Production equipment, energy-saving production system and production method for melamine

Abstract

The invention discloses a heat-conducting oil hollow blade cooling crystallizer for melamine, an energy-saving production system consisting of the crystallizer and a method for producing the melamine by using the system. The invention is characterized in that: a hot air cooling crystallization system consisting of the heat-conducting oil hollow blade cooling crystallizer, a hot air purification device, a heat-conducting oil steam generator and a cyclone separator is adopted. In the invention, the heat-conducting oil hollow blade cooling crystallizer which is provided with a movable heat exchange surface and has the heat exchange surface with a self-cleaning function is used for crystallizing and recovering the melamine for the first time; heat-conducting oil is adopted as a melamine crystallization cooling medium for the first time; heat is transferred to soft water to produce steam by the heat-conducting oil; the heat-conducting oil is in a closed cycle without heat loss; and thus, high-efficiency recycling of waste heat of cooling crystallization is realized, energy is saved and consumption is reduced.

Description

technical field [0001] The invention relates to the field of chemical industry, in particular to a production system and a production process of melamine. Background technique [0002] At present, the production process of domestic melamine mainly includes the traditional one-step method at normal pressure, one-step method at low pressure and two-step method at normal pressure; there are also very few high-pressure one-step methods. The normal pressure mentioned here refers to the system pressure of 0-0.2MPa, the low pressure refers to the system pressure of 0.2-1MPa, and the high pressure refers to the system pressure greater than 1MPa. Relevant to the present invention are traditional normal pressure one-step method, low pressure one-step method and normal pressure two-step method. (The production process system of the traditional atmospheric pressure one-step method and the low-pressure one-step method are exactly the same, the difference is that the system pressure is d...

AI Technical Summary

Problems solved by technology

[0009] The common disadvantages of the hot gas cooling and crystallization systems of the above-mentioned traditional processes are: the system structure is complex, the waste heat in the cooling and crystallization process is not recycled, and the waste heat is dissipated into the atmosphere, resulting in a great waste of heat and high energy consumption of the system

[0011] 1. The crystallizer, liquid urine circulation pump, liquid urine washing tower, gas-liquid separator, liquid urine cooler and other equipment and pipeline valves are all made of stainless steel, most of which are made of expensive 316L stainless steel, and the equipment is huge and numerous. It is complicated, occupies a large production space, and requires huge investment in equipment and supporting civil engineering;

[0012] 2. The amount of circulating cold air used for crystallization is six to seven times that of the normal reaction cycle process, which requires a high-power air-conditioning fan to circulate the cold air; the liquid-urine circulation is also large, and a high-power liquid-urine circulation pump is also required to complete it. All need to consume a large amount of electricity, and the energy consumption is very high;

[0013] 3. The process equipment of the cooling crystallization system is complex and numerous, the production process is long, the operation is complicated, and the control is difficult;

[0014] 4. In the process of continuous heating and cooling of liquid urine, it will not only cause a large amount of power consumption, but also cause high-temperature urea decomposition and partial biuret phenomenon with process fluctuations, increasing the consumption of urea;

[0015] 5. Liquid urine is easy to crystallize at low temperature, and all equipment and pipelines in contact with liquid urine require steam system heat tracing; in addition, crystallizers also need steam system heat tracing, which greatly increases energy consumption;

[0016] 6. A small amount of residual liquid urine will always be entrained in the process gas after the gas-liquid separator, which will not only increase the consumption of urea, but also cause the pipeline and equipment to become walled and affect the production cycle;

[0018] 1. The device needs to be stopped regularly to open the blind plate at the bottom of the trap and discharge the material manually, which can only be produced intermittently and cannot be continuously produced;

[0019] 2. The melamine product obtained from the trap contains impurities such as by-products, and the quality cannot reach the target of the finished product. It can only be regarded as a crude product. The crude product needs to be dissolved, heated, filtered, cooled, crystallized, separated, dried, and crushed. The refined system can only get the finished product of melamine, which can only be produced in two steps;

[0020] 3. Long production process, high energy consumption and heavy pollution;

[0021] 4. The cooling and crystallization effect of the trap is greatly affected by the trap wall, the external environment temperature and the height of the material level. It is difficult to control the temperature before the 1# washing tower

Especially in summer, due to the high temperature of the external environment and the reduction of the effective space required for cooling and crystallization when the material level in the trap is high, the temperature before washing the 1# tower will be higher than usual, and the circulating gas will easily carry the material into the 1# Washing the tower with ammonia water will cause unnecessary material loss and increase in consumption;

[0022] 5. It takes more than 10 hours to stop the activation of the material before discharging each time and to raise the temperature of the system after starting up. During this period, the molten salt furnace, compressor, refrigerator and other energy-consuming equipment are all in no-load operation, that is, the increase Reduced coal consumption, electricity consumption, and affected production;

[0023] 6. It takes 6-8 hours for each discharging process. When discharging manually, a lot of triamine dust and residual ammonia will float into the air, which will cause environmental pollution and cause a lot of waste of materials;

[0024] 7. Due to the trap wall problem, it is necessary to manually beat the outer wall of the trap regularly, which is labor-intensive and produces a lot of noise pollution;

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