Supercritical Pressure Coal-Fired Thermal Power Plant

Thermal power is generally classified into three categories based on the type of fuel, known as liquefied natural gas (LNG), petroleum and coal. While petroleum used to be used as fuel in most situations, the utilization ratios of LNG and coal have increased since the first oil crisis of 1973 as petroleum use has decreased over the years.
In 2008, statistics indicated that in Japan petroleum makes up only 12% of power usage, while LNG makes up 28% and coal 25%. The use of coal-fired power generation is expected to increase with a long-term future in Japan as coal reserves are enormously larger than that of LNG or petroleum. In fact, it is estimated that coal mining will continue for at least another century. Additionally, the consistency and global availability of coal is ample and therefore less likely to cause the type of political issues that exist around the petroleum supply. In addition, coal will continue to be an essential source of energy mainly because of its price, which is more stable than petroleum.

While CO2 emissions are unavoidable when using coal-fired power generation for electricity due to its nature as a fossil fuel, it is undeniable that it is a major factor in global warming. In addition, coal-fired power generation can be problematic because it does emit the largest volume of CO2 for power generation using fossil fuels.
However, it's worth considering that a reduction in CO2 emissions from coal-fired power generation will have a dramatic effect on the prevention of global warming. Since coal-fired power generation must continue to be a leading global power generation method; Hitachi is addressing this important issue. Hitachi has developed the world's leading supercritical pressure and ultra-supercritical pressure coal-fired power generation technologies (*1). These new technologies are expected to contribute to the reduction of CO2 emissions by achieving more efficient coal-fired power generation.

The efficiency of coal-fired power generation is primarily dependent on when the steam generated from the boiler and the combustion of coal is at a more elevated temperature and pressure. However, the strength of the boiler decreases when used at high temperatures and pressure for long periods of time.
In an effort to solve this problem, Hitachi has reviewed the design by focusing on strength and heat transmission, and developed high-strength steel. Hitachi has also established ultra-supercritical pressure power generation technology, which is able to withstand high temperatures in the (600 degrees) class and high pressure (25MPa, about 250 times greater than atmospheric pressure). This approach is resulting in the reduction of CO2 emissions by 7% in ultra-supercritical pressure power generation, compared with current sub-critical pressure power generation.
Coal-fired power generation in Japan is operated with a total efficiency rate of 40% or more, the highest rate in the world. This is due to the recent widespread utilization of supercritical pressure and ultra-supercritical pressure power generation. Moreover, Hitachi has promoted the development of technology at higher temperatures and pressure (in the 700 degrees). In an effort to curb the effects of global warming, Hitachi is applying a practical application of coal gasification power generation and the development of oxygen-burning coal-fired thermal power.