The Gasification Technology – Biomass & Waste
The PRME® Gasification Technology is fixed grate, up-draft, sub-stoichiometric and multi-zoned gasification system. PRME® Gasification Systems are available in a wide range of sizes to gasify from 20 – 2,000 tons per day.
Original Installation – The PRME® technology first employed in an “around the clock”, high demand, industrial application in 1982. The original units have since gasified over 1,250,000 tons of biomass fuel. Repairs on this system have been negligible. Later installations account for more than 700,000 tons of annual gasification capacity.
A complete PRME® Gasification System includes a fuel metering bin, solids infeed control; multi-zoned gasification air, the KC Reactor®, syngas cleaning process or staged combustion chamber, water cooled ash discharge conveyors, utility piping and instrumentation/electronic controls to provide automated operation. Then, depending on the customers’ needs, the syngas produced will be fully combusted for heat applications, partially combusted in a staged configuration for steam applications or cleaned and conditioned for other uses, such as electrical generation through I. C. engine gensets.
Fuel Metering Bin – Biomass fuels are metered to the reactor from the metering bin. This bin is equipped with an infeed leveling conveyor, level switches and a variable outfeed conveyor. The speed of the outfeed conveyor is automatically adjusted by the control system to maintain a predetermined temperature in the reactor.
Solids Infeed Control – Discharge from the metering bin is directed through a fuel metering device, providing precise, remote indication and control of feed rates. Metered biomass feed is transported into the reactor by a water-cooled screw conveyor, discharging into the lower portion of the reactor.
PRME© Reactor – The reactor is a vertical, cylindrical steel vessel that is lined with castable refractory. The proprietary shape of the reactor produces negligible entrained particulate matter and promotes mixing of volatilized combustibles. Residence time of the biomass fuels within the reactor can be precisely controlled.
Multi-zoned Gasification Air – Sub-stoichiometric air is admitted into the reactor via one or more zones and is controlled to volatilize the biomass while partially combusting the solids.
Staged Combustion – After the gasification process occurs in the reactor, hot evolved gas of low calorific value crosses into a staged air combustion zone. Staging combustion of the gases reduces the formation of incipient NOx.
Combustion Tube – As the evolved biomass gases are staged to complete oxidation, achieving desired temperature (typically 1600 to 2300F), they enter the combustion tube. The combustion tube is sized to assure adequate residence time at temperature and thorough mixing in the presence of excess oxygen to assure complete oxidation/destruction of all evolved combustibles.
Ash Discharge Conveyors – Ash exiting the reactor is discharged by a series of water-jacketed screw conveyors. The produced ash can be varied in composition to desired carbon content.
Utility Piping, Controls, Instrumentation – The typical scope of supply includes all utility piping (air and water) and all necessary controls to provide a complete operating system. This unique combination of equipment and process design produces a low pollutant content heat that may be used for steam generation, electrical power generation, drying applications, or safely diverted to the atmosphere. The entire process operates under induced draft, producing slightly negative pressure, eliminated fugitive emission of hot gases. Most biomass fuels do not require auxiliary fuel.
Biomass Fired Engine Generating Systems – The synthesis gases exiting the gasifier contain sufficient heating value to be used as a fuel for internal combustion engines, multi-fuel engines or gas turbines or to be converted into synthetic organic liquids. The synthesis gases from the reactor are, thermally treated to reform the gases, cooled and conditioned.
Control System – PRME® will provide a fully integrated, freestanding, PLC based logic control with functional operator interface stations, LCD screen, loop controllers and motor controls. Field instrumentation and protective devices will be provided to accommodate continuous control, monitoring, interlocking and alarming for the entire gasification system. This system will be capable of communicating with the balance of plant control system through a modular bus communication link. Should alternate hardware or software be desired, PRME® will incorporate the selected software into the process logic.