Control Technology For Volatile Organic Compounds Treatment Based On MLD Model

Volatile organic compounds released in the atmosphere during industrial process are one of the main air pollution sources. There are lots of methods to treat air pollution, among which reverse flow reactor that combines reverse flow technology and catalytic combustion technology is akeady industrialized and widely used. As this technology become more and more popular, the relevant theory causes people's attention. But due to the complexity of the treatment course, there's few paper published about this technology, especially those about control strategy of the process. This paper analyzes the whole process from a new approach. Considering that the process has the property of hybrid system, firstly a MLD model of the process was built and then model predictive control (MPC) strategy for this system was presented. At last a PLC control system that was akeady employed in actual industrial work field is introduced. The main content of this paper is as follow:1. The process of VOCs treatment by reverse flow catalytic combustion reactor and its speciality was introduced. Then the main control technology used for this process was summarized.2. Comparing with the characteristic of hybrid system, the VOCs treatment process by a reverse flow reactor was analyzed. As a result the idea of describing the process with a MLD model that used in hybrid system was presented. The fundamental theory of MLD modeling was introduced, and then the step of modeling and its main idea with piece-wise linear dynamic systems and piece-wise linear output functions as examples. At last MPC control arithmetic based on MLD model was introduced.3. Most of available references take the reverse periodic time as a constant value when controlling the process based on principle model. However, this is not reasonable for actual industrial field. In fact, it's an effective method to change the dynamic behavior of the process by adjusting reverse periodicity. In this paper, a principle model was introduced and then it was simplified and reorganized in order to build the MLD model of the process. Subsequently a MLD model of a whole periodicity of the process wasbuilt. According to the simulation result, the model can well show the process's dynamic behavior. But due to omitting the factor of axial temperature and mass transfer during model simplifying, the MLD model is less accurate than the original principle model. That is the cost of simplification.4. Control strategy employed MPC arithmetic was presented and the performance index function was given. Aiming at that control strategy and the system's feature, a hardware configuration plan was given. Due to the objective condition of the work field and some other reasons, this control system wasn't applied into the actual field. But a PLC control system was implemented instead. At the end of this paper, a PLC control system of reverse flow reactor was explicated. It was already used as environmental protection equipment in an adhesive product manufactory. The running data noted from work field shows that the system works well and can gain the VOCs reduction goal.