Coal gasifier and using method thereof

A coal gasifier which comprises a cylindrical gasification chamber, a plurality of burners for injecting and burning a mixture of coal and gasification agent provided on a side wall of said gasification chamber and arranged to direct the mixture in a tangential direction along said side wall, a slag cooling chamber provided under said gasification chamber via a slag tap, and a heat recovery vessel provided on said gasification chamber for cooling gas generated in said gasification chamber and for recovering heat from the generated gas, said heat recovery vessel comprising an inlet part connected to an upper outlet end of the gasification chamber and a body part connected to the inlet part;

• an inner wall surface cooling mechanism for cooling surfaces of inner walls of each of the inlet part and the body part of said heat recovery vessel by circulating cooling medium in a flow path provided in each of the inner walls, the inner wall surface of the inlet part of said heat recovery vessel being made of metal;
• a plurality of peeling gas injection holes provided in said inner wall surface of the inlet part and arranged to direct the injected gas in a tangential direction of said inner wall surface for peeling deposits of ash on said inner wall surface, said injected gas being intermittently injected from said plurality of peeling gas injection holes and forming a slewing gas flow within the inlet part;
• and
• at least one cooling medium injection nozzle provided in a side wall in an upper part of said gasification chamber near said outlet end for cooling the gas generated in said gasification chamber.