(3) Repowering
The technology to increase the performance by additionally providing the gas turbine, etc. on the existing boiler steam turbine system, is referred to as the repowering.
Fig.3 shows an example in which a coal-fired boiler of an old coal-fired thermal power plant which was constructed in 1964, and has been operated for 100,000 hours is dismantled, the ABB-GT26 type gas turbine is additionally installed, natural gas is fired therein, its exhaust gas is led to the waste heat boiler, the steam under the same steam conditions is produced to drive the historical steam turbine. This plant is No.4 Generator of the Rheinhafen Power Station of Badenwerk Power Company in Karlsruhe City along the Rhein in Germany. This plant has been operated for 34 years, and its operation time is 100,000 hours which is relatively short for the age, and its steam turbine is sound, and even after the repowering, it is still serviceable only by partly modification. Through the modification, the output of the steam turbine of 100 MW was increased to 123 MW, and the total output reaches 360 MW including 240 MW of the gas turbine, and the thermal efficiency is increased from 38% to 58% (LHV). The temperature of the exhaust gas of GT 26 is as high as 613℃, and the steam condition of 153 bar at 540℃ for the high pressure steam turbine is obtained.
As illustrated in this example, the thermal efficiency is at most 44% (HHV) even with the large latest thermal power station only by the boiler and the steam turbine plant, and it is not easy to increase the thermal efficiency by another 1%. However, the total thermal efficiency can be greatly improved even with medium to small coal-fired power stations if the boilers and the steam turbine plants are combined with the gas turbine for hybridization following the principle of the thermodynamics to use the heat completely from the high temperature to the low temperature.
(4) Gas Turbine Combined with refuse-burning power generation
The problem of the general municipal refuse of about 140,000 tons which is daily discharged all over Japan raises a social problem. About 74% of the refuse is incinerated now, 15% thereof is reclaimed, and the rest is treated through the compost, etc. There are about 1,900 refuse burning facilities in Japan; about 440 refuse burning facilities are of 24-hour continuous incineration type with the treatment capacity of total 130,000 tons/day, and the remainders are medium to small incinerators of quasi-continuous treatment type or of batch type. Among these facilities, 178 facilities generate the electric power making use of the incineration heat with the total capacity of 734,000 kW at the end of 1997, and only 87 facilities sell the power after subtracting their own demand. If the power generation of about 600 kWh/ton refuse as high as that of Europe and USA is obtained by the refuse of about 100,000 ton/day to be incinerated, the total capacity will be about 2.50 million kW by itself, which is a fairly large latent power-generating capacity. It will be the first step to eliminate the shortage of the power sources that the inhabitants in large cities are awakened to the impartiality that they enjoy only the electric power while forcing the nuclear power generation on others, and show the attitude of generating even a part of the power demand by themselves based on the wastes.
