{"id":4366,"date":"2017-01-31T11:40:33","date_gmt":"2017-01-31T03:40:33","guid":{"rendered":"http:\/\/www.envguide.com\/%e5%8e%9f%e4%bd%8d%e5%9c%9f%e5%a3%a4%e4%bf%ae%e5%a4%8d-%e7%83%ad%e8%84%b1%e9%99%84\/"},"modified":"2018-01-28T04:57:16","modified_gmt":"2018-01-27T20:57:16","slug":"thermal-conduction-heating","status":"publish","type":"post","link":"https:\/\/us.envguide.com\/thermal-conduction-heating\/","title":{"rendered":"Thermal Conduction Heating"},"content":{"rendered":"

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Company Informaiton\uff1aClick<\/a><\/p>\n

What is Thermal Conduction?<\/p>\n

Thermal conduction is the process of heat flowing from the hot end of a solid object (like an iron rod) to the cold end. In soil or rock, heat flows from heater wells out into the formation by grain-to-grain contact (in soil) and across solid objects (rocks). The fluids (water, air, NAPL) in contact with the solids also heat up at the same time. The heat moves out radially from each thermal well until the heat fronts overlap.<\/p>\n

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TCH Installation<\/p>\n

Electrically-powered heaters and vapor extraction points were installed in situ, to heat contaminated soil to target treatment temperatures. Target treatment temperatures are typically 100\u00b0C for volatile contaminants and between 150\u00b0C and 325\u00b0C for semi-volatile contaminants.<\/p>\n

Benefits of TCH<\/p>\n

Thermal conductivity values for the entire range of known soils vary by a factor of less than plus or minus three, while fluid conductivity of soils may vary by a factor of a million or more. Compared to fluid injection processes, the conductive heating process is uniform in its vertical and horizontal sweep. Transport of the vaporized contaminants is further improved by the creation of permeability, which results from drying (and, if clay is present, shrinking) of the soil close to the heaters. Preferential flow paths are created even in tight silt and clay layers, allowing flow and capture of the vaporized contaminants. TCH produces uniform heat transfer through thermal conduction and convection in the bulk of the soil volume. This allows the achievement of very high contaminant removal efficiency with a nearly 100% sweep efficiency, leaving no area untreated. TCH can be applied at low (<100\u00b0C), moderate (~100\u00b0C), and higher (>100\u00b0C) temperature levels to accomplish the remediation of a wide variety of contaminants, both above and below the water table.<\/p>\n

TCH is the only major in situ thermal remediation technology capable of achieving target treatment temperatures above the boiling point of water.<\/p>\n

TCH is effective at virtually any depth in almost any media.<\/p>\n

TCH works in tight soils, clay layers, and soils with wide heterogeneity in permeability or moisture content that are impacted by a broad range of volatile and semi-volatile contaminants, such as:<\/p>\n

Applicable to Both In Situ and Stockpiled Soils and Sediments<\/p>\n

The TCH technology can be utilized to heat in situ soils and stockpiled soils and sediments. The design of the treatment system for in situ soils (ISTD) typically includes vertically installed heaters whereas the design of the treatment system for the stockpiled soils (In-Pile Thermal Desorption, or IPTD) typically incorporates horizontally installed heaters. Examples of the elements of each system are shown below:<\/p>\n

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The TCH technology can operate\u202finside, beneath, and near buildings and infrastructure<\/b>. This capability has been field proven at numerous projects.<\/p>\n

The TCH technology can be applied to contaminants in soils both above and below the water table (see also\u202fPermeability and Geology<\/a>) where the soils can be heated up to target treatment temperatures. Contaminants such as TCE, PCE, and other VOCs that have boiling points similar to water can be treated simply by steam distillation. Contaminants such as PAHs, dioxins, PCBs, and other SVOCs that have higher boiling points than water are treated by boiling off the water within the treatment zone, and then by heating the soil to the designated treatment temperatures. Where significant groundwater flow is present, additional measures such as groundwater management or a hydraulic barrier may be required. Steam injection was successfully used into the high-K zones to augment the ISTD process, thereby ensuring complete heat-up and treatment of both tight zones and permeable zones<\/p>\n

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  1. <\/b>Electrical Resistance Heating (ERH)<\/b><\/li>\n<\/ol>\n

    ERH has been widely applied and proven effective for free product recovery and enhanced vapor extraction at sites with volatile contaminants such as VOCs, CVOCs, and NAPLs, and is applied at low and moderate temperatures.<\/p>\n

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    What is Electrical Resistance Heating (ERH)?<\/b><\/p>\n

    When electric current is passed through the soil, the resistance it encounters causes the soil and fluids to heat up. The current flows from one electrode to another, primarily through the soil water. Once the water boils off, electrical conductivity becomes negligible and heating ceases; thus, water is added at each electrode to keep them from drying out. Heat-up with ERH is limited to the boiling point of water.<\/p>\n

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    ERH Process<\/b><\/p>\n

    Electrodes are installed in wells throughout the contaminated soil and groundwater volume. The electrode array is connected to a Power Delivery System unit that uses standard, readily available three-phase power from the grid. The process begins by passing current between electrodes causing the soil temperature to rise. This increased temperature results in the volatilization of contaminant compounds into the vapor phase for removal with vapor extraction techniques.<\/p>\n

    Comprehensive computer controls are used to regulate and optimize the thermal response of the target formation.<\/p>\n

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    ERH Advantages<\/b><\/p>\n

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