Processes for turning natural gas-to-liquid fuels have been around for about 200 years, but large-scale adoption of GTL technologies has languished, primarily because of relatively high investment costs in a market where prices tend to fluctuate from year to year. Interest, however, continues in GTL systems, especially with the exploration of shale-based gas reserves in the United States. Thus, its timely that a Scottish company, Gas2, which has been plugging away at developing lower-cost gas-reforming technologies, announced it is moving ahead with construction this year of a novel pilot reactor plant that it hopes will show that GTL production can be cost-competitive.
According to the company, the goal of Gas2’s new £5.5 million facility will be to demonstrate that it can convert “natural gas to liquid hydrocarbon more economically and cleanly than has previously been possible with conventional large scale GTL technologies. … The Gas2 approach is expected to result in considerably lower capital and operational expenditure and a smaller environmental footprint compared to conventional GTL technologies.”
“We are entering a new and exciting phase with the build of the pilot plant which will validate on a larger scale the commercial viability of the Gas2 process. We have a unique technology and process, and the commercial prize is great for a successful outcome,” says Mike Fleming, cofounder and managing director of Gas2.
It appears that the key component of the technology Fleming refers to is a catalytic ceramic based porous membrane that makes possible an alternative route than that being pursued by other developers of small to medium GTL.
Generally speaking, the GTL process requires two steps: first a feedstock gas is conversed into syngas, and then the syngas is converted into liquid hydrocarbon via the Fischer-Tropsch process. Although this sounds simple, each of these steps can have several complicated stages. For example, the production of syngas typically requires careful generation of steam and oxygen, which is mixed with the feedstock gas.
Gas2 says its catalytic ceramic membranes permit a simpler GTL design: The syngas and FT units are still separate, but the stages in each can be reduced. The company is understandably tight-lipped about the specifics of their membrane and system, but in the story “GTL just got smaller,” which appeared last year in The Chemical Engineer (pdf), Fleming and Gas2 engineer Ruben Rodriguez wrote about Gas2’s modular GTL technology uses a two-step process, each with only two stages. Their patented and trademarked porous membranes are used in both steps, first in a reactor to achieve catalytic partial oxidation of the feedstock gas into syngas, and then to transform the syngas to liquid fuels via a membrane running a low-temperature Fischer-Tropsch process.
In the story, they explain, “The technology is designed to work with oxygen-enriched air rather than pure oxygen, eliminating the need for air separation units. There is no need for steam during syngas generation and no compression between the syngas and FT units, reducing the amount of equipment and capital expenditure needed. Meanwhile, the Gas2 porous membrane reactors use asymmetric multi-channel membranes composed of a porous catalyst support and a filtering layer based on a mix of oxide materials such as titania and alumina. This gives the membranes greater thermal conductivity and an increased surface area for catalyst support which, coupled with a negligible pressure drop, results in improved heat and mass transfer. The mechanical strength of the porous membranes allows operability at pressures of up to 80 bar and temperatures as high as 1,000°C. The catalyst embedded in the membrane is rhodium for syngas generation, while a cobalt catalyst is used to produce liquid fuels in the Fischer-Tropsch reactor.”
Capacity-wise, they say they one barrel of liquid fuel can be produced from 10,000 cubic feet of natural gas (at standard conditions). Gas2 says it system also will work with stranded gasses, various gasses derived from shale deposits and offshore “associated” gasses (e.g., unwanted oilfield gasses that are often flared off), and that the FT process can create end products that include “gasoline, diesel, waxes, ammonia, methanol, hydrogen and ethylene for industrial use.”
Part of what Gas2 wants to demonstrate with the pilot plant is how a modular design can offer great flexibility at low cost. On its website, the company says, “The advantage of this modular design is that it can achieve large capacities (between 50–50,000 barrels per day) by adding more modular reactors.” The company says that its syngas and FT units can operate as stand-alone modules, too.
Gas2 says it will build and begin testing the plant this year, and then launch a commercialization phase in 2013. The company reports that monies for the pilot plant are coming from “existing shareholders, including Lime Rock Partners LLP, Robert Gordon University and a group of private investors with substantial interests in the oil, gas and hydrocarbons processing industries.”