June 4, 2003 — A new gasifier invention application has just been published at the U.S. Patent and Trademark Office (USPTO). This low-temperature (1600F) pressurized two-stage gasification process, PCPG (Pulverized Coal Pressurized Gasifier), has a unique level controlled ash bed which is porosity controlled to filter and hold un-reacted char to complete second stage gasification reactions prior to hot gas filtration using metalized candle filters.
Such hot gas candle filters remove 99.99 percent of particulates, equal to photographic clean room air in capability. A recent companion (see drawing above) patent application improves fuel distribution and burner design (Coanda Effect eddy generating means are included with the burner air swirl means to improve overall burner eddy effects) and locates both at the top of the gasifier for added simplicity and greater effectiveness.
According to inventor Lloyd Weaver, the advantages of this gasifier are its low-temperature operation (1600 degrees F) enabling sulfur to be reacted-out within the gasification process and insuring long gasifier life between shutdowns.
High-temperature designs (2700 degrees F) have short refractory life and require separate down-stream processes to react out sulfur.
The technology promises simpler and more reliable feed arrangement of dry pulverized fuel instead of pumping wet slurries through nozzles that wear out fast, not to mention the slurry pump wear problems.
PCPG is designed to operate air-blown for maximum cost effectiveness for large clean-coal power stations while still maintaining reliable low temperature operations for petrochemical operations requiring O2-blown gas. It features a unique ash quenching and dewatering screw auger to depressurize the ash, capture ash energy, and dry the ash for other uses.
Also, since pressurized gases reduce volumes about 20 times over normal boiler volumes, other pollution modules, when developed, are simpler to add since they are more compact and easier to insert into such processes.
The primary initial market intended for the gasifier is IGCC (Integrated Gasification Combined Cycle) power Stations that are gas turbine based, but petrochemical applications are not expected to lag far behind.
And because of the expected high hot gas efficacy of the gasifier (exceeding 97% with minimal carbon losses), overall power efficiency is expected to reach 50% with high reliability and low installed cost.
Since average global coal power efficiency is only about 25% according to World Coal Institute studies, such processes have the potential to halve coal use globally while greatly reducing air pollution simultaneously.
“Companies seeking solutions to the natural gas fuel crisis should be considering gasification technology to diversify their fuel mix,” Weaver said. “Only through fuel diversification and use of price-steady domestic fuels such as coal using clean, reliable, and fuel flexible gasification technologies can we take the pressure off natural gas supplies and bring the price of gas down.”
The patent can be viewed at http://www.uspto.gov/patft/index.html (in the Patent Application section under Publication Number Search, enter 20030089038). Additional information on PCPG is available at www.pcpg.us.