DE102014115395A1 - Process and plant for the separation of ammonia from a gas mixture - Google Patents

Abstract

A method for separating ammonia from an ammonia-containing gas mixture 1 'by at least partially mixing the gas mixture with an aqueous liquid from which ammonia is introduced, the gas mixture and the aqueous liquid being introduced separately into the inlet hood 15 of a shell-and-tube heat exchanger 16 and into a biphasic gas therein Liquid mixture are mixed, in which case the gas-liquid mixture is passed through the tubes of the tube bundle heat exchanger 16, wherein the gas-liquid mixture is cooled by a shell-side guided cooling medium, then the gas-liquid mixture from the heat exchanger 16 in a separator 18 for separating the gas - And the liquid phase is transferred, wherein an ammonia-depleted gas phase 19 and an ammonia-enriched liquid phase 12 'is obtained and discharged for further use from the separator 18.

Description

Field of the invention

The invention relates to a method and a plant for separating ammonia from an ammonia-containing gas mixture by mixing the gas mixture with an aqueous liquid from which ammonia is at least partially absorbed.

State of the art

Such methods and devices are known per se. An important application for this is in the context of the workup of gas condensate produced in the fixed bed coal gasification by the Sasol-Lurgi process. In this workup successively tar, oil, phenols and then sequentially sour gas and ammonia are separated from the gas condensate. These processes are described in GASIFICATION, 2nd Ed., Christopher Higman / Maarten van der Burgt, Gulf Professional Publishing, Chapter 5.1.1, and Ullmann's Encyclopaedia of Industrial Chemistry, 6th Ed., Vol. 15, Chapter 6, page 430 ff ,

The separation of ammonia is often carried out in practice by absorption of the ammonia in an absorption column. In this case, the ammonia-containing gas mixture flows through the column from bottom to top and is characterized by one or more, e.g. led three packings. In countercurrent to water, as an absorbent, passed from top to bottom through the packs. In the lowermost packing, in which the ammonia-containing gas mixture first comes into contact with the aqueous absorption liquid, the aqueous absorption liquid is in each case via an external heat exchanger, because of the large amount of ammonia absorbed in this contact and the associated large accumulation of heat of absorption Circle led. This measure is often carried out in the second packed pack.

Since the absorption capacity of the aqueous absorption liquid generally decreases with increasing temperature, it is necessary to keep the temperature rise caused by the absorption of the ammonia low by means of a correspondingly large amount of liquid. However, this leads to the fact that the column must be designed in the region of the lowest, with the gas mixture first coming into contact Füllkörperpackung with a very large diameter in order to distribute the large amount of liquid evenly over the Füllkörperpackung. This large volume of liquid to be circulated leads to large apparatus dimensions and corresponding costs, which reduce the economic efficiency of the method.

The object of the present invention is to provide an improved process and a plant operating according to this process, in which the contact between the ammonia-containing gas mixture and the absorption liquid is carried out in a less voluminous, and thus more cost-effective apparatus.

Description of the invention

The object is achieved by the invention according to claim 1 by a method for separating ammonia from an ammonia-containing gas mixture by mixing the gas mixture with an aqueous liquid from which ammonia is at least partially absorbed, wherein the gas mixture and the aqueous liquid separated from each other in the inlet hood a shell-and-tube heat exchanger are introduced therein and mixed into a two-phase gas-liquid mixture, wherein then the gas-liquid mixture is passed through the tubes of the tube bundle heat exchanger, wherein the gas-liquid mixture is cooled by a shell side run cooling medium, then the gas-liquid mixture from the heat exchanger in a separator for separating the gas and the liquid phase is transferred, wherein an ammonia-depleted gas phase and an ammonia-enriched liquid phase obtained and each for further use of the separator 18 be discharged.

According to the invention, the mixing of the ammonia-containing gas mixture coming from the total stripping column with the aqueous liquid, the absorption of the ammonia and the removal of the heat of absorption in a shell-and-tube heat exchanger are carried out. In this case, the gas mixture and the aqueous liquid are introduced separately into the inlet hood of the tube bundle heat exchanger and mixed into a two-phase gas-liquid mixture, wherein the gas-liquid mixture is then passed through the tubes of the tube bundle heat exchanger, wherein the gas-liquid mixture guided by a shell side Cooling medium is cooled. By flowing together the ammonia-containing gas mixture and the absorbing aqueous liquid through the tubes of the heat exchanger, the heat of absorption is partly dissipated as they are formed, lowering the temperature rise of the liquid, thereby increasing the absorbency of the liquid. Subsequently, the gas-liquid mixture is transferred from the heat exchanger in an apparatus for separating the gas and the liquid phase.

Preferred embodiments of the invention

An expedient embodiment of the invention is that the aqueous liquid is introduced into the ammonia-containing gas mixture by means of at least one nozzle in the inlet hood of the shell-and-tube heat exchanger. This is a simple way to evenly distribute a liquid in a gas.

A variant of the invention is to carry out the absorption of the ammonia in a multi-stage process, wherein the first stage according to claim 1 or 2 is carried out and then, in a second stage, the resulting ammonia-depleted gas phase is passed into an absorption column and this flows through from bottom to top, and wherein fresh water is introduced into this column, which flows through the column in countercurrent to the gas phase from top to bottom and wherein the further depleted in ammonia gas is discharged from the column for further use, and wherein the case with ammonia discharged water is discharged as an aqueous liquid from the column and used in the first step by being introduced into the inlet hood of the tube bundle heat exchanger.

By this measure, residual contents of ammonia in a conventional manner, d. H. removed by contact of the gas and the liquid phase in one or more Füllkörperschichten, from the gas phase. In connection with the inventive mixing of the gas phase and the aqueous liquid in the tube bundle heat exchanger so particularly high separation efficiency for ammonia can be achieved with a small overall size of the apparatus used.

A further particular embodiment of the invention is characterized in that the absorption column used in the second stage is equipped with two separate, superimposed mass transfer devices, for example random packings or structured packings, wherein the aqueous phase in a circle over the lower packing and for cooling via an outside the column lying heat exchanger is performed. This embodiment is particularly advantageous if, according to the prior art, in the first step, the absorption is carried out in a packed body.

• (a) einen Rohrbündelwärmetauscher 16 mit Zuleitungen für ein ammoniakhaltiges Gasgemisch 1‘ und eine wässrige Flüssigkeit 14 und einer Ableitung für ein zweiphasiges Gas-Flüssiggemisch 17‘, geeignet zur Vermischung des Gasgemischs 1‘ und der wässrigen Flüssigkeit 14 zu dem zweiphasiges Gas-Flüssiggemisch 17‘ und zur Kühlung desselben,
• (b) einen dem Anlagenteil (a) strömungsmäßig nachgeschalteten Abscheider 18 zur Trennung in eine an Ammoniak angereicherte Flüssigphase 12‘ und eine an Ammoniak abgereicherte Gasphase 19,
• (c) einen dem Anlagenteil (b) in Bezug auf die Gasphase strömungsmäßig nachgeschaltete Absorptionskolonne 2‘, enthaltend eine Zuleitung für Frischwasser 6‘, eine Ableitung für mit Ammoniak beladenes Wasser als wässrige Flüssigkeit 14, eine Ableitung für an Ammoniak abgereichertes Gas 13‘ sowie mindestens eine Stoffaustauschvorrichtung 4‘, wobei ein erster Teil der wässrigen Flüssigkeit 14 mittels einer Fördervorrichtung 8‘ über einen Wärmetauscher 10‘ gefördert, dort gekühlt und anschließend der Absorptionskolonne 2‘ oberhalb der Stoffaustauschvorrichtung 4‘ aufgegeben wird und wobei ein zweiter Teil der wässrigen Flüssigkeit 14 zum Anlagenteil (a) zurückgeführt wird.

In a further aspect, the invention also relates to a plant for separating ammonia from an ammonia-containing gas mixture, comprising the following plant parts:

• (a) a shell and tube heat exchanger 16 with supply lines for an ammonia-containing gas mixture 1' and an aqueous liquid 14 and a derivative for a two-phase gas-liquid mixture 17 ' , suitable for mixing the gas mixture 1' and the aqueous liquid 14 to the two-phase gas-liquid mixture 17 ' and to cool it,
• (B) a downstream of the plant part (a) separator 18 for separation into an ammonia-enriched liquid phase 12 ' and an ammonia-depleted gas phase 19 .
• (c) an absorption section downstream of the plant section (b) with respect to the gas phase 2 ' containing a supply line for fresh water 6 ' , a discharge for ammonia-laden water as an aqueous liquid 14 , a discharge for ammonia-depleted gas 13 ' and at least one mass transfer device 4 ' , wherein a first part of the aqueous liquid 14 by means of a conveyor 8th' via a heat exchanger 10 ' promoted, cooled there and then the absorption column 2 ' above the mass transfer device 4 ' is abandoned and wherein a second part of the aqueous liquid 14 to the plant part (a) is returned.

embodiment

Further developments, advantages and applications of the invention will become apparent from the following description of exemplary embodiments and the drawings. All described and / or illustrated features alone or in any combination form the invention, regardless of their combination in the claims or their dependency.

Show it

1 a process for separating ammonia from a gas mixture containing ammonia and inert gases, according to the prior art,

2 an exemplary embodiment of the method according to the invention. First, to hand on 1 The prior art will be explained. The ammonia-containing gas mixture 1 is at the bottom of the absorption column 2 introduced and flows through the mass transfer devices in succession 3 . 4 and 5 , which are designed here as packed packing. In the head of the column 2 becomes demineralized water 6 introduced as an absorbent and flows through in countercurrent to the rising gas mixture in succession, the packed packings. For the lower and middle packing 3 and 4 The water is pumped 7 and 8th circulated. About the heat exchangers 9 and 10 In this case, the heat of absorption of the absorption of ammonia is removed from the water. In this way, a higher uptake of water to ammonia is achieved. At the bottom of the column 2 is over pump 11 Ammonia-enriched aqueous fluid 12 deducted for further use. At the head of the column 2 becomes ammonia-depleted gas 13 , essentially nitrogen-containing inert gas, withdrawn for further use.

Due to the large volume flows of the partially loaded absorbent must in particular the bottom packing packing 3 be made particularly large. Therefore, large sizes for the absorption column result 2 , in particular with regard to the column cross-section. This in turn leads to increased investment costs and limitations with regard to the installation of the absorption column 2 within the plant network. Furthermore, the pump must 7 and the heat exchanger 9 be designed accordingly powerful.

2 shows as an example of an embodiment of the method according to the invention, such as the ammonia-containing gas mixture 1' and a stream 14 aqueous liquid in the entrance hood 15 a shell and tube heat exchanger 16 be initiated. The resulting two-phase gas-liquid mixture, after flowing through the tubes of the heat exchanger, with a large portion of the ammonia from the gas phase being absorbed by the liquid phase and heat of absorption being removed, is taken as a current 17 ' in a separator 18 initiated for the separation of the gas and the liquid phase. This turns the gas phase into electricity 19 in the bottom of the absorption column 2 ' introduced and flows through the packed packing 4 ' and 5 ' to the head of the column 2 ' , At the head of the column 2 ' we demineralized water 6 ' introduced, which absorbs as residual absorbent ammonia levels from the gas phase. The largely freed from ammonia gas phase leaves the column 2 ' on the head as electricity 13 ' for further treatment. About the lower packing 4 ' the water is pumped 8th' circulated, passing over the heat exchanger 10 ' Absorption heat is dissipated. The circulation becomes electricity 14 to the heat exchanger 16 branched off. The generated aqueous ammonia-enriched liquid 12 ' gets out of the separator 18 discharged and by pump 11 ' fed further use.

Industrial Applicability

The invention is a cost effective alternative to a practical method and is therefore industrially applicable.

LIST OF REFERENCE NUMBERS

1, 1 '

Gas mixture, containing ammonia

2, 2 '

absorption column

3

Mass transfer device

4, 4 '

Mass transfer device

5, 5 '

Mass transfer device

6, 6 '

Fresh water or demineralized water

7

pump

8, 8 '

pump

9

heat exchangers

10, 10 '

heat exchangers

11, 11 '

pump

12, 12 '

aqueous liquid, enriched in ammonia

13, 13 '

Inert gas, depleted of ammonia

14

aqueous liquid

15

inlet hood

16

Tube heat exchanger

17 '

Gas-liquid mixture

18

separators

19

gas phase

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• GASIFICATION, 2nd ed., Christopher Higman / Maarten van der Burgt, Gulf Professional Publishing, Chapter 5.1.1 and in Ullmann's Encyclopedia of Industrial Chemistry, 6th Ed., Vol. 15, Chapter 6, page 430 et seq. [0002]

Claims (5)

Process for separating ammonia from an ammonia-containing gas mixture 1' by mixing the gas mixture with an aqueous liquid from which ammonia is at least partially absorbed, characterized in that the gas mixture and the aqueous liquid 14 separated from each other in the entrance hood 15 a shell and tube heat exchanger 16 introduced therein and into a two-phase gas-liquid mixture 17 ' be mixed, and then the gas-liquid mixture through the tubes of the tube bundle heat exchanger 16 is passed, wherein the gas-liquid mixture is cooled by a jacket-side guided cooling medium, then the gas-liquid mixture from the heat exchanger 16 in a separator 18 is transferred to the separation of the gas and the liquid phase, wherein a gas phase depleted of ammonia 19 and an ammonia-enriched liquid phase 12 ' received and each for further use from the separator 18 be discharged. A method according to claim 1, characterized in that the aqueous liquid is introduced by means of at least one nozzle in the inlet hood of the tube bundle heat exchanger in the ammonia-containing gas mixture. A process for separating ammonia from an ammonia-containing gas mixture by mixing the gas mixture with aqueous liquid from which the ammonia is at least partially absorbed, characterized in that the process is carried out in two steps, the first step being according to claim 1 or 2, then obtained in the first step, ammonia-depleted gas phase 19 in an absorption column 2 ' is passed and flows through them from bottom to top, in the column fresh water 6 ' is introduced, which is the absorption column 2 ' flows through in countercurrent to the gas phase from top to bottom and the case while the further depleted of ammonia gas 13 ' for further use from the column 2 ' is discharged and wherein the case with ammonia-laden water as an aqueous liquid 14 from the column 2 ' discharged and used in the first step, placing it in the entrance hood 15 of the tube bundle heat exchanger 16 is initiated. A method according to claim 3, characterized in that the absorption column 2 ' with two separate, overlying mass transfer devices 4 ' . 5 ' or structured packing, wherein the aqueous phase is above the lower packing 4 ' in a circle and for cooling via a heat exchanger located outside the column 10 ' to be led. Plant for separating ammonia from an ammonia-containing gas mixture, comprising the following parts of the installation: (a) a shell-and-tube heat exchanger 16 with supply lines for an ammonia-containing gas mixture 1' and an aqueous liquid 14 and a derivative for a two-phase gas-liquid mixture 17 ' , suitable for mixing the gas mixture 1' and the aqueous liquid 14 to the two-phase gas-liquid mixture 17 ' and for cooling the same, (b) a downstream of the plant part (a) separator 18 for separation into an ammonia-enriched liquid phase 12 ' and an ammonia-depleted gas phase 19 (c) an absorption column downstream of the plant section (b) with respect to the gas phase 2 ' containing a supply line for fresh water 6 ' , a discharge for ammonia-laden water as an aqueous liquid 14 , a discharge for ammonia-depleted gas 13 ' and at least one mass transfer device 4 ' , wherein a first part of the aqueous liquid 14 by means of a conveyor 8th' via a heat exchanger 10 ' promoted, cooled there and then the absorption column 2 ' above the mass transfer device 4 ' is again abandoned and wherein a second part of the aqueous liquid 14 to the plant part (a) is returned.

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