Fuzzy Coordination Control Strategy and Thermohydraulic Dynamics Modeling of a Natural Gas Heating System for In Situ Soil Thermal Remediation

Abstract

Soil contamination remains a global problem. Among the different kinds of remediation technologies, in situ soil thermal remediation has attracted great attention in the environmental field, representing a potential remedial alternative for contaminated soils. Soils need to be heated to a high temperature in thermal remediation, which requires a large amount of energy. For the natural gas heating system in thermal remediation, a fuzzy coordination control strategy and thermohydraulic dynamics model have been proposed in this paper. In order to demonstrate the superiority of the strategy, the other three traditional control strategies are introduced. Analysis of the temperature rise and energy consumption of soils under different control strategies were conducted. The results showed that the energy consumption of fuzzy coordination control strategy is reduced by 33.9% compared to that of the traditional control strategy I, constant natural gas flow and excess air ratio. Further, compared to the traditional control strategy II, constant excess air ratio and desired outlet temperature of wells, the strategy proposed can reduce energy consumption by 48.7%. The results illustrate the superiority of the fuzzy coordination control strategy, and the strategy can greatly reduce energy consumption, thereby reducing the cost of in situ soil thermal remediation.

Planned Heating Control Strategy and Thermodynamic Modeling of a Natural Gas Thermal Desorption System for Contaminated Soil

“…Model of Thermal Well Figure 4c illustrates individual temperature points of the heat well. The temperature dynamics of the inner pipe and outer pipe of the thermal well, which are based on the energy conservation principle, are represented by Equations (7)-(8) [31,37]:…”

“…(c) Heat-Flow Model As presented in Figure 5, the temperature dynamics of the soil [31,33] can be expressed by:…”

“…According to Equations (5) and (6), the natural gas mass flow rate Gg and the air mass flow rate Ga can be separately expressed by Equations (29) and (30), correspondingly. Furthermore, the natural gas inlet pressure Pg and the air inlet pressure Pa can be obtained by Equations (31) and (32), where Pb is inlet pressure of the burner. Given the flow resistance of the inlet natural gas pipe R g and that of the inlet air pipe R a calculated from Equation (24), the parallel flow resistance R par [49,50] can be presented by Equation (25), where φ g and φ a characterize the valve opening of the inlet natural gas pipe and air pipe.…”

“…According to Equations (5) and (6), the natural gas mass flow rate G g and the air mass flow rate G a can be separately expressed by Equations (29) and (30), correspondingly. Furthermore, the natural gas inlet pressure P g and the air inlet pressure P a can be obtained by Equations (31) and (32), where P b is inlet pressure of the burner.…”

“…Due to the disadvantages of the aforementioned experimental research, a lumped-parameter method is employed in the present study in order to investigate the influence of moisture migration on the heating performance of the soil. Furthermore, other correlative studies [31][32][33] by our team using a numerical simulation method or a lumped-parameter method have been conducted and published online.…”