Study On Quantitative Optimization Of Gas Detectors Placement For Refining Installations

As an important protective layer of refining unit,gas detector can reduce the loss greatly if they function properly in the event of leak.However,statistical data show that the efficiency of gas leak detection and alarm is not satisfactory.In order to strengthen the security of refining unit and the reasonable distribution of gas detection system resources,supported by Natural Science Foundation of Shandong Province and the Fundamental Research Funds for the Central Universities,this paper researches on the quantitative optimization of gas detector for refining unit.A technical scheme for the optimization of gas detector placement in the refining unit is proposed.1.Dangerous gas leakage dispersion model of based on CFDTo reflect the meteorological conditions of near surface layer in the dangerous gas leakage dispersion model of based on CFD,a method for setting index model of wind field profile and vertical gradient of temperature is proposed.Wind field consistency check,temperature field consistency check and validity check of CFD model based on empirical model is also proposed.The numerical simulation by the CFD model can obtain hazardous gas leakage and diffusion concentration field in accordance with field device layout and meteorological conditions,and finally provides support for risk quantification of hazardous gas leakage.2.Quantitative construction method of dangerous gas leakage scene setTake the leakage source and the condition of wind field as main random factors,this paper proposes a quantitative construction method of dangerous gas leakage scene set in refining unit,including identification of leakage hazard,discrete description of leakage source and wind field conditions,prediction of gas leakage susceptibility and joint distribution probability of wind field,fusion mechanism of leakage source and wind field.Considering both the accuracy and economy of engineering calculation,the risk index of the leakage scene is defined by the combination of the experience model of gas diffusion and the probability of occurrence to obtain optimal scheme of leakage scenario set.3.Quantitative optimization model of gas detectors placementBased on the triad model and gas leakage scene set,this paper proposes the plant real-time quantitative risk as the gas detectors layout decision-making risk.Take minimizing the decision-making risk value as the optimization objective and the number of gas detectors as the constraint conditions,A p-median problem(PMP)is established considering reliability and voting logic.Considering the long tail of the scene consequences,MRPMP-UV model considering Conditional-Value-At-Risk(MRPMP-UVCVaR)presented in this article adds constraint of CVaR.These two models takes the selection of gas detector placement as the decision variable.Enumeration of detector placement satisfying the constraint function belongs to the NP(Non-Deterministic Polynomial)-hard problem.Particle swarm optimization(PSO)is used to solve the model.Analysis of scenario sensitivity is proposed to study the dependence of the optimization scheme on leakage scenario.Under a certain confidence level,the confidence interval of the target value offset for the optimization would be achieved.4.Case analysisThrough the above research,the method was applied to the hydrogen sulfide detectors optimizing for a diesel hydrogenation unit and provides the optimal layout number and location quantitatively.Case analysis demonstrates that the optimal hydrogen sulfide detectors placement can significantly improve the detection efficiency.