Producing gaseous fuels of high calorific value
AssigneePetrocarbon Developments Limited
InventorJames Kevin Jones
Life of this patent
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Abstract
Process for upgrading an air-contaminated methane composition such as is found near coal measures comprises condensing this gas, and thereafter fractionating it to yield a first product having a methane content higher than that of the initial composition and a calorific value commensurate with that of natural gas, and a second product having a methane content below that of the initial composition but above the highest limit of the flammability range for methane-air mixtures under the conditions of temperature and pressure prevailing in the process.
Claims17
A process of upgrading a methane gas stream contaminated with a minor but significant quantity of air by fractionation at sub-ambient temperatures and superatmospheric pressures, said process comprising the steps of compressing said air-contaminated methane gas stream to elevated pressure, cooling the compressed gas to condense said gas, expanding the condensate to fractionation pressure and thereafter fractionating said expanded condensate to yield a liquid first product stream having a methane content higher than that of the initial composition and a calorific value commensurate with that of natural gas, and a gaseous second product stream having a methane content below that of the initial composition but above the highest limit of the flammability range of methane-air mixtures under the conditions of temperature and pressure prevailing in said fractionation, said elevated pressure being sufficiently high for substantially the whole of the refrigeration requirements of said cooling step to be provided from said subsequent expansion to fractionation pressure, and said cooling of the compressed gas being effected by indirect countercurrent heat exchange with first product and with evaporating second product.
Apparatus for upgrading an air-contaminated methane composition, said apparatus comprising in combination:
- a. first, second and third compression means each having a gas inlet and a gas outlet,
- b. gas-fuelled prime mover means for driving said first, second and third compression means,
- c. indirect countercurrent heat exchange means,
- d. expansion valve means,
- e. a fractionating column having an inlet, a liquid outlet below said inlet and a gas outlet above said inlet,
- f. a pump having an inlet and outlet,
- g. means for feeding said composition to the inlet of said first compression means,
- h. means for passing compressed composition from the outlet of said first compression means through said indirect countercurrent heat exchange means and then through said expansion valve means where it is expanded to a lower pressure and thence to the inlet of said fractionating column,
- i. means for separating a liquid product from the liquid outlet of said fractionating column into first and second portions, and means for recycling said first portion of said product through said heat exchange means in indirect countercurrent heat exchange with said compressed composition and back to the fractionating column,
- j. means for passing said second portion of the liquid product to the inlet of said pump,
- k. means for passing the liquid product from the outlet of said pump through said heat exchange means in indirect countercurrent heat exchange with said compressed composition and thence to the inlet of said second compression means,
- l. means for recovering a compressed fuel gas from the outlet of said second compression means, m) means for recoverng a gaseous product from the gas outlet of said fractionating column passing it through said m. exchange means in indirect countercurrent heat exchange with said compressed composition and thence to the inlet of said third compression means, and
- n. means for recovering a compressed lean fuel gas from the outlet of said third compression means and for feeding said gas as fuel to said prime mover means,
- said indirect countercurrent heat exchange means including first and second heat exchangers and in which said first heat exchanger contains first passage means for the passage therethrough of said compressed composition and second and third passage means for the passage therethrough respectively of said gaseous product and said second portion of said liquid product each in countercurrent to said compressed composition, and said second heat exchanger contains first passage means the inlet of which is connected to the outlet of said first passage means of said first heat exchanger for the passage therethrough of said compressed composition after it has traversed said first heat exchanger and second passage means for the passage therethrough of said first portion of said liquid product in countercurrent to said compressed composition.
Dependencies are inferred from the claim text.