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Device and technique for recovering melamine exhaust by using urea unit

A melamine and urea plant technology, applied in the preparation of organic compounds, urea derivatives, organic chemistry, etc., can solve the problems of insufficient heat utilization rate of melamine tail gas, inconvenient urea production control process, unstable urea production process, etc. , to achieve the effect of stable urea production control process, convenient urea production process, and reducing the number of times of flow into different equipment

Active Publication Date: 2015-02-25
HUAQIANG CHEM GRP
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  • Claims
  • Application Information

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Problems solved by technology

[0011] The present invention proposes a device and process for recovering melamine tail gas using a urea plant, which solves the shortcomings of the prior art that the heat utilization rate of melamine tail gas is not high enough, the control process of urea production is inconvenient, and the urea production process is unstable. It can better utilize the heat of melamine tail gas, and the urea production control process is stable, which is convenient to control the urea production process and does not increase the energy consumption of the urea plant

Method used

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  • Device and technique for recovering melamine exhaust by using urea unit

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Embodiment 1

[0054] This embodiment provides a process for recovering melamine tail gas using a urea plant. The urea plant used in this embodiment is a dual-load urea plant that can run two carbon dioxide compressors at the same time. The theoretical output is 36 tons / hour. The load of melamine tail gas is 120 tons / day, and the present embodiment comprises the steps:

[0055] Step 1. Pressurize the melamine tail gas to 1.91MPa through the tail gas compressor 5.

[0056]Step 2, the melamine tail gas after the pressurization is transported in one section of decomposition tower 6 through tail gas compressor 5, simultaneously the urea solution after being heated by steam in a sub-heater 8 is introduced into the lower separation section of one section of decomposition tower 6, and then The urea solution in the pre-separator 1 is injected into the pre-rectification section of a decomposition tower 6; the urea solution in the 8 tubes of a sub-heater is heated to 157°C, and the urea solution in th...

Embodiment 2

[0062] This embodiment provides a process for recovering melamine tail gas using a urea plant. The urea plant used in this embodiment is a dual-load urea plant that can run two carbon dioxide compressors at the same time. The theoretical output is 36 tons / hour. The load of melamine tail gas is 135 tons / day, and the present embodiment comprises the steps:

[0063] Step 1. Pressurize the tail gas of melamine to 1.8MPa through the tail gas compressor 5.

[0064] Step 2, the difference between this step and Step 2 in Implementation 1 is: "Heat the urea solution in the 8 tubes of a sub-heater to 155°C, and the urea solution in the 8 tubes of a sub-heater enters a section of decomposition tower 6 The lower part of the separation section", "the temperature of the urea solution at the outlet of a sub-heater 8 is controlled at 155 ° C, and the urea solution at 155 ° C flows into one section of decomposition tower, and after flowing out from the bottom outlet of one section of decomposi...

Embodiment 3

[0069] This embodiment provides a process for recovering melamine tail gas using a urea plant. The urea plant used in this embodiment is a dual-load urea plant that can run two carbon dioxide compressors at the same time. The theoretical output is 37 tons / hour. The load of melamine tail gas is 150 tons / day, and the present embodiment comprises the steps:

[0070] Step 1. Pressurize the tail gas of melamine to 2.0MPa through the tail gas compressor 5.

[0071] Step 2, the difference between this step and Step 2 in Implementation 1 is: "heat the urea solution in the 8 tubes of a sub-heater to 160°C, and the urea solution in the 8 tubes of a sub-heater enters a section of decomposition tower 6 The lower part of the separation section", "the temperature of the urea solution at the outlet of a sub-heater 8 is controlled at 160 ° C, and the urea solution of 160 ° C flows into one section of decomposition tower, and after flowing out from the bottom outlet of one section of decomposi...

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Abstract

The invention provides a device and technique for recovering melamine exhaust by using a urea unit, relating to the technical field of melamine exhaust recovery treatment. The device comprises an exhaust compressor and a urea unit with a primary decomposing tower, wherein the side wall of the primary decomposing tower corresponding to the bottom of the lower separating section is provided with an exhaust inlet; and the exhaust compressor is communicated with the primary decomposing tower through the exhaust inlet. The technique comprises the following steps: sending pressurized melamine exhaust to the primary decomposing tower, introducing a urea solution heated by a primary heater into the primary decomposing tower, injecting a urea solution in a preseparator into a pre-rectifying section, controlling the urea solution at the outlet of the primary heater at 155-160 DEG C, and cooling the gas-liquid mixture in a methylamine condenser to 90-100 DEG C. The device and technique can well utilize the heat of the melamine exhaust, are stable in the production process and convenient to control, and do not increase energy consumption generated by the urea unit.

Description

technical field [0001] The invention relates to the technical field of recovery and treatment of melamine tail gas, in particular to a device and process for recovering melamine tail gas using a urea plant. Background technique [0002] Usually, melamine tail gas contains 68% to 72% ammonia and 28 to 32% carbon dioxide, which can be used to co-produce soda ash, urea and ammonium bicarbonate. In addition, the temperature of melamine tail gas is generally 165°C to 175°C, making melamine Exhaust gas has extremely high heat utilization value. Therefore, the recovery and utilization of melamine tail gas is of great significance to waste reuse and energy saving and emission reduction. [0003] At present, due to the obvious excess production capacity of soda ash and ammonium bicarbonate in China, the co-production of urea with melamine tail gas has become the main method of recycling melamine tail gas. The traditional method of using melamine tail gas to co-produce urea mainly i...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C273/12C07C273/04B01D53/76
CPCY02P20/141
Inventor 杨世立刘华郭卫红
Owner HUAQIANG CHEM GRP
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