Gasification in Detail – Types of Gasifiers – Fluidized Bed Gasifiers
Great Point Energy
GreatPoint Energy, founded in 2005, is commercializing a fluidized-bed, catalytic gasification process, called Bluegas™, to covert coal and other carbonaceous materials to synthetic natural gas (SNG). In contrast to conventional coal-to-SNG process (e.g., the Great Plains Synfuels Plant), which is based on non-catalytic coal gasification to first generate a syngas, then followed by water-gas-shift (WGS) and methanation reaction to produce methane, catalytic gasification offers the opportunity to combine these processes into a single step with improved thermal efficiency.
Catalytic gasification to SNG has been subjected to an extensive developmental effort by Exxon in the late 1970s to the early 1980s with funding support from the U.S. Department of Energy (DOE). With the natural gas price collapsed in the mid 1980s, continued developmental efforts stopped. The original Exxon patents on the process have expired. GreatPoint Energy has expanded on Exxon’s developments in its current technology commercialization development program.
GreatPoint Bluegas™ Process
Figure 1 shows an overview of the GreatPoint Energy’s Bluegas™ catalytic gasification SNG process. Partially dried coal and/or other carbonaceous feed (GreatPoint is marketing the technology for biomass and petcoke application as well) is mixed/catalyzed with a proprietary catalyst solution. The catalyzed coal is then dried and transported to a fluidized-bed gasifier via a lock hopper system. Steam is also added. In the gasifer, the catalyst promotes the hydrogasification/WGS/methanation reactions to produce methane and carbon dioxide (CO2). The syngas leaving the catalytic gasifier undergoes a series of cleanup steps to remove particulates, water and acid gases followed by a separation step to recover the methane product gas. The syngas from the gasifier is not expected to contain tar, heavy oil byproducts, or volatile organic compounds (VOCs), and CO2 can be captured and sequestrated.
The char withdrawn from the gasifier is processed in the catalyst recovery unit, in which the catalyst is recovered and recycled to the process. Fresh makeup catalyst solution is used to supplement catalyst losses.
Figure 1: Overview of GreatPoint Energy Bluegas™ Process
Great Point Energy)
Demonstration and Early Commercialization
GreatPoint Energy’s process demonstration of their Bluegas™ technology was initially conducted at the Gas Technology Institute’s (GTI) Flex-Fuel Test Facility, from 2006 to the end of 2007, using GTI’s existing fluidized-bed U-GAS gasifier of 1 ton per day (tpd) capacity. The demonstration program focused primarily on gasification testing of the process and did not include testing of other supporting processes such as gas cleanup, catalyst recovery, and/or gas recycling. Catalyst system development and recovery were carried out in a bench-scale laboratory at a different location. During this demonstration period, GreatPoint Energy operated the U-GAS gasifier (14-inch diameter and 60-foot high) at 1,200 to 1,300° F and at approximately 500 psia, and conducted test runs using sub-bituminous Powder River Basin (PRB) coal and petcoke.
GreatPoint has recently completed construction of a new, 1-tpd demonstration plant located at Dominion’s Brayton Point power plant in Massachusetts. This demonstration plant has facilities for coal grinding, catalyst addition, and gasification. Operation of the demonstration plant began in March of 2009. GreatPoint Energy is currently testing coal feedstock and has plan to test petcoke and biomass.
As the next stage of commercial development, GreatPoint Energy intends to accelerate its development from the 1-tpd demonstration facility to a 1,500-tpd commercial-scale plant. A $1.25 billion partnership was created recently between GreatPoint Energy and industrial conglomerate China Wanxiang Holding to build a large scale plant to produce .5% of China's projected energy needs. The first phase is expected to begin operation in 2015 with an initial natural gas production of 30 billion cubic feet.1