Low inlet gas velocity high throughput biomass gasifier

A method of operating a gasifier which comprises:

• a. introducing inlet gas at a gas velocity of about 0.5 to 7 ft/sec to fluidize a bed in a gasifier vessel;
• b. forming the bed into a fluidized bed in a first space region by means of the inlet gas, the fluidized bed containing a circulating hot relatively fine and inert solid bed particle component;
• c. inputting and throughputting carbonaceous material into and through the first space region with fluidized bed at a rate from 500-4400 lbs/ft.sup.2 -hr;
• d. endothermally pyrolyzing the carbonaceous material by means of the circulating hot inert particle component so as to form a product gas;
• e. forming contiguous to and above the fluidized bed a lower average density entrained space region containing an entrained mixture of inert solid particles, char, and carbonaceous material and the product gas;
• f. gradually and continuously removing the entrained mixture and the product gas from the lower average density entrained space region of the gasifier to a separator, residence time of the carbonaceous material in the gasifier not exceeding 3 minutes on average;
• g. separating the entrained mixture from the product gas;
• h. passing the entrained mixture containing inert solid particles char, and carbonaceous material through an exothermic reaction zone to add heat;
• i. returning at least the inert solid particles to the first space region;
• and
• wherein the gasifier is operated at a pressure between atmospheric and 100 psia and wherein the inlet gas velocity in step (a) has an inverse relationship to the rate of inputting carbonaceous material in step (c).