Crystallizing kettle temperature control system and control method

Abstract

The invention discloses a crystallizing kettle temperature control system and control method, wherein the temperature control system is composed of a crystallizing kettle provided with an outer coil pipe, a water storage tank, a heat exchanger, a DCS control system and a conveying pipeline; before materials enter a crystallizing kettle, steam is introduced, and the crystallizing kettle is preheated by heating circulating water; when the crystallizing operation begins, a steam regulating valve is closed, freezing water is introduced, the temperature of the circulating water is reduced by a heatexchanger, and the crystallization kettle is cooled. The temperature control method DCS controls to set different temperature difference [delta]t according to different temperature t sections of thecrystallizing kettle to ensure the quality of crystallization products and improve the crystallization speed of the products. The crystallizing kettle temperature control system integrates heating andcooling of the crystallizing kettle, can flexibly and steadily control the temperature of the crystallizing kettle, has a wide range of temperature control, can also achieve a good cooling effect forthe crystallizing reaction with the terminal temperature of crystallization as low as 5 DEG C, can effectively and smoothly control the temperature in the crystallizing kettle, ensures the smooth progress of the crystallizing process, and also increases the lower limit of the cooling.

Description

Technical field [0001] The invention relates to the technical field of industrial automation control, in particular to a crystallization kettle temperature control system and control method. Background technique [0002] Cooling crystallization is an important method for product purification in the chemical industry. During the cooling and crystallization process, the temperature of the crystallization kettle is crucial to the smooth progress of the crystallization process. If the temperature is not properly controlled, it will affect the crystal quality of the product and slow down the crystallization speed of the product. At present, there are few related documents about the continuous cooling temperature control method of the crystallization process. [0003] The patent application number is 200810012328.4 A jacketed reactor temperature control system and its temperature control method, which discloses a method for controlling the temperature in the reactor by adjusting the te...

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Problems solved by technology

[0006] However, the existing patents generally have the problems of low water recycling rate and narrow cooling range for heat exchange systems. For example, the water used for heat exchange is not recycled in the patent application number 200810012328.4; while the patent application number is 201220407389.8 Although there is a water tank to store water, it is necessary to add fresh cooling water to the heat exchange system every time the reactor is cooled down. The degree of water recycling in the heat exchange system is not high. Since the cooling water is used as the refrigerant, the above patent has no effect on the crystallization end point. Lower temperature reactions have certain limitations

Another example is that in the patent application number 201720697414.3, cold water at -15°C to -10°C is used as the refrigerant, which can effectively reduce the temperature of the reactor jacket and thereby reduce the temperature inside the reactor. Concentration of agent, resulting in cold water can not be recycled

In particular, the prior art patent application numbers 200810012328.4, 201220407389.8 and 201720697414.3 did not detect and control the temperature t of the crystallization tank and the temperature difference Δt between the outer coil and the crystallization tank

As a result, when the material just enters the crystallization tank, the temperature difference at the initial stage of crystallization is relatively large, and the temperature on the wall side of the crystallization tank drops too quickly. Due to the high concentration of the product contained in the mother liquor, crystal scars are formed on the wall of the crystallization tank, and the initial crystallization product formed Large particles, low purity, poor quality

However, the temperature difference in the final stage of crystallization is small, and because the product concentration in the mother liquor is low, the yield of crystallized products in the final stage is low, the heat transfer rate is small, and the crystallization speed is slow.

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