Direct fired heater utilizing particulates as a heat transfer medium

A direct fired process fluid heater wherein the process fluid is a liquid, and wherein heat resistant particulates are used as a heat transfer medium;

• a dispersion device located at the top of the heater, the dispersion device consisting of an externally insulated outer pipe carrying pressurized steam and an inner pipe carrying a stream of particulates pressurized by a rotary helical conveyor;
• one or more openings along the length of the inner pipe admitting a downward jet of steam to contact the particulates, steam jets passing through the particulate mass, and carrying with it a stream of particulates, the particulates exiting through a shrouded opening in the outer pipe;
• the arrangement allowing for the formation of jets with a concentration of particulates at the outer surfaces of the jets, resulting in a cavity enveloped by the jet surfaces, the jet cavity having a base equal in diameter to the inside diameter of the heater enclosure;
• permitting passage of a controlled flow of hot combustion products between inner and outer particulate containing surfaces of the jets;
• use being made of an induced draft fan with control damper, located at the convection section combustion product outlet, allowing for controlled transfer of incoming combustion products from inner to outer surfaces of the jets, so as to control jet configuration and providing for maximum utilization of particulate surface area;
• spacing and orientation of the steam-particulate openings to be such that contact between the down-flowing particulates and the up-flowing stream of heated combustion products, generated by horizontal, bottom, opposed, side wall burners, is obtained;
• combustion product exits the burners, the combustion end of the latter extending beyond the inside wall of the heater enclosure, so that the upward flow of combustion products generated by the opposed side wall burners are directed inside the base of the cavity formed by the particulate laden surfaces of the jet;
• burners to be fired with gas, liquid or other types of fuel and located at the bottom of a first vertical cylindrical, water jacketed, internally insulated particulate—combustion product containment vessel, with sloping sides, dis-engagement between combustion product and particulates occurring at the bottom of said first containment vessel, the particulates then flowing thru a particulate standpipe;
• particulate free combustion product exiting at the top of said first containment vessel 1, and passing downward thru a horizontal tube convection section, the exiting combustion product processed further in a down stream quench tower;
• incoming process feed, pressurized by a pump, flowing past the inside surfaces of the convection section tube array, recovering heat in the process and lowering the temperature of the combustion product gas flowing across the outer tube surfaces of the tube array;
• preheated process feed exiting the convection section tube array, conveyed by a transfer line to the exit nozzle of the particulate standpipe and mixing with and conveying the high temperature particulates to a second, internally insulated, vertical containment vessel, wherein preheated process fluid is raised to design outlet temperature by contact with the high temperature particulate stream;
• the up-flowing particulate and process feed stream disengaging in a reduced velocity settling section of said second containment vessel, the settling section consisting of a diametrically enlarged upper section of vessel said second containment vessel;
• the high temperature liquid process stream at design temperature being further processed in downstream equipment, the particulate stream being withdrawn thru a vertical transfer line from the bottom of the settling section and entering said rotary helical conveyor which pressurizes the particulate stream, allowing particulates to be conveyed thru the dispersion device of said first containment vessel;
• the combustion product streams entering the inlet of the convection section and exiting thru an outlet nozzle and transfer line and routed to a quench tower for process fluid recovery in a quench tower.