DE1165555B - Process for the recovery of hydrogen sulfide and ammonia from scrubbing liquids for gases - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Class: C Ol b

German class: 12 i- 17/16

Number: 1165 555

File number: S 67783 IV a / 12 i

Filing date: March 29, 1960

Opening day: March 19, 1964

The invention relates to a process for the recovery of hydrogen sulfide and ammo niac from washing liquids for gases, the ammonium salts contain the oxygen acids of sulfur.

When exhaust gases are washed with ammoniacal liquids, what is present in the gas combines Sulfur dioxide with the ammonia in the liquid with the formation of ammonium sulfite and ammonium bisulfite, about one third of that in the due to oxidation of the liquid Liquid present sulfur occurs in the form of ammonium sulfate, and the rest of the sulfur ammonium sulfite, ammonium bisulfite and ammonium thiosulfate are present in approximately equal parts. If the washing liquid containing these ammonium salts of the oxo acids of sulfur then by application Treated by heat and pressure, ammonium sulfate and elemental sulfur become educated.

The process according to the invention has set itself the task of recovering sulfur and ammonia from the washing liquids, the ammonia as ammonia solution, that of the washing device is fed back, and to recover the sulfur in the form of hydrogen sulfide.

The erfmdungsgemäße method is characterized in that the washing liquid is introduced into a flash evaporator at a temperature of about 800 ⁰ C and the decomposition products then with a mixture of carbon monoxide and hydrogen over a bauxite catalyst at a temperature of 400 to 600 ⁰ C can be reduced, the reaction mixture condensed and the condensate is distilled to separate the hydrogen sulfide from the ammonia liquid. Here, the catalyst is preferably maintained at a temperature of 450 to 55O ⁰ C. The space velocity of the sulfur oxides through the catalyst is here 5 or less.

The vaporizer can be heated by burning some of the reduced gases inside and the Liquid can be injected into the combustion flame. The space velocity in the reduction vessel should not be greater than 250.

In order to convert sulfur dioxide and sulfur trioxide in the decomposition products in hydrogen sulfide, which decomposition products can be conducted from the evaporation stage through a bed of hot coke in the reaction vessel, wherein the coke bed is to be kept at a temperature of 800 to 900 ⁰ C. In this conversion, the space velocity should not be chosen to be greater than 150; the processes for the recovery of hydrogen sulfide and ammonia from scrubbing liquids for gases

Applicant:

Simon-Carves Limited, Stockport, Cheshire (Great Britain)

Representative:

Dipl.-Ing. H. Seiler, Berlin 19, Oldenburgallee 10 and Dipl.-Ing. H. Stehmann, Nuremberg 2, patent attorneys

Named as inventor:

Peter Simpson, Stockport, Cheshire, Manfred Landau, Sale, Cheshire, Kenneth Hope,

Todhunter, Northenden, Manchester (Great Britain)

Claimed priority:

Great Britain of April 9, 1959 (No. 32 301) - -

According to the invention, the temperature of the reaction vessel itself is 950 to 1000.degree.

When carrying out the process according to the invention, the ammoniacal liquids are completely evaporated and the ammonium salts decomposed according to the following equations:

Equation 1:

(NH ^ ₂ SO ₃ -> 2 NH ₃ + H ₂ O + SO ₂ equation 2:

NH ₄ HSO ₃ → NH ₃ + H ₂ O + SO ₂

Equation 3:

(NH ₄ ) ₂ S ₂ O ₃ - * ■ 2 NH ₃ + H ₂ O + SO ₂ + S

Equation 4:

(NHJ ₂ SO ₄ - * 2 NH ₃ + H ₂ O + SO ₃

The evaporation is carried out by injecting the liquid into a flash evaporator, which is kept at a temperature of about 800 ° C. It is essential that the temperature does not drop to 650 ⁰ C in this process stage, otherwise the evaporation unit through the

409 539/452

speed in the reduction vessel can then be reduced to 250, so as to reduce the dilution effect of the nitrogen to overcome the air and also to the effect of that formed by the combustion Carbon dioxide to overcome the equilibrium of equation 8. The internal heating also causes the Overcoming the heating problems in the evaporator also has the effect of reducing ammonia losses to be reduced because nitrogen comes from the air

ammonium bisulfate paste formed according to the following equation is contaminated:

Equation 5:

(NH ₄ ) ₂ SO ₄ → NH ₄ HSO ₁ + NH ₃

The decomposition products are fed from the evaporator to a reduction stage in which the
Sulfur dioxide and the sulfur trioxide are reduced to hydrogen sulfide. This reduction can
can be carried out in various ways. One of the reasons for the speed of implementation according to equation 9 is the use of reduced.

ornamental gases, d. H. by means of mixtures of when using solid carbon containing

Carbon monoxide and hydrogen. Such gases as reducing agents are easily evaporated in the form of luminous gas or water gas to the liquid in the same way, as is the case with the use of the reducible, or the same can be the case in larger quantities of ornamental gas. The gases are produced by known gasification processes and then passed through a bed of the reducing agent. Another embodiment to achieve this
the reduction consists in passing the steam through one
Bed of solid carbon-containing material, such as
Coke to pass through.

When using reducing gases, the gases leaving the evaporator with the reducing Gases mixed and then passed through a catalyst bed of bauxite beads. It is

which usually represents coke at a temperature of 800 ° C. Here the following implementations occur a:

Equation 10:

H, 0

Equation 11

CO + H, O

CO + H ₂

CO ₂ + H ₂

known per se, a bauxite catalyst at 500 ° C for equation 12:

To use conversion of sulfur dioxide with hydrogen. In the method according to the invention the following reactions occur when carried out by the catalyst:

SO ₂ + 3 H ₂

H ₂ S + 2 H ₂ O

equation 6:
SO ₂ + 3 H ₂ -> H ₂ S 4_ 2 H ₂ O equation 7:
SO ₃ -j-4 H ₂ -> · H ₂ S + 3 H ₂ O equation 8th:
CO + H ₂ o -> CO ₂ equation 9:

2NH ₃

N,

3H ₂

Equation 13:

SO ₃ + 4 H ₂ -> H ₂ S r 3 H ₂ O In order to achieve the complete conversion of the sulfur oxides, a total space velocity of 150 must not be exceeded. Under these conditions, large amounts of the water vapor are converted into water gas in accordance with the reaction according to equation 10, the amount of hydrogen formed being significantly higher than that required for equations 12 and 13. It can be up to _75/0 of the converted present in the liquid water for applications of doors temperature of 950 to 100O ⁰ C in the reaction vessel in water Gas °, wherein the gas after carrying out the method used for heating the evaporator.

The following after each of the optional

To do the conversions according to equations 6 and 7
to be carried out quantitatively, the catalyst must be at
a temperature within a range of 450
to 550 ^c C are maintained and the space velocity (ie the gas volume at 25 ⁰ C per minute per 45 given embodiments of the process volume of packed bed obtained) of the sulfur oxides, exit gases consisting of a mixture of water must not exceed 5. Under these conditions proceeds
the implementation according to equation 8 is also quantitative.

The decomposition of ammonia due to the

steam, hydrogen sulfide, ammonia, carbon monoxide, carbon dioxide, hydrogen and nitrogen. The cooling of these gases leads to a condensation reduction according to equation 9 under these loading 50 of the steam, of ammonia, of Schwefeldingungen not more than 15 ° / ₀ of the total ammonia hydrogen and a portion of the Kohlendioxydes, niaks. The condensate contains all of the ammonia and

Around a space velocity of 5 for practically all of the hydrogen sulfide and will To achieve sulfur oxides, it is necessary, then by means of known distillation processes in Space velocity of the total in the reaction vessel 55 an ammonia solution and hydrogen sulfide limit incoming gases to 520. This changes. That which remains after the condensation

Gas consists of a mixture of hydrogen, carbon monoxide, carbon dioxide and nitrogen. if the amount of nitrogen is low, the mixture can do so

liquid is unusual that the same more than 60 are used to heat the vaporizer, or Contains 7 moles of ammonia per liter, it rarely occurs; a space velocity of less than 500 passing gas can be mixed depending on becomes necessary. the embodiment in question, with which the use of reducing gases is applied, can be operated. When the nitrogen levels are high the evaporator is inside by burning a 65, the gas is discarded.

represents a numerical value, which, however, varies slightly with the composition of the solution to be treated will fluctuate. However, since there is a

Part of the reducing gas is heated in the same and the liquid is injected into the flame. In this case the entire space velocity should

Suitable, for example, flow diagrams for the optional embodiments of the invention are shown in the drawings.

F i g. Fig. 1 is a flow chart showing the application of a reducing gas and internal heating of the evaporator indicates;

F i g. Figure 2 shows the application of a hot coke reduction unit.

As shown in Fig. 1, becomes ammoniacal Washing liquid, which contains about 6 moles of ammonia per liter and 4 moles of sulfur per liter, from the wet cleaner 1 led into the evaporation unit 2, which in a known manner at a temperature of 800 ° C ίο will hold. In the evaporator 2 is together with an amount of air from a pump 4 of reducing gas introduced into the evaporator 2 from a gas container 3. Those evaporated in the evaporator mixed Gases then enter the reaction vessel 5, which is at a temperature of 450 to 550 ° C is maintained. The units 2 and 5 are enclosed in a common casing in order to so to keep heat losses to the outside as small as possible.

The gas leaving the reaction vessel 5 consists of a mixture of ammonia, hydrogen sulfide, nitrogen, water vapor, carbon dioxide and small amounts of hydrogen and carbon monoxide. The same is passed through a waste heat boiler 6, which cools the gas of a temperature from 450 to 500 ⁰ C to a temperature of 100 to 110 ° C.

The gas then passes through a condenser 7 in which the water vapor, ammonia and hydrogen sulfide be condensed. The remaining gas, which for the most part consists of nitrogen and carbon dioxide exists, is returned to the wet cleaner 1 via the line 8, so as to reduce the amount of residual material from the same Recover amounts of hydrogen sulfide.

The condensate passes through the line 9 to the distillation device 10 and is known in the art Way converted into ammonia solution, which is returned to the wet cleaner 1 via line 11. The hydrogen sulfide set free in the distillation device is via line 13 to the Claus furnace 12 performed, in which the hydrogen sulfide in the presence of supplied by the pump 14 Air is burned to sulfur. The gases emerging from the furnace 12 become the wet cleaner 1 recycled through line 15 so as to recover all in the exiting gas stream to cause the sulfur gases present.

According to the FIG. The embodiment shown in FIG. 2 is the one emerging from the wet cleaner 1 Liquid supplied to the evaporator 2, which is heated by an external gas furnace 3. They evaporated Gases enter the reaction vessel 5 and are ■ from here through a waste heat boiler 6 to the condensation!

Sator 7 supplied, in which water vapor, hydrogen sulfide and ammonia are condensed. That Residual gas enters the gas furnace 3 via line 8, in which the same is burned to heat the evaporator. The ammonium sulfide liquid will then led to the distillation device 10, in which the same in ammonia solution and hydrogen sulfide is converted. These reaction products are then treated in the same way, as is the case with regard to FIG. 1 has been described.

If one of the two embodiments explained above the method according to the invention is used in an ammonia gas wet cleaner, The effort for wet cleaning can be reduced by returning the ammonia solution to the wet cleaner can be significantly reduced, as this results in the maintenance of the operation of the wet cleaner required amount of fresh ammonia is reduced. This is particularly evident in those Cases where synthetic ammonia is used.

Claims (4)

Patent claims: 1. A process for the recovery of hydrogen sulfide and ammonia from ammonium salts of the oxygen acids of sulfur-containing scrubbing liquids for gases, characterized in that the scrubbing liquid is introduced into a flash evaporator at a temperature of about 800 ^° C. and the decomposition products are then mixed with a mixture of carbon monoxide and hydrogen a bauxite catalyst at a temperature of 400 to 600 ° C, the reaction mixture is condensed and the condensate is distilled for the purpose of separating the hydrogen sulfide from the ammonia liquid. 2. The method according to claim 1, characterized in that the catalyst is maintained at a temperature of 450 to 55O ⁰ C. 3. The method according to claim 1 and 2, characterized in that the decomposition products so be passed through the catalyst that the space velocity of the sulfur oxides 5 or is less. 4. The method according to claim 1, characterized in that the decomposition products from the flash evaporator are passed through a bed of coke kept ^{at a temperature of 800 to 900 0 C for reduction.} Considered publications:
Gmelin's Handbook of Inorganic Chemistry, I. Edition, Volume Schwefel, Part B, 1953, p. 263. 1 sheet of drawings 409 539/452 3. 64 © Bundesdruckerei Berlin