Study On Stability Enhanced Cement Raw Materials Quality On-Line Monitoring By Using Laser

Mastering the change of cement raw materials composition in real time has important significance to timely adjusting the proportion of raw materials and improving the quality of cement products.We developed an experimental laser-induced breakdown spectroscopy(LIBS)device for on-line cement raw materials quality monitoring in the way of ejecting gas-powder mixture,and many aspects of the optimization have bine done,forming a complete and reliable and accurate testing equipment by Integrating automation control calculation software.Firstly,we developed a laser power feedback adjusting technique,calibration the output power of laser by feedback adjusting the voltage of xenon lamp.With stabilization,the laser output power has maintained at the pre-set value 160mW for two months.However,the laser power without stabilization has decreased from 160 mW to 90 mW with a drop of 56%.Secondly,a beam expander(BE)and a concave mirror(CM)with a middle hole were employed to increase the excitation efficiency as well as the fluorescence collection efficiency.As a result,the line intensities of Ca(II)318.0 nm and Mg(II)279.7nm have increased of 30%while the RSD has decreased of nearly 50%.Finally,we developed a spectral normalization and matrix stabilization technique based on scattered laser of material flow.The scattered laser was used as a spectral normalization parameter to make the RSD of normalized spectra decrease from 35%to 23%,which is much better than that of full spectrum normalization 28%.At the same time,by comparing the scattered light intensity and the pre-set value,the vacuum conveyor driven pressure could be adjusted to correct the deviation of the state parameter of the material flow,so as to realize the long-term stability of the ejected material flow matrix.The stability of the material flow matrix is increased from 2.79%to 1.63%.In addition,a new data processing method is constructed,preprocessing spectral data by series of methods,such as local thermal equilibrium determination,spectrum screening,UV light intensity normalization,and so on,then regression analysis the parameters of cement raw material by support vector machine.In order to verify the measurement stability of the optimized LIBS device,we chose 500 samples,of which 400 samples were used for calibration and the rest 100 samples were for validation.The results show that,the average relative error(ARE)has decreased from 1.01%to 0.43%,without any accidental large fluctuations.It can be seen that pulsed laser power stability,optical optimization and scattered spectra normalization method proposed in this experiment can significantly improve the measurement stability of LIBS device,and meets the requirements of on-line cement raw materials quality monitoring in cement industry.