Beneficial Use of Landfill Gas for Leachate Evaporation and Power Generation

Transcription

1 Beneficial Use of Landfill Gas for Leachate Evaporation and Power Generation Efficient use of Energy Turning waste to energy, liabilities to assets and visions into reality.

2 Table of Contents BENEFICIAL USE OF LAND FILL GAS THE HTI ADVANTAGE LANDFILL GAS COMBUSTION & LEACHATE EVAPORATION PLANTS FEET OF CONTROL KEY FEATURES LEACHATE EVAPORATION SYSTEM ONE POWER GENERATION SYSTEM TWO Turning waste to energy, liabilities to assets and visions into reality.

3 LANDFILL GAS COMBUSTION & LEACHATE EVAPORATION PLANTS Heat Transfer International (HTI) engineers have designed, fabricated and installed waste-to-energy systems since the 1970 s. Plants in operation today continue to recover energy, destroy pollutants and meet all environmental codes. Industrial processes reclaim precious metals, destroy medical waste, clean acid-laden gases and process sludge, biomass and municipal solid wastes. Landfills have been brought under the regulatory blanket, wherein the noxious leachate must be collected and treated and the odoriferous methane laden landfill gas must be collected and burned. To meet new codes, leachate is transported to water treatment plants, or evaporated by combustion of the landfill gas in fired evaporators. Surplus landfill gas is burned in specially constructed flare stacks. HTI has developed two breakthrough systems, each of which is more efficient and cost effective than present competitive technologies. The first will burn the landfill gas to heat air indirectly for combustion and leachate evaporation. The second will generate power by indirectly heating air to a temperature and pressure needed to drive an air turbine generator set. The turbine exhaust (clean air) evaporates the leachate and provides air to combust the volatile hydrocarbons. BENEFICIAL USE OF LAND FILL GAS THE HTI ADVANTAGE Heat Transfer International has developed two beneficial methods for disposing of noxious landfill-produced leachate and gases. Each system combusts the methane-rich landfill gas in an all-ceramic, vertical oxidizer, utilizing air that has been indirectly heated by HTI s patented all-ceramic, shell and tube heat exchanger. The ceramic construction permits heat transfer at higher temperatures than metal exchangers can withstand, resulting in higher thermal efficiency. The preheated air stream is split, with part being sent to the landfill gas burner as described above and the balance to a leachate evaporator. This mass contains non-combustibles, unburned volatiles, inert landfill gases and excess air along with the combustion products. By using only hot air as a medium to vaporize the leachate, the ratio of volatiles to combustion air is higher. The hot air mixes with the volatile hydrocarbons and vaporizes the water. The leachate vapor and warm air are sent to the vertical oxidizer and indirectly heated further to raise all the leachate vapor above the combustion flammability limits of the hydrocarbons. The preheating of air for landfill gas combustion and leachate evaporation means, even as the methane percentage in the landfill gas decreases, the disposal system will continue to operate without the need for auxiliary fuel. A second unique, patented HTI system will generate electrical power without the need for a steam boiler and all the related water treatment, cooling tower, pumps, etc., that a typical steam power plant requires. The HTI system combusts the landfill gas and indirectly heats the air in a high pressure, high temperature, hybrid ceramic heat exchanger. The clean air is sent to an air turbine generator set for production of electrical power. The hot air turbine exhaust is then forwarded to the leachate evaporator. Again, the leachate is vaporized with air rather than products of combustion. The utilization of the turbine exhaust to evaporate leachate, combined with the driving of an air turbine with high temperature, high pressure air, makes the process considerably more efficient than conventional steam plants. Plants generating as low as one megawatt can be capitalized and produce power for sale at rates competitive with major utilities. Turning waste to energy, liabilities to assets and visions into reality. 1

4 62 FEET OF CONTROL KEY FEATURES Vertical Ceramic Heat Exchanger (I) When destroying landfill gas and evaporating leachate only, the exchanger heats air indirectly to approximately 1400 F that is sent to the evaporator. When an air turbine is part of the system, the ceramic exchanger is supplied in conjunction with a second-stage, high alloy metal exchanger. The two units preheat the air, at pressure, to upwards of 2000 F and send it to an air turbine. The flue gas in both cases contains excess air, products of combustion and water vapor. The only visible plume will be from the water vapor. heating of the vapor and combustion air above the flammability limits of the volatiles. Landfill Gas Burner (V) A landfill gas booster fan supplies the gas to a dual-fuel, sealed burner that is designed to mix the low-btu-fuel with preheated combustion air from the ceramic heat exchanger. The sealed burner is furnished with burner management, flame safety equipment and propane pilot. In the event the methane percentage needed to maintain a stable flame drops, then auxiliary fuel will inject automatically. Tempering Air Stage (II) When the system is designed to evaporate leachate and combust landfill gas only, the tempering air section mixes in sufficient air with the flue gas products to control the discharge temperature at 1800 F. When an air turbine is used to generate electrical power, the tempering air section will control the inlet temperature to the ceramic heat exchanger at approximately 2300 F. The ceramic tuyeres are designed with a slotted front face and an offset single entrance from the outer side that permits the flow of air without direct radiation to the plenum. Overfire Air (III) Overfire air is injected and controlled to hold the first stage oxidizer exit at a preset temperature. Fail-Safe Design In the event there is a utility failure or interruption of landfill gas flow, gas and leachate valves will close automatically and the natural draft (stack effect) will induce combustion air to complete the burning of the volatiles remaining in the oxidizer. I Leachate Vapor Inlet Ducts (IV) Part of the water vapor, with volatiles and preheated air from the evaporator, is injected above the burner. The balance of the vapor is mixed with preheated combustion air and flows upward between the oxidizer inner and outer walls. This feature allows for both direct and indirect II III IV EVAPORATOR CONTROL ROOM VERTICAL OXIDIZER V Turning waste to energy, liabilities to assets and visions into reality. 2

5 LEACHATE EVAPORATION SYSTEM ONE POWER GENERATION SYSTEM TWO The proprietary systems and equipment depicted are protected by U.S. and foreign patents issued, patents pending and/or patents applied for. Turning waste to energy, liabilities to assets and visions into reality. 3