Energy Audit And Integration Of Waste Heat Recovery System: A Case Of Dire Dawa National Cement

Abstract

A Cement plant is an energy intensive industry both in terms of thermal and electrical energy and more than 40% of production cost is accounted for by the cost of energy. Ethiopian cement factories costs an energy of 50 to 60% of the total operational costs as contrast to global standards due to imported fossil fuel and have the problem of effective utilization of available energy within industries which affects directly the organization’s profitability. The aim of this study is to conduct thermal and electrical energy audit, identify potential areas for improvement, quantify the energy losses in the system and finally propose possible energy saving opportunities in Dire Dawa National cement factory with a kiln capacity of 3000 ton-clinker per day. The energy auditing was conducted based on data collection from site measurement of material and energy flows using Infrared temperature guns , thermocouples, Air flow meters , pitot tubes with different length ,XRF, combustion analyzers and RETScreen Expert software . In this plant, Coal is the main source of thermal energy due to generation about 96.97% of the total heat input energy of system that it used for the clinker production process. The findings revealed that around 50% of the total input energy was being lost through preheater exhaust gas (23%), cooler exhaust (13.04%), and kiln shell (14.02%) convection plus radiation. Various heat recovery methods were introduced and discussed to mitigate these losses, and it was estimated that approximately 6.63 MW of energy (equivalent to 11% of the total input energy) could be recovered using a steam Rankine cycle. Additionally, an electrical energy audit focused on the main equipment in the process unit. The audit showed that the Coal Mill and Cement Mills had achieved net energy savings compared to the baseline period. However, the Raw Mill and the Kiln exhibited a trend of energy wastage. Aligning the performance of these equipment with the baseline or best-performing historical period could result in savings of approximately 14.4 million birr. Furthermore, the study highlighted a substantial production loss of 229,370 tons of cement over a four- year period, which equated to an estimated annual loss of 430,068,750 ETB. The findings from this study provide valuable insights into the energy performance of the Dire Dawa National Cement factory and offer recommendations for energy efficiency improvements. Implementing the proposed energy- saving measures has the potential to significantly reduce energy costs, increase profitability, and enhance sustainability in the cement industry

A Cement Plant Is An Energy Intensive Industry Both In Terms Of Thermal And Electrical Energy And More Than 40% Of Production Cost Is Accounted For By The Cost Of Energy. Ethiopian Cement Factories Costs An Energy Of 50 To 60% Of The Total Operational Costs As Contrast To Global Standards Due To Imported Fossil Fuel And Have The Problem Of Effective Utilization Of Available Energy Within Industries Which Affects Directly The Organization?�?S Profitability. The Aim Of This Study Is To Conduct Thermal And Electrical Energy Audit, Identify Potential Areas For Improvement, Quantify The Energy Losses In The System And Finally Propose Possible Energy Saving Opportunities In Dire Dawa National Cement Factory With A Kiln Capacity Of 3000 Ton-Clinker Per Day. The Energy Auditing Was Conducted Based On Data Collection From Site Measurement Of Material And Energy Flows Using Infrared Temperature Guns , Thermocouples, Air Flow Meters , Pitot Tubes With Different Length ,Xrf, Combustion Analyzers And Retscreen ?Expert Software . In This Plant, Coal Is The Main Source Of Thermal Energy Due To Generation About 96.97% Of The Total Heat Input Energy Of System That It Used For The Clinker Production Process. The Findings Revealed That Around 50% Of The Total Input Energy Was Being Lost Through Preheater Exhaust Gas (23%), Cooler Exhaust (13.04%), And Kiln Shell (14.02%) Convection Plus Radiation. Various Heat Recovery Methods Were Introduced And Discussed To Mitigate These Losses, And It Was Estimated That Approximately 6.63 Mw Of Energy (Equivalent To 11% Of The Total Input Energy) Could Be Recovered Using A Steam Rankine Cycle. Additionally, An Electrical Energy Audit Focused On The Main Equipment In The Process Unit. The Audit Showed That The Coal Mill And Cement Mills Had Achieved Net Energy Savings Compared To The Baseline Period. However, The Raw Mill And The Kiln Exhibited A Trend Of Energy Wastage. Aligning The Performance Of These Equipment With The Baseline Or Best-Performing Historical Period Could Result In Savings Of Approximately 14.4 Million Birr .Furthermore, The Study Highlighted A Substantial Production Loss Of 229,370 Tons Of Cement Over A Four-Year Period, Which Equated To An Estimated Annual Loss Of 430,068,750 Etb. The Findings From This Study Provide Valuable Insights Into The Energy Performance Of The Dire Dawa National Cement Factory And Offer Recommendations For Energy Efficiency Improvements. Implementing The Proposed Energy-Saving Measures Has The Potential To Significantly Reduce Energy Costs, Increase Profitability, And Enhance Sustainability In The Cement Industry