Adaptability Analysis And Dynamic Characteristics Of A Natural Gas Desulfurization Unit

During actual operation, the natural gas desulfurization device is usually faced with the disturbance and fluctuation of feed flowrate, acid gas content in raw gas and the temperature of lean amine,due to natural gas development,the change of natural gas source and the fluctuation of ambient temperature. In order to keep the desulfuration unit operating efficiently and steadily,the adaptability and dynamic characteristics of the desulfurization device were investigated by means of the steady-state simulation and dynamic simulation technology, which could also provide theoretical support.In this thesis, the steady-state model of desulfurization device was established on the base of HYSYS simulator. Compared with the actual operation data, the simulation results of the steady-state model have excellent performances in prediction accuracy. According to the analysis of difficulty degree of the device parameters control, these parameters were divided into controllable parameters and uncontrollable parameters. According to the single factor analysis and sensitivity analysis for the controllable variables, how these parameters affected the observing indexes (the concentration of H2S in wet sweet gas, acid load in rich amine and unit energy consumption) was elucidated and the degree of influence on the indexes come from the controllable parameters was determined. With the response surface analysis regard to the uncontrollable parameters, the quantitative relationship equations between raw gas flow, the concentration of H2S in raw gas, the concentration of CO2in raw gas, the temperature of lean anmine,appropriate lean amine flow rate and the renewable energy consumption in corresponding condition was conducted and the quantitative relationship equations of them were attained. Based on the regression equations, the interaction effect on the flow rate and energy consumption was analyzed. The results show that the interaction between any two factors is significant, while the interaction between flowrate of feed gas and temperature of lean amine solution and the interaction between the concentration of H2S and CO2in feed gas can be neglected.The desulfuration device’s dynamic mode was built successfully by adding the equipment information and control scheme into the steady state model. In dynamic analysis, the concentration of H2S in wet sweet gas, the concentration of H2S in feed gas, the temperature of lean amine and the flow rate of lean amine were defined as disturbance variable. The dynamic characteristic of the device was investigated by giving these disturbance variables the same magnitude disturbance including positive changes and negative changes. Faced with the disturbance, the acid load of rich solution showed large variation and the regeneration energy consumption had no obvious adjustment, which may be attributed to the fact that lean amine cannot adjusted automatically under the disturbance. In order to improve the device’s adaptability, proportion control and regression control were approved. The results showed that the lean amine flow rate could change with the feed rate disturbance automatically in proportion control, and lean amine flow rate can adjust with multi disturbance variable in regression control. What’s more, regression control can make the unit be an auto-adaptive system.