Process for producing a combustible product

Abstract

A process for producing combustible product from an organic or biomass feedstock, the process comprising: mixing the feedstock with an alkaline material to give an alkaline aqueous mixture; heating the mixture by ohmic heating to a temperature in the range of about 280° C. to about 320° C. and reacting the mixture under subcritical conditions at the said temperature range and a pressure of about 6.6 to about 11.6 MPa (65 bar gauge to about 115 bar gauge); and removing at least some of the water to leave a combustible product, which may be used to form an aqueous slurry, suspension or emulsion and combusted in a suitable engine.

1 . A process for producing a combustible product from an organic or biomass feedstock, the process comprising:
 mixing the feedstock with an alkaline material to give an alkaline aqueous mixture;   heating the mixture by ohmic heating to a temperature in the range of about 280° C. to about 320° C. and reacting the mixture under subcritical conditions at the said temperature range and a pressure of about 6.6 to about 11.6 MPa (65 bar gauge to about 115 bar gauge); and   removing at least some of the water to leave a combustible product.   
     
     
         2 . The process as specified in  claim 1 , wherein the weight ratio of solid:liquid in the mixture is in the range about 1:2 to about 1:25, preferably about 1:3 to about 1:7, particularly preferably about 1:3 to about 1:5. 
     
     
         3 . The process as specified in  claim 1 , wherein the reaction under subcritical conditions is carried out over a period of at least about 1 minute, preferably at least about 2 minutes, particularly preferably at least about 5 minutes; and at most about 60 minutes, preferably at most about 30 minutes. 
     
     
         4 . The process as specified in  claim 1 , wherein the alkaline material is added in an amount about from 0.1 to 10% (calculated on 100% base content), preferably about 1 to about 5% w/w. 
     
     
         5 . The process as specified in  claim 1 , wherein the feedstock is an organic feedstock selected from one or more of: sewage material, sewage sludge, digested sewage sludge, digested human sewage sludge, digested dewatered sewage sludge cake, farm slurry, livestock slurry, pig slurry, cow slurry, compost, plant material, food production wastes, food production slurry, anaerobic digestate. 
     
     
         6 . The process as specified in  claim 1 , wherein the feedstock is a biomass feedstock selected from one or more of: wood chippings, wood fines, saw dust, waste wood, waste treatment wastes, bio crops, plant matter. 
     
     
         7 . The process as specified in  claim 1 , wherein the alkaline material is selected from: sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium formate, potassium formate, calcium hydroxide. 
     
     
         8 . The process as specified in  claim 1 , wherein the reaction is carried out at a pressure in the range of about 8.1 to about 11.1 MPa (80 to about 110 bar gauge), preferably about 9.1 to about 10.6 MPa (90 to about 105 bar gauge). 
     
     
         9 . The process as specified in  claim 1 , carried out in a tubular reactor or a plug flow reactor. 
     
     
         10 . The process as specified in  claim 1 , the process further comprising the step of combusting at least some of the combustible product. 
     
     
         11 . The process as specified in  claim 1 , further comprising milling the combustible product to produce fine particles, preferably of size less than about 10 μm, and mixing the particles with water, optionally with a surfactant and/or a stabiliser, to produce an aqueous suspension suitable for use as a liquid fuel. 
     
     
         12 . The process as specified in  claim 1 , further comprising extracting a liquid hydrocarbon fraction from the combustible material, and mixing the extracted hydrocarbon fraction with water, optionally with a surfactant and/or a stabiliser, to produce an emulsion suitable for use as a liquid fuel. 
     
     
         13 . The process as specified in  claim 1 , wherein the feedstock is waste wood fines. 
     
     
         14 . The process as specified in  claim 1 , wherein the feedstock is sewage sludge. 
     
     
         15 . The process as specified in  claim 13 , further comprising mixing the combustible product with water without milling the combustible product, optionally with a surfactant and/or a stabiliser, to produce an aqueous suspension suitable for use as a liquid fuel. 
     
     
         16 . A process for producing a liquid fuel from an organic or biomass feedstock, the process comprising:
 mixing the feedstock with an alkaline material to give an alkaline aqueous mixture;   heating the mixture by ohmic heating to a temperature in the range of about 280° C. to about 320° C. and reacting the mixture under subcritical conditions at the said temperature range and a pressure of about 6.6 to about 11.6 MPa (65 bar gauge to about 115 bar gauge);   removing at least some of the water to leave a combustible material;   extracting a liquid hydrocarbon fraction from the combustible material, and combining the extracted hydrocarbon fraction with water to produce an emulsion suitable for use as a liquid fuel.   
     
     
         17 . A process for producing a combustible product from an organic or biomass feedstock, the process comprising:
 mixing the feedstock with an alkaline material to give an alkaline aqueous mixture;   heating the mixture by ohmic heating to a temperature in the range of about 280° C. to about 320° C. and reacting the mixture under subcritical conditions at the said temperature range and a pressure of about 6.6 to about 11.6 MPa (65 bar gauge to about 115 bar gauge);   removing at least some of the water to leave a solid combustible material;   milling the solid combustible material to produce particles of size less than about 10 μm; and   mixing the particles with water and a surfactant to produce an aqueous suspension suitable for use as a liquid fuel.