Research Progress of Microwave Modification Technology for Underground Coal Seam

Coal is one of the major energy resources in China, accounting for approximately 70 % of primary energy consumption. Many environmental problems and human health risks arise during coal exploitation, utilization, and waste disposal, especially in the remote mountainous areas of western China (e.g., eastern Yunnan, western Guizhou and Hubei, and southern Shaanxi). In this paper, we report a thorough review of the environmental and human health impacts related to coal utilization in China. The abundance of the toxic trace elements such as F, As, Se, and Hg in Chinese coals is summarized. The environmental problems (i.e., water, soil, and air pollution) that are related to coal utilization are outlined. The provenance, distributions, typical symptoms, sources, and possible pathways of endemic fluorosis, arsenism, and selenosis due to improper coal usage (briquettes mixed with high-F clay, mineralized As-rich coal, and Se-rich stone coal) are discussed in detail. In 2010, 14.8, 1.9 million, and 16,000 Chinese people suffered from dental fluorosis, skeletal fluorosis, and arsenism, respectively. Finally, several suggestions are proposed for the prevention and treatment for endemic problems caused by coal utilization.

This manuscript developed two methodologies of mapping energy flows of coal utilization in the form of Sankey diagrams: one was energy allocation diagram without illustrating any energy losses and the other was energy efficiency diagram illustrating main energy losses. Based on the methodologies, energy flow diagrams of China's coal utilization in the year 2005 and 2010 were presented. The two diagrams divided coal utilization into four stages from raw coal supply, by coal products supply and coal conversion, to energy end-use. Comparing with previous studies, some technical details were further introduced into the mapping, including coal preparation and the distribution of end-use energy such as electricity, heat and coke etc. Based on the results, the main characteristics of coal utilization in China and its main changes from 2005 to 2010 were discussed.

General equilibrium analysis of energy-saving and lowcarbonized development for coal utilization in China

This study analyzes the ecological effects of energy efficiency improvement for coal utilization during urbanization in China by a hybrid computable general equilibrium model. Firstly, the impacts of energy efficiency and industrial technology upgrading on total coal consumption and coal consumption intensity during the period from 2002 to 2030 are examined. Then the ecological benefits of energy efficiency related technology progress for coal utilization are also estimated. Simulation results show that resource input saving has absolutely more ecological benefits than emissions reduction for energy efficiency improvement of coal utilization in China.

The Jartai Pass site is a Late Bronze Age (3600–3000cal. a B.P.) settlement site in Nilka County, Xinjiang, China, containing the world’s earliest coal-burning remains including coal and ash. To investigate possible sources of coal used at the Jartai Pass site, extractable polycyclic aromatic hydrocarbons (PAHs) of the coal remains and coals around the site were analyzed. The concentrations of total PAHs (∑PAHs), 16 US Environmental Protection Agency prioritized PAHs (∑16PAHs), and alkylated PAHs (∑aPAHs) in 14 coal remains samples ranged from 1680–8579, 1090–4193, and 180–4066 ng/g, respectively. Four samples had higher PAH concentrations than the other 10 samples and were dominated by parent 4–6-ring PAHs and alkylated 2–3-ring PAHs. The other 10 samples were dominated by parent 2–3-ring PAHs, indicating different sources for the coal remains at the site. Total PAH concentrations in six coal samples around the site ranged from 2858–21582 ng/g. Three raw coal samples from mines were dominated by parent 2–3-ring PAHs, and the other three outcrop coals were dominated by parent 4–6-ring PAHs and alkylated 2–3-ring PAHs, revealing a significant difference in the PAH composition between raw coal and weathered outcrop coal. Based on the regional coalfield geology and development history of coal utilization in China, we suggest that the coals used at Jartai Pass site were from outcrop coal seams. The four high-PAH coal remains might have been from the coal line on the bank of the Kashgar River. Considering the amount used at the site over a long period, we speculate that the remaining coal may have been from the subsurface layer of the outcrop coal seam, indicating variation in mining depth. This study provides a basis for understanding coal remains unearthed at an archeological site in northwestern China and early coal utilization by humans.

The supercritical circulating fluidized bed (CFB) boiler, which combines the advantages of CFB combustion with low cost emission control and supercritical steam cycle with high efficiency of coal energy, is believed to be the future of CFB combustion technology. It is also of greatest importance for low rank coal utilization in China. Different from the supercritical pulverized coal boiler that has been developed more than 50 years, the supercritical CFB boiler is still a new one which requires further investigation.Without any precedentor engineering reference, Chinese researchers have conducted fundamental research, development, design of the supercritical CFB boilers independently. The design theory and key technology for supercritical CFB boiler were proposed. Key components and novel structures were invented. The first 600 MWe supercritical CFB boiler and its auxiliaries were successfully developed and demonstrated in Baima Power Plant, Shenhua Group as well as the simulator, control technology, installation technology, commissioning technology, system integration and operation technology. Compared with the 460 MWe supercritical CFB in Poland, developed in the same period and the only other supercritical one of commercial running in the word beside Baima, the 600 MWe one in Baima has a better performance. Besides, supercritical CFB boilers of 350 MWe have been developed and widely commercialized in China. In this paper, the updated progress of 660 MWe ultra-supercritical CFB boilers under development is introduced.

This paper analyzes the status quo in China regarding carbon emissions, and discusses challenges facing coal utilization in China. It concludes that the development of clean coal technology is an important means to realize low-carbon emissions in China. Using scenario analysis methodology, this paper presents quantitative analysis of the potential of clean coal technologies for carbon emission reductions in 2015 and 2020. The analysis indicates that high-efficiency combustion in industrial boilers and clean, highly efficient coal-fired power generation should serve as important factors for carbon emission reductions before 2020.

Development of coal dry beneficiation with air-dense medium fluidized bed in china

Coal is the primary energy source in China, widely used in energy production, industrial processes, and chemical engineering. Due to the complexity and diversity of coal quality, there is an urgent need for new technologies to achieve rapid and accurate detection and analysis of coal, aiming to improve coal resource utilization and reduce pollutant emissions. This study proposes a rapid quantitative analysis of coal using laser-induced breakdown spectroscopy combined with the random forest algorithm. Firstly, a Q-switched Nd: YAG laser at 1064nm was employed to ablate coal samples, generating plasma, and spectral data were collected using a spectrometer. Secondly, the study explores the impact of different parameters in the preprocessing method (wavelet transform) on the predictive performance of the random forest model. It identifies elements related to coal ash content and calorific value along with their spectral information. Subsequently, to further validate the predictive performance of the model, a comparison is made with models established using support vector machine, artificial neural network, and partial least squares. Finally, under optimal parameters for spectral information preprocessing (wavelet transform with Db4 as the base function and 3 decomposition levels), a model combining wavelet transform with Random Forest is established to predict and analyze the ash content and calorific value of coal. The results demonstrate that the Wavelet Transform-Random Forest model exhibits excellent predictive performance (coal ash content: R2 = 0.9470, RMSECV = 4.8594, RMSEP = 4.8450; coal calorific value: R2 = 0.9485, RMSECV = 1.5996, RMSEP = 1.5949). Therefore, laser-induced breakdown spectroscopy combined with the random forest algorithm is an effective method for rapid and accurate detection and analysis of coal. The predicted coal composition values show high accuracy, providing insights and methods for coal composition monitoring and analysis.

Coal is the primary energy source in China, and coal pyrolysis is considered an essential and efficient method for clean coal utilization. Three high arsenic coals collected from the southwestern Guizhou province of China were chosen in this study. Low-temperature ashing plus X-ray diffraction analysis (XRD) was used to identify the minerals in coals. The three coals were pyrolyzed in a tube furnace in an N2 atmosphere at 950 °C, 1200 °C, and 1400 °C, respectively. Environment scanning electron microscope (ESEM), XRD, X-ray fluorescence analysis (XRF), and inductively coupled plasma-mass spectrometry (ICP-MS) were adopted to determine the morphology, mineral compositions, and element compositions and arsenic contents of the coal pyrolysis ashes, respectively. It can be found that minerals in coal are mainly composed of quartz, pyrite, muscovite, and rutile. The minerals in the ashes generated from coal pyrolysis mainly contain quartz, dehydroxylated muscovite, iron oxide minerals, mullite, and silicon nitride. Oldhamite and gupeite exist at 950 °C and 1400 °C, respectively. The morphologies of oldhamite and gupeite at these temperatures are irregular block-shaped particles and irregular spherical particles, respectively. The mineralogical transformations in the process of coal pyrolysis affect coal utilization. The arsenic release rate is higher than 87% during pyrolysis at 1400 °C. The arsenic in organic matter is more able to be volatilized than mineral components. The retention time can slightly influence the arsenic release rate, and the influence of temperature is much more significant than the influence of retention time. The understanding of mineral evolution and arsenic environmental emission is helpful for the safety of high-arsenic coal pyrolysis.

The systematic review of Hosgood et al. published in this issue of the IJE, provides strong and sobering evidence about the price several hundred million people, mostly in Asia, pay for cooking or heating with coal using unvented stoves: a 2to 5-fold increased risk of developing lung cancer. The focus on geographic differences in the risks highlight that some areas in China are particularly strongly affected; be it due to different compositions of coal or habits and exposure patterns. The majority of the 25 studies come from China where the use of coal remains highly prevalent. Primary energy sources in China— the world’s biggest emitter of CO2—are strongly dominated by coal (470%). Lung cancer is just the tip of the iceberg of the adverse effects of indoor coal (and biomass) combustion. Lung cancer and chronic respiratory diseases, in particular chronic obstructive pulmonary disease (COPD), not only cluster among smokers, but also among those exposed to indoor air pollution due to coal or biomass combustion. Due to its chronic long-term nature, the morbidity burden related to COPD largely exceeds that due to lung cancer although mortality rates are rather similar for both diseases. The two diseases not only share pathological pathways, but COPD increases the risk of developing lung cancer four to five times. A previous cohort study from China showed that the lung cancer risk due to indoor coal combustion was even larger than the risk related to tobacco smoking: women with a history of 440 years of cooking had a 43-fold lung cancer incidence compared with those cooking <20 years, while men with 440 years smoking history had a 50% higher lung cancer incidence compared with those with <20 years of smoking. The question arises how to abate this entirely preventable burden of morbidity and mortality caused by indoor coal combustion. As shown in the above mentioned retrospective cohort study, stove improvement programmes in the rural Xuanwei region of China effectively cut lung cancer incidence by half. The intervention in this cohort study consisted in the change from smoky coal fires to stoves with chimneys. While this is promising, the approach falls short in embracing the problem in a more holistic manner. Two issues are of particular relevance. First, chimneys simply transport the combustionrelated pollution to the outdoor environment. While concentrations of health-relevant toxicants are certainly far more diluted outdoors than in poorly vented rooms, outdoor air pollution remains an environmental hazard shared among the entire population, day and night. Ambient air pollution contributes to a range of health problems including lung cancer. In fact, the impact of the indoor coal combustion is even underestimated in the studies reviewed by Hosgood et al., as cancer rates due to coal-related outdoor pollution (from indoor origin) contribute to the ‘background rates’ of lung cancer, thus diluting the relative risks due to indoor combustion of coal. Depending on local conditions and topography, indoor combustion can indeed become the dominant cause of outdoor air pollution. This is exemplified in the Mongolian capital Ulaan-Baatar, where poorquality stoves and boilers fuelled by coal and wood have become the single most important cause of a permanent ‘outdoor air quality crisis’, with daily mean particulate matter concentrations regularly exceeding 1000 mg/m. Secondly, coal ranks very high both in terms of equivalent CO2 emissions (per energy content) and of air pollution-related health effects. From a climate change perspective, coal combustion—indoors as well as in power plants or industries—remains a main problem and challenge. Most attractive are policy decisions that promote win–win situations in both abating climate change and improving the environment (air quality in this case) to maximize the public-health benefits. As shown in a comparative risk assessment scenario conducted for India, replacing 150 million combustionbased stoves with electric ones could avoid 12 500 disability-adjusted life years (DALYs) per million person-years while saving some 0.2 Mt of CO2 Published by Oxford University Press on behalf of the International Epidemiological Association

The sustainable development-oriented development and utilization of renewable energy industry——A comprehensive analysis of MCDM methods

Recent developments in coal mine methane extraction and utilization in China: A review

The total coal consumption in China is on the rise. The characteristics of CO2 and SO2 emissions in the whole process of coal processing and utilization in China are worthy of study. Based on the five links of the whole process of coal production and utilization, including coal production, raw coal processing, logistics and transportation, conversion and utilization and resource utilization, this paper summarized and analyzed the energy consumption and pollutant emission sources of these five links, combined with the US Environmental Protection Agency’s AP-42 method and IPCC method, to calculate total pollutant discharge and emission factors, where the emission factors were corrected by conversion efficiency. At the same time, uncertainty analysis is performed about CO2 and SO2 emissions. The results showed that CO2 emissions were 3.657 billion tons, and emission reductions were 61 million tons, and SO2 emissions were 4,844,500 tons, and emission reductions were 10.3595 million tons in 2015.

New progress in the processing and efficient utilization of coal