Xian Zheng Gong

CO2 Emissions due to Cement Manufacture

With increasing concerns about global warming, and the cement plants emitting huge CO2, it is necessary to know how the CO2 emits and how much the CO2 emits due to cement manufacture in both direct and indirect ways. A precise method to calculate CO2 emissions including three processes was established in this paper and a case study was provided. From the case of LQDX plant, we can see the amount of CO2 emissions at the right level. The summary of CO2 emissions is consisted by emissions from raw materials, fuels and electricity. The direct CO2 emissions are 0.822 ton CO2 per ton clinker, and the total CO2 emissions are 0.657 ton CO2 per ton cement in this study. Therefore, the way that CO2 emissions due to cement manufacture was pictured and then measured. An approach provides a basic framework to identify various situations in different cement plants in China and other in the rest of the world. The framework would be useful in quantitatively evaluating CO2 emissions for government to know precisely CO2 emissions in cement plants.

Exergy-Based Model of the Depletion of Mineral Resources

The primary problem of eco-materials is how to judge whether a material is environmentally friendly or not, and the method of life cycle assessment is usually used to evaluate it. The depletion of mineral resources is a very important indicator of LCA, but its characterization is still filled with dispute. At present, the most commonly used method is CML, which is put forward by Leiden University, and its core idea is that using the ratio of exploitation amount and reserves of mineral resources as the degree of scarcity. Although being accepted by most of the scholars at work on LCA, CML doesn’t grasp the essence of the depletion of mineral resources. Recently, a new assessment method, injecting new ideas to the conventional life cycle assessment, combines exergy with LCA is arising, which can be used to solve some specific problems of LCA especially the depletion of mineral resources. In this paper, two results of elements’ exergy calculated by Rivero and Szargut respectively are compared, and the exergy of some natural minerals, which can be used in LCA and other minerals-related research, is calculated based on the data of Chinese mineral resources.

LCA Method of MSC and Low-NOx Burner Technology in Cement Manufacturing

LCA method was used to model the life cycle of cement manufacturing with multi-stage combustion and low-NOx Burner technology applied as its low-NOx system. The life cycle is from the coal and raw materials transportation, through the coal and raw meal grinding, to the clinker incineration, and finally the flue gas including NOx to the air atmosphere. The functional unit is 1 tonne clinker. Data for cement produced in MSC and LNB technology is analyzed. The data is collected from the real clinker production situation and the measurement is taken in 12 hours continuously.

A Research on Energy-Saving and Environmental Impacts of Primary Magnesium and Magnesium Alloy Production in China

China is the largest primary magnesium producer in the world, because of nearly 80% of the global market share. In the present paper, an approach of life cycle assessment (LCA) was applied to build an inventory of air emissions and to analyze the environmental impact of the global warming potential (GWP) and the acidification potential (AP) related to the production of AZ91D magnesium alloy. A summary of environmental impacts of primary magnesium and primary aluminum production with various studies was made to show the influence of uncertainties on the impacts. The results showed that the cumulative GWP and the acidification potential (AP) of AZ91D Mg-alloy are 33.4 t CO2 eq/t ingot and 139 kg SO2 eq/t ingot, with the range of 29.5-36.3 t CO2 eq/t ingot and 104-152 kg SO2 eq/t ingot, respectively. The GWP and AP of primary magnesium account for 90% and 77% of the cumulative environmental impact of AZ91D Mg-alloy. Under the grand background of advancing the development strategy of energy-saving and emission-reducing, China magnesium smelting and manufacture industry has made rapid progress in the structure optimization, energy efficiency improvement, and environment protection. The calculated data show that the improvement measures, e.g. reduction of dolomite consumption and energy consumption, in Chinese Pidgeon process led to 23% decrease of the GWP for the primary magnesium production in 2009 compared with 2005. The global warming reduction potential for 1 ton AZ91D alloy ingots produced in China was estimated of substituting HFC-134a for SF6 as a cover gas.

Life Cycle Assessment of Rock Wool Board and EPS Board

Although outer wall thermal insulation technology is an effective measure for building energy-saving, the production of thermal insulation materials causes serious impacts on environment. In the present investigation the resource, energy consumption and environmental emission of the two kinds of thermal insulation materials were analyzed, from the acquisition of raw materials to production process based on Life Cycle Assessment (LCA). The result show that life cycle energy consumption of rock wool board is 415MJ per functional unit, proximately twice of EPS board’s (220MJ). Overall, environmental impact indicators caused by rock wool board is more serious than EPS.

Multiple Imputation for Missing Data in Life Cycle Inventory

The major environmental loads of mineral separation process in China iron production (with missing data) are analyzed. And the inner relationship between these loads data is qualified and the missing data are imputed using a statistic method called multiple imputation (MI), aimed to improve the quality of LCA datasets and allow industry to easily conduct a highly reliable LCA. By using computer simulation, MI replaces each missing value with a set of plausible values which represent the uncertainty of the missing data. The multiply imputed datasets are then analyzed by the standard procedures for completing data and combining the results from these analyses. The result proves that MI Method is an effective and reasonable method to solve the problem of missing data and therefore can ensure the validity and reliability of LCA.

Materials Flows Analysis on the Beneficiation and Roasting Processes of a Typical Rare Earth Mineral

The aim of this paper is to explore material flow analysis, study the resource consumption and environmental impact of the production preparation process of typical rare earth materials. The results showed that in the beneficiation processes, producing one ton of rare earth concentrates (Rare Earth Oxide, REO50%) will also produces 27 tons of iron ore and 21 tons of tailings. The recovery of rare earths is only 16.8%. In roasting processes, roasting one ton (REO50%) of rare earth concentrates will emits 150 ~ 200Kg sulfuric acid mist, 500 ~ 600Kg sulfur dioxide, 30 ~ 40Kg fluoride, 30 ~ 50Kg smoke and1t (containing thorium) radioactive slag, and 1.2 tons of concentrated sulfuric acid should be used. The lower recoveries and large-scale of concentrated sulfuric acid used in roasting processes in rare earth industry are the main reasons lead to high pollution and high emissions.

Life Cycle Assessment of Heavy-Duty Truck for Highway Transport in China

The detailed life cycle assessment of heavy-duty truck for highway transport in China is conducted by Centre of National Material Life Cycle Assessment (CNMLCA). The input of energy and output of pollutants emissions are documented as the life cycle inventory (LCI). The life cycle impact assessment (LCIA) results calculated with the CML method show that the hotspot of environmental impacts from transport in China. The environmental benefits from implementations of European emissions standards in China for transport are also analyzed. The analysis shows that the acidification potential (AP) makes the most huge contribution to total environmental impact, up to 33.7%. As the second hotsopt, global warming potential (GWP) takes up 26.83% of total environmental impact. Photochemical oxidant formation potential (POCP) takes up 23.42% of total environmental impact, which is more or less the same comparing with the result of GWP. Eutrophication potential (EP) takes up 15.05% of total environmental impact. The last but not the least environmental impact category - human toxicity potential (HTP), only takes up 0.95% of total environmental impact. If the heavy metal and dioxin emissions are also considered, maybe the results will be changed and the HTP will take more in the whole environmental impact. It can be concluded that if we pay more attention on SO2 emissions especially NOx emissions reduction, the acidification and photochemical smog would be relieved a lot and the total environmental impact can be decreased a lot. More punishment on overload may be a good choice to reduce environmental load of heavy truck of highway transport in China.

Life Cycle Assessment of Steel Production

Based on life cycle assessment, analysis of energy consumption and other environment load by steel production in Chinese typical iron and steel industry was carried out. The process accounted for the most environment load was found by studying the different processes in steel production route. The results indicate that the most important process is blast furnace (BF) which is the major factor of CO2 and CO emissions, and contributes most to globe warming potential (GWP) and photochemical ozone creation potential (POCP).

Life Cycle Assessment of Ready-Mixed Concrete

Approximately 416.9 million m3 of concrete were used in China in buildings, roads and other constructions in 2009. This makes concrete one of the most common building materials on the market. While consuming large amounts of energy, concrete industry has also cause large burden on the environment due to the environmental emissions by the production of cement and the transport of materials. Therefore, more detailed quantitative studies are necessary to finally acknowledge its effects of energy and environment. The objective of this paper is to identify and quantify the energy consumption, and environmental emissions during all life-cycle phases of concrete in China by LCA.