Process and system for converting waste to energy without burning

Abstract

This invention relates to a power recovery process in waste steam/CO 2 reformers whereby a waste stream can be made to release energy without having to burn the waste or the syngas. This invention does not make use of fuel cells as its critical component but makes use of highly exothermic chemical reactors using syngas to produce large amounts of heat, such as Fischer-Tropsch. It also relates to control or elimination of the emissions of greenhouse gases in the power recovery process of this invention with the goal of producing energy in the future carbonless world economy. A New Concept for a duplex kiln was developed that has the combined functionality of steam/CO 2 reforming, heat transfer, solids removal, filtration, and heat recovery. New methods of carbon-sequestering where the syngas produced by steam/CO 2 reforming can be used in Fischer-Tropsch processes that make high-carbon content compounds while recycling the methane and lighter hydrocarbons back to the reformer to further produce syngas at a higher H 2 /CO ratio.

1 . A system consisting of an improved rotary kiln for carrying out steam/CO 2  reforming, where the preferred features of waste volatilization, steam/CO 2  reforming, gas heat exchange, filtration and solid separation are combined into a single duplex kiln that uses in the primary region a heated hollow flight screw to begin the endothermic steam/CO 2  reforming of the biomass or waste feedstock, where the off-gases are carried into a second region where inductively-heated annular surfaces radiatively heat the gases to 800-1050° C. (1470-1920° F.) and particulate is removed so that these hot gases can pass now counter-currently through the central shaft and then through the hollow flight screw internal cavities to supply the reforming heat needed to do the endothermic chemistry and cool the syngas for kiln exit. 
     
     
         2 . A system in  1  that includes spiral vanes to carryout a cyclonic separation of entrained solids so that the syngas produced has high quality so to avoid detrimental effects of fuel cell poisoning arising from undesirable constituents in the waste. 
     
     
         3 . A system in  1  that includes an internal high-temperature porous ceramic or metal filter cartridge to further remove entrained solids so that the syngas produced has high quality so to avoid detrimental effects on downstream process units of catalyst poisoning arising from undesirable constituents in the waste. 
     
     
         4 . A process that provides the interface between a steam/CO 2  reforming waste conversion system generating syngas and a Fischer-Tropsch Unit that uses said syngas that makes paraffin wax product for carbon sequestration while recycling the light hydrocarbons off of the Fischer-Tropsch Unit, consisting of hydrogen, CO, CO 2 , methane, ethane, propane, etc. to avoid their emissions as powerful greenhouse gases and also recycling the lighter hydrocarbons to help maintain a higher H 2 /CO ratio of the syngas. The Fischer-Tropsch unit, which is exothermic, produces a large steam flow for turbine-generation of electricity and, thus, replaces the need for a fuel cell. This process method destroys the waste stream while at the same time the syngas is made to release energy without having to burn the waste or the syngas. 
     
     
         5 . A system of  1  where the kiln residue can be converted into carbon-containing fertilizer, and a carbon-sequestering, high-carbon content product of important commercial value. 
     
     
         6 . System of  4  where a Fischer-Tropsch synthesis reactor system is used to produce a high carbon content compound that can be sold into markets where it is never burned in its life cycle and therefore serves as a carbon sequestering agent and where the Fischer-Tropsch overhead stream containing hydrogen, CO, CO 2 , methane, ethane and light paraffins are recycled back to the steam/CO 2  reformer in order to make use of their high hydrogen content to achieve the more desirable H 2 /CO ratio around 1.0. 
     
     
         7 . A system of  4  where a Fischer-Tropsch unit combined with a parallel shift converter/pressure-swing absorption unit to accomplish the conversion of the syngas to commercially-marketable hydrogen fuel, ample steam to generate electrical power for the plant and for export, and a high-carbon content organic product paraffin that sequesters substantially the carbon in the waste stream—all without any burning of the waste or the syngas. 
     
     
         8 . A system of  7  where the light gases from the Fischer-Tropsch unit are recycled back to the steam reformer for destruction and avoiding release to the environment. 
     
     
         9 . A system of  7  where carbon dioxide and a portion of the hydrogen from the Shift and Pressure Swing Absorber units are recycled back to the steam reformer to adjust the H 2 /CO ratio for optimum utilization in the Fischer-Tropsch unit. 
     
     
         10 . A system of  7  where small impurities in the syngas that could damage the sensitive catalysts in a high temperature fuel cell do not damage the more robust catalysts (i.e. iron or cobalt-based) in a Fischer-Tropsch unit. 
     
     
         11 . A system of  4  where the best clean-up of syngas impurities involves a process where there are both a high temperature filtration step and a sulfur-, chlorine-, and nitrogen containing compound removal step as well as a chilling and condensation step downstream which includes a HEP A filter and a guard bed to protect high temperature fuel cell electrochemical catalysts. 
     
     
         12 . A system of  4  where the best clean-up of syngas impurities involves a process where there are both a high temperature filtration step and a sulfur-, chlorine-, and nitrogen containing compound removal step as well as a chilling and condensation step downstream which includes a HEPA filter and a guard bed to protect Fischer-Tropsch catalysts. 
     
     
         13 . A system of  4  where a Fischer-Tropsch unit that is greatly simplified because its many tail or overhead streams can be used as recycle to the steam/CO 2  reforming process. 
     
     
         14 . A system of  6  where a heat recovering exothermic reactor that contains a supported catalyst immersed in water to maintain the catalyst at a constant temperature by the boiling of the water to make steam that is used to generate power. 
     
     
         15 . A system of  4  where a power recovery system that involve the combined use of a shift and PSA unit as well as the Fischer-Tropsch unit to make best use of recycle streams and waste heat. 
     
     
         16 . A system of  14  where an exothermic reactor consists of a Fischer-Tropsch reactor. 
     
     
         17 . A system of  14  where an exothermic reactor consists of a methanol synthesis reactor. 
     
     
         18 . A system of  14  where an exothermic reactor consists of a methanation reactor. 
     
     
         19 . A system of  1  where heat to the kiln sections doing endothermic steam/CO 2  reforming is supplied by recycling the syngas through the holoflite screw to heat the waste and do reforming. 
     
     
         20 . A system of  4  where hot syngas from a conventional kiln followed by the steam/CO 2  reformer is heat exchanged with another inert gas, such as carbon dioxide or air, to heat the kiln by indirect heating in the oven surrounding rotary kiln tube by means of a series of injection jets, where gas burners are normally located. 
     
     
         21 . (canceled)