Experimental investigation and theoretical modeling on scale behaviors of high salinity wastewater in zero liquid discharge process of coal chemical industry

Zero liquid discharge(ZLD)treatment and reuse equipment of high salinity wastewater in coal-chemical industry often occur in various types of blockage problems because of high salt content,affecting the long-term stability of the device.In this study,the effects of solution temperature,steel,reaction time and wall roughness on fouling were investigated.The changes in the contents of fouling and fouling substances were qualitatively and quantitatively analyzed by XRD and EDS respectively,and the formation of scale was observed by SEM.The results show that with temperature increasing,Q235 steel is the most difficult to scale.Scaling rate of all salt scales reaches a maximum after 12 h,and the fouling rate decreases significantly from 12 to 48 h.It gradually stabilizes at 48 to 96 h.With the roughness increasing,the thickness of fouling layer increases,and a linear relationship is presented for 1 to 10 h.By comparing actual and simulated wastewater scaling rates,the relationship between actual and simulated wastewater scaling rates is y=ax-0.494.The composition of the scale was analyzed,calcium carbonate is the main product and increases with fouling time.Based on the above-mentioned results combining literatures,the hybrid prediction model with calcium carbonate as the main product is put forward.It is discussed microscopically that calcium carbonate is converted from aragonite and vaterite in a thermodynamically metastable state to calcite in a thermodynamically stable state.

Status and Suggestion for Modern Coal Chemical Industry and Coal Clean Technology

Coal is fossil fuel abundant and widespread all over the world. It is a vital resource for energy security in our country, because the supply is stable. In this paper, the important role of coal played in the total primary energy supply was described, and the status of modern coal chemical industry and clean coal technologies was analyzed. Based on the scientific research experiences of author, strategy and suggestion for Chinese development were proposed according to the regulation of scientific panning. In China, there are more social benefits and strategic meaning for developing the coal high-efficiency utilization technology. Considering of the general situation of our countries, these technologies with the features of can be industrialized, advanced, applicative, mature and feasible should be developed preferentially. The high-expend, low economic effectiveness and behindhand technologies should be abandoned. So, the development of coal clean technology in China should meet the natural resources, restrictive condition and elements of our countries industry situations. Based on these analysis, the most important technologies and fundamental researches should be prior developed in China.

China＇s Progress for Modern Coal-chemical Industry

介绍了我国现代煤化工项目的投产情况以及近年来取得的自主技术装备广泛应用、带动资源地区经济转型发展等业绩;指出煤化工产业仍存在工艺技术需进一步优化、产业布局难度大、环境保护和碳排放压力大、盈利能力受能源价格影响大等问题;提出扎实做好已投产示范工程达标达产、适时推进升级示范工程有序建设的发展趋势。

A study of fire propagation in coal seam with numerical simulation of heat transfer and chemical reaction rate in mining field

Spontaneous combustion of coal is a problem that affects the mining operation and generates environ-mental,economic,social and geotechnical impacts.This phenomenon has been divided into two pro-cesses:ignition and propagation.Fire propagation develops in coal seams because of a set of factors such as direction and wind speed,fracturing and temperature.In this work,heat transfer and chemical kinetics are studied from conservation equations of energy and species,respectively,using the software COMSOL Multiphysics to simulate the propagation of fires in coal seams.Two possible scenarios were analyzed that usually occur in the walls of the coal seams,such as fire focus and fire complete screens.It was found that the propagation kinetics of the fire changes depending on the temperature,the fractur-ing of rock mass and the area of fire influence.For temperature values lower than 300℃,there is con-sumption around 250 cm^3/h,values around 700℃,the consumption is 1500 cm^3/h,and for fires of 1200℃ have values of 3000 cm^3/h.Depending on the speed of propagation can vary from 4 to 17cm/day,considering on the level and fracturing of the final wall of the open pit.

CO2 and SO2 emission characteristics of the whole process industry chain of coal processing and utilization in China

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.

Spatiotemporal simulation and predication of heavy metal(loid) concentrations in coal chemical industrial areas with a soil environmental capacity model

Heavy metal (loid)(HM) accumulation in the soil and the HM spatiotemporal distribution have important implication for soil pollution prevention and remediation. The present study investigated the concentrations and spatiotemporal distributions of lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr) and arsenic (As) in the topsoil of a coal chemical plant in Ningxia Aulonomous region (Ningxia), China. Topsoil samples (/?= 153) were obtained using the checkerboard method, and the HM concentrations were determined. The soil residual rates of the five HMs were measured with leaching experinients and were applied in a soil environmental capacity model to predict the quarHitiHive variation of the HM concentrations. The predicted results were employed to estimate the HM spatiotemporal distribution within 2() years with the Kriging technique. The number of sampling sites, where all five HM concentratio ns exceed their corresponding background values in Ningxia, would be increased from 0 to 90% within 1() years of the plant operation. In addition, Pb and Cd were distributed along the traffic routes. Mercury and As were distributed near fuel gas emission vents. Chromium was mainly accumulated in slag dumps. The study may provide the theoretical and practical foun d at ion for future HM pollution control in coal chemical plants.

A review on nitrogen transformation and conversion during coal pyrolysis and combustion based on quantum chemical calculation and experimental study

The emission of NOx during coal combustion contributes to the formation of acid rain and photochemical smog,which would seriously affect the quality of atmospheric environment.Therefore,the decrease of NOx is of great importance for improving the efficient utilization of coal.The present review comprehensively summarized the influence factors and mechanisms of migration and transformation of nitrogen during the coal pyrolysis and combustion based on experimental study and quantum chemical calculation.Firstly,in the process of pyrolysis:the occurrence state and transformation of nitrogen were concluded.The influence of temperature,atmosphere,heating rate and catalyst on formation of NOx precursor and nitrogen migration path at the molecular level were summarized;Secondly,during the process of combustion:the influence of temperature,ambient oxygen concentration,physical structure of coal char,catalyst on heterogeneous oxidation of char(N)were summarized;The effects of char surface properties,catalyst and ambient atmosphere on heterogeneous reduction of NOx were also concluded.Based on the quantum chemical calculation,the reaction path of heterogeneous oxidation of char-N and heterogeneous reduction of NOx were described in detail.Current studies focus more on the generation of HCN and NH3,but in order to reduce the pollution of NOx from the source,it is necessary to further improve the process conditions and the optimal formula of producing more N2 during pyrolysis,as well as clarify the path of the generation of N2.Experiments study and quantum chemistry calculation should be combined to complete the research of directional nitrogen reduction during pyrolysis and denitration during combustion.

Experimental and mechanistic study on chemical looping combustion of caking coal

Under high-temperature batch fluidized bed conditions and by employing juye coal as the raw material,the present study determined the effects of the bed material,temperature,OC/C ratio,steam flow and oxygen carrier cycle on the chemical looping combustion of coal.In addition,the variations taking place in the surface functional groups of coal under different reaction times were investigated,and the variations achieved by the gas released under the pyrolysis and combustion of Juye coal were analyzed.As revealed from the results,the carbon conversion ratio and rate were elevated significantly,and the volume fraction of the outlet CO_(2)remained more than 92%under the oxygen carriers.The optimized reaction conditions to achieve the chemical looping combustion of Juye coal consisted of a temperature of 900℃,an OC/C ratio of 2,as well as a steam flow rate of 0.5 g·min^(-1).When the coal was undergoing the chemical looping combustion,volatiles primarily originated from the pyrolysis of aliphatic-CH_(3)and-CH_(2),and CO and H_(2)were largely generated from the gasification of aromatic carbon.In the CLC process,H_(2)O and CO_(2)began to separate out at 270℃,CH4 and tar began to precipitate at 370℃,and the amount of CO_(2)was continuously elevated with the rise of the temperature.

Chemical looping gasification of maceral from low-rank coal: Products distribution and kinetic analysis on vitrinite

The product distribution and kinetic analysis of low-rank coal vitrinite were investigated during the chemical looping gasification(CLG)process.The acid washing method was used to treat low-rank coal,and the density gradient centrifugation method was adopted to obtain the coal macerals.By combining thermogravimetric analysis and online mass spectrometry,the influence of the heating rate and oxygen carrier(Fe2O3)blending ratio on product distribution was discussed.The macroscopic kinetic parameters were solved by the Kissinger-Akahira-Sunose(KAS)method,and the main gaseous product formation kinetic parameters were solved by the iso-conversion method.The results of vitrinite during slow heating chemical looping gasification showed that the main weight loss interval was 400–600℃,and the solid yield of sample vitrinite-Fe-10 at different heating rates was 64.30%–69.67%.When b=20℃·min^(-1),the maximum decomposition rate of vitrinite-Fe-10 was 0.312%min1.The addition of Fe2O_(3)reduced the maximum decomposition rate,but by comparing the chemical looping conversion characteristic index,it could be inferred that the chemical looping gasification of vitrinite might produce volatile substances higher than the pyrolysis process of vitrinite alone.The average activation energy of the reaction was significantly reduced during chemical looping gasification of vitrinite,which was lower than the average activation energy of 448.69 kJ·mol^(-1) during the pyrolysis process of vitrinite alone.The gaseous products were mainly CO and CO_(2).When the heating rate was 10℃·min^(-1),the highest activation energy for CH4 formation was 21.353 kJ·mol^(-1),and the lowest activation energy for CO formation was 9.7333 kJ·mol^(-1).This study provides basic data for exploring coal chemical looping gasification mechanism and reactor design by studying the chemical looping gasification process of coal macerals。

Effect of chemical conditioning on the triboelectrification of coal and mineral particles

Chemical conditioning was used to modify the triboelectrification of coal and mineral particles.The chemicals tested included starch,lignin,kerosene,ethanol,acetic acid,salicylic acid,sodium oleate,Sodium Hexametaphosphate(SH),sodium silicate, Sodium Dodecylbenzenesulfonate(SDBS),Sodium Bicarbonate(SB) and ammonia.A high-speed,dry mixing method was employed.The charge-to-mass ratio of the coal and mineral samples,both untreated and treated,was tested using a Faraday cup. Dielectric constants were determined by measuring capacitance.It is found that the selectivity of the additives toward coal or minerals is not consistent.Salicylic acid is the optimal additive to enhance the triboelectrification performance of coal samples.Starch, lignin and sodium oleate are suitable for removal of pyrite.SH,sodium silicate,SDBS,SB and ammonia are suitable additives for the removal of ash-forming minerals.

Migration of sulfur in in-situ gasification chemical looping combustion of Beisu coal with iron-and copper-based oxygen carriers

Chemical looping combustion(CLC)is an energy conversion technology with high efficiency and inherent separation of CO_(2).The existence of sulfur in coal may affect the CO_(2) purity and the performance of oxygen carrier due to the interactions between sulfur contaminants and oxygen carrier.The migration of sulfur in Beisu coal during the in-situ gasification chemical looping combustion(i G-CLC)process using two oxygen carriers(iron ore and Cu O/Si O_(2))was investigated respectively.The thermodynamic analysis results showed the formation of metal sulfides was thermodynamically favored at low temperatures and low oxygen excess coefficients,while they were obviously inhibited and the production of SO_(2) was significantly promoted with an increase in temperature and oxygen excess coefficient.Moreover,part of sulfur was captured and fixed in the forms of alkali/alkaline earth metal sulfate due to the high amount of alkali/alkaline earth metal oxides in the coal ash or/and oxygen carrier.The experimental results showed that the sulfur in coal mainly released in the form of SO_(2),and the sulfur conversion efficiency(XS)in the reduction stage were 51.04%and 48.24%when using iron ore and Cu O/Si O_(2) respectively.The existence of metal sulfides was observed in the reduced oxygen carriers.The values of XSin the reoxidation process reached 3.80%and 7.64%when using iron ore and Cu O/Si O_(2) respectively.The residue and accumulation of sulfur were also found on the surfaces of two oxygen carriers.

Experimental Study on Chemical Looping With Oxygen Uncoupling Using Copper Based Oxygen Carrier and Different Volatiles Contained Coal Chars

采用溶胶一凝胶法制备CuO／CuAl204氧载体，研究了该氧载体在N2气氛下的释氧性能，发现氧载体774℃时开始释氧，且随着温度的升高氧气含量不断升高。随后，在流化床反应器中研究了挥发分含量不同的6种煤焦的化学链氧解耦燃烧（chemicalloopingwithoxygenuncoupling，CLOU）特性，结果表明，挥发分含量的增加和温度的升高均会加速煤焦燃烧，煤焦中碳元素转化率达到95％所需要的时间随着挥发分含量及温度的升高不断减少，相应的碳的平均转化率也不断增加；然而，较高的挥发分含量和反应温度都会导致CO2捕集率的下降。对于挥发分含量低的高平煤焦和东欢坨煤焦，C02捕集率超过99％，而对于挥发分高的胜利褐煤焦，C02捕集率不足95％。

Potential Impact of Carbon Emission Tax on Coal Chemical Industry

In the case of carbon emission tax,implementation target and effect of carbon emission tax are analyzed. For development status of Chinese coal chemical industry,carbon emission data of traditional and new coal chemical industries are contrasted and analyzed,and the impact of levying carbon emission tax on coal chemical industry is studied. Promotion implementation opinions of carbon emission tax in coal chemical industry are proposed,and coordinated development between China environmental taxation system and relevant industries is further explored.

Towards an Ethical and Ecological Approach to Electricity Generation: A Comparative Analysis of Coal and Nuclear Power in the USA

According to the US Energy Information Administration, about 4118 billion kilowatt-hours (kWh) electricity was generated at large-scale generation facilities in 2019. About 63% of this was from fossil fuels, e.g., coal, natural gas, petroleum, and other gases. Environmental exposure to particulates, sulfur dioxide, nitrogen oxides, mercury, arsenic, radioactive fly ash, and other pollutants are extremely detrimental to the human cardiovascular, respiratory, and nervous systems. Such exposure increases the risk of lung cancer, stroke, heart disease, chronic respiratory diseases, respiratory infections, and other illnesses. In light of the challenges associated with renewables providing large quantities of base load power, as well as other factors, the benefits offered by nuclear power should be reexamined by policy makers to move the country towards a more ecological and ethical method of electric power production. This paper offers a concise analysis of many of the salient issues, comparing electricity generation from coal plants and light water nuclear reactors.

Analysis of Contradiction Between Coal and Power Industry

At the beginning of 2008, the Central, East and South China suffered a rare snow and ice disaster. After the disaster, power generation and power grid enterprises faced a big problem of power coal supply.

Spectroscopic Elucidation of the Links between Char Morphology and Chemical Structure of Coals of Different Ranks

In this investigation, SAXS and XRD were used to investigate both the physical and chemical changes in six coals of different ranks subjected to heat treatment. The specific surface area which gives an indication of the reactivity of the coal (measures surface area available for reaction) was determined to be in the range of 70.04 - 260.40 m2/cm3 particle volume for lignite from 450°C - 700°C. The specific surface area was determined to be in the range of 51.58 - 239.00 m2/cm3 particle volume for sub-bituminous;440.60 - 241.70 m2/cm3 particle volume for light volatile bituminous;452.71 - 247.73 m2/cm3 particle volume for high volatile bituminous;349.11 - 347.52 m2/cm3 particle volume for semi-anthracite and 333.60 - 125.34 m2/cm3 particle volume for anthracite respectively. On the other hand, the aromaticity was determined in the range of 0.66 - 0.76 for lignite;0.67 to 0.80 for sub-bituminous;0.91 - 0.97 for light volatile bituminous;0.93 - 0.99 for high volatile bituminous;0.96 - 1.00 for semi-anthracite and 0.96 to 0.99 for anthracite respectively. The porosity, pore size distribution associated with SAXS and the other crystallite parameters identified with XRD were also determined. Links between the physical and chemical parameters were established.

Intelligent and ecological coal mining as well as clean utilization technology in China: Review and prospects

Coal is an essential fossil fuel in China; however, coal mining and its utilization are being under the increasing pressure from ecological and environmental protection. Therefore, the consulting project "Technical Revolution in Ecological and Efficient Coal Mining and Utilization & Intelligence and Diverse Coordination of Coal-based Energy System," initiated by Chinese Academy of Engineering, puts forward three stages(3.0, 4.0 and 5.0) of China's coal industry development strategy. Aimed at "reduced staff,ultra-low ecological damage, and emission level near to natural gas," breakthroughs should be achieved in the following three key technologies during the China Coal Industry 3.0 stage(2016–2025): including intelligent coal mining, ecological mining, ultra-low emission and environmental protection. This paper focuses on the development trends of the China Coal Industry 3.0 and its support for China Coal Industry 4.0 and 5.0 is analyzed and prospected as well, which may offer technical assistance and strategy orientation for realizing the transformation from traditional coal energy to clean energy.

Environmental assessment and nano-mineralogical characterization of coal,overburden and sediment from Indian coal mining acid drainage

The deterioration of environmental conditions is the major contributory factor to poor health and quality of life that hinders sustainable development in any region.Coal mining is one of the major industries that contribute to the economy of a country but it also impacts the environment.The chemical parameters of the coal,overburden,soil and sediments along with the coal mine drainage(CMD)were investigated in order to understand the overall environmental impact from high sulphur coal mining at northeastern coalfield(India).It was found that the total sulphur content of the coal is noticeably high compared to the overburden(OB)and soil.The volatile matter of the coal is sufficiently high against the high ash content of the soil and overburden.The water samples have a High Electrical Conductivity(EC)and high Total Dissolve Solid(TDS).Lower values of pH,indicate the dissolution of minerals present in the coal as well as other minerals in the mine rejects/overburden.The chemical and nano-mineralogical composition of coal,soil and overburden samples was studied using a High Resolution-Transmission Electron Microscopy(HR-TEM),Energy Dispersive Spectroscopy(EDS),Selected-Area Diffraction(SAED),Field Emission-Scanning Electron Microscopy(FE-SEM)/EDS,X-ray diffraction(XRD),Fourier Transform Infrared Spectroscopy(FTIR),Raman and Ion-Chromatographic analysis,and Mossbauer spectroscopy.From different geochemical analysis it has been found that the mine water sample from Ledo colliery has the lowest pH value of 3.30,Tirap colliery samples have the highest electrical conductivity value of5.40 ms cm^(-1)Both Ledo and Tirap coals have total sulphur contents within the range 3-3.50%.The coal mine water from Tirap colliery(TW-15 B)has high values of Mg^(2+)(450 ppm),and Br^-(227.17 ppm).XRD analysis revealed the presence of minerals including quartz and hematite in the coals.Mineral analysis of coal mine overburden(OB)indicates the presence both of pyrite and marcasite which was also confirmed in XRD and Mossbauer spectral analysis.The presented data of the minerals and ultra/nano-particles present shows their ability to control the mobility of hazardous elements,suggesting possible use in environmental management technology,including restoration of the delicate Indian coal mine areas.

An Experimental Study on the Conductivity Changes in Coal during Methane Adsorption-Desorption and their Influencing Factors

During the processes of methane adsorption and desorption,the internal structure of coal changes,accordingly leading to changes in electrical conductivity.In this paper,using low rank coal seams of the Yan'an Formation in the Dafbsi field as the research subject,the relationship between coal resistivity,methane adsorption quantity,and equilibrium pressure is analyzed through proximate analysis,mercury injection tests,low temperature liquid nitrogen adsorption tests,and coal resistivity measurements during methane adsorption and desorption.The results show that during the process of pressure rise and methane adsorption,the conductivity of coal increases,resulting from heat release from methane adsorption,coal matrix swelling and adsorbed water molecules replaced by methane,but the resistivity reduction gradually decreases.The relationship between coal resistivity and methane adsorption quantity and equilibrium pressure can be described by a quadratic function.During the processes of depressurization and desorption,the resistivity of coal rebounds slightly,due to decalescence of methane desorption,coal matrix shrinkage and water-gas displacement,and the relationship coincides with a linear function.Methane adsorption leads to irreversible changes in coal internal structure and enhances the coal conductivity,and resistivity can not be restored to the initial level even after methane desorption.The resistivity and reduction rate of durain are higher than those of vitrain,with relatively greater homogeneous pore throat structure and fewer charged particles in the double electric layer.In addition,moisture can enhance the conductivity of coal and makes it change more complexly during methane adsorption and desorption.