Process of synthesis at isotonic pressure

Among the processes where the syngas is produced from residual oil or pulverized coal (coal-water slurry) at 8.5 MPa, the following procedures can be adopted for the S3mthesis loop. 

One of the keys to achieve the synthesis process at 7.5 MPa is to use ammonia synthesis catalyst used in low temperature and low pressure. A301 and ZA-5 catalysts with wiistite as precursors have very high activity at low temperature and low pressure, which establish a good foundation for developing ammonia synthetic process at low pressure and created favorable conditions. Tables 9.4-9.7 have shown the operating data of A301 loaded in the bypass device in a plant which was measured in the actual industrial conditions. 

It is known from Table 9.4 that the outlet concentration and the net value of ammonia on A301 catalyst is up to 14.35% and 10.75% when the pressure is 7.0 MPa, the space velocity is 6000 h , the ratio of H2/N2 is 2.6, inert gas (mainly He) is less than 2%, the concentration of ammonia in the inlet gas is 3.6% and the size of the catalyst particle is 1.6-3.0 mm. Under the same condition, the outlet concentration of ammonia is 13.54% (425°C) and the net value of ammonia is 10% when the space velocity is 8000 h F In the lower space velocity, the outlet concentration of ammonia is higher. For example, when the space velocity is 3000 h F the concentration of ammonia is 16.55% and the net value of ammonia is 13%. In 7.5MPa, the net value of ammonia is up to 11.2%. 

Note The particle size of the catalyst is 1.6-3.0mm, volume 20cm , the composition of the inlet  

According to the estimation from some relative experts, it is economic when the net value of ammonia is more than 8.4% in low-pressure ammonia synthesis. When the A301 catalyst is in the conditions of 7.0 MPa and space velocity of 4000-8000 h , and the net value of ammonia is 10%-12%, it can meet the needs of economy to net value. Table 9.5 shows the amoimt of inlet syngas (S in) and catalyst volume (V at) needed at isotonic pressure ammonia plant with capacity of 1000 t/d at 7.0-7.5MPa. 

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