CA2014954A1

CA2014954A1 - Process and apparatus for the treatment of brines and contaminated mineral salts or mixtures thereof

Info

Publication number: CA2014954A1
Application number: CA002014954A
Authority: CA
Inventors: Charles Zampieri
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-04-24
Filing date: 1990-04-19
Publication date: 1990-10-24
Also published as: DE3913482A1; DE3913482C2; WO1990012756A1; EP0394607B1; AU5541090A; PT91200A; PT91200B; DE59000098D1; EP0394607A1; US5122233A; YU201290A

Abstract

Abstract of the Disclosure Process and apparatus for the treatment of brines and contaminated mineral salts or mixtures thereof The invention concerns a process for the treatment of brines and contaminated mineral salts or mixtures there-of, comprising the steps of (a) substantially separating organic components from the process mixture, (b) subjecting the resulting mixture to a vacuum evapo-ration step, (c) thermally treating the partially dried mineral salts or mixtures thereof at an elevated temperature and thereafter obtaining pure dry mineral salts or mix-tures thereof, (d) condensing the vapour of the vacuum evaporation step and subjecting said vapour to a reverse osmosis step, and (e) obtaining from said reverse osmosis step pure water, as well as an apparatus for carrying out said process, substantially comprising a means 1 for separating orga-nic components from the process mixture, a vacuum evapo-ration means 4 in order to partially dry said mineral salts or mixtures thereof, a means 5 for thermal treat-ment of the partially dried mineral salts or mixtures thereof from the vacuum evaporation means 4, a condenser 7 for condensing the humid vapours from the vacuum eva-poration means 4 and a means 9 for reverse osmosis treatment of the condensate as well as suitable con-veying devices between said parts of the apparatus.

Description

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D e s c r i p t i o n The invention concerns a process as well as an apparatus for the treatment of brines and contaminated mineral salts or mixtures thereof. In ?articular, the invention concerns a process and an apparatus by means of which supersaturated brines or contaminated mineral salts or mixtures thereof can be freed of such contaminations which occur during preparation and curing of animal hides with mineral salts, especially with sodium chlo-ride, before the manufacture of leather. Such contamina-tions can, for example, be animal dung and urine, re-mains of blood, skin and flesh, as well as hair.

The hide removQd from the animal carcass, the so-called "green hide", is very rarely tanned immediately after slaughtering and processed to leather in the leather factory. It ta]ces time, often wee~s or months, to col-lect major batches of hides, to sort them by weight and quality categories, to compile the parcels and to trans-port them fro~ the slaughterhouse or place of prepara-tion, respectively, to the leather factory. However, owing to their protein structure, uncured and untanned hides left in the natural wet state are often infested by putrefactive bacteria and mould which find optimal conditions for reproduction in the damp raw hides often ~,cposed to warm weather. In order to prevent infestation with and reproduction of putrefactive bacteria on the raw hides these must be cured.

Even thougll other curing processes have been proposed for ecological reasons, only curing with sodium chloride has really been successful. Moreover, only curing with sodium chloride has so far fulfilled the two essential conditions required of such curing: Firstly, curing must result in a'lasting bactericidal effect and thus preven-:

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tion of putrefaction and mould infestation on the rawhide. Secondly, it must be possible to process the hide to faultless leather after curing and extended storage, i.e. to fully undo the curing. Both requirements are optimally met ~y the curing by means o- sodium chloride.

In detail, curing of raw hides hy means of sodium chlo-ride is effected in such a way that the hides are pre-cleaned superficially and then sprin};led with solid sodium chloride containing common denaturants such as naphthalene or similar organic compounds or are soa]ced in a saturated or supersaturated brine for up to 24 hours. ~1hen the hides are stac~ed or folded into pac~-ets, either solid salt comes off the salted parts or saturated or supersaturated brine drips from the hides.
In the past, it ~as customary to let off the solid or dissolved quantities of salt thus obtained straight into sewage canals or into-the environment, which has result-ed in an unacceptable pollution of lalces and rivers with sodium chloride in high concentrations.

In addition, the curing salt is dissolved by steeping the hides in water hefore they are tanned or processed to leather, respectively. The water left over from this step which contains salt in high concen~rations is also let off into the se~rage canals or immediately into the rivers. This, too, r~sults in an unacceptable increase of the salt concentration in natural waters.

Another disadvantag2 of the traditional disposal of the salt quantities resulting from the curing of raw hides is the fact that the sodium chlorid~, which has become incr~asingly expensive, cannot be recycled. Therefore, the purchas~ cost for mineral salt is fully added to the price of the cured hides.

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A process and a device, respectively, for treating con-taminated mineral salts or mix~ures thereof is described in the parallel German patent application P 3835418.7 submittec1 on October 17, 1988. In this patent applica-tion, there is d2scribed the tr_atment of contaminated mineral salts or mi:ctures thereof in a heatable retort by continuous or step-b~-step heating to over 350C for a period of at least four minutes. The gases and vapours developing during this heating ?rocess are let off into the atmosphere. This retort is preferably shaped as an uprigllt cylindrical tube and can be heated over its en-tire lengt~ to the r_quired process temperature by mQanS
of a heating spiral. The serious disadvantage of this process or the devic_ descrihed in the application, res?_ctively, is the requirQment that only precleaned mineral salts which are essentially free of solid conta-minations can be used. Organic components caused by the process are not separated. I'oreover, there is a risk with this device that the increasingly thickening salt layer is deposited on the heated inner walls of the retort, ma~cing the heat transmission more difficult and, as the thickness of the layer increases, encumbering and eventually preventing the penetration of gases and salt inside the r~tort. Other processes known from the prior art are carried out at treatment temperatures which are so low that the salts thus obtained are not free of germs owing to the comparatively low temperaturss.

It is the object of this invention to overcome the dis-advantases of ?revious means or the processes carried ! out therswith, respectively. The new apparatus according to the invention is to provide a means where clogging by deposition and the resulting decreasing effectiveness of a means for the recycling and purefying treatment of brin~s and mineral salts during extended continuous or intermittedd operation can be avoided.

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i~ot only for r~asons of keeping environment pollution low, but also for cost reasons it ~as further desirable to ~rovide a process and an apparatus which does not only achieve desalinisation of the process water obtain-ed during the dressing OL raw hides, but also makes it possible to process brines and the mineral salts or mi.ctures thereoF containinq said contaminations in such a way that they become free of contaminations and can be used again for the repeated process of curing.

It was a further object of the present invention to pro-vide the salts obtained on he occasion as pourable gra-nulates having a granule size which can be adapted ac-cordinq to the relevant recuirements o the users.

It was an additional object of the invention to process the contaminated mineral salts in such a way that the resultin~ salt products are free of germs.

Finally, it -~as also an object of the invention to pro-vide a process suitable for processing brines and con-taminated mineral salts or mixtures thereof which can be carried out ~ontinuously or intermittQntly in an energy saving manner and in sim21e designs. The products of such a proc3ss are not only to be salts of a quality corresponding to the requirements of the users but also water of the highest possihle purity which can be chan-nelled once more into the process water or drin~ing water cycle. It is the intention of such a process to recover all the process products in a high quality and thus to be able to use them repeatedly in an economi-cally meaningful manner.

It has now been found that the above-named technical problems can be solved by the process indicated in pa-tent claim 1 and by providing the device indicated in : ~

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patent claim ~3. Advantageous embodiments and further developments of the inven~ion result from the dependent claims.

The invention concerns a process for the treatment of brines and contaminated mineral salts and mixtures thereof comprising the steps of (a) substantially separating organic components from the process mixture, (b) subjecting the resulting mixture to a vaccum evapo-ration step, (c) thermally treating the partially dried mineral salts or mixtures thereof at an elevated temperature and ~hereafter obtaining pure dry mineral salts or mix-tures thereof, (d) condensing the vapour resulting from the vacuum eva-poration step and subjecting said vapour to a re-verse osmosis step and (e) obtaining from said reverse osmosis step pure water.
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In addition, the invention concerns an apparatus for tr~ating brines or contaminated mineral salts or mix-tures thereof comprising (a) a means 1 for separating organic components from the process mixture, (b) a means 4 for vacuum evaporation in order to par-tially dry the mineral salts or mixtures thereof, ' ', '. . : '` . . : , `' : : ~ ' ~ ' ' : :

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(c) a m~ans 5 for thermal treatment of the partially clried mineral salts or mixtures thereof resulting from said means 4 for vaccum evaporation, (d) a condenser 7 for condensing the humid vapours re-sulting from said meanc 4 for vacuum evaporation and (e) a means 9 for reverse osmosis treatment of the con-densate resulting from step (d), as well as (f) conveyin~ means 12, 71, 93 connecting in series said means 1 for separating organic components, said means ~ for vacuum evapora~ion, said condens~r 7 and said means 9 for reverse osmosis treatment, as well as conveyins means al for connecting said vacuum eva~oration means 4 with said means S for the ther-mal treatment of said salts.

Brines treated in the process according to the invention are aqueous solutions containing mineral salts and pri-marily sodium chloride and result from the curing treat-ment of raw hicles or the steeping of cured hides before tanning. The salt content of these aqueous solutions can be under the saturation point of the solution under con-ditions of application.lIowever, it is also possible to treat supersaturated aqueous brines according to the process of the present invention. For the purposes of the present invention mineral salts are understood to be all compdunds of metal cations with acid radicals of mineral acids. Mixtures of such mineral salts are also comprised by the present invention. Preferably, the term "mineral salts" is understood to comprise such salts as used in the curing treatment of raw hides. Especially sodium chloride is one of those salts; however, the invention is not limited to the treatment of sodium chloride o~ salt mixtures or brines containing sodium chloride, even if it is illustrated using this especial-ly preferred embodiment.

In th2 first st~p of the process according to the inven-tion fsr treatins brines, contaminated mineral salts and mi~tures thereof organic components are substantially separated from the process mixture. Such organic compo-nents are mainly animal recrements left over from the slaughtering process such as animal dung and urine, remainders of f lesh and slcin as ~ell as hairs. This first process step is based on the realisation that said recrements partially contain recoverable components which can he directed to~.Jards systematic reuse, to be used, for instance, as fodder. The most simple and eco-nomical separation from the brines or ~ineral salts or mixtures thereof, res?ectively, is effected in multi-pllase systems such as flotation, filtration, decantation and centrifugal systems. Flotation processes are pre-ferred for this purpose. In such a process, the brines or mineral salts or mixtures thereof, res?ectively, contaminated ~ith said organic components are fed to an aqueous flotation system by means of a suitable flota-tion agent in a manner which is known per se from the prior art. Flotation agents can l?referabl~ be FeC13 or siliceous earth. The temperatures are usually between 5 to 25C; room temperature is preferred. As a result of tlle effect of t~e flotation agents, the organic compo-nents float to the surface and can he slcimmed therefrom in tlle customar~ manner. Wllat remains are - sometimes supersaturated - salt solutions containing the undis-solved salt portions as a non floatable solid remaining at the bottom of the solution. According to other pre-ferred embodiments of the invention, filters, decanters or centrifuges can also be used instead of a flotation means.

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In a preferred embodiment of the process the muds con-taining floated or~anic components are then recycled for reuse, for instance as fodder. If necessary, they can be washed in order to remove the flotation agents. They are then clried in a manner which is known as such and pul-- verised to be used, for example, as a fodder additive.

In the next step of the process according to the inven-tion, the aqueous mi,~ture which is left over after sepa-ration of th~ organic comoonents and which may contain undissolved mineral salts as a non floatable solid re-maining at the hottom, is subjected to a vacuum evapora-tion step. For this purpose, the mixture is orefsrably fed into a closed vessel, for ins~ance an autoclave or ~such li'ce, wherein it can be moved by ~eans of the custo~ary agents, for instance stirred.

In a preferred embodimenL of th~ present invention the vacuum evaporation treatment of the aqueous solution or mixturs, res~ectively, is carried out in a ~ressure vessel which is ca?able of sustaining the pressure of this process step and, optionally ~and then preferably), controllable by a thermostat, said pr~ssure vessel hav-ing the shape of a cylinder ~ith a cone tapering side-ways attached to its lower end or the shape of a cone tapering downwards. The aqueous solution or mixture is fed to the inside of the vessel via suitable feeding lines, preferably nozzles, where it is exposed to an increased temperature and reduced pressure. The tempera-ture is appli~clto the outer wall of the pressure vessel by sources of h~at operating outside the vessel, prefer-ably a fuel liquid or a fuel gas rlowing in the thermo-stat casing. The vacuum is created by traditional vacuum pumps connected with the prsssure vessel by a tube going out at the top end of the vessel.

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Salt separated during the vacuum evaporation triclcles do~n into the vcssel and is removed intermittently or continuously - optionally by means of a loc~ chamber -and directed towards the following process steps. The special advantage of a loc!~ chamber for the removal of - ~hc salt is seen to be that continuous operation of the vacuum evaporation means undar unchanging vacuum condi-tions is possible while salt is nevertheless permanently withdrawn. Accordin~ to the invention, it is preferred to obtain comparatively large salt crystals, for example with a granular size of 0.2 to 0.3 mm so that said salt crystals are not carried along by the stream of vapour to cause problems during tha subsequent steps of treat-ing the liquid phase. In a s?ecially preferred embodi-ment of the process according to the invention this can be achieved by feeding the aqueous solution or mixture into th~ vessel through a line ending in an annular nozzle inside the v~ssel, said annular nozzle having an optional number, preferably, for example, six to eight, of indivic7ual nozzles for spray distribution of the solution or mi:-~ture, respectively, within the vessel.
This is conducive to an even distribution of the aqueous phase inside the vessel and thus a continuous evapora-tion process, which not only leads to a continuous stream of vapour at unchanging vacuum conditions, but also to the formation of even salt crystals. ~ithin certain limits, the size of the crystals can even be controlled by tha injection speed or injection pressure, respectively, the size of the noszles, the temperature inside the vessel, etc.

The vapour resulting from the evaporation step is drawn off through the tube going off at the top end of the pressure vessel, said tube forming the connection with the vacuum, pump or pumps, respectively. This tube is coolad by a cooling system connected to a cooling aggre-- 2 Q~ 3~

gate, preferably an intensive cooling system which runs in a helix-typ~ manner inside the vessel. The tempera-tures of the cooling system are betweQn 8 and 12C at the entry point (at the lower end of the tube in rela-tion to the dir ction of the vapour flo-r~ and 14 to 32C
at the exit point (at the uoper end of the tube in relation to the direction of the vapour flow). Thus, cooling preferably takes place b~ reverse flow cooling.
Owing to the intensive cooling system, ~hich is ~laced inside the vapour escape tube in a space-saving manner, complete condensation of the vapour is achieved.

In another preferred embodiment according to the inven-tion one or several vapour traps are positioned in the vapour escape tube be~ond the e~it from the 2ressure vessel and a certain distance thereafter, preferably after a bend in the tube, ~dhich can, for example, be simple obstacles projecting into the course of the va-pourO In a specially preferred way, the first obstacle is installed immediately beyond the exit of the vapour escape tube from the pressure vessel. Salt crystals which may have been carried along by the vapour are separated at this ~oint and drop bac~ into the pressure vessel so that the condensate is not contaminated later by larger quantities of salt carried along. Moreover, such vapour traos form an obstacle against a consider-able decrease of pressure; thus, the orocess pressure can be maintain~d more evenly.

At th~ lower end of the vapour escape tube the conden-sate is let out into a reservoir and removed continu-ously or intermittently.

In a preferred embodiment of the process according to the invention, the vacuum evaporation step is carried out at a pr~ssure in the range of 0.5 to 10 3 bar, èven 2 ~ c ~

more preferably, in the range between 10~1 and 10-2 bar.
The process temperatures are advantageously in the range between 20 to 50C, more preferably between 42 and 50C.
The advantase of concentrating the aqueous mixture by means of vacuum eva?oration in comparison with processes lcnown so far, for example treatment in a heated retort, must be seen in the fact that, by using the process according to the invention, a steam containing hardly any salts any more can be obtained in an energy-saving manner on the one hand, and mineral salts or mixtures thercof having a considerably reduced humidity content, preferably a maximum humidit~ conten, o~ 40 % and, even more prefera~ly, a maximum humidity content of 25 to 35 %, are obtained on the other hand. T~ere is no danger of clogging in the means or individual parts thereof or of a deterioration of the energy exploitation by salt layers encumbering heat transmission.

In another preferred embodiment of the process the aque-ous mixtures fed to the vacuum evaporation step are preheated by waste hea, occurring elsewhere in the pro-cess. For example, the warm air resulting from the thermal treatment of the salts described below can be used to heat the aqueous mi~ures to a temperature between 20 and 50C, preferably between 42 to 50CC, and to maintain such a te!nperature during the course of the vacuum evaporation step, i.e. to provide the necessary evaporation h~at. The energy saving increases the pro-fitability of the process.

In the most preferred case, the mineral salts or mix-tures thereof, respectivsly, ~hich are obtained as pro-ducts of the vacuum evaporation step and which are par-tially drisd consist almost sxclusively of sodium chlo-ride and, cf course, water. However, said sodium chlo-ride can be mix~d with other salts as well as small quantities of natural or process-caused contaminations, such as chlorides of other metals, bromides, iodides, carbonates, hydrogen carbonates, phosphates or sul~hates or other salts. In the nex~ step of the process accord-ing to the invention, the mineral salts or mi~tures thereof, respectively, are subjected to a thermal treat-ment at an elevated temperature. Preferably, mineral salts or mixtures thereof having a maximum humidity con-tent of of ~0 %, most preferably having a humidity content between 25 and 35 %, are subjected to the ther-mal treatment. This can be carried out by traditional means, for examDl~a a conveyor belt or a COnveyiQr spiral.
In a preferred embodiment OL th_ process according to tne invention the mineral salt or mixture ,hereof to be thermally treated is fed to the rotary ,ubular kiln by a stuffing conveyor means. Said means can for example consist of a cylinder having a supply nozzl~ or supply container on the side wheraill a stuffer can be moved manually or mechanically over a distance extending (in the direction OL the flow of the supplie~ salt) from a point in front of the lateral suppl~ nozzle to a point beyond said lateral supply nozzle. B-~ moving the s,uffer in the cylinder - while the sup?ly nozzle is closed - a certain quantity of salt is conveyed in the direction of the rotary tube and fed to a tube connected to the stuffing conveyor means, the open end of said tube extending to the reed opening of the rotary tube. After that, the stuffer is withdrawn. Suitable devices in the tubea, for ~xample a conus tapering in the flow direction of the mineral salt cr mixture thereof, respectively, can prevent the salt falling back. ~hen the stuffer has returned to the original position, the supply nozzle is opened so that additional salt can be supplied, which is then conveyed by the stuffer towards the rotary tube once the supply nozzle is closed again. T'ne a~vantage of this stuffing conveyor means is to be seen in the fact ;`.. " ' ` ~ :
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that salt conveyed in the direction of the tubular kiln does not clog the feed opening, if the conveying must be interrupted for some reason and the mineral salt or mixture thereof, respectively, absorbs humidity in the conveying means and sticks together when left standing for a longer period of time, for instance over night.
The stuffing conveyor means preferred according to the invention makes it possible to rQstart conveying the mineral salt or mixture thereof to the rotary tube without problems even after it has been left standing for a lcnger period of time.

In a special embodiment of the process the mineral salts or mixtures thereof obtained by the vacuum evaporation step can be united with additional salts of similar consistency, which are referred to as so-called waste salts from the operation. Said waste salts have a maximum water content of 40 % and are free of rough organic contaminations such as remainders of dung or urine, blood, flesh, skin and such like. Such salts can for instance be fed into a separate storage tank, there-in mixed with the salts obtained from the vacuum evapo-ration step and then be conveyed to the thermal treat-ment, or be conveyed immediately to the thermal treat-ment separately from the mineral salts or mixtures thereof.

It is true that the thermal treatment of the mineral salts or mixtures thereof, respectively, according to the invention can be carried out by any method known to the person skilled in the art from the prior art, as long as the object of the invention, namely to produce mineral salts of high purity and free of germs is achieved. However, it corresponds to a preferred process method to carry out the thermal treatment in a rotary tuhular ki'ln. The design and function of such a rotary ~.: , . .

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tubular kiln may be known to the person skilled in the art from the prior art. Advantageous and thereCore ~re-ferred is a rotary tubular ~iln having a diameter of or above 450 mm and a length of or above 1,500 mm.

The rotating sp2ed of such a ]ciln is preferably variable and can be adapted to the relevant process situation, for example to the water content of the mineral salts supplied or the speed in which the mineral salts are supplied and must, consequently, also be withdra~"n from the ~iiln. Preferably, the rotating speed varies in the range hetween 5 and 20 rotations/minute. Another prefer-red embodiment of the process is to su?~ly the mineral salts or mixtures thereof of the ?revious vacuum drying step to a rotary tubular lciln wllich is inclined down-wards in the direction of the flow of the salt at an angle (alpha) of 2 to 10, preferably 3 to 5. This ma];es it~?ossible to adjust the flow of the treated salt to the exit or the rotary tubular kiln which is adapt-able to the relevant process conditions also with regard to speed without having to provide costly devices inside the ~iln for this purpose.

It is further preferred according to the invention to charge the rotary tubular !iiln with hot gases in order to produce higher temperatures. These can be oxygen-free gases which are brought to the required process tempera-ture with the aid of suitable technical devices, for exam~le h~ating spirals or heat e:cchangers, and which are admixed with oxygen or gas mixtures containing oxy-gen. EIowever, the mcans for the process according to the invention is preferably charcJed with combustion gases and, even more preferably, with combustion gases from a gas-burner to which said combustion gases oxygen or oxy-genic gas mixtures, especially air, are admixed. It has turned out'to be especially preferable for thermal :'. ', :; : ~: :

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treat~ent of the partially dried mineral salts and mi~-tures thereof accorcling to the invention to charge the rotary tubular Xiln with combustion gases from a gas-burner of suitable size and a combustion output adapt-abl~ to this process sten and to admix to the stream of gas an amount of air corresponding to a surplus of 100 to 300 %, preferably 200 %, related ,o the amount of oxygen requir~d for the complete combustion of all re-maining organic components of the mineral salts. The amount necessary to adapt to the relevant ?rocess si-tuation can easily be determined by the person s]~illed in the art by measuring tlle o~;ygen concentration in the waste gases. This ensures that all orsanic components, especially micro-organisms such as bacteria and spores still contained in the mineral salt or mineral salt mixturQ, respectively, are invariably eliminated without residue under the process conditions and combusted to gases which are not harm,ul to the environment. Conse-quently, soot or to~ic gases resulting form an incom-plete combustion do not occur.

In accordance ~ith the invention, the thermal treatment of the mineral salts or mixtures thereof is carried out at an elevated temperature. The temperature is prefer-ably in the range of 140 to 500C, even more preferably between 300 to 400C. This temperature is reached at the hottest spot OL the '.ciln, which, as a rule, is at the tip of the flame of the gas-burner, andis also measured there. ~y carrying out the treatment in these preferred ranges it can be ensured that all organic components remaining in the salt or mixture thereof, respectively, are combusted completely and do not contain any micro-organisms thereafter which could cause damages to the ra~ hides if the salt is used again. In this respect, the process according to the invention is clearly supe-rior to the processes of the prior art. In addition, the :

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salt thus obtained is odourless and flat~less in colour, i.e. white.

As already pointed out above, the hot waste gases of this process step can not only be used to 2reheat the mineral salts or mixtures thereof, r~spectively, which are fed to the means for thermal treatment or the rotary tubular kiln, respectively. Rather, the hot waste gases can also be usect to preheat the substances employed in other process steæs of the ?resent process, for example to preheat the brine or the mineral salt or mixture thereof, respectively, for vacuum evaporation. It goes without saying that the surplus heat can also be used for non process-bound purposes. This further increases the profitability of the process of the invention, espe-cially if energy costs are at a high level.

In another preferred el~odim2nt of the process according to the invention, the mineral salt or the mixture there-of, respectively, is ground to the granule size desired by the users at the end of the thermal treatment or thereafter. In a preferred embodiment of the process the granule size can be < 0.1 mm to 0.6 mm and is especially pref~rred at 0.2 mm to 0.5 mm. Even though separate grinding in a grinder ~ositioned downstream is possible, it is preferred in accordance with the invention to grind the salts in a grinding chamber ?ositioned inside the rotary tubular kiln in front of the salt exit. Said cha~er is equipped with grinding balls which can be selectAd by the person skilled in the art in accordance with the process conditions and the desired granular size. Moreover, a sieve positioned in front of the exit can prevent salt granules or chunks exceeding the de-sired size from leaving the rotary tubular kiln. The salt thus obtained is pourable and can be reused without problems for curing raw hides.

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~1hen treating the process mixture, which has substan-tially been freed of organic components, by a vacuum evaporation step, steam is ob~ained in addition to the mineral salt or a mixture thereof, and said steam is expanded and fed to a condenser. It is inherent to the method that, at least in the less preferred embodiments of the process, it cannot be fully prevented at all times that small arnounts of salt are carried along which are then found in the condensate. Usually, the salt content is in the range of O.l to 5 g/1 of the conden-sate, preferably betw22n 0.5 to 2 g/l of the condensate.
In order to obtain actually pure, salt-~re~ water - as opposed to that obtained by the prior art - the conden-sate is subjected to a reverse osmosis in a subsequent proc~ss step.

The speed, the pressure and the temperature of the vacu-um evaporation st~p are pref2rably controlled in such a way that the condensat2 can be continuously subjected to reverse osmosis. Alternativel~, however, it is also possible to channel the condensate of the vacuum evapo-ration step and of the subs~quent condensation step first to a storage tank and and then to feed said con-densate to the reverse osmosis step..~ third, preferred possibility is seen in providing for both steps mention-ed above and to interpose the storage tank only if and when the immediate supply to the reverse osmosis step is not possible for capacity reasons because the obtained amount of condensate is high. It is a further advantage of the third alternative that the means for reverse osmosis can also be switched off for a short time, for instance for cleaning or for exchanging the membrane, without having to interrupt the entire process.

The reverse osmosis step is carried out under process conditions~known per se. For example, a pressure of l to !~

30 bar, preferably 5 to 20 bar, is applied to the mem-brane side. The subsequent flow rate of the condensate can be at 500 to 5,000 l/h, preferably 100 to 1,000 l/h, the result being equally favourable in all cases, i.e.
pure water being obtained as permeate of the reverse osmosis step. As is customary, the temperatures are in the range betw~en 0 to 30C, preferably in the range between 5 and 20C. The usual semipermeable membranes of polymers such as composite materials of polyamides and polysulpllones or cellulose aceta-te, preferably poly-amide/?olysulphone composite materials, having a pore width in the range of ~.5 to 1 nm, prefera:~ly 0.5 to 0.8 nm, can be used.

The residue obtained from the reverse osmosis step is not disposed of, since it still contains salts and therefore valuable substances. Therefore, the residue is subject to thermal tr~atment at an elevated temperature in a preferred embodiment of 'he process. This can take place in a special ?rocess step especially adapted to the conditions. It is particularl~ preferred, however, to unite the residue of the reverse osmosis step with the partially dried salts fro~ the vacuum evaporation for thermal treatment and to thermally treat ~o-th com-ponents together, especially in a rotary tubular kiln.
For this purpose, the residue from the reverse osmosis step is either directly united ~Jith said salts or is suppliedto a storage tank together with said salts from which tank the means for thermal treatment can be fed.
It is another preferred embodiment to subject the resi-due from the reverse osmosis step to a repeated vacuum evaporation st~p. For this purpose, said residue is united with the process mictures having undergone flota-tion and substantially havin~ been freed of organic components, and the two are fed to the means for vacuum evaporation.

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As a result, pure water wherein no salts can be detected is obtained as permeate of the reverse osmosis step. The water can either be reused as process water or fed into the drinking water cycle. Accordiny to the prior art, it was not possible to obtain water completely free of salt alone from the brines in question.
As repeatedly pointed out above, the process cf the present invention can be carried out either continuously or inter-mittently. The continuous process step is preferred.
Below, the apparatus of the invention is illustrated in greater detail with reference to the attached drawings.
Figure 1 shows a flow diagram of the process according to the invention and at the same time a diagram of the positioning of the means characterising the apparatus accord-ing to the invention for treating brines or contaminated mineral salts or mixtures thereof, respectively.
Figure 2 shows a longitudinal section through the rotary tubular kiln as the preferred embodiment of the means for ~ thermal treatment of the partially dried salts.
il Figure 3 shows a cross section through the rotary tubular kiln along the line III-III in figure 2.
Figure 4 shows a view from above of the lid of the rotary tubular kiln.
Figure 5 shows a cross section through the vacuum evapora-tion means preferred according to the invention.
Figures 6a and 6b show cross sections through the stuffing conveyor means which is preferred for feeding the rotary ..

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tubular kiln.

The apparatus for the treatment of brines or contaminat-ed mineral salts or mixtures thereo~ comprises a means 1 for s~paratin the organ-ic components from the process mixture. Preerably, this means is a flotation means.
However it can also consist of a filter, a decanter or a centrifuge. The advantage of the flotation means is that separation of the organic components from the process mixture can substantially be achieved in a simple and efficient manner without using complicated apparatuses.
A centrifuge is also efficient in separating organic components.

In a preferred embodiment there is positioned downstream of the means 1 for separating the organic components a means 2 for drying and ?ulversing the separated organic components. The two means 1 and 2 are connectecl by a conveying means 12 which can, for example, be a conveyor belt, a line or such lil.ce. The products obtained from the drying and pulverisation step in the means 2 are either removed immediately and sold - either in packaged form or as bul~ products - or they are fed into a sto-rage tank 3 via a withdrawing line 21 or such like.

A vacuum ~vaporation means 4 for partially drying the mineral salts or mixtures thereof is positioned down-stream of the means 1 for separating organic components via a line 13. This can preferably be a customary vessel resistant to pressure, for example an autoclave compris-ing the devices for moving, for example stirring, of the contents, the devices for supplying and withdrawing the components involved, the devices for applying pressure, etc., which are necessary for the purposes on hand. A
condenser ? wherein the expanded steams from the means 4 are condensed can be positioned downstream of said va-cuum evaporation means ~ via a line 71. The condensersand coolers known from the prior art can be used as con-denser 7.

In a preferred embodiment of the apparatus according to the invention the vacuum evaporation means is a pressure vessel capable of sustaining the pressure of this pro-cess step and, optionally (and then preferably), con-trollable by a thermostat, said vessel having the shape of a cylinder with a cone tapering sideways attached to its lower end or the shape of a cone tapering downwards.
The aqueous solution or mixture is supplied via suitable feeding lines, preferably via nozzles and especially preferahly via an annular nozzle fed via suitable feed-ing lines outside the vessel. Sources of heat operating outside the vessel, preferably a fuel liquid or a fuel gas flowing in the thermostat casing, make it possible to heat the vessel to process temperature. The vacuum is created by traditional vacuum pumps connected to the pressure vessel hy a tube going out at the top end of the vessel.

In a preferred embodiment the lower end of the cone or the taper of the vessel leads out into a lock chamber for withdrawing the salt, said lock chamber being con-nected to a storage tanX for storing the salt or to a conveying means for conveying the salt. The special ad-vantage of a lock chamber for removing the salt is seen to be the fact that continuous operation of the vacuum evaporation means under unchanging vacuum conditions is possible while salt is nevertheless permanently removed.

In a specially preferred embodiment of the apparatus according to the invention the line by means of which the aqueous solution or mixture is fed to the vessel ends in an'annular nozzle inside the vessel, said annu-2 ~ f ~

lar nozzle having an optional number, preferably, forexample six to eight, of individual nozzles, for spray distribution of the solution or mixture, respectively, inside the vessel. This is conducive to an even distri-bution of the aqueous 2hase inside the vessel and thus a continuous evaporation process, t7hich not only leads to a continuous stream of vapour at unchanging vacuum con-ditions, but also to the formation of even salt crystals.

A tube forming the connection with the vacuum pump or vacuum pumps, respectively, and additionally serving to draw off the steam formed during t~e vacuum evaporation step is attached to the too end of the pressure vessel.
This tube has a cooling system connected to a cooling aggregate, said system preferably being an intensive cooling system which runs in a helix-tyoe manner inside the tube in a specially ~referred emoodiment. The tempe-raturzs of the cooling system are bet~een 8 and 12C at the entry point (at the lower end of the tube in rela-tion to the direction of the vapour flow) and 14 to 32C
at the exit point (at the upper end of the tube in relation to the direction of the vapour flow). Thus, cooling preferably ta~es place by reverse flow cooling.
Owina to the intensive cooling system, which is placed inside the vapour escaoe tube in a space-saving manner, a complete and energy-saving condensation of the vapour is achieved.

In another 2referred embodiment according to the inven-tion one or several vapour traps are positioned in the vapour escape tube beyond the exit from the pressure vessel and a certain distance thereafter, preferably after a bend in the tube, which can, for example, be simple obstacles projecting into the course of the va-pour. In a specially preferred way, the first obstacle is installed immediately be~ond the exit of the vapour .~:; . . , : - -escape tube from the pressure vessel. Salt crystals which may have been carried along by the vapour are se-parated at this point and drop back into the pressure vessel so that the condensate is not contaminated later by larger quantities of salt carried along. ~loreover, such vapour traps form an obstacle against a consider-able decrease of pressure; thus, the process temperature can be maintained more evenly.

At the lo~er end of the vapour escape tube, the appara-tus according to the invention has a reservoir in the form of another loc~ chamber into which loc?~ chamb~r the condensate is let out and removed intermittently or continuously. It is the advantage of this embodiment that the pressure in the vacuum evaporation means can be kept more or less at a constant level. Letting out the condensate via the lock cham~er avoids an interruptiion of the vacuum condensation caused b~ a collapse of the vacuum which would have to be built U? again by pumps.

As an essential element, the apparatus according to the invention also comprises a means 5 for thermal treatment of the partially dried salts from the vacuum evaporation means 4. Even though oth~r means kno~n from the prior art can also be used, the means 5 according to the in-vention for thermal treatment of the partially dried salts is preferably a rotary tubular kiln 53. It is especially proven and therefore preferred to use a rota-ry tubular kiln having a diameter of 450 mm or more and a length of 1,500 mm or more. For example, such a rotary tubularl;iln has a diameter in the range between 450 and 1,200 mm and a length in the range of 2,000 to 4,000 mm.
However other measurements may also be used. Such a rotary tubular kiln 53 can advantageously be moved with a rotating speed in the range of 5 rotations/min to 20 rotations/~in.

?

2 ~

In a preferred embodiment the rotary tubular kiln 53 is positioned in such a way that it is inclined downwards at an angle (alpha) of 2 to 10, prefera~ly 3 to 5, in relation to the horizontal line in the direction of the flow of the salt. This ma!ces it possible to do without costly devices inside the rotary tubular kiln S3 which effect a propulsion of the salts. Rather, the salt fol-lo~s the gravitational force and is successively con-veyed to the highest temperature zone and through said zone to the e~it.

In a further preferred embodiment the rotary tubular kiln 53 is heatable. I~eating is advantageously eff~cted by means of hot gases, preferably combustion gases. For this purpose, the chosen apparatus provides a burner 541, preferably a gas-burner, at a suitable ~osition of the tuhular rotary kiln 53, for example in the lid 54, the heating output of said burner being adaptable to the relevant requirements, for example the size of the kiln, the flow quantity or the humidity content of the added mineral salt.

In a suitable position, for example in the lid 54, the rotary tubular kiln 53 comprises openings or nozzles 542 which make possihle the access of gases. Said openings or nozzles are preferably of a size allowing access of gases, especially oxygenic gases and quite ?articularly air; in a quantity corresponding to a surplus of 100 to 300 %, preferably 200 %, in relation to the oxygen amount necessary for complete combustion of all the remaining organic components of the mineral salts. The amount necessary to adapt to the relevant process si-tuation can easily be determined by the person skilled in the art by measuring the oxygen concentration in the waste gases. The size of the access openings 542 is then adjusted a~cordingly. In this conte~t care must be taken :

that only a light str~am of gas may occur in the rotary tube 53, said stream providing sufficient oxygen for combustion and drawing off the humidity and waste gases contained in the salt, without, however, blowing off lig~ter salt crvstals.

In an especially preferred embodiment which can be seen particularly clearly from figure 2, the rotary tubular kiln 53 ess2ntially comprises (a) a stationery lid 54 comprising a burner device 541, a number of openings or nozzles 542 for the supply of gas, a bearing 543 including pressure-stabilised gaskets 544 and a chamber 545 for grinding and sieving said salts, said chamber being positioned at the botto~ side of said lid 54;

(b) a stationary bottom 56 having a number of openings 561 for the ~ithdrawal of gas and comprising a bearing 562 including pressure-stabilised gaskets;
and (c) a cylinder 55 being rotatable around a longitudinal axis, the sides 551 of said cylinder 55 being sup-ported by said bearing 543 of said lid 54 and said bearing 562 of said bottom 56, a multitude of driver blades 552 being positioned in longitudinal direc-tion parallel to said longitudinal axis of said cylinder S5 and fixed at an angle (B) of substan-tially 90 relative to thc sides 551 of said cylin-der 55, and a sieve grate 553 corresponding in length to the length of said chamber 545 for grind-ing and sieving said salts.

The above~mentioned gaskets 544, 563 in the bearings 543, 562 of the lid 54 and the bottom 56 of the rotary . ~ .

2 ~

tubular kiln can be optional gaskets!cno~n for this ~ur-pose froM the prior art, as long as they protect the bearings against the access of salt. So-called "laby-rinth gaskets" are preferably used in the apoaratus according to tll2 invention.

~s mentioned above, the rotary tubular kiln 53 according to the invention is equippe~ with a chamber 545 for grinding and sieving made possible by a recess in the lid 54, in which chamber 5a5 the dried crystals are ground and sieved in such a way that the resulting mineral salt corresponds to the requirements of the users with regard to aranular size. For this purpose, the chamber 545 for grinding and sieving preferably includes devices for grinding coarser crystals, espe-cially preferably grinding balls. The advantage of grinding balls is to be seen in the fact that they automatically move in the chamber 545 for grinding and sieving during the rotating movement of the rotary tubular kiln 53, thus crushing coarser crystals or smashing stuck-together crystals. Therefore, separate grinding of the mineral salt is not required. According-ly, it is also pre'erred that the openings of the sieve grate 553 through which grate the ground salt crystals are passing are variable according to the size of the salt crystals desired by the user. Crystals whose size does not permit passing through the adjusted openings are crushed by the grinding balls until they are able to pass the openings of the adjusted size.

' According to a further preferred embodiment,the driver blades 552 inside the cylinder body 55 of the rotary tubular kiln 53 are shaped in such a ~ay that they are ~ curved at an angle (gamma) of 120 to 150, preferably t```~ 135, in the rotating direction of the cylinder 55 of ,~i the rotary~tubular kiln at the end opposite the cylinder ~:

~, .
.~
.

2 ~

grate 551. In this context, it is not mandatory, albeit preferred, that the driver blades 552 are bent at a sharp angle as can be seen from figure 3.

The means 4 for vacuum evaporation and the means 5 for thermal treatm2nt of the partially dried mineral salts or mixtures thereof can either be connected immediately via a conveying means 41, for example a line, a conv~yor spiral or such lilce. In a preferred embodiment of the invention the mineral salt or mixture thereof to be thermally treated is supplied to the rotary tubular Iciln 53 via a stuffing conve~or means 46. This can, for example, be a cylinder 461 equipped with a lateral feed nozzl.e or feed container 462, in which cylinder 461 a stuffer 463 is moved manually or mechanically over a distance extending (in the flow direction of the supplied salt) from a point 464 in front of said lateral feed nozzle 462 to a point 465 beyond said lateral feed nozzle 462. By moving said stuffer 463 in said cylinder 461 while said feed nozzle 462 is closed a certain quantity of salt can be fed in the direction of the rotary tube 53. By doing so, the salt to be treated is fed to a tube 47 attached to the stuffing conveyor means 46 extending with its open end 472 into the supply opening of the rotary kiln 53. Suita~l~ devices inside the tube, for exam~le a cone 471 tapering in the flow direction of the mineral salt or mixture thereof, re-spectively, prevents the salt from dropping back into the area where the stuffer moves. The advantage of this stuffing conveyor means is to be seen in the fact that salt conveyed in the direction of the tubular kiln 53 do~s not clog the feed opening if the conveying must be interrupted for some reason and the mineral salt or mixture thereof, respectively, absorbs humidity in the conveying means 46 and sticks together when left stand-ing for a longer period of time, for example over night.

q! ~ ~i The stuffing conveyor means preferred according to this invention makes it possibl~ to restart conveyin~ the mineral salt or mi~ture thereof, respectively, to the rotary tube 53 even after it has been left standing for a longer ?eriod of time.

~ccording to another preferred embodiment of the inven-tion it is also possible to connect said two means 4 and 5 by a comparable conveying means 43 leading via a stor-age tanlc 42. This is advantageous in those cases t~here other batches of mineral salts, for example the so-called waste salts from the operation or the residues from the revorse osmosis step, ar~ to be sup?lied to the means S in addition to the salts from the vacuum evapo-ration means ~. The latter is carried out through the feeding lines 92 and/or 44.

The products obtained from the means 5 for thermal treatment of the mineral salts are either withdrawn and sold - either in packaged form or as bulk products - or supplied to a storage tan]c 6 via a a withdrawing line 51 or such like.

The apparatus ac~ording to the invention also comprises a means 9 for reverse osmosis of the condensate from the condenser 7, said means 9 being connected to said con-denser 7 either i~mediately via a line 71 or via lines 72 and 82 if a storage tank 8 is interposed. Optionally, the alt~rnating pressure pumps 81 and 83, which are activated when a mininum or maximum level of liquid is reached in said storaae tank 8, can be interposed in front of or behind said storage tank 8 in order to apply to said means 9 the process pressure in the range of 1 to 30 bar, preferably S to 20 bar, which is required for reverse osmosis.

2 ~

The customary, commercially available units or means comprising individual, separately available and known parts such as vessel, membrane, connections for feeding and draining etc. can be used as means 9 for the reverse osmosis step. For reasons of easier serviceability, easier access for cleaning and repair worlcs as well as the possibility to adjust the means to certain require-ments a means comprised of individual, separately avail-able parts is preferred.

The highly pure water obtained as 2ermeate from the means 9 for reversn osmosis can either be drained imme-diately and filled into tan~s or fed to a storage tank 10 via a withdrawing line 93 or such like. It is pre-ferred not to dispose of the residue from the means 9 for reverse osmosis, but to redirect said residue either to the vacuum evaporation means 4 via line 91 or, as mentioned above, to the storage tank 42 via line 92 and subsequently to the means 5 for thermal treatment of the partially dried salts.

All components of the means are made of ~aterials not corrodahle by the mineral salts and the solutions there-of for which purpose a number of materials are available to the person skilled in the art. Stainless steel is especially preferred.

Below, the invention is illustrated with the aid of an example without, however, limiting the invention to the application within the field of recycling sodium chlo-ride left over from the curing of raw hides.

Exam~le According to analysis, sodium chloride obtained during centrifuga~ drying and scraping of salt from cured raw ':. , .. , ~: ~ .
i . :.. . ~ ~ ............. . ... : :-' !

2 ~ L~

hides was comprised of the following before passage through the process according to the invention:

85.0 weight percent NaCl 0.4 weight percent naphtllalene and 14.6 weight percent or~anic residues and humidity The salt war a dar~ red-brown in colour and emitted a foul, dung-lil~e smell.

After adding siliceous earth as a flotation agent, 1,000 kg of such a brine were floated and 200 kg of a flota-tion residue obtained which was then dried at 60C and pulverised. From this resulted 120 kg of a dry powder usable as fodder.

The brine ~800 1) containing about 15 % of sodium chlo-ride was treated in the vacuum evaporation means at 40C
and a oressure of 10~1 bar. Together with 426 kg of heavily conta~inated waste salt from the curing of hides, the partially dried sodium chloride (40 % humidi-ty1 thus ohtained was continuously supplied to a rotary tubular 'ciln operated at 350C (inclination alpha: 2;
peripheral speed: 10 rotations/min; diameter: 650 mm;
len~th: 2,500 mm). The passage of the sodium chl~ride through the kiln took 60 minutes. After cooling, 498 kg of a pourable, white and odourless salt were obtained which prov~d to be pure (> 99.5 %) sodium chloride in analysis. The granular size was 0.3 mm.

The vapours of vacuum evaporation were expanded and condensed, and the condensate was cooled to room tempe-rature and subjected to reverse osmosis. This was carri-ed out with a membrane of polyamide/polysulphone compo-site material (pore diameter 0.5 nm) at a pressure of 14 bar, a tem~erature of 25C and a variable flow of 100 to 2 ~

1,000 l/h.

With a salt content of 2 g sodium chloride/l the yield was approximately 60 % of pure water in which no left-over salt could be found.

An additional cxperiment under comparable conditions resulted in about 52 % of pure water with a salt content of 3 g sodium chloride/l.

The residue was subjected to the vacuum evaporation step once more.

Claims

1. A process for the treatment of brine and contaminated mineral salts and mixtures thereof comprising the steps of (a) substantially separating organic components from the process mixture, (b) subjecting the resulting mixture to a vacuum evaporation step, (c) thermally treating the partially dried mineral salts or their mixtures at an elevated temperature and thereafter obtaining pure dry mineral salts or mixtures thereof, (d) condensing the vapour resulting from the vacuum evaporation step and subjecting said condensed* vapour to a reverse osmosis step, and *scalding condensation (e) obtaining from said reverse osmosis step pure water.

2. Process according to claim 1 wherein the brine, mineral salt and/or mixture thereof is subjected to a step of flotation, decan-tation or centrifugation in order to separate organic components, and optionally the separated organic components are additionally dried and powdered.

3. Process according to any of the claims 1 or 2 wherein the va-cuum evaporation step is carried out at a temperature of from 20 to 50 °C, preferably at a temperature of from 42 to 50 °C, and/or at a pressure of from 0,5 to lo-a bar, preferably at a pressure of from 10-1 to 10-2 bar.

4. Process according to any of the claims 1 to 3 wherein the ther-mal treatment is carried out in a rotary tubular kiln.

5. Process according to any of the claims 1 to 4 wherein the ther-mal treatment is carried out in a rotary tubular kiln rotating at a rotating speed of from 5 to 20 rpm.

6. Process according to any of the claims 1 to 5 wherein the ther-mal treatment is carried out in a rotary tubular kiln inclined downwards, in the direction of the flow of the mineral salt(s), at an angle (alpha) of from 2 to 10 °, preferably of from 3 to 5 °, relative to the horizontal plane.

7. Process according to any of the claims 1 to 6 wherein the mine-ral salt or the mixture thereof is fed to the rotary tubular kiln by means of a stuffing conveyor means.

8. Process according to any of the claims 4 to 7 wherein the ro-tary tubular kiln is charged with hot gases, preferably with hot gases resulting from a combustion, more preferably with hot gases resulting from a combustion in a gas-burner.

9. Process according to any of the claims 4 to 8 wherein the ro-tary tubular kiln is charged with an excess of air in the gas stream of from 100 to 300 %, preferably of 200 %, based on the amount necessary for the complete combustion of the residual orga-nic components.

10. Process according to any of the claims 1 to 9 wherein the thermal treatment is carried out at a temperature of from 140 to 500 °C, preferably of from 300 to 400 °C.

11. Process according to any of the claims 1 to 10 wherein the step of vacuum evaporation is controlled in such a manner that the condensate resulting from the step of vacuum evaporation can con-tinuously and immediately be subjected to a reverse osmosis step or additionally be led to the step of reverse osmosis via a storage tank.

12. Process according to any of the claims 1 to 11 wherein the process is carried out in a continuous manner.

13. Apparatus for the treatment of brine and contaminated mineral salts and mixtures thereof comprising (a) a means (1) for separating organic components from the process mixture;

(b) a means (4) for vacuum evaporation in order to partially dry said mineral salts or mixtures thereof;

(c) a means (5) for the thermal treatment of said partially dried mineral salts or mixtures thereof resulting from said means (4) for vacuum evaporation;
(d) a condenser (7) for condensing the humid vapors resulting from said means (4) for vacuum evaporation; and (e) a means (9) for reverse osmosis treatment of the condensate resulting from step (d); as well as (f) conveying means (12, 71, 93) connecting in series said means (1) for separating organic components, said means (4) for vacuum evaporation, said condenser (7) and said means (9) for reverse os-mosis treatment, and conveying means (41) connecting said means (4) for vacuum evaporation and said means (5) for the thermal treatment of said salts.

14. Apparatus according to claim 13 wherein said means (1) for se-parating organic components from the process mixture is a flo-tation means, a decanter or a centrifuge.

15. Apparatus according to any of the claims 13 or 14 comprising in addition a means (2) for drying and powdering said separated organic components.

16. Apparatus according to any of the claims 13 to 15 wherein said means (4) for vaccum evaporation for partially drying said mineral salts or mixtures thereof comprises a vessel 1401) in the shape of a cylinder having attached at its lower end a tapered cone (402) or in the shape of a reversed tapered cone (402), the temperature of which vessel (401) optionally being controlled by a thermostat, said vessel (401) comprising a feeding line (4052) leading to an annular nozzle (405) for spraying said aqueous solution containing said mineral salts or mixtures thereof within said vessel (401);
one of more lock chambers (403) at the bottom of said vessel (401) for removing said partially dried mineral salts or mixtures thereof; a tube (406) for removing the water vapour from the top of said vessel (401) comprising one or more vapour traps (4061) and a cooling device (907) for condensing the water vapour said cooling device (407) preferably being fitted into said tube (406);
one or more lock chambers (408) for removing the condensed liquid;
and one or more vacuum pumps ((09).

17. Apparatus according to any of the claims 13 to 16 wherein said means (5) for the thermal treatment of said partially dried salts resulting from the step of vacuum evaporation is a rotary tubular kiln (53).

18. Apparatus according to any of the claims 13 to 17 wherein said means (5) for the thermal treatment of said partially dried salts is a rotary tubular kiln (53) which is heated by means of hot gases, preferably by hot gases resulting from a combustion, more preferably with hot gases resulting from a combustion in a gas-burner.

19. Apparatus according to any of the claims 13 to 18 wherein the rotary tubular kiln (53) substantially comprises (a) a stationary lid (54) comprising a burner device (541), a num-ber of openings or nozzles (542) for the supply of gas, a bearing (543) including pressure-stabilized gaskets (549) and a chamber (545) for grinding and sieving said salts, said chamber being po-sitioned at the bottom side of said lid (54);

(b) a stationary bottom 156) having a number of openings (561) for the withdrawal of gas and comprising a bearing (562) including pressure-stabilized gaskets (563);

(c) a cylinder (55) being rotatable around a longitudinal axis, the sides (551) of said cylinder (55) being supported by said bea-ring (543) of said lid (54) and said bearing (562) of said bottom (56), a multitude of driver blades (552) being positioned in lon-gitudinal direction parallel to said longitudinal axis of said cy-linder (55) and fixed at an angle of substantially 90 ° relative to the sides (551) of said cylinder (55), and a sieve grate (553) corresponding in length to the length of said chamber (545) for grinding and sieving said salts.

20. Apparatus according to any of the claims 13 to 19, additio-nally comprising a storage tank (42) in the line (43) between said means (4) for vacuum evaporation and said means (5) for the ther-mal treatment of said partially dried salts.

21. Apparatus according to any of the claims 13 to 29, additio-nally comprising a supply line (44) for supplying waste salts into said additional storage tank (42).

22. Apparatus according to any of the claims 13 to 21, additio-nally comprising a supply line (92) between the means (9) for re-verse osmosis and said additional storage tank (42).

23. Apparatus according to any of the claims 13 to 22, additio-nally comprising one or more storage tanks (3, 6, 10) for said se-parated, dried and powdered organic components, said pure salts and/or said pure water.