In phase 1 of the project, a conceptual design of a coal-fired high performance power system was developed, and small scale R & D was done in critical areas of the design. The current Phase of the project includes development through the pilot plant stage, and design of a prototype plant that would be built in Phase 3. Goals have been identified that relate to the efficiency, emissions, costs and general operation of the system. The base case arrangement of the HIPPS cycle is shown in Figure 1. It is a combined cycle plant. This arrangement is referred to as the All Coal HIPPS because it does not require any other fuels for normal operation. A fluidized bed, air blown pyrolyzer converts coal into fuel gas and char. The char is fired in a high temperature advanced furnace (HITAF) which heats both air for a gas turbine and steam for a steam turbine. The air is heated up to 1400F in the HITAF, and the tube banks for heating air are constructed of alloy tubes. The fuel gas from the pyrolyzer goes to a topping combustor where it is used to raise the air entering the gas turbine to 2350F. In addition in the HITAF, steam duty is achieved with a heat recovery steam generator in the gas turbine exhaust stream and economizers in the HITAF flue gas exhaust stream. An alternative HIPPS cycle is shown in Figure 2. This arrangement uses a ceramic air heater to heat the air to temperatures above what can be achieved with alloy tubes. This arrangement is referred as the 35% natural gas HIPPS. A pyrolyzer is used as in the base case HIPPS, but the fuel gas generated is fired upstream of the ceramic air heater instead of in the topping combustor. Gas turbine air is heated to 1400 F in alloy tubes the same as in the All Coal HIPPS. This air then goes to the ceramic air heater where it is heated further before going to the topping combustor. The temperature of the air leaving the ceramic air heater will depend on technological developments in that component.

In the third quarter of calendar year 1996, 13 days of combust-boiler tests were performed, including 3 days of tests on a parallel DOE sponsored project on sulfur retention in a stagging combustor. Between tests, modifications and improvements that were indicated by these tests were implemented. This brings the total number of test days to the end of September in the task 5 effort to 41, increased to 46 as of the date of this Report, 10/27/96. This compares with a total of 63 test days needed to complete the task 5 test effort. As reported previously, the only major modification to the Williamsport combustor has been the addition of a new downstream section, which lengthens the combustor and improves the combustor-boiler interface. The original combustor section, which includes the fuel, air, and cooling water delivery systems remained basically unchanged. Only the refractory liner was completely replaced, a task which occurs on an annual basis in all commercial stagging utility combustors. Therefore, this combustor has been operated since 1988 without replacement.