Technical Analysis of Energy Saving and Emission Reducing in China's Cement Industry Based on LEAP Model

[Objective] The study aimed at evaluating the ability to save energy and reduce CO2 emission in China＇s cement industry. [Method] Based on long-term energy alternative planning system software （LEAP）, ＂LEAP of China＇s cement industry＂ model was established to simulate energy conservation and emission reduction in China＇s cement industry from 2010 to 2040 in different technologic situations. E ResultJ To save ener- gy and reduce CO2 emissions, new dry process kiln has priority over other technologies or measures, followed by equipment enlargement, mechani- cal shaft kiln, power generation system based on waste heat, as well as high-efficiency and energy-saving grinding technology, and new prepara- tion technology. If all the advanced technologies and measures are adopted, energy consumption and C02 emissions can be reduced by about 40.76% and 42.97% respectively. [ Condusion] LEAP of model is suitable for analyzing energy saving and emission reducing in China＇s cement industry and other industrial fields.

A review of low-carbon technologies and projects for the global cement industry

Carbon dioxide(CO_(2))emissions from the cement industry account for 26%of the total industrial emissions,and the need to develop low-carbon techniques within the cement industry is extremely urgent.Low-carbon projects and technologies for the cement industry in different regions and countries have been thoroughly reviewed in this manuscript,and the low-carbon development concept for each county has been analyzed.For developing countries such as China and India,energy saving and efficiency enhancement are currently the key points,while for developed countries and regions such as Europe,more efforts have been focused on carbon capture,utilization,and storage(CCUS).Global CCUS projects have been previously conducted,and the majority of CCUS projects are currently performed in Europe where major projects such as the CEMCAP,CLEANKER,and IEILAC projects represent the latest research progress in cement production technologies and low-carbon technologies for the global cement industry.The development of low-carbon cement technologies has changed from focusing on the end point to instead focusing on the source and process through the exploration of hydrogen and solar energies,and more disruptive and original technologies are expected to be developed,particularly in the cement industry in China.

Challenges against CO_(2) abatement strategies in cement industry: A review

Cement industry is an intensive source of fuel consumption and greenhouse gases(GHGs) emissions. This industry is responsible for 5% of GHGs emissions and is among the top industrial sources of carbon dioxide(CO_(2)) emissions. Therefore, CO_(2) emissions reduction from cement production process has been always an appealing subject for researches in universities and industry. Various efforts have been carried out to mitigate the huge mass of CO_(2) emissions from the cement industry. Although, majority of these strategies are technically viable, due to various barriers, the level of CO_(2) mitigation in cement industry is still not satisfactory. Among numerous researches on this topic, only a few have tried to answer why CO_(2) abatement strategies are not globally practiced yet. This work aims to highlight the challenges and barriers against widespread and effective implementation of CO_(2) mitigation strategies in the cement industry and to propose practical solutions to overcome such barriers.

Diffusion and adoption of environmentally sound technology in China cement industry

From rapid growth of cement industry in China there is serious pollution of powdered dust. After general analysis on factors influencing adoption of environmentally sound technology(EST) as well as economic benefit from adoption of dust removing technology and capital ability of cement firms to invest, the conclusion that the obstacles to EST in China cement sector are different from ones in other sectors was drawn. And then, hindrances to diffusion and adoption of EST in China cement were discussion by empirical study.

CO2 emissions from cement industry in China： A bottom-up estimation from factory to regional and national levels

Much attention is being given to estimating cement-related CO2 emissions in China. However, scant explicit and systematical exploration is being done on regional and national CO2 emission volumes. The aim of this work is therefore to provide an improved bottom-up spatial-integration system, relevant to CO2 emissions at factory level, to allow a more accurate estimation of the CO2 emissions from cement production. Based on this system, the sampling data of cement production lines were integrated as regional- and national-level information. The integration results showed that each ton of clinker produced 883 kg CO2, of which the process, fuel, and electricity emissions accounted for 58.70%, 35.97%, and 5.33%, respectively. The volume of CO2 emissions from clinker and cement production reached 1202 Mt and 1284 Mt, respectively, in 2013. A discrepancy was identified between the clinker emission factors relevant to the two main production processes （i.e., the new suspension preheating and pre-calcining kiln （NSP） and the vertical shaft kiln （VSK））, probably relevant to the energy efficiency of the two technologies. An analysis of the spatial characteristics indi- cated that the spatial distribution of the clinker emission factors mainly corresponded to that of the NSP process. The discrepancy of spatial pattern largely complied with the economic and population distribution pattern of China. The study could fill the knowledge gaps and provide role players with a useful spatial integration system that should facilitate the accurate estimation of carbon and corresponding regional mitigation strategies in China.

Optimization of Fuel In-Situ Reduction(FISR)Denitrification Technology for Cement Kiln using CFD Method

Nitrogen oxides(NO_(x))from cement industry have drawn more and more attention and the existing denitrification technologies can hardly meet the increasingly stringent emission requirements in China.In our previous work,fuel in-situ reduction(FISR)method was proposed to cut cement NO_(x)emission.With the pilot-scale precalciner in the previous experiment as objection,optimization of FISR method was conducted using CFD method.The results demonstrated that NO_(x)emission decreased by 69.86%after adopting FISR method.The effects of initial concentrations of NO and O_(2)in kiln gas,feeding location of the first-stage tertiary(tertiary air-I)and cement raw meal(CRM)were further investigated.With increasing initial NO concentration,NO_(x)emission increased linearly,while the reduction rate of NO in kiln gas maintained above 80%.When O_(2)content in kiln gas is more than 4%,oxygen would more significantly promote the formation of NO_(x)and inhibit the reduction of NO.The dimensionless locations of tertiary air-I and CRM were introduced.The simulation results showed that the optimal dimensionless locations are 0.6 and 1.6 for tertiary air-I and CRM,respectively.The outputs achieved in this study will provide a strong support for the practical application of FISR method in cement industry.

Experimental analysis on calcination and carbonation process in calcium looping for CO_(2) capture: study case of cement plants in Indonesia

Carbon dioxide(CO_(2))is the main contributor to greenhouse gases that affect global warming.The industrial sector is the third largest producer of CO_(2) and the cement industry is one of the industries that consistently produces the most significant CO_(2) emissions.The cement industry produces 5-8% of global CO_(2) emissions.Several methods for reducing specific CO_(2) emissions have been reported in the cement industry,including calcium looping,which uses the reversible reaction between calcination[calcium carbonate(CaCO_(3))decomposition]and carbonation[CO_(2) capture by calcium oxide(CaO)].This work investigates calcium looping employing limestone obtained directly from several cement factories in Indonesia to observe the carbon-absorption characteristics of limestone from different mining locations.The experiment was carried out using a tube furnace equipped with a controlled atmospheric condition that functions as a calciner and a carbonator.X-ray diffraction and scanning electron microscopy with energy-dispersive x-ray spec-troscopy characterization were conducted to analyse the changes in the experimental samples.The results demonstrated that the reactor configuration was capable of performing the calcination process,which converted CaCO_(3) to calcium hydroxide[Ca(OH)_(2)],as well as the carbonation process,which captured carbon and converted it back to CaCO_(3).Parametric analysis was performed on both reactions,including pressure,temperature,duration,particle size and reaction atmosphere.The results show that the limestone obtained from all sites can be used as the sorbents for the calcium-looping process with an average reactivity of 59.01%.Limestone from cement plants in various parts of Indonesia has the potential to be used as carbon sorbents in calcium-looping technology.With a similar CO_(2) concentration as the flue gas of 16.67%,the experimental results show that Bayah limestone has the maximum reactivity,as shown by the highest carbon-content addition of 12.15 wt% and has the highest CO_(2)-capture capability up to>75% per mole of Ca(OH)_(2) as a sorbent.Similar levels of the ability to capture CO_(2) per mole of Ca(OH)_(2) can be found in other limestones,ranging from 14.85% to 34.07%.The results show a promising performance of raw limestones from different mining sites,allowing further study and observation of the possibility of CO_(2) emission reduction in the sustainable cement-production process.

Spatial differences of exergy use of cement manufacturing industry in China based on extended exergy accounting method

Factory-level data from 23 provinces and some national statistical data in cement manufacturing industry and socio-economies in 2012 are used to analyze the spatial distribution of exergy use for China＇s cement manufacturing industry by the Extended Exergy Accounting method. This method takes full account of the inclusion of energy and raw material supply and other external factors （capital, labor and environment） into a comprehensive resource cost assessment. The extended exergy consumption and its intensity quantitatively at the provincial levels of cement production were calculated and then the agglomeration level of exergy use at the regional level was also evaluated. Based on this analysis, their spatial difference in size and efficiency of exergy use at the provincial level were identified. Moreover, their regional characteristics were revealed. Some important results could be drawn as follows. First, the invisible social cost accounted for 1/10 of the total exergy use in cement manufacturing industry, while the energy element shared about 9/10. Second, the gross distribution of exergy use in China＇s cement manufacturing industry was mainly concentrated in the eastern region like Anhui and Shandong provinces, and in the western region like Sichuan province. In terms of exergy use, the coal and electricity were the highest of energy costs in the eastern region, whereas the cost of capital, labor and external environmental factors highlighted the invisible social cost for cement production in the central and western regions to some extent. Third, the efficiency distribution of exergy use in China＇s cement manufacturing industry illustrated an incremental feature from west to east, especially for the energy, labor and capital efficiencies. An evaluation on the environmental efficiency indicated that provinces or regions like Tibet, Xinjiang, Inner Mongolia and Shanxi have undertaken much higher environmental costs. Fourth, the 23 provinces could be classified into eight groups by the Euclidean distance model using the gross and efficiency results of exergy use. Fifth, the high industry concentration degree is the main driving factor of exergy efficiency improvement for cement manufacturing industry in China.

Experimental Investigation of Cutting Nitrogen Oxides Emission from Cement Kilns using Coal Preheating Method

The large consumption of coal in cement industry leads to a significant nitrogen oxide(NO_(x))emission,which has caused severe atmospheric pollution due to the existing low-efficiency denitration technologies.In this research,a fuel pretreatment method on the concept of coal preheating was proposed to reduce NO_(x)emission from cement kilns.A special bench-scale experiment was designed to verify the feasibility of the proposed method.Experimental results showed that the proposed method could achieve high combustion efficiency,steady operation and low NO_(x)emission.The maximum reduction efficiency of primary NO in kiln gas reached 91.4%while the lowest NO_(x)emission was 145 mg/m^(3)(@10%O_2)during the experiment.The effects of key parameters on NO_(x)emission and primary NO_(x)reduction efficiency were comprehensively investigated.It was found that primary and secondary air ratios determined the oxygen content in the flue gas and the reaction temperature,which multiply affected the fuel-NO_(x)formation and activity of reductants.Increasing the length of the reducing zone could not only enhance the primary NO_(x)reduction efficiency,but also lower the combustion efficiency.In addition,cement raw material could greatly accelerate the formation of fuel-NO_(x)while its catalytic action on NO_(x)reduction was limited.

Recovery of waste heat in cement plants for the capture of CO2

Large amounts of energy are consumed during the manufacturing of cement especially during the calcination process which also emits large amounts of CO2. A large part of the energy used in the making of cement is released as waste heat. A process to capture CO2 by integrating the recovery and utilization of waste heat has been designed. Aspen Plus software was used to calculate the amount of waste heat and the efficiency of energy utilization. The data used in this study was based on a dry process cement plant with a 5-stage preheater and a precalciner with a cement output of 1 Mt/y. According to the calculations： 1） the generating capacity of the waste heat recovery system is 4.9MW. 2） The overall CO2 removal rate was as high as 78.5%. 3） The efficiency of energy utilization increased after the cement producing process was retrofitted with this integrated design.