Research On Key Technology Of Cement Raw Meal Composition Detection Based On Near Infrared Spectroscopy

Cement is an essential basic construction material.In the 13th five-year plan,the country puts forward higher requirements for the production efficiency and environmental protection standards of the cement industry.In the production process of cement,the quality of the finished cement is directly determined by the quality of cement raw meal.At present,since the quality detection of cement raw meal has problems such as slow detection speed and radiation pollution,the quality improvement of cement raw meal is restricted.Near-infrared spectroscopy(NIRS)detection technology was first used in the quantitative detection of substances in 1977,exhibiting great advantages of fast speed,high precision,and pollution-free.Then,it has been developed rapidly in the field of organic compounds composition detection.However,there is little research on the near-infrared spectrum detection of the mineral composition related to cement raw meal because the near-infrared absorption peak generated by the chemical bond in the mineral composition is more than one order of magnitude smaller than that in the organic matter.In recent years,the research on NIR detection of inorganic components has gradually emerged with the improvement of the detection accuracy of the near-infrared spectrometer.Therefore,the NIR quantitative detection of cement raw meal becomes more feasible.In this paper,the composition detection of cement raw meal is investigated based on the near-infrared spectroscopy detection technology.The main research contents of this paper are as follows:(1)The hardware design of the near-infrared spectrum detection system for cement raw meal was completed,the possible spectral noise in the detection process was analyzed,and the relevant problems were optimized.Besides,the near-infrared spectra of four raw materials(limestone,sandstone,coal gangue,and iron powder)were analyzed.The positions of the absorption peaks of the components were preliminarily determined by comparing the main components of the four materials and the main absorption peaks in the spectra.Then,the near-infrared spectra of calcium carbonate,silica,iron oxide,and alumina were detected.Moreover,the spectral range of the components to be measured in the cement raw meal spectrum was further determined.Finally,the spectral ranges of calcium carbonate,silica,iron oxide,and alumina were determined to be 4100cm-1 to 4400cm-1,4400cm-1 to 4600cm-1,4000cm-1 to 4800cm-1,and 4400cm-1 to 4800cm-1,respectively.(2)A control test was designed to select the most suitable pretreatment method and modeling method for the detection of various components in the cement raw meal.Besides,144 times of model building for four components and the validation set prediction under each model were completed using 12 groups of preprocessing methods and 3 modeling methods.Then,the most suitable preprocessing method and modeling method were determined by comparing the prediction results of the model.Finally,calcium carbonate is modeled by SVR and pretreated by SNV;silica is modeled by SVR and pretreated by SNV;alumina is modeled by SVR and pretreated by SNV;iron oxide is modeled by SVR and pretreated by MSC+SG.The average error of prediction results is 0.2%for calcium carbonate,0.16%for silica,0.1%for alumina,and 0.022%for iron oxide.(3)Aiming at the problem of temperature interference and humidity interference,the influence of temperature and humidity on the near-infrared spectrum of cement raw meal was investigated and the temperature and humidity compensation of the model was performed by the method of mixed sample correction.The final results indicate that RMSEP of silicon dioxide,aluminum oxide,iron oxide,and calcium carbonate decreased by 25%,31.3%,33.3%,and 25%,respectively after humidity correction;meanwhile,RMSEP of silicon dioxide,aluminum oxide,iron oxide,and calcium carbonate decreased by 36.4%,27.5%,50%,and 36.4%,respectively after temperature correction.(4)A set of the standardized testing process is designed by applying the established near-infrared spectrum test model of cement raw meal to the cement plant.Then,the contents of calcium carbonate,silicon dioxide,aluminum oxide,and iron oxide in 48 samples of cement raw meal from the cement plant were detected by this detection process and compared with X-ray fluorescence detection.Finally,the average errors of calcium carbonate,silica,alumina,and iron oxide were 0.204%,0.306%,0.069%,and 0.037%respectively;this met the requirements of the cement plant.