GB2453963A

GB2453963A - Manufacture of carbon-neutral fuel

Info

Publication number: GB2453963A
Application number: GB0720790A
Authority: GB
Inventors: David Leslie Mcneight
Original assignee: STRATOS FUELS Ltd
Current assignee: STRATOS FUELS Ltd
Priority date: 2007-10-23
Filing date: 2007-10-23
Publication date: 2009-04-29
Also published as: GB0720790D0

Abstract

Carbon-neutral hydrocarbon fuel is made by reacting hydrogen and carbon dioxide both derived from water, particularly sea water, using solar power or other non-fossil fuel produced power. The hydrogen and carbon dioxide may be taken out of solution from sea water by heating or electrolysis, or using a semi-permeable membrane arrangement. They can then react together to produce carbon monoxide which can then react with more hydrogen to produce hydrocarbons by the Fischer-Tropsch reaction. All these systems may be powered by a solar generator or other type of renewable power such as wave or tidal power.

Description

Manufacture of Fuel This invention relates to the manufacture of fuel and, in particular, to the synthesis of hydrocarbon fuels from carbon monoxide or carbon dioxide and hydrogen.

It has been proposed to synthesise hydrocarbon fuels, using non-fossil fuel-derived energy, such as solar energy, from carbon dioxide recovered from the atmosphere, where there is too much of it, and hydrogen split by electrolysis from water, perhaps sea water, which is, because of its salt content, an electrolyte. The recovery of carbon dioxide from the atmosphere may be carried out in a variety of ways, such as absorption in lime or cryogenically. With carbon dioxide levels at some 380 parts per million (ppm) a huge quantity of air has to be processed to recover sensible amounts of carbon dioxide.

Recovery of the carbon dioxide from the atmosphere means that the fuel produced thereby is carbon neutral -there is no net addition of carbon dioxide as a result of combustion of the fuel, It is proposed to reduce and eventually cease using fossil fuels in order to stabilise atmospheric carbon dioxide levels. Recovered carbon dioxide in excess of that require to synthesis fuels could be sequestered, if it was desired to reduce the level of carbon dioxide in the atmosphere.

Carbon dioxide is soluble in water -think of soda water. It is in fact dissolved in sea water to the extent of 90 cc (at NTP) per 100 ml of sea water. It has recently been suggested mat because of the concentration of carbon cnoxide in the atmosphere, sea water is now saturated with carbon dioxide -no more can dissolve. This would appear to mean that atmospheric carbon dioxide levels will increase faster, for a given emissions rate, hastening the day when the level is too high to sustain life as we know it, currently predicted to be within forty or fifty years' time.

The present invention provides a method for the production of hydrocarbon fuel that addresses this problem.

The invention comprises a method for making hydrocarbon fuel, comprising reacting a carbon oxide with hydrogen, both being derived from water.

The water may be sea water.

The carbon oxide may be carbon dioxide taken out of solution from the water.

The amounts of carbon dioxide and hydrogen in the synthesis need to be balanced. A given mass of sea water will yield, on electrolysis, about ten times as much hydrogen by weight as it will carbon dioxide, while the synthesis reaction needs about a tenth as much hydrogen as carbon dioxide. So about one hundred times as much water has to be processed to extract carbon dioxide as needs to electrolysed to make hydrogen.

However, this is a much smaller volume of water than the volume of air required to extract the same amount of carbon dioxide, and wou'd require a much smaller plant. 4 4

Extraction of carbon dioxide from sea water may be less costly than extraction from air, particularly in situations where the water does not have to be pumped, e.g. in an ocean current or in tidal waters, and may be effected for example by warming the water -the solubility of carbon dioxide decreases with increasing temperature -or using semi-permeable membranes to remove it by osmosis.

One embodiment of apparatus to make fuels and a method of so doing will now be described with reference to the accompanying drawings, in which the single Figure is a diagrammatic illustration.

The drawing illustrates apparatus for making hydrocarbon fuel from sea water.

The apparatus comprises a solar generator 11 or other source of electricity not driven by fossil fuel, and a reactorl2 for reacting carbon monoxide and hydrogen using the Fischer-Tropfsch reaction to produce hydrocarbon fuel.

Electrical power from the generator 11 is used to extract carbon dioxide from sea water in a water heater 13, in which the water temperature is raised to reduce the solubility of carbon dioxide, which comes out of solution and is collected and fed to a reactor 14 into which hydrogen is fed from an electrolyser 15 to which is fed water from the water heater 13. The hydrogen reacts with the carbon dioxide to form carbon monoxide, which is fed to the reactor 12 together with hydrogen from the electrolyser 15. The catalysed enclotnermic reactions in reactors I -ano ii are powerea from me generator i i. Oniy some of the water from the water heater 13 is fed to the electrolyser IS. Hot water is passed in heat exchange with incoming cold water, to conserve power.

Clearly, other sources of electrical power may be used, such, for example, as nuclear power, wind, wave or tidal power.

Instead of a water heater, a semi-permeable membrane arrangement may be used to separate the carbon dioxide from the water.

And instead of two reactors, to convert carbon dioxide to carbon monoxide and then to hydrocarbon fuel, a single reactor may, under appropriate conditions, combine these two steps.

While sea water is referred to herein, it will be realised that any water may be used that is electrically conductive, or rendered so by the addition of salts. And while electrolysis is clearly a familiar method for splitting water into hydrogen and oxygen, water may also be dissociated using high temperatures.

Claims

Claims: A method for making hydrocarbon fuel, comprising reacting carbon oxide with hydrogen, both being derived from water.
2 A method according to claim I, in whish the water comprises sea water
3 A method according to claim I or claim 2, in which the carbon oxide is taken out of solution from the water, as by heating.
4 A method according to claim I or claim 2, in which the carbon dioxide is removed in a semi-permeable membrane arrangement.
Apparatus for making hydrocarbon fuel comprising a source of electrical energy not driven by fossil fuel, a source for sea water containing carbon dioxide, carbon dioxide separator means separating carbon dioxide from the sea water, hydrogen producing means for producing hydrogen from sea water and reactor means converting the carbon monoxide and hydrogen into hydrocarbon fuel, said separator, hydrogen producing and reactor means being powered by electrical energy from said source thereof.
6 Apparatus according to claim 5, in which the source of electrical energy comprises a solar power arrangement.
7 Apsu acccrding tc thc 3ai ãàijcij ic..civs peak insolation on the order of 1000 megawatts.
8 Apparatus according to any one of claims 5 to 7, in which the source of electrical energy comprises a nuclear reactor.
9 Apparatus according to any one of claims 5 to 8, in which the source of electrical energy comprises a wave or tidal power plant.

Apparatus according to any one of claims 5 to 9, comprising an electrolyser producing hydrogen from sea water.

II Hydrocarbon fuel made by a method according to any one of claims I to 4 or by apparatus as claimed in any one of claims 5 to
10.