Fluidized bed coking with fuel gas production

Abstract

A Flexicoking™ unit which retains the capability of converting heavy oil feeds to lower boiling liquid hydrocarbon products while making a fuel gas from rejected coke to provide only a minimal coke yield. The heater section of the conventional three section unit (reactor, heater, gasifier) is eliminated and the cold coke from the reactor is passed directly to the gasifier which is modified by the installation of separators to remove coke particles from the product gas which is taken out of the gasifier for ultization. Hot coke from the gasifier is passed directly to the coking zone of the reactor to supply heat to support the endothermic cracking reactions and supply seed nuclei for the formation of coke in the reactor. Coke is withdrawn from the gasifier to remove excess coke and to purge the system of metals and ash.

1 . A coking process for converting a heavy hydrocarbon feedstock to lower boiling products in a fluid coking process unit comprised of a fluid coking reactor and a gasifier, comprising:
 (i) introducing the heavy hydrocarbon feedstock into the coking zone of a fluid coking reactor containing a fluidized bed of solid particles maintained at coking temperatures to produce a vapor phase product including normally liquid hydrocarbons, while coke is deposited on the solid particles;   (ii) passing the solid particles, with coke deposited on them directly to the gasifier,   (iii) contacting the solid particles with coke deposited on them in the gasifier with steam and an oxygen-containing gas in an oxygen limited atmosphere at an elevated temperature to heat the solid particles and form a fuel gas product from the coke, comprising carbon monoxide and hydrogen,   (iv) recycling the heated solid particles directly from the gasifier to the coking zone to supply heat to the coking zone.   
     
     
         2 . A process according to  claim 1  in which the oxygen-containing gas comprises air or oxygen-enriched air. 
     
     
         3 . A fluid coking unit for converting a heavy hydrocarbon feedstock to lower boiling products and for producing a fuel gas product in a fluid coking process unit comprised of a fluid coking reactor section and a gasifier section, comprising:
 (i) a fluid coking reactor section with an inlet for a heavy hydrocarbon feedstock, an outlet for cracked hydrocarbon vapors at the top of the reactor, an inlet at the bottom of the reactor for a fluidizing gas, an inlet for heated solid particles and a solid particle outlet at the bottom of the reactor for solid particles with coke deposited on them,   (ii) a gasifier section with an inlet for steam and oxygen-containing gas at its bottom, a solid particle inlet for solid particles with coke deposited on them, an outlet for fuel gas at its top and a solid particle outlet for solid particles heated in the gasifier,   (iii) a transfer line for passing the solid particles with coke deposited on them from the reactor solid particle outlet directly to the solid particle inlet of the gasifier section,   (iv) a transfer line for passing the solid particles heated in the gasifier section from the solid particle outlet of the gasifier section to the solid particle inlet of the reactor section for recycling the heated solid particles from the gasifier section to the reactor section to supply heat to the coking zone of the reactor.   
     
     
         4 . A fluid coking unit according to  claim 3  in which the gasifier section includes a gasifier vessel having internal cyclones to separate solid particles heated in the gasifier from the fuel gas. 
     
     
         5 . A fluid coking unit according to  claim 3  in which the gasifier section includes a gasifier vessel in which the solid particles with coke deposited on them are contacted with the steam and oxygen-containing gas and internal cyclones for separating solid particles heated in the gasifier from the fuel gas. 
     
     
         6 . A fluid coking unit according to  claim 3  in which the gasifier section includes (i) a gasifier vessel in which the solid particles with coke deposited on them are contacted with the steam and oxygen-containing gas and (ii) a separator in which solid particles heated in the gasifier vessel are separated from the fuel gas. 
     
     
         7 . A fluid coking unit according to  claim 6  in which the separator vessel includes cyclones for separating solid particles heated in the gasifier vessel from the fuel gas. 
     
     
         8 . A fluid coking unit according to  claim 6  in which the separator vessel includes gas/solid filters for separating solid particles heated in the gasifier vessel from the fuel gas. 
     
     
         9 . A fluid coking unit according to  claim 8  in which the gas/solid filters for separating solid particles heated in the gasifier vessel from the fuel gas comprise porous ceramic filters, sintered metal filters or a combination thereof. 
     
     
         10 . A fluid coking unit according to  claim 3  in which the gasifier section includes a main gasifier vessel in which the solid particles from the reactor with coke deposited on them are contacted with the steam and oxygen-containing gas to form fuel gas and a separator vessel having (i) a gas inlet connected to the main gasifier vessel, (ii) cyclones for separating solid particles heated in the main gasifier vessel from the fuel gas and (iii) a solid particle return line connecting the separator vessel to the main gasifier vessel for returning separated solid particles to the main gasifier vessel. 
     
     
         11 . A fluid coking unit according to  claim 3  in which the gasifier section includes a main gasifier vessel in which the solid particles from the reactor with coke deposited on them are contacted with the steam and oxygen-containing gas to form fuel gas and a separator vessel having (i) a gas inlet connected to the main gasifier vessel, (ii) gas/solid filters for separating solid particles heated in the main gasifier vessel from the fuel gas and (iii) a solid particle return line connecting the separator vessel to the main gasifier vessel for returning separated solid particles to the main gasifier vessel.