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WOWClean® Multi-Pollutant Reduction System
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WOWClean® is a standalone multi-pollutant removal system for installation on existing coal-fired power plants, boilers, furnaces, incinerators, gasifiers and other flue gas waste heat sources. The WOWClean® system removes nearly all the pollutants from a flue gas without using multiple pollution reduction systems such as a Flue Gas Desulfurization (FGD) unit, Selective Catalytic Reduction (SCR) system or Thermal Oxidizers (TO). In addition to removal of SOx, NOx and particulates, the WOWClean® system has demonstrated the capability of removing Mercury emissions and reducing CO2 greenhouse gases by 25% or more from flue gases.
The WOWClean® system was designed to operate with low temperature flue gases when using the WOWGen® power plant in a single or dual turbo-expander configuration or as a standalone pollution reduction system. Depending on the flue gas temperature, quenching methods may be required to reduce flue gas temperatures to levels conducive to low temperature flue gas cleaning with the WOWClean® system. A description of the WOWClean® system is provided below along with a flow path schematic.
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First Stage Reactor: The first stage reactor has the capability to simultaneously remove acid gases, heavy and sub-micron particulates, mists, metals, dioxins/furans, sulfur oxides and mercury with efficiencies >95%. The first stage reactor is highly efficient where flue gas streams fall into one or more of the following categories.
1. The flue gas has a high moisture content
2. The gas stream includes sticky particulates
3. The collection of sub-micron particulate is required
4. The flue gas has acid droplets or mist – SO3
5. The temperature of the flue gas approaches the gas dew point
If not used with a WOWGen® system, the first stage includes a preconditioning quenching system that allows reducing the slipstream flue gas temperature to near ambient while absorbing heavy particulates in the flue gas. This reduces flue gas temperatures that are not already at levels compatible with efficient scrubbing and rapid chemical reactions – reduced resident time.
The purpose of the WOWClean® is to remove particulates, acid mists, and other contaminants and eliminate NOx and SOx levels in a flue gas. Of primary importance is to convert as much NO as possible to nitrogen compounds in the initial stages that are soluble in water (NO2 or NO3) or will react with chemicals in the second and third stage. Removal of as much NOx and SOx as possible in the first stage reactor reduces the cost of chemicals needed to remove the levels of SOx and NOx in the flue gas downstream of the first stage reactor.
The first stage reactor is a unique Non-Thermal Plasma (NTP) “cold” combustion process that produces free radicals from electrical energy to generate favorable chemistry for oxidizing pollutants (decompose) to more manageable chemical compounds. This is achieved “electrically” by using high intensity electrodes to produce compounds that chemically react with pollutants in the flue gas stream. The NTP is tuned to allow oxidizing of NOx, SOx and other vaporized pollutants, including heavy metal compounds, that can be removed using chemical additives in the downstream stages. NO is the most difficult pollutant to remove and oxidization of NO is greatly increased with the WOWClean® first stage reactor. Low temperature flue gases are important for the thermal stability of the first stage reactor and thermal decomposition of the favorable oxidizing chemicals is known to proceed rapidly at temperature ranges above 212 oF and can increase by a factor of 13 when flue gases are above 300 oF.
The first stage scrubber section allows injection of water-diluted chemicals to react with the decomposed compounds and remaining pollutants in the flue gas stream. The wet scrubbing processes offer simultaneous removal of NOx and SOx using spray nozzles for chemical injection to optimize removal of chemical compounds in the flue gas. Any remaining pollutants in flue gas will be removed in the downstream reactors.
Second Stage Reactor: The second stage reactor is a transition section that changes the flow direction from vertical to horizontal and incorporates water/chemical injection spray nozzles and packing to scrub out chemical compounds. This is a low velocity section that promotes higher residence time for more efficient chemical reactions. Heavy metals and neutralized pollutants will be trapped in the wastewater as they are condensed and collected in the sump below the packed bed of this second stage section. Chemicals are used in this stage to react with the water-soluble chemicals from the first stage to produce stable salts and other safe or saleable compounds, including metals.
Third Stage Reactor: The third and final stage reactor is nearly identical to the first stage reactor and is used to generate oxidizing compounds and additional injection of scrubbing chemicals, if necessary, to react with any residual pollutants such as SOx and NOx, while removing any remaining particulates and water soluble pollutants such as SO3. The third stage reactor is highly effective in removing PM2.5 and PM10 particulates and collecting any remaining acid mist in the flue gas resulting in a clean flue gas exiting the WOWClean® exhaust stack. Depending on the pollution levels in the flue gas and/or removal efficiencies desired, the third stage may or may not be required.
The resulting flue gas is nearly free of heavy metal oxides, SOx, NOx, PM2.5, PM10 and any acid mists, dioxins/furans and VOCs. The clean flue gas is discharged from the WOWClean® via an exhaust fan. The final flue gas, free of contaminants, can be naturally dispersed and diffused into the environment since its molecular weight is now equivalent to the surrounding air.
The by-products from the WOWClean® can be a broad range of liquids and solids including heavy metals, acids and stable salt solutions, depending on the concentration of pollutants in the flue gas. The WOWClean® process neutralizes these by-products with the resulting effluent discharged in the form stable salts and other precipitated pollutants. Since heavy metals, including Mercury, are removed from flue gases, these by-products require careful assaying and handling and can be safely disposed of or sold in the case of fertilizers, acids or metals.
Every flue gas stream has a unique combination of pollutants and testing can be conducted using WOW Energies' 2,500 to 4,000 ACFM pilot plant to determine the type and percentages of pollutants; the interaction between pollutants when exposed to WOWClean® processes; the quantity and combination of chemical additives required; and the overall efficiency.
The WOWClean® pilot plant was built with funds from a $1.6 million cost-sharing grant to WOW Energies issued by the Texas Commission on Environment Quality (TCEQ) in 2005. The TCEQ grant program provides for testing of the mobile pilot plant at any facility interested in reducing/eliminating emissions from flue gas stacks.
Contact Wow Energies for more information about setting up a test for your plant.
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Testing of this pilot plant was completed in the fall of 2006 on the AES 150 MW petroleum coke (“petcoke”) fired cogeneration power plant in Pasadena, TX and on the Boralex 40 MW wood waste fired power plant in Livermore, MA.
Test results, verified by third party testing in accordance with EPA and TCEQ test procedures, demonstrated the capability of the WOWClean® system to remove nearly all pollutants from a flue gas stream including Mercury while reducing CO2 greenhouse gases.
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