Method for synthetically reutilizing ammonia and hydrogen in tail gas discharged from indigo production

A technology of tail gas and indigo, applied in separation methods, chemical instruments and methods, vapor condensation, etc., can solve problems such as air or water pollution, environmental pollution, resource waste, etc., to reduce pollution, achieve obvious economic benefits, and reduce waste liquids. The effect of emissions

Inactive Publication Date: 2008-10-01
NANJING UNIV OF TECH +1
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  • Abstract
  • Description
  • Claims
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Problems solved by technology

At present, the above-mentioned tail gas is basically simply burned and discharged, resulting in serious pollution to the atmosphere or water sources, and at the same time causing serious w

Method used

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  • Method for synthetically reutilizing ammonia and hydrogen in tail gas discharged from indigo production
  • Method for synthetically reutilizing ammonia and hydrogen in tail gas discharged from indigo production

Examples

Experimental program
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Embodiment 1

[0023] The process of recovering indigo production tail gas is as follows: figure 1 shown, including the following steps:

[0024] 1) The relatively stable composition and flow rate of the ammonia-containing tail gas discharged from the alkali melting section is recovered by ammonia compression method, that is, after the tail gas is buffered and bagged for dust removal, it is cooled and enters the compressor Y1, and then condensed to form liquid ammonia and stored in the storage tank C1;

[0025] 2) The tail gas G1 containing ammonia, air and water vapor discharged from the potassium and sodium salt synthesis section is sent to the absorption tower (T1) through the fan. The tail gas G1 is mainly composed of ammonia and mixed with air (air ≤ 30%)) and saturated water vapor, the operating pressure is normal pressure, through the two-stage absorption of normal temperature process water and low temperature process water in the absorption tower, dilute ammonia water and exhaust ga...

Embodiment 2

[0035] The process flow is the same as in Example 1, and the parameters are the same, except that the low-temperature process water in the absorption tower 2 is changed to normal temperature process water (30° C.). The result shows: the ammonia content becomes 0.008 (8 times than the concentration of discharge in embodiment one) in the absorption tower 2 discharge gas, contains ammonia 560ppm. recovery rate reduces in the gained hydrogen.

[0036] From the above results, it can be seen that the cooling capacity of ammonia evaporation is cleverly used in the process, which reduces the ammonia content in the purified tail gas and improves the recovery rate of ammonia. At the same time, the reboiler set in the process also has the function of adjusting the amount of ammonia gas. When the production of the workshop fluctuates to a certain extent, the amount of ammonia gas used can be adjusted to meet the production needs and solve the problem of continuous ammonia gas consumption. ...

Embodiment 3

[0038] Process flow is as embodiment 1, and main process parameter is also identical. In this embodiment, liquid ammonia is directly used as reflux without using a rectifying column, and an ammonia compressor is installed at the top of the column and a condenser is installed.

[0039] Comparing the operating results of Examples 1 and 3, both processes can reach the quality index of ammonia recovery, meeting the needs of indigo production. But embodiment three increases investment (a compressor and a condenser) and energy consumption (increase 19kw) than embodiment one

[0040] It can be seen from the above results that direct reflux of liquid ammonia is cleverly used in the process flow of the present invention, which meets the operation needs of the rectification tower, and achieves the purpose of saving investment and reducing consumption. Moreover, the reflux of liquid ammonia directly does not need to wait for the hysteresis of heat transfer and mass transfer, the adjustm...

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Abstract

The invention discloses a method for comprehensively recovering and using ammonia and hydrogen gases in tail gases exhausted in indigo production. The final purity of ammonia generated by the recovery with the method is more than 99.9 percent and the ammonia can be directly applied to the production of sodium amide, with simple and convenient operation and large operation elasticity. Furthermore, the purity of the hydrogen recovered by the flow at the same time is more than 99.9 percent and the hydrogen can be directly applied to hydrogenation as a gas source. The technical proposal of the method mainly comprises the steps as follows: 1) liquid ammonia is formed by compressing and cooling the ammonia released from alkali melting positions; 2) purified and exhausted from tail gases, gases at potassium and sodium salt synthesis positions and sodium amine positions are respectively adsorbed; dilute ammonia solution is collected so as to gain high-consistency hydrogen; 3) a combined rectification operation is used for preparing pure ammonia from the dilute ammonia solution. Effects of exhaust reduction, energy saving and efficiency increment can be achieved by the process, and the method of the invention is a novel green processing routine of indigo production.

Description

technical field [0001] The invention relates to a method for recycling waste gas, and more specifically relates to a method for comprehensively recycling ammonia-hydrogen gas from indigo production exhaust tail gas. Background technique [0002] Ammonia gas is mainly used as an intermediate raw material in indigo production, and ammonia gas is also discharged in different sections as waste gas and tail gas. Since the indigo production process is mostly batch operation, the concentration, temperature and flow of the emissions from each step vary greatly, and the composition is complex. There are both hydrogen-containing streams and oxygen-containing streams in the exhaust gas, and explosive mixtures are easily formed during recovery. Therefore, it is technically difficult to recover ammonia and hydrogen in the tail gas. Therefore, quite a lot of indigo dyestuff enterprises discharge the above-mentioned tail gas directly or after simple combustion, resulting in serious pollut...

Claims

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Application Information

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IPC IPC(8): B01D5/00B01D53/14B01D3/16
Inventor 梅华张荣生祝宁东张文达吴德生
Owner NANJING UNIV OF TECH
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