The Feasibility of Using Alternative Fuels to Produce Portland Cement
Type of Degreethesis
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The production of cement involves a combination of numerous raw materials, strictly monitored system processes, and temperatures on the order of 1500 °C. Immense quantities of fuel are required for the production of cement. Traditionally, energy from fossil fuels was solely relied upon for the production of cement. Over the past few decades, concerns of sustainability and environmental impact from the utilization of fossil fuels have influenced the research of and implementation of alternative fuel sources. In this study, construction and demolition waste, woodchips, and soybean seeds were used as alternative fuels at a full-scale cement production facility. These fuels were co-fired with coal and waste plastics. The alternative fuels used in this trial accounted for 5 to 16 % of the total energy consumed during the pyroprocess. The construction and demolition waste and the woodchips possessed roughly half the energy value of the coal. The soybean seeds, however, were within 20 % of the coal’s heating value. Throughout each alternative fuel trial, samples of all process inputs and outputs were collected. Emissions were also monitored using a continuous emission monitoring system (CEMS). The monitored emissions included NOx, SO2, VOC, and CO. The alternative fuels used in this study were found to have minimal impact on the overall emission levels. Chemical analyses of all materials in each trial burn were conducted and the performance of each trial burn’s cement was thoroughly tested. Statistical analysis was performed on each trial burn’s clinker to compare the trial mean to the baseline mean. The majority of the trial burn’s clinker parameters had means that were significantly different from the baseline’s mean. These differences could be attributed to changes in the conditions at the cement plant between burns. The statistical differences found, however, did not translate into substantial differences in the cement performance. The construction and demolition waste trial burn had the greatest similarities to the baseline cement’s physical properties. The other trial burns also produced cement that had comparable mortar strengths compared to baseline results. The concrete produced from the variable feed and soybean seed trial burns’ cement possessed varying strengths compared to the baseline. The concrete strengths, however, were thought to be influenced by the chemical admixtures used in the mixture and therefore did not accurately represent characteristics of the trial cement. The cement plant successfully utilized the alternative fuels in this study. Production rates and cement quality were not compromised by the use of alternative fuels. Given the local availability of the fuel sources and compatibility with a cement facility’s operations, construction and demolition waste, woodchips, and soybeans are viable alternative fuel options for portland cement production.