CA1132335A - Method for processing wastes resulting from production of phosphorus, namely, slime and off-gases, with utilisation of the resultant products - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The method comprises processing of the slime and off-gases resulting from the production of phosphorus by an aqueous solution of copper sulphate preferably at a concentra-tion of from 15 to 50% by weight. The process is preferably conducted at a temperature within the range of from 20 to 80°C
to give two products, i.e. solid and liquid ones. The solid product containing mainly copper phosphide as well as fluorides, chlorides of alkali metals and silicon, calcium and aluminium silicates is used as a modifying and refining agent for hypereutectic silumines as well as for the production of a copper-phosphorus alloy. The liquid product containing phosphoric acid, sulphuric acid, and copper sulphate serves as the starting material for the manufacture of a copper-containing fertilizer therefrom. The method according to the present invention makes it possible to improve the production of phosphorus so as to eliminate the formation of secondary wastes and thereby contribute to a better control of the environment protection.

Description

ME~HOD ~ PROCESSING WAS~ES RESUL~ING ~ROM PRO~UC~ION
OF PHOSPHORUS, NAMEL~, SLIN~ AND OFF~ ASES, WI~H U~ILI-ZA'~ION OF THE RESU~TANT PRODUCTS

A The present invention broadly relates to bhc environmentalcontrol and, more specifically, to the production of elemental phosphorus; in particular, the present invention rola-tes to methods of processing of wastes resulting from the production of elemental white (yellow) phosphorus, namely slime and of~ ga-ses with the, utilization of the obtained products.
In the production of elemental phosphorus by way of ther-mal reduction of phosphate materials~by means of carbonaceous reducing agents in the presence of silica~wastes are formed, such as ferrophosphorus, slag, slime, off-gases, Cottrell dust and phosphorite fines.
Ferrophosphorus is used mainly in metallurgy an~ slag, in the production of building and construction materials. Depend-ing on the startin~ stock and co~ditions of the process of phosphorus manufacture, up to 0.7% of elemental phosphorus is entrained with the off-gases and up to 8% of elemental phos-phorus is lost with the slime. The off-gases contain, per cent by volume: H2~ up to 1.3; CO, up to 90; CO2, up to 5; H2S, up to O.9; poisonous gas phosphine PH3 up to 0.4~as well as vapours or fine particles of phosphorus.

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~ ~ 3z33s l`hough calorific power of the of~-gases is as high as 3~000 kcal/m3, said of~-gases cannot be used, without purifi-catio~, as a fuel, since phosphine and phosphorus particles contained therein cause corrosion of the metal of heating units. ~or this reason, onl~ a portion of the off-gases is used ~or dehydration, decarbo~ization of phosphorites and for heating of electrostatic precipitators. The major portion of r the of`~-gases is combusted over the stack as a torch, thus pol-A e/~l~/r~ nen7L
luting the envi-r~n~n~with phosphorus oxides and, in the case of presence of humidity in air, with phosphorus acids.
Another waste product resulting from the manufacture of elemental phosphorus is slime. Phosphorus slime is a chemico--mechanical~col,lloidal system consisting of substances based on oxides of a~ earth metals and silicon fluorides and chlori-des thereof, oxides of aluminium and calcium, fine-dispersed carbon and the like, strongly bonded with phosphor~s into aggre-gates (micelles) by absorption forces of cohesion. ~he slime com-position depends on the nature of the starting stock employed ~or the production o~ phosphorus, as well as on the technolqgi-cal parameters of the process. Phosphorus slimes may be classi-~ied as "thin" and "thick'l ones. A "thin" slime contains up to 35% o~ phosphorus as calculated ~or the dry solids. ~his slime is a dark-brown viscous non-uni~orm mass.
Known in the art are certain methods for processing o~
"thick" slimes. As to "thin" slimes, these are collected, as a ~:

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~3Z335 rule because of the absence o~ inexpensive and efficient pro-cessing methods, in slime-collectors which occupy lar~e areas, ~ e~ ^an~e~
1~ pollute the cnvironmcnta and are rather fire-hazardous. In cer-tain cases, in order to avoid pollution of the environments, slimes with a small content of phosphorus are discarded into abandoned mines.
Another waste product resulting from the manufacture of elemental phosphorus is Cottrell dust deposited on electrostatic precipitators upon passing of the flue-gases therethrough. This dust contains up to 22% by weight of P205 and sometimes up to 15%
by weight of K20. The use of this dust as a fertilizer is not always possible, since it contains particles of elemental phos-phorus. For this reason, the Cottrell dust is discarded from the electrostatic precipitators into a bin and then into a tank with water, wherein it forms so-called Cottrell milk which is then processed by conventional methods. Particularly, ~ottrell dust may be returned to the furnace as a component of the charge.
In many cases it is economically efficient to discard the Cott-rell dust into refuse dumps, but this results in environment pollution.
Still another waste product resulting ~rom the manu~acture o~ phosphorus and formed in grinding of the starting stock, i.e~
phosphorite, is phosphorite fines. As a rule, a small-size frac-tion screened upon crushing is agglomerated or briquetted, which in~olves additional costs~ In certain cases it is more efficient, from the economic considerations, to discard the fines back in-to the pit, wherein phosphorite is extracted. This, however5 also results in enviro~ment pollution.
Known in the axt are numerous methods for processing of phosphorus slime. Mostly used now are methods contemplating combustion of slimes at the temperature of 1,000C. Used for combustion are slimes with a content of phosphorus of at least 50% by weight. Slimes containing 15 to 50~0 by weight of phos-phorus are processed by distillation. Distilling-off of phos-~ 5~erhe~te~
A phorus ic effected by means of oYorhoatcd steam at a tempera-ture within the range of from 160 to 175C under a pressure of from 6 to 8 atm. Enown methods for processi~g of "thin" pho~-phorus-containin~ slimes by distillation, filtration, centrifuga-tion or briquetti~g feature low efficienc~, necessitate high expenses for their commercial implementation and cannot provide for utilization of all the products involved in the processing.
Known in the art are also methods for breaking slimes by means of inorganic salts and acids. ~hus, US Patent No. 3,515,515 Cl. 23-223, 2. V~.7D, teaches breaking of slime at a temperature of from 40 to 70C by means of water-soluble compoundR of hexa-valent chromium, i.e. chromates and bichromates of metals, and sulphuric acid. The method contemplates the use of a solution of chromates with a concentration of from 0.1 to 10.0% by weight as calculated per chromic acid~ ~ulphuric acid is added to chro-mic acid at the ratio of 1:1.

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1~3'~335 Another US Patent No. 3,442,621 Cl. 23-223, 6.V.69, teaches processing of slime with chromic acid in a concentra-tion of from 0.1 to 10.0% by weight of water in the slime and with hydrochloric acid or sulphuric acid in a concentration of from 1 to 30% by weight of water in the slime.
Upon the action of reagents, the protective film stabiliz ing the slime particles is oxidized and the slime structure is broken. As a result, pure yellow phosphorus is obtained along with a small amount of phosphoric acid and a solid residue. The resultin~ pure phosphorus is collected and combusted by a con-ventional method to give phosphoric acid.
These prior art methods, however, have the following disad-vantages: formation of substantial amounts o~ liquid wastes containing a suspension of solid particles, weak phosphoric and sulphuric acids, chromium salts or chromic acid; pollution of en~ onrnent the onv~-ro~ments with the accumulated liquid wastes; high cost of chromium compounds employed in the process and irrevocable losses thereof.
GDR (German Democratic Republic) Patent No. 54677 of March 20, 1967 teaches the treatment of a phosphorus slime with a~ alkali. IR doing so, abo~t 30% of phosphorus contained in the slime is converted to a poisonous gas phosphine, while the re-maining part of phosphorus remains in the form of a black, stron-gly contaminated phosphite solution (Na2HP03). This prior art method has a disadvantage residing in the formation o~ large .

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amounts of phophine which should be further entrapped, as well as the formation of solid and liquid wastes polluting the environment. While effective methods exist for process-ing of "thick" slimes, there are still no such methods for processing of "thin" slimes.
Known in the art are numerous methods for process-ing the off-gases resulting from the manufacture of phosphorus by way of trapping phosphine therefrom by using various ab-sorption solutions. These absorption solutions contain CuCl, FeCl HCl~ HgC12+ HCl~ H2S04 + Na2Cr2o7, H2S04 ( 4 2 4 NaC102 + C12, NaC102 + bleaching powder; HN03, HN03 + AgN03, AsC13, FeC13, KMnO4 and the like.
US Patent No. 2,673,885 teaches a method for puri-fication of the gases in a counter-current scrubber, which comprises washing of the gases with chlorinated water contain-ing 0.3 to 1 g/l of chlorine.
Among the above-mentioned absorption solutions such solutions as CuC1, FeC12, HCl, HN03, FeC13 have a small absorp-tion capacity with respect to phosphine. Solutions containing HgC12+ HCl, AsCl~ or NaC102 + bleaching powder are poisonous or evolve a poisonous gas, i.e. chlorine. The solution con-taining HN03 + AgN03, though quite efficient, is rather ex-pensive .
The products obtained with the use of said solutions do not find any use, they are discarded as wastes and pollute the environment.

~' ~13~Z335 Despite a ~reat number of patents and other publications in the art there are no cheap, effective methods for process-ing o~ "thin" slimes and off-gases resulting from the manufac-ture of phosphorus which would make full utilization of all A the products of such processing; neither there are~cheap methods for utilization of Cottrell dust or phosphorite fines. For this reason, at the present time processing of "thin" slimes, entrapp-ing of phosphine and phosphorus particles from off-gases, a mo-re rational utilization of Cottrell dust and phosphorite fines constitute an urgent but still unsolved problem.
It,is the main object of the present invention to protect e,~ On,~
the onvironmcnto from pollution with harmful wastes resulting from the production of elemental phosphorus.
It is another object of the present invention to provide a method for processing of wastes resulting from the production of phosphorus which would make it possible to simultaneously convert to useful products both slime and the off-gases.
Still a~other object of the present invention is to provide a method for processing slimes and the off-gases resulting from the production of phosphorus which would make it possible to substantially eliminate waste products.
It is a further object of the present invention to provide such a method for processing of wastes resulting from the pro-duction of phosphorus which would make it possible to make use of Cottrell dust and phosphorite fines to give a useful product.

It is a still further object of the present invention to provide a method enabling processing, to useful products, of "thin'~ slimes, i.e. slimes containing phosphorus in an amount below 35~0 by weight.
It is an object of the present invention to ensure utili-zation of all the products resulting from said processing of slimes and of~-gases from the production of phosphorus.
In accordance with the present invention, the method for processing of wastes from the production of phosphorus, i.e.
slime and off-gases, comprises treatment of said wastes with an aqueous solution of copper sulphate, followed by separation of a solid product containing mainly copper phosphide as well as fluorides, chlorides of alkali metals and silicon, calcium and aluminium silicates, from a liquid product containing phos-phoric and sulphuric acids and copper sulphate which are utili-zed.
In accordance with the present invention, copper sulphate concentration in the solution is varied within the range of from 15 to 50% by weight, dependinæ on what is treated, i.e.
slime or the off-gas.
It is advisable to use, for the slime processing, an a~ueous solution of copper sulphate with a concentration of A' from 30 to 50% by weight, since within this vo-~ range most ef-ficient processing conditions are ensured. At concentrations of .

~3l32335 the copper sulphate solution above 50% by weight the result-ing solid residue entrains too much copper ions. This causes difficulties during washing of the residue with pure water and necessitates a high consumption rate of pure water. With concentrations of the solution of copper sulphate below 30%
by weight large volumes of water are required for processing of the slime; in addition, the process duration is increased.
Taking into account these factors, optimal concentrations of copper sulphate for processing of the slime are cencentrations varied within the range of from 30 to 50% by weight.
For processing of the off-gases it is advisable to use aqueous solutions of copper sulphate with a concentration of from 15 to 20% by weight containing an additive of chlor-ides of an alkali metal or ammonium, or fluorides, bromides or iodides of an alkali metal. It is preferable that said addi-tive be used in an amount of from 0.5 to 1% by weight.
Upon introduction of chlorides of lithium, potas-sium, sodium or ammonium into said solution, entrapping of phosphine and phosphorus particles from the off-gas is in-creased up to 93-95% of their content in said off-gas. Flu-orides, bromides or iodides of the same metals act in the same manner, but it is preferable to use chlorides of sodium and ammonium, since those are cheaper and more readily available. The presence of said additive in the solution of copper sulphate accelerates the formation of a solid precipi-tate during the treatment of the off-_g_ -gases. Where a solution o~ copper sulphate is used without said additive, a solid precipitate is formed 30 'lO minutes after the start of the treatment, whereas in the presence of said additives a solid precipitate is formed already after 15 minutes a~ter the start of the treatment. It is likely that said additives act as a catalyst.
As ~ar as the solution of copper sulphate intended for processing of the slime is concerned, there is no necessity of introducing said additive thereinto, since the solid phase of the slime already contains a sufficient amount of fluorides and chlorides of an alkali metal (2 to 8% by weight) which act as a catalyst. ~he process of treatment o~ the slime and off--gases by means of a solution of copper sulphate is conducted at a temperature within the ra~ge o~ from 20 to 80C. It is within this particular range that the best results are attained.
~hough the process can be conducted at a temperature above 80 C, this is undesirable due to difficulties associated with filtra-tion and discharging of the solid product, since the evolving vapour is detrimental for the sanitary a~d hygienic conditions o~ labour. It is undesirable to conduct the process at a tempe-rature below 20C, though it is quite possible, because the pro-cessing time is increased.
Phosphorus and phosphine contained in the off-gases as well as phosphorus contai~ed in the slime react with the solu-tion of copper sulphate according to a complicated multi-stage _ mechanism. In a generalized form this interaction may be characterized by the reactions:

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1) P4 ~ Cu2+S04 + E20--~Cu3P3 ~ H3P5~o4 + H2S04

2) P3 H3 ~ Cu2~SO~ + H20 -i~ Cu3P3 ~ H3P5+o4 ~ P4 ~ H2S04 As a result of reactions (1) and (2) copper phosphide Cu3P is formed which is the principal compound of the solid pro-duct.
Therewith, into the solid product those solid inorganic components are passed without any changes which are contained in the off-gases and slime, i.e. fluorides and chlorides of alkali metals and silicon, calcium and aluminium silicates, carbon black. Said compounds in the solid product are determined by X-ray analyæis, crystallo~optic analysis, metallographic and chemical analyses~
In accordance with the present invention, processing of the slime and the o~gases resulting from the production of phosphorus b~ means of an aqueous solution of coper sulphate is accompanied by the formation of two useful products, i.e. a so-lid product and a liquid one.
The solid product contains mainly cuprous phosphide~ and a certain amount o~ ~luorides, chlorides of an alkali metal and of silicon; silicates of calcium a~d aluminium, while the li-quid product contains sulphuric acid, phosphoric acid and cop-per sulphate.

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~ he present invention provides for utilization of said products. It has been found that said solid product can be successfully employed as a modifying agent and ra~ination agent for posteutectic silumines. It should be noted in this respect that the product is used without any additional purification.
Eurthermore, the solid product can be u~ed for the manufacture of a copper-phosphorus alloy.
The liquid product may be used for the manufacture of a va-luable copper-containing potassium-phosphorus fertilizer.
~ he present invention makes it possible to condu~t the processing of wastes from the production of phosphorus, i.e.
slime and of~-gases, without the formation of secondary wastes.
I~ other words, the method according to the present invention makes it possible to trans~orm the production o~ phosphorus to a wasteless production which is advantageous from the point of view of environment protection and which is the main merit of the present invention.
The method for processing of wastes resulting from the production of phosphorus in accordance with the present invention is rather simple, economically efficient ,A does not requre high does rates of power consumption, nor expensive reagents; neither~it req~,Y`e -req'u-i~e~ a~y special equipment.
~ he method according to the present invention stipulates utilization of all the resulting products with simultaneous utilization of other wastes resulting from the production of -phosphorus, such as Cottrell dust and phosphorite fines. All this in itself makes the method according to the present in-vention commercially profitable compared to the prior art methods for processing of wastes resulting from the production of phosphorus.
These and other advantages of the present invention will be now more fully apparent from the following detailed description.
A detailed description of the present invention is given hereinbelow with reference to the accompanying drawing, wherein a principal scheme of processing of wastes from the production of phosphorus is shown which illustrates the treatment of the slime and off-gases into useful products.
Copper sulphate is fed from bin 1 into tanks 2 and

3, into which water is also supplied. In said tanks 2 and 3 a solution of copper sulphate of a required concentration is prepared under stirring. The resulting aqueous solution of copper sulphate from the tank 2 is passed into a reactor 4, while from the tank 3 the solution is fed into an absorber 5 provided with a sphere-type packing. Into the reactor 4 the slime is fed via the line "a", while into the absorber 5 the off-gas is passed via the line "b" counter-currently with respect to the solution.
In the reactor 4 copper sulphate reacts, under stirring, with the slime components to give a liquid product and a solid one. The solid product contains mainly copper phosphide as well il3~335 as metallic copper, copper phosphate, cupric and cuprous oxides, fluorides and chlorides of alkali metals and silicon, calcium and aluminium silicates, and carbon black. The li-quid product contains phosphoric acid, sulphuric acid and a certain amount of copper sulphate.
In the absorber 5 copper sulphate reacts with the off-gas components which results in the formation of the solid and liquid products. The solid product contains mainly copper ~hosphide as well as metallic copper, cuprous phosphate,cupric and cuprous oxides, carbon black, fluorides and chlorides of an alkali metal and silicon, calcium and aluminium silicates.
The latter pass into the solid product from the dust contained in the off-gas. The liquid product contains phosphoric acid, sulphuric acid and a certain amount of copper sulphate. The off-gases purified from phosphine, phosphorus and dust are evacuated from the absorber 5 via the line "c" and employed as a fuel or as the starting stock for the manufacture of a crude solid carbon dioxide.
The pulp consisting of the solid and liquid products is fed, from the reactor 4 and absorber 5, onto a filter 6, wherein these products are separated; the solid residue is washed with water and delivered into a bin 7, from which it is discharged via the line "d". After drying, the solid product is of a commercial grade and is delivered to a user.
The filtrate resulting after separation of the solid phase is delivered from the filter 6 into a collector 8, ~,,, from which it is fed into the tanks 2 and 3 for a repeated use, i.e. for dissolution of a fresh portion of copper sul-phate. As a result of the repeated use of the liquid product, the concentration of phosphoric acid and sulphuric acid therein is increased. After a repeated use the liquid pro-duct is collected in a collector 8 and delivered to a vessel 9.
In the vessel 9 the liquid product, when required, is adjusted so as to obtain a copper-containing potassium-phosphorus fertilizer therefrom. From the vessel 9 the liquid product is delivered to a tank 10, into which Cottrell dust is fed via the line "e" under stirring. (This is the dust which is deposited on electric filters upon passing of gases therethrough and contains up to 22% by weight of P205 and up to 15% by weight of K20). The resulting pulp from the tank 10 is delivered into a mixer 11, wherein it is mixed with the phosphorite flour supplied via the line "f". The phosphorite flour may be prepared from phosphorite fines which is a waste product from crushing of phosphorite ores and which, as a rule, is not processed but discarded, thus polluting the environment. The mass produced in the mixer 11 is delivered to a storage 12, wherein it is kept for 15 to 20 days for maturation. The thus-obtained product from the storage 12 is discharged via the line "g" and further subjected to a treat-ment similar to that employed for matured superphosphate.
As a result, a copper-containing potassium-phosphorus ferti-lizer is obtained. The gases containing SiF4, HF, C02 are delivered from the apparatus 10, 11, 12 to the common system of purification from fluorine and compounds thereof lnot shown).
Therefore, the liquid product resulting from pro-cessing of slimes and off-gases in accordance with the pre-sent invention is used along with other wastes from the pro-duction of phosphorus, i.e. Cottrell dust and phosphorite flour to yield a fertilizer containing copper and potassium.
This fertilizer is a valuable fertilizer for numerous plants growing on peaty soils. In this manner the liquid product is completely employed.
As has been mentioned hereinbefore, the solid pro-duct can be used as a modifying and refining agent for hyper-eutectic silumines. Hypereutectic silumines are aluminium alloys containing silicon in an amount of more than 11.6%
by weight. The modification-and-refining process is performed in the following manner. A hypereutectic silumine is melted at a temperature within the range of from 820 to 900C and 0.4 to 0.8% by weight of said solid product is added thereto at this temperature. Therewith, modification and refining of the alloy occurs. This may be further illustrated by the following.
Copper phosphide contained in the solid product reacts with aluminium with the formation of a large number of seeds AlP according to the reaction:

Cu P + Al -~ AlP + CuA12 (3) ~;

~13~335 ~ he seeds of AIP serve as crystallization cen ~erS
for silicon grains which would be smaller than grains of si-licon crystallized without the seed of AlP.
~ hen, chlorides and ~luorides of alkali metals and sili-con, including Na2SiF6 and Na2~iC16 contained in the solid pro-duct for gaseous fluorides and chlorides at a temperature of from 820 to 900C which, evolving from the melt, contribute to its refining. The decomposition occurs in accordance with the reactions as follows:

Na2SiF6 + Al -~- AlF~ + ~a~ ~ Si~ + Si (4) Na2~1Cl6 + Al -~- AlC13 + NaCl + SiC14 + Si (5) A ~e~;n;r1g The -ro~t components of the solid product do not take part in the reactions and come up to the metal surface as a slag.
The modified and refined silumine is further employed for the manufacture of foundry articles (such as pistons for internal--combustion engines).
Besides, said solid product can be used ~or the producti-on of a copper-phosphorus alloy. ~o this end, the solid product is melted at a temperature within the range of from 1,050 to 1,150C in an inert medium. ~wo layers are formed therewith, namely: the upper and lower ones. 'rhe lower layer comprises a melt of copper and phosphorus (phosphorus content is 7 to 13%) which is easil~ poured into crystallization moulds. ~he upper 1~32335 layer comprises a slag which is in the form of a glass-like substance containing fluorosilicates of metals and can be used as a flux in soldering or melting of non-ferrous metals.
For a better understanding of the present invention some specific Examples are given hereinbelow with reference to the accompanying drawing; Examples 1 to 5 illustrate the method of processing the ~lime and off-gases of the production of phos-phorus, while Examples 6, 7 and 8 illustrate utili~ation of the resulting products.
Example 1 This Example illustrates processing of the slime resul-ting from the production of phosphorus along~ with the prepara-tion of useful products.
In a tank 2 at the temperature o~ 20C there are prepared 100 litres of a 40% solution of copper sulphate. ~rom the tank a ;~l ~o ~h,ch A 2 the solution is delivered into a reactor 4, ~hcrcinto under constant stirring there are added 10 l of a phosphorus slime with the specific gravit~ of 1.25 and with the ~ollowing compo-sition~'per cent by weight: P 25.0; total ~ + Cl 5.3; total SiO2 ~ A1203 ~ Fe203 35.9; CaO 4.9; MgO 0.5; C 2.1; Na20 0.8;
K20 1.0; water being the balance. As a result of' interaction between the reagents two products are ~ormed, i.e. a liquid pro-duct and a solid one which are separated in a ~ilter 6. ~he so-lid product is washed on the filter and delivered into a bin 7 for the f`inal solid product, while the liquid product is col-lected in a collector vessel 8. ~he weight o~ the resulting so-- 18 _ , ' ;' ~:

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1~32335 lid product is equal to 12.5 kf, it contains in per cent by weight: P 13.3, Cu 55.0; total F ~ Cl 6.1, Si 2,2; Al 1.2;
total Na + K 1.2; total Ca ~ Mg 3.4, C l.l; 2 being the balance. Phase analysis of the solid products has shown the presence of the following phases, namely: copper phosphide Cu3P, copper phosphate, metallic copper, cuprous oxide, cupric oxide fluorides and chlorides of sodium, potassium and sili-con, silicates of calcium and aluminium, carbon black. The product comprises a black or dark-brown powder.
The liquid product contains 40 g/l of H3P04, 300 g/l of H2S04 and 2.8 g/l of Cu ion. This liquid product from the collector vessel 8 is again delivered to the tank 2 for dissolution of a new portion of copper sulphate to treat another portion of the phosphorus slime. After separation of the solid product, the filtrate repeatedly produced in the collector vessel 8, i.e. liquid product, contains 105 g/l of H3P04~ 550 g/l of H2S04 and 3-2 g/l of Cu ion.
The results illustrating processing of the slime with a solution of copper sulphate at various temperatures and concentrations are given in Table l hereinafter.

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It follows from Table 1 that the duration of the inter-c~Pf~
action of the solution of cuprous sulphate and the slime is lowered with increasin~ temperature. ~herewith, the major part of phosphorus from the slime is passed into the liquid product in the form of phosphoric acid which results in an increased yield thereof. The amount of phosphorus in the solid phase is reduced. The temperature ~or the slime processing is selected depending on what product is to be obtained in a larger quantity.
Thus, if it is desired to obtain a greater amount of phosphoric acid in the liquid product, then the slime processing should be conducted at a temperature within the range of from 70 to 80C.
At temperatures below 20C it is undesirable to perform process-ing of the slime, since the process duration would be rather long.Furthermore, at low temperatures ~uS04 5H20 is sparingly soluble.
It also follows from Table 1 hereinbefore that processing Cc~pP~ r of the slime can be performed by means of a solution of oupro~
sulphate in concentrations above 50% (60% solution) with equally good results. However, a concentration of the solution above 50% is undesirable due to the fact that the solution becomes very saturated and this has a detrimental e~fect upon the pro-cessing time (which is increased) and washing of the solid pro-duct ~rom copper ions (which are difficult to wash-of~). At a 20% concentration of ~w~Y~ sulphate the process duration is 60 minutes instead of 30 minutes for a 30% solùtion.

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Increased duration of the process results in a lesser out-put from the reactor 4. Reduced concentration of the solu-tion below 30% results in an increased consumption of water.
For the above-mentioned reasons, optimal concentrations of the solution of copper sulphate for processing of the slime should be varied within the range of from 30 to 50% by weight.
Example 2 This example illustrates processing of the off-gases resulting from the production of phosphorus with the preparation of useful products. In a tank 3 at the tempe-rature of 40C there are prepared 100 1 of an aqueous solu-tion of copper sulphate with the concentration of 20% by weight containing 0.5% by weight of sodium chloride. From--the tank 3 the solution is passed into an absorber 5 with a sprayed suspended spherical pac~ing. From the lower part of the absorber 5 the off-gas is fed counter-currently to the solution stream via the line "b". The off-gas compo-sition is varied with in the following range in per cent by volume: C0 83-89, H 0.9-4; CO2 1-3, H2S 0.4-0.8, phos-phine PH3 1-1.5 g/sm3, amount of phosphorus particles 1-4 g/sm3, supply rate of the off-gas is 4.000 m3/hr. Total phosphorus content in the gas samples taken before and after passing thereof through the absorber 5 is determined by che-mical analysis, the content of phosphine is determined chromatographically. According to data obtained from these analyses, upon passing the off-gases of the above-mentioned composition through said solution of copper sulphate at the temperature of 40C the solution entraps 93D/o of phosphine and 90YO of phosphorus particles.

,, -As a result of interaction of the gas com-ponents with the solution of copper sulphate there are formed solid and liquid products which are separated in a filter 6. The solid product is fed into a bin 7, while the liquid product into a collector vessel 8. The solid product has the following composition in per cent by weight:
P 9.9, Cu 75.2, total F + Cl 3. 2 ~ Si 4.2, Al 0.5, total ~a + K 0.1, total Ca ~ Mg~1.4, C 0~3~ 2 being the balance.
The liquid product, after a single passage through the absorber 5, contains 40 g/l of H3P04, 180 g/l of H2S04, 170 g/l of CUS04. From the collector vessel 8 the liquid product is passed into the tank 3, wherein its composition is corrected (adjusted) to the 20% concentration of copper sulphate,- though without sodium chloride. From the tank 3 the solution is again passed into the absorber 5.
After a repeated cycle of the process of treating the off-gas, the liquid product has the following composition:
75 g/l of H3PO4 ~ 270 g/l of H2S04 and 190 g/l of CuSO4.
Upon a repeated treatment of the off-gas with the solution 20 the latter entraps 91% by weight of phosphine and 89% by weight of phosphorus particles. Therefore, the solution of copper sulphate with the addition of 0.5% of sodium chlo-ride substantially totally catches phosphine and phosphorus particles.
The gases purified from phosphine and phos-phorus are withdrawn from the absorber 5 via the line "c"
and used as a fuel.
Example 3 This Example is given to illustrate selection of an optimal concentration of the solution of copper sul-1~233~

phate with the addition of 0.5% of sodium chloride forcatching phosphine and phosphorus particles from the off-gases. The process is conducted as described in the fore-going Example 2. Use is made of solutions with the con-centration of 10, 15, 20 and 25% by weight of copper sul-phate respectively with the addition of 0.5% of sodium chloride at the temperature of 40C. The results obtained have shown that the optimal concentration of copper sulphate in the solution for the treatment of the off-gases is 15 to 20% by weight. The data thus-obtained are shown in Table 2 hereinbelow.

Relationship between the amount of entrapped phosphine and phosphorus particles from the off-gases vs. the concentration of copper sulphate Concentration of copper Percentage of entrapping sulphate in the solution per cent by weightPhosphine phosphorus 1~32335 Example 4 This ~xample is given by way of illustration of the in-corporation of additives of alkali metal halides or ammonium ~of 're~
into the solution of oupr~u~ sulphate. The process is conducted in a manner similar to that described in the foregoing Example C Op~ ~r 2~ Into a 20% solution of cup~s sulphate at the temperature of 40C are addsd 1% additives of chlorides o~ alkali metals, ammonium as well as bromides~ fluorides and iodides of an alka-li metal. The results obtained have shown that the addition of chlorides, fluorides, bromides and iodides of an al~ali metal or ammonium enhance the absorption capacit~ of the solution of -cup-rou~ sulphate which makes it possible to effectively puri~y the off-gas. The data illustrating this processing of the off--gas are shown in Table 3 hereinbelow.
Table Relationship between entrapping of phosphine and phosphorus particles from the off-gases vs. the nature of additive ~ _ . . _ _ _ . _ , . . _ . _ . . _ _ Additive taken in Percentage of entrapping the amount of 1% by ----- --- --- -- -- ---weight phosphinephosphorus ..~
LiCl 95 91 ECl 92 94 NaCl 94 92 - ~5 -~ ..

ll~Z335 KBr 86 89 NaF 92 93 It is obvious that halides of other alkali metals will have the same or similar effect, but they are rather expensive as are fluorides, bromides and iodides of metals. For this reason, it is preferable to use chlo-rides of alkali metals and ammonium.
Example 5 This Example is given by way of illustration of the effect of the quantity of chlorides of sodium and ammonium in the solution of copper sulphate on the absorp-tion of phosphine and phosphorus particles from the off-gases. The process is conducted in a manner similar to that described in Example 2 hereinbefore. As a solution for absorption of phosphine use is made of a 20~ solution of copper sulphate with the addition of sodium chloride or ammonium chloride taken in different amounts. The data obtained are shown in Table 4 hereinafter.

Table 4 _ Relationship between absorption of phosphine and phospho-rus particles from the off-gases vs. concentration of the additives .. .. . _ _ _ Additive, per cent Percentage of entrapping by weight --~
phosphine phosphorus ~ . _ . __ v .. . .. ._ _ __ 0.~ 82 89 NaCl -5 93 9 1.0 94 92 2.0 94 92 5.0 93 91 0.1 79 85 NH4Cl 89 90 1.0 93 95 2.0 92 94 5.0 93 92 As follows from Table 4~ increased concentration of the addit ve above 1% does not result in a higher d.egree of catching~phosphine and phosphorus particles. At a concentration of the additive of 0.1% and belowJthe absorption capacit~ o~

the solution is reduced. For this reason, optimal concentra~
tions o~ said additives should be varied within the range of ~rom 0. 5 to 1% by weight.
Example 6 This Example illustrates the possibility of utilization of the solia product as prepared in Example 1 herein before as a modification and refining agent for hyp~Kutectic silumines.
~he modification and refining process is carried out in the h~e~ e/J~e~
following manner. A hypoeutootio silumine of the composition~r per cent by weight: silicon 20,0; copper 1.5; nickel 1.0; man-ganese 0.7; magnesium 0.3; aluminium the balanceJtaken in the amount of 220 kg is melted in a furnace and maintained at the temperature of 840 ~ 10 C. Then 0.9 kg of the solid product, i.e. 0.4% by weight is added into the melt. Therewith, on the surface of the metal there is observed the formation of gas bubbles consisting of Si~4, Al~3 and AlC13 which refine the silumine. Completion of the refining process is determined b~
the discontinuation of evolution of gas bubbles. ~he thus-mo-dified and refined silumine has been tested for its charac-teristics. '~here are measures tensile strength ~ (kgf/mm2), elongation ~ (%), Brinnel hardness HB (kgf/mm2) and porosity -- number of pores in 1 cm2 of the surface. The results thus obtained are shown in Table 5 hereinbelow. Also shown in Table 5 are data obtained after addition of ~.32 kg (0.6% by weight) and 1.76 kg (0.8~ b~ weight) of the solid product.

~ , 1~3~335 For the purpose of comparison, shown in Table 5 are also the properties of a hyp~neutectic silumine modified by means of a conventional modifying agent, i.e. cuprous phosphide Cu3P of the "pure" grade containing 13.0% of phosphorus and ~5.2% by weight of copper.
Table_~
Effect of the modif~ing agent amount on properties of a hype~eutectic silumine No. Modifying Mechanical properties Porosity agent, ~
per cent ~ 2 ~ HB 2 number of pores by weight kg~mm ~0 kg/mm in cm~
.~
1. Solid product of Example 1:
0~4 16 0.7 115 15 0.6 18 0.7 116 10 0.8 20 '7 115 10 2, Copper phosphide 0.4 14 0.5 110 20 0.6 15 0.5 110 20 0.8 16 0.5 110 20 ~ rom the data shown in the above Table 5 it follows that after processing of the hyp~utectic silumine with the solid product obtained in accordance with the present invention, its - 29 _ '' : :
~, ~

,~ :

mechanical strength is increased by 10-15%, percent of elonga-tion is also increased, while gas porosity is redu~ed as com-pared to the data obtained with the use of Cu3P. Metallographic anal~sis has shown that the size of grains o~ silicon in the hy~eutectic silumine modified by the solid product of the pre-sent invention and by Cu~P is 10 to 20 mcm, while that of the non-modified silumine is 80 to 100 mcm. Taking into consideration the fact that the solid product according to the present inven-tion is used without purification and that it has been prepared from wastes, production costs of the modified and refined product are reduced by 4-5 times.
~xample 7 ~ his Example illustrates the opportunity of utilization o~ the solid product as prepared in Example 2 hereinbefore for the manufacture of a copper-phosphorus alloy therefrom. The so-lid product taken in the amount of 12.5 kg is brought i~to a crucible which is in tur~ placed into an apparatus provided with a pipe for admission and discharge of argon. ~he apparatus is placed into a ~urnace. The product is heated to the tempera-ture of 1,100 ~ 50C. The solid product is molten with evolution of Si~4 which is entrained with the inert gas and absorbed by a solution of NaOH. No evolution of phosphorus vapours is observed.
After cooling of the molten solid product two layers are formed, namely: the upper layer and the lower one. ~he uppex one com-prises a slag, while the lower layer is an alloy copper-phos-`,,~

;

:
:

1~3Z335 phorus. ~he slag is separated ~`rom the casting. The casting o~
the alloy copper-phosphorus has its weight of 9.6 kg and con-sists of 84.1% by weight of copper and 10.7% by weight of phosphorus, impurities being the balance. ~he thus-produced alloy of copper and phosphorus can successfully replace the same alloy produced by other methods in all applications the-reof (as a deoxidizing agent ~or copper alloys, as a component of copper solder). The thus-produced allo~ of copper and phos-phorus is well-castable. The slag a~ter solidification has a glass-like appearance, it has a good adherence to metals and cleans them from oxides. For this reason it may be used as a flux for soldering or melting of non-ferrous metals.
Example 8 This Example illustrates utilization of the liquid product as prepared in ~xample 2 hereinbefore for the preparation of a potassium-phosphorus fertilizer.
'~he liquid product collected in the vessel 9 and having the ~ollowing composition: 75 g/l of H3P04, 270 g/l o~ H2S04, 1go g/l of CuS04 is adjusted to the content o~ H3P04 of 110 g/l and that of X2S04 od 620 g/l. Afterwards, the thus-prepared so-lution is passed into the vessel 10, whereinto under constant stirring Cottrell dust is portionwise added via the line "e"
till a pulp is ~ormed with a density of from 1.40 to 1.45. ~he Cottrell dust contains 25% o~ P205, 10~o 0~ K20 and 1% o~ phos-phorus fines. Upon ~'ormation of the pulp, phosphorus particles 113Z~;~5 which are entrained with the Cottrell dust are "neutralized" by the solution of copper sulphate with the formation of Cu3P. Said pulp from vessel ~0 is fed into a mixer 11, wherein it is mixed with phosphorite flour containing 22% by weight of P205 taken in the excess of 15% over its stoichiometric amount and which is supplied via the line "f". The resulting mass is deli~ered from the mixer 11 to a storage 12, wherein it is kept for matu-ration for 15 days under periodic agitation.
The degree of decomposition of phosphorite flour is as high as 92%. From the storage 12 the formed copper-containing potassium-phosphorus fertilizer is discharged via the line "g~".
The content of P205 in the resulting fertilizer is 32.5%, includ-ing the content of assimilated P205 equal to 30.1%; content of K20 is 3.5~0, Cu2~ 4.8% b~ weight. The thus-obtained fertilizer is a commercial product.

Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of processing wastes resulting from the production of phosphorus, namely slime and off-gases, compris-ing treatment of said wastes with an aqueous solution of copper sulphate, separation of the resulting solid product containing mainly copper phosphide and chlorides, fluorides of alkali metals and silicon, silicates of calcium and aluminium, from the liquid product containing sulphuric acid, phosphoric acid and copper sulphate.

2. A method as claimed in claim 1, wherein use is made of a solution of sulphate with a concentration within the range of from 15 to 50% by weight.

3, A method as claimed in claim 1, wherein for the treatment of the slime use is made of a solution of copper sulphate with a concentration within the range of from 30 to 50% by weight.

4. A method as claimed in claim 1, wherein for the treatment of the off-gases use is made of a solution of copper sulphate with a concentration of from 15 to 20% by weight.

5. A method as claimed in claim 4, wherein for the treatment of the off-gases use is made of a solution of copper sulphate containing a halide of an alkali metal or ammonium.

6. A method as claimed in claim 5, wherein for the treatment of the off-gases use is made of a solution of copper sulphate containing an alkali metal or ammonium chloride.

7. A method as claimed in claim 5, wherein use is made of a solution of copper sulphate containing 0.5 to 1% by weight of said alkali metal or ammonium halide.

8. A method as claimed in claim 1, wherein the treatment of said slime and off-gases is conducted at a temperature within the range of from 20 to 80°C.