Abstract
Raising the efficiency and environmental friendliness of electric power generation from coal is the aim of numerous research groups today. The traditional approach based on the steam power cycle has reached its efficiency limit, prompted by materials development and maneuverability performance. The rival approach based on the combined cycle is also drawing nearer to its efficiency limit. However, there is a reserve for efficiency increase of the integrated gasification combined cycle, which has the energy efficiency at the level of modern steam-turbine power units. The limit of increase in efficiency is the efficiency of NGCC. One of the main problems of the IGCC is higher costs of receiving and preparing fuel gas for GTU. It would be reasonable to decrease the necessary amount of fuel gas in the power unit to minimize the costs. The effect can be reached by raising of the heat value of fuel gas, its heat content and the heat content of cycle air. On the example of the process flowsheet of the IGCC with a power of 500 MW, running on Kuznetsk bituminous coal, by means of software Thermoflex, the influence of the developed technical solutions on the efficiency of the power plant is considered. It is received that rise in steam-air blast temperature to 900°C leads to an increase in conversion efficiency up to 84.2%. An increase in temperature levels of fuel gas clean-up to 900°C leads to an increase in the IGCC efficiency gross/net by 3.42%. Cycle air heating reduces the need for fuel gas by 40% and raises the IGCC efficiency gross/net by 0.85-1.22%. The offered solutions for IGCC allow to exceed net efficiency of analogous plants by 1.8-2.3%.
Highlights
The combined gas-steam cycle of Brayton and Rankine approaches in the efficiency to its temperature maximum of ~1700°С [1]
According to DOE-NETL [2], operating IGCC on the basis of the oxygen gasifier and cold fuel gas clean-up (CGCU) fall behind those, that operate on ready-made standard fuel, by 10-12%
The total steam flow decreases with a syngas clean-up temperature increase from 157kg/s to 102kg/s at 900/900/900°С mode
Summary
The combined gas-steam cycle of Brayton and Rankine approaches in the efficiency to its temperature maximum of ~1700°С [1]. According to DOE-NETL [2], operating IGCC on the basis of the oxygen gasifier and cold fuel gas clean-up (CGCU) fall behind those, that operate on ready-made standard fuel, by 10-12%. According to MHI [4], the difference in efficiency between IGCC with air gasification and cold fuel gas clean-up and NGCC amounts to ~10%. The potential of the modern air-blown IGCC is not fully realized. The reason for this is the operation of ‘gasification island’, which is less effective than the operation on oxygen.
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