[Mechanism and Influencing Factors of Increasing Soil Temperature by in-situ Electrical Resistance Heating].

The mechanism and influencing factors of an in-situ thermal remediation using electrical resistance heating were investigated. The effects of electrical current, heating method, rehydration, and negative pressure on soil heating and energy consumption were studied using in-situ electrical resistance heating equipment. The results showed that there were two main mechanisms for soil heating. Firstly, electric energy was converted into heat energy, whereby direct heating of the soil by electricity increased the soil temperature. This mechanism mainly existed in the soil between two electrodes. The second was heat conduction, whereby the soil temperature between the electrodes was the highest, and the heat gradually transferred from the high-temperature soil to the low-temperature soil, such that the temperature of the soil far away from the electrode connection gradually increased. The heating current affected the rate of increase of the soil temperature. The higher the current was, the faster the soil temperature rate of increase was and the lower the unit energy consumption was. Compared with continuous heating, intermittent heating had a slower heating rate and required a longer time to reach the same temperature. However, the energy consumption per unit was low and only 45.2% of that of continuous heating. During the heating process, water should be continuously added to the soil around the electrode to maintain a high current and continuous heating. The negative pressure of extraction was large, the soil heat loss was large, and the unit energy consumption was high. In actual projects, appropriate technological conditions should be selected according to time, cost, and the removal rate as a means of improving the efficiency of the in-situ resistance thermal desorption remediation of contaminated soil, reducing energy consumption, and shortening the time limit.