| The air separation pre-cooling system in Phase ? 400,000 ton/year plant of Shaanxi Shenmu Chemical Industry Co.,Ltd.was designed without chillers.After several years of operation,it was found that the implementation of the project area increased the summer hot weather,the average temperature increased,which need a higher circulating cooling water ratio.Especially in summer the air temperature of the air cooling tower reached up to 18 ?,and the moisture content in the air rises,causing a large increase in the adsorption load of the molecular sieve in the purification system,bring a lot of difficulties in regeneration and activation of the molecular sieve such as insufficient adsorption capacity of the molecular sieve,etc.This poses a serious threat to the safe operation of equipment in the hot summer season.At the same time,the increase in exchanger heat load need more amount of expansion air and energy consumption,which caused hidden danger to the air-separation system,sometimes the main heat exchangers are blocked by dry ice,and are heated and blown away by parking.In order to eliminate potential safety hazards and guarantee the air-separation unit performed in good condition,it's urgent to innovate the air separation pre-cooling system to improve production efficiency and unit operation safety.This paper aims at how to reduce the air temperature at the outlet of the air cooling tower to the design specification of 13 ?.Based on a large number of investigations,process analysis,and equipment load capacity calculations,chilled water is adopted to reduces the temperature of the air cooling tower and the direct contact heat exchange area.At the same time,the matching relationship between the freezing water temperature and the air temperature of the air cooling tower is examined.Based on the simulation calculation of the packed tower,the chilled water is considered to have a flow rate of 287 m3/h with a temperature of 7 ? can meet the design requirements of the top gas outlet temperature.The results of this study were applied to the technical transformation of the plant.The practical running shows by adding chillers,the temperature of the chilled water was effectively decreased,and the chilled water was normally operated in summer,which eliminates the hidden threaten posed by the high temperature and achieving the safety of the air separation plant,at the meanwhile,saving energy and reducing consumption. |
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