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Tail gas recycling process and system for melamine production device

A production device and technology for melamine, applied in the field of tail gas recovery process and system, can solve the problems of lower urea synthesis conversion rate, disordered water balance of urea system, and high pressure of synthesis system, and achieve the effects of low production cost, easy operation and short process flow

Active Publication Date: 2014-12-03
WUHUAN ENG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] Due to the low pressure of the tail gas, no matter what method is used to send it to the urea plant for recovery, the amount of water brought into the system will be very high, which will lead to a decrease in the conversion rate of urea synthesis, a decrease in production capacity, and an increase in consumption, and even cause the water balance of the urea system to be disordered and unable to normal operation
[0007] On the other hand, whether the urea plant used to produce urea uses CO 2 For various urea production processes such as steam stripping process, ammonia stripping process, ACES process, aqueous solution full circulation method or thermal circulation method, the pressure of the synthesis system is usually high, such as the content of the stripper outlet in the ammonia stripping process The urea solution of methylammonium has a pressure of about 14.6MPa(G). When it enters the subsequent medium-pressure recovery system, it needs to be depressurized (usually by using a regulating valve) to meet the pressure requirements of the medium-pressure recovery system. However, this The step-down process is actually a loss of system energy, which is not conducive to energy saving and consumption reduction

Method used

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  • Tail gas recycling process and system for melamine production device
  • Tail gas recycling process and system for melamine production device

Examples

Experimental program
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Effect test

Embodiment 1

[0028] Taking the production of urea by ammonia stripping process as an example, under normal working conditions, the pressure from the stripper 1 is about 14.6MPa(G), and the urea solution (or process gas) at a temperature of 204°C enters as the driving medium. The driving medium inlet 2.2 of the ejector 2, and the NH-containing 3 and CO 2 The low-pressure exhaust gas enters the exhaust gas inlet 2.2 of injector 2, and the urea solution decompressed to 1.8MPa (G) by injector 2 and the low-pressure exhaust gas decompressed to 1.8MPa (G) by injector 2 are mixed by injection port 2.3 at the same time It is sprayed out and enters the medium-pressure decomposition tower 3 for medium-pressure decomposition. The medium-pressure decomposition gas obtained from the top of the medium-pressure decomposition tower 3 enters other processes of the medium-pressure recovery system, and finally returns to the urea synthesis system to co-produce urea; the bottom of the tower flows out The ure...

Embodiment 2

[0032] The difference from Example 1 is that in the aqueous solution full circulation urea production process, the stripper 1 is replaced by the urea synthesis tower 5 in the high-pressure synthesis system.

[0033] The method of the present invention is applicable to various urea production processes, the pressure of the driving medium of the injector 2 is 13MPa(A)~25MPa(A), and the pressure of the driving medium must be higher than that of the NH-containing urea from the melamine production device 6. 3 and CO 2 The pressure of the low-pressure exhaust gas, the output pressure of the injector 2 can be reasonably adjusted according to the operating pressure of the medium-pressure recovery system of the specific urea plant, preferably pressurized to 1.7MPa(A)-2.0MPa(A) through the injector. For other process conditions, refer to the specific urea production process.

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Abstract

The invention relates to a tail gas recycling process and a tail gas recycling system for a melamine production device. The problems of the existing tail gas recycling process for the melamine production process that urea synthesis conversion rate is low, the yield is reduced, the consumption is increased, even water balance of a urea system is disordered and the urea system cannot work normally are solved. According to the technical scheme, low-pressure tail gas containing NH3 and CO2 guided out of a tail gas outlet of the melamine production device is fed to an ejector; the low-pressure tail gas is sprayed out and sent into a pressure suction system after being pressurized to 0.3MPa(A)-7MPa(A) by the ejector. The tail gas recycling system for the melamine production device comprises a melamine production system, wherein a tail gas outlet of the melamine production device is connected with a medium-pressure recycling system in a urea device by the ejector. The tail gas recycling process disclosed by the invention is short in flow, low in investment, low in energy consumption and low in cost. The tail gas recycling system disclosed by the invention is simple in structure, easy to operate, energy-saving and consumption-reducing, safe and reliable and environment-friendly.

Description

technical field [0001] The invention relates to a melamine production process and system, in particular to a tail gas recovery process and system of a melamine production device. Background technique [0002] At present, the mainstream melamine production process in the world uses urea (granule or molten urea) as raw material, and its chemical reaction equation is: [0003] 6CO(NH 2 ) 2 =C 3 N 6 h 6 +3CO 2 +6NH 3 [0004] Through the reaction equation, it can be calculated that 6 kmol of urea is consumed for every 1 kmol of melamine produced, and 6 kmol of NH is released at the same time. 3 and 3kmol of CO 2 , so how to effectively recycle the released NH 3 and CO 2 Just become the important way of reducing melamine cost, also be the needs of environmental protection. In the process of producing melamine by urea polymerization, because ammonia and carbon dioxide are just the raw materials for urea synthesis, it is a feasible and economical method to remove part o...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07D251/60C07C273/04
CPCY02P20/141
Inventor 夏炎华孙喜杨志国
Owner WUHUAN ENG