DD255720A1 - METHOD FOR OBTAINING PURE HYPERMICANTS AND / OR CARBON DIOXIDE-CONTAINING AMMONIA WATER - Google Patents

Abstract

The invention includes the thermal recovery of pure ammonia from hydrogen sulfide and / or carbon dioxide-containing ammonia water. The process should be designed so that a supply of pure water for the separation of the inert gas-ammonia mixture and the ammonia wash is not required. This is achieved by passing after the distillative Entsaeuerung the reprocessed ammonia water or part of it in countercurrent to the inert gas-ammonia mixture. Another part of the deaerated ammonia water is used to wash the ammonia removed in the thermal ammonia output. The enriched ammonia water coming from the inert gas-ammonia separation is fed to the thermal ammonia stripping, and the ammonia water coming out of the wash, after a large part of the ammonia has been expelled, is fed to distillative deaeration. The invention is used in the processing of effluents incurred in petroleum and coal refinement.

Description

For this 1 page drawing

Field of application of the invention

The invention is used in the treatment of waste water, which are obtained in petroleum and coal refinement. The ingredients contained therein, such as ammonia on the one hand, hydrogen sulfide and / or carbon dioxide on the other hand, are recovered in separate form.

Characteristic of the known technical solutions

In coal and petroleum upgrading often occur polluting wastewater containing ammonia, hydrogen sulfide, carbon dioxide and possibly also hydrogen cyanide and organic ingredients. These wastewater must therefore be treated before being reused or before being discharged into natural waters. On the other hand, it is interested in recovering the materials ammonia and hydrogen sulfide from these effluents in order to use them again as raw materials elsewhere. Known methods for treating such wastewater include the separation of the ammonia and the acid gases hydrogen sulfide, carbon dioxide and optionally hydrocyanic acid by distillation. Basis of these procedures is the combination of the deacidification, thus a selective thermal, sour gas separation, with the thermal Ammoniaabtrieb.

Since the deacidification is not completely feasible, but always a more or less large proportion of the acid gas remains in the water, the subsequent ammonia output does not immediately lead to pure ammonia. Pure ammonia is obtained only after washing the still acid-containing ammonia vapor, in which the remaining sour gases are washed out. Such a method is known from DD-PS 227948. For washing the ammonia steam here fresh water is used. The resulting ammonia-sour gas solution is subsequently treated at temperatures below 60 ° C with inert gas, wherein predominantly the ammonia is expelled. The remaining acid-rich solution is returned to the deacidification, while the ammonia is washed out by means of fresh water from the inert gas-ammonia mixture. The fresh water used in the washing of ammonia or in the ammonia absorption increases the cost of the process, because it creates additional ammonia water, which in turn must be thermally treated.

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Object of the invention

The aim of the invention is to recover pure ammonia and the acid gases from these constituents containing water with little energy expenditure.

Explanation of the essence of the invention

The invention has for its object to provide a method for the thermal recovery of pure ammonia on the one hand and acid gases on the other hand from these components and organic contaminants containing wastewater, which is designed such that a supply of pure water (fresh water) for the separation of the inert gas-ammonia Mixture and for ammonia wash is not required.

The object is achieved according to the invention in that the ammonia water to be treated or a part thereof after distillative deacidification is passed in countercurrent to the inert gas / ammonia mixture, the ammonia being absorbed from this gas mixture. Subsequently, the ammonia water to be treated, which has taken up the additional ammonia, is fed to the thermal ammonia stripping.

In a further development of the method, after the distillative deacidification in addition to the part of the ammonia water to be treated, which is conducted in countercurrent to the inert gas-ammonia mixture, another part of the ammonia water to be treated is used to wash the ammonia released in the thermal ammonia stripping and then, after a Most of the ammonia was expelled, recycled to distillate deacidification. It has been found that for the removal of the ammonia from the inert gas-ammonia mixture and for washing the ammonia after its thermal output instead of fresh water, the use of the deacidified ammonia water to be treated, ie the starting product after its deacidification, is sufficient, although this water is still ammonia and hydrogen sulfide contains.

An expedient embodiment of the method provides that the ammonia water to be treated is cooled after the distillative deacidification to temperatures below 40 ⁰ C and then used for washing the inert gas-ammonia mixture and for washing the liberated in thermal ammonia drive ammonia. For cooling the ammonia water to be treated, use is made of the still enriched ammonia water present after the countercurrent flow to the inert gas / ammonia mixture, which is heated and subsequently supplied to the thermal ammonia stripping. In addition, it is expedient to use the ammonia water to be treated after the distillative deacidification or after the above-described cooling as a heating medium in the endothermic desorption of ammonia, wherein it is cooled simultaneously in the desired manner.

The invention has the advantage that the external reference of pure water (fresh water) for washing the inert gas and the ammonia vapor is not necessary. As a result, the higher cost, both in terms of equipment and energy is avoided, which arises when using fresh water by increasing the throughput of the thermal ammonia output. In the choice of the amount of wash water in the Inertgaswäsche is within certain limits no limitation by energetic aspects, so that a complex cooling can be omitted in this laundry.

embodiment

The invention will be explained in more detail below with reference to three exemplary embodiments. In the accompanying drawing, a scheme of a method for ammonia recovery is shown, wherein the letters include the composition of the respective streams and the numbers the reference numerals for the most important apparatus and pipelines.

Essollen ammonia-containing wastewater are worked up, which in addition to the ammonia also hydrogen sulfide and / or carbon dioxide and are contaminated with organic components. The proportions of the organic components are low; they were therefore not taken into account when stating the composition of the material streams. Such sewage traps in the coal and oil refining on.

The letters in the examples and in the drawing mean:

A - ammonia water to be treated (feed water)

B - sour gases hydrogen sulphide and / or carbon dioxide (final product)

C - deacidified ammonia water

D - the first part of the deacidified ammonia water

E - first cooled ammonia water stream

F - inert gas-ammonia mixture

G - enriched ammonia water

H - the second part of the deacidified ammonia water

J - purified water (final product)

K - uncondensed steam

L - second cooled ammonia water stream

M - washing solution

N - sour gas solution

O - ammonia vapor

P - pure ammonia (end product)

Through the sewer line 1, the reprocessed ammonia water A enters the processing plant. Part of this ammonia water is at the top of the deacidification 2, which operates at atmospheric pressure, abandoned. The other part of the ammonia water is heated in the first heat exchanger 3 by hot purified waste water from the Ammoniakabtriebskolonne 4 and also fed into the deacidification column 2. By heating in the circulating evaporator belonging to the deacidification column 2, almost all of the acid gases B (hydrogen sulphide and / or carbon dioxide) contained in the ammonia water A to be treated are expelled in this column.

The deacidified ammonia water C exits at the bottom of this column. A first part D of the deacidified ammonia water is cooled in the recuperator 5 from about 96 ⁰ C to about 70 ° C, then in the second heat exchanger 6 to about 50 ° C and in the first cooler 7 to 30 ⁰ C. This cooled stream of ammonia water is divided again, wherein the first cooled stream of ammonia water E is passed into the inert gas washing column 8 and is conducted there in countercurrent to an acidic inert gas-ammonia mixture F. In this countercurrent treatment, the ammonia water dissolves the ammonia and the hydrogen sulfide or carbon dioxide from this gas mixture. The enriched ammonia water G, which has been heated to about 52 ° C in this process, is further heated in the recuperator 5 to 80 ° C and passed through the first ammonia water line 9 in the Ammoniakabtriebskolonne 4.

The second part H of the deacidified ammonia water leaving the bottom of the dewatering column 2 is also passed through the second ammonia water line 10 into the ammonia stripping column 4, but at a point below the mouth of the first ammonia water line 9.

In the ammonia stripping column 4, the thermal ammonia stripping is carried out at atmospheric pressure. At the bottom of the column, this purified water leaves J containing about 50 ppm of ammonia, which is cooled in the first heat exchanger 3 and then leaves the plant.

The vapors emerging at the top of the ammonia stripping column 4 are condensed in the dephlegmator 11 to a large extent. The condensate flows into the oil separator 12, in which a part of the organic components is separated, and then back into the top of the column. The steam K which is not condensed in the dephlegmator 11 is washed in the scrubbing column 13 with the second cooled stream of ammonia water L, which is formed when the ammonia water stream leaving the first cooler 7 divides. This second cooled stream of ammonia water is fed via the third ammonia water line 14 at the top of the wash column 13. In the cooling circuit via the second cooler 15 and a column at the top of this column, the heat of absorption is removed, which is formed in the upper column piece by the Ammoniaaufsättigung.

In the middle part of the scrubbing column 13, the countercurrent scrubbing takes place, whereas in the sump part the scrubbing solution is circulated via the third cooler 16 in order to dissipate the heat which results from partial condensation and cooling of the introduced steam. The leaving at the bottom wash solution M is charged at the top of the packed column 17 and passed in this column in countercurrent to the coming of the gas line 18 from the Inertgaswaschkolonne 8 inert gas, wherein a large part of the ammonia is expelled from the wash solution. With the help of the blower 19 while the promotion of the inert gas takes place. In a heating circuit through the second heat exchanger 6 and a column item in the lower part of the packed column 17 the washing solution when heat is applied, so that the bottom temperature is maintained at about 4O ⁰ C. The thus treated acid gas solution N passes through the return line 20 for Sääuerungskolonne 2. The resulting in the packed column 17 inert gas-ammonia mixture F is fed into the inert gas washing column 8 and there largely separated with the aid of the first cooled ammonia water stream E. The withdrawn from the scrubbing column 13 through the first ammonia line 21 ammonia vapor 0 contains only barely measurable traces of hydrogen sulfide or carbon dioxide, but it still contains certain amounts of organic impurities, which are mainly water-soluble and low-boiling and not separated in the oil separator 12 can. They would not be noticeably eliminated in the wash column 13 even if, instead of the inventive treatment of the ammonia vapor with deacidified ammonia water (feedstock), which inevitably still contains organic impurities, pure fresh water would be used, since the complete elimination of the releasable organics for the entire process would have to be used disadvantageously impacting very large amount.

To produce ammonia of the highest purity, which is comparable to that of synthetically produced ammonia, the ammonia vapor 0 coming from the scrubbing column 13 via the first ammonia line 21 in the plate column 22 is subjected to a scrubbing with simultaneous deep cooling with liquid ammonia. The compressor 23 compresses a part of the ammonia purified and dried as a result of the washing in the tray column 22, which is then liquefied in the condenser 24 by means of cooling by cooling water and then discharged to the collector 25. From this collector 25, the liquid ammonia or a part thereof passes through an expansion valve in the tray column 22. In the third heat exchanger 26, the cold of the purified ammonia is used for precooling of the ammonia vapor 0. Finally, the pure gaseous ammonia P leaves the plant through the second ammonia line 27.

If it is desired to remove the pure ammonia of the plant in liquid form, it is removed via the third ammonia line 28.

At the bottom of the tray column 22 exits an aqueous and enriched in organic impurities ammonia solution, which leaves the plant or is fed into the Ammoniakabtriebskolonne 4. In the latter case, after reaching a certain concentration level, the organic impurities leave the plant with the treated wastewater.

NH ₃ CO ₂ example 80,000 1 inert 84206 700 15058 NH ₃ H ₂ S Example 2 80000 82,400 Inert NH ₃ 1600 H ₂ S -4 H ₂ O 1 80,000 - 255/20 83400 H ₂ O n.d. m ³ / h 2120 69301 H ₂ O n.d. 1200 m ³ / h n.d. Example 3 n.d. 1800 kg / h 82 257 in. 85506 80 004 kg / h 86780 90392 in. 2 904 CO ₂ 86836 inert 90765 material 2086 15589 16 205 4355 1200 35809 37,299 1552 1200 kg / r 46426 m ³ / h 48526 electricity 2120 13862 14410 1795 1200 29 632 30865 1347 1200 40270 in. 42 092 A 2 565 2120 n.d. 4 068 2 595 1200 n.d. 2100 1452 716 600 n.d. 1860 2150 B 486 684 13862 3 420 1071 1017 29632 32180 2799 383 600 40 270 43 952 C 432 130 / 66668 2 082 886 419 50971 53093 1352 332 309 40410 42 239 D 641 116 ^! 80,000 2 082 1185 347 80,000 80004 4 403 165 80000 80004 e 1073 7 530 2 071 130 603 5269 4147 735 143 680 6187 F 2 079 123 1727 1524 477 6177 6434 205 333 5 6156 6434 G ^- 4 554 2 257 4 598 6780 10 507 2 756 n.d. 148 6836 11025 H 3148 n.d. 2 257 3 591 n.d. 6780 9192 1304 1068 144 6836 9165 I 54 677 n.d. 185 1075 n.d. 1196 1596 51 n.d. n.d. 1596 K 1 120 14 n.d. 2 580 72 n.d. 1196 1596 1 119 292 n.d. 1596 L 479 691 1395 1147 716 22 M 2 082 684 1 196 1017 n.d. 314 N 2 082 n.d. 1 196 n.d. n. n. 309 O η. η. N. N. n.d. P n. n.

n. b. = not considered

n. n. = undetectable

Claims (5)

claims: 1. A process for the recovery of pure ammonia from hydrogen sulfide and / or , kohlendioxidhaltigem ammonia wastewater, in which the reprocessed ammonia water is deacidified by distillation and the ammonia is driven off, the aborted ammonia is removed by washing still remaining acid gases, these acid gases and a part of the ammonia are dissolved in water, the dissolved ammonia with the aid of inert gas the resulting solution is largely blown out and the remaining solution is returned to the distillative deacidification, the inert gas withdrawn together with the blown ammonia, freed by washing ammonia, fed the resulting solution in this wash the thermal ammonia and the released during thermal stripping ammonia after the Removal of the acid gases optionally subjected to a wash with liquid ammonia, characterized in that the reprocessed ammonia water or a part thereof after the distillative deacidification in countercurrent to the inert gas Ammo nia mixture is performed while taking the ammonia and then fed to the thermal ammonia output. 2. The method according to claim 1, characterized in that after the distillative deacidification, part of the ammonia water to be treated is passed in countercurrent to the inert gas-ammonia mixture and another part of the ammonia water to be treated is used to wash the ammonia removed in the thermal ammonia stripping ammonia. 3. The method according to claim 1 or 2, characterized in that the reprocessed ammonia water after the deacidification by distillation to temperatures below 4O ⁰ C cooled and then used for washing the inert gas-ammonia mixture and for washing the removed in the thermal ammonia stripping ammonia. 4. The method according to claim 3, characterized in that the reprocessed ammonia water after the distillative deacidification is cooled by the present after the countercurrent flow to the ammonia-inert gas mixture to be treated ammonia water. 5. The method according to claim 3, characterized in that the reprocessed ammonia water is used after the distillative deacidification and optionally after cooling as a heating medium in the blowing of the ammonia with the aid of the inert gas.