DE1118765B - Process for the production of gaseous ammonia from strong ammonia water - Google Patents

Description

When cooling and cleaning coal distillation gases, it is known that water containing ammonia is obtained, which can be processed into so-called strong water, an approximately 20 to 25% ammonia water, by being driven off. In addition to ammonia, this strong water generally contains about 2 to 6% H ₂ S and 8 to 12% CO ₂ in the form of ammonium sulfide or ammonium carbonate. The recovery of pure ammonia in gaseous form from this strong water is possible in an economical way by deacidifying under very high pressures of 40 to 60 atmospheres and then driving off the deacidified water. It is obvious that one does not like to operate columns under such high pressures, especially since considerable operating temperatures of about 200 ° C. have to be used and the aggressiveness of the strong water at such high temperatures requires special precautionary measures. The energy and material costs are therefore in an unfavorable relationship to the desired success.

For the deacidification of less concentrated, i.e. 4 to 8% ammonia water, deacidification columns are sufficient for pressures of up to about 10 atmospheres, which can also be well controlled in terms of material. In such a column, the hydrogen sulfide would be completely removed from about 4 to 8% ammonia water, but not all of the CO ₂ , of which at most about two thirds would escape at the top of the column even with this less concentrated ammonia water.

The invention solves the problem of obtaining pure gaseous ammonia from strong water using columns designed for pressures of up to about 10 atmospheres and utilizing the knowledge that less concentrated ammonia water is at least easier to deacidify at 5 to 10 atmospheres. However, the invention is also completely new ways of solving this problem. It is based above all on the knowledge that the deacidification _{effect with regard to the CO 2} evacuation is only dependent on the ammonia content of the solutions and, above all, independent of their absolute CO ₂ content. This means, for example, that the deacidification of a 10 ° / cigen ammonia water at 10 atm always leads to an ammonia water with about 3% CO ₂ , regardless of how large the original CO ₂ content is. It is also based on the finding that the strong water is able to absorb _{substantial amounts of CO 2 in the course of a wash.}

According to the invention, gaseous ammonia is obtained from strong water from coking plants or a similar joint process for the extraction of gaseous ammonia from strong ammonia water

Applicant:

Mining Association G.m.b.H., Essen, Dortmunder Str. 151

Dr. Georg Huck, Dortmund-Eving, and Dr. Paul Opgenhoff, Essen, have been named as the inventor

Set solution obtained by diluting the strong water and deacidifying under pressures of up to 15 atm, removing practically all of the H _{2 S in addition to some of the CO 2,} removing the partially deacidified ammonia _{water and driving off the NH 3} and CO ₂ -containing fumes is passed into a washer, the vapors are washed here with the strong water intended for deacidification or a part of it, taking up the CO ₂ still contained in the abortion swath, and processed for ammonia, while the steam flowing off from the steam washer and, if necessary, the remaining strong water, preferably with the hot Abortion drain water is diluted.

The deacidification and subsequent removal of ammonia water has long been known in coking technology. In this respect, the new process consists of a combination of process steps that are known per se. In particular, it achieves an excellent effect with regard to the removal of CO ₂ from ammonia water without the use of devices that have not yet been tested. Despite the dilution of the strong water, e.g. B. to twice the volume or more, it works quite economically because, as I said, with a deacidification at 50 atm, particularly high steam costs are to be expected, which are greater than the costs of processing the increased amount of liquid. In contrast, the process according to the invention manages with pressures of 10 to 15 atmospheres. In addition, the total steam requirement can be kept as low as possible by means of heat exchange devices.

In general, excellent results are obtained using strong water with 20 to 25% ammonia

109 748/417

is diluted to an ammonia content of about 7 to 10%. At higher concentrations, e.g. B. an ammonia content of 12 to 15%, the absorption of the CO ₂ in the washing of the abortion swaths can be inadequate. The steam consumption during deacidification and stripping also rises sharply with the increasing concentration of the ammonia water, since higher decomposition and evaporation energies then have to be applied. On the other hand, too much dilution of the strong water would also undesirably increase the amount of steam required for deacidification and the subsequent abortion process, since larger amounts of liquid would have to be heated. In addition, larger deacidifiers and aborters would also be required. A useful guide for the optimal dilution is the expulsion of the hydrogen sulfide in the deacidification column. It is advisable to dilute the strong water just enough that practically all of the hydrogen sulfide is expelled during the deacidification.

The method according to the invention will be explained in more detail with reference to the drawing.

The pressure deacidifier 1 consists, as usual, of a column with distributor elements in the lower and middle Space and cooling coils in the upper part. Ammonia water is introduced via lines 2 and 3, some fresh water via line 4 to cool the rising vapors and to recirculate Ammonia. Deacid vapor leave the column via line 5 or valve 6. The column can indirect, e.g. B. via the snakes 7, or be heated directly.

The partially deacidified water is left from the bottom of column 1 via line 8 into the stripper 9 overflow, which is operated directly with steam as usual. The line 10 indicates that the steam from the indirect heating of the deacidifier can be used for the abortionist.

The line 11 serves to discharge the practically NH ₃ - and CO ₂ -free wastewater. The expeller fumes leave the expeller 9 via line 12, are cooled to 50 to 70 ° C. and flow through the washer 13, which is expediently indirectly cooled in the upper part, which is illustrated by the cooling coil 14. The vapors, which now consist exclusively of ammonia and some water vapor, leave the washer via line 15. Traces of H ₂ S can be removed from the ammonia in a second wash with ammonia water or alkali lye.

The heavy water is wholly or partially via the line 16 after a detour via the washer 13 led to deacidifier 1. The supply to the washer 13 takes place via line 17, the discharge from Washer via line 18, which opens into line 16 again. For diluting strong water A line 19 branches off from the sewage line 11 and also opens into the pipeline 16. Mixing containers are expediently placed at the points at which two liquid streams are combined intended. The diluted strong water is finally via a liquid pump 20 in the Deacidifier 1 pumped in.

When deacidifying a coke oven water with 2OVoNH ₃ , 10% CO ₂ and 4% H ₂ S, the following process balance results if 40% of this water is passed through the washer 13 and the strong water is diluted approximately three times with water from the stripper : The water entering the deacidifier contains 8% NH ₃ , 6% CO ₂ and

ίο 1.4% H ₂ S. After deacidification at 8 atm this water contains 7.9% ammonia, 2.5% CO ₂ and 0.08% H ₂ S. It is completely driven off in the column 9, so that the drain from the aborter contains only 0.01% ammonia and neither CO ₂ nor H ₂ S.

From 1 m ^{3 of} processed strong water, a vapor with 227 kg of NH ₃ and 72 kg of CO ₂ is obtained behind the drift. This vapor is washed in the washer 13 with 0.4 m ^{3 of} strong water, thereby separating all of the carbon dioxide from the ammonia. The drain from the scrubber 13 contains 27.5% NH ₃ and 28% CO ₂ . A small part of the ammonia is also washed out by the strong water in the washer 13. After mixing with the raw water, the concentration of the strong water is 23% NH ₃ , 17.5% CO ₂ and 4% H ₂ S.

The above numerical example shows that with the invention a 100% strength water can easily be obtained Ammonia can be obtained. It should be noted, however, and should be understood from the foregoing be clearly recognizable that the process with regard to the concentrations to be set Solutions in the individual sections of the procedure and with regard to the conditions for deacidification, the abortion and the final wash can be varied within certain limits.

Claims (3)

PATENT CLAIMS: 1. Process for the extraction of gaseous ammonia from the strong water of the coking plants and the like., characterized in that the strong water is diluted and deacidified under pressures of up to 15 atmospheres, with practically all of the H _{2 S being removed in addition to part of the CO 2} , the partially deacidified ammonia water being driven off and the NH ₃ - and CO ₂ -containing vapors are passed into a washer, the vapors are washed here with the strong water intended for deacidification or a part of the same, taking up the CO ₂ still contained in the abortion vapors, and processed for ammonia, while the steam flowing off from the vapor washer and, if necessary, the remaining strong water preferably is diluted with the hot drainage water from the abortionist. 2. The method according to claim 1, characterized in that 20 to 25% ammonia water is diluted to about 7 to 12% ammonia water. 3. The method according to claim 1 and 2, characterized in that the deacidification of the diluted Strong water is carried out at pressures of about 8 to 15 atü. For this purpose, 1 sheet of drawings