Study On Assessment Method Of Compliance With Air Pollutant Emission Limits Of Cement Industry Based On CEMS Data

The current assessment methods of compliance with air pollutants emission limits are mostly based on manual monitoring,and the emission limits are formulated based on hourly concentration data.With the wide and rapid application of continuous emissions monitoring system（CEMS）in key stationary sources and the continuous improvement of the quality assurance system of monitoring data,it is necessary to study and formulate assessment methods of compliance with air pollutant emission limits based on CEMS data.It is of great significance to study the emission control of air pollutants in the cement industry for improving ambient air quality due to cement industry belonging to high air pollutants emission industry.957 cement production lines from 510 cement enterprises located in 23 provinces（autonomous regions or municipalities）were collected in 2017.The screening principle of production line was developed according to missing and invalid data resulting from the abnormal operating condition of NO_x,SO₂ and PM.The concentration probability distribution characteristics of air pollutants emitted from the production lines were analyzed after screening out of the production lines that met the data validity conditions.Representative production lines were selected referred to the log-normal distribution of the daily average concentration-hourly cumulative frequency of the cement production line.The correlation between the daily average concentration and the hourly cumulative frequency of the production line was analyzed in 5 scenarios with different limitation levels.Furthermore,the ratio between the hourly and daily average the hourly concentration was calculated in each scenario.The above results provide a scientific basis for studying the hourly and daily average concentration limits.The results indicated that:（1）the percentages of screened cement production lines are 100%,94.3%and 97.4%for NO_x,SO₂ and PM respectively,in which correlation coefficients between hourly concentrations log value and cumulative frequency normal value was greater than or equal to 0.6.（2）as for NO_x,SO₂ and PM,there is a significant correlation between the hourly and daily average concentration limits,while there is no significant difference in the multiple relationship between curve fitting method and the variation factor ratio method;（3）in the condition of 90%of the production lines meeting the limit,the hourly concentration limit can be set as 1.5 times of the daily average concentration limit;in that of 95%of the production lines meeting the limit,the hourly concentration is limited 1.6 times of the daily average concentration limit;as for 99%of the production lines,the hourly concentration limit is formulated as 1.7times of the daily average concentration limit.Based on the statistical analysis of hourly concentration,the quantitative proportional relationship between hourly and daily average concentration limits can be determined by variation factor ratio method and curve fitting method,and the assessment of compliance with emission limits can be established based on CEMS data.Taking the demand of new ecological and environmental supervision and enterprise air pollutants emission control into consideration,the assessment of compliance with emission limits based on CEMS data can be established and integrated into the emission standard of air pollutants for cement industry.