Flare gas limiting apparaus for coal gasification unit

A gas flare pollution reducing device comprising:

• a coal pressure gasification unit having inlet means and exhaust means, said inlet means for introducing gasification agents into said gasification unit, said exhaust means for emitting product gas formed by combining gasification agents and coal in said gasification unit;
• pressure reducing means, connected to said inlet means of the pressure gasification unit, for reducing the pressure of gasification agents into said gasification unit after an interruption in the operation of said gasification unit;
• a start-up flare regulating valve having an upstream port and a downstream port, said upstream port connected to said exhaust means of said gasification unit;
• a main flare regulating valve having an upstream port and a downstream port, said upstream port connected to said exhaust means of said gasification unit;
• a start-up flare connected to said downstream port of said start-up flare regulating valve for burning product gas from said gasification unit;
• orifice means, connected to said downstream port of said start-up flare regulating valve and to said downstream port of said main flare regulating valve, for limiting the flow of product gas therethrough;
• a main gas flare connected to said orifice means for burning product gas from said gasification unit;
• a first predetermined minimum response pressure, connected to said start-up flare regulating valve at said upstream port, for actuating said start-up flare regulating valve after an interruption in the operation of said gasification unit and when an excess quantity of product gas is formed in said gasification unit, said first predetermined minimum response pressure further being determined by the critical pressure ratio for the product gas across said start-up flare regulating valve;
• and
• a second predetermined minimum response pressure connected to said main flare regulating valve at said upstream port for actuating said main flare regulating valve after an interruption in the operation of said gasification unit and when an excess quantity of product gas is formed in said gasification unit, said second predetermined minimum response pressure further being determined by at least 90 percent of the critical pressure ratio for the product gas across said main flare regulating valve, whereby when said start-up flare regulating valve and said main flare regulating valve are opened and said pressure reducing means are opened after an interruption in the operation of said gasification unit the product gas is permitted to flow from the gasification unit to said start-up gas flare and to said main gas flare to be burned therein thereby reducing environmental pollution.