Flaring associated gas is common practice in oil field operation. The main purpose of flaring gas through flaring system is to convert ignited gas to unignited gas (CO, CO2, H2O). By doing so, the operator prevents uncontrolled fire.
Thousand cubic feet of gas are burn everyday. The burning produces CO and CO2 as major air pollutant into atmosphere. Oil field operators opt burning gas because of difficulties in utilizing the gas and no limitation yet to burn gas.
Nowadays, global warming and expensive fossil fuel issues are rising. People are pushed harder to reduce air pollution and utilize fossil fuel as effectively as possible. The idea is to convert flare gas to liquid (GTL) and produce hydrocarbon oil or liquid only, no more natural gas flaring and wasting unutilized fossil fuel in oil field operation.
Converting waste gas to useful hydrocarbon has been started since a long time ago. The technology was founded by Franz Fischer and Hans Tropsch in the 1920s and became popular as FT synthesis. FT synthesis converts syngas (CO, H2) to synthetic fuel. It uses HPHT equipment and high power to convert CO back to hydrocarbon. Germany used the technology to fulfill its need in liquid hydrocarbon fuels during world war. There was no significant advancement in the technology since that.
Due to scarcely of hydrocarbon fuels, flare gas capture companies start using FT synthesis to convert waste gas to valuable hydrocarbon after more than 50 years since founded. HPHT equipment and high power requirements in FT synthesis bring the idea of finding alternative technology to convert waste gas. Some scientists still use some parts of FT synthesis and make better processes in preparing synthesis gas or syngas (steam-methane reforming, partial oxidation, autothermal reforming, gas heated reforming). Others do not use FT synthesis at all.
The following patents convert hydrocarbon gas to hydrocarbon liquid by using the high shear device and chemical reaction. Both technologies can be used by oil field companies or flare gas capture companies who want to produce hydrocarbon liquid only. For economic valuation, they can contact CompactGTL, headquartered in the UK, which can construct GTL facilities as required such as mobile skid facilities.
System and process for production of liquid product from light gas
TThe process mechanically broke source gas to smaller molecules or radical molecules. The molecules disperse in a liquid medium such as water in the form of bubbles. To achieve very small bubbles (0.1 to .5 micron m), a high shear device (HSD) and catalyst are required (Figure 1). The HSD can generate 20000/s of shear rate. The shear rate and catalyst (ruthenium) can be chosen selectively to make certain products. Multi-stage HSD can be used for a high production rate.
The product from HSD is stable for 15 minutes and flowing into the reactor for recombination. The reactor will recombine radical molecules to produce liquid hydrocarbon. Produced hydrocarbon liquid will flow to the storage tank and the remaining gas is trapped in the condenser and flowed back to HSD. Some produced hydrocarbon liquid (fuel) can be used to run the pieces of equipment (HSD, reactor, pumps, and condenser).
Process for converting gaseous alkanes to olefins and liquid hydrocarbons
The process in this patent converts hydrocarbon gas to hydrocarbon liquid chemically. Bromine can break hydrocarbon gas at lower temperatures compared to other methods such as steam-methane reforming which requires temperature more than 600 degrees Celcius. This process can be used with less expensive equipment and more efficient energy.
Gas feed will be mixed with dry bromine vapor in a reactor at a temperature between 250 and 600 degrees Celcius (Figure 2). The reaction will produce alkyl bromide and hydrobromic acid vapor. The products will flow to the second reactor for catalytic reaction (zeolite as a catalyst) to produce hydrocarbon liquid. A scrubber is used to clean-up hydrocarbon liquid. Excess of hydrobromic vapor will flow to reconditioning facilities for treatment to recover dry bromine vapor.
Recommended readings, hydrobromic acid, natural gas to liquid propane convertor, and oilfield pump model: