CO_2 COMPRESSORS WITH INTERSTAGE COOLING FOR CCS APPLICATIONS: EFFECTS OF COMPRESSOR TYPE

摘要

Comparative analyses of compressor and interstage heat exchanger performance characteristics were carried out for a RAMGEN compressor, an in-line compressor and an integrally geared compressor for the cases of an oxy-fired boiler and MEA and chilled ammonia post-combustion CO_2 capture systems. The predicted results show that because of large differences in inlet pressure to the first compressor stage, the compressor power requirements will be greatest for oxyfired boilers and smallest for chilled ammonia CO_2 capture systems. The analyses also show that of the three compressors which were analyzed, the RAMGEN compressor has the largest predicted power requirement and the integrally geared compressor has the smallest. These differences are due primarily to the effects of multistage compression with intercooling on shaft power, with the power requirement decreasing with increasing number of compression stages. Predicted results are also presented on cooling water exit temperatures and heat exchanger surface areas as functions of cooling water to CO_2 flow rate ratio. These show that the RAMGEN compressor would result in the highest exit water temperatures and the integrallygeared compressor would result in the lowest. Higher water exit temperatures will make it possible to take greater advantage of use of captured heat for improving unit heat rate. The predicted results also show that due to relatively low compressor stage CO_2 exit temperatures and a relatively large number of compressor stages, intercoolers for integrally geared compressors will require the largest and most expensive array of heat exchangers for each type of capture system.