Carbon Dioxide Removal in High-Pressure IGCC Power Plants

2 CARBON DIOXIDE REMOVAL IN HIGH-PRESSURE IGCC POWER PLANTS 

In the previous section, we studied the absorption of carbon dioxide in a low-pressure system in which a reactive amine was used. Now we want to consider a significantly different situation in which the absorber pressure is quite high, in fact high enough so that physical absorption in a suitable solvent is effective. 

The numerical example considered is an IGCC power plant that generates 773 MW of total electric power. The system is based on a paper by Robinson and Luyben.  

In the low-pressure amine absorption system, a low stripper pressure is used to keep stripper reboiler duty as small as possible. In the high-pressure TEG absorption system, there is a smaller dependence of reboiler energy on pressure. A higher pressure in the stripper reduces the compression costs to raise the recovered carbon dioxide gas up to the required pipeline pressure for sequestration. Therefore, there is an optimum economic stripper pressure (ISOpsia) that balances compression costs with stripper reboder energy cost. The stripper distillate is cooled to 110 °F to minimize the amount of water in carbon dioxide gas product from the stripper reflux drum. Diameters of the columns are very large due to the enormous throughput. 

The losses of the very heavy solvent (DME—PEG) are very small in both the off gas from the absorber and in the vapor product from the stripper reflux drum. The loss is about 0.35 lb mol/h. The loss of water in the absorber off-gas is 785.1 lb mol/h. The loss of water in the stripper vapor is 176.7 lb molTh. The amount of water coming into the absorber in the feed gas is 122.2 lb mol/h. Therefore, the amount of water that must be fed into the system is 839.6 lb mol/h of makeup fresh water. 

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CARBON DIOXIDE REMOVAL IN HIGH-PRESSURE IGCC POWER PLANTS 419 20% disturbances in gas feed... 

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