Preparation of exhaust gas from a gas turbine for exhaust gas recirculation

A combined cycle power generating system comprising:

• a gas turbine unit having a compressor for compression of inlet air, a combustor for combustion of a fuel with the compressed inlet air to form an exhaust gas, and a gas turbine for expansion of the exhaust gas;
• a steam generator utilizing heat of the exhaust gas originating from the gas turbine for generation of steam;
• a steam turbine for expansion of the steam generated by the steam generator;
• a condenser utilizing water as a cooling medium for condensation of the steam originating from the steam turbine;
• a first cooling circuit for cooling of said water utilized as the cooling medium by the condenser and returning said water to the condenser, the first cooling circuit comprising a cooling tower for removal of heat from said water;
• and
• a recirculation line for passing at least a first portion of the exhaust gas originating from the gas turbine to the compressor;
• wherein the recirculation line comprises a first gas cooling and cleaning device having a first packed bed for contacting the first portion of the exhaust gas with a first cooling and absorption liquid in a counter current flow to perform cooling and absorption of the first portion of the recirculated exhaust gas in the first packed bed, to lower a temperature of the first portion of the exhaust gas and to remove contaminants from the first portion of the exhaust gas,
• wherein the system further comprises a second cooling circuit for cooling of the first cooling and absorption liquid utilized by the first gas cooling and cleaning device and returning it to the first gas cooling and cleaning device, the second cooling circuit comprising said cooling tower of the first cooling circuit for removal of heat from said first cooling and absorption liquid;
• wherein the system further comprising a pH control system configured to measure a pH of the first cooling and absorption liquid after exiting the cooling tower and prior to returning the cooled first cooling and absorption liquid to the first gas cooling and cleaning device, and to add a substance to the first cooling and absorption liquid to adjust the pH of the first cooling and absorption liquid in dependence upon the measurement prior to returning the cooled first cooling and absorption liquid to the first gas cooling and cleaning device;
• wherein the recirculation line is provided with a reagent injector located upstream of the first gas cooling and cleaning device;
• wherein the first cooling circuit and the second cooling circuit are in fluid communication with one another within the cooling tower such that acidity of the first cooling and absorption liquid reduces scaling resulting from alkalinity of the water utilized as the cooling medium.

An exhaust gas treatment system comprising:

• a turbine unit having a compressor for compression of inlet air, a combustor for combustion of a fuel with the compressed inlet air to form an exhaust gas, and a turbine for expansion of the exhaust gas;
• a recirculation line for passing at least a first portion of the exhaust gas originating from the turbine to the compressor, the recirculation line comprising a first gas cooling and cleaning device having a first packed bed for contacting the first portion of the exhaust gas with a first cooling and absorption liquid in a counter current flow to perform cooling and absorption of the recirculated exhaust gas in the first packed bed, to lower a temperature of the recirculated exhaust gas and to remove contaminants from the recirculated exhaust gas;
• a cooling circuit for cooling of the first cooling and absorption liquid utilized by the first gas cooling and cleaning device, and returning the first cooling and absorption liquid to the first gas cooling and cleaning device, the cooling circuit comprising a cooling tower that receives a primary supply of cooling water for condensation of steam from a steam turbine, and receives at least a portion of the first cooling and absorption liquid for removal of heat from said first cooling and absorption liquid;
• and
• a pH control system configured to measure a pH of the first cooling and absorption liquid after exiting the cooling tower and prior to returning the cooled first cooling and absorption liquid to the first gas cooling and cleaning device, and to add a substance to the first cooling and absorption liquid to adjust the pH of the first cooling and absorption liquid prior to returning the cooled first cooling and absorption liquid to the first gas cooling and cleaning device in dependence upon the measurement;
• wherein the recirculation line is provided with a reagent injector located upstream of the first gas cooling and cleaning device.