CA2122224A1 - Method and apparatus for soil remediation with superheated steam thermal desorption and recycle - Google Patents
Method and apparatus for soil remediation with superheated steam thermal desorption and recycleInfo
- Publication number
- CA2122224A1 CA2122224A1 CA002122224A CA2122224A CA2122224A1 CA 2122224 A1 CA2122224 A1 CA 2122224A1 CA 002122224 A CA002122224 A CA 002122224A CA 2122224 A CA2122224 A CA 2122224A CA 2122224 A1 CA2122224 A1 CA 2122224A1
- Authority
- CA
- Canada
- Prior art keywords
- exit
- gas
- treatment
- gas stream
- superheated steam
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/06—Reclamation of contaminated soil thermally
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09B—DISPOSAL OF SOLID WASTE
- B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
- B09B3/40—Destroying solid waste or transforming solid waste into something useful or harmless involving thermal treatment, e.g. evaporation
- B09B3/45—Steam treatment, e.g. supercritical water gasification or oxidation
Abstract
ABSTRACT OF THE DISCLOSURE
Method and apparatus for soil remediation with superheated steam thermal desorption and recycle.
A method and apparatus are provided for remediating contaminated soil having volatilizable organic pollutants in a heated treatment zone, preferably a rotary drum, in gas/solids contact with superheated steam. Treatment gases from the treatment zone are repressurized and reheated for reuse in the treatment zone. Superheated steam is maintained in a closed loop and is maintained at superheated conditions. Vaporized organic pollutants and superheated steam are removed from the closed loop of superheated steam for cooling and condensation to condense water and condense liquid volatilizable organic pollutants and uncondensed organic pollutant vapors.
Method and apparatus for soil remediation with superheated steam thermal desorption and recycle.
A method and apparatus are provided for remediating contaminated soil having volatilizable organic pollutants in a heated treatment zone, preferably a rotary drum, in gas/solids contact with superheated steam. Treatment gases from the treatment zone are repressurized and reheated for reuse in the treatment zone. Superheated steam is maintained in a closed loop and is maintained at superheated conditions. Vaporized organic pollutants and superheated steam are removed from the closed loop of superheated steam for cooling and condensation to condense water and condense liquid volatilizable organic pollutants and uncondensed organic pollutant vapors.
Description
2~2222~
PHA 21.810 1 12.10.1993 MET~OD AND APPARATUS FOR SOIL REMEDL~TION WITH SUPER~IEA'IED
STEAM THERMAL DESORPTION AND RECYCLE
Field of ~he Invention This invention relates to a method and apparatus ~or the remediation of contaminated soil by removing volatilizable organic pollutants which contaminate the soil to permit reuse of the soil and re overy ot volatilizable organic pollutants. More 5 par~cularly, the invention relates to a me~od and apparatus for recovering volatiLizable organie pollutants from contaminated soil by means of tre~tment with superheated s~eam maintained in a closed, circulating l~p.
BACKGR(:)IJMl~) OP THE INV~NTION
Soil remediation is well established as a procedure for complying with environmental clean-up requirements. Continued accumulations of volatilizable organic pollutants in the soil around chemical plants, petroleum plants, manufacturing pl~nts, gasoline filling stations, and agricultural chemical deposits (eg., pesticides, herbicides, fungicides, etc.) may be considered as a thr~t to surface water and ground water or a 15 threat to one or more other circumstance which is regulated by environmental laws and rules. Where contaminated soil is objectionable, there are numerous regulations to be considered.
The present invention is concerned with contaminated soil remedia~on where the volatili~able organic content of the soil e~c~eds the allowable regulatory 20 maxima but i3 p~ferably less than about ~ive weight percent of the soil and more particularly less than ~out two weight percent of the soil. E~amples of suitable soils include solids such as topsoil, river sediments, bedrock, alluvium, and particulate fill materials such as cinders, gravel and slag.
Several procedures for remediating cont~uninated soils are shown in U.S.
25 Patents 4,738,2n6; 4,974,52~; 5,072,674; S,103,578; 5,121,699; 5,142,998; 5,152,233;
5,187,131; ( heat supply for devolatilization by heated flight conveyor3 4,738,206;
5,072,674; 5,142,998; (indirect heating means, e.g. ~eetric heaters or heat exchange 212222~
.........
PHA 21.810 2 12.10.1993 fluids) 5,103,578; and (fuel oil or fuel gas combustion) 4,974,528; 5,121,699;
5, 1~2,233.
None of the prior art processes employ superheated steam in gas/solids contact with the contaminated soil in a syst rn wherein superheated stearn and the 5 volatiliæd and/or volatilizable organic pollutants recirculate with the system at temperatures which m~intain the superheated system in a superheated state, i.e.,wherein the steam is maintained above its saturation temperature at all tirnes.
~U~ARX C)F THE INVENTTQ~
According to the present invention, contaminated earth solids are introduced into an enclosed treatment zone, preferably an appropriately sealed rota~ng drum, which is maintained at an elevat~d temperature which promotes vola~lization of any volatilizable org~nic pollutants from the contalminated soil. Approprizte soil temperatures are 250F to 1000F and preferably 300F to 700~ depending on the 15 par~cular pollutants present in the soil and the particular contaminat~d soil. The contaminated soil is introduced into the treatment zone at ambient temperature and is heated within the treatment zone to a pre-selected discharge temperatufe after which a remediated soil having a residual organic pollutant content acceptable within applicable laws and regulations is obtained.
The soil preferably i~ heated to a pre-selected temperature an~ maintained at the pre-selected temperature within the rotary drum for a residence time sufficien~ to achieve the desired pollutant volatilization. Extended residence time with extended retention of the contaminated soil in the treatment zone may achieve the desiredpollutant volatilization at a lower soil temperature. The pre-selected temperature and 25 pre-selected residence time will be determined by the specific con~aminated soil, the nature of the organic pollutants and the ma~imum residual contamination under applicable regula~ns or other considera~ons.
A stream of ~eatment gas passes through the t~eatment ~one in gas/solids contact with the contan~inated soil. Tlle ~eatment gas consists of superheated st~n and 30 volatilized organic pollutants which have been rernoved from contaminated soils in the prior operation of the process. l'he treatment gas is withdrawn from the treatment zone at an esdt pressure and at an e~it temperature which is su~cient to maintain the steam in a superheated state. A major portion of the treatment gas i5 pressuriæd, reheated 2:12222~
-~ PHA 21.810 3 12.10.1993 and returned to the ~eatment zone as the treatment gas. A portion of the exit gas, consisting of superheated steam and volatili~ed, volatilizable organic pollutants, is separated from the recirculating treatment gas and is cooled to condense the superheated stearn and most of the vaporiæd organic pollutants. Any non-condensed organic S pollutants are recovered as a gas s~eam; the condensed organic pollutants are recovered as a liquid strearn; the condensed superheated steam is recovered as water.
The hot decontaminated soil i5 recovered from the treatment zone and is recycled to the environment. In a preferred mode~ the decontaminated soil is restored to the location from whence it originated, i.e., the plot of land requiring remediation.
10 Alternatively the decontaminated soil may be dispersed in other areas, for ex~nple, the decontaminated soil may qualify as a cover for municipal landfills. The water recovered from the process may be IlSed to cool and moisten the decontarninated soil prior to reuse of the decontaminated soil.
In one embodiment, the exit gas from ~he treatment zone may be passed 15 through a gas/solids separator such as a cyclone, a baghouse, an impingement hlock-out box, etc. to remove gas-borne particles which may be objectionable in the subsequent gas treatment. Preferably such a gas/solids separator will be heated to a temperature above the temperature of the gas stream passing through the gas/solids separator to preclude deposition of volatile organic materials ~rom the gas stream. Solids recovered 20 from the gas/solids separator can be returned to the lrea~ment zone or Gan be separately disposed of in any suitable or desirable procedure, e.g., appropria~e landfilling.
The present invention and apparatus permit relatively easy separation of the recovered volatiliæd organic pollutant~ from the condensed superheated steam.
Depending upon the nature of the contaminating organic pDllutant~, appropriate 25 recovery for recycle may be feasible as in the case of, for example, recovered benzene, toluene, xylene; aliphatic and cyclic petroleum products, etc.
B~IEF D~ RE"I IQN OF I~ DRAWIN~
The sole figure, Figure 1, i5 a schematic illustra~ion of the apparatus 30 assembled according to the invention for carrying out the novel methods.
DETAI~EE2-DE~cRlE~o~L OF 'rHE3 PR~F~ ~0I)l~
2~2222~
PHA 21.810 4 12.10.1993 Examples of contaminated soil that may be used for the purposes of this invention include earth materials (e.g., topsoil, river sediments, bedrock, alluvium) or particulate fill material (e.g., cinders, gravel, slag) and others which containobjectionable quantities of volatilizable organic pollutants, i.e., quantities exceeding the 5 limits imposed by environmental laws and regulations. Preferably, organic pollutant content should not exceed about 5 % by weight of the earth solids and most preferably should not exceed about 2% by weight of the earth solids in order to benefit from the present inventiGn although soils with higher pollutant content may be satisfactorily treated.
Volatilizable orgar~ic materials are those organic materials which can enter into the vapor phase at the temperatures anticipated in the treatment wne. The volatilizable organic pollutan~s thus include:
normally volatile mate~ials which may be dissolved or absorbed in the soil (e.g., acetone, paint thinners, etc.);
norrnally liquid organic materials which may be absorbed or otherwise contained in the soil (e.g., benzene, toluene, xylene, gasoline, fuel oil, lubricating oil, etc.);
materia1s which may be solid or semi-solid at arnbient temperature but which can be volatilized at elevated temperatures (e.g., heavy oil, grease, light asphalt, 20 tars, etc.);
agricultural chemicals such as pesticides, herbicides, rodenticides, fertilizers, etc.; and halogenated organic materials such as halogenated aromatics (PCBs~ and halogenated alipha~cs, etc.
For convenience, the volatilizable organic materials are some~imes referred to herein as "pollutants" to indicate that they are not naturally occur~ing ingredients of the soil.
Superheate~ st~m is steam which is maintained at a temperature ab~ve its saturation temperature wi~ liquid water. Superheated steam can exist at sub-30 atmospheric pressure, at atmosphelic pressure and at super-atmospheric pressures.
Superheated steam at all times contains the la~ent heat of vapolization and at least some sensible heat or enthalpy.
Re~erring to PIGURE 1, the principal elements of the apparatus are:
~2222~
PHA 21.810 5 12.10.1993 10 a supply site for contasninated earth solids;
11 a rotary drum which is a treatment zone for gas/solids ~ntac~;
12 pump or blower means for increasing the pressure of recirculating treatment gas;
13 a st~m supe~heater for increasing the temperature of recirculating treatment gas;
14 a condenser for recondensing a portion of the recirculating treatmellt gas;
17 a liquid collector shown as a decanter for separate recovery of non~ondensed organic gase~
condensed organic liquids and water; and 18 a collection site for decontaminated soil.
15 he Treatment ~Qne.
The treatment zone preferably is a rotary drum. Typically rotary dNms have circumferential supporting bands 20 ~two are shown~ which support the drum in a position with the central lengthwise axis tilted from the horizontal to facilitate movement of solids through the rotary drum. Another band 19 may be provided with2() perim~ter teeth 21 which engage a toothed gear driving gear 22 dri~en by an appropriate drive means 23, usllally a motor and spe~d reducer, to turn the rot~ drum about its central leng~hwise axis. Th~ other bands 20 are supported Oll trunnion rolls 24 and thrllSt rolls (not ~own). The rotary drum 11 rotates in accordallce wi~ the manufacturer's specification for the desired solids t}uoughput. The ~o~ary drum 25 customarily i9 equipE;ed with agita~ng flight~ extend~d ~ially inwardly from the inner cylindrical wall of ~he drum. The flights may have angled sur~aces to facilitate lif~ag ~ld showering of earth solids as they move ~rough the rotary drum ~om ~ft to right in PIGURE 1. l~e rotary drum 11 is a sealed drum which has appr~priate fe~ing m~s .
for receiving con~ated soil from the supply site 10 through a conduit 25. An auger 30 feeder is a preferred fe~ding means for introducing contan~inated soil into ~e rotal~
drum 11. Double-valved lock hoppers or star valves may be used. Appropriate means may be provided for metering the flow of cDntaminated soil. The rot~ry dmm 11 also has sealed withdrawal me~ns for removing deeon~ninat~d soil from the rotary drum 11 :
;
, ,.;
PHA 21.810 6 12.10.1993 through a conduit 26 to the collection site 18 for decontaminated soil. The withdrawal means preferably is a double-valved lock-hopper or star valve.
The rotary drum 11 can be any of several that may be obtained from several manufacturers. One embodiment is a steel cylinder having thermal insulation S around ~he outer cylindrical wall and having inwardly directed radial flights to agitate and advance the soil moving through the drum.
In ~he preferred embodiment of the invention, all of the heat requirements for the process are supplied by ths sensible heat of the recirculating superheated steam.
In o~her embodiments, the superheated steam may supply a portion of the heat 10 requirements for the process, witih another por~on of the heat requirements being supplied by means of a heated rotary drum 11 which ma~ be a heated concentric rotary drum having two concentric steel cylinders in which heating gases are bumed in the annulus between the two eylinders and the contaminated soil is delivered into the central cylinder. Alternatively, the rotary drum may be heated elecbically, etc..
The rotary dmms as des~ribed are readily aYailable. Ihe length and diameter of a rotary dmm determines the internal volume and hence the throughput of the drum. A typical drum might be S feet in diameter and 30 feet long ~or processing 1 to S tons per hour of contaminated soil. The dmm may range from about 3 feet to about 8 feet in diameter and have a length ~rom 10 to 40 feet. In general, about 10%
20 of the volume of a rotary drum comprises the solid materials undergoing treatment within the drum.
The rotary drum usually will exhibit a temperature profile with the highest temperature adjacent to the solids discharge end of the drum and the lowest temperature adjacent to the solids inlet of the drum.
Thç Treatment Gas The treatment gas consists of superheated steam and volatilized organic pollutants which have been removed from previously treated contaminated soil in the process. The treatment gas passes through a clos~d loop consisting of:
the rotary drum 11; a conduit means 27 which leads from the rotary drum 11 to the blower means 12; a conduit means 28 which leads to the steam superheater 13; and a conduit means 29 which leads back to the rotary drunn 11 .
" ~122~2~
PHA 21.810 7 12.10.1993 Trea~ment gas enters into the rotary drum 11 through the conduit means 29 at an elevated temperature, i.e., elevated above the operating temperature within the rotary drum 11. The hot treatment gas provides the heat of vaporization ~or the volatilizable organic pollutants in the contaminated soil. The treatment gas also provides at least 5 some of the heat necessary for the heat of vaporization of the moisture which is inherent in the contaminated soil. Thus ~he treatment gas generates additional superheated steam from the soil moisture. The treatment gas, the newly created superheated steam and the volatili~ed, volatili~able organic pollu~nts exit from the rotary drum 11 at an exit temperature and an exit pressure and is delivered through conduit means 27 to the pump 10 (blower) means 12 where the pressure of the gases is increased above the exit pressure.
The exit pressure can be sub-atmospheric~ atmospheric or super-atmospheric. Typically the exit pressure is from 0 to 5 psig. The exit temperature is sufficient to maintain the superheated steam in a superheated state at the exit pressure~ and typically is 220~ to 50~F. The blower means 12 increases the treatment gas pressure sufficiently to drive 15 the treatment gas through the superhea~er 13 and the rotary drum 11. Typically the blower/pump means 12 raises the treatment gas pressure to 2 to 15 psig, i.e., several psig above the exit pressure. Relatively low pressures are preferred to avoid any psessure-vessel piping requiremen~, i.e., the need to design, build, test and maintain the system in accordance with indus~y codes ~or pressure-vessels. Centrifugal 20 compressors or positive displacemen~ blowers are preferred as th~ pump means.Optionally, the process may be operated under subatmospheric pressure, e.g., at 14.7 to 13.8 psia. Subatmospheric pressure operation reduces any tendency of the system to leak organic pollutants into the environment. If such subatmospheric operation is employed, then the inner portion of the exit gas stream will pass the pump means 12 and conduits 28, 31, 32 to the condenser 14; the conduit 30 wiLI be closed. During subatmospheric operation, the system must remain relatively free of leaks which n~ight allow air to enter the recirculating superheated 9team 15~op.
e Stearn ~uperheater The steam superheater 13 is a heat transfer device such as an electrical core h~ater or a gas or fuel oil fired heater. Electrical heating i5 preferred for precise control of the process.
21 2222~
PHA 21.810 8 12.10.1993 The pressuriæd treatment gases are delivered from the pump means 12 through the conduit 28 to the steam superheater where the eemperature of the treatment gases is increased above the exit temperature. Typically the temperature of the treatment gases entenng the conduit 29 from the steam superheater 13 will be 500F to 5 1100F. A product stream is withdrawn from the treatment gas loop through conduits 30 or 31.
It should be observed from the preferred embodiment illustrated in FIGURE 1 that the volume of the rot~ drum 11 greatly e~ceeds ~he total volume ofthe conduit means 27, 28, 29 and the pump means 1~ and superheater 13. Thus in any 10 instant, ~he overwhelming majority of the ~eatment gas is in the rotary drum 11 and a minor portion of the recircula~g treatment gas is in the remainder of the closed loop consisting of the conduit means 27, 28, 29, the pump means 12, and the superheater 13.
The Org~ic Pollutant ~Qllç~l Qn Sy~em A portion of the recirculating treatment gas from the conduit 27 or from the conduit 28 is recovered through conduits 30, 31 respeetively and delivered through a conduit 3~ to the condenser 14. The material passing into the condenser 14 corresponds to the moisture and organic pollutant content of the contaminated soil. The condenser is cooled by rneans of coolant fluids which are delivered through a conduit 33, and20 withdrawn through a conduit 35.
If adequate cooling water is available, cool water will enter conduit 33 and heated water will be withdrawn ~hrough conduit 35. If cooling water is not available, a chiller (not shown) may provide chilled coolant fluid through conduit 33.
Heated coolant fluid is withdrawn through conduit 35 and recovered for reuse as 25 coolant.
Substantially all of the superheater steam is cool~d and condensed in the condenser 14 along with substantially all of the condensible vola~iliæd organic pollu~ants. The liquid products from the condenser 14 are delivered through a conduit 36 to the collector 17 which is shown as a decanter. Uncondensed organic pollutants 30 are removed from the decanter 17 through conduit means 40. Light organic pollutants are removed from ~e decanter 17 through conduit m~ns 39. Water is removed from the decanter 17 through conduit means 38. Heavy ~ars, asphalts, carry-over particles, e~c., are withdrawn from the decanter 17 through conduit means 37.
~ ; .. . ~ . : .
2122~24 PHA 21.810 9 12.10.1993 The mass flow rate of treatment gas through the condult means 29 is from 2.5 to 1~ times (preferably 5 to 30 times) the mass flow rate of treatment gas recovered through the conduits 30 or 31. The need for substantial volumes of flow arises from the use of the superheated steam in the treatment gas as a source of heat for 5 vaporization of volatilizable organic pollutants and for vapori~ing moisture ~om the contaminatecl soil within the rotary drum 11. In some embodiments it may be desirable to provide extrinsic heat to the exit gas stream in the conduit means 27 as shown schematically by the heater element 41. The supplemental heat is primarily intended to preclude condensation of volatilized organic pollutants within the conduit 27 and the 10 pump means 12 and the conduits 28, 30, 31 and 32.
Solids Removal It mlay be desirable to remove gas-borne solid panicles ~rom the recircula~ng ~eatment gas in the condui~ 27. An appropriate solidslgas separator 42 15 may be provided along with condui~ means 43 for receiving treatment gas f~om the conduit 27 and conduit means 44 to return to the conduit 27 treatment gas from which solids have been ~moved. The p~ticles from the conduit 45 may be returned to therotary drum 11 or may be otherwise managed. It is desirable that the solids/gas separator 42 be maintained at a temperature above the condensation temperature of the 20 volatili~ed organic pollutants. Appropriate heating means indicated schematically by the numeral 46, are provided to maintain the solids/gas separator 42 at an appropriate eïevated temperature.
~XAMPL~
To illustrate the cost effectiveness of the present inYention, four examples 25 are provided for comparison in which the energy requirements for dec~ntamination of soils by treatment with suyerheat~d steam is calculated for a process according to the invention, in which superheated steam is recycled~ and according to a process in which superheated steam is employed without recycling. In all instanees, the calculations are based on the following: (a) the contaminated soil contains 1% by weight of 30 volatilizable organic pollutants and 20% by weigh~ moisture at arnbient temperature (60F); (b) the decontaminated soil contains less than 0.5 wt percent water and less than 0.001 wt percent of residual organic pollutant, i.e., more th~n 99.9 wt percent of the 2:~222~
"
PHA 21.810 10 12.10.1993 volatilizable organic pollutants were removed; (c) ~he rotary drum is S feet in diameter, weight 7000 lbs. and the soil is heated to 700F.
Four e~amples will highlight the benefits resulting from the practice of the present invention.
S In each example, calculations are made based on the system illustrated in FIGURE 1 with certain changes to be described.
EXAMPLES I, II and m illustrate the cost effectiveness of the invention.
EXAMPLE IV is a comparative example and illustrates the cos~ of using superheated steam in a process without reeycle or recircula~on of superheated steam.
In EXAMPLE I, calculations were based on the system illustrated in FIGUl~ 1 operated on 1 ton per hour of contaminated soil with superheated steam being employed to supply the en~re heat requirements of the system.
In EXAMPLE Il, calculations were based on the sy~tem illustrat~d in FIGURE 1 operated on 1 ton per hour of contaminated soil with indirect heat supplied 15 to the rotary drum and superheated st~n employed to heat the soil and to maintain the contan~inated soil at the desired temperature, 700F, and to offset heat losses from the system to the environment.
In EXAMPLE m, the calculations were based on a system similar to that described in EXAMPLE II except that the throughput is 2 tons per hour.
In comparative EXAMPLli IV, the calculations were based on a system wherein the rotary drum 11 and the recovery system illustrated in fig. 1 were employed, without pump 12, i.e. a system which has no recir~ulating superheated steam and in which superheat~ steasn provides all of the heat energy, is employed on a once-through basis, and the throughput i9 1 ton per hour.
TABLE I sets forth the parameters of each EXAMPLE and the heat requirements and steam re~uLrements.
212222~
....,~
;~ PHA 21.810 11 12.10.1993 TABLE I
ENER~;Y REQUIREMENTS FOR SOIL DECONTAMINATION
s E~MPI~ES
III ~ III I~l FEE~ SO~ omoaracive) Wa~er, w~ 20 20 20 ~0 Orga~ics, wt ~ ~ 1 1 1 1 Temperature (F) 60 50 60 60 FLOW RATE lbs/h~20002000 4000 2000 - Wet 3asi~
~ROD~CT ~OI~
Water wt ~ ~ c0.5~0.5 ~0.5 ~0.5 Organics, wt ~0.001~0.001~0.001~0.001 Exi~ Tempera~ure (F)700 700 700 700 - Dry ~3asis L~L~ 5~-E~ iency)- M9~.U~
Heat Soil to 700 (F)520 520 1040 520 Heat, Vaporize Moisture 665 665 1330 665 ~eat, Vaporize Organics 15 15 30 15 Heat 1~099 300 300 300 300 TSI~Ll5~T ~EQUI~ NTS1500 1500 2700 1500 STEAM REQUIR~M~N~
S/H Steam lbs/hr39252250 2250 3925 S/H Steam to Compre~sor : :
220 ~F) - ACFM1770 1015 1015 N/A :~
S/H Steam t~ Superhea~er 300 (F) -- ACFM1310 750 750 N/A
S/H Steam to Rotary Drlm :
1000 (F) -- ACFM2~20 1600 1600 3925 .~
INDI~ECT ~ aI~I~E O 635 1~35 o ~ ii''".,:`"'''`'.'''''.''.''.''',,``.',`"','`''``''''.' "':`' 212222~
PHA 21.810 12 12.10.1993 From TABLE I it will be observed that the steam requîrement ~or EXAMPLE I is the same as that ~or EX~IPLE IV. In both EXAMPLES I and :lV all of the heat requirement is supplied by superheated steam. Similarly, the superheated S stearn requirement for EXAMPLE II is the same as tha~ of E~AMPLE IlI, despite the fact that EXAMPLE m treats twice the quantity of contaminated soil of ~XAMPLE II.
TA~LE II sets forth the coolillg requirements ~or volatilized organic pollutants and the carrying steam and also a summary of the overall energy requirements.
T~LE II
FNERGY REQUIREMENTS FOR OR&ANIC RECOVERY
I II III LV
(compara~lve) GAS EXIT ST~EAM ~lhalh~) Steam 3925 2250 2250392S
Soil Moisture 390 390 7ao 390 20 Organlcs 20 20 40 20 GAS STREAM TO C^~ E~ s/~r~
Vaporized Mois~-e~390 ~390 ~790~3~0 Organics 20 20 40 20 Recirculating S/H Steam 0 0 0 3925 25 ~QIAh L3S/H~ TQ CONDENSE~ ~410~410 ~020 ~4335 C~ING REQUI~EMENTS
co 60 (F), 75~ Sf~iciency 617 617 1234 5000 M9TUIhr E~ERGY R~Q~L~E~NTS (M~TU/con) 30 S/H Ste~n ^ 1500 365 4335300 Coollng 620 620 6205120 Indirect Heat T3 Rotary Drum 0635 917 o TOTAh ENERGY REQUI~EMENTS 212021201970 10420 M~TU/Ton Ill TABL13 II the cooling requiremen~s per ton of soil processed are identical for EXA~fPLE I, lEX~I:,E II and EXAMPLlEi m.
The cooling requ~rements for EXAMPLE IV are disproportionate because the superheated steam i5 employed on a once-through b~sis.
- 2~2222~
PHA 21.810 13 12.10.1993 Summary of Examples I to IV
From TABLE II it will be observed that substantial savings in the total energy requirements per ton for the described soil decontamination are obtained S according to the invention (compare Examples I, II and III with example IV). It will also be observed that the total energy requirements per ton are least for EXAMPL~i m since the sarne rotary drum is processing twice the throughput with the same heat loss.
The energy requirements for the me~hod illustrated by EXAMPLE IV (without recirculation or recycle of superheated steam) are excessive.
Some of the energy supplied for EXAMPLES II and III is in the form of buming fuel gas or fuel oil which indirectly heat the ro~ary drum and provides therrnal energy at xelatively low cos~ and a~ a significan~y lower cost than electrically heated superheated steam. It is thus possible to reduce the amount of superheated steamrequired to be in the recirculating loop (compare EXAMPLES II, m versus 15 E~AMPLES I, IV) and to thus reduce the siæ of th~ superheater 13 and pump 12 by the use of supplemental heating means.
Ihe process of the invention has been used on a bench scale and found to be effective for decontarnination of contarninated soil from a varie~ of contaminated sites including a former wood treating facility that used creosote and copper, chromium 20 and arsenic forrnulations and a site contaminated with pesticides.
The method and system of the invention have been found to be quite flexible with a wide variety of operating temperatures and residence times depending on the material being treated, are applicable to the cleanup of a variety of contaminants, and are a viable alternative for on-site treatment of so;ls from various contaminated 25 sites.
The method and system may be used in conjunction with the remediation of contaminated solid materials as described and claimed in copending applications U.S.
Se~ial No. en~ed ~fETHOD FOR TREATMENT OF CONT~ATED
MATERIALS WlTH SUP~IEATED STEAM[ I~IEUMAL DESO3~PTION AND
30 l~CYCLE Docket No. 1604-0003-2) and ll.S. Serial No. ~, entitled METHOD
FOR TREAT~NT O~ D~POUNDED SLUDGES, SOILS AND OTH~R
CONTA~NATED SOLID ~iATERlALS (Docket No. 1604-0003-1), both filed 212222~
~: PHA 21.~10 14 12.10.1993 concurrently and commonly assigned herewith, the disclosures of which are incorporated herein by thiis re~erence.
PHA 21.810 1 12.10.1993 MET~OD AND APPARATUS FOR SOIL REMEDL~TION WITH SUPER~IEA'IED
STEAM THERMAL DESORPTION AND RECYCLE
Field of ~he Invention This invention relates to a method and apparatus ~or the remediation of contaminated soil by removing volatilizable organic pollutants which contaminate the soil to permit reuse of the soil and re overy ot volatilizable organic pollutants. More 5 par~cularly, the invention relates to a me~od and apparatus for recovering volatiLizable organie pollutants from contaminated soil by means of tre~tment with superheated s~eam maintained in a closed, circulating l~p.
BACKGR(:)IJMl~) OP THE INV~NTION
Soil remediation is well established as a procedure for complying with environmental clean-up requirements. Continued accumulations of volatilizable organic pollutants in the soil around chemical plants, petroleum plants, manufacturing pl~nts, gasoline filling stations, and agricultural chemical deposits (eg., pesticides, herbicides, fungicides, etc.) may be considered as a thr~t to surface water and ground water or a 15 threat to one or more other circumstance which is regulated by environmental laws and rules. Where contaminated soil is objectionable, there are numerous regulations to be considered.
The present invention is concerned with contaminated soil remedia~on where the volatili~able organic content of the soil e~c~eds the allowable regulatory 20 maxima but i3 p~ferably less than about ~ive weight percent of the soil and more particularly less than ~out two weight percent of the soil. E~amples of suitable soils include solids such as topsoil, river sediments, bedrock, alluvium, and particulate fill materials such as cinders, gravel and slag.
Several procedures for remediating cont~uninated soils are shown in U.S.
25 Patents 4,738,2n6; 4,974,52~; 5,072,674; S,103,578; 5,121,699; 5,142,998; 5,152,233;
5,187,131; ( heat supply for devolatilization by heated flight conveyor3 4,738,206;
5,072,674; 5,142,998; (indirect heating means, e.g. ~eetric heaters or heat exchange 212222~
.........
PHA 21.810 2 12.10.1993 fluids) 5,103,578; and (fuel oil or fuel gas combustion) 4,974,528; 5,121,699;
5, 1~2,233.
None of the prior art processes employ superheated steam in gas/solids contact with the contaminated soil in a syst rn wherein superheated stearn and the 5 volatiliæd and/or volatilizable organic pollutants recirculate with the system at temperatures which m~intain the superheated system in a superheated state, i.e.,wherein the steam is maintained above its saturation temperature at all tirnes.
~U~ARX C)F THE INVENTTQ~
According to the present invention, contaminated earth solids are introduced into an enclosed treatment zone, preferably an appropriately sealed rota~ng drum, which is maintained at an elevat~d temperature which promotes vola~lization of any volatilizable org~nic pollutants from the contalminated soil. Approprizte soil temperatures are 250F to 1000F and preferably 300F to 700~ depending on the 15 par~cular pollutants present in the soil and the particular contaminat~d soil. The contaminated soil is introduced into the treatment zone at ambient temperature and is heated within the treatment zone to a pre-selected discharge temperatufe after which a remediated soil having a residual organic pollutant content acceptable within applicable laws and regulations is obtained.
The soil preferably i~ heated to a pre-selected temperature an~ maintained at the pre-selected temperature within the rotary drum for a residence time sufficien~ to achieve the desired pollutant volatilization. Extended residence time with extended retention of the contaminated soil in the treatment zone may achieve the desiredpollutant volatilization at a lower soil temperature. The pre-selected temperature and 25 pre-selected residence time will be determined by the specific con~aminated soil, the nature of the organic pollutants and the ma~imum residual contamination under applicable regula~ns or other considera~ons.
A stream of ~eatment gas passes through the t~eatment ~one in gas/solids contact with the contan~inated soil. Tlle ~eatment gas consists of superheated st~n and 30 volatilized organic pollutants which have been rernoved from contaminated soils in the prior operation of the process. l'he treatment gas is withdrawn from the treatment zone at an esdt pressure and at an e~it temperature which is su~cient to maintain the steam in a superheated state. A major portion of the treatment gas i5 pressuriæd, reheated 2:12222~
-~ PHA 21.810 3 12.10.1993 and returned to the ~eatment zone as the treatment gas. A portion of the exit gas, consisting of superheated steam and volatili~ed, volatilizable organic pollutants, is separated from the recirculating treatment gas and is cooled to condense the superheated stearn and most of the vaporiæd organic pollutants. Any non-condensed organic S pollutants are recovered as a gas s~eam; the condensed organic pollutants are recovered as a liquid strearn; the condensed superheated steam is recovered as water.
The hot decontaminated soil i5 recovered from the treatment zone and is recycled to the environment. In a preferred mode~ the decontaminated soil is restored to the location from whence it originated, i.e., the plot of land requiring remediation.
10 Alternatively the decontaminated soil may be dispersed in other areas, for ex~nple, the decontaminated soil may qualify as a cover for municipal landfills. The water recovered from the process may be IlSed to cool and moisten the decontarninated soil prior to reuse of the decontaminated soil.
In one embodiment, the exit gas from ~he treatment zone may be passed 15 through a gas/solids separator such as a cyclone, a baghouse, an impingement hlock-out box, etc. to remove gas-borne particles which may be objectionable in the subsequent gas treatment. Preferably such a gas/solids separator will be heated to a temperature above the temperature of the gas stream passing through the gas/solids separator to preclude deposition of volatile organic materials ~rom the gas stream. Solids recovered 20 from the gas/solids separator can be returned to the lrea~ment zone or Gan be separately disposed of in any suitable or desirable procedure, e.g., appropria~e landfilling.
The present invention and apparatus permit relatively easy separation of the recovered volatiliæd organic pollutant~ from the condensed superheated steam.
Depending upon the nature of the contaminating organic pDllutant~, appropriate 25 recovery for recycle may be feasible as in the case of, for example, recovered benzene, toluene, xylene; aliphatic and cyclic petroleum products, etc.
B~IEF D~ RE"I IQN OF I~ DRAWIN~
The sole figure, Figure 1, i5 a schematic illustra~ion of the apparatus 30 assembled according to the invention for carrying out the novel methods.
DETAI~EE2-DE~cRlE~o~L OF 'rHE3 PR~F~ ~0I)l~
2~2222~
PHA 21.810 4 12.10.1993 Examples of contaminated soil that may be used for the purposes of this invention include earth materials (e.g., topsoil, river sediments, bedrock, alluvium) or particulate fill material (e.g., cinders, gravel, slag) and others which containobjectionable quantities of volatilizable organic pollutants, i.e., quantities exceeding the 5 limits imposed by environmental laws and regulations. Preferably, organic pollutant content should not exceed about 5 % by weight of the earth solids and most preferably should not exceed about 2% by weight of the earth solids in order to benefit from the present inventiGn although soils with higher pollutant content may be satisfactorily treated.
Volatilizable orgar~ic materials are those organic materials which can enter into the vapor phase at the temperatures anticipated in the treatment wne. The volatilizable organic pollutan~s thus include:
normally volatile mate~ials which may be dissolved or absorbed in the soil (e.g., acetone, paint thinners, etc.);
norrnally liquid organic materials which may be absorbed or otherwise contained in the soil (e.g., benzene, toluene, xylene, gasoline, fuel oil, lubricating oil, etc.);
materia1s which may be solid or semi-solid at arnbient temperature but which can be volatilized at elevated temperatures (e.g., heavy oil, grease, light asphalt, 20 tars, etc.);
agricultural chemicals such as pesticides, herbicides, rodenticides, fertilizers, etc.; and halogenated organic materials such as halogenated aromatics (PCBs~ and halogenated alipha~cs, etc.
For convenience, the volatilizable organic materials are some~imes referred to herein as "pollutants" to indicate that they are not naturally occur~ing ingredients of the soil.
Superheate~ st~m is steam which is maintained at a temperature ab~ve its saturation temperature wi~ liquid water. Superheated steam can exist at sub-30 atmospheric pressure, at atmosphelic pressure and at super-atmospheric pressures.
Superheated steam at all times contains the la~ent heat of vapolization and at least some sensible heat or enthalpy.
Re~erring to PIGURE 1, the principal elements of the apparatus are:
~2222~
PHA 21.810 5 12.10.1993 10 a supply site for contasninated earth solids;
11 a rotary drum which is a treatment zone for gas/solids ~ntac~;
12 pump or blower means for increasing the pressure of recirculating treatment gas;
13 a st~m supe~heater for increasing the temperature of recirculating treatment gas;
14 a condenser for recondensing a portion of the recirculating treatmellt gas;
17 a liquid collector shown as a decanter for separate recovery of non~ondensed organic gase~
condensed organic liquids and water; and 18 a collection site for decontaminated soil.
15 he Treatment ~Qne.
The treatment zone preferably is a rotary drum. Typically rotary dNms have circumferential supporting bands 20 ~two are shown~ which support the drum in a position with the central lengthwise axis tilted from the horizontal to facilitate movement of solids through the rotary drum. Another band 19 may be provided with2() perim~ter teeth 21 which engage a toothed gear driving gear 22 dri~en by an appropriate drive means 23, usllally a motor and spe~d reducer, to turn the rot~ drum about its central leng~hwise axis. Th~ other bands 20 are supported Oll trunnion rolls 24 and thrllSt rolls (not ~own). The rotary drum 11 rotates in accordallce wi~ the manufacturer's specification for the desired solids t}uoughput. The ~o~ary drum 25 customarily i9 equipE;ed with agita~ng flight~ extend~d ~ially inwardly from the inner cylindrical wall of ~he drum. The flights may have angled sur~aces to facilitate lif~ag ~ld showering of earth solids as they move ~rough the rotary drum ~om ~ft to right in PIGURE 1. l~e rotary drum 11 is a sealed drum which has appr~priate fe~ing m~s .
for receiving con~ated soil from the supply site 10 through a conduit 25. An auger 30 feeder is a preferred fe~ding means for introducing contan~inated soil into ~e rotal~
drum 11. Double-valved lock hoppers or star valves may be used. Appropriate means may be provided for metering the flow of cDntaminated soil. The rot~ry dmm 11 also has sealed withdrawal me~ns for removing deeon~ninat~d soil from the rotary drum 11 :
;
, ,.;
PHA 21.810 6 12.10.1993 through a conduit 26 to the collection site 18 for decontaminated soil. The withdrawal means preferably is a double-valved lock-hopper or star valve.
The rotary drum 11 can be any of several that may be obtained from several manufacturers. One embodiment is a steel cylinder having thermal insulation S around ~he outer cylindrical wall and having inwardly directed radial flights to agitate and advance the soil moving through the drum.
In ~he preferred embodiment of the invention, all of the heat requirements for the process are supplied by ths sensible heat of the recirculating superheated steam.
In o~her embodiments, the superheated steam may supply a portion of the heat 10 requirements for the process, witih another por~on of the heat requirements being supplied by means of a heated rotary drum 11 which ma~ be a heated concentric rotary drum having two concentric steel cylinders in which heating gases are bumed in the annulus between the two eylinders and the contaminated soil is delivered into the central cylinder. Alternatively, the rotary drum may be heated elecbically, etc..
The rotary dmms as des~ribed are readily aYailable. Ihe length and diameter of a rotary dmm determines the internal volume and hence the throughput of the drum. A typical drum might be S feet in diameter and 30 feet long ~or processing 1 to S tons per hour of contaminated soil. The dmm may range from about 3 feet to about 8 feet in diameter and have a length ~rom 10 to 40 feet. In general, about 10%
20 of the volume of a rotary drum comprises the solid materials undergoing treatment within the drum.
The rotary drum usually will exhibit a temperature profile with the highest temperature adjacent to the solids discharge end of the drum and the lowest temperature adjacent to the solids inlet of the drum.
Thç Treatment Gas The treatment gas consists of superheated steam and volatilized organic pollutants which have been removed from previously treated contaminated soil in the process. The treatment gas passes through a clos~d loop consisting of:
the rotary drum 11; a conduit means 27 which leads from the rotary drum 11 to the blower means 12; a conduit means 28 which leads to the steam superheater 13; and a conduit means 29 which leads back to the rotary drunn 11 .
" ~122~2~
PHA 21.810 7 12.10.1993 Trea~ment gas enters into the rotary drum 11 through the conduit means 29 at an elevated temperature, i.e., elevated above the operating temperature within the rotary drum 11. The hot treatment gas provides the heat of vaporization ~or the volatilizable organic pollutants in the contaminated soil. The treatment gas also provides at least 5 some of the heat necessary for the heat of vaporization of the moisture which is inherent in the contaminated soil. Thus ~he treatment gas generates additional superheated steam from the soil moisture. The treatment gas, the newly created superheated steam and the volatili~ed, volatili~able organic pollu~nts exit from the rotary drum 11 at an exit temperature and an exit pressure and is delivered through conduit means 27 to the pump 10 (blower) means 12 where the pressure of the gases is increased above the exit pressure.
The exit pressure can be sub-atmospheric~ atmospheric or super-atmospheric. Typically the exit pressure is from 0 to 5 psig. The exit temperature is sufficient to maintain the superheated steam in a superheated state at the exit pressure~ and typically is 220~ to 50~F. The blower means 12 increases the treatment gas pressure sufficiently to drive 15 the treatment gas through the superhea~er 13 and the rotary drum 11. Typically the blower/pump means 12 raises the treatment gas pressure to 2 to 15 psig, i.e., several psig above the exit pressure. Relatively low pressures are preferred to avoid any psessure-vessel piping requiremen~, i.e., the need to design, build, test and maintain the system in accordance with indus~y codes ~or pressure-vessels. Centrifugal 20 compressors or positive displacemen~ blowers are preferred as th~ pump means.Optionally, the process may be operated under subatmospheric pressure, e.g., at 14.7 to 13.8 psia. Subatmospheric pressure operation reduces any tendency of the system to leak organic pollutants into the environment. If such subatmospheric operation is employed, then the inner portion of the exit gas stream will pass the pump means 12 and conduits 28, 31, 32 to the condenser 14; the conduit 30 wiLI be closed. During subatmospheric operation, the system must remain relatively free of leaks which n~ight allow air to enter the recirculating superheated 9team 15~op.
e Stearn ~uperheater The steam superheater 13 is a heat transfer device such as an electrical core h~ater or a gas or fuel oil fired heater. Electrical heating i5 preferred for precise control of the process.
21 2222~
PHA 21.810 8 12.10.1993 The pressuriæd treatment gases are delivered from the pump means 12 through the conduit 28 to the steam superheater where the eemperature of the treatment gases is increased above the exit temperature. Typically the temperature of the treatment gases entenng the conduit 29 from the steam superheater 13 will be 500F to 5 1100F. A product stream is withdrawn from the treatment gas loop through conduits 30 or 31.
It should be observed from the preferred embodiment illustrated in FIGURE 1 that the volume of the rot~ drum 11 greatly e~ceeds ~he total volume ofthe conduit means 27, 28, 29 and the pump means 1~ and superheater 13. Thus in any 10 instant, ~he overwhelming majority of the ~eatment gas is in the rotary drum 11 and a minor portion of the recircula~g treatment gas is in the remainder of the closed loop consisting of the conduit means 27, 28, 29, the pump means 12, and the superheater 13.
The Org~ic Pollutant ~Qllç~l Qn Sy~em A portion of the recirculating treatment gas from the conduit 27 or from the conduit 28 is recovered through conduits 30, 31 respeetively and delivered through a conduit 3~ to the condenser 14. The material passing into the condenser 14 corresponds to the moisture and organic pollutant content of the contaminated soil. The condenser is cooled by rneans of coolant fluids which are delivered through a conduit 33, and20 withdrawn through a conduit 35.
If adequate cooling water is available, cool water will enter conduit 33 and heated water will be withdrawn ~hrough conduit 35. If cooling water is not available, a chiller (not shown) may provide chilled coolant fluid through conduit 33.
Heated coolant fluid is withdrawn through conduit 35 and recovered for reuse as 25 coolant.
Substantially all of the superheater steam is cool~d and condensed in the condenser 14 along with substantially all of the condensible vola~iliæd organic pollu~ants. The liquid products from the condenser 14 are delivered through a conduit 36 to the collector 17 which is shown as a decanter. Uncondensed organic pollutants 30 are removed from the decanter 17 through conduit means 40. Light organic pollutants are removed from ~e decanter 17 through conduit m~ns 39. Water is removed from the decanter 17 through conduit means 38. Heavy ~ars, asphalts, carry-over particles, e~c., are withdrawn from the decanter 17 through conduit means 37.
~ ; .. . ~ . : .
2122~24 PHA 21.810 9 12.10.1993 The mass flow rate of treatment gas through the condult means 29 is from 2.5 to 1~ times (preferably 5 to 30 times) the mass flow rate of treatment gas recovered through the conduits 30 or 31. The need for substantial volumes of flow arises from the use of the superheated steam in the treatment gas as a source of heat for 5 vaporization of volatilizable organic pollutants and for vapori~ing moisture ~om the contaminatecl soil within the rotary drum 11. In some embodiments it may be desirable to provide extrinsic heat to the exit gas stream in the conduit means 27 as shown schematically by the heater element 41. The supplemental heat is primarily intended to preclude condensation of volatilized organic pollutants within the conduit 27 and the 10 pump means 12 and the conduits 28, 30, 31 and 32.
Solids Removal It mlay be desirable to remove gas-borne solid panicles ~rom the recircula~ng ~eatment gas in the condui~ 27. An appropriate solidslgas separator 42 15 may be provided along with condui~ means 43 for receiving treatment gas f~om the conduit 27 and conduit means 44 to return to the conduit 27 treatment gas from which solids have been ~moved. The p~ticles from the conduit 45 may be returned to therotary drum 11 or may be otherwise managed. It is desirable that the solids/gas separator 42 be maintained at a temperature above the condensation temperature of the 20 volatili~ed organic pollutants. Appropriate heating means indicated schematically by the numeral 46, are provided to maintain the solids/gas separator 42 at an appropriate eïevated temperature.
~XAMPL~
To illustrate the cost effectiveness of the present inYention, four examples 25 are provided for comparison in which the energy requirements for dec~ntamination of soils by treatment with suyerheat~d steam is calculated for a process according to the invention, in which superheated steam is recycled~ and according to a process in which superheated steam is employed without recycling. In all instanees, the calculations are based on the following: (a) the contaminated soil contains 1% by weight of 30 volatilizable organic pollutants and 20% by weigh~ moisture at arnbient temperature (60F); (b) the decontaminated soil contains less than 0.5 wt percent water and less than 0.001 wt percent of residual organic pollutant, i.e., more th~n 99.9 wt percent of the 2:~222~
"
PHA 21.810 10 12.10.1993 volatilizable organic pollutants were removed; (c) ~he rotary drum is S feet in diameter, weight 7000 lbs. and the soil is heated to 700F.
Four e~amples will highlight the benefits resulting from the practice of the present invention.
S In each example, calculations are made based on the system illustrated in FIGURE 1 with certain changes to be described.
EXAMPLES I, II and m illustrate the cost effectiveness of the invention.
EXAMPLE IV is a comparative example and illustrates the cos~ of using superheated steam in a process without reeycle or recircula~on of superheated steam.
In EXAMPLE I, calculations were based on the system illustrated in FIGUl~ 1 operated on 1 ton per hour of contaminated soil with superheated steam being employed to supply the en~re heat requirements of the system.
In EXAMPLE Il, calculations were based on the sy~tem illustrat~d in FIGURE 1 operated on 1 ton per hour of contaminated soil with indirect heat supplied 15 to the rotary drum and superheated st~n employed to heat the soil and to maintain the contan~inated soil at the desired temperature, 700F, and to offset heat losses from the system to the environment.
In EXAMPLE m, the calculations were based on a system similar to that described in EXAMPLE II except that the throughput is 2 tons per hour.
In comparative EXAMPLli IV, the calculations were based on a system wherein the rotary drum 11 and the recovery system illustrated in fig. 1 were employed, without pump 12, i.e. a system which has no recir~ulating superheated steam and in which superheat~ steasn provides all of the heat energy, is employed on a once-through basis, and the throughput i9 1 ton per hour.
TABLE I sets forth the parameters of each EXAMPLE and the heat requirements and steam re~uLrements.
212222~
....,~
;~ PHA 21.810 11 12.10.1993 TABLE I
ENER~;Y REQUIREMENTS FOR SOIL DECONTAMINATION
s E~MPI~ES
III ~ III I~l FEE~ SO~ omoaracive) Wa~er, w~ 20 20 20 ~0 Orga~ics, wt ~ ~ 1 1 1 1 Temperature (F) 60 50 60 60 FLOW RATE lbs/h~20002000 4000 2000 - Wet 3asi~
~ROD~CT ~OI~
Water wt ~ ~ c0.5~0.5 ~0.5 ~0.5 Organics, wt ~0.001~0.001~0.001~0.001 Exi~ Tempera~ure (F)700 700 700 700 - Dry ~3asis L~L~ 5~-E~ iency)- M9~.U~
Heat Soil to 700 (F)520 520 1040 520 Heat, Vaporize Moisture 665 665 1330 665 ~eat, Vaporize Organics 15 15 30 15 Heat 1~099 300 300 300 300 TSI~Ll5~T ~EQUI~ NTS1500 1500 2700 1500 STEAM REQUIR~M~N~
S/H Steam lbs/hr39252250 2250 3925 S/H Steam to Compre~sor : :
220 ~F) - ACFM1770 1015 1015 N/A :~
S/H Steam t~ Superhea~er 300 (F) -- ACFM1310 750 750 N/A
S/H Steam to Rotary Drlm :
1000 (F) -- ACFM2~20 1600 1600 3925 .~
INDI~ECT ~ aI~I~E O 635 1~35 o ~ ii''".,:`"'''`'.'''''.''.''.''',,``.',`"','`''``''''.' "':`' 212222~
PHA 21.810 12 12.10.1993 From TABLE I it will be observed that the steam requîrement ~or EXAMPLE I is the same as that ~or EX~IPLE IV. In both EXAMPLES I and :lV all of the heat requirement is supplied by superheated steam. Similarly, the superheated S stearn requirement for EXAMPLE II is the same as tha~ of E~AMPLE IlI, despite the fact that EXAMPLE m treats twice the quantity of contaminated soil of ~XAMPLE II.
TA~LE II sets forth the coolillg requirements ~or volatilized organic pollutants and the carrying steam and also a summary of the overall energy requirements.
T~LE II
FNERGY REQUIREMENTS FOR OR&ANIC RECOVERY
I II III LV
(compara~lve) GAS EXIT ST~EAM ~lhalh~) Steam 3925 2250 2250392S
Soil Moisture 390 390 7ao 390 20 Organlcs 20 20 40 20 GAS STREAM TO C^~ E~ s/~r~
Vaporized Mois~-e~390 ~390 ~790~3~0 Organics 20 20 40 20 Recirculating S/H Steam 0 0 0 3925 25 ~QIAh L3S/H~ TQ CONDENSE~ ~410~410 ~020 ~4335 C~ING REQUI~EMENTS
co 60 (F), 75~ Sf~iciency 617 617 1234 5000 M9TUIhr E~ERGY R~Q~L~E~NTS (M~TU/con) 30 S/H Ste~n ^ 1500 365 4335300 Coollng 620 620 6205120 Indirect Heat T3 Rotary Drum 0635 917 o TOTAh ENERGY REQUI~EMENTS 212021201970 10420 M~TU/Ton Ill TABL13 II the cooling requiremen~s per ton of soil processed are identical for EXA~fPLE I, lEX~I:,E II and EXAMPLlEi m.
The cooling requ~rements for EXAMPLE IV are disproportionate because the superheated steam i5 employed on a once-through b~sis.
- 2~2222~
PHA 21.810 13 12.10.1993 Summary of Examples I to IV
From TABLE II it will be observed that substantial savings in the total energy requirements per ton for the described soil decontamination are obtained S according to the invention (compare Examples I, II and III with example IV). It will also be observed that the total energy requirements per ton are least for EXAMPL~i m since the sarne rotary drum is processing twice the throughput with the same heat loss.
The energy requirements for the me~hod illustrated by EXAMPLE IV (without recirculation or recycle of superheated steam) are excessive.
Some of the energy supplied for EXAMPLES II and III is in the form of buming fuel gas or fuel oil which indirectly heat the ro~ary drum and provides therrnal energy at xelatively low cos~ and a~ a significan~y lower cost than electrically heated superheated steam. It is thus possible to reduce the amount of superheated steamrequired to be in the recirculating loop (compare EXAMPLES II, m versus 15 E~AMPLES I, IV) and to thus reduce the siæ of th~ superheater 13 and pump 12 by the use of supplemental heating means.
Ihe process of the invention has been used on a bench scale and found to be effective for decontarnination of contarninated soil from a varie~ of contaminated sites including a former wood treating facility that used creosote and copper, chromium 20 and arsenic forrnulations and a site contaminated with pesticides.
The method and system of the invention have been found to be quite flexible with a wide variety of operating temperatures and residence times depending on the material being treated, are applicable to the cleanup of a variety of contaminants, and are a viable alternative for on-site treatment of so;ls from various contaminated 25 sites.
The method and system may be used in conjunction with the remediation of contaminated solid materials as described and claimed in copending applications U.S.
Se~ial No. en~ed ~fETHOD FOR TREATMENT OF CONT~ATED
MATERIALS WlTH SUP~IEATED STEAM[ I~IEUMAL DESO3~PTION AND
30 l~CYCLE Docket No. 1604-0003-2) and ll.S. Serial No. ~, entitled METHOD
FOR TREAT~NT O~ D~POUNDED SLUDGES, SOILS AND OTH~R
CONTA~NATED SOLID ~iATERlALS (Docket No. 1604-0003-1), both filed 212222~
~: PHA 21.~10 14 12.10.1993 concurrently and commonly assigned herewith, the disclosures of which are incorporated herein by thiis re~erence.
Claims (23)
1. A method for reducing the volatilizable organic pollutant content of soil which is contaminated with at least one volatilizable organic pollutant, comprising:
delivering contaminated soil to a treatment zone and passing said contaminated soil through said treatment zone in vapor/solids contact with treatment vapors comprising predominantly superheated steam and devolatilized organic pollutant whereby moisture from said contaminated soil is converted to steam and a substantial portion of said volatile organic pollutant is volatilized;
maintaining said treatment zone at a pre-selected temperature to cause moisture from said soil to convert to steam and a substantial portion of said organic pollutants to volatilize, recovering from said treatment zone a relatively dried soil having substantially lower pollutant content than said contaminated soil;
recovering as an exit gas stream at an exit temperature and an exit pressure the treatment vapors from said treatment zone, said exit gas stream comprising predominantly superheated steam and a minor portion of volatilized organic pollutants;
and recirculating a major portion of said recovered exit gas steam at a pressure and temperature greater than said exit pressure and said exit temperature and comprising predominantly superheated steam and a minor portion of volatilized organic pollutant to said treatment zone as the treatment vapors therein.
delivering contaminated soil to a treatment zone and passing said contaminated soil through said treatment zone in vapor/solids contact with treatment vapors comprising predominantly superheated steam and devolatilized organic pollutant whereby moisture from said contaminated soil is converted to steam and a substantial portion of said volatile organic pollutant is volatilized;
maintaining said treatment zone at a pre-selected temperature to cause moisture from said soil to convert to steam and a substantial portion of said organic pollutants to volatilize, recovering from said treatment zone a relatively dried soil having substantially lower pollutant content than said contaminated soil;
recovering as an exit gas stream at an exit temperature and an exit pressure the treatment vapors from said treatment zone, said exit gas stream comprising predominantly superheated steam and a minor portion of volatilized organic pollutants;
and recirculating a major portion of said recovered exit gas steam at a pressure and temperature greater than said exit pressure and said exit temperature and comprising predominantly superheated steam and a minor portion of volatilized organic pollutant to said treatment zone as the treatment vapors therein.
2. The method of claim 1 including the additional step of heating said treatment zone and its contents independently of said superheated steam.
3. The method of claim 1 including the additional steps of recovering a minor portion of said exit stream and cooling said minor portion of said exit gas stream to condense superheated steam and to condense substantially all of the condensible volatilized organic pollutants therein to a liquid state.
4. The method of claim 3 wherein the mass flow ratio of said exit gas stream to the mass flow of said minor portion of said exit gas stream exceeds between 5:1 to 30:1.
5. The method of claim 1 wherein said exit pressure is less than 10 psig.
6. The method of claim 1 wherein said exit pressure is less than one atmosphere.
7. The method of claim 1 wherein said exit gas stream contains gas-borne particles and said exit gas stream is passed through a solids-gas separator to remove a substantial quantity of said gas-borne particles from said exit gas stream.
8. The method of claim 7 wherein said solid-gas separator is heated to maintain an elevated temperature therein above the temperature of gas and solids in said separator.
9. The method of claim 1 wherein said treatment zone is a rotary drum.
10. The method of claim 9 wherein the rotary drum is heated to provide a portion of the thermal energy required to heat said contaminated soil and to maintain said rotary drum at a pre-selected temperature profile.
11. A method for reducing the volatilizable organic pollutant content of particulate soil which is contaminated with at least one volatilizable organic pollutant, comprising:
delivering contaminated particulate soil to a treatment zone and passing said contaminated soil through said treatment zone in vapor/solids contact with treatment vapors comprising predominantly superheated steam whereby moisture from said contaminated particulate soil is converted to steam and a substantial portion of said volatile organic pollutant is volatilized;
heating said treatment zone to maintain a pre-selected temperature therein;
recovering from said treatment zone a dried, particulate soil having substantially lower pollutant content than said contaminated particulate soil;
recovering as an exit gas stream at an exit temperature and an exit pressure the treatment vapors from said treatment zone, said exit gas stream comprising predominantly superheated steam and a minor portion of volatilized organic pollutants;
removing a minor portion of said exit gas stream;
increasing the pressure of the remaining exit gas stream to a pressure greater than said exit pressure and heating the resulting pressurized gas stream to an elevated temperature above said exit temperature;
recirculating the resulting gas stream at a pressure and temperature greater than said exit pressure and said exit temperature and comprising predominantly superheated steam and a minor portion of volatilized organic pollutant to said treatment zone as the treatment vapors wherein, whereby said gas stream and said treatment vapors comprise predominantly superheated steam; and cooling said removed minor portion of said exit gas stream to condense superheated steam and to condense substantially all of the condensible volatilized organic pollutants therein to a liquid state.
delivering contaminated particulate soil to a treatment zone and passing said contaminated soil through said treatment zone in vapor/solids contact with treatment vapors comprising predominantly superheated steam whereby moisture from said contaminated particulate soil is converted to steam and a substantial portion of said volatile organic pollutant is volatilized;
heating said treatment zone to maintain a pre-selected temperature therein;
recovering from said treatment zone a dried, particulate soil having substantially lower pollutant content than said contaminated particulate soil;
recovering as an exit gas stream at an exit temperature and an exit pressure the treatment vapors from said treatment zone, said exit gas stream comprising predominantly superheated steam and a minor portion of volatilized organic pollutants;
removing a minor portion of said exit gas stream;
increasing the pressure of the remaining exit gas stream to a pressure greater than said exit pressure and heating the resulting pressurized gas stream to an elevated temperature above said exit temperature;
recirculating the resulting gas stream at a pressure and temperature greater than said exit pressure and said exit temperature and comprising predominantly superheated steam and a minor portion of volatilized organic pollutant to said treatment zone as the treatment vapors wherein, whereby said gas stream and said treatment vapors comprise predominantly superheated steam; and cooling said removed minor portion of said exit gas stream to condense superheated steam and to condense substantially all of the condensible volatilized organic pollutants therein to a liquid state.
12. The method of claim 11 including the additional step of heating said treatment zone and its contents independently of said superheated steam.
13. The method of claim 11 wherein the mass flow ratio of said exit gas stream to the mass flow of said minor portion of said exit gas stream exceeds between 5:1 to 30:1.
14. The method of claim 11 wherein said exit pressure is less than 10 psig.
15. The method of claim 11 wherein said exit pressure is less than one atmosphere.
16. The method of claim 111 wherein said exit gas stream contains gas-borne particles and said exit gas stream is passed through a solids-gas separator to remove a substantial quantity of said gas-borne particles from said exit gas steam.
17. The method of claim 11 wherein said treatment zone is a rotary drum.
18. The method of claim 11 wherein the rotary drum is heated to provide at least a major portion of the thermal energy required to heat said contaminated soil and to maintain said rotary drum at a pre-selected temperature profile.
19. Apparatus for treating solid materials which are contaminated with at least one organic pollutant in order to reduce the content of said pollutant, including:
(a) a treatment zone having a treatment chamber, means for introducing contaminated solid materials into said chamber, means for recovering dried particulate solid materials from said chamber having a substantially reduced organic pollutant content, means for introducing treatment vapors into said treatment chamber, means for establishing effective vapor/solids contact in said chamber between said treatment vapors and said solid materials, and means for recovering an exit gas stream from said chamber comprising predominantly superheated steam and a minor portion of vaporized moisture from said solid materials and a minor portion of volatilized organic pollutant;
(b) a gas-pressurizing means; a gas-heating means; first conduit means extending from said chamber means to said gas pressurizing means; second-conduitmeans extending from said gas-pressurizing means to said gas-heating means; and third conduit means extending from said gas-heating means to said treatment chamber, providing a closed loop for circulation of treatment vapors from said treatment chamber through said first conduit, through said gas-pressurizing means, through said second conduit means, through said gas-heating means, and through said third conduit means to said treatment chamber;
(c) condenser means for cooling a gas stream; fourth conduit means connecting said condenser means and said first conduit means or said second conduit means for delivering a gas stream from said first conduit means or said second conduit means to said condenser means.
(a) a treatment zone having a treatment chamber, means for introducing contaminated solid materials into said chamber, means for recovering dried particulate solid materials from said chamber having a substantially reduced organic pollutant content, means for introducing treatment vapors into said treatment chamber, means for establishing effective vapor/solids contact in said chamber between said treatment vapors and said solid materials, and means for recovering an exit gas stream from said chamber comprising predominantly superheated steam and a minor portion of vaporized moisture from said solid materials and a minor portion of volatilized organic pollutant;
(b) a gas-pressurizing means; a gas-heating means; first conduit means extending from said chamber means to said gas pressurizing means; second-conduitmeans extending from said gas-pressurizing means to said gas-heating means; and third conduit means extending from said gas-heating means to said treatment chamber, providing a closed loop for circulation of treatment vapors from said treatment chamber through said first conduit, through said gas-pressurizing means, through said second conduit means, through said gas-heating means, and through said third conduit means to said treatment chamber;
(c) condenser means for cooling a gas stream; fourth conduit means connecting said condenser means and said first conduit means or said second conduit means for delivering a gas stream from said first conduit means or said second conduit means to said condenser means.
20. The apparatus of claim 19 including heating means for heating said treatment chamber independently of said superheated steam.
21. The apparatus of claim 19 wherein said treatment zone is a rotary drum.
22. The apparatus of claim 19 including gas/solids separating means in said first conduit means.
23. The apparatus of claim 22 including heating means for maintaining a pre-selected temperature within said gas solids separating means.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US5543393A | 1993-04-29 | 1993-04-29 | |
| US055,433 | 1993-04-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2122224A1 true CA2122224A1 (en) | 1994-10-30 |
Family
ID=21997762
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002122224A Abandoned CA2122224A1 (en) | 1993-04-29 | 1994-04-26 | Method and apparatus for soil remediation with superheated steam thermal desorption and recycle |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US5613452A (en) |
| CA (1) | CA2122224A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6840712B2 (en) | 2002-01-03 | 2005-01-11 | Hood Environmental Engineering, Ltd. | Thermal remediation process |
Families Citing this family (24)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1998052704A1 (en) * | 1997-05-20 | 1998-11-26 | Shell Internationale Research Maatschappij B.V. | Remediation method |
| US6464430B1 (en) * | 1999-10-27 | 2002-10-15 | Tom L. Maleck | Soil decontamination apparatus and method |
| WO2003035290A1 (en) * | 2001-10-24 | 2003-05-01 | Shell Internationale Research Maatschappij B.V. | Thermally enhanced soil decontamination method |
| US7534926B2 (en) * | 2003-05-15 | 2009-05-19 | Board Of Regents, The University Of Texas System | Soil remediation using heated vapors |
| US7004678B2 (en) * | 2003-05-15 | 2006-02-28 | Board Of Regents, The University Of Texas System | Soil remediation with heated soil |
| DE10323774A1 (en) * | 2003-05-26 | 2004-12-16 | Khd Humboldt Wedag Ag | Process and plant for the thermal drying of a wet ground cement raw meal |
| US7228822B2 (en) * | 2003-10-14 | 2007-06-12 | Goodfield Energy Corporation | Vapor generator using pre-heated injected water |
| US7721679B2 (en) * | 2003-10-14 | 2010-05-25 | Goodfield Energy Corporation | Vapor generator with preheater and method of operating same |
| US7293532B2 (en) * | 2003-10-14 | 2007-11-13 | Goodfield Energy Corp. | Heavy oil extraction system |
| FI123396B (en) * | 2007-04-19 | 2013-03-28 | Savaterra Oy | Method for producing fertilizer from sludge |
| US8616000B2 (en) * | 2008-06-13 | 2013-12-31 | Michael J. Parrella | System and method of capturing geothermal heat from within a drilled well to generate electricity |
| US20100270002A1 (en) * | 2008-08-05 | 2010-10-28 | Parrella Michael J | System and method of maximizing performance of a solid-state closed loop well heat exchanger |
| US8534069B2 (en) * | 2008-08-05 | 2013-09-17 | Michael J. Parrella | Control system to manage and optimize a geothermal electric generation system from one or more wells that individually produce heat |
| US20100270001A1 (en) * | 2008-08-05 | 2010-10-28 | Parrella Michael J | System and method of maximizing grout heat conductibility and increasing caustic resistance |
| US9423158B2 (en) * | 2008-08-05 | 2016-08-23 | Michael J. Parrella | System and method of maximizing heat transfer at the bottom of a well using heat conductive components and a predictive model |
| DE102010025206A1 (en) * | 2010-06-22 | 2011-12-22 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Process for recovering volatiles from a solid |
| US9004817B2 (en) * | 2010-12-21 | 2015-04-14 | Empire Technology Development Llc | Soil remediation systems and methods |
| US20150159918A1 (en) * | 2011-05-04 | 2015-06-11 | Gtherm Inc. | Swegs adapted for use in cooling, heating, voc remediation, mining, pasteurization and brewing applications |
| CA2951230A1 (en) * | 2014-06-06 | 2015-12-10 | Boldwater Usa, Lp | Processes for remediation of a contaminated material |
| US10875062B2 (en) * | 2018-10-04 | 2020-12-29 | Ezraterra, Llc | Sintered wave porous media treatment, apparatus and process for removal of organic compounds and nondestructive removal and condensation of per and polyfluoroalkyl substances and related fluorinated compounds |
| CZ309369B6 (en) * | 2021-01-26 | 2022-10-12 | IMPEX TRADE CZ, s.r.o. | Method of decontaminating hazardous substances from solid materials |
| CN113426820B (en) * | 2021-08-02 | 2023-04-07 | 安徽省通源环境节能股份有限公司 | Superheated steam thermal desorption device |
| CN114345916B (en) * | 2022-01-06 | 2022-11-18 | 中国科学院武汉岩土力学研究所 | Novel in-situ thermal evaporation displacement restoration test system for organic contaminated soil |
| US11768189B2 (en) | 2022-02-16 | 2023-09-26 | Patrick Richard Brady | Detection, characterization, and mapping of subsurface PFAS-stabilized viscoelastic non-Newtonian LNAPLS using rheological methods |
Family Cites Families (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3212197A (en) * | 1961-06-08 | 1965-10-19 | James R Crawford | Drying method and apparatus |
| US3525673A (en) * | 1969-03-24 | 1970-08-25 | Eric C Cameron | Closed,controlled system for carbonizing organic refuse |
| US3991481A (en) * | 1975-05-28 | 1976-11-16 | E. I. Du Pont De Nemours And Company | Process for recovering volatile organic liquids |
| US4217222A (en) * | 1977-03-21 | 1980-08-12 | Harendza Harinxma Alfred J | Apparatus for processing municipal solid waste and sewage sludge |
| US4676908A (en) * | 1984-11-19 | 1987-06-30 | Hankin Management Services Ltd. | Waste water treatment |
| US4738206A (en) * | 1986-09-16 | 1988-04-19 | Roy F. Weston, Inc. | Apparatus and method for low temperature thermal stripping of volatile organic compounds from soil |
| US5199354A (en) * | 1988-11-18 | 1993-04-06 | Tps Technologies, Inc. | Mobile soil remediation system |
| US5142998A (en) * | 1989-11-28 | 1992-09-01 | Feitel Frederick E | Apparatus and method for treating contaminated gas emissions |
| US4974528A (en) * | 1989-12-08 | 1990-12-04 | Ryan-Murphy, Inc. | Method and apparatus for the treatment of contaminated soil |
| US5187131A (en) * | 1990-01-16 | 1993-02-16 | Tigg Corporation | Method for regenerating particulate adsorbents |
| US5052313A (en) * | 1990-04-19 | 1991-10-01 | Combustion Design Corporation | Waste treatment system and method |
| US5228803A (en) * | 1990-06-12 | 1993-07-20 | Richard A. Crosby | Apparatus and method for thermally stripping volatile organic compounds from soil using a recirculating combustible gas |
| US5272833A (en) * | 1990-08-28 | 1993-12-28 | Asphalt Product Technologies, Inc. | Soil remediation apparatus and method for same |
| US5072674A (en) * | 1990-12-13 | 1991-12-17 | Roy F. Weston, Inc. | Apparatus and method for low temperature thermal stripping of volatile organic compounds from soil with non-oxidative cross-sweep gases |
| US5121699A (en) * | 1991-02-12 | 1992-06-16 | Frank Lowell C | Reclamation method and apparatus for soil and other products |
| US5103578A (en) * | 1991-03-26 | 1992-04-14 | Amoco Corporation | Method and apparatus for removing volatile organic compounds from soils |
| US5245113A (en) * | 1991-05-23 | 1993-09-14 | Dynecology, Incorporated | Decontamination of PCB contaminated solids |
| US5188041A (en) * | 1991-12-17 | 1993-02-23 | Roy F. Weston, Inc. | Apparatus and method for low temperature thermal stripping of volatile organic compounds from soil and waste materials with non-oxidative co-current gases |
| US5152233A (en) * | 1992-01-30 | 1992-10-06 | Heyl & Patterson, Inc. | Method of devolatilizing earth solids and mobile truck for carrying out the method |
-
1994
- 1994-04-26 CA CA002122224A patent/CA2122224A1/en not_active Abandoned
-
1995
- 1995-03-30 US US08/419,292 patent/US5613452A/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6840712B2 (en) | 2002-01-03 | 2005-01-11 | Hood Environmental Engineering, Ltd. | Thermal remediation process |
Also Published As
| Publication number | Publication date |
|---|---|
| US5613452A (en) | 1997-03-25 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2122224A1 (en) | Method and apparatus for soil remediation with superheated steam thermal desorption and recycle | |
| US5216821A (en) | System and method for removing a volatile component from a matrix | |
| US4715965A (en) | Method for separating and recovering volatilizable contaminants from soil | |
| AU659120B2 (en) | Apparatus and process for removing contaminants from soil | |
| US5242245A (en) | Method and apparatus for vacuum enhanced thermal desorption of hydrocarbon and other contaminants from soils | |
| US5405579A (en) | Decontamination of polluted soils | |
| EP0303339B1 (en) | Method and apparatus for treating sludges | |
| US5292429A (en) | Process for recovery and treatment of a diverse waste stream | |
| CA2468720C (en) | Thermal remediation process | |
| EP0344946B1 (en) | Method and apparatus for treating waste paint sludge | |
| US5188041A (en) | Apparatus and method for low temperature thermal stripping of volatile organic compounds from soil and waste materials with non-oxidative co-current gases | |
| AU727756B2 (en) | Process and apparatus for treating process streams from a system for separating constituents from contaminated material | |
| AU2006341575A2 (en) | Method and apparatus for processing of materials | |
| US4948511A (en) | Method for extracting dissolved organic pollutants from aqueous streams | |
| US5514286A (en) | Thermal desorption unit | |
| CN107855354A (en) | A kind of organic polluted soil thermal desorption prosthetic device and method | |
| DE60217183T2 (en) | DEVICE FOR DRYING A PARTICULAR PRODUCT WITH OVERHEATED STEAM | |
| WO2003018954A1 (en) | System and method for processing cuttings polluted with oil-based mud | |
| CN113426820A (en) | Direct thermal desorption device of overheated formula steam | |
| CA2122232A1 (en) | Method for treatment of contaminated materials with superheated steam thermal desorption and recycle | |
| US5176087A (en) | Apparatus and method for low temperature thermal stripping of volatile organic compounds from soil and waste materials with non-oxidative cross-sweep gases | |
| EP0285231A1 (en) | Method and apparatus for treating mixed organic and inorganic wastes | |
| EP0561955A1 (en) | A method of continuously decontaminating a material, and an assembly for carrying out the method. | |
| WO2006033718A1 (en) | Dewatered sludge soil enrichment method | |
| AU712838B2 (en) | Volatile materials treatment system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |