System and method for improving the performance of a heat recovery steam generator

A method of cleaning heat transfer surfaces in a heat recovery steam generator, comprising the steps of:

• receiving a flow of exhaust gas from a gas turbine;
• directing the exhaust gas through a heat exchanger and to a gas outlet of the heat recovery steam generator, the heat exchanger including a plurality of heat transfer surfaces configured to transfer heat from the exhaust gas to a fluid within the heat exchanger;
• decreasing a flow of the fluid through the heat exchanger for a predetermined time period, but maintaining the fluid within the heat exchanger, while maintaining the flow of exhaust through the heat exchanger, to increase a temperature of the heat transfer surfaces above a target temperature;
• and
• increasing the flow of the fluid through the heat exchanger after the predetermined time period, while maintaining the flow of exhaust through the heat exchanger.

A heat exchanger, comprising:

• a plurality of heat exchange tubes defining a flow pathway for a fluid, the heat exchange tubes including a plurality of heat transfer surfaces configured to transfer heat from an exhaust gas passing through the heat exchanger to the fluid within the tubes;
• and
• a valve associated with the heat exchanger and configured to regulate a flow of the fluid through the tubes of the heat exchanger the valve being controllable from an open position to a closed position to decrease the flow of the fluid through the tubes of the heat exchanger in order to effect an increase in a temperature of the heat transfer surfaces of the heat exchanger to clean the heat transfer surfaces, and controllable from the closed position to the open position to increase the flow of the fluid through the tubes of the heat exchanger, while maintaining the flow of exhaust gas through the heat exchanger;
• and
• a control unit in communication with the valve, the control unit being configured to control the valve to a reduced flow position sufficient to decrease the flow of the fluid through the tubes of the heat exchanger while maintaining the flow of exhaust gas through the heat exchanger;
• wherein in the reduced flow position, the fluid is maintained in the tubes of the heat exchanger;
• and
• wherein the heat exchanger is located downstream from an ammonia injection grid of a heat recovery steam generator.