A recently-arrived integrated 6 barrel per day (bbl/day) microchannel GTL (gas-to-liquids) demonstration plant, designed to test the feasibility of small-scale offshore GTL, will produce a raw FT (Fischer-Tropsch) liquid and wax which can be further processed to provide a range of products or integrated into a crude oil stream for conventional refining.
Small-scale GTL facilities based on the use of microchannel reactors and designed for use on offshore platforms have the potential to turn unwanted associated gas into an energy asset and halt wasteful flaring or expensive re-injection.
The skid-mounted plant was built as part of a joint demonstration and testing agreement (JDTA) between the microchannel reactor specialists Velocys, Inc., the US-based member of the UK-based Oxford Catalysts Group; offshore facility developers, MODEC; the global engineering firm Toyo Engineering; and Petrobras. (Earlier post.) The skid includes microchannel Fischer-Tropsch (FT) and steam methane reforming (SMR) reactors developed by Velocys, as well as all the auxiliary equipment required to convert methane to FT products.
The GTL process involves two operations: steam methane reforming (SMR), followed by Fischer-Tropsch (FT) synthesis. In SMR the methane gas is mixed with steam and passed over a catalyst to produce a syngas consisting of hydrogen (H2) and carbon monoxide (CO). The reaction is highly endothermic, so requires the input of heat. This can be generated by the combustion of the excess H2. In microchannel SMR reactors the heat-generating combustion and steam methane reforming processes take place in adjacent channels. The high heat transfer properties of the microchannels make the process very efficient.
These same heat transfer properties offer different advantages for the highly exothermic FT reaction. Microchannel FT reactors consist of reactor blocks containing thousands of thin process channels filled with FT catalyst, which are interleaved with water-filled coolant channels. As a result they are able to dissipate the heat produced by the FT reaction much more quickly than conventional systems, so more active FT catalysts can be used.
Microchannel reactors are compact reactors that have channels with diameters in the millimeter range. The small diameter channels dissipate heat more quickly than conventional reactors with larger channel diameters in the 2.5 – 10 cm (1 – 4 inch) range so more active catalysts can be used. Mass and heat transfer limitations reduce the efficiency of the large conventional high pressure reactors used for hydroprocessing. The use of microchannel processing will make it possible to greatly intensify chemical reactions to enable them to occur at rates 10 to 1000 times faster than in conventional systems.
The Oxford Catalysts Group has developed microchannel Fischer-Tropsch (FT) and steam methane reforming (SMR) reactors.
Although the Oxford Catalysts Group’s FT microchannel reactors already have been proven in biomass to liquids (BTL) trials taking place at the biomass gasification facility in Güssing, Austria, the trial in Brazil will provide the first proving ground for the SMR reactor. It also represents the first time FT and SMR microchannel reactors have been combined on a single skid. This technology advance demonstrates the potential for the use of small scale microchannel GTL plants to handle and profit from small volumes of gas which would otherwise be flared.—Andrew Holwell, Business Development Manager at Oxford Catalysts
Following re-assembly, pre-commissioning and commissioning at the Fortaleza site, the demonstration plant is scheduled to start up in September, subject to the availability of the required utilities from Petrobras. It then will operate for approximately nine months.
Offshore GTL. According the Global Gas Flaring Reduction Initiative (GGFR), a World Bank-led public-private partnership launched in 2002, more than 134 billion cubic meters (bcm; or 4.7 trillion cubic feet) of natural gas are being flared and perhaps the same amount is vented annually. This is equivalent to 25% of the United States’ gas consumption, 30% of the European Union’s gas consumption, and more than the combined gas consumption of Central and South America.
A newly released GE study on the topic also estimates that 5% of the world’s natural gas production is wasted by burning or “flaring” unused gas each year, despite some progress on the flaring issue. (Earlier post.)
Offshore GTL facilities offer the potential to make use of this abundant potential energy source. The combination of small size, and high heat and mass transfer properties leading to high production efficiency make microchannel reactors ideal for use in offshore GTL.
Offshore GTL is an optimal approach for handling associated gas because the resulting product is a synthetic crude which can be combined with the petroleum crude so that it transported along with the oil to shore via existing tankers, eliminating the need for a separate logistics system to transport the gas to market.