Optimization of Heat Recovery Steam Generators (HRSG)

Applications

Splitting boilers and heat recovery steam generators can be applied to coal boilers and other heat exchangers that require quenching of the hot liquid such as pressurized oxy-coal combustion (OCC).

Problem Addressed

Reducing the capital cost and/or increasing efficiency of power generation is highly desirable especially given the ever growing market of electric power generation. This design decreases the power requirements by 18% (corresponding to 0.15 percentage points in cycle efficiency increase) while simultaneously reducing the area by 12%.

Technology

This design splits the hot combustion gas prior to its dilution by the secondary recycling stream. The flue gas entering the HRSG decreases in temperature as it exchanges thermal energy with the working fluid of the Rankine cycle. The split concept enhances the rate of thermal energy transfer by increasing the average temperature between the involved streams, and reduces the compression requirements by reducing the flow rates and/or pressure losses compared to the conventional operation. For a given HRSG thermal load, the splitting process can increase the overall temperature difference between the streams of the exchanger, particularly avoiding small differences which require the most heat transfer area. The higher average temperature differences imply smaller exchange area, and lower recycling requirements imply lower pressure drops and lower compensation power requirements (CPR).

Advantages

  • Decreases power requirements
  • Decreases heat transfer area
  • Can be retrofitted to existing heat exchangers