Process the Generation of Gaseous Fuels

Abstract

A process and system for the generation gaseous fuels, the process comprising gasifying a carbonaceous fuel with vitiated air in the presence of lime and water to provide calcium carbonate, a gaseous fuel and heat; the system comprising a reactor for the gasification of the carbonaceous fuel with vitiated air in the presence of lime and water, and a heat exchanger to extract heat from the gaseous fuel. Use in the generation of gaseous fuels, in energy distribution and in grid energy firming.

Claims

1. A process for the generation gaseous fuels, the process comprising gasifying a carbonaceous fuel with vitiated air in the presence of a metal oxide and water to provide a metal carbonate, a gaseous fuel and heat, wherein the overall process is represented by the following reaction:
C.sub.aH.sub.bO.sub.c+aMO+N.sub.2+H.sub.2O.fwdarw.N.sub.2+C.sub.xH.sub.y+(a-x)MCO.sub.3 wherein a, b and c are the molar component of the carbonaceous fuel, x may very from 0 to 8 and y may very from 2 to 14, MO represent metal oxide and MCO.sub.3 represent metal carbonate.

2. A process according to claim 1, comprising: a) gasification of the carbonaceous fuel to produce carbon monoxide and hydrogen; b) reaction of carbon monoxide with water to produce carbon dioxide and hydrogen; and c) recarbonation of the metal oxide by carbon dioxide to produce a metal carbonate.

3. A process according to claim 1, wherein the metal oxide is selected from calcium oxide and/or magnesium oxide, and the metal carbonate is calcium carbonate and/or magnesium carbonate.

4. A process according to claim 1, wherein the carbonaceous fuel comprises a solid fuel.

5. A process according to claim 1, wherein the carbonaceous fuel is selected from coal, coke, lignite, biomass, one or more hydrocarbons, or a combination thereof.

6. A process according to claim 1, wherein the gaseous fuel is selected from syngas or hydrogen.

7. A process according to claim 1, wherein the gaseous fuel is a low or zero carbon fuel.

8. A process according to claim 1, wherein the vitiated air comprises in the range 1-15 mol % oxygen.

9. A process according to claim 1, wherein the process occurs in a single reactor.

10. A process according to claim 9, wherein the reactor is a bed reactor.

11. (canceled)

12. A process according to claim 1, wherein the gaseous fuel is combusted to provide heat energy.

13. A gaseous fuel generation system for a process of claim 1, the system comprising a reactor for the gasification of the carbonaceous fuel with vitiated air in the presence of lime and water, and a heat exchanger to extract heat from the gaseous fuel.

14. A system according to claim 13, further comprising a separator for the gaseous fuel.

15. A use of a process or system according to claim 1, in the generation of gaseous fuels.

16. A use according to claim 15, in energy distribution.

17. A use according to claim 16, wherein the energy is distributed by transport of the gaseous fuel to the point of use.

18. A use according to claim 16, wherein the energy is distributed by the combustion of the gaseous fuel to provide heat energy which is converted into electrical energy.

19. A use according to claim 15, in grid energy firming.

Description

[0055] In order that the invention may be more readily understood, it will be described further with reference to the figures hereinafter.

[0056] FIG. 1 is a schematic representation of a process and system of the invention comprising a single reactor together with separation of the gaseous fuels;

[0057] FIG. 2 is a schematic representation of a process and system of the invention comprising multiple reactors; and

[0058] FIG. 3 is a schematic representation of a process and system of the invention comprising a single reactor, together with subsequent combustion of the gaseous fuel to generate heat.

[0059] FIG. 1 shows one implementation of the process and system of the invention. The system comprises fluidised bed reactor 5, comprising the carbonaceous fuel (for instance wet biomass) and lime. To this is added vitiated air. The solid reaction products, primarily ash and calcium carbonate are removed from the reactor and distributed on land to improve soil quality. The hot gaseous fuel, such as syngas (here carbon monoxide and hydrogen as carbon dioxide has been removed) produced passes from the reactor to a heat exchanger 10 where it is cooled. In this example, the cooled syngas is then separated in gas separator 20, to provide pure carbon monoxide and hydrogen. The heat in this process is converted to electricity in turbine 15.

[0060] FIG. 2 shows an alternative implementation of the process and system of the invention. The system of FIG. 2 comprises a fixed bed gaseous fuel generation reactor 25, however, in this implementation, the gaseous fuel generation reactor 25 does not facilitate recarbonation. Recarbonation occurs in fluidised bed recarbonation reactor 30.

[0061] As such, the hot gaseous fuel released from reactor 25 in this example includes carbon dioxide. By way of specific illustration, the carbonaceous fuel, for instance coke, is reacted with vitiated air and water in reactor 25. The gaseous fuel released from reactor 25 comprises, for instance, syngas—hydrogen, carbon monoxide—and carbon dioxide. The fuel is transferred to recarbonation reactor 30, where it is passed over lime which absorbs the carbon dioxide. After recarbonation in reactor 30, all gases are passed to heat exchanger 10, and cooled, the heat being used to generate electricity via turbine 15 and the cooled gaseous fuel is stored. In this example, the separate production of ash from reactor 25, and calcium carbonate from reactor 30 provides for the easy use of calcium carbonate as a commodity product if desired, whilst the ash may be spread on the land as before.

[0062] FIG. 3 shows a further implementation of the process and system of the invention. The system of FIG. 3 is similar to the system of FIG. 1 and comprises, a fluidised bed reactor 5, together with a heat exchanger 10, passing heat into turbine 15, and a combustion chamber 35. In this implementation, reactor 5 comprises carbonaceous fuel (in this case lignite), vitiated air, water (often provided as moist vitiated air) and a combination of lime and magnesium oxide. The solid reaction products, namely ash and calcium/magnesium carbonate are removed from reactor 5 and distributed on land. The hot gaseous fuel (in this example hydrogen) is passed to heat exchanger 10, where it is cooled. In this example, the cold fuel is then burnt in combustion chamber 35 to generate hot flue gas which can be cooled using heat exchanger 10 to generate more electricity.

[0063] In each of the above processes a conventional reforming step may also be introduced to remove hydrocarbon by-products, this step is not illustrated here.

[0064] It would be appreciated that the process and system of the invention are capable of being implemented in a variety of ways, only a few of which have been illustrated and described above.