NOVELTY - A solid biomass is contacted with a catalyst stream (c1) in a reaction zone (r1) and mixed to obtain a biomass-catalyst mixture (m1). A portion of solid biomass in biomass-catalyst mixture (m1) is converted to obtain a gaseous product stream (g1) and a biomass-catalyst mixture (m2). At least a portion of unconverted biomass in biomass-catalyst mixture (m2) is converted to obtain a gaseous product stream (g2) and a spent catalyst. The gaseous product stream (g1) and gaseous product stream (g2) are removed from reaction zone (r1) as a product mixture comprising hydrocarbons.    USE - Conversion of solid biomass to hydrocarbon. Uses include but are not limited to wood, straw, grass, bagasse and corn stover.    ADVANTAGE - The method enables conversion of solid biomass to hydrocarbon efficiently, with catalyst/feedstock contact time of millisecond range.    DETAILED DESCRIPTION - A solid biomass is contacted with a catalyst stream (c1) comprising a catalyst in a reaction zone (r1) at temperature (t1) of 250-400 degrees C. The solid biomass is mixed with catalyst stream (c1) to obtain a biomass-catalyst mixture (m1). A portion of solid biomass in biomass-catalyst mixture (m1) is converted to obtain a gaseous product stream (g1) comprising hydrocarbons and a biomass-catalyst mixture (m2) comprising catalyst stream (c1) and unconverted biomass. The biomass-catalyst mixture (m2) is downwardly-passed to a reaction zone (r2). A catalyst stream (c2) is charged to reaction zone (r2) for contact with biomass-catalyst mixture (m2), and the reaction zone is at temperature (t2). At least a portion of unconverted biomass in biomass-catalyst mixture (m2) is converted to obtain a gaseous product stream (g2) comprising hydrocarbons and a spent catalyst comprising coke. The spent catalyst is charged to a regenerator (20) in which coke is burned off from spent catalyst in presence of oxygen to obtain a regenerated catalyst. A portion of regenerated catalyst is charged to reaction zone (r1) as catalyst stream (c1), and a portion of regenerated catalyst is charged to reaction zone (r2) as catalyst stream (c2). The gaseous product stream (g2) is upwardly-passed to reaction zone (r1), and gaseous product stream (g1) and gaseous product stream (g2) are removed from reaction zone (r1) as a product mixture comprising hydrocarbons. An INDEPENDENT CLAIM is included for system, which has a pyrolysis reactor with reaction zone (r1) and reaction zone (r2) located spatially below the reaction zone (r1), regenerator which is in fluid flow communication by a conduit (i) to the top of pyrolysis reactor, which is in fluid flow communication by a conduit (ii) to the bottom of pyrolysis reactor and which is in fluid flow communication by a conduit (iii) to reaction zone (r2) and a conduit (iv) which is in fluid flow communication with reaction zone (r1) of pyrolysis reactor.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of the apparatus for converting solid biomass to hydrocarbon.    Conversion unit (1)    Stripper/reactor (10)    Regenerator (20)    Heat exchanger (21)    Fractionator (30)