Aqueous solution full-cycle urea energy-saving production process

Abstract

The invention relates to an aqueous solution full-cycle urea energy-saving production process. The aqueous solution full-cycle urea energy-saving production process comprises a high pressure synthesis step, a recycling step, an evaporation step and a desorption and hydrolysis step, wherein the a high pressure synthesis step comprises enabling raw material liquid ammonia from an ammonia tank to be sent through a liquid ammonia pump to a liquid ammonia preheater to be heated and divided into two paths, enabling one path to enter a tower top distributor of a synthesis tower, enabling the other path to enter the urea synthesis tower to undergo an isothermal high-pressure synthesis reaction, and enabling a reaction product to be out of the tower top; the recycling step comprises enabling the discharged reaction mixture to undergo medium-pressure and low-pressure decomposition absorption and then be sent into an evaporation system, and enabling tail gas to be vented after ammonia cleaning treatment; the evaporation step comprises performing preconcentration on urea solution from a low-temperature circulating system, utilizing expansion steam and steam condensate to perform heating reconcentration on the preconcentrated urine, and sending the urine to a urea granulation tower; and the desorption and hydrolysis step comprises pumping ammonium bicarbonate liquid to a desorption and hydrolysis system, and enabling content of urea and ammonia in desorbed cleaned water discharged out of the tower bottom to be no larger than 5ppm. Compared with the prior art, the aqueous solution full-cycle urea energy-saving production process is simple in process flow, good in operation controllability, low in material consumption, good in heat energy recycling, low in investment cost and little in pollution.

Description

technical field [0001] The invention relates to a urea production process, in particular to an energy-saving production process for full-circulation urea in aqueous solution. Background technique [0002] The existing urea production processes mainly include the traditional aqueous solution full-cycle production process and the stripping urea production process. The former has problems such as high consumption, tail gas flammable and explosive, and waste liquid containing ammonia and urea exceeding the standard. When the load is low, the load of the decomposition and recovery system increases, the consumption of ammonia and carbon dioxide increases, and the operation flexibility is poor and the operation requirements are harsh. Moreover, in the above two processes, the high-pressure synthesis system has a large number of equipment, the system is relatively complex, the operation controllability is poor, the recovery and utilization of heat energy is not good, and the investm...

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Problems solved by technology

[0003] The purpose of the present invention is to provide a simple process flow and easy operation in order to overcome the defects of the existing urea production process, such as relatively complex system, poor operation controllability, poor heat energy recovery and utilization, high material consumption, and high investment cost. Good controllability, low material consumption, good heat recovery and utilization, low investment cost, less pollution, energy-saving production process of full cycle urea in aqueous solution

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