Fluidized bed biogasifier and method for gasifying biosolids

A method for gasifying biosolids obtained from sewage sludge, comprising:

• receiving biosolids in a biogasifier apparatus, the apparatus having:
• a fluidized bed biogasifier for gasifying biosolids to produce a producer gas;
• a staged-combustion thermal oxidizer for thermally oxidizing said producer gas;
• and
• a recycle flue gas loop connecting the staged-combustion thermal oxidizer to the fluidized bed biogasifier;
• wherein the fluidized bed gasifier comprises:
• a reactor vessel;
• a freeboard section having a diameter of at least 57 inches and a height of at least 10 feet;
• a feeder for feeding biosolids into said reactor vessel, said feeder being configured to feed said biosolids into said reactor vessel at a biosolids fuel feed rate during steady-state operation of the biogasifier;
• and
• a fluidized bed in a bed section of said reactor vessel, said fluidized bed having a diameter of at least 45 inches;
• wherein the freeboard section has a greater diameter than the fluidized bed;
• wherein the ratio of the freeboard section diameter to the fluidized bed diameter is at least 57:45;
• and further wherein the recycle flue gas loop is configured to recycle flue gas to the fluidized bed biogasifier;
• introducing gas to said fluidized bed reactor;
• and
• heating and reacting said biosolids inside said biogasifier, whereby biosolids are gasified.