Zuoren Nie

Bio: Zuoren Nie is an academic researcher from Beijing University of Technology. The author has contributed to research in topics: Portland cement & Cement. The author has an hindex of 4, co-authored 9 publications receiving 150 citations.

Environmental impact analysis of blast furnace slag applied to ordinary Portland cement production

Abstract: This study was conducted based on the ISO 14040/14044 standards to analyze the environmental impact caused by blast furnace slag utilization for ordinary Portland cement production in typical plants in Beijing. In addition, sensitivity analysis of resource consumption, transport distance, the allocation methods and life cycle impact assessment model were discussed in detail. The results showed that global warming potential and acidification potential were the most significant environmental impacts resulted by slag-based cement production, accounting for 58.5% and 21.7% of the total environmental impact, respectively. Moreover, the cement production and energy generation phases accounted for 66.6% and 29.6% of total environmental loads of slag-based cement from cradle to gate, respectively. Sensitivity analysis showed that the comprehensive environmental impact of slag-based cement was sensitive to the consumption of limestone and energy, as well as the allocation methods and life cycle impact assessment model; but was insensitive to the consumption and transport distance of blast furnace slag. Compared with traditional Portland cement, except for the approximately 9% increase of human toxicity potential, the other impacts of slag-based cement decreased to a certain extent. In particular, abiotic depletion potential and land use potential significantly reduced by 72% and 41%, respectively. Therefore, producing cement with blast furnace slag would slightly increase electricity consumption, but significantly improve the benefits of land resource and materials conservation and significantly decrease the comprehensive environmental impact of cement.

The LCA of portland cement production in China

Abstract: Cement production is associated with a considerable environmental load, which needs to be fully understood before effective measures can be taken. The existing literature did not give detailed life cycle assessment (LCA) study of China and had limited potential for investigating how best available techniques (BATs) would provide a maximum benefit when they are applied in China. Japan was selected as a good example to achieve better environmental performance of cement production. We identified potentials for reducing emissions and saving energy and natural resources in Chinese cement industry through the comparative analysis. This paper follows the principal of Life Cycle Assessment and International Reference Life Cycle Data System (ILCD). The functional units are “1 t of portland cement” and with 42.5 MPa of strength grade. The input (limestone, sandstone, ferrous tailings, coal, and electricity) and output (CO2 from limestone decomposition and coal combustion, NOx, PM, and SO2) of cement manufacturing were calculated by use of on-site measurements, calculation by estimated coefficients, and derivation by mass and heat balance principle. The direct (cement manufacturing) and indirect (electricity production) LCI are added to be total LCI results (cement production). The impact categories of global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), photochemical oxidant formation potential (POCP), and human toxicity potential (HTP) are used to calculate environmental impact. Only in GWP of cement manufacturing China has advantage. Japanese cement industry shows remarkable superiorities in the environmental impacts of AP, POCP, HTP, and EP due to advanced technologies. SO2 emissions make the corresponding AP and HTP. PM emissions result in part of HTP. The NOx emissions are the major contributors of POCP, AP, EP, and HTP in China. China emits fewer CO2 emissions (2.09 %) in cement manufacturing than Japan but finally makes higher total GWP than Japan due to more GWP of electricity generation in power stations. The waste heat recovery technology can save electricity but bring more coal use and CO2 emissions. The alternative fuel and raw materials usage and denitration and de-dust technologies can relieve the environmental load. Using the functional unit with the strength grade, the life cycle impact assessment (LCIA) results are affected. LCA study allows a clear understanding from the view of total environmental impact rather than by the gross domestic product (GDP) unit from an economic development perspective. In an LCA study, the power generation should be considered in the life cycle of cement production.

Characterization and normalization factors of abiotic resource depletion for life cycle impact assessment in China

Abstract: The availability of resources for economic activities differs between regions, and the importance of the resources is consequently observed to be different within regions compared to a global scale. With the current situation in Chinese mining industry and its statistic characteristics, the characterization procedures of abiotic resource in life cycle impact assessment (LCIA) have demonstrated certain limitations in the Chinese materials industry. The aim of this paper is to propose new characterization and normalization factors for abiotic resource depletion categories such as metals and non-renewable energy resources in a Chinese context. The actual production of abiotic resources calculated by a modified model is compared to the reserve base in line with the new national standard to determine characterization factors in equivalence units, with antimony as the reference mineral. The normalization factors are based on the total base reserves of the most important minerals in China. A case study on primary magnesium production using the Pidgeon process is used to compare LCIA results for abiotic resource categories that are between current LCIA factors and the new Chinese factors. These factors not only reflect the importance of abiotic resource with respect to region-specific resource depletion, but also can compare with the global factors.

Exergy-based resource consumption analysis of cement clinker production using natural mineral and using calcium carbide sludge (CCS) as raw material in China

Abstract: The purposes of this study were to quantify the resource consumption intensity of cement clinker production using natural mineral in China and to determine the influence of the utilization of calcium carbide sludge (CCS) for cement clinker production on the resource-accounting result. Exergy-based resource accounting method was adopted by this study. Cumulative exergy demand (CExD) was used to characterize the resource consumption intensity of cement clinker production using natural mineral in China. Exergy-based characterization factors of land resource and CO2 emission were employed to determine the resource benefit brought by the substitution of CCS for natural limestone (land saving and CO2 reduction). The CExD value of cement clinker production using natural mineral as raw material in China is 5005 MJ/t, and the consumption of raw coal is the largest contributor to this result, accounting for approximately 81% of the CExD value. The phenomenon that coal consumption dominates the CExD result may be because, through combustion reactions, the chemical state of carbon contained in coal almost reaches equilibrium with its chemical dead state in terms of exergy and is deeply dissipated; in comparison, the major chemical compound contained in limestone, i.e., calcium oxide, is mostly transformed into cement clinker by the reactions occurred in the production system, instead of being consumed in a deeply dissipated way and emitted to the environment. The major disadvantage of using CCS for cement clinker production is the increase of coal consumption, i.e., 515 MJ/t cement clinker, and the major advantage of using CCS for cement clinker production is the resource benefit brought by CO2 reduction (the avoided biotic resource damage in ecosystem), i.e., 1160 MJ/t cement clinker. From the analysis on the influence of the substitution of CCS for limestone on the resource consumption intensity, we found that the resource consumption intensity of the production system using CCS is approximately 15.5% lower than that of the production system using natural mineral; however, if this resource benefit is neglected, the resource consumption intensity of the production system using CCS is approximately 7.6% higher than that of the production system using natural mineral. We suggest that establishing a theoretical bridge between the characterization models of biotic resource and abiotic resource will still be a significant research direction in the future, which is fundamental in objectively understanding and unifying the issues of emission reduction and resource saving.

On-line monitoring and controlling method for incomplete combustion carbides in cement production process

Abstract: The invention relates to an on-line monitoring and controlling method for incomplete combustion carbides in the cement production process, belonging to the field of cement production. The method is characterized by comprising the following steps of: installing a carbon dioxide sensor and measuring the actual discharge amount of CO2 in a time range T; calculating a critical value of the CO2 in thetime range T; initializing an on-line monitoring and controlling system, setting the delivered oxygen amount to be 0.5% of the air amount in the time range T if the incomplete combustion carbides arein a higher range, and increasing the amounts of secondary air and tertiary air until the actual discharge amount of the CO2 is equal to the critical value of the CO2 if the incomplete combustion carbides are less, wherein the error is not more than 1.0%. The invention provides calculation formulas of the critical value and the discharge reduction value of the CO2 and a method for controlling thecarbides generated by incomplete combustion. The method is also suitable for cement production lines utilizing acetylene sludge for replacing partial raw materials and has the advantages of environmental protection, resource and energy source saving, low investment and running cost and the like.

Hybrid life cycle assessment of greenhouse gas emissions from cement, concrete and geopolymer concrete in Australia

Abstract: Concrete is the second most used material after water and the production of cement is responsible for 5–8% of global carbon dioxide emissions. The development of low-carbon concretes is pursued worldwide to help the construction industry make its contribution to decarbonising the built environment and achieving carbon reduction targets agreed under the Paris Climate Agreement. However, there is uncertainty around the actual amount of greenhouse gas emissions that can be avoided by employing alternative types of concrete. This study quantifies the carbon footprint intensities of Australian cement and concrete production, including ordinary Portland cement, standard ordinary Portland cement concrete, blended cement-based concrete and geopolymer concrete production. For the first time, an input-output based hybrid life-cycle assessment method is used for these products. The main goal of this paper is therefore to make a methodological comparison between process-based and hybrid life cycle assessment using the Australian cement and concrete production as a case study. A comparison with published results from process-based life-cycle inventories as well as a decomposition of results into product categories is provided. The hybrid life cycle assessment resulted in higher greenhouse gas emissions for ordinary Portland cement and all types of concrete due to the methodology incorporating an economy-wide system boundary, which includes the emissions from upstream processes. For geopolymer concrete in particular, the results were also dependent on the method applied for allocating greenhouse gas emissions from fly ash and slag. The findings from this study are likely to inform the development of strategies and policies aimed at greenhouse gas reduction in the cement and concrete industries.

A review of microbial precipitation for sustainable construction

Abstract: Rapid urbanisation has accelerated consumption of concrete making it the most consumed artificial material. Present day concrete is one of the largest sources of anthropogenic greenhouse gas emission and is not sustainable. Microbial precipitation of CaCO3 is a promising way of emulating nature’s sustainable ways. This paper reviews current progress and potential of this technology. Prior research on the modes of application of the technology and consequent gains in strength and durability of construction materials has been summarised. Imperatives for a quantitative estimate of sustainability are identified. Progress necessary for industrial adoption of the technology has been discussed.

Environmental impacts, life cycle assessment and potential improvement measures for cement production: a literature review

Abstract: Cement constitutes one of the primary building materials. As cement manufacturing involves the use of large amounts of raw materials and energy, an issue that arises is the necessity to assess its environmental impact and analyze in which way the industry should proceed concerning best practices. Life Cycle Assessment (LCA) has frequently been used in case studies around the globe as an environmental impact assessing tool. The present literature review serves for: (i) describing the environmental impacts, (ii) clarifying the methodological approaches in LCA, and (iii) identifying the main alternatives to improve the environmental performance of cement production. Several available studies on the environmental performance of manufacture and use of cement products were reviewed. These studies identified improvement of energy efficiency, the use of alternative fuels, clinker substitution, and carbon capture and storage (CCS) as the main solutions for mitigating environmental impacts caused by cement production. The first three options have been thoroughly analyzed, applied, and have shown improvement through the years. CCS has a high improvement potential; however, it presents technical and economic barriers to its implementation.

Comparative LCA on using waste materials in the cement industry: A Hong Kong case study

Abstract: Cement is traditionally regarded as an energy and emission intensive construction material. The reduction of environmental impacts in the cement industry has gained increasing concern worldwide for environmental sustainability. As a resource-scarce city, cement production in Hong Kong is associated with high CO2 emissions, thus contributing significantly to the high environmental impacts in the construction industry. This study herein has been conducted to comprehensively assess the energy consumption and global warming potential impacts of different types of cement manufactured in Hong Kong using life cycle assessment (LCA) techniques. Two sustainable strategies for the reduction of energy consumption and greenhouse gases emission in the cement industry were then proposed. The LCA results showed that ordinary Portland cement production has high environmental impacts mainly due to the import of associated raw materials and burning of fossil fuel. The use of alternative material, such as fly ash would help to reduce the environmental impacts. Significant impacts reductions associated with cement production can be further achieved by strategies such as the use of glass powder from locally generated waste glass bottles as part of the raw materials, and the use of a bio-fuel produced from locally generated wood wastes as a co-fuel with coal. The assessment results indicated that about 12% of the total greenhouse gases emission and 15% of energy consumption can be reduced from the cement industry in Hong Kong by using waste materials to replace virgin materials (clinker/coal).

A comparative cradle-to-gate life cycle assessment of three concrete mix designs

Abstract: The concrete industry faces challenges to create concrete mix designs that reduce negative environmental impacts but also maintain high performance. This has led to ‘greener’ cementitious materials being developed which can decrease the use of traditional Portland cement (PC). This study intended to carry out a ‘cradle-to-gate’ life cycle assessment (LCA) on concrete mix designs containing different cementitious blends. The aim of this study was to obtain the overall environmental impact, with a particular focus on carbon dioxide (CO2) emissions of three concrete mix designs: CEM I (100 % PC content), CEM II/B-V (65 % PC content, 35 % Fly Ash (FA) content) and CEM III/B (30 % PC content, 70 % ground granulated blast furnace slag (GGBS) content). Evaluations of the three concrete mixes were performed using ‘SimaPro 8’ LCA software. A comparative cradle-to-gate LCA of these mixes has not currently been explored and could present a new insight into improving the environmental impact of concrete with the use of secondary materials. Recommendations from this work would help the industry make key decisions about concrete mix designs. Results show that Mix 2 (CEM II/B-V) and Mix 3 (CEM III/B) could potentially be taken forwards to improve their environmental impacts of concrete production. With respect to optimum mix design, it is strongly recommended that GGBS is selected as the addition of choice for reducing CO2 emissions. FA does still considerably improve sustainability when compared to PC, but this work proved that inclusion of GGBS environmentally optimises the mix design even further. Advantages of using GGBS include lower CO2 emissions, a substantial reduction of environmental impacts and an increased scope for sustainability due to the higher PC replacement levels that are permitted for GGBS. Due to mix designs enabling a higher contribution of GGBS additions, it would also indicate an increased positive effect regarding waste scenarios. The main contribution of this work demonstrated that concrete can be produced without loss of performance whilst significantly reducing the negative environmental impacts incurred in its production. The results obtained from this work would help to define the available options for optimising concrete mix design. The only material variations in each mix were the different cementitious blends. So, by determining the best option, a platform to make recommendations can be established based upon cementitious materials.