An innovative ceramic high temperature plate-fin heat exchanger for EFCC processes

Kurzfassung

For heat exchanger applications needing extreme operation temperatures such as in the field of power generation or heat recovery a ceramic plate-fin heat exchanger is proposed, based on the “Offset Strip Fin” design. At first the principal selection of the materials and the Environmental Barrier Coating (EBC) needed to protect the substrate from the aggressive flue gases is explained. Then a manufacturing process is described able to incorporate the EBC on all parts having contact to the flue gases. On the basis of a representative biomass fuelled Externally Fired Combined Cycle (EFCC) process with an electrical output of 6 MW the thermal design is presented resulting in a ceramic heat exchanger block of weight 4.0 t and surface area densities of 443 mm²/mm³ on the flue gas side and 286 mm²/mm³ on the pressurized process gas side. To ensure the thermo mechanical integrity investigations of both the steady state operation and the case of an emergency stop were investigated by means of Finite Element Method (FEM). In the case of steady state operation a security factor of 8.5 was achieved. This demonstrates that the stresses in both cases are controllable.