System and method for generation of synthesis gas from subterranean coal deposits via thermal decomposition of water by an electric torch

Abstract

A system for gasification of coal deposits below the ground surface comprising an injection well assembly comprising one end positioned at the surface and the opposite end located adjacent or within the coal deposit; a production well assembly comprising one end positioned at the surface and the opposite end of the production well assembly located adjacent or within the coal deposit; a non-vertical reaction shaft assembly located adjacent or within the coal deposit, the non-vertical reaction comprising an injection end in communication with the end of the injection well assembly located adjacent or within the coal deposit and a production end in communication with the end of the production well assembly located adjacent or within the coal deposit; and an electric torch configured to move within the non-vertical reaction shaft assembly and create an oxidant and moderator downhole. A method for gasifying coal deposits is also provided.

1 . A system for the gasification of a coal deposit located below the ground surface, the system comprising:
 an injection well assembly comprising one end positioned proximate the ground surface and the opposite end of the injection well assembly located adjacent to or within the coal deposit;   a production well assembly comprising one end positioned proximate the ground surface and the opposite end of the production well assembly located adjacent to or within the coal deposit;   a non-vertical reaction shaft assembly located adjacent to or within the coal deposit a distance below the ground surface, the non-vertical reaction shaft having a length and comprising an injection end in communication with the end of the injection well assembly located adjacent to or within the coal deposit and a production end in communication with the end of the production well assembly located adjacent to or within the coal deposit; and   an electric torch configured to move within the non-vertical reaction shaft assembly and create an oxidant and moderator downhole.   
     
     
         2 . The system of  claim 1  wherein the coal deposit comprises at least one selected from the group consisting of peat, lignite, sub bituminous coal, bituminous coal, anthracite, and combinations thereof. 
     
     
         3 . The system of  claim 1  wherein the injection well assembly is within 15 degrees of vertical. 
     
     
         4 . The system of  claim 1  wherein the non-vertical reaction shaft assembly diverges from vertical by more than 15 degrees. 
     
     
         5 . The system of  claim 1  wherein the electric torch comprises a non-transferred arc plasma torch, and wherein the electric torch utilizes steam as the plasma gas. 
     
     
         6 . The system of  claim 1  wherein the electric torch comprises one or more directional jets which may be actively or passively vectored to shape a reaction cavity. 
     
     
         7 . The system of  claim 6  wherein the electric torch is operable to separate positively charged species from negatively charged species or is operable to separate oxidizers from reducers or both and wherein the electric torch is configured to expel separate jets thereof. 
     
     
         8 . The system of  claim 1  wherein the non-vertical reaction shaft is at least partially lined by a water-cooled, thermally-consumable casing material. 
     
     
         9 . The system of  claim 1  wherein the distance below ground surface is greater than about 3,000 feet (914.4 m). 
     
     
         10 . The system of  claim 1  wherein the only fluid inlet into the system is one or more inlets for liquid water or liquid carbon dioxide. 
     
     
         11 . The system of  claim 1  wherein the production well assembly further comprises a product casing, a steam jacket casing surrounding at least a portion of the product casing, and an external water jacket casing surrounding at least a portion of the steam jacket casing, wherein the external water jacket casing comprises an inlet for water and wherein the steam jacket casing comprises an outlet for steam and wherein the product casing transfers product gasification gas from the non-vertical reaction shaft assembly to the surface. 
     
     
         12 . The system of  claim 11  wherein at least one of the steam jacket casing and the product casing is capable of expanding independently and/or at different rates of thermal expansion as compared to the external water jacket casing. 
     
     
         13 . A method for gasifying a coal deposit located below the ground surface, the method comprising:
 positioning an electric torch comprising a discharge head within a non-vertical reaction shaft assembly, the non-vertical reaction shaft assembly having a length, an injection end, and a production end, and wherein the non-vertical reaction shaft assembly is positioned at least partially within the coal deposit a distance of at least 1,000 feet (304.8 m) below ground; and   internally creating, with the electric torch, an oxidant and a moderator from an externally-supplied liquid, whereby at least a portion of the coal deposit is gasified to create a reaction cavity, wherein the electric torch is operated at a temperature.   
     
     
         14 . The method of  claim 13  wherein the coal deposit comprises at least one selected from the group consisting of peat, lignite, sub bituminous coal, bituminous coal, anthracite, and combinations thereof. 
     
     
         15 . The method of  claim 13  wherein the electric torch is attached to one end of each of at least one retaining cables whereby each of the at least one retaining cables extends from the electric torch through an injection well to the ground surface; and wherein the production end of the non-vertical reaction shaft assembly is in communication with a below-ground end of a production well, and wherein the injection well comprises one end in communication with the ground surface and one end in communication with the injection end of the non-vertical reaction shaft assembly. 
     
     
         16 . The method of  claim 13  wherein the production well further comprises: a product casing adapted to transfer product gasification gas from the non-vertical reaction shaft assembly to the surface; a steam jacket casing surrounding at least a portion of the product casing, the steam jacket casing having an outlet; and an external water jacket casing surrounding at least a portion of the steam jacket casing, the external water jacket casing having an inlet; and wherein the method further comprises injecting water into the inlet of the external water jacket casing and extracting steam from the outlet of the steam jacket casing. 
     
     
         17 . The method of  claim 16  wherein at least one of the steam jacket casing and the product casing is capable of expanding independently and/or at a different rate of thermal expansion as compared to the water jacket casing. 
     
     
         18 . The system of  claim 17  wherein at least one casing selected from the product casing and the steam jacket casing comprises spacers, whereby the at least one selected casing remains substantially concentric with the external water jacket casing during gasification of the coal deposit. 
     
     
         19 . The method of  claim 13  wherein the non-vertical reaction shaft assembly diverges from vertical by more than 15 degrees. 
     
     
         20 . The method of  claim 13  wherein the electric torch operates with steam as plasma gas. 
     
     
         21 . The method of  claim 13  wherein the electric torch comprises one or more directional jets which may be actively or passively vectored to shape the reaction cavity. 
     
     
         22 . The system of  claim 21  further comprising operating the electric torch to separate positively charged species from negatively charged species or to separate oxidizers from reducers or both and expelling separate directional jets thereof. 
     
     
         23 . The method of  claim 13  wherein the distance below ground surface is greater than about 3,000 feet (914.4 m). 
     
     
         24 . The method of  claim 13  wherein the externally-supplied liquid is water, which is utilized as coolant, reactant, and/or moderator during gasification, and from which the electric torch produces steam and oxygen for its operation. 
     
     
         25 . The method of  claim 13  wherein water is the only fluid injected into the electric torch and the non-vertical reaction shaft assembly following startup.