The study documented in this report was initiated in order to conduct an energy assessment and to identify the relationship between combustion issues and emissions from cement kilns. A new suspension preheater/precalciner (NSP) rotary cement kiln at one cement manufacturing facility (referred to as Shui Ni 1 in this report) and a vertical shaft kiln (VSK) at another cement manufacturing facility (referred to as Shui Ni 2 in this report), which are both in Shandong Province, were selected to conduct the energy and emission assessments through collection of data. Based on analysis of the data collected during this assessment, several actions are suggested that could lead to reduction in coal use and reduction in emission of gaseous pollutants from the system.
Specific actions suggested for NSP rotary kiln at Shui Ni 1 Cement Plant are: 1. reduce excess air use in coal burners, 2. reduce air leakage in the system through control of pressure and/or eliminating openings or gaps through which air leaks into the system, and 3. use of improved insulation and refractory in the kiln. These measures, if fully implemented, would reduce net (actual use minus equivalent of power production) coal consumption from 119 kg/ton kg of clinker to 103 kg/ton of clinker or a reduction of 16 kg coal per ton of clinker production – a reduction of 13.4%. Using a coal cost of 400 RMB/ton of coal, 360 days/year operation, and 5000 tons/day (approximately 208 tons/hour) clinker production rate, potential savings would be 11.52 million RMB/year.
Specific actions suggested for VSK at Shui Ni 2 Cement Plant are: 1. Preheat nodules by using hot water and/or using waste heat. 2. Pre dry nodules using waste heat from exhaust gases or air used for cooling nodules. 3. Reburn CO-combustible gases and recover heat for use in the process or plant. 4. Reduce areas of air leaks to increase temperature of exhaust gas and use a heat exchanger to recover heat by recovering heat for nodule making process. 5. Control kiln pressure to avoid negative pressure at the clinker discharge level.