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Production method of thiourea continuous crystallization

A production method and technology of thiourea, applied in the field of continuous crystallization of thiourea, can solve problems affecting crystallization effect and production efficiency, aggravating fouling, affecting crystallization effect, etc.

Active Publication Date: 2019-11-12
SHANDONG EFIRM BIOCHEMISTRY & ENVIRONMENTAL PROTECTION CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

For example, the thiourea purification production methods disclosed in patent applications CN201711141587 and CN201810815034 are all batch crystallization methods. The batch crystallization production process has the advantages of simple production equipment and strong production controllability. At the same time, there are also differences in different batches of operations. The disadvantages of poor quality stability, low efficiency of industrialized large-scale production, and large equipment footprint
Hebei Xinji Chemical Group Co., Ltd. also discloses a thiourea continuous crystallization device (CN201720994840), which uses an Oslo crystallizer for thiourea production. In actual production, the material side surface of the heat exchanger in the Oslo crystallizer is prone to fouling, which affects The heat exchange effect will affect the crystallization effect; after a period of operation, it needs to be shut down for cleaning, because the thiourea feed liquid contains a large amount of calcium ions, which aggravates the formation of scaling and affects the crystallization effect and production efficiency

Method used

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  • Production method of thiourea continuous crystallization
  • Production method of thiourea continuous crystallization
  • Production method of thiourea continuous crystallization

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0056] Add 22% thiourea feed liquid into the feed liquid buffer tank before crystallization, and control the feed liquid temperature to 40°C. A two-stage continuous crystallizer is selected, and the refrigerant used for cooling each stage of the crystallizer is opened separately. The first stage is fed with circulating water at a temperature of 25°C, and the second stage is fed with cold water at 8°C. Turn on the feed liquid delivery pump, inject the thiourea feed liquid into the first-stage crystallizer, and control the flow rate of the refrigerant. The cooling rate of the thiourea feed liquid in the first-stage crystallizer is 3°C / h, and the residence time is 2h; The cooling rate in the 2-stage crystallizer is 8°C / h, and the residence time is 3h. The crystallization operation process is recorded, and the crystallized feed liquid is centrifuged and dried by a centrifuge to obtain a thiourea product.

Embodiment 2

[0058] Add 22% thiourea feed liquid into the feed liquid buffer tank before crystallization, and control the feed liquid temperature to 40°C. Choose a three-stage continuous crystallizer (such as figure 1 shown), turn on the cooling medium for each stage of the crystallizer respectively, the first stage is fed with circulating water at a temperature of 27°C, the second stage is passed with 20°C circulating water, and the third stage is fed with 7°C chilled water. Turn on the feed liquid delivery pump, inject the thiourea feed liquid into the crystallizer of the first stage, and control the flow rate of the refrigerant. The cooling rate of the thiourea feed liquid in the crystallizer of the first stage is 3°C / h, and the residence time is 1.5h; The cooling rate in the second stage crystallizer is 5°C / h, and the residence time is 1h; the cooling rate in the third stage crystallizer is 11°C / h, and the residence time is 1.5h. The crystallization operation process is recorded, and ...

Embodiment 3

[0060]Add 22% thiourea feed liquid into the feed liquid buffer tank before crystallization, and control the feed liquid temperature to 40°C. Select three sections of continuous crystallizers, open each section of the crystallizer cooling medium respectively, the first section is fed with circulating water at a temperature of 27°C, the second section is fed with 20°C circulating water, and the third section is fed with 7°C refrigeration water. Turn on the feed liquid delivery pump, inject the thiourea feed liquid into the first-stage crystallizer, and control the flow rate of the refrigerant. The cooling rate of the thiourea feed liquid in the first-stage crystallizer is 2°C / h, and the residence time is 2.5h; The cooling rate in the first stage crystallizer is 5°C / h, and the residence time is 1h; the cooling rate in the third stage crystallizer is 11°C / h, and the residence time is 1.5h. The crystallized feed liquid is centrifuged and dried by a centrifuge to obtain a thiourea ...

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Abstract

The invention provides a production method of thiourea continuous crystallization. According to the method, a n-stage series crystallizer is used to carry out continuous cooling crystallization of a thiourea material liquid to obtain thiourea, wherein n is greater than or equal to 2; in the n-stage series crystallizer, from the first-stage crystallizer to the nth-stage crystallizer, a cooling rateV<x> is gradually increased, and a refrigerant temperature T<x> is gradually decreased; and in each-stage crystallizer, a temperature difference between the inlet refrigerant and the inlet thiourea material liquid is less than or equal to 20 DEG C. Through the above-mentioned segmented temperature-controlled crystallization manner, occurrence of explosive nucleation in the crystal nucleation stage can be avoided, and a crystallization time and a production cycle can be shortened. Results show that the production method greatly improves production efficiency while obtaining a same quality product as an existing intermittent production method. In addition, the production method can improve stability of product quality, and overcomes the problem of large difference in quality between different batch products in the existing intermittent production method.

Description

technical field [0001] The invention relates to the technical field of chemical production, in particular to a production method for continuous crystallization of thiourea. Background technique [0002] Thiourea, the molecular formula is (NH 2 ) 2 CS, relative molecular weight 76.12, white orthorhombic or needle-like bright crystals; flammable, melting point 170-180°C, pyrolysis; soluble in cold water and ethanol, almost insoluble in ether. It can be used as a raw material for the manufacture of medicines, dyes, resins, and compression molding powders, as well as a vulcanization accelerator for rubber and a flotation agent for metal minerals. Therefore, thiourea is a widely used chemical product, and efficient production of thiourea is of great significance. [0003] At present, thiourea is mainly prepared in the following manner in industry: water, lime nitrogen (calcium cyanamide) and hydrogen sulfide gas are used as raw materials, and the absorption synthesis reaction ...

Claims

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Application Information

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IPC IPC(8): B01D9/02C07C335/02
CPCB01D9/0009B01D9/0059B01D2009/0086C07C335/02
Inventor 张宁崔卫华梁万根曹斌孙作龙刘冠宏
Owner SHANDONG EFIRM BIOCHEMISTRY & ENVIRONMENTAL PROTECTION CO LTD