An energy-saving urea production system and its production process

Abstract

The invention belongs to the field of urea preparation, and particularly relates to an energy-saving urea production system and a production process thereof. The system comprises a CO2 compressor, an ammonium carbamate pump, a liquid ammonia pump and a urea synthesizer. The system is characterized in that the CO2 compressor is connected with the ammonium carbamate pump and the liquid ammonia pump, the liquid ammonia pump is connected with the urea synthesizer, a falling-film countercurrent medium-pressure decomposing tower and a heater, an ammonium carbamate condenser, an ammonium carbamate separator, a three-stage medium-pressure absorption tower and an evaporative ammonia refrigeration recoverer, a liquid ammonia buffer tank, an inert gas scrubber, a tail-gas ammonia cleaning fine purifier, a low-pressure decomposing tower and a heater, a dimethyl liquid preheater, a horizontal low-pressure absorber, a falling film type pre-evaporator, a one-stage evaporator and a one-stage evaporative condenser, a two-stage evaporator and a two-stage evaporative condenser, and a process wastewater desorption and hydrolysis tower are sequentially connected behind the urea synthesizer in sequence. The energy-saving urea production system has the advantages of low investment, low energy consumption, simple operation, high elasticity and the like, thereby the process technology has considerable economic benefit and social benefit.

Description

technical field [0001] The invention belongs to the field of urea preparation, in particular to an energy-saving urea production system and a production process thereof. Background technique [0002] Urea【CO(NH 2 ) 2 】Also known as carbonamide, carbonamide, urea, mainly exists in the urine excreted by humans and animals in nature. It has a wide range of uses, not only as a high-efficiency nitrogen fertilizer for agricultural production, but also as a chemical raw material commonly used in industry. [0003] Urea was first discovered in 1773 by the chemist Rouelle when he evaporated urine. In 1798, it was identified as a new substance by FoUrcray and Vauqudin and named as urea. In 1828, Uvohler produced urea when he heated ammonium cyanate in the laboratory, and the reaction was: Nl{4CNO=NH2c∞m2. In 1886, Bassroff succeeded in the first test, which is adopted by modern industry. A method for the direct synthesis of urea from ammonia and carbon dioxide. [0004] In 1922,...

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Problems solved by technology

[0014] However, the production process of the aqueous solution full circulation method in the above-mentioned prior art still has the following technical defects: first, the common urea synthesis tower of the existing aqueous solution full circulation process generally has the following problems: uneven mixing of materials, uneven distribution of reaction heat, and partial urea synthesis rate. Low' and other defects

However, to design a urea synthesis high-pressure ring, the technical difficulty of equipment design and manufacture is very high, and the investment is also expensive, which makes it difficult to increase the conversion rate of urea synthesis to about 73%.

[0015] Second, the consumption of products is higher

Due to the low conversion rate of the aqueous solution full circulation method, there are many materials that need to be heated and decomposed, resulting in high steam consumption. Therefore, the steam consumption of this process is relatively high. Generally, the steam consumption per ton of urea is about 1100kg.

At the same time, because the decomposed materials need to be recycled, the consumption of circulating cooling water is increased. Generally, the consumption of circulating cooling water per ton of urea is 140M 3

[0016] Third, the graded utilization of heat is poor

Although the domestic improved full circulation method of aqueous solution has high energy consumption, the investment is relatively low. Therefore, it is urgent to develop a urea production process with low investment and low energy consumption, which can reach the international advanced level.

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