A system for producing ethanol and methane / methanol

Abstract

A system comprises an anaerobic digester 110 configured to process carbohydrate to produce carbon dioxide gas 112 and a digestate 114, wherein the digestate comprises a mixture of ethanol and water; a

Claims

1. A system comprising:an anaerobic digester configured to process carbohydrate to produce carbon dioxide gas and a digestate, wherein the digestate comprises a mixture of ethanol and water;a separator configured to separate the mixture of ethanol and water from the digestate;a distillation apparatus configured to distil and separate the ethanol and the water;an electrolyser configured to electrolyse the distilled water in order to produce hydrogen and oxygen; anda reactor configured to convert the carbon dioxide gas and hydrogen to produce methane or methanol.

2. The system of any preceding claim, wherein the system comprises a furnace configured to burn solids in order to produce carbon dioxide gas, wherein the reactor is arranged to receive the carbon dioxide gas produced by the furnace.

3. The system of claim 2, wherein a solid residue is formed when the mixture of ethanol and water is removed from the digestate, and wherein the furnace is arranged to receive and burn the solid residue to produce the carbon dioxide gas.

4. The system of any one of claims 2 or 3, wherein the carbohydrate is derived from feedstock which comprises husk, and wherein the furnace is arranged to receive and burn the husk of the feedstock in order to produce the carbon dioxide gas.

5. The system of any one of claims 2 to 4, wherein the furnace is arranged to receive the oxygen produced by the electrolyser in order to form an oxygen-rich atmosphere in the furnace.

6. The system of any one of claims 2 to 5, wherein the furnace is further configured to produce steam, and wherein the distillation apparatus is arranged to receive the steam produced by the furnace.

7. The system of any one of claims 2 to 6, wherein the system comprises a dryer configured to remove water vapour from the carbon dioxide gas produced by the furnace.

8. The system of any preceding claim, wherein the system comprises an extractor configured to form an aqueous solution of carbohydrate at least partially from feedstock and distilled water produced by distillation apparatus, and arranged to provide the aqueous solution of carbohydrate to the anaerobic digester.

9. The system of any preceding claim, wherein the separator is a centrifuge.

10. The system of any preceding claim, wherein the reactor is a hydrogenator.

11. The system of any preceding claim, wherein the distillation apparatus comprises a heat pump.

12. The system of any preceding claim, wherein the system comprises a boiler arranged to produce steam using heat generated by the reactor, and wherein the distillation apparatus is arranged to receive the steam produced by the boiler.

13. The system of any preceding claim, wherein, when the reactor is configured to convert the carbon dioxide gas and hydrogen to produce methane, the system comprises one or more condensers configured to remove water vapour from the methane produced by the reactor.

14. The system of claim 13 when dependent on claim 8, wherein the one or more condensers are configured to condense the removed water vapour, and the extractor is configured to form aqueous solution of carbohydrate at least partially using condensed water vapour received from the condenser.

15. The system of any one of claims 1 to 12, wherein, when the reactor is configured to convert the carbon dioxide gas and hydrogen to produce methanol, the systemcomprises one or more distillation columns configured to remove water vapour from the methanol produced by the reactor.

16. A method comprising:fermenting carbohydrate in order to produce carbon dioxide gas and a digestate, wherein the digestate comprises a mixture of ethanol and water;separating the mixture of ethanol and water from the digestate;distilling and separating the ethanol and the water;electrolysing the distilled water in order to produce hydrogen and oxygen; and converting the carbon dioxide gas and the hydrogen to produce methane or methanol.

17. The method of claim 16, wherein the method comprises:prior to fermenting, forming an aqueous solution of carbohydrate at least partially from feedstock and from distilled water produced by distillation apparatus, wherein fermenting the carbohydrate comprises fermenting the aqueous solution of carbohydrate.

18. The method of any one of claims 16 or 17, wherein the method comprises:burning solids to produce carbon dioxide gas; andconverting the carbon dioxide gas produced from burning solids and the hydrogen to produce methane or methanol.

19. The method of claim 18, wherein the method comprises:combining the carbon dioxide gas produced from burning solids with the carbon dioxide gas produced from fermenting carbohydrate, prior to converting the carbon dioxide gas and the hydrogen to produce methane or methanol.

20. The method of claim 18 or 19, wherein the solids comprise at least one of a solid residue formed when the mixture of ethanol and water is separated from the digestate, and / or husk from a feedstock.

21. The method of any one of claims 18 to 20, wherein the solids are burned in an oxygen-rich atmosphere that at least partially comprises oxygen produced from electrolysing distilled water.

22. The method of any one of claims 18 to 21, wherein the method comprises: removing water vapour from the carbon dioxide gas produced from burning solids.

23. The method of any one of claims 16 to 22, wherein the method comprises: generating heat when converting the carbon dioxide gas and the hydrogen to produce methane or methanol;producing steam from the heat; andproviding the steam for distilling and separating ethanol and water.

24. The method of any one of claims 16 to 23, wherein the method comprises: removing water vapour from the methane or methanol produced by convertingthe carbon dioxide gas and the hydrogen.

25. The method of claim 24, wherein the method comprises:condensing the removed water vapour from the methane or methanol produced by converting the carbon dioxide gas and the hydrogen; andproviding the condensed water vapour to at least partially form aqueous solution of carbohydrate.

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