PLASMA GASIFICATION PROCESS DESCRIPTION OVERVIEW
The ALFA ENERGY SYSTEMTM begins with the thermal transformation of waste to produce a clean combustible gas referred to hereinafter as "Fuel Gas". The Fuel Gas is used to produce electricity in a combined cycle gas/steam turbine. Alternatively, the Fuel Gas can be used to produce ethanol (denatured ethyl alcohol), a fuel that can either be blended with gasoline or burned in an engine as a neat fuel. Heat generated by the process is used to produce electricity, superheat steam, heat boiler feedwater and to distill.
ZERO WASTE PHILOSOPHY
The process operates on a ZERO WASTE philosophy, defined as:
The recycling of all materials back into nature or the marketplace in a manner that protects human health and the environment.
- The conversion of any carbon-based material is in excess of 99%. Non-carbon-based materials are converted into vitrified glass. Molten metals are separated from the glass. NON-CARBON BASED FEEDSTOCK MATERIALS ARE CONVERTED INTO SALABLE PRODUCTS WITH NOTHING LEFT OVER. THERE IS VIRTUALLY NO NEED FOR A LANDFILL WITH THIS PROCESS!
- The Fuel Gas produced is much cleaner than standard gasification processes and only contains traces of some elemental contaminates such as particulates, chlorine, sulfur and metals (amounts depend on the feedstock). There are no tars, furans or dioxins. Depending on the waste input there may be trace amounts of other elements. Most of the particulate is removed by a cyclone back into the process, becoming part of the vitrified glass. The chlorine is then scrubbed out leaving dilute hydrochloric acid (HCL). The sulfur is removed in a wet scrubber, producing sodium bisulfite.
- The dilute HCL contains some amounts of particulate and metals, which are removed. The particulate and metals removed at this point amount to a fraction of 1% of the original feedstock.
- The dilute HCL can be concentrated to make a 20% salable HCL product. The water that is removed by either process is reused in the plant for makeup water. The only water discharge is cooling tower and boiler blowdown.
- The sole discharge into the air is from the turbine, which meets EPA standards.
- Heat from the process is used internally to produce electricity, distill ethanol and distill HCL.
- The technology for the patented Thermal Transformation process has been applied commercially to a variety of materials including Municipal Solid Waste (MSW). The developer of the process is a well-known and respected company.
- The process is designed using GUARANTEED TECHNOLOGIES!
PROCESS FLOW DESCRIPTION
The following is a description of ALFA Energy System™ process for transforming Municipal Solid Waste (MSW) and other waste materials into energy and useable by-products. The process can be broken down into four sub-systems: material handling, thermal transformation or plasma gasification, gas clean up, and steam and energy production. A flow diagram is shown at the end of this section.
- The incoming waste is weighed in and then deposited on the tipping floor from any of the trucks currently in use that pick-up and or transfer MSW. No tedious sorting or handling is needed. The only separation that is required will be large oversized pieces that won't fit into the shredder, heavy metal items like engines that may slow down the shredder or items that need special pre-processing, such as refrigerators, freezers and AC units that need the freon removed. Hazardous waste and medical waste are handled separately and not co-mingled with normal waste.
- The system is designed to process waste as quickly as possible. During delivery hours the waste is delivered faster than it can be gasified. Part of the waste is stored for processing at night and on weekends and holidays. Any oversized material is shredded and then conveyed to storage.
- The waste is completely cycled every 3-4 days. Should unscheduled shutdowns occur, the waste received from the municipality goes into the storage area which is designed to handle normal surges and continue accepting the waste.
- The waste is injected into the upper part of thermal transformer (also referred to as the plasma gasifier or reactor) and piles up in the body of the reactor. The plasma torches located at the bottom of the reactor generate a flame that is between 5000-8000º F.
- The organic material does not burn because there is not enough oxygen. The organic matter is transformed to a gas composed primarily of carbon monoxide (CO), hydrogen (H2) and nitrogen (N). This gas contains substantial energy and can be used in a variety of ways.
- The hot gas rises up through the waste piled in the reactor and begins the gasification process on the material piled in the reactor. By the time the waste has reached the bottom of the reactor, the high temperature, oxygen starved environment has totally transformed all organic compounds into a gas.
- The gas that exits from the top of the reactor and is made up of primarily carbon monoxide, hydrogen, water and nitrogen. Small amounts of chlorine, hydrogen sulfide, particulate, carbon dioxide and metals with boiling points less than 2280º F are contained in the gas. Because of the low oxygen atmosphere and high temperature, the base elements of the gas cannot form toxic compounds such as furans, dioxins, NOx, or sulfur dioxide in the reactor.
- As the gas exits the reactor it first goes to a proprietary gas reformer and then it is cooled in a series of high temperature heat exchangers. The sensible heat is reduced to about 270º F and is used to generate high-pressure steam that is fed to a steam turbine to produce electricity.
- The high temperatures from the plasma torches liquefy all inorganic materials such as metals, soil, glass, silica, etc. All matter, other than the metals, becomes vitrified or molten glass. The metal and glass flow out of the bottom of the reactor at approximately 3000º F. As the metal and glass flow from the reactor, they are quenched in a water bath. The glass forms obsidian like glass fragments. The metals are then separated from the glass.
- There is no waste left at the end of the thermal transformation. All of the waste is recycled into metal, glass or has been converted to fuel gas.
- After the fuel gas has left the heat exchanger, approximately 85% of the particulates are removed in a cyclone. A smaller percentage of the metals are also removed with the particulate. The ALFA particulate and metals are then injected into the molten glass. The components of the glass are locked into the glass matrix and cannot leach out. The vitrified glass material passes EPA leachability tests.
- The gas then goes through a scrubber where the hydrochloric acid (HCL) is scrubbed out to form dilute HCL water. The liquid goes through a series of nano filter membranes where the particulates and metal in the liquid are removed. The metals and particulate at this stage cannot go back into the glass and can either be sold to a metal refiner or removed to a landfill. This small amount of material is the only potential material that goes back to a landfill and represents less than a fraction of 1 percent of the waste feedstock. The clean HCL water is concentrated to 15-20% for commercial sale.
- The water in the gas is condensed out and is used to provide clean makeup water for the rest of the plant.
- The hydrogen sulfide (H2S) in the gas is scrubbed out to make fertilizer grade sulfur using a biological process or alternatively can be converted into sodium bisulfite. The gas then goes to a gas compressor and then to the gas turbine.
STEAM AND POWER GENERATION
- High-pressure steam from the primary heat exchanger goes to a steam turbine where it is converted to electricity. The electricity generated with this steam source provides most of the power needed for internal power requirements. The system is capable of generating all its own internal requirements.
- The fuel gas goes into a gas/steam combined cycle turbine where it is used to produce electricity.
- All the available heat in the process is used to make electricity or steam. The discharge temperature off the gas turbine is less than 270ºF. Any low-pressure steam (small amount) not used in the process is condensed.
- A facility designed with electricity production can export approximately one megawatt of electricity for each ton of MSW, depending on the moisture content and characterization of the MSW.