Staged furnaces for firing coal pyrolysis gas and char

A staged furnace assembly adapted for combustion of coal to produce hot flue gases for heating air and generating steam, the furnace assembly comprising:

• (a) a pyrolyzer reactor unit having inlet and outlet connections and adapted for reacting coal and air to produce a pyrolysis gas;
• (b) a first stage furnace having inlet and outlet connections and adapted for combusting the coal-derived pyrolysis gas to produce a primary combustion gas effluent;
• (c) two high temperature heat exchangers provided within the inlet portion of said first-stage furnace, one of said heat exchangers containing tubes utilizing heat resistant ceramic surfaces;
• and
• (d) a second stage furnace located adjacent to said first-stage furnace, and adapted for combusting char to produce a secondary combustion gas and mixing the secondary combustion gas with the primary combustion gas from the first-stage furnace, said second-stage furnace having an upper conduit connection for discharging the secondary combustion gas and two bottom conduit connections for coal feed and for ash withdrawal, respectively, said second-stage furnace containing within its upper portion a heat exchanger for preheating pressurized air and a heat exchanger for superheating steam, and including conduit connection means extending between said heat exchanger for preheating pressurized air and said high temperature heat exchanger within said first stage furnace.

A process for combusting coal utilizing two staged furnaces and generating power, the process comprising:

• (a) reacting coal feed with air in a pyrolyzer reactor, and producing a clean fuel gas and char;
• (b) combusting the clean fuel gas with additional air in a first stage furnace and producing a primary combustion gas, while heating a pressurized air stream in a high temperature heat exchanger therein;
• (c) feeding the primary combustion gas and the char to a second-stage furnace and burning the char and producing secondary combustion gas while quenching and reducing temperature of the resulting secondary combustion gas produced therein so as to thereby protect heat transfer surfaces and to preheat the pressurized air and superheat steam therein;
• (d) further heating the preheated pressurized air against said primary combustion gas and expanding the heated air in a gas turbine for generating shaft power;
• and
• (e) expanding the superheated steam in a steam turbine and producing additional shaft power.

A process for combusting coal utilizing two-staged furnaces and generating power, the process comprising:

• (a) reacting coal feed in a pyrolyzer reactor with air and a sorbent material and producing a raw fuel gas containing char, then separating the raw gas and char to provide a clean fuel gas;
• (b) combusting the clean fuel gas with additional air in a first-stage furnace and producing a primary combustion gas, while heating pressurized air in a high temperature heat exchanger therein;
• (c) feeding the primary combustion gas and the char to a second-stage furnace and burning the char and producing a secondary combustion gas while quenching and reducing temperature of the resulting secondary combustion gas produced therein so as to thereby protect heat transfer surfaces and to preheat the pressurized air and superheat steam therein;
• (d) feeding the char from said pyrolyzer reactor to said second-stage furnace along with additional air and coal as needed for burning of the char, and producing additional secondary combustion gases while preheating the pressurized air and superheating the steam therein;
• (e) further heating the preheated pressurized air against said primary combustion gas and expanding the heated air in a gas turbine for generating shaft power;
• (f) expanding the superheated steam in a steam turbine and producing additional shaft power;
• and
• (g) cooling the gas turbine and steam turbine exhaust streams and heating recycled steam condensate water to generate steam.