CA1172837A - Process for the production of sintered bauxite spheres - Google Patents
Process for the production of sintered bauxite spheresInfo
- Publication number
- CA1172837A CA1172837A CA000381189A CA381189A CA1172837A CA 1172837 A CA1172837 A CA 1172837A CA 000381189 A CA000381189 A CA 000381189A CA 381189 A CA381189 A CA 381189A CA 1172837 A CA1172837 A CA 1172837A
- Authority
- CA
- Canada
- Prior art keywords
- particles
- bauxite
- fractions
- continuously
- layer
- 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.)
- Expired
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/021—After-treatment of oxides or hydroxides
- C01F7/025—Granulation or agglomeration
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/80—Compositions for reinforcing fractures, e.g. compositions of proppants used to keep the fractures open
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/30—Particle morphology extending in three dimensions
- C01P2004/32—Spheres
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/50—Agglomerated particles
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/51—Particles with a specific particle size distribution
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/51—Particles with a specific particle size distribution
- C01P2004/52—Particles with a specific particle size distribution highly monodisperse size distribution
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/10—Solid density
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/21—Attrition-index or crushing strength of granulates
Abstract
Abstract of the disclosure: High strength sintered bauxite spheres usable as fracture propping agents in oil ox gas wells are produced by continuous spray-granulation of an aqueous binder-containing bauxite suspension to form granules which are subsequently sintered to high strength and high density spheres.
Description
,J ~
BACKGROUND OF THE INVENTION.
It is well known that the productivity of an oil or gas well may often be increased by a procedure jwhich involves crea~ing a fracture in the subterranean 5 Iformations surrounding a well and propping the fracture opening by filling it with granular material called propping agent. Methods of this type are disclosed in US-patent specifications Nos. 3 701 383 and 4 068 718.
¦ A survery of propping agents and their manufacture is given in the specification to German Offenlegungsschrift 29 21 336.
A granular material must fulfil several condi-Itions to be suitable for use as a propping agent. The 15 ¦material must have hiyh strength to avoid crushing of the particles when exposed to high pressure during their application~ The shape of the individual particle should depart as little as possible from the spherical one and the particle size distribution should be within defined, relative narrow limits to insure sufficien~
gas and oil permeability of fractures propped with the propping agent. Moreover, the particles should be able to resist the corrosive conditions to which they may be exposed at their application.
~5 The material regarded as most suitable for ful-filling these conditions is sintered bauxite pellets.
Several methods have been proposed ~ox producing sintered bauxlte paxticles. The process which has hither-'to found widest commercial success is the one described in the above German Offenlegungsschrift 29 21 336.
According to said methods bauxite spheres arefirst prepared by agglomeration of a mixture of bauxite, temporary binder and water in an intensive mixer to produce spheres called green pellets, which are after-wards sintered by heating. In the embodiment examplesof said application the products have a typical density :
:
72~3~
of 3.7 g/cm3, while the crushing loss measured by the method described below was 8,16~ and 6,~, resp.
It is however, a drawback of said process that the granulation, which is carried out in an intensive mixer, can only be perEormed batch-~ise. Moreover, said prior art process usually requir~s a preliminary drying of the starting material.
SUMMARY 0~ THE INVENTION:
It is, however, generally recognized that us~a~ly a continuous process is to be preferred to a batch-wise process when a large-scale industrial production is concerned.
It is therefore an object of the invention to provide a process for the production of sintered bauxite spheres comprising steps all of which may be performed continuously.
Since any crushing of the bauxite spheres by ~:~ their use as fracture propping agents involves an im-paired permeability of the propped fracture it is desired to obtain a strength of spheres corresponding to an crushing loss even lower that the results obtained according to said German Offenlegungsschrift 29 21 336.
Consequently it is an other object o~ the inven-tion to provide a process resulting in bauxite spheres havlng a crushing 1QSS measured by the below defined method of les~ that S%.
In the above prior art process using an intensive mixer the possibilities are rather limited for control-ling the granulometry of the product, e.g. because a certain minimum mixing intensity will always be necessa-ry to secure homogeneity of the individual particles.
This means that a product having a very narrow particle size distribution, as is often required for propping .
3, ri~
agents, can only be prepared by simultaneous product.ion of a substantial amount of partlcles being too small or : too large, which necessitates extensivé sieving opera-tions and impairs total process economy.
Therefore it is a further object of the invention to provide a process which may easily be adapted to produce a major fraction of particles complying to varying requirements as to particle size distribution.
I The above objects are according to the invention achieved by a process for the production of sintered bauxite spheres having a particle size range from 0O4 to 2.5 mm, or a more narrow particle size range within said limits,suitable for use as fracture propping agent in oil wells, which process comprises the steps of (a) preparing an aqueous feed suspension comprising bauxite and a binder, (b) continuously atomizing said feed suspension into a layer of alxeady partly dried bauxite particles fluidized in a stream of drying air, (c) continuously recovering particles from said layer (d) continuously separating said recovered particles in oversize, unde.rsize and product fractions, making allowance for shrinkage in the subsequent sintering operation, (e) continuously recycling material selected :Erom the group cons:Lsting of undersize fractions, xelat.tve f:ine product fractions, ground product fractions and ground oversize fractions, to the layer o fluidized particles at a site at substantial distance, measured along the flow path of the par-ticles,from the site where said recovering of par-ticles takes place, and (f) drying and sintering the non-recycled product fractions by heating them at a temperature between 1200 and 1650C.
~ ', :
A method involving steps in principle correspon-ding to the above steps (b)-(e) is called ~luidized spray granulation and has been suggested ~or the granu-lation of various inorganic and organic products. Spray granulations has, howe~er, not been suggested for the manufacture of green proppant pellets and the suitabili-ty of the method for this specific purpose could in no way be predicted. In ~act it is rather surprising that a perfect spherical shape of the pellets ca~ be obtained, considering the very rapid evaporations o~ the atomized suspension in the process.
The crushing strength of the resulting sintered particles is to a substantial extent dependent on the homogenity of the green proppant pellets, and it is ; 15 also rather surprising that a spray granulation process is able to produce pellets which are supperior also in that respect.
In the present specification and in the accompany-ing claims "bauxite" is used in the widest sense of the word comprising also very low grade materials.
All steps of the process of the invention may be carried out in a continuous manner, which makes -the process especially attractive for large scale proppant manuEacture. It is a further advant~ge of khe process that -the prellminaxy drying necessary in prior art methods is disposed oE.
By using the steps (a)-(e) it :Ls possible to ob-tain pellets of spherical shape and of sufEicient strength for handling prior to and during the final drying and sintering process. After sintering these pellets form propping agents of higher strength than described in the prior art.
.
~ 17 2 ~ ~
DESCRIPTION OF THE DRAWING.
The invention is further elucidated with reference to the drawing, which is a schematic flow sheet illu-strating an embodiment of the process.
S DESCRIPTION OF THE INVENTION.
On the drawing a feed tank is designatPd 1. In this tank an aqueous feed suspension comprising bauxite and a binder is prepared. Preferably the feed contains 40-60, more preferably approximately 50 t % by weight bauxite (as defined abov'e~ and preferably 0.25-5, more preferably 0.5-2.5, % by weight binder. The bauxite should preferably have a particle size below 20 micron which îs conveniently achieved by a wet grinding process which is less energy consuming than dry milling prescribed in connection with some of the prior art processes.
The preferred binders are polyvinyl aceta~e, polyvinyl alcohol, methylcellulose, dextrin and molasses.
The function of the binder is to provide green 20 1 strenyth to the pellets until the sinterlng thereo~.
During the sintering most of the binders comming lnto consideration will decompose.This means ~hat ~ relakively h:Lyh amount Oe binder will impair the str~n~th Oe the e inal sintexed product, for which reason blnders are preEerred ~hich exhibi-t ~ sueficient temporary binding ahility even when used in small amounts.
Also further auxiliary agents may be added to the feed, such as dispersing agents, e.g~ ammonium citrateO
From the tank 1 the feed is led to a pump 2 feeding atomizing nozzles 3 arranged in a fluidized bed unit 4.
: , .' ' , . : , ,:
1~72~37.
:~ Between the feed tank 1 and the nozzles 3 may be inserted a grinding mill and/or a sieve tnot shown), to prevent that too coarse particles reach the nozzles and the fluid bed.
The atomizing nozzles 3 are pressure nozzles o~
conventional design~ or two-fluid nozzles. The design of such nozzles is well known e.g. from K. Masters:
''Spray Drying Handbook", John Wiley and Sons, New York ` ~1979).
The fluid bed unit 4 is of conventional desig~
Ias described in e.g. US patent specification 3 533 829 and in British patent specification 1 401 303 In the illustrated~em~odiment a fluidized par-ticle layer 5 is supported by a perforated plate 6 through which hot fluidizing gas is flowing. Said hot gas is introduced in the bottom part of the fluid bed unit by means of a fan 7 and an air heater 8.
The distance from the atomizing nozzles 3 to the ~erforated plate 6 is adjustable and the nozzles 20 1 are pr~ferably possitioned a rather short distance ¦above the surface of the fluidized particle layer 5.
The exact position of the nozzles will in each indivi-ldual case be fixed with due regard to the fact that too ! long distance from the nozzles to the surface of the fluidized layer causesundesired dus-t formation, because the atomized feed droplets will be dried to -too high an extent, before they reach the fluidized layer, whi].e a too short distanae on the other hand results in for-mation of irregular and too coarse particles. Therefore, the position of the nozzles is adjusted on the basis of analyses of powder taken out from the fluid bed unit.
The v~locity of the fluidizing and drying air passing the layer 5 is preferably 0 T 9-1.5 m/sec.
and the height of the fluidized particle layer will ty-.` ' ' . .
: , ' , , 3~
pically be 20-~0 cm.
The temperature oE the drying- and 1uldiziny air when introduced at -the botkom part of the fluid bed unit - 4 will preferably be 250-650 C, more preferably 400-600C.
When leaving the fluid bed unit the tempera-ture of said air is preferably below 100C, more preerably - approximately 70C.
- From the fluid bed unit the ai~ entraining dust consisting primarily of fine bauxite particles are led to a collector means 9, which may for instance be an electrostatic precipitator, a cyclone, a bag filter or a wet scrubber or a combination thereof.
Particles recovered in the collector means 9 may be recycled to the feed tank 1 and/or to the fluidized bed unit 4. It has turned out that the fine paxticles collected in 9 are very suitable for being recycled as seed particles to the fluidized bed due to their uniform spheroidal shape, and in this respect they are supperior to other seed particles obtained by grinding as explained below.
It is essential tha-t -the fluid bed unit 4 is designed to give a long and uni~orm residence time or the particles to obtain a desired particle ~.Lze distri~
25 jbu-tion and the des.ired spherical shape o~ the procluct.
Therefore, the ~low of particles ln the fluidizcd layer shoul.d be o~ the type conventionally termecl plug Elow, which is a ~low pattern wherein very li-ttle back mixiny takes place. Thereby an equal treatment of all particles is secured.
In a fluidized particle layer plug flow of the particles may be obtained by various measures. In the embodiment shown on the drawing the desired flow pattern is obtained by introducing powder particles serving as seeds or nuclei through a powder inlet 10 in one end of .,. ' ., ~ .
,.
.~,. .
3 ~
the fluid bed uni-t 4 and removing particles from the fluidized layer 5 through an outlet 11 situated at the opposite end o~ the ~luid bed unit. Alternatively - plug flow may be obtained by using guide walls in ~he fluid bed as is well known in the art.
The seed or nuclei particles introduced through powder inlet 10 consist of rec~cled material as will be explained a~ove and further elucidated below.
I Alternatively to the illustrated embodiment the 10 ~fluid bed unit may comprise two or several compartments in which different conditions prevail as to fluidizing air velocity, temperature and slurry feeding conditions ~Such fluid bed units having more than one compartment are well known in the art, and may e.g. have a circular perforated plate and radian partitions preventing back mixing.
Through the powder outle-t 11 is withdrawn a pow-der having a moisture content of 1-5~ which powder via a rotary valve 12 is conducted to a sieving unit 13 wherein it is separated into three or more fractions, viz. an oversize fraction, one or more product fractions - (in the embodiment shown: two fractions) and an under-- size fraction.
The oversize ;fraction is conductecl to a grind:Lny unit comprising a mill 14 and a ~ieve 15 which may possibly be comhi.ned. Oversize makerlal are recycled from the sieve 15 -to the miLI. 14 and fractions having preferably a slze of app. 0.5 mm are, in the embodiment shown, led to the powder inlet 10 of the fluid bed unit together with the fine fraction. In case the quantity of material of these two fractions, together with material collected in 9, is not sufficient to form seed or nuclei material for the fluid bed, a part of the product fraction or of one of the produc~ ~ractions may be added thereto as indicated by the dotted line in the .
:;
. "
., .
lower part of the drawing. A part o or the total amount of recycled product fraction may be ground before being introduced to the fluid bed, as indicated on the drawing. Qn the other hand, if the amount of material in the oversize fraction together with the undersize fraction is higher than what is required to supplement seed or nuclei material, a part thereof may be added to the feed tank 1, as illustrated by the dotted line in the left upperpart of the drawing.
10 j Non-recycled product fraction or fractions are led to a drying oven 16 wherein residual moisture and organic additives are evaporated and thereafter to a kiln 17, e.g. a rotary kiln, wherein the particles are !sintered to form high strength spheres suitable as prop-ping agents. The firing process taking place in the kiln 17 is conducted under the same conditions as those used in the prior art processes in which an agglomeration has ~een performed in a mixing apparatus.
; The size limits for the product fractions separa-ted in the sieving unit 13 must be fixed with due regard to the fact that in the s~bsequent firing pro-cess in the kiln 17 a substantial shrinkage takes - place. The extent of this shrinkage depends on the ori-gin of the original bauxite and may typlcally clmount to app. 25% on linear basis.
¦ As it appears the process may be p~rformed on a continuous basis and it ls very suitable for being ; automatically controlled using a rninirnurn of manpower.
As mentioned above the resulting propping agent !~ 30 has higher density and higher crushing strength than obtained in the embodiment examples of the above men-tioned German application. The crush~g strength is evalu-ated by a method in which the fraction between app. 600 microns and app. 700 microns is placed in a 1 5/8 inch diameter steel cylinder, and pressuré is applied to the ~, ' , .
:. . . ..
;' .. . .
~ ~ ~72~3~
: 10 sample through a plunyer fitting the -top o~ -the cylirlder according to the following schedule: 1 minute to 700 kg/cm2, 3 minutes hold at th.is pressure and 1 mlnute down to 0 pressure. Afterwards the amoun-t o material having a particle size below 600 microns is measured and expressed as % of the total amount. The result ls recorded as the weight ~ crushing loss.
The inven-tion is further elucidated by means of the following embodiment example.
10 Example 1 The process is carried out in a plant correspon-ding to the one illustrated on the drawing.
In the feed tank a feed suspension is prepared from water, fresh bauxite, recycled bauxite dust from 15 the collector unit and the below indicated auxiliary agents in amounts giving a total solids content of the feed~suspension of app. 50% by weight, which solids con-sist o, ca.93% bauxite, 1% polyvinylalkohol and.0,3~ ammo-nium citrate. This feed is in an amount of 4000 kg/hour atomized through the pressure nozzles 3 in a fluid bed unit in principle designed as shown on the drawing and having a fluidizing area oE 3 m2.
The velocity of the Eluidi.zing air is 1.2 m/sec, - and the inlet tempera-ture o the alr :Ls 550C while the outlet temperature is 70C. Recycled mater:La:l lntroduced : through the powcler inlet 10 amount~ to 1700 kg/hour. The height of the fluidized particle layer 5 is app. 35 cm.
The average residence time of the particles in the fluidi~ed layer may under these conditions be estimated to 15 minutes.
. Through the outlet 11 material is withdrawn in a quanti~y of 3400 kg/hour, which by sieving is sepa-rated in an oversize fraction having a particle si.ze above 2.1 mm (50 kg/hour), a coarse product fraction ', ' '
BACKGROUND OF THE INVENTION.
It is well known that the productivity of an oil or gas well may often be increased by a procedure jwhich involves crea~ing a fracture in the subterranean 5 Iformations surrounding a well and propping the fracture opening by filling it with granular material called propping agent. Methods of this type are disclosed in US-patent specifications Nos. 3 701 383 and 4 068 718.
¦ A survery of propping agents and their manufacture is given in the specification to German Offenlegungsschrift 29 21 336.
A granular material must fulfil several condi-Itions to be suitable for use as a propping agent. The 15 ¦material must have hiyh strength to avoid crushing of the particles when exposed to high pressure during their application~ The shape of the individual particle should depart as little as possible from the spherical one and the particle size distribution should be within defined, relative narrow limits to insure sufficien~
gas and oil permeability of fractures propped with the propping agent. Moreover, the particles should be able to resist the corrosive conditions to which they may be exposed at their application.
~5 The material regarded as most suitable for ful-filling these conditions is sintered bauxite pellets.
Several methods have been proposed ~ox producing sintered bauxlte paxticles. The process which has hither-'to found widest commercial success is the one described in the above German Offenlegungsschrift 29 21 336.
According to said methods bauxite spheres arefirst prepared by agglomeration of a mixture of bauxite, temporary binder and water in an intensive mixer to produce spheres called green pellets, which are after-wards sintered by heating. In the embodiment examplesof said application the products have a typical density :
:
72~3~
of 3.7 g/cm3, while the crushing loss measured by the method described below was 8,16~ and 6,~, resp.
It is however, a drawback of said process that the granulation, which is carried out in an intensive mixer, can only be perEormed batch-~ise. Moreover, said prior art process usually requir~s a preliminary drying of the starting material.
SUMMARY 0~ THE INVENTION:
It is, however, generally recognized that us~a~ly a continuous process is to be preferred to a batch-wise process when a large-scale industrial production is concerned.
It is therefore an object of the invention to provide a process for the production of sintered bauxite spheres comprising steps all of which may be performed continuously.
Since any crushing of the bauxite spheres by ~:~ their use as fracture propping agents involves an im-paired permeability of the propped fracture it is desired to obtain a strength of spheres corresponding to an crushing loss even lower that the results obtained according to said German Offenlegungsschrift 29 21 336.
Consequently it is an other object o~ the inven-tion to provide a process resulting in bauxite spheres havlng a crushing 1QSS measured by the below defined method of les~ that S%.
In the above prior art process using an intensive mixer the possibilities are rather limited for control-ling the granulometry of the product, e.g. because a certain minimum mixing intensity will always be necessa-ry to secure homogeneity of the individual particles.
This means that a product having a very narrow particle size distribution, as is often required for propping .
3, ri~
agents, can only be prepared by simultaneous product.ion of a substantial amount of partlcles being too small or : too large, which necessitates extensivé sieving opera-tions and impairs total process economy.
Therefore it is a further object of the invention to provide a process which may easily be adapted to produce a major fraction of particles complying to varying requirements as to particle size distribution.
I The above objects are according to the invention achieved by a process for the production of sintered bauxite spheres having a particle size range from 0O4 to 2.5 mm, or a more narrow particle size range within said limits,suitable for use as fracture propping agent in oil wells, which process comprises the steps of (a) preparing an aqueous feed suspension comprising bauxite and a binder, (b) continuously atomizing said feed suspension into a layer of alxeady partly dried bauxite particles fluidized in a stream of drying air, (c) continuously recovering particles from said layer (d) continuously separating said recovered particles in oversize, unde.rsize and product fractions, making allowance for shrinkage in the subsequent sintering operation, (e) continuously recycling material selected :Erom the group cons:Lsting of undersize fractions, xelat.tve f:ine product fractions, ground product fractions and ground oversize fractions, to the layer o fluidized particles at a site at substantial distance, measured along the flow path of the par-ticles,from the site where said recovering of par-ticles takes place, and (f) drying and sintering the non-recycled product fractions by heating them at a temperature between 1200 and 1650C.
~ ', :
A method involving steps in principle correspon-ding to the above steps (b)-(e) is called ~luidized spray granulation and has been suggested ~or the granu-lation of various inorganic and organic products. Spray granulations has, howe~er, not been suggested for the manufacture of green proppant pellets and the suitabili-ty of the method for this specific purpose could in no way be predicted. In ~act it is rather surprising that a perfect spherical shape of the pellets ca~ be obtained, considering the very rapid evaporations o~ the atomized suspension in the process.
The crushing strength of the resulting sintered particles is to a substantial extent dependent on the homogenity of the green proppant pellets, and it is ; 15 also rather surprising that a spray granulation process is able to produce pellets which are supperior also in that respect.
In the present specification and in the accompany-ing claims "bauxite" is used in the widest sense of the word comprising also very low grade materials.
All steps of the process of the invention may be carried out in a continuous manner, which makes -the process especially attractive for large scale proppant manuEacture. It is a further advant~ge of khe process that -the prellminaxy drying necessary in prior art methods is disposed oE.
By using the steps (a)-(e) it :Ls possible to ob-tain pellets of spherical shape and of sufEicient strength for handling prior to and during the final drying and sintering process. After sintering these pellets form propping agents of higher strength than described in the prior art.
.
~ 17 2 ~ ~
DESCRIPTION OF THE DRAWING.
The invention is further elucidated with reference to the drawing, which is a schematic flow sheet illu-strating an embodiment of the process.
S DESCRIPTION OF THE INVENTION.
On the drawing a feed tank is designatPd 1. In this tank an aqueous feed suspension comprising bauxite and a binder is prepared. Preferably the feed contains 40-60, more preferably approximately 50 t % by weight bauxite (as defined abov'e~ and preferably 0.25-5, more preferably 0.5-2.5, % by weight binder. The bauxite should preferably have a particle size below 20 micron which îs conveniently achieved by a wet grinding process which is less energy consuming than dry milling prescribed in connection with some of the prior art processes.
The preferred binders are polyvinyl aceta~e, polyvinyl alcohol, methylcellulose, dextrin and molasses.
The function of the binder is to provide green 20 1 strenyth to the pellets until the sinterlng thereo~.
During the sintering most of the binders comming lnto consideration will decompose.This means ~hat ~ relakively h:Lyh amount Oe binder will impair the str~n~th Oe the e inal sintexed product, for which reason blnders are preEerred ~hich exhibi-t ~ sueficient temporary binding ahility even when used in small amounts.
Also further auxiliary agents may be added to the feed, such as dispersing agents, e.g~ ammonium citrateO
From the tank 1 the feed is led to a pump 2 feeding atomizing nozzles 3 arranged in a fluidized bed unit 4.
: , .' ' , . : , ,:
1~72~37.
:~ Between the feed tank 1 and the nozzles 3 may be inserted a grinding mill and/or a sieve tnot shown), to prevent that too coarse particles reach the nozzles and the fluid bed.
The atomizing nozzles 3 are pressure nozzles o~
conventional design~ or two-fluid nozzles. The design of such nozzles is well known e.g. from K. Masters:
''Spray Drying Handbook", John Wiley and Sons, New York ` ~1979).
The fluid bed unit 4 is of conventional desig~
Ias described in e.g. US patent specification 3 533 829 and in British patent specification 1 401 303 In the illustrated~em~odiment a fluidized par-ticle layer 5 is supported by a perforated plate 6 through which hot fluidizing gas is flowing. Said hot gas is introduced in the bottom part of the fluid bed unit by means of a fan 7 and an air heater 8.
The distance from the atomizing nozzles 3 to the ~erforated plate 6 is adjustable and the nozzles 20 1 are pr~ferably possitioned a rather short distance ¦above the surface of the fluidized particle layer 5.
The exact position of the nozzles will in each indivi-ldual case be fixed with due regard to the fact that too ! long distance from the nozzles to the surface of the fluidized layer causesundesired dus-t formation, because the atomized feed droplets will be dried to -too high an extent, before they reach the fluidized layer, whi].e a too short distanae on the other hand results in for-mation of irregular and too coarse particles. Therefore, the position of the nozzles is adjusted on the basis of analyses of powder taken out from the fluid bed unit.
The v~locity of the fluidizing and drying air passing the layer 5 is preferably 0 T 9-1.5 m/sec.
and the height of the fluidized particle layer will ty-.` ' ' . .
: , ' , , 3~
pically be 20-~0 cm.
The temperature oE the drying- and 1uldiziny air when introduced at -the botkom part of the fluid bed unit - 4 will preferably be 250-650 C, more preferably 400-600C.
When leaving the fluid bed unit the tempera-ture of said air is preferably below 100C, more preerably - approximately 70C.
- From the fluid bed unit the ai~ entraining dust consisting primarily of fine bauxite particles are led to a collector means 9, which may for instance be an electrostatic precipitator, a cyclone, a bag filter or a wet scrubber or a combination thereof.
Particles recovered in the collector means 9 may be recycled to the feed tank 1 and/or to the fluidized bed unit 4. It has turned out that the fine paxticles collected in 9 are very suitable for being recycled as seed particles to the fluidized bed due to their uniform spheroidal shape, and in this respect they are supperior to other seed particles obtained by grinding as explained below.
It is essential tha-t -the fluid bed unit 4 is designed to give a long and uni~orm residence time or the particles to obtain a desired particle ~.Lze distri~
25 jbu-tion and the des.ired spherical shape o~ the procluct.
Therefore, the ~low of particles ln the fluidizcd layer shoul.d be o~ the type conventionally termecl plug Elow, which is a ~low pattern wherein very li-ttle back mixiny takes place. Thereby an equal treatment of all particles is secured.
In a fluidized particle layer plug flow of the particles may be obtained by various measures. In the embodiment shown on the drawing the desired flow pattern is obtained by introducing powder particles serving as seeds or nuclei through a powder inlet 10 in one end of .,. ' ., ~ .
,.
.~,. .
3 ~
the fluid bed uni-t 4 and removing particles from the fluidized layer 5 through an outlet 11 situated at the opposite end o~ the ~luid bed unit. Alternatively - plug flow may be obtained by using guide walls in ~he fluid bed as is well known in the art.
The seed or nuclei particles introduced through powder inlet 10 consist of rec~cled material as will be explained a~ove and further elucidated below.
I Alternatively to the illustrated embodiment the 10 ~fluid bed unit may comprise two or several compartments in which different conditions prevail as to fluidizing air velocity, temperature and slurry feeding conditions ~Such fluid bed units having more than one compartment are well known in the art, and may e.g. have a circular perforated plate and radian partitions preventing back mixing.
Through the powder outle-t 11 is withdrawn a pow-der having a moisture content of 1-5~ which powder via a rotary valve 12 is conducted to a sieving unit 13 wherein it is separated into three or more fractions, viz. an oversize fraction, one or more product fractions - (in the embodiment shown: two fractions) and an under-- size fraction.
The oversize ;fraction is conductecl to a grind:Lny unit comprising a mill 14 and a ~ieve 15 which may possibly be comhi.ned. Oversize makerlal are recycled from the sieve 15 -to the miLI. 14 and fractions having preferably a slze of app. 0.5 mm are, in the embodiment shown, led to the powder inlet 10 of the fluid bed unit together with the fine fraction. In case the quantity of material of these two fractions, together with material collected in 9, is not sufficient to form seed or nuclei material for the fluid bed, a part of the product fraction or of one of the produc~ ~ractions may be added thereto as indicated by the dotted line in the .
:;
. "
., .
lower part of the drawing. A part o or the total amount of recycled product fraction may be ground before being introduced to the fluid bed, as indicated on the drawing. Qn the other hand, if the amount of material in the oversize fraction together with the undersize fraction is higher than what is required to supplement seed or nuclei material, a part thereof may be added to the feed tank 1, as illustrated by the dotted line in the left upperpart of the drawing.
10 j Non-recycled product fraction or fractions are led to a drying oven 16 wherein residual moisture and organic additives are evaporated and thereafter to a kiln 17, e.g. a rotary kiln, wherein the particles are !sintered to form high strength spheres suitable as prop-ping agents. The firing process taking place in the kiln 17 is conducted under the same conditions as those used in the prior art processes in which an agglomeration has ~een performed in a mixing apparatus.
; The size limits for the product fractions separa-ted in the sieving unit 13 must be fixed with due regard to the fact that in the s~bsequent firing pro-cess in the kiln 17 a substantial shrinkage takes - place. The extent of this shrinkage depends on the ori-gin of the original bauxite and may typlcally clmount to app. 25% on linear basis.
¦ As it appears the process may be p~rformed on a continuous basis and it ls very suitable for being ; automatically controlled using a rninirnurn of manpower.
As mentioned above the resulting propping agent !~ 30 has higher density and higher crushing strength than obtained in the embodiment examples of the above men-tioned German application. The crush~g strength is evalu-ated by a method in which the fraction between app. 600 microns and app. 700 microns is placed in a 1 5/8 inch diameter steel cylinder, and pressuré is applied to the ~, ' , .
:. . . ..
;' .. . .
~ ~ ~72~3~
: 10 sample through a plunyer fitting the -top o~ -the cylirlder according to the following schedule: 1 minute to 700 kg/cm2, 3 minutes hold at th.is pressure and 1 mlnute down to 0 pressure. Afterwards the amoun-t o material having a particle size below 600 microns is measured and expressed as % of the total amount. The result ls recorded as the weight ~ crushing loss.
The inven-tion is further elucidated by means of the following embodiment example.
10 Example 1 The process is carried out in a plant correspon-ding to the one illustrated on the drawing.
In the feed tank a feed suspension is prepared from water, fresh bauxite, recycled bauxite dust from 15 the collector unit and the below indicated auxiliary agents in amounts giving a total solids content of the feed~suspension of app. 50% by weight, which solids con-sist o, ca.93% bauxite, 1% polyvinylalkohol and.0,3~ ammo-nium citrate. This feed is in an amount of 4000 kg/hour atomized through the pressure nozzles 3 in a fluid bed unit in principle designed as shown on the drawing and having a fluidizing area oE 3 m2.
The velocity of the Eluidi.zing air is 1.2 m/sec, - and the inlet tempera-ture o the alr :Ls 550C while the outlet temperature is 70C. Recycled mater:La:l lntroduced : through the powcler inlet 10 amount~ to 1700 kg/hour. The height of the fluidized particle layer 5 is app. 35 cm.
The average residence time of the particles in the fluidi~ed layer may under these conditions be estimated to 15 minutes.
. Through the outlet 11 material is withdrawn in a quanti~y of 3400 kg/hour, which by sieving is sepa-rated in an oversize fraction having a particle si.ze above 2.1 mm (50 kg/hour), a coarse product fraction ', ' '
2~7 having a particle size between 1.2 and 2.1 mm (300 kg/
hour), a fine product fraction having a particle size between 0.6 and 1.2 mm (2450 kg/hour) and an undersize fraction having a parti~le size below 0.6 mm ~600 kg/
hour).
In the collector unit 9 which is a bag ilter 300 kg/hour entrained particles are collected and re-cycled to the feed tank l.
The total amount of the oversize fraction togethex with 400 kg/hour o the ine product fraction is ground in a grinding unit having a sieve of mesh size 3~U mi-crons,and together with the undersize fraction led to the fluid bed unit as seed or nuclei particles. 650 kg/
hour fine product fraction is recycled to inlet 10 with-out prior grunding.
The remaining material from the product fractionsis led through an oven in which the remaining moisture and organic additions ~app. totally 4% by weight) are removed and afterwards the sintering is perormed in a rotary kiln at a temperature of app. 1500C. The re-sidence time of the particles at this tempera-ture i5 ,~
app. 10 minutes.
The sintered particles is subject to a ~urther sieving operation to assure thak substantially all the 25 product has a particle size between 0.4 and 1.5 mm. The sphericity of the particles is excellent ancl their den-sity app. 3.8 g/cm3. q'he crushiny strength according to the~above methocl is 1.5% by weight, for which reason the `~ product must be regarded as being excellently suitable ~ 30 as a propping agent.
;.~.
.~
Example 2 In this embodiment the process is performed in a plant which only departs from the one used in Example ; 1 by having a sieving unit 13 which separates the par-'''.
,~'..
.
' , ~v .
ticles in only three frackions (viz. an oversize frac~
tion, a product ~raction and an undersize frac-tion) and by having a collector means 9 compris ng a cyclone collecting particles coarser than app. 100 microns and a 'wet scrubber collecting the finer particles as an aqueous Islurry.
! Also in this embodiment the total solids content 'of the feed suspension is app. 50% by weight and the quantity atomized is 4000 kg/hour.
10 ' Inlet air temperature is 530C and the outlet air temperature 68C.
,I That part of the material recycled as seed to the powder inlet 10 which consists of the undersize ,fraction, the ground oversize fraction and a part of 15 Ithe product fraction (ground) amounts to 300 kg/hour.
As in Example 1 the fluidizing air velocity is 1.2 m/sec. and the height of the fluidized layer is app.
35 cm. The average residence time is app. 20 minutes.
The material withdrawn from the fluid bed through 11 amounts to app. 2100 kg/hour and is let to the sieving unit 13 having two screens of mesh width 1.5 and 0.6 mm. resp. Thereby is obtained 30 kg/hour oversize fraction, 2030 kg/hour product fraction and 40 kg/hour undersize fraction.
. , 25 , 230 kgyhour of the product fraction is together ,with the oversize frac-tion cJround to a partLcle slze less than 600 microns ancl recycled together wlth the under-size ~raction as mentioned above,.
, In the above mentioned cyclone 100 kg/hour par-; 30 ticles having a size above 100 microns are collected and recycled to fluid bed inlet 10, while in the wet ~ scrubber connected to the cyclone 200 kg/hour particles ,, of an average size below 100 microns are collected and ' recycled as a slurry to the feed tank 1.
:' .
:;
:
~" ~, r;! ~ f3 ~3 r~
. 13 The product fraction not recycled which amoun-ts to 1800 kg/hour is dryed and sintered as descrlbed in Example 1. The crushing strength is 1.7% by weight and the density F 3-8 g/cm .
~'' .
`
. ., , ., ; .,:
. ~,. .
. .
'', . .
hour), a fine product fraction having a particle size between 0.6 and 1.2 mm (2450 kg/hour) and an undersize fraction having a parti~le size below 0.6 mm ~600 kg/
hour).
In the collector unit 9 which is a bag ilter 300 kg/hour entrained particles are collected and re-cycled to the feed tank l.
The total amount of the oversize fraction togethex with 400 kg/hour o the ine product fraction is ground in a grinding unit having a sieve of mesh size 3~U mi-crons,and together with the undersize fraction led to the fluid bed unit as seed or nuclei particles. 650 kg/
hour fine product fraction is recycled to inlet 10 with-out prior grunding.
The remaining material from the product fractionsis led through an oven in which the remaining moisture and organic additions ~app. totally 4% by weight) are removed and afterwards the sintering is perormed in a rotary kiln at a temperature of app. 1500C. The re-sidence time of the particles at this tempera-ture i5 ,~
app. 10 minutes.
The sintered particles is subject to a ~urther sieving operation to assure thak substantially all the 25 product has a particle size between 0.4 and 1.5 mm. The sphericity of the particles is excellent ancl their den-sity app. 3.8 g/cm3. q'he crushiny strength according to the~above methocl is 1.5% by weight, for which reason the `~ product must be regarded as being excellently suitable ~ 30 as a propping agent.
;.~.
.~
Example 2 In this embodiment the process is performed in a plant which only departs from the one used in Example ; 1 by having a sieving unit 13 which separates the par-'''.
,~'..
.
' , ~v .
ticles in only three frackions (viz. an oversize frac~
tion, a product ~raction and an undersize frac-tion) and by having a collector means 9 compris ng a cyclone collecting particles coarser than app. 100 microns and a 'wet scrubber collecting the finer particles as an aqueous Islurry.
! Also in this embodiment the total solids content 'of the feed suspension is app. 50% by weight and the quantity atomized is 4000 kg/hour.
10 ' Inlet air temperature is 530C and the outlet air temperature 68C.
,I That part of the material recycled as seed to the powder inlet 10 which consists of the undersize ,fraction, the ground oversize fraction and a part of 15 Ithe product fraction (ground) amounts to 300 kg/hour.
As in Example 1 the fluidizing air velocity is 1.2 m/sec. and the height of the fluidized layer is app.
35 cm. The average residence time is app. 20 minutes.
The material withdrawn from the fluid bed through 11 amounts to app. 2100 kg/hour and is let to the sieving unit 13 having two screens of mesh width 1.5 and 0.6 mm. resp. Thereby is obtained 30 kg/hour oversize fraction, 2030 kg/hour product fraction and 40 kg/hour undersize fraction.
. , 25 , 230 kgyhour of the product fraction is together ,with the oversize frac-tion cJround to a partLcle slze less than 600 microns ancl recycled together wlth the under-size ~raction as mentioned above,.
, In the above mentioned cyclone 100 kg/hour par-; 30 ticles having a size above 100 microns are collected and recycled to fluid bed inlet 10, while in the wet ~ scrubber connected to the cyclone 200 kg/hour particles ,, of an average size below 100 microns are collected and ' recycled as a slurry to the feed tank 1.
:' .
:;
:
~" ~, r;! ~ f3 ~3 r~
. 13 The product fraction not recycled which amoun-ts to 1800 kg/hour is dryed and sintered as descrlbed in Example 1. The crushing strength is 1.7% by weight and the density F 3-8 g/cm .
~'' .
`
. ., , ., ; .,:
. ~,. .
. .
'', . .
Claims (7)
1. A process for the production of sintered bau-xite spheres having a particle size range of from 0,4 to 2.5 mm or a more narrow particle size range within said limits, suitable for use as fracture propping agent in oil wells, comprising the steps of (a) preparing an aqueous feed suspension comprising bau-xite and a binder, (b) continuously atomizing said feed suspension into a layer of already partly dried bauxite particles fluidized in a stream of drying air, (c) continuously recovering particles from said layer (d) continuously separating said recovered particles in oversize, undersize and product fractions making allowance for shrinkage in the subsequent sintered operation, (e) continuously recycling material selected from the group consisting of undersize fractions, relative fine product fractions,ground product fractions and ground oversize fractions, to the layer of fluidized particles at a site at substantial distance, measured along the flow path of the particles,from the site where said recovering of particles takes place, and (f) drying and sintering the non-recycled product fractions by heating them at a temperature between 1200 and 1650°C.
2. A process according to claim 1, wherein the aqueous feed suspension contains 40-60% by weight bau-xite having a particle size below 20 micron and 0.25-5%
by weight binder selected from the group consisting of polyvinyl alcohol, polyvinyl acetate, methyl cellulose, dextrine and molasses.
by weight binder selected from the group consisting of polyvinyl alcohol, polyvinyl acetate, methyl cellulose, dextrine and molasses.
3. A process accordring to claim 1, wherein the material recycled in step (e) has been ground to a controlled particle size distribution.
4. A process according to claim 1, wherein the stream of drying air fluidizing the bauxite particles has a velocity of 0.5-1.5 m/s.
5. Sintered bauxite spheres produced by a process according to claim 1 and having less than 5% by weight crushing loss, measured as defined herein.
6. A process for the production of binder-contai-ning bauxite spheres for use in the manufacture of sin tered bauxite spheres comprising (a) preparing an aqueous feed suspension comprising bauxite and a binder, (b) continuously atomizing said feed suspension into a layer of already partly dried bauxite particles fluidized in a stream of drying air, (c) continuously recovering particles from said layer, (d) continuously separating said recovered particles in oversize, undersize and product fractions, and (e) continuously recycling material selected from the group consisting of undersize fractions, relative fine product fractions, ground product fractions and ground oversize fractions, to the layer of fluidized particles at a site at substantial distance, measured along the flow path of the particles,from the site where said recovering of particles takes place.
7. Binder-containing bauxite spheres produced by a process according to claim 6.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB80/22175 | 1980-07-07 | ||
| GB8022175A GB2079261B (en) | 1980-07-07 | 1980-07-07 | Process for the production of sintered bauxite spheres |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1172837A true CA1172837A (en) | 1984-08-21 |
Family
ID=10514584
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000381189A Expired CA1172837A (en) | 1980-07-07 | 1981-07-06 | Process for the production of sintered bauxite spheres |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA1172837A (en) |
| CH (1) | CH647689A5 (en) |
| DE (1) | DE3126568A1 (en) |
| FR (1) | FR2486930B1 (en) |
| GB (1) | GB2079261B (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7036591B2 (en) | 2002-10-10 | 2006-05-02 | Carbo Ceramics Inc. | Low density proppant |
| US7387752B2 (en) | 2004-07-09 | 2008-06-17 | Carbo Ceramics Inc. | Method for producing solid ceramic particles using a spray drying process |
| US7654323B2 (en) | 2005-09-21 | 2010-02-02 | Imerys | Electrofused proppant, method of manufacture, and method of use |
| US7678723B2 (en) | 2004-09-14 | 2010-03-16 | Carbo Ceramics, Inc. | Sintered spherical pellets |
| US7721804B2 (en) | 2007-07-06 | 2010-05-25 | Carbo Ceramics Inc. | Proppants for gel clean-up |
| US7828998B2 (en) | 2006-07-11 | 2010-11-09 | Carbo Ceramics, Inc. | Material having a controlled microstructure, core-shell macrostructure, and method for its fabrication |
| US8063000B2 (en) | 2006-08-30 | 2011-11-22 | Carbo Ceramics Inc. | Low bulk density proppant and methods for producing the same |
| US8216675B2 (en) | 2005-03-01 | 2012-07-10 | Carbo Ceramics Inc. | Methods for producing sintered particles from a slurry of an alumina-containing raw material |
| US8562900B2 (en) | 2006-09-01 | 2013-10-22 | Imerys | Method of manufacturing and using rod-shaped proppants and anti-flowback additives |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DK155781C (en) * | 1982-01-07 | 1989-10-09 | Niro Atomizer As | PROCEDURE FOR MANUFACTURING SINTERED TASTING BULBS OF BAUXITE OR BAUXIT SUBSTANCED BERGART, AND MEANS OF EXERCISING THE PROCEDURE |
| DE3223024A1 (en) * | 1982-06-19 | 1983-12-22 | Battelle-Institut E.V., 6000 Frankfurt | METHOD FOR PRODUCING A SUPPORT |
| NL8304305A (en) * | 1983-01-03 | 1984-08-01 | Chevron Res | MATERIAL COMPOSITION OF SINTERED BAUXITE FOR A GRINDER PACK OR PRE-PREPARED PACKAGE AT A STEAM INJECTION WORK. |
| EP0277730B1 (en) * | 1987-01-29 | 1992-05-06 | Sumitomo Chemical Company, Limited | Process for the preparation of alumina |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL136037C (en) * | 1965-08-27 | |||
| JPS5116442A (en) * | 1974-07-31 | 1976-02-09 | Akiko Hirata | Chikudenchino denkaiekijohatsuboshihoho |
| CA1045027A (en) * | 1975-09-26 | 1978-12-26 | Walter A. Hedden | Hydraulic fracturing method using sintered bauxite propping agent |
| CA1117987A (en) * | 1978-12-13 | 1982-02-09 | Robert J. Seider | Sintered high density spherical ceramic pellets for gas and oil well proppants and their process of manufacture |
-
1980
- 1980-07-07 GB GB8022175A patent/GB2079261B/en not_active Expired
-
1981
- 1981-06-30 CH CH4308/81A patent/CH647689A5/en not_active IP Right Cessation
- 1981-07-06 CA CA000381189A patent/CA1172837A/en not_active Expired
- 1981-07-06 DE DE3126568A patent/DE3126568A1/en not_active Withdrawn
- 1981-07-07 FR FR8113310A patent/FR2486930B1/en not_active Expired
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7036591B2 (en) | 2002-10-10 | 2006-05-02 | Carbo Ceramics Inc. | Low density proppant |
| US7387752B2 (en) | 2004-07-09 | 2008-06-17 | Carbo Ceramics Inc. | Method for producing solid ceramic particles using a spray drying process |
| US7678723B2 (en) | 2004-09-14 | 2010-03-16 | Carbo Ceramics, Inc. | Sintered spherical pellets |
| US7825053B2 (en) | 2004-09-14 | 2010-11-02 | Carbo Ceramics Inc. | Sintered spherical pellets |
| US8216675B2 (en) | 2005-03-01 | 2012-07-10 | Carbo Ceramics Inc. | Methods for producing sintered particles from a slurry of an alumina-containing raw material |
| US7654323B2 (en) | 2005-09-21 | 2010-02-02 | Imerys | Electrofused proppant, method of manufacture, and method of use |
| US7828998B2 (en) | 2006-07-11 | 2010-11-09 | Carbo Ceramics, Inc. | Material having a controlled microstructure, core-shell macrostructure, and method for its fabrication |
| US8063000B2 (en) | 2006-08-30 | 2011-11-22 | Carbo Ceramics Inc. | Low bulk density proppant and methods for producing the same |
| US8562900B2 (en) | 2006-09-01 | 2013-10-22 | Imerys | Method of manufacturing and using rod-shaped proppants and anti-flowback additives |
| US7721804B2 (en) | 2007-07-06 | 2010-05-25 | Carbo Ceramics Inc. | Proppants for gel clean-up |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2079261B (en) | 1983-06-08 |
| CH647689A5 (en) | 1985-02-15 |
| FR2486930B1 (en) | 1986-01-24 |
| DE3126568A1 (en) | 1982-06-16 |
| FR2486930A1 (en) | 1982-01-22 |
| GB2079261A (en) | 1982-01-20 |
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