The Design Of Online Carbon Content In Fly-ash Monitoring System Based On The Loss-on-ignition Method

The carbon content in flying ashes of boiler is an important indicator to how to show the combustion efficiency of coal-fired boiler in thermal power plant. This index can directly show the combustion efficiency of boiler. Therefore, supervising the carbon content of flying ashes in real time can help guide and operate the correct coal-air ratio,thus improving the control level of boiler combustion, reducing the coal needed for generating electricity and enhancing the economical operation of boiler. In the current applied method of measuring carbon content in fly ash, the method of loss on ignition is the most precise method whose measuring results will least be influenced by external factors. Therefore, this paper takes loss on ignition as the measuring method, and combined with online monitoring technique, the paper will design a kind of measurement system of online carbon content in fly-ash based on the method of loss on ignition.Through the research on the current device of online carbon content in flying ash, the paper completes the overall design plan of the online carbon content in fly-ash on the basis of combustion method. This measuring device will regularly collect the fly ash with carbon contents in flue through fly ash sampler after combustion and it put the ash sample to burn in the crucible. Then the device can get the data of carbon content by measuring the ash sample in different stages with weighing sensor. Its acquisition system use Siemens S7-200 PLC to achieve the acquisition of weighing analog signals and in technical part, it uses software programming to automatically collect, weigh and burn the fly ash. And it uses the DOPSoft to create the user interface which can friendly show the data in real time. In this paper, the author further studies the entrance of fly ash sampler.Through the research on theory of equivalent sampling and simulation on the ash two-phase flow of the flue bottom with FLUENT software, it can get the distribution of concentration of fly ash. And it uses the software MATLAB to conduct data fitting to the results of fly ash concentration distribution acquired by numerical stimulation and get to know the position relation between fly ash concentration and sampling position, thus designing multipoint static balance isokinetic sampler. Finally, combining the carboncontent data with the benefit computational formula, the author can calculate benefits brought by lowering the carbon content after putting the carbon measuring device into operation by the plant unit.This system combines the traditional chemical loss on ignition method with online measuring technique, realizing the high-precision and intelligent online supervision of the carbon content of boiler fly ash in real time. The operating personnel can take the data and information offered by online supervision system, and it reduces the carbon content of fly ash through adjusting proper ratio of coal-air and improves the efficiency of boiler. And its benefits are considerably ideal and the results prove that the research in this paper is of great value to the production in the thermal power plant.