Kiln Energy Research Articles

A life cycle assessment of clinker and cement production in Ethiopia

Cement production is a major consumer of energy and the largest source of industrial CO2 emissions. This study aims to perform an environmental life cycle assessment of clinker and cement production in Ethiopia, using ReCiPe impact assessment method. Inventory data (material, energy, and transportation) is collected from seven major Ethiopian cement industries. The midpoint analysis identified nine hotspot environmental concerns: global warming, ozone formation (human health and terrestrial ecosystem), particulate matter formation, terrestrial (acidification and ecotoxicity), freshwater eutrophication, human carcinogenic toxicity, and fossil resource scarcity. Human health emerged as the most significantly affected endpoint damage category by the midpoint impacts. Among the process stages included in clinker system boundary, clinker production phase (kiln emissions) is a significant contributor to the total score of the hotspot impacts, ranging from 60.7% to 91.8%. The clinker system is responsible for over 81.03% of the overall environmental burden of cement. The sensitivity analysis reveals that a 5% change in kiln energy consumption and transportation burden could lead to a reduction in hotspot impacts ranging from 1.8% to 5%. To foster reliability of this study, uncertainty analysis is also conducted. Overall, the findings indicate the need to enhance environmental sustainability in Ethiopian cement production.

Decarbonizing the lime-based construction materials industry: A practical guide for cradle-to-gate life-cycle inventory

This paper presents an integral parametrized framework to calculate the life-cycle inventory (LCI) in lime-based construction materials manufacturing, utilized for implementing decarbonization strategies in the LCI. The calcination operation is identified as the main source of CO2 emissions, with 0.79 tCO2/t CaO being inevitable (65 % of total emissions). Kiln fuel combustion contributes up to 35 % to emissions. Decarbonization strategies are ranked as: carbon capture, carbon direct avoidance, and circular economy. Parallel Flow Regenerative Kilns result in 40 % lower energy consumption compared to Long Rotary Kilns. Substituting lignite with natural gas can reduce emissions by up to 17 %. Direct CO2 separation from calcite decomposition, coupled with thermal energy recovery, can capture 65 % of the CO2 emitted, reducing kiln energy consumption by 15 % and CO2 emissions from fuel combustion by 13 %. The high purity of captured CO2 offers potential for future use as a valuable by-product. Supplementary raw materials in lime-based binder production have limited effects on CO2 emissions due to unavoidable emissions from calcite decomposition. The proposed process-oriented parametric methodology empowers Life Cycle Assessment practitioners, reducing reliance on generic databases for rigorous and transparent inventory calculations.

Energetic assessment of a precalcining rotary kiln in a cement plant using process simulator and neural networks

Cement production has been increasing rapidly leading to energy consumption, with serious cost implications and environmental challenges. Energy efficiency is a key component required to maintain the cement company’s environmental strategy. In this study, Aspen Plus process model and neural networks are used to assess the energetic efficiency of a precalcining rotary kiln in a cement production process. Aspen Plus process simulator estimated energy efficiency at 61.30 % using the first law of thermodynamic. Further, for the ANN model, kiln feed, kiln gas, calciner gas, clinker cooling air, and primary air were the operation parameters inputs. ANN model is validated and demonstrated it is capable of predicting cement rotary kiln energy efficiency accurately with a correlation coefficient (R2) of 0.991. In conclusion, the Bootstrap aggregated neural network (BANN) was used to search the optimal operational parameters in achieving the lowest mean square error (MSE) of the energy efficiency. The MSE for training, testing, and validation data sets were 3.64 × 10-5, 3.70 × 10-5, and 5.00 × 10-5 for in the estimation of rotary kiln system energy efficiency. To achieve this optimal condition of 61.5 % energy efficiency, the optimal parameters as determined by ANN (BANN) were kiln feed of 205050 kg/hr, kiln fuel gas of 2821 kg/hr, calciner fuel gas of 5648 kg/hr, clinker cooling air of 247463 kg/hr and primary air of 7309 kg/hr. Consequently, it is recommended that ANN should be combined with Bootstrap aggregated neural network (BANN) for effective prediction and monitoring of energy efficiency for precalcining rotary kiln system.

Beyond the energy balance: Exergy analysis of an industrial roller kiln firing porcelain tiles

The ceramic tile manufacturing process consumes large amounts of energy, mainly in the firing stage. Firing usually takes place in natural gas-fuelled continuous roller kilns, the most widely used tile firing facilities worldwide, which typically exhibit low energy efficiency (generally 5 to 20%). This paper investigates the application of energy and exergy balances to an industrial roller kiln firing porcelain tiles in order to identify the most critical parameters affecting kiln energy efficiency and propose ways of improving kiln energy performance. The experimental kiln measurements and thermodynamic calculations confirmed the kiln’s low energy performance (15%). Exergy analysis showed that 83% of the total exergy input into the kiln was destroyed, only 10% of the exergy input being kept in the physico-chemical transformations of the ceramic tile composition. The main sources of irreversibilities: natural gas combustion, heat transfer in the fired tile cooling process, and heat transfer through the kiln surfaces, were identified and quantified. The study shows that waste heat (over 61%) recovery could be expected to significantly increase kiln energy performance. Finally, further measures are proposed for optimising kiln energy efficiency.

MODEL TO ASSESS ENERGY CONSUMPTION IN INDUSTRIAL LUMBER KILNS

In this work, a kiln energy model was developed with the main objective of assessing energy consumption in industrial lumber kilns. The model simulates kiln energy consumption on the basis of a simplifi ed description of kiln technologies, energy systems and lumber characteristics, and it requires a minimum set of empirical parameters that are calibrated in practice. In this study, the model calibration was performed for a laboratory scale conventional kiln and three experimental drying runs of 50 mm thick spruce-pine lumber. The results of this study illustrate how the kiln energy model is calibrated, compares experimental and simulated MC, energy and water consumption, and describes how the model simulates different components of energy consumption that can be used to evaluate potential energy saving strategies.

Mill study on improving lime kiln efficiency

Optimization of the lime kiln requires an examination of the entire lime cycle. To increase the energy efficiency of the lime kiln, all auxiliary unit operations must function properly. It is also imperative that the lime and liquor in the system is of acceptable quality. We detail a kiln energy efficiency study performed by MWV Corp.’s Covington, VA, USA, mill. From a recausticizing standpoint, lime quality is much easier to control than liquor quality because liquor passes through many operations that are not under the lime kiln operator’s control. Recausticizing is a fairly closed cyclical process where lime is concerned, so saturation of impurities to the point of operational issues must be considered. Specific cycle performance indicators (e.g., lime mud solids entering the kiln) must be viewed from a perspective that does not exclude their potential impact. To get a true picture of the cost of operating the lime cycle, all inputs must be considered. The four main inputs are power (electrical and fuel), fresh lime, caustic, and water.

Opportunities to Reduce Energy Consumption in Softwood Lumber Drying

While a few years ago the cost and availability of energy was not an important issue for the Canadian lumber industry, this situation has recently changed. Today, companies that have operated trouble-free for many years using the same technologies and practices may now have to adapt to the rising cost of fossil fuels and concerns about greenhouse gas emissions. This article addresses this problem for the particular case of the softwood lumber industry. The study describes the most important sources of energy losses in conventional drying and proposes a number of strategies and technologies to reduce kiln energy demand.

Impact of kiln losses on a dehumidifier drier

The performance of a heat pump dehumidifier kiln has been measured, and the kiln energy balance assessed, during commercial-scale operation. Test data is presented for four drying tests. The results show that the drying performance of the system is impaired by excessive air exchange between the environment and the kiln, and by losses due to heat conduction through the kiln envelope. The results illustrate the importance of the integrity of the kiln structure for both the system drying speed and its energy efficiency.