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Method for continuously dissolving urea and propylene glycol (or ethylene glycol)

A technology of propylene glycol and ethylene glycol, applied in the direction of organic chemistry, etc., can solve problems such as environmental pollution, potential safety hazards, and no stable, safe and continuous dissolution method of urea and propylene (or ethylene) glycol.

Pending Publication Date: 2020-11-13
EAST CHINA UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Since urea is solid at normal temperature, if it is directly added to the reactor, there will be the following problems: First, because the air will be entrained between the urea particles, the amount of air leaked into the reactor will be large, the vacuum system will pump a lot of air, and the energy consumption of the vacuum pump will be large. The second is that the leakage of air will form an explosive mixed gas with the ammonia produced by the reaction, which has potential safety hazards; the third is that there is more air in the ammonia gas, which will affect the subsequent ammonia recovery, reduce the ammonia recovery rate, and increase production costs.
However, in the case of heating, even without a catalyst, urea will react with propylene glycol (or ethylene glycol) to release ammonia gas. If it is not treated, it will cause ammonia gas leakage, pollute the environment, and endanger the health of workshop workers; If it is treated by adding a water tank above the stirring tank, and the ammonia gas enters the water tank for absorption, a lot of low-concentration ammonia water will be added, which will increase the difficulty and cost of treatment
[0006] Therefore, in the prior art, there is no method for stable, safe and continuous dissolution of urea and propylene (or ethylene) glycol

Method used

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  • Method for continuously dissolving urea and propylene glycol (or ethylene glycol)

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Embodiment 1

[0028] In the 40,000 tons / year urea two-step dimethyl carbonate production plant, the continuous dissolution of urea and propylene glycol is carried out in a single tank. The volume of the stirred tank is 25m 3 , urea at 3705kg / h and propylene glycol at 8447kg / h are continuously added to the stirring tank, the urea feeding pipe is immersed 100cm below the liquid surface, the stirring tank is heated to 100°C with steam, and the pressure is kept at 90kPa through the vacuum regulating valve, and the generated propylene glycol is saturated The vapor pressure and ammonia gas enter the condenser, the condensation temperature is -5°C, the condensed propylene glycol liquid is returned to the stirring tank, and the non-condensable ammonia gas enters the subsequent recovery device. The material in the stirred tank (urea has been completely dissolved) is transported to the subsequent urea alcoholysis reactor through the pump at the bottom of the tank, and the liquid level of the stirred ...

Embodiment 2

[0030]In the 100,000 tons / year urea two-step dimethyl carbonate production plant, two tanks are connected in series for continuous dissolution of urea and propylene glycol. The volumes of the stirred tank (1) and the tank (2) are both 30m 3 , urea at 9530kg / h and propylene glycol at 16900kg / h are continuously added to the stirring tank (1), the urea feeding pipe is immersed 80cm below the liquid surface, the stirring tank is heated to 90°C by steam, and the pressure is kept at 95kPa through the vacuum regulating valve, resulting in The saturated vapor pressure of propylene glycol and ammonia gas enter the condenser (2), the condensation temperature is 0°C, the condensed propylene glycol liquid is returned to the stirring tank, and the ammonia gas enters the subsequent recovery device. The material in the kettle (1) automatically flows into the kettle (2) through the pipeline at the bottom of the kettle. The kettle (2) is heated to 90°C with steam, and the pressure is kept at 9...

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Abstract

The invention relates to a method for continuously dissolving urea and propylene glycol (or ethylene glycol). The method comprises the following main steps: in a dissolving kettle, using urea and propylene glycol or ethylene glycol as raw materials, continuously dissolving under continuous heating and negative pressure to obtain a homogeneous reaction material for continuously producing propylenecarbonate or ethylene carbonate. According to the method, ammonia gas leakage, environmental pollution and harm to body health of workshop workers cannot be caused in the urea dissolving process, meanwhile, the recovery rate of ammonia is also increased, and the method has the advantages of low energy consumption, simple process and the like; the method is high in automation degree, the labor intensity is greatly reduced, the labor efficiency is improved, raw materials can be continuously and stably provided for production of propylene carbonate (or ethylene carbonate) through urea alcoholysisreaction, and undoubtedly, good development prospects and huge economic benefits are brought to the dimethyl carbonate industry.

Description

technical field [0001] The invention belongs to the technical field of chemical industry, and in particular relates to a method for continuously dissolving urea and propylene glycol or ethylene glycol, and continuously preparing propylene carbonate or ethylene carbonate through urea alcoholysis reaction. Background technique [0002] Propylene carbonate and ethylene carbonate are high-boiling and highly polar organic solvents with excellent performance, and are also important organic chemicals, which have been widely used in organic synthesis, gas separation, battery dielectric, and metal extraction. They can be used as plasticizers, spinning solvents, dispersants for water-soluble dyes and pigments, oily solvents, extractants for olefins and aromatics, used as decarbonization solvents in nitrogen fertilizer production, and used in second-generation lithium-ion batteries Used as electrolyte to protect graphite anode. It is a high-efficiency desulfurization and decarbonizati...

Claims

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Application Information

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IPC IPC(8): C07D317/36C07D317/38
CPCC07D317/36C07D317/38
Inventor 方云进沈卫华
Owner EAST CHINA UNIV OF SCI & TECH