Design And Reliability Analysis Of Limestone Milling And Transmission Control System

The emission of sulfur dioxide in thermal power plant is seriously damage the human living environment, even impacts human's health directly. With the improvement of quality requirements on environment, we are paying more and more attention to flue gas desulphurization on the thermal power plant.As the main desulfurization agent of coal-fired boiler, limestone milling system has become an important part of environmental protection. For the power plant, high reliability control system in the limestone milling will reduce stopping frequency of desulfurization system, witch making the costs of maintenance and examination greatly. It ensures the desulfurization rate of the power plant, and makes contributions to environmental protection projects.Firstly, this article analyzes the structure of limestone milling production line, describes in detail every composition, function and the whole process.According to process requirements, combined with the milling function, overall control scheme of various components is given in this paper.Secondly, design process of the limestone milling control system is described from both hardware and software.It includs system components, parts selection, communication network, control procedures and interface design.In order to improve the reliability of automatic control system, Siemens S7-400H fault-tolerant redundant series PLC is selected to the redundant design.In addition, programming software STEP 7 and interface software WINCC are used to making the control system perfect.Finally, reliability theory is applied in the paper to analysis the reliability of limestone milling system.Markov state transition method is used to transition analyzing, calculating and comparing the difference of the main control system between before and after redundancy.At the same time, reliability diagram was drawn according to the composition of limestone milling sysem.This paper has caculated the reliability of milling system through using data provided by the manufacture.This control system of limestone power production line should work well to ensure the stable running of desulfurization in power plant. Additionally, it has certain technical reference to the similar milling control system.