Performance Evaluation of Low-Carbon and Clean Transformation of China’s Coal Economy

In China,the oversupply of coal occurred in 2009,and from that year onwards,China’s coal economy began a low-carbon and clean transformation.Evaluating transformation performance is the research goal of this paper.The data collection for this paper includes data on deep processing of Chinese coal products from 2009 to 2020,as well as data on asset structure evolution and financial performance of 34 listed companies in the Chinese coal mining.Entropy value method is used to calculate the entropy value of low-carbon transformation,and the regression analysis is used to study the performance of cleaner transformation,the conclusion is as follows:(1)From 2009 to 2020,in China’s total energy consumption,coal consumption accounted for 71.6%in 2009 and 56.8%in 2020,the goals set by the state have been achieved.(2)The national goal of reducing the proportion of coal consumption and reducing carbon emissions has forced the transformation of deep processing of coal products.The transformation of coal enterprises towards low-carbon and clean production has achieved remarkable results.(3)From 2009 to 2020,the non coal industry income of 34 listed companies in China’s coal mining industry increased by 8.21%annually.At the same time,the asset structure was adjusted,and nearly 80%of the asset structure evolution showed an orderly development trend.(4)The regression analysis results show that the entropy value of coal deep processing products and the entropy value of asset structure adjustment are significantly related to transformation performance.The paper proposes to summarize the successful experience of China’s coal energy economic transformation,lay a foundation for achieving the carbon peak and carbon neutral goals in the future,further increase the intensity of coal deep processing,increase the proportion of clean energy in total energy consumption,and strive to control asset operation towards the goal of increasing the proportion of non coal industry income.

Coal waste management practices in the USA:an overview

This paper provides an overview of coal waste management practices with two case studies and an estimate of management cost in 2010 US dollars.Processing of as-mined coal typically results in considerable amount of coarse and fine coal processing wastes because of in-seam and out-of-seam dilution mining.Processing plant clean coal recovery values run typically 50%-80%.Trace metals and sulfur may be present in waste materials that may result in leachate water with corrosive characteristics.Water discharges may require special measures such as liner and collection systems,and treatment to neutralize acid drainage and/or water quality for trace elements.The potential for variations in coal waste production and quality depends upon mining or processing,plus the long-term methods of waste placement.The changes in waste generation rates and engineering properties of the coal waste during the life of the facility must be considered.Safe,economical and environmentally acceptable management of coal waste involves consideration of geology,soil and rock mechanics,hydrology,hydraulics,geochemistry,soil science,agronomy and environmental sciences.These support all aspects of the regulatory environment including the design and construction of earth and rock embankments and dams,as well as a wide variety of waste disposal structures.Development of impoundments is critical and require considerations of typical water-impounding dams and additional requirements of coal waste disposal impoundments.The primary purpose of a coal waste disposal facility is to dispose of unusable waste materials from mining.However,at some sites coal waste impoundments serve to provide water storage capacity for processing and flood attenuation.

Modeling of fine coal flotation separation based on particle characteristics and hydrodynamic conditions

Flotation is a complex multifaceted process that is widely used for the separation of finely ground minerals. The theory of froth flotation is complex and is not completely understood. This fact has been brought many monitoring challenges in a coal processing plant. To solve those challenges, it is important to understand the effect of different parameters on the fine particle separation, and control flotation performance for a particular system. This study is going to indicate the effect of various parameters （particle Characteristics and hydrodynamic conditions） on coal flotation responses （flotation rate constant and recovery） by different modeling techniques. A comprehensive coal flotation database was prepared for the statistical and soft computing methods. Statistical factors were used for variable selections. Results were in a good agreement with recent theoretical flotation investigations. Computational models accurately can estimate flotation rate constant and coal recovery （correlation coefficient 0.85, and 0.99, respectively）. According to the results, it can be concluded that the soft computing models can overcome the complexity of process and be used as an expert system to control, and optimize parameters of coal flotation process.

Facultative-anaerobic microbial digestion of coal preparation waste and use of effluent solids to enhance plant growth in a sandy soil

Coal preparation solid waste,which is a major environmental issue for coal-producing areas in China,may be microbiologically digested and transformed into a product suitable as a soil amendment to increase soil organic matter content and prevent and enhance plant/crop growth.Coal preparation waste collected from a coal sorting plant in Inner Mongolia,China was digested in bioreactors inoculated with microbial enrichments prepared from activated sludge and cow manure.The effluent solids from the coal preparation waste bioreactors were analyzed for their suitability as organic soil amendments,which complied with China standards.Plant growth tests were conducted in sandy soil from a semi-arid region in Colorado,which was amended with the effluent solids.Kentucky bluegrass(Poa pratensis L.)and chives(Allium schoenoprasum)were used as the representative plants for the growth tests,where results indicated substantially higher yields of Kentucky bluegrass and chives for the sandy soils amended with the effluent solids when compared to a commercial organic fertilizer.The number and average length of Kentucky bluegrass shoots were 10 and 5.1 times higher,respectively,in soils amended with the effluent solids.Similarly,the number and average length of chives shoots were 10 and 1.7 times higher,respectively,in soils amended with the effluent solids.Overall,the microbial digestion of coal preparation waste for application as an organic soil amendment is a viable alternative and beneficial use of coal preparation solid waste.

Vibrated fluidized bed air classification of moist raw coal

Vibrated fluidized bed air classification is completely different from traditional screening in principle. It extracts fine coal from moist raw coal by entrainment of an ascending airflow in a vibrated fluidized bed. Pilot tests showed that air classification efficiencies varied from 74.85% to 93.84% at cut-size 6, 4, 3, 2, 1, and 0.5 mm when free moisture of coal is in the range of 1.7% to 9.5%, and ash contents of fine coal products were 2%～3% lower than those of the same size fractions in feed, and 4%～10% lower than those of feeds for most cases because of the density differences between coal and waste, which is beneficial to producing lower ash fine coal from raw coal as fuel of blast furnaces or pulverized coal firing boilers. A commercial unit of 100 t/h has been in smooth operation, and several 300～400 t/h units are in plan or construction.

Batch methanogenic fermentation experiments of wastewater from a brown coal low-temperature coke plant

Coke plant effluents with high contents of organic compounds are mainly treated by biological aerobic fermentation after physical pre-treatment. In this study, a brown coal condensate wastewater from a low temperature coking process was fermented under methanogenic conditions in discontinuous experiments. By this fermentation, acetate, propionate, and the main polyphenolic compounds （catechol, resorcinol and hydroquinone） were degraded to a level below the detection limit. The COD was reduced by 72% with a residual concentration of 2.1 g/L. This anaerobic fermented wastewater had a residual BOD5 of 0.66 g/L and 2.2 L CH4 were formed per litre of wastewater. An abiotic pre-treatment for this wastewater with air had a negative effect on the COD reduction and decrease of colour on the methanogenic fermentation due to the autoxidation of polyphenolic compounds to humic-like compounds. This study showed that methanogenic fermentations in the treatment sequence of brown coal coking wastewaters could reduce energy consumption for aeration in further treatment processes and had the potential for a better effluent quality due to a less formation of recalcitrant humic-like compounds.

Negative-pressure pneumatic separator:a new solution for hard-coal beneficiation

Hard coal is an important source of energy worldwide.Owing to the imperfections of excavation technology,most run-of-mine coals must be processed before they can be utilised as fuel.In this study,tests on the dry separation process were performed with numerous different raw hard coal and coal waste material samples,using a newly designed and constructed negative-pressure pneumatic separator(NPPS).The experiments revealed the effects of the feed-material properties and material processing conditions.These experiments were preceded by additional tests for evaluating the influence of each device operating parameter on the process,to determine the optimal method of supplying the feed material.The calorific value of the processed materials was improved by 5%–40%,while a minimal output yield of products(60%–70%)was maintained.The trials indicated that in coal material processing,the developed NPPS can be used for not only raw coal enrichment but also coal recovery from materials stored at coal-waste dumps.The main advantages of the device are its mobility,low material processing cost,and lack of water consumption during operation.

Mechanism research of gas and coal dust explosion

Combined with the experimental results from the large tunnel of the ChongqingResearch Institute,the mechanism of gas and coal dust explosion was studied.Someconcepts about gas and coal dust explosion were introduced such as the form conditionand influential factors.Gas and coal dust explosion propagation was researched and thelifting process of coal dust was simulated.When an explosion occurred due to great mixtureof gas and air,the maximum explosion pressure appeared in the neighborhood of theexplosion source point.Before it propagated to the tunnel of the deposited coal dust,themaximum explosion pressure appeared to be in declining trend.Part of the energy waslost in the process of raising the deposited coal dust through a shock wave,so the maximumexplosion pressure was smallest on the foreside of the deposited coal dust sector.On the deposited coal dust sector,the explosion pressure rapidly increased and droppedoff after achieving the largest peak value.Because of coal dust participation in the explosion,the flame velocity rose rapidly on the deposited coal dust and achieved a basic stablevalue;coal dust was ignited to explode by initial laminar flame,and the laminar flametransformed into turbulent flame.The turbulence transformed the flame fold into a funnelshape and the shock wave interacted with the flame,so the combustion rate rose and thepressure wave was further enhanced.The regeneration mechanism between the flamecombustion rate and the aerodynamic flowing structure achieved the final critical state forforming the detonation.

The influence of intensity and properties of tectonic stress on the process of coalification

Through the research on stress metamorphism character of the II1 coal seam in Ludian gliding structure, the stress effecting factors of metamorphism and hydrocarbon generation process of tectonic coal were studied. It is shown that different tectonic stress has different coal evolution effects. Compared with tensional stress, compressive stress, which has apparent anisotropic characteristics, has greater stimulative effect against the increase of coal metamorphic degree, the abscission of functional group and side chains of basic structural unit, and the formation of gas primarily composed of methane.

HIGH-RESOLUTION SEQUENCE DIVISION AND TRANSGRESSIVE EVENTS COAL FORMATIONIN SOUTHEASTERN NORTH CHINA EPICONTINENTAL BASIN

The sea level changes in the Paleozoic epicontinental basin were of high frequency and the transgressive events were episodic.This kind of sea level changes controlled both the basin filling and the coal accumulation within the basin.Coal accumulation in the transgressive process is one of the typical features of the North China epicontinental basin.High resolution sequence analysis to the Permo carboniferous coal series based on the core observation indicates that the epicontintental coal bearing succession can be divided into 1 tectonic sequence (the original type of basin filling), 3 supersequences, 12 third order sequences and about 48 parasequences.The third order sequences are of dual configuration sequences that are composed of transgressive systems tract in the lower part and highstand systems tract in the upper part.The transgressive systems tracts are relatively thin in thickness and have fewer parasequences (commonly 1 to 2), while the highstand systems tracts are thick, generally consist of several parasequences.

Construction of a macromolecular structural model of Chinese lignite and analysis of its low-temperature oxidation behavior

The aim of this paper is to analyze the change in the active structure of lignite during the process of lowtemperature oxidation by constructing a molecular structure model for lignite. Using quantum computation combined with experimental results of proximate analysis, ultimate analysis, Fourier transform infrared spectroscopy(FTIR) and X-ray photoelectron spectroscopy(XPS), a structural model for the large molecular structure was constructed. By analyzing the bond lengths in the model molecule, the evolution law for the active structure of lignite was predicted for the process of low-temperature oxidation. In low-temperature oxidation,alkanes and hydroxyls are the primary active structures observed in lignite, though ether may also react. These active functional groups react with oxygen to release heat, thereby speeding up the reaction between coal and oxygen. Finally, the content of various functional groups in the process of lignite low-temperature oxidation was analyzed by infrared analysis, and the accuracy of the model was verified.

Effects of the grinding process on the preparation and qualities of CWS

Two different grinding processes were examined to determine the effect grinding has on the quality of a CWS. A series of slurries was prepared from Australian (Au) and Chinese (YZ) coals. Both types of coal were ground by a Chinese (CUMT) and an Australian (JK) grinding process. The performance tests of the prepared CWS showed that fluidity of all slurries was acceptable. The concentration of the CWS from YZ coal ground by the CUMT grinding process was higher than when the JK grinding process was used. The highest concentration was 70.14% in this case. The concentration of the CWS prepared from Au coal by the JK grinding process was higher than when the CUMT grinding process was used. The highest con- centration in this case was 70.97%. These differences are caused by the particle size distribution devel- oped during the different grinding processes.

Automatic Process Control and Management in Laohutai Coal Preparation Plant

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