OXYGEN-FREE STEAM GASIFICATION UNDER POLYGENERATION

Abstract

The relevance of the research is associated with the prospects for solid fuel deep processing with an unconventional method of producing superheated water vapor at thermal power plants with oxygen-free steam gasification. This will make it possible to create highly efficient energy technology enterprises at thermal power plants with the production of not only thermal and electrical energy, but also a variety of chemicals, in particular hydrogen and Fischer–Tropsch synthesis products. The main aim of the research is to substantiate the possibility and prospects of the implementation of steam oxygen-free gasification at thermal power plants in comparison with the widely used process of steam-oxygen gasification; to compare the steam-oxygen and steam oxygen-free gasification in terms of the cost of chemicals obtained from synthesis gas in the Fischer–Tropsch process. Objects: oxygen-free steam gasification of solid fuels under polygeneration conditions; method of producing superheated water vapor at thermal power plants for oxygen-free steam gasification. Methods: thermodynamic analysis of the operation of thermal power plants with integrated gasification process; analytical calculation of the oxygen-free steam gasification and its comparison with the steam-oxygen gasification; simplified calculation of the cost of Fischer–Tropsch synthesis products in comparison with steam oxygen-free gasification and steam-oxygen gasification. Results. This paper presents a new concept of polygeneration using oxygen-free steam gasification under conditions of steam production at thermal power plants. The new polygeneration concept assumes the production of water vapor with high temperature (up to 1000℃) and pressure (up to 2–3 MPa) with a high flow rate for the implementation of oxygen-free steam gasification of solid fuels. The concept is based on the thermodynamic justification of the operation of thermal power plants with a traditional steam-power cycle and the redistribution of material flows between a steam boiler and a steam turbine. A simplified economic assessment was made to calculate the price of syngas produced by steam oxygen-free gasification. It is shown that the production of synthesis gas by oxygen-free steam gasification in the new concept can be 15% cheaper than with the traditional steam-oxygen technology. This can be achieved if the ratio of the generated gas in steam oxygen-free gasification and steam-oxygen technologies is more than 3,5:1 respectively.

Keywords

• high temperature water vapor
• oxygen-free gasification
• renewable resources
• polygeneration
• fischer–tropsch synthesis