Dehydrogenation method of CO2 raw material gas for synthesizing urea

Abstract

A dehydrogenation method of CO2 charge gas for synthesizing urea includes the following steps: firstly, using active carbon or iron oxide normal-temp. desulfurizer to remover H2S from CO2 charge gas,then using the normal-temp. hydrolyst to hydrolyze orgnaic sulfur at 40-100 deg.C, then using active carbon or iron oxide refined desulfurizer to make desulfurization up to total sulfur content in the gas be less than 0.5 ppm, then using dehydrogenation catalyst containing Pt-Pd dual noble metals or TH-3 type rare earth metal element-contained Pt-Pd dual noble metals dehydrogenation catalyst to mare dehydrogenation, removing H2 from CO2 charge gas and making H2 content be less than 300 ppm under the conditions of that its inlet temp. is 120-250 deg.C and pressure is les sthan 20 MPa. The saidmethod is applicable to urea plant using coal or heavy oil to produce gas, can eliminate the hazard due to accumulation of H2, and can prolong catalyst life to about 5 years.

Description

technical field [0001] The invention relates to the dehydrogenation technology of raw material gas for urea synthesis. Background technique [0002] To prevent corrosion of the urea synthesis system, it is necessary to 2 Add O to raw gas 2 , which will result in the synthesis of high-pressure or medium-pressure tail gas H in urea production 2 Can cause explosion when the content accumulates too high, especially in CO 2 It is easy to occur in the steam stripping method and the full circulation method of aqueous solution, and explosion accidents have occurred in urea plants at home and abroad. According to investigations, explosions have occurred in almost every part of the urea section of a medium-sized nitrogen fertilizer plant in my country, which is a long-standing major safety hazard in urea production. At present, in order to avoid the hydrogen content in the tail gas falling in the explosion zone, most urea plants in China adopt the method of increasing the ammonia ...

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Problems solved by technology

However, most small and medium-sized urea plants in my country use coal as raw material, and CO 2 The sulfur content in the raw material is high, H 2 S is 3-500ppm, COS is 3-15ppm, and total sulfur Ts is 10-500ppm. At this time, the dehydrogenation catalyst cannot be used even though it has a certain anti-sulfur performance, and its life is only about one month. Therefore, the development is suitable for coal as raw material. The new technology of urea synthesis and dehydrogenation has important economic significance

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