United States Patent 9) 11, 3,935,100 Alagy et al. (45) Jan. 27, 1976

54) PROCESS FOR THE TREATMENT OF l,557, 88 10/1925 Newlands...... 20153 WASTE WATERS CONTAINING SULFURIC 1959,305 5/1934 Rentschler...... 423 fliS8 2,094,902 10/937 Muller ...... 4231554 ACID AND/OR AMMONUM SULFATE 2,863,732 12/1958 Bowers et al...... 20/50 X (75) Inventors: Jacques Alagy, Lyon; Christian 3,784,680 l/1974 Strong et al...... 4231554 X Busson, Rueil Malmaison; Maurice Cessou, Communarg, all of France (73) Assignee: Institut Francais du Petrole, Paris, Primary Examiner-Thomas G. Wyse France Attorney, Agent, or Firm-Millen, Raptes & White (22) Filed: June 28, 1974 21 ) Appl. No.: 484,228 (57) ABSTRACT (30) Foreign Application Priority Data Process for treating a waste water containing sulfuric June 29, 1973 France...... 73.2427 acid and/or ammonium sulfate comprising (1) react Dec. 4, 1973 France ...... 73.433 18 ing said water with sulfide to form barium sul Mar. 6, 1974 France ...... 7408095 fate, (2) reacting the latter with carbon containing in organic impurities, at high temperature, thereby form 52 U.S. C...... 210,45; 210/47; 210/48; ing , at least a major portion of which is 210/50; 423/158 recycled to step (1), and a gas which is separated, (3) (51 Int. Cl.’...... C02B 1134; CO2C5/06 dissolving in water a minor portion of the barium sul 58) Field of Search...... 210/42, 45, 47-53, fide produced in step (2), separating the insoluble im 210/63, 67, 71; 423, 158, 166, 170,554 purities therefrom and recycling at least one portion of the resulting purified solution to step ( ). (56) References Cited UNITED STATES PATENTS 24 Claims, 4 Drawing Figures 62404 5, 1899 Jacobs ...... 423 ft 70

U.S. Patent Jan. 27, 1976 Sheet 1 of 4 3,935,100

22 FG.1 U.S. Patent Jan. 27, 1976 Sheet 2 of 4 3,935,100

F.G.2 51

5 l

1 2 12 34 33

3 O 42 S 3

P. t. 39

15 44

4. O-20 26 47 24 U.S. Patent Jan. 27, 1976 Sheet 3 of 4 3,935,100

FG.3 22 23 46 45

31 25 (2) 30

21 40 28

5 17. 32 1 2 12

42 "... 39 11 U.S. Patent Jan. 27, 1976 Sheet 4 of 4 3,935,100

3,935,100 1 2 from the insoluble impurities contained therein and (5) PROCESS FOR THE TREATMENT OF WASTE transferring at least one portion of the resulting puri WATERS CONTAINING SULFURIC ACID AND/OR fied solution to step (1). AMMONUM SULFATE BRIEF DESCRIPTION OF THE DRAWINGS In the course of numerous chemical operations and The invention is illustrated by the accompanying various treatments, solutions of sulfuric acid are used. drawings: The waste waters from said operations are polluted by FIG. 1 is a schematic flow diagram illustrating a first organic and inorganic impurities and by free sulfuric embodiment which may be used when treating rela acid whose concentrations are variable to a large ex O tively dilute sulfuric acid containing waste water; tent. FIG. 2 is a modification of the diagram of FIG. 1 The discharge of these waste waters resulting in a concerning the treatment of two different streams of pollution of waters, difficult problems have to be solved sulfuric acid containing waste water. by the industry in order to comply with more and more FIG. 3 is a modification of the diagram of FIG. 1 severe regulations in this field. As a matter of fact, this 15 concerning the treatment of relatively concentrated water cannot be sent to the plants usually used for the sulfuric acid containing waste water. treatment of waste waters, due to the presence of sulfu FIG. 4 is a modification of the diagram of FIG. 3 ric acid. The neutralization by CaO, as carried out in concerning the treatment of ammonium sulfate con numerous plants, requires to solve the problem of the taining waste water. discharge of the formed CaSO4. Other waste waters 20 contain ammonium sulfate. DETALED DESCRIPTION OF THE DRAWINGS According to a first embodiment, waste water is re SUMMARY acted in a first step with barium sulfide (BaS). The The object of this invention is to provide a general latter may be used, for example, as a powder or in method for treating such waste waters irrespective of 25 solution or suspension in water or in a gas. We prefera their origin and their concentration. This method per bly proceed with a slight shortage of barium sulfide mits to recover and recycle sulfur. It is particularly with respect to SO so that the pH during the oper convenient for treating waste waters of low sulfuric ation and particularly at the outlet of the neutralization acid content, for example from 1 to 40 percent by reactor is maintained between 3 and 7 and, preferably, weight. These waters may also contain soluble sulfates, 30 between 4 and 6. The reaction is preferably conducted for example ammonium sulfates or various metal sul in a stirred reactor in order to completely exhaust the fates. introduced BaS and to maintain in suspension the The optimum concentration being from 10 to 30 formed BaSO. The substantially pure percent b.w. , when various waste waters of different hydrogen sulfide (HS) produced by the reaction may origin are available, it is possible by admixing them, to be converted in a burner to (SO) which adjust the sulfuric content of the resulting mixture. can be used for example for manufacturing sulfuric When the total concentration is greater than 30 per acid. The HS may also be converted to sulfur, for cent by weight, we can proceed to a dilution by recy example by the Claus process. The precipitation of cling a portion of the treated water. However, in a BaSO may be conducted under atmospheric pressure particular embodiment, the treated waters contain 20 40 or super atmospheric pressure and at Toom tempera to 40 percent by weight of sulfuric acid or ammonium ture or a higher temperature. The residence time is sulfate. usually from 0.1 to 1 hour. A very significant parame The present process makes use of the known reaction ter of this reaction is the pH at the outlet of the reactor of reduction of barium sulfate to barium sulfide by which must be maintained below 7 in order to limit as means of carbon. It has however been observed that 45 much as possible the amount of soluble Ba, irrespective this process was difficult to carry out. For example, the of its form, in the medium and, preferably, to a value insoluble impurities accompanying the treated waters lower than 10 ppm by weight corresponding to the or resulting from the reacted materials, have the effect solubility of BaSO in water. of progressively reducing the efficiency of the process. In a second step, the resulting barium sulfate suspen Moreover, it has been observed that the gaseous efflu 50 sion in water is fractionated, for example filtrated with ents obtained at various points of the installation could or without filtration aids or dried or centrifuged. The not be discharged as such in the atmosphere, in view of solid precipitate consisting mainly of BaSO4, but also their polluting action. possibly, of other organic and inorganic impurities, is The present process provides an economical way of advantageously washed with water. solving these difficulties. 55 In a third step, this precipitate is intimately admixed The invention concerns a process for treating a waste with carbon possibly containing in organic impurities, water containing sulfuric acid and/or ammonium sul for example coal or coke or, preferably finely crushed fate, comprising the steps of : (1) reacting the waste petroleum coke. This mixture is treated in an oven water with barium sulfide, introduced at least partly in where BaSO is reduced at high temperature by the the solid state, so as to form a suspension of solid bar 60 carbon to BaS according to a well known process. We ium sulfate in waste water, (2) reacting the resulting proceed for example at a temperature of from 700 to barium sulfate at high temperature with carbon con 1 500°C. During this operation, the organic impurities, taining inorganic impurities so as to form solid barium if any, are incinerated and the inorganic impurities, as sulfide containing inorganic impurities) and a gas well as the coal ashes, are removed from the system by which is separated, (3) recycling to step (1) at least the 65 purging a portion of the produced BaS. At least the major portion of the formed solid barium sulfide and major portion (more than 50 percent) of the produced (4) dissolving in water a minor portion of solid barium BaS is recycled to the neutralization reactor. The sulfide from step (2), separating the resulting solution purged BaS fraction is defined by the amount of inor 3,935,100 3 4 ganic impurities, particularly ashes, to be removed about 16.9 T/h. The neutralization of HSO, by BaS is from the system and by the stationary concentration conducted under controlled pH, the latter being main compatible with a good operation of the oven. This tained at a value of at most 6. The average residence fraction is, for example from 5 to 30 percent by weight. time in the reactor is 0.25 h. in these conditions, the in a fourth step the purged BaS is treated with water, BaS attack is substantially complete. Through line 21, preferably at a temperature of 70-80°C, in order to 3.2 T?h of HS evolve which are subsequently con dissolve substantially all the BaS. The inorganic impuri verted to SO, in the burner 22. The formed SO, is fed ties insoluble in water, such as the gangue of BaSO, ore through line 23 to the sulfuric acid manufacturing unit. and the coal ashes and a few insoluble Ba compounds The suspension formed in reactor 5 contains 23.3 tons such as BaCO and BaCO, are removed, for example O of BaSO, and, in addition, impurities which are insolu by filtration or centrifugation. The resulting filtrate, ble in water in substantially neutral medium and which containing BaS is, at least partly, recycled to the neu are found, on the one hand, in the treated water and, on tralization reactor. The residue may be discharged. the other hand, in the barium sulfate discharged from However, in some cases, it may be interesting to react the oven in which is carried out the BaSO reduction. the same with a solution of HCl before its discharge in 5 This suspension is conveyed through line 4 to the order to recover Ba in the form of BaCl, which can be liquid-solid separator 7 consisting, for example, of a subsequently treated by HSO, to form BaSO, which is filter. The filtration is facilitated by the use of incinera recycled to the oven, and to regenerate HCl, which is ble filtration aids, for example having a cellulose or a recycled. porous coal base. The resulting filtrate (line 15) is very In a preferred additional stage, the fumes evolving 20 slightly acid and contains less than 10 ppm of soluble from the oven, are subjected to dust-removal in dry Ba in the form of BaSO. conditions by means of cyclones or other devices com This filtrate contains from 2 000 to 3 000 ppm of monly used for dry-dust removal and for washed with a dissolved HS which can be removed by stripping with portion of the purified water. The so-washed fumes air introduced into tower 43 through line 47. The air contain H.S, SO, CO,etc... and may be advanta 25 effluent (line 44) containing more than 98 percent of geously oxidized for converting HS to SO, they can be the HS of the water, is sent to incinerator 28. The subjected to a final purification before being dis water free from the major portion of the HS may then, charged. This purification may be advantageously car if necessary, be sent through line 26 to the water purifi ried out according to the process described in the cation station of the plant in order to be subjected to a French patents: No. E.N. 72 34076, No. E.N. 72 30 finishing treatment. 32342. For this purpose, the SO, contained in the The solid residue obtained on filter 7, after admixture gaseous effluent from the incinerator is washed out by with the necessary coal amount and additional BaSO. means of an aqueous solution of ammonium sulfite through line 16, is sent through line 6 to the reduction and for ammonia. The effluent gas usually contains less oven 13 where BaSO is reduced to BaS at a tempera than 300 ppm of SO. The liquid effluent from the 35 ture of 100"C. At the outlet from the oven 18.8 T/h collector is treated by means of a BaS solution. The of BaS in the solid form. admixed with solid impurities precipitated Ba salts (mainly Ba sulfite and sulfate), such as unreacted coal, BaCOs, BaO, gangue due to the after filtration, are fed to the oven for reduction of the coal, etc... are recycled in major portion to the reactor sulfates. The filtrate is introduced into a distillation or S through lines (8-9-12). About 2 T?h of BaS (line 10) stripping tower in order to obtain a top fraction consist 40 are dissolved in a dissolution reactor 19 with 10 T/h of ing of a mixture of steam, NH and HS and a bottom filtrate coming from line 14. fraction consisting of water having a reduced (NH),S The effluent is conveyed through line 11 to filter 20. content and which can be directly discharged. H.S after After drying and washing in the unit 20, the mother oxidation to SO, is fed to reactor 41 through line 25 of liquors are returned to reactor 5 through line 13 and F.G. 1. The amount of HS contained in line 25 corre 45 the residue is discharged through line 24. The gases sponds to one half by moles of that contained in line 33. issued from the oven (line 17) are subjected to a dust Sulfur is produced at the bottom of the reactor (line removal in dry conditions followed with a washing with 32). The ammonia solution condensed at the top of the water in a wet washer. The so-washed gases contain, in . reactor is recycled through line 31 to the gas washer addition to the inert gases N, and CO, about 2 to 3 40. The purified water line 15 discharged from filter 7 SO percent of the total sulfur introduced by HSO, in the contains 2 000 to 3 000 ppm of dissolved HS which form of HS and SO. These gases are supplied through must be removed before rejecting the water. This re line 17 to the incinerator 28 and then through line 27 to moval can be achieved in a tower by stripping with air, the above-mentioned fume treatment unit. For this according to a preferred embodiment of this invention. purpose, the fumes are treated in the gas washer 40 by The air outflow from the tower, containing more than 55 means of an ammonia solution introduced through line 98 percent of the HS of the water, is conveyed through 31. The purified fumes, containing less than 300 ppm line 44 to the incinerator 28. by volume of SO, may be rejected to the atmosphere through line 30. The solution of ammonium sulfite and EXAMPLE 1 (FIG. 1) sulfate obtained from the bottom of the washer (line The feed through line 1 consists of 32.7 T/h of waste 60 29) is treated in a stirred reactor 35 by means of a BaS waters containing 30 percent by weight of HSO and solution coming from line 34. The mixture of BaSO. suspended solids, i.e. 9.8 T/h of H,SO, (100 kmoles). and BaSO obtained after filtration 36, which amounts This waste water is so diluted as to contain 15 percent to 2.5 T/h, is conveyed through line 38 to the oven 18. by weight of HSO, by recycling 32.6 T/h of filtrate The resulting ammonium sulfide solution (line 37) is through line 3. The so-diluted waste water is intro 65 distilled in tower 42. We obtain, from the bottom of the duced into the neutralization reactor 5 through line 2. tower, through line 39, waste water which can be re The same reactor is also fed through line 12 with a jected and, at the top, from line 33, HS, NH and water suspension of BaS in water having a BaS content of vapor which are transferred to reactor 41 in order to

3,935,100 5 6 produce sulfur (line 32) by reaction with a correspond The different modes of operation of the invention in ing amount of SO, fed through line 45. this particular case, will be illustrated by examples 2 to This SO, is obtained by combustion in the incinerator 4. The flow sheet is that of FIG. 2. 46 of a small portion (line 25) of the HS produced in The plant will be operated as in the first mode of reactor 5. The ammonia solution obtained by conden 5 operation of the invention except that a portion of the sation of the top effluent from reactor 41 is recycled waste sulfuric waters will be sent to reactor 48. through line 34 to collector 40. In view of making easier the understanding of the The performance of the process of the invention is specification, the three examples relate to the same sometimes made difficult when the waste sulfuric wa hourly feeding rate of the absorber 40 with 100 moles ters contain impurities producing, during the reaction O of SO, through line 27. with barium sulfide, an evolution of gaseous com The ammonia hourly flow rate through line 31 is such pounds accompanying the main HS gaseous effluent. that the resulting sulfitic liquor contains 50 moles of The further use of the HS may be thus jeopardized, ammonium hydrogen sulfite and 50 moles of di depending on the nature of the impurities accompany ammonium sulfite. ing it. These impurities may be, for example, HCl, 15 The stoichiometrical reaction taking place in the metal chlorides or hydrocarbyl halides. absorber, may be written : This inconvenience may be avoided in a second 100 SO, + 150 NH + 100 H.O - 50 NHH SO + mode of operation of this invention. 50 (NH)SO In this second mode, we proceed to a preliminary This basic case is not to be considered as a preferred selection of waste sulfuric waters of different origins 20 embodiment and has been given only for illustrative and we feed the zone of reaction with barium sulfide purpose. In particular, any other ratio between the only with those waste waters which, by reaction with sulfite and the hydrogen sulfite can be used as well. BaS, do not produce compounds impeding the subse EXAMPLE 2 quent operations. 25 To the sulfitic liquor recovered from the bottom of The complementary portion of the waste sulfuric absorber 40, containing 50 moles of NHH SO and 50 waters, which may or not contain impeding impurities, moles of (NH)SO, we add 50 moles of HSO in the is fed to a reactor intermediate between the SO, ab form of waste sulfuric waters containing impeding in sorber and the reactor for converting ammonium sul purities, introduced through line 49. fite to barium sulfite. In this intermediate reactor, sul 30 The reaction taking place in the intermediate reactor furic acid reacts with ammonium sulfite with produc (48), gives a mixture of ammonium sulfate and ammo tion of SO. The SO, evolved during this reaction is nium hydrogen sulfite according to the stoichiometrical conveyed to the enclosure where is carried out the reaction: reaction between H.S and SO, in view of producing So NHH SO + 50(NH)SO + 50 HSO - S0 elemental sulfur, 35 SO, + 50 (NH),SO -- 50 NHH SO + 50 HO According to some preferred operating conditions The resulting aqueous solution is fed to reactor 35 which will be specified later, the SO, amount thus fed where it is reacted with the stoichiometrical amount of to this intermediate reactor may contribute to reduce BaS according to the reaction : 50 (NH)SO + 50 NHH SO + 100 BaS -) 50 Ba or even avoid the independent production of SO, by SO + 50 Ba SO + 50 (NH), S + 50 NH, HS HS combustion. The respective amounts of the two 40 After filtration or centrifugation in separator 36, the separate flows of waste sulfuric waters may vary within resulting liquor is subjected to a decomposition in reac a wide range, the only condition being that the total tor 42, according to the reaction : amount of the waste sulfuric waters which may give rise 50 (NH)S + 50 NHHS - 150 NH + 100 HS to contaminents of HS be included in the feed of the The so-produced gases are fed to reactor 41 where intermediate reactor. 45 they react with 50 moles of SO, coming from reactor FIG. 2 illustrates the performance of this technique. 48 through line 50, thereby producing 150 moles of The equipments denoted with references (1) to (47) sulfur recovered from the bottom of reactor 41 and fed are the same as in FIG. 1 and, accordingly, it will not to the absorber so as to close the ammonia cycle. normally be made reference to them. The total equation of these reactions may be written The intermediate reactor referenced 48 and placed 50 : on line 29, is fed with waste sulfuric water containing 2 SO, + HSO + 2 BaS - Ba SO, + Ba SO + HO impeding impurities, through line 49, while other less -- 3 S polluted sulfuric waters are treated in reactor 5. This The barium salts are fed to the reduction oven 18 so reactor is fed with an aqueous solution of ammonium as to regenerate the barium sulfide required for the sulfites through line 29 and, in some cases, with addi 55 reaction. As reducer, we use coke containing 10 per tional ammonia from line 52. The outflow from this cent b.w. of ash and 2 percent b.w. of surfur. reactor consists of an aqueous solution containing am EXAMPLE 3 monium sulfates and sulfites (duct 29a connected to To the sulfitic liquor of example 2, we add 150 moles reactor 35) and of a gaseous effluent of high SO, con of HSO containing impeding impurities. The follow tent (duct 50). In some operating cases, particularly 60 ing reaction takes place in reactor 48 : when the production of SO, duct 50 is sufficiently high 50 NHH SO + 50 (NH)SO + 150 HSO -> 100 with respect to that of HS (line 33) to comply with the SO, + 150 NHH SO, + 100 H.O stoichiometry of the reaction between H.S and SO, in SO, evolves and the obtained solution is treated with reactor 41, it will be needless to incinerate HS in reac BaS : 65 150 NHH SO + 150 BaS - 150 Ba SO, + 150 tor 46. When the production of SO, is higher than the NHHS stoichiometry, it will be not only convenient to omit the After centrifugation, the solution is heated so as to incineration 46 but also the additional HS will be sent liberate HS and NH : to reactor 41 through line 51. 150 NH H S - 150 NH + 150 HS 3,935,100 7 8 The amount of produced HS is not sufficient for Moreover, this third mode of operation of the inven stoichiometrically reacting with SO, from line 50. Ac tion has a very particular advantage in the case of waste cordingly 50 moles of additional HS are fed through waters containing ammonium sulfate without free sul lines 21, 25, 51, 45. 300 moles of sulfur are thus pro furic acid. In this case, no gas evolves from the neutral duced in reactor 41. The ammonia is fed to absorber ization reactor. The SO, amount required by the reac 40, thus closing its cycle. tion in order to produce elemental sulfur is then ob The total equation of these reactions may be written tained in a known manner, for example by sulfur com bustion. 2 SO, + 3 HSO + 3 BaS + HS -> 3 Ba SO, + 4 The third mode of operation concerns particularly HO + 6 S 0. the treatment of waste waters whose concentration of The barium sulfate is converted to barium sulfide as sulfuric acid and/or ammonia sulfate is substantially indicated in example 2. high, for example about 20 to 40 percent by weight and EXAMPLE 4 optionally containing soluble organic impurities which do not react with barium sulfide or react with the same To the sulfitic liquor of example 2, we add 300 moles 5 by producing soluble organic compounds and/or inor of HSO, containing impeding impurities. The follow ganic impurities. ing incomplete reaction should have then to take place When the sulfuric acid and/or ammonium sulfate 50 NHH SO + 50 (NH,),SO + 300 HSO, - 100 concentration is too high and exceeds about 40 percent SO, + 100 H.O + 150 H,SO, + 150 NH.H SO, by weight, it is convenient to dilute the feed charge if fed to reactor 35, this strongly acid liquor is liable 20 with water. Such water may be advantageously taken to lose HS in this reactor. In order to avoid this incon from the purified effluent at the outlet of the treatment venience, a portion of the recycled ammonia is fed to unit. reactor 48 through line 52. The ammonia amount to be The mechanical design of the reactor is substantially added for neutralizing the sulfuric acidity is 50 moles different from that herein before recommended: as a of NH3. The total stoichiometrical reaction in reactor 25 matter of fact, the high apparent viscosity of the semi 48 can thus be written : solid paste resulting from the chemical reaction and the 50 NHH SO + 50 (NH) SO + 300 HSO, + 150 necessity of obtaining a sufficient homogeneity of the NH, -9 300 NHHS O, + 100 SO, + 100 H.O composition and of the temperature while permitting By reaction with BaS, we obtain : 300 NHH SO + 300 BaS --> 300 Ba SO, + 300 the evolution of HS as completely as possible, make it NH H S 30 necessary to use malaxing devices such as axial mixers BaSO is reduced to BaS by means of coal and the with Archimede screw, planet mixers, z. mixers, etc. aqueous solution of NHH S is decomposed by heating The further treatment of this semi-solid paste is dif as follows : ferent according to the fact that the waste waters con 300 NHH S - 300 NH + 300 HS tain or not ammonium sulfate. Finally, the ammonia will be found partly at the inlet 35 When the waste sulfuric waters do not contain or of the absorber 150 moles and partly at the inlet of the only contain negligible amounts of ammonium sulfate, reactor 48 150 moles. The ammonia thus closes its the paste issued from the mixer-degazifier reactor 5 is cycle. At that time, HS is in excess with respect to SO, directly conveyed to the oven 18 for reduction of Ba and it will be convenient to produce the lacking SO, by So... The subsequent steps of the treatment are the incinerating a portion of the HS which is fed to incin 40 same as hereabove described. The complete flow sheet erator 46 through line 25. The required SO, amount is is given in FIG. 3. The organic impurities accompany 50 moles. ing BaSO are destroyed in the oven 18, partially incin It has been mentioned above that the process of the erated in the oven itself or rejected with the gases. invention could be used for treating waste sulfuric wa These gases are fed to the incinerator 28 together with ters containing from 1 to 40 percent by weight of sulfu 45 air from duct 62 ensuring the conversion of the sulfur ric acid. However, in the case of high concentrations, it containing compounds to SO, and the complete incin was necessary to dilute the waste water by means of a eration of the organic impurities. filtrate produced in the step of filtration of Ba SO, When the waste waters contain ammonium sulfate in produced by reaction of BaS with sulfuric acid, it has substantial amount, wheter or not free sulfuric acid is been observed that, for sulfuric acid concentrations 50 still present, it is observed that the treatment carried from 20 to 40 percent by weight, it was not only useless out in reactor 5 has converted the ammonium sulfate to to recycle a portion of the filtrate, but that, in addition, ammonium sulfide. the filtration step could be completely omitted, thereby For recovering the ammonium sulfide, a modification resulting in a considerable simplification of the treat of the flow sheet in conformity with FIG. 4 is necessary. ment with the substantial advantages resulting there 55 In view of recovering the ammonium sulfide con from. This constitutes a third mode of operation of the tained in the paste, the latter is fed to a stove 53. We invention, proceed, either by indirect heating, performed, for As a matter of fact, it has been observed that it was example, by means of tubes heated with steam or by difficult to remove from the filtrate produced by filtra direct heating, for example by means of steam or hot tion of the barium sulfate obtained by reacting sulfuric 60 gases, to the removal of the ammonium sulfide in the acid with barium sulfide, the soluble organic impurities form of HS and NH. This operation can be performed already present in the starting material or produced by continuously or batchwise in a single stove or in several the reaction of initially present organic impurities with stoves in series. the reactants. Said removal of the soluble organic com The operation may consist only in the removal of pounds would require a costly complementary treat 65 ammonium sulfide but it may also be conducted so as ment. By using the third mode of operation of the in to completely dry the paste issued from reactor 5. vention, it is possible to completely avoid this inconve The paste having a variable degree of dryness is sub nience. sequently fed, in a known manner, to the reactor 18 for 3,935, 100 9 10 reduction of Ba S.O. 4. A process according to claim 1 in which the aver The vapors evolving from the stove 53 through line age reaction time of step (a) is from 0.1 to 1 hour. 54 essentially contain NH, H.S and variable amounts 5. A process according to claim 1 in which the gas of steam. formed in step (b) is subsequently treated with a gas Preferably these vapors will be subjected to a partial containing free oxygen for converting the hydrogen condensation 55, 56; the condensate line 58 will be fed sulfide contained in said gas to sulfur dioxide. to stripper 42 and the uncondensed fraction line 57 will 6. A process according to claim 5 in which the gas feed reactor 41. it is however possible to directly supply formed in step (b), before treatment with a gas contain these vapors to reactor 41 through line 60. ing free oxygen, is subjected to dust removal and/or A portion of the ammonia recovered at the top of O washing with water. reactor 41, will be reused in the form of an aqueous 7. A process according to claim 5 in which, after solution in view of absorbing SO, in the absorber 40 conversion of hydrogen sulfide to sulfur dioxide, the The exceeding portion will be withdrawn from the gas is washed with an aqueous solution of ammonium system through line 59 in the form of an aqueous am sulfite and/or ammonia, to dissolve the sulfur dioxide monia solution containing traces of ammonium sulfide. s and obtain a solution of ammonium sulfite and/or bisul When the charge contains ammonium sulfate without fite. free sulfuric acid, the lines 21, 23, 25 and the units 22 8. A process according to claim 7 in which the ob and 46 can be omitted. The sulfur dioxide necessary for tained solution of ammonium sulfite and/or bisulfite is the reaction taking place in the reactor 41, may be reacted with an aqueous solution of barium sulfide to introduced through line 45. It is produced, for example, 20 produce insoluble barium sulfites and/or sulfates and a by sulfur combustion. residual aqueous phase containing hydrogen sulfide The water necessary for dissolving BaS in the reactor and ammonia, and separating said insoluble barium 19 is taken from duct 39, through duct 63. Through sulfites and for sulfates from said residual aqueous duct 61, it is possible to dilute the waste waters when phase. their concentration is too high. 25 9. A process according to claim 8 in which the bar These examples have been successfully repeated with ium sulfites and/ or sulfates are recycled to step (b). other materials under claimed conditions. For example 10. A process according to claim 8 in which the resid coals or cokes containing or producing from 0.1 to 20 ual aqueous phase is subjected to distillation or strip percent b.w.of ash (such as SiO, iron oxides, calcium ping with an inert gas, to obtain a hydrogen sulfide- and and iron silicates, or silicate and the like). 30 ammonia-containing gas. According to a preferred embodiment, there is used 11. A process according to claim 10, in which the highly sulfurized coke (S content of about 1-15 % hydrogen sulfide and ammonia-containing gas is re b.w.) which is normally valueless but which yields her acted with the sulfur dioxide produced according to gaseous sulfur compounds (HS and SO) which are claim 22. useful to the process: they are discharged through pipe 35 12. A process according to claim 1 in which, after 17 and converted in reactor 28. step (a), at least one portion of the waste water is sepa We claim: rated from the solid barium sulfate, the latter is fed to 1. A process for treating waste water containing sul step (b) and the separated waste water is treated with furic acid and/or ammonium sulfate, comprising the an air stream, so as to carry away the hydrogen sulfide steps of: (a) reacting the waste water with ash-contain 40 contained therein, the resulting gas, containing free ing solid barium sulfide recovered from the following oxygen, being then heated in order to convert the hy step (c) and with an aqueous solution of barium sulfide drogen sulfide to sulfur dioxide. recovered from the following step (e), to form a sus 13. A process according to claim 1 in which waste pension of ashcontaining solid barium sulfate in the water of other origin, containing sulfuric acid, is fed to waste water at a pH of 3 - 7, the proportions of said 45 an enclosure in which said waste water is contacted solid barium sulfide from step (c) and said barium with an aqueous solution of ammonium sulfite so as to sulfide supplied as solution from step (e) being respec form gaseous sulfur dioxide and an aqueous solution tively 70 - 95 percent and 5 - 30 percent of the total containing ammonium sulfate, said solution being sub barium sulfide, (b) reacting the resulting barium sulfate sequently treated with barium sulfide so as to form with coal or coke containing 0.1 - 20 percent b.w. of 50 insoluble barium salts and ammonium sulfide, the bar ash, at 700°- 1500°C, to form ash-containing solid ium salts being used in step (b), the ammonium sulfide barium sulfide and a gas containing HS and SO, which being decomposed by heating to a gaseous mixture of is separated, (c) recycling to step 1 at least the major hydrogen sulfide and ammonia, said mixture of hydro portion of the ash-containing solid barium sulfide gen sulfide and ammonia being subsequently reacted formed in step (b), and (d) admixing water with a 55 with sulfur dioxide to produce elemental sulfur with minor portion of the ash-containing solid barium sul evolution of ammonia. fide formed in step (b), thereby obtaining a barium 14. A process according to claim 13, in which the sulfide solution and insoluble ash, separating said bar waste water of other origin fed to the enclosure for ium sulfide solution from said insoluble ash and (e) being contacted with an aqueous solution of ammo recycling at least one portion of the barium sulfide 60 nium sulfite, is waste sulfuric acid containing water, solution obtained in step (d) and separated from the capable of generating, by reaction with barium sulfide, ash to step (a). gaseous compounds which contaminate hydrogen sul 2. A process according to claim 1 in which the waste fide and jeopardize its further use. water contains from 1 to 40 percent by weight of sulfu 15. A process according to claim 13, in which the ric acid. 65 amount of sulfuric acid present in said waste water of 3. A process according to claim 1 in which the pH of other origin, exceeds the amount necessary for ensur the barium sulfate suspension at the end of step (a) is ing the evolution of all the potential SO, contained in from 4 to 6. the aqueous solution of ammonium sulfite, so that the 3,935, 100 11 12 formed aqueous solution containing ammonium sulfate elemental sulfur by reaction of hydrogen sulfide with sulfur dioxide. also contains sulfuric acid. 20. A process according to claim 18, in which said 16. A process according to claim 15, in which ammo separated gas containing steam, ammonia and hydro nia is added to said aqueous solution containing ammo gen sulfide is subjected to partial condensation for nium sulfate and sulfuric acid, the amount of ammonia removing water there from, the uncondensed vapors being sufficient to convert said sulfuric acid to ammo being reacted with sulfur dioxide to produce elemental nium bisulfate. sulfur. 17. A process according to claim 1 in which, during 21. A process according to claim 1 wherein the step (a), waste water containing about 20 to 40 percent 10 treated waste-water contains sulfuric acid, whereby by weight of sulfuric acid and for ammonium sulfate is hydrogen sulfide is formed in step (a) and is separated treated with powdered barium sulfide to form a wet from the suspension of solid barium sulfate in the semi-solid paste containing a high proportion of BaSO4, waste-Water. which is fed in totality to step (b). 22. A process according to claim 21, wherein at least 18. A process according to claim 17, in which the 5 a portion of the hydrogen sulfide separated from the waste water supplied to step (a) contains ammonium suspension of solid barium sulfate in the waste-water is sulfate, whereby the semi-solid paste obtained by reac reacted with oxygen to produce sulfur dioxide. tion of said waste water with barium sulfide contains 23. A process according to claim 1 wherein the ash of ammonium sulfide produced by reaction of ammonium said coal or coke contains silicium dioxide, iron oxide, sulfate with barium sulfide, and said semi-solid paste is calcium silicate, iron silicate, barium oxide or barium heated to produce a gas containing steam, ammonia silicate. and hydrogen sulfide, and said gas is separated from the 24. A process according to claim 1 wherein the ash of semi-solid paste. said ashcontaining solid barium sulfide contains unre 19. A process according to claim 18, in which said acted coal, barium carbonate, barium oxide or gangue separated gas containing steam, ammonia and hydro 25 fron coal. gen sulfide is admixed with sulfur dioxide to produce st k k k k

30

35

40

45

50

55

60

65