IL24090A - Production of dried granular solid chemical products - Google Patents

Production of dried granular solid chemical products

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Publication number
IL24090A
IL24090A IL2409065A IL2409065A IL24090A IL 24090 A IL24090 A IL 24090A IL 2409065 A IL2409065 A IL 2409065A IL 2409065 A IL2409065 A IL 2409065A IL 24090 A IL24090 A IL 24090A
Authority
IL
Israel
Prior art keywords
granules
reactants
bed
reaction
gases
Prior art date
Application number
IL2409065A
Original Assignee
Montedison Spa
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Montedison Spa filed Critical Montedison Spa
Publication of IL24090A publication Critical patent/IL24090A/en

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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J8/00Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
    • B01J8/18Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
    • B01J8/24Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles according to "fluidised-bed" technique
    • B01J8/245Spouted-bed technique
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2/00Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
    • B01J2/16Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by suspending the powder material in a gas, e.g. in fluidised beds or as a falling curtain
    • CCHEMISTRY; METALLURGY
    • C05FERTILISERS; MANUFACTURE THEREOF
    • C05BPHOSPHATIC FERTILISERS
    • C05B19/00Granulation or pelletisation of phosphatic fertilisers, other than slag

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Fertilizers (AREA)
  • Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)

Description

0'©3» 0»'β*3 DVJVt "OX** The production of dry granular chemical fertilizers MQNTECATINI BBISOfl S.p.A. formerly Societa Edison G i23080 This invention relates to the production of dried granular solid chemical products. More particularly the inventionconce ns a process for obtaining solid chemical products such as inorganic salts and particularly fertilizers in a dried granular state, starting directly from reactants in gaseous state, in solution or in suspension.
The usual processes for obtaining dried granular products, and particularly ertilizers, usually consist in first reacting the various reactants, for instance by neutralization reactions between an acid or a mixture of acids and salts on the one hand and a base or basic salt on the other hand, or decomposition of minerals with aqueous inorganic acids, so as to achieve a solution, suspension or slurry which is subjected to granulating treatment and drying.
There are, therefore, three separate operations, the first being the chemical reaction, and the latter two being physical operations, namely, granulation and elimination of the liquid phase which is generally water* he operations of granulation and the elimination of the water from the slurry, solution or suspension may be effected in several different ways, depending on the quantity of liquid to be removed and on the product to be processed. Amongst the more commonly used ways are: - the granulation in drums or mixers of the slurry prior to addition of recycled pulverulent materials intended to lower the liquid content of the slurry so as to obtain moist granules which are subsequently dried for instance in rotary furnaces traversed by a flow of - "prilling**, that is, spraying the product into a solidification tower in counter current to a flow of cool air so as to cause the crystallization or solidification of the sprayed product, which will then be dried before it reaches the base of the tower; and - "spray-drying11 (or atomised spraying), that is atomizing a slurry of high moisture content in a flow of hot gases so as to give a dry powder which, in order to be transformed into a granular shape, is then re-wetted, compressed and dried. times Furthermore, it is somew-ha-t- possible to combine two of the operations into a single one. Thus, for example, it is possible to granulate and dry at the same time in a fluid bed granula or or special rotary drum, or the chemical reaction may be conducted with simultaneous granulation in, for example, a T.V.A. granulator-ammonizer.
All these known processes have a least some drawbacks such as operational and handling difficulties, poor control of the shape and size of the granules obtained, the limitation of using only raw materials having a low liquid content, or the necessity of considerable recycling of pulverulent materials which require bulky equipment including auxiliary equipment and increases the processing costs, considerably increase the operation times, and in general, necessitate more operational stages.
It is, therefore, an object of this invention to provide a process of the highest operational simplicity and effectiveness which is also extremely quick and economical, for the production of chemical fertilizers as solid, dry, According to the present invention there is provided a process for obtaining solid dry granules of chemical fertilizers starting from the reactants at least one of which is in a liquid state, comprising injecting the reactants in an atomized state through a fluid bed of growing granules of the product, which fluidized bed has its cross-section increasing with height in con-current flow with the rising gaseous fluidizing current, so that the reactants before, during or after any liquid materials evaporate, a proportion of the granules being discharged to keep the fluid bed at a substantially constant level.
The reactants tend to react immediately after injection and deposit as a thin layer on the granules. Each layer completely reacts and dries and due to the circulation of the granules in the usual way known with fluidized beds a number of successive layers build up to form the granules. Granules of about the desired average size and of substantially constant shape are continually discharged.
The heat necessary or drying the product and for effecting an endothermic reaction, can be supplied to the gaseous fluidizing current which transfers its heat to the fluid bed at an extremely high heat exchange rate and so ensures the evaporation of the liquid phase and the shifting of the reaction equilibrium in the desired direction in the case of an endothermic reaction.
With a strongly exothermic reaction it may not be necessary to supply further heat for the evaporation of the liquid since the heat given rut by the reaction may be sufficient and the fluidizing gas may not need any further heating.
The apparatus necessary for a process according to the invention is very simple. An upright tower which is preferably cylindrical may be used having a conical lower end preferably with an opening angle of 55 to 65°. The gaBes for fluidizing the granular bed are fed into the lower end. In the lower part of the cone-shaped bottom is an injector for atomizing the reactants and injecting them in con-current flow with the fluidizing gases. An overflow, placed in correspondence with the top of the bed, and preferably at the end of the conical part, is provided for the discharge of the dry granulary product while the exhausted gases are discharged from the top of the cylinder. These gases will normally be passed through a cyclone in order to remove entrained dust, which is normally recycled into the apparatus in order to form new condensing nuclei for the subsequent growth granules, and may be subjected to the removal of the sensible heat and/or of useful substances contained therein such as un-reacted gaseous reagents and volatile reaction products. For example, in the production of ammonia salts it is possible to recover both the sensible heat of the exhausted gases as well as the ammonia contained therein by washing with a solution of the acid to be used as a reagent.
In order to support the bed no grill or porous baffles are necessary, as is known in the technique of the fluid beds with the cross-section increasing with the height, and it is sufficient to suitably adjust the rate of the flow of the fluidising gases in order to maintain the bed fluidized and for causing, at the same time, an orderly circulation of the bed components, so that the solid granules are rapidly projected upward by the gaseous current through the central zone of the bed forming a kind of jet and to drop then back again onto the towards the narrow section of the cone in which is placed the injector, to be then thrown upward again. All the time the granules are gradually growing by successive deposits of thin layers, until the desired size is reached. The granules of finished product are thus the result of successive cycles, each one comprising the reaction between the components introduced, the granulation and the drying. At the same time there takes place a screening of the particles whereby the greater particles tend to remain on the top or surface of the bed and on its periphery wherefore they can be easily removed through the overflow.
The manner of introducing the reactants into the reactor will vary according to the type of chemical reaction involved. For instance, ink neutralization reaction and in general whenever the reaction takes place by simple mixing, it is necessary to introduce them separately in such a way that the mixing takes place in the reactor. For this purpose the reactants are introduced into the reactor through an injector formed by at least two concentric nozzles and into which injector they are introduced separately. Alternatively, if one of the reactants is gaseous, it may be introduced into the reactor mixed with the fluidizing gases.
When, on the contrary, the reaction does not take place by simple mixing but has to be provoked by suitable conditions obtaining only inside the reactor, they may be introduced into the latter already mixed. The injector introduces the various reactants at the base of the fluid bed, below the lower section, into the fluidizing current also introduced from the base.
The tip of the injector should be shaped so as to commences right at the outlet of the nozzle. The reaction will normally go on in an aerosol phase and then complete itself on the surface of- the granules.
If one of the raw materials is gaseous, for instance ammonia or carDon dioxide, it is preferably conveyed to the inner ozzle of the injector at a higher speed than that of the gaseous fluidizing current, thus ensuring the atomization and intimate mixing with the liquid component, i.e. a solution, a suspension, a slurry or a paste, injected through the outer nozzle.
If none of , he reactants is gaseous, the atomization of the reactants is furthered preferably by the action of compressed air forced through the outer nozzle.
The product discharged from the bed through the overflow can be screened and fines below a certain size will usually be recycled back into the reactor with the dust particles acting as growth nuclei for the successive granules.
It is possible to run the process as a continuous operation and, by suitably adjusting the speed, flow and tempera ture of the feed and of the fluidizinggases,he size of the granules tends to near a constant size so that a minimum of recycling is necessary* The addition of new growth nuclei for compensating the drawing off of the granules is not always necessary since new nuclei are formed by abrasion of the particles among themselves or against the walls of the reactor.
An important feature of the invention is that it ensures an extremely high exchange between the solid and the gaseous phase because of the enormous specific surface of the bed; in this way the kinetics of the chemical physical processe $he process according to this invention may be applied to all those industrial procesoeo where solid dry granules are to be obtained starting from reagents, at least one of which is in a liquid state. For example, it may be applied to the production of: from - ammonium phosphate/dilute phosphoric acid and gaseous ammonia; - sodium phosphate from dilute phosphoric acid and sodium hydrate? - potassium metaphosphate from potassium chloride and dilute phosphoric acid; - triple-super-phosphate from dilute phosphoric acid and phosphorite ; - ammonium sulphate from ammonia and sulphuric acid even highly diluted; - a mixture of ammonium nitrate and ammonium sulphate commonly known as ammonium sulphonitrate, dilute nitric acid and ammonia, from dilute nitric acid, dilute sulphuric acid and ammonia, or from ammonium nitrate, dilute sulphuric acid and ammonia, carrying out the mixing under such temperature conditions as not to cause the ammonium nitrate to decompose; - complex fertilizers of various formulations from nitric acid, phosphoric acid, ammonia and potassium salts; - sodium or potassium carbonate from carbon dioxide and dilute sodium or potassium hydrate, the intermediate formation of bicarbonate being avoided, even with an excess of COg, by keeping the bed at such a temperature that the bicarbonate is unstable; - aluminium fluoride from hydrofluoric- acid in the gaseous state or in aqueous solution and aluminium hydrate.
Depending on the general requirements of the process according to this invention, i.e. the chemical nature, granule sizes, the degree of dryness of the granules, the type of reactants, their liquid contents, the masses involved and environmental conditions, the operational conditions such as temperatur injection velocity of the gases and of the reactants can be widely varied. Thus, for example: - the inlet velocity of the fluidizing gas depends on the diameter of the apparatus and may vary in the range of from 30 to 100 m/sec? - the inlet velocity of the reactants is preferably kept at not less than the velocity of the fluidizing gas? - the average outlet velocity of the gases (fluidizing gas, water vapour and eventual gaseous reaction products) should be such as not to cause too much entraining of solid products, it is therefore a function of the type and size of the granules and in value may vary between 1 - the inlet temperature of the supporting gas is a function of the type of product and of the diameter of the apparatus and may attain a value of from 500 to 600°C and more; - the outlet temperature of the gases is a function of the product and must in any case be higher than the dew point of the gases in order to avoid condensations in the circuit? - the top of the bed is preferably maintained slightly part above (i.e. 20 to 7Q cm) the terminal/portion of the - the reactants may be in a gaseous, liquid or solid state, provided they may be injectable, at least one of them being liquid; - the final moisture of the products obtained depends on the type of product itself besides of course on the degree of dryness required; the average degree of moisture is around 0.3 to 0.4$ but, if desired, also values below 0.1$ may be achieved; - the average granular size of the product obtained may be varied at will within a wide range, for instance from 0.5 to 8 mm and preferably from 1 to 4 mm in the case of fertilizers.
The process of the present invention allows the achievement of considerable advantages in comparison to the processes conducted according to the known techniques, amongst which advantages may be particularly pointed outs ~ due to the fact that the reaction, granulation and drying occur simultaneously, the total duration of the process is reduced and the apparatus used for carrying it out is of simpler design than in known processes; ' » the reactor-granui tor dryer may be made of iron rather than of stainless steel since the reactants do not come into contact with the walls but only the granular product after the surface thereof has been dried; in the case of chemical reactions that develop corrosive gases it will be necessary to take care to avoid any condensation of the moisture of the exhausted gases by insulating all cold parts in the circuit on which condensation of the gases in the case of exothermic processes, the full reaction heat is completely exploited since this latter develops inside the reactor-granulator; the reaction can be carried out effectively and rapidly in dilate phase even in cases which would normally require concentrated reactants and long reaction times, which is due to the fact that the reactants are in a fluidized phase and undergo an immediate concentration onthe surface of th«? particles at the expense of the sensible heat of the gases because of the very high energy exchange that occurs in the fluidized phase; thus the flexibility of the process is quite considerable similarly, owing to the very high heat exchange, the drying of the granules is very rapid; the thermal efficiency is higher than in conventional drying processes as very hot gases can be introduced with products that usually need lower drying temperatures inasmuch as the reactants and the product obtained underg a very fast evaporation of the water that causes a lowering of the temperature of gas to values which are not harmful to the finished product; the equipment is very simple and of small volume thus facilitating considerably its insulation, besides which there is a complete lack of moving parts (with the exception of a blower fan and the feeding pump to the injector); therefore it is also very inexpensive and easily maintained and controlled and can be made fully automatic; the characteristica of the granules obtained are very good both as regards appearance and homogeneity of the the drying involves only the surface zone of ¾ach granule, the granule is more compact and is without the capillary channels that usually remain after drying when granules are produced by agglomeration of the particles in a wet state. Such channels are due to the enclosed water that migrates from the centre of the granule towards the outside surface with a consequent unfavourable effect on the mechanical resistance; - in consequence of the regular shape of the granules and because of the almost total lack of big agglomerates the grinding and screening installations can be eliminated altogether or at least reduced to a minimum, a screening being sufficient before recycling undersized granules and sending oversized granules for grinding; - furthermore, the handling of the separate raw materials is normally much easier than the handling of the already reacted materials, i.e. slurries, suspensions or super-saturated solutions, Just as it is easier to measure them.
The following Examples are given as illustrating the invention.
Example 1 Production of ammonium phosphate Granular ammonium phosphate was prepared from dilute phosphoric acid JO/o by weight of o^&ined & we* process, and gaseous ammonia (example of a reaction between a liquid and a gas) . 550 kg of a previously prepared granular product rate of 3,000 Hm3/h. The cone angle was 60O and the average porosity of the bed was around 0.5. Into the reactor were then injected through an injector placed at the base of the apparatus, 6601/h of phosphoric acid dilited to 30$ by weight of through a peripheral nozzle of the injector, and 75 kg/h of gaseous ammonia through the inner nozzle. The reactants were injected at such a velocity as to cause the atomization and intimate mixing of the acid with the gaseous ammonia adjacent to the exit of the injector.
The sensible heat of the carrier gas, together with the reaction heat, favoured the evaporation of the water and the reaction was completed on the surface of the particles.
At the operational production rate the apparatus had an output of 500 kg/h of a very homogeneous and compact product having an analysis by weight of 12$ N and 2$ a moisture content of 0.3$ and granules measuring between 2 and 4 mm, while smaller granules were recycled to the reactor.
The gases left the reactor at a temperature of 105°G, while the entrained dusts were separated in a centrifugal dust separator and returned to the reactor.
By operating at the same conditions and by varying the molar ratio of HH^ to H^PO^, fertilizers of various compositions, for instance between 11:53 and 16:4-8, were obtained· The operational conditions were similar, but with an Increase in hourly production rate due to the increased reaction heat which in turn was due to the fact that the molar ratio NH^H^PO^ was close to 2. Because of the higher temperature in this case the ammonia losses were somewhat greater. Therefore, it is possible in such a case to scrub the exhaust gases Example 2 Production of triple-sugerphosphate Granular triple-superphosphate -was prepared from dilute phosphoric acid 30 by weight of and pebble- phosphorite, an instance of a reaction between a liquid and a solid. 214 kg/h of pebble-phosphorite were continuously cold mixed with 405 1/h of H-jPO^ having a concentration of 30 by weight of ^2 * Tiie analysis ¾ weight of the phosphorit used was as follows: size of granules: P2°5 oo2 = 3.O5S - 0.2 mm a 9 .0$ - 0.16 mm « 89.0$ sio2 = - 0.11 mm * 73.0 2*5% - 0.08 mm « 58.0 R2°3 CaO = 3.8 - O.O5 mm « 42.0 MgO ss 0.6$ H20 as 1.5 Loss of weight at 400°C = 3.5$ The suspension obtained was then immediately sent into the granulating reactor through a compressed air nozzle in order to promote the atomizing of the mixed raw materials. The bed, consisting of about 350 kg of a previously prepared product, was fluidized by a current of hot air at a temperature o ■¾ of 280 C and having a flow rate of 3t000 Mer/ v ¾e angle of the conieal part of the reactor was of 60° and the average porosity of said product amounted to around 0.5.
The particles forming the fluid bed had a temperature of 90 to 100°C, the gases left the reactor at almost the same temperature entraining with them some reaction products such centrifugal dust separator the HP contained in the gases was separated before discharging the exhausted gases into the atmosphere.
At the operational rate, after about two hours from start-up, the reactor had a continuous output of 450 kg/h of finished product, whose chemical analysis established immediately upon the withdrawal of a sample, showed the following values by weight: P20(j total « 49«7$ The granular siae of the product" ^2^5 aseimilal5le = 48.8$ was comprised between 2 and 4 mm.
P20-- soluble in HgO = 46.3 Pg05 free = 2.8 moisture « 2. $ When using other types of phosphorites such as Gafsa, the Casablanca, Florida and Jordan phosphorite, practicallj same reaction yields were obtained.
Example 3 (an example of reaction between a gas, a liquid or mixture of liquids and a solid). 315 1/h of H^ O^ at a concentration of 30$ of PgOg «ere uninterruptedly mixed oold with 332 kg/h of dry K-S04 and with 300 kg/h of a solution of HH^ UO^ having a concentration of 82$ by weight.
The pulp was partially ammoniated with 31.2 kg/h of H&j up to a pH of 3 and was then sprayed through the outer nozzle of an injector placed at the base of the fluid bed.
This bed consists of about 350 kg of particles and is supported by 3,000 Nm^/h of air at a temperature of 350°C. The cone's angle was 60°C and the average porosity of the bed was about 21.5 kg/h At the same time, through the inner nozsle/of gaseous NH-j were injected to promote the atomization of the above pulp and to neutralize it to a pH of 5.2.
The bed had a temperature of about 90°C and the gases left the reactor at 100°C to be conveyed to a dry separation stage in order to recover the entrained dusts. The gases were then washed by means of the phosphoric acid to be used in the process to recover the ammonia present in the gas and to recover the sensible heat of the gases themselves.
At operational production rate, 750 kg/h of fertilizer were obtained analyzing 16:16:16 and with a moisture content ^0. $ and a granular size of between 2 and 4 mm.
The product obtained may be stored while warm and remains perfectly conditioned without the use of anti-caking agen s · A variant of the process consisted in introducing the whole or part of the solid component (in this instance 2S0^) directly into the reactor together with the recycled fines that pass through the screen, instead of admixing it beforehand with the other components.
With the same raw materials used in different proportion® (as a source of potassium KC1 may be used), it is possible to obtain other formulations, such as 8:24:24» 8:16:32, 11:22:22 and 12:24: 2, while maintaining almost identical operational conditions.

Claims (9)

- 17 - 24090/2? It- : CLAIMS
1. A process for obtaining solid dry granules of chemical fertilisers from the reactants at least one of which is in a liquid state, comprising injecting the reactants in an atomiaed state through a fluid bed of growing granules of the product, which fluldized bed has its cross-section increasing with height^ in con-current flow with the rising gaseous fluidizing current, so that the reactants before, during or after reaction deposit on the surface of the moving granules and any liquid materials evaporate, and the granules grow gradually owing to the formation of successive layers of reaction products, a proportion of the granules being withdrawn at such a rate as to keep the fluid bed at a substantially constant level,
2. A process as claimed in Claim 1, in which one or more of the reactants is injected at a velocity greater than or at least equal to that of the fluidi2ing current,
J. A process as c med i Claim 1 or 2, in which the injection of the reactants is promoted by a compressed gas.
4. A process for obtaining solid dry granules of a chemical fertilizer starting from the reactants substantially as herein described with reference to the Examples.
5. An apparatus for carrying out a process as claimed in any preceding claim which comprises an upright cylindrical tower for containing the fluidized bed and having an inverted cone-shaped lower end and an injector adjacent to the base of this cone-shaped part*
6. An apparatus as claimed in Claim 5, in which the opening angle of the cone-shaped part is from 55 to 65°· - 1Θ - 24090/2,
7. An apparatus as claimed in Claim 5 or 6, in which the injector comprises a central nozzle with one or more surrounding concentric nozzles, different reactants being fed to each nozzle.
8. An apparatus as claimed in any of Claims 5 to 7 adapted for an overflow discharge of the granules of desired size and comprising an overflow positioned adjacent to the top of the conical part.
9. Granules prepared by a process as claimed in any of Claims 1 to 4 or in an apparatus as claimed in any of Claims 5 to 8. MC: Z
IL2409065A 1964-08-12 1965-08-05 Production of dried granular solid chemical products IL24090A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
IT1742764 1964-08-12

Publications (1)

Publication Number Publication Date
IL24090A true IL24090A (en) 1969-07-30

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Application Number Title Priority Date Filing Date
IL2409065A IL24090A (en) 1964-08-12 1965-08-05 Production of dried granular solid chemical products

Country Status (10)

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BE (1) BE668009A (en)
CH (1) CH460724A (en)
DE (1) DE1542425A1 (en)
DK (1) DK116451B (en)
ES (1) ES316591A1 (en)
GB (1) GB1114128A (en)
IL (1) IL24090A (en)
NL (1) NL145465B (en)
NO (1) NO121333B (en)
SE (1) SE332158B (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2903289A1 (en) * 1979-01-29 1980-08-07 Otto & Co Gmbh Dr C METHOD FOR GRANULATING THE FALLING PRODUCTS CREATED FROM AMMONIUM COMPOUNDS BY SUBSTITUTION WITH EARTH ALKALINE COMPOUNDS
FI105472B (en) * 1998-05-15 2000-08-31 Kemira Agro Oy Multi-suspension process for the preparation of a fertilizer
DE102019211958A1 (en) * 2019-08-08 2021-02-11 Glatt Ingenieurtechnik Gesellschaft mit beschränkter Haftung Process for the production of fertilizer granules
CN115722158B (en) * 2022-11-28 2024-07-16 兰州理工大学 Multilayer expansion fluidized bed reactor system and process for producing hydrogen fluoride
CN116272645B (en) * 2023-05-11 2023-08-04 中建环能科技股份有限公司 Sewage denitrification carrier preparation system and preparation method

Also Published As

Publication number Publication date
NL6509990A (en) 1966-02-14
BE668009A (en) 1965-12-01
GB1114128A (en) 1968-05-15
NL145465B (en) 1975-04-15
SE332158B (en) 1971-02-01
DK116451B (en) 1970-01-12
ES316591A1 (en) 1966-04-01
NO121333B (en) 1971-02-15
DE1542425A1 (en) 1969-12-18
CH460724A (en) 1968-08-15

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