Optimum method for co-producing melamine and urea

A technology of melamine and urea, applied in chemical instruments and methods, preparation of organic compounds, chemical industry, etc., can solve problems such as unfavorable long-distance transportation, easy bonding, small volume flow, etc., and achieve the effect of ensuring long-term stable operation

Active Publication Date: 2012-11-28
丁泽华 +1
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Problems solved by technology

Improved gas phase quenching process Although the exhaust gas pressure is increased to above 0.3MPa (A), if it is discharged from the outlet branch of the carrier gas compressor, it can reach above 0.6MPa (A), but to merge the exhaust gas of the large-scale melamine plant into the urea plant, either The tail gas is compressed to above 1.8MPa for medium-pressure absorption, or the tail gas is absorbed at low pressure and then subjected to medium-pressure desorption and concentration above 1.8MPa, or ammonia-carbon separation; desorption concentration and ammonia-carbon separation require more than 4 tons of melamine tail gas 2.0MPa steam, such a high steam consumption seriously restricts the development of this process route. Although the energy consumption of the direct compression of tail gas is much lower than that of the low-pressure absorption and medium-pressure analysis process, due to the smal

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  • Optimum method for co-producing melamine and urea
  • Optimum method for co-producing melamine and urea

Examples

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Example Embodiment

[0017] Example 1: An optimized method for co-production of melamine and urea. The melamine production process refers to a gas phase quenching low-pressure circulation process using urea as a raw material, and the urea plant refers to CO 2 Air stripping urea plant.

[0018] The present invention CO 2 Gas stripping urea plant and conventional CO 2 Compared with the steam stripping urea unit: a. Increase the medium-pressure flash evaporation heating and decomposition operation unit, and the pressure is preferably 1.8-2.2 MPa (A).

[0019] b. Add a urine pre-concentrator to recover the condensation heat of the medium-pressure decomposition gas.

[0020] c. Increase the operation unit of the excess ammonia separation and rectification tower to separate excess ammonia in the low-pressure decomposition gas to control the pressure of the urea low-pressure decomposition system. The excess ammonia is separated and discharged from the top of the tower, and the excess ammonia is separated and dis...

Example Embodiment

[0023] Example 2: Such as figure 1 As shown, an optimized method for co-production of melamine and urea. The melamine production process adopts low-pressure gas or solid phase quenching melamine tail gas with a pressure above 0.4 MPa, which is discharged from the front of the carrier gas cycle compressor and directly sent to the urea plant. Co-production method of low-pressure condensation absorption section.

[0024] CO 2 In the gas stripping urea plant, a medium-pressure flash evaporation heating decomposition section with a pressure of 1.8-2.2 MPa (A) is added between the high-pressure section and the low-pressure section. The gas or solid phase quenching melamine tail gas condensation and absorption operation unit is added. The low-pressure decomposition gas is mixed and condensed into the low-pressure methylamine liquid I from the desorption tower of the urea unit. The melamine tail gas and the low-pressure methylamine liquid I are mixed into the melamine tail gas for condens...

Example Embodiment

[0026] Example 3: Such as figure 2 As shown, an optimized method for the co-production of melamine and urea. The melamine production process adopts Eurotech high-pressure method or DSM low-pressure method. . The absorption liquid is methylammonium liquid.

[0027] CO 2 In the gas stripping urea plant, a urine preconcentrator is added after the low pressure decomposition section to recover the condensation heat of the medium pressure decomposition gas. The methylamine liquid from the tail gas of the melamine production process is directly mixed with a part of the medium-pressure methylamine pump and the medium-pressure decomposition gas of the urea device to be sent to the shell side of an evaporator. The condensation temperature of the shell side is 135℃, and the product is discharged from the shell side of the evaporator. Carbamate and uncondensed NH 3 , CO 2 And water vapor, the remaining triamine tail gas methylammonium liquid and the low-pressure methylamine liquid of the ...

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Abstract

The invention relates to an optimum method for co-producing melamine and urea, the melamine production technology is characterized by comprising a gas phase quenching or solid phase quenching low pressure circulation method which takes urea as a raw material, an European science and technology high pressure method or a DSM low pressure method, and an urea device is a CO2 air stripping urea device. The optimum method has the following technical effects that the urea device enables matched reformation according to maximal coproduction melamine capability, and the productivity is increased by near 25% after merging with melamine tail gas, the capacity expansion reformation on synthesis ammonia is not required, because that a medium pressure decomposition system and an urea pre-concentration device are added, the vapor of urea per ton and unit consumption of electricity are not increased.

Description

technical field [0001] The invention is suitable for the improvement of production and energy saving of the carbon dioxide gas stripping urine device and the recycling of ammonia and carbon dioxide tail gas discharged from the melamine production process or methylamine liquid co-production of urea. technical background [0002] The melamine reaction process with urea as raw material produces a large amount of ammonia and carbon dioxide by-products, and at the same time, due to the need to supplement part of the ammonia gas during the process operation, it is necessary to discharge 1.05 tons of ammonia and 1.15 tons of carbon dioxide mixed gas for the production of 1 ton of melamine, commonly known as tail gas; Ammonia and carbon dioxide gas are the raw materials for urea production, so the co-production of melamine and urea is the most suitable in terms of resource allocation. However, due to the different production processes of melamine, the co-production of urea from melam...

Claims

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Application Information

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IPC IPC(8): C07D251/60C07C275/00C07C273/10
CPCY02P20/10Y02P20/50
Inventor 丁泽华
Owner 丁泽华
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