April 2, 2002 — Coal as an energy source for electricity is presently inefficient and polluting, but it doesn’t have to be. It has 1/2 the overall global efficiency that is possible with proposed clean-coal IGCC (integrated gasification combined cycle) or new super-critical high temperature steam systems.
Ironically, solving the efficiency problem solves the pollution problem simultaneously. Once coal power is rebuilt globally to clean-coal standards (up to a $2 trillion proposition), twice the electricity is possible from the 3000 million tons coal consumed globally each year.
Averaging simple cycle natural gas-fired plants with combined cycle plants puts gas below what modern coal power can average in efficiency, according to the Lloyd Weaver, the inventor of a new coal gasification process.
Power producers in the U.S. may have built more gas turbine power plants than they can sustain with the gas resources currently available, which would necessitate the import of gas liquefied (LNG) in large ball shaped high-pressure tanks in ships.
However, coal gasification for power is presently in its infancy and may not progress with the technology DOE is sponsoring today, Weaver said. That’s because it commonly believed to be too expensive, unreliable, and too inefficient.
Gasifiers DOE sponsors require an oxygen plant to operate. While some Japanese researchers are developing a primarily air blown technology, theirs too requires some oxygen and both are high temperature process that shorten the life of the gasifier, Weaver said.
The strictly air-blown proposed PCPG (pulverized coal pressurized gasifier), Weaver’s invention, is a relatively simple machine. It operates at almost 1000 F degrees lower temperature (but at a more typical gasification temperature) than DOE’s or Japanese research units, Weaver said.
While the PCPG gasifier is slightly larger, it is designed to last longer, enhance sulfur-reducing reactions within the gasifier, and significantly lower the plant cost, and increase reliability.
“My new air-blown entrained-flow gasifier invention called PCPG (pulverized coal pressurized gasifier) will be so efficient and clean that it can eliminate the need for natural gas power plant systems saving valuable natural gas for other uses,” Weaver said.
“PCPG power plant efficiency can exceed 50% with the lowest capital, fuel and operational cost of any coal power system contemplated today.
“If PCPG power systems are properly designed, their emissions will be as competitive as it gets for coal using an air-blown gasifier that doesn’t have the added cost of an oxygen plant next door.”
On average, coal power plants around the world are only 25% efficient, half as efficient as they could be, he said.
“The simple idea that sets PCPG apart from all other gasifiers is it’s a simple air-blown technology that passes the hot combustion gases from the pressurized combustion chamber through a level-controlled agitated hot ash bed to capture char turning it into useful gas. The final gas passes under the inner wall out to an empty annular space and up and out the side as a hot gas and after high efficiency filtration (99.99% efficient) is used in a modern gas turbine-steam turbine combined cycle power system to achieve 50% efficiency,” Weaver said.
Consultant group Pearl Street Inc. (www.pearlstreetinc.com), in an independent evaluation of the invention, said “There is some evidence to suggest that the air-fed entrained-flow process could be most favorable for smaller electricity generation applications. These analyses were based on air-fed entrained processes other than PCPG. However, assuming that PCPG is a significant enhancement of this generic process, then it seems logical that a niche could be developed for this application. This should be considered an important means of expanding the market for coal gasification.”
The gasifier is currently licensed to Pakistan, and another license has been offered to Russia. Weaver said he is offering licenses at a reduced rate in some cases to encourage use of the technology around the world.
Weaver was a founder and former principal in SeptiTech Inc. (www.septitech.com), a company pioneering new wastewater treatment technologies. He is a mechanical engineer.
For more information, e-mail Lloyd Weaver at email@example.com.