Abstracts Category : Other

Heat Exchanger Model Optimization of Compressed Industrial Flue Gas to Improve Department of Energys Carbon Capture Simulation Tools

by Lisa-Marie Clarke

The Department of Energys Carbon Capture Simulation Initiative models are an advanced method of analyzing emerging technologies at an amazing depth. To further the usability of the membrane model in industry, a compressor and heat exchanger were optimized. Industrial flue gas compositions were used for the creation of the model based on information provided from the Department of Energy. An isentropic compressor was used to compress the flue gas from 1 to 2 bar and a counter current heat exchanger was added to cool the gas to an acceptable operating temperature of 25C. 3 different coolants were analyzed using the shortcut HeatX method in Aspen Plus V8.8 to determine the best heat exchanger for the model. The 3 coolants analyzed were water, an ethylene glycol (EG) /water mixture, and a dimethyl ether (DME) /water mixture. All 3 coolant streams consisted of an inlet temperature of 20C and pressure of 1 bar throughout the analysis. The heatexchangers were tested for optimal compositions by minimizing the required area. Based on the results, ethylene glycol impedes heat exchange, however, because of its other qualities (corrosion and freezing protection), it is standard to have a 20 wt% solution with water. The dimethyl ether solution was found to have an optimal concentration of 40 wt%. Once optimal concentrations of the coolants were found, the heat exchangers were compared against each other. The flue gas stream of 1,000 kg/hr and 100,000 kg/hr were used to compare heat exchanger areas. Coolant flow rate streams of 1,000 kg/hr and 50,000 kg/hr were used for each comparison as well. Based on the results, the dimethyl ether solution had the best each exchange by requiring the smallest area of about 2.5 sqm, and 346 sqm, respectively. A cost analysis on each exchanger was also conducted to compare the utility and capital costs of each structure. Based on the results, the EG, water and DME exchangers had utility costs of11 /gal, 0/gal, and 1 /kg, assuming the water was process water already on site. The EG, water and DME exchanger had capital costs of 60,200, 59,100, and 59,900, respectively. The area results were not the only considerations in choosing the better heat exchanger configuration. Safety, availability, and corrosion were also taken into account. Because of this, even though the exchanger area would need to be slightly larger, the ethylene glycol mixture was chosen because of its previously mentioned functions to help maintain the process, its wide availability as a process coolant, and smallest concentration amount. Once the heat exchanger and compressor model was developed, it was configured in SimSinter to create a usable simulation package that industry users can incorporate into their designs. This format will allow industry users to optimize and analyze models easily in FOQUS and develop new carbon capture models ready for industry use. ( en )