Structural properties of residual carbon in coal gasification fine slag and their influence on flotation separation and resource utilization:A review

Coal gasification fine slag(FS)is a typical solid waste generated in coal gasification.Its current disposal methods of stockpil-ing and landfilling have caused serious soil and ecological hazards.Separation recovery and the high-value utilization of residual carbon(RC)in FS are the keys to realizing the win-win situation of the coal chemical industry in terms of economic and environmental benefits.The structural properties,such as pore,surface functional group,and microcrystalline structures,of RC in FS(FS-RC)not only affect the flotation recovery efficiency of FS-RC but also form the basis for the high-value utilization of FS-RC.In this paper,the characteristics of FS-RC in terms of pore structure,surface functional groups,and microcrystalline structure are sorted out in accordance with gasification type and FS particle size.The reasons for the formation of the special structural properties of FS-RC are analyzed,and their influence on the flotation separation and high-value utilization of FS-RC is summarized.Separation methods based on the pore structural characterist-ics of FS-RC,such as ultrasonic pretreatment-pore-blocking flotation and pore breaking-flocculation flotation,are proposed to be the key development technologies for improving FS-RC recovery in the future.The design of low-cost,low-dose collectors containing polar bonds based on the surface and microcrystalline structures of FS-RC is proposed to be an important breakthrough point for strengthening the flotation efficiency of FS-RC in the future.The high-value utilization of FS should be based on the physicochemical structural proper-ties of FS-RC and should focus on the environmental impact of hazardous elements and the recyclability of chemical waste liquid to es-tablish an environmentally friendly utilization method.This review is of great theoretical importance for the comprehensive understand-ing of the unique structural properties of FS-RC,the breakthrough of the technological bottleneck in the efficient flotation separation of FS,and the expansion of the field of the high value-added utilization of FS-RC.

Multiscale analysis of fine slag from pulverized coal gasification in entrained-flow bed

Fine slag(FS)is an unavoidable by-product of coal gasification.FS,which is a simple heap of solid waste left in the open air,easily causes environmental pollution and has a low resource utilization rate,thereby restricting the development of energy-saving coal gasification technologies.The multiscale analysis of FS performed in this study indicates typical grain size distribution,composition,crystalline structure,and chemical bonding characteristics.The FS primarily contained inorganic and carbon components(dry bases)and exhibited a"three-peak distribution"of the grain size and regular spheroidal as well as irregular shapes.The irregular particles were mainly adsorbed onto the structure and had a dense distribution and multiple pores and folds.The carbon constituents were primarily amorphous in structure,with a certain degree of order and active sites.C 1s XPS spectrum indicated the presence of C–C and C–H bonds and numerous aromatic structures.The inorganic components,constituting 90%of the total sample,were primarily silicon,aluminum,iron,and calcium.The inorganic components contained Si–O-Si,Si–O–Al,Si–O,SO_(4)^(2−),and Fe–O bonds.Fe 2p XPS spectrum could be deconvoluted into Fe 2p_(1/2) and Fe 2p_(3/2) peaks and satellite peaks,while Fe existed mainly in the form of Fe(III).The findings of this study will be beneficial in resource utilization and formation mechanism of fine slag in future.

Effective separation of coal gasification fine slag: Role of classification and ultrasonication in enhancing flotation

Effective separation of residual carbon and ash is the basis for the resource utilization of coal gasification fine slag(CGFS).The conventional flotation process of CGFS has the bottlenecks of low carbon recovery and high collector dosage.In order to address these issues,CGFS sample taken from Shaanxi,China was used as the study object in this paper.A new process of size classification-fine grain ultrasonic pretreatment flotation(SC-FGUF)was proposed and its separation effect was compared with that of wholegrain flotation(WGF)as well as size classification-fine grain flotation(SC-FGF).The mechanism of its enhanced separation effect was revealed through flotation kinetic fitting,flotation flow foam layer stability,particle size composition,surface morphology,pore structure,and surface chemical property analysis.The results showed that compared with WGF,pre-classification could reduce the collector dosage by 84.09%and the combination of pre-classification and ultrasonic pretreatment could increase the combustible recovery by 17.29%and up to 93.46%.The SC-FGUF process allows the ineffective adsorption of coarse residual carbon to collector during flotation stage to be reduced by pre-classification,and the tightly embedded state of fine CGFS particles is disrupted and surface oxidizing functional group occupancy was reduced by ultrasonic pretreatment,thus carbon and ash is easier to be separated in the flotation process.In addition,some of the residual carbon particles were broken down to smaller sizes in the ultrasonic pretreatment,which led to an increase in the stability of flotation flow foam layer and a decrease in the probability of detachment of residual carbon particles from the bubbles.Therefore,SCFGUF could increase the residual carbon recovery and reduce the flotation collector dosage,which is an innovative method for carbon-ash separation of CGFS with good application prospect.

Review of the characteristics and graded utilisation of coal gasification slag

The characteristics of the energy structure of rich coal,less oil and less gas,coupling with a high external dependence on oil and natural gas and the emphasis on the efficient and clean utilisation of coal,have brought opportunities for coal chemical industry.However,with the large-scale popularisation of coal gasification technology,the production and resulting storage of coal gasification slag continue to increase,which not only result in serious environmental pollution and a waste of terrestrial resources,but also seriously affect the sustainable development of coal chemical enterprises.Hence,the treatment of coal gasification slag is extremely important.In this paper,the production,composition,morphology,particle size structure and water holding characteristics of coal gasification slag are introduced,and the methods of carbon ash separation of gasification slag,both domestically and abroad,are summarised.In addition,the paper also summarises the research progress on gasification slag in building materials,ecological restoration,residual carbon utilisation and other high-value utilisation,and ultimately puts forward the idea of the comprehensive utilisation of gasification slag.For large-scale consumption to solve the environmental problems of enterprises and achieve high-value utilisation to increase the economic benefits of enterprises,it is urgent to zealously design a reasonable and comprehensive utilisation technologies with simple operational processes,strong adaptability and economic benefits.

Characteristics of gaseous product from municipal solid waste gasification with hot blast furnace slag

Possibility of combustible gas production from municipal solid waste （MSW） using hot blast furnace （BF） slag has been studied.The objective of this work is to generate combustible gas from MSW using heated BF slag.In this experiment,the thermal stability of the MSW was analyzed by thermogravimetric analysis,and effects of temperature,gasifying agent （air,N2,steam） and BF slag on the gas products were investigated at 600？900 ？C.The thermogravimetric analysis indicates that the weight loss of MSW includes four stages：evaporation of the moisture,combustion of volatile materials,burning of carbon residue and burnout of ash.The contents of the combustible gas increase with increasing temperature,and the lower calorific value （LCV） increases rapidly at 600？900 ？C.It is found that volume fraction of CO,H2 and CH4 at different atmospheres increases in the order N2〈air〈steam.It is believed that BF slag acts as the catalyst and the heat carrier,which promotes the gasification reactivity of MSW.

Preparation of Sialon Powder from Coal Gasification Slag

X-ray fluorescence spectrometry（XRF）,X-ray powder diffractometry（XRD） and scanning electron microscopy（SEM） were used to characterize the chemical composition,phase constituent and microstructure of the coal gasification slag.Sialon powders were synthesized by carbothermal reduction and nitridation using the coal gasification slag as raw materials.The experimental results showed that glass and amorphous carbon were the main phases,quartz and calcite as minor crystalline phases were also presented in porous coal gasification slag.Main constituents of coal gasification slag were SiO2,Al2O3,CaO and residual carbon.Sialon powder with Ca-α-Sialon as main crystalline phase can be synthesized when coal gasification slag powders were reduced and nitrided at 1500 ℃ for 9 h using nitrogen flow of 500 ml/min.The coal gasification slag is a valuable and economic starting material for preparing Sialon powders.

Chemical looping gasification of sewage sludge using copper slag modified by NiO as an oxygen carrier

Chemical looping gasification(CLG) provides a novel approach to dispose the sewage sludge.In order to improve the reactivity of the calcined copper slag,NiO modification is considered as one of the good solutions.The copper slag calcined at 1100℃ doped with 20 wt% NiO(Ni20-CS) was used as an oxygen carrier(OC) in sludge CLG in the work.The modification of NiO can evidently enhance the reactivity of copper slag to promote the sludge conversion,especially for sludge char conversion.The carbon conversion and valid gas yield(V_(g)) increase from 67.02% and 0.23 m^(3)·kg^(-1) using the original OC to 78.34% and 0.29 m^(3)·kg^(-1) using the Ni20-CS OC, respectively.The increase of equivalent coefficient(Ω) facilitates the sludge conversion and a suitable Ω value is determined at 0.47 to obtain the highest valid gas yield(0.29 m^(3)·kg^(-1)).A suitable steam content is assigned at 27.22% to obtain the maximum carbon conversion of 87.09%,where an acceptable LHV of 12.63 MJ·m^(-3) and Vg of 0.39 m^(3)·kg^(-1)are obtained.Although the reactivity of Ni20-CS OC gradually decreases with the increase in cycle numbers because of the generation of NiFe_(2) O_(4-δ) species,the deposition of sludge ash containing many metallic elements is beneficial to the sludge conversion.As a result,the carbon conversion shows a slight uptrend with the increase of cycle numbers in sludge CLG.It indicates that the Ni20-CS sample is a good OC for sludge CLG.

Occurrence,leaching behavior,and detoxification of heavy metal Cr in coal gasification slag

Coal gasification slag(CGS)is a type of solid waste produced during coal gasification,in which heavy metals severely restrict its resource utilization.In this work,the mineral occurrence and distribution of typical heavy metal Cr in CGS is investigated.The leaching behavior of Cr under different conditions is studied in detail.Acid leaching-selective oxidation-coprecipitation method is proposed based on the characteristics of Cr in CGS.The detoxification of Cr in CGS is realized,and the detoxification mechanism is clarified.Results show that Cr is highly enriched in CGS.The speciation of Cr is mainly residual fraction(74.47%-86.12%),which is combined with amorphous aluminosilicate.Cr^(3+)and Cr^(6+)account for 90.93%-94.82%and 5.18%-9.07%of total Cr,respectively.High acid concentration and high liquid-solid ratio are beneficial to destroy the lattice structure of amorphous aluminosilicate,thus improving the leaching efficiency of Cr,which can reach 97.93%under the optimal conditions.Acid leaching-selective oxidation-coprecipitation method can realize the detoxification of Cr in CGS.Under the optimal conditions,the removal rates of Fe^(3+)and Cr^(3+)in the leaching solution are 80.99%-84.79%and 70.58%-71.69%,respectively,while the loss rate of Al^(3+)is only 1.10%-3.35%.Detoxification slag exists in the form of Fe-Cr coprecipitation(Fe_(1-x)Cr_xOOH),which can be used for smelting.The detoxification acid leaching solution can be used to prepare inorganic polymer composite coagulant poly-aluminum chloride(PAC).This study can provide theoretical and data guidance for detoxification of heavy metal Cr in CGS and achieve resource utilization of coal gasification solid waste.

Effects of Different Calcining Temperatures on the Properties of Ceramsite Prepared by High-carbon Gasification Slag

The structure and characteristics of high-performance lightweight aggregates produced by high-carbon gasification slag were investigated by X-ray diffraction,scanning electron microscopy,thermogravimetry/differential thermogravimetr,differential scanning calorimetry-Fourier transform infrared,and mercury intrusion porosimetry,respectively.The experimental results show that the ceramsite undergoes two weightless stages in the calcining process.With the increase in the calcining temperature,a large number of pores are formed inside the ceramsite,its structure becomes denser,but the calcining temperature band of the ceramsite becomes narrow.The crystalline phase of the ceramsite changes at different calcining temperatures and the mineral phase changes from the earlieralbite,quartz,oligoclase,hematite,etc,to a silica-aluminum-rich glass phase.The 1130℃ is a more suitable calcining temperature,and the cylinder compressive strength of ceramics is 11.59 MPa,the packing density,apparent density,porosity,and water absorption are 939.11 kg/m^(3),1643.75 kg/m^(3),28.11%,and 10.35%,respectively,which can meet the standards for high-strength lightweight aggregates.

Study on the removal of Hg^0 from flue gas by coal dry powder gasification coarse slag

The prevention and treatment of mercury in coal-fired power plants has always been the focus and difficulty.How to control the pollution of mercury to human body and ecological environment quickly and effectively is a hot research topic nowadays.As a low cost and potential adsorbent,there is a huge space for the development of coal dry powder gasification coarse slag.In this paper,Mercury osmotic tubes are heated by water bath tank as mercury source,and the scavenging effect of adsorbent on Mercury monomer under different influence conditions is explored.The adsorbent plays an important role in adsorption of mercury monomer because of its special active sites on the surface.The reason is that the adsorbent surface is rich in carboxyl group,hydroxyl functional group,combined with mercury to form complexes.This shows that chemical adsorption facilitates the adsorption process.

The study of the effect of gas-phase fluctuation on slag flow and refractory brick corrosion in the slag tapping hole of an entrained-flow gasifier

The service life of refractory brick in the slag tapping hole of the entrained flow gasifier was significantly lower than that in other locations.It was critically important to study the corrosion mechanism of refractory brick in the slag tapping hole for guiding industrial production.Considering the complex flow field in the slag tapping hole,the influence of gas velocity and temperature fluctuation on the service life of refractory brick was investigated in this study.The results showed that the slag flow characteristics periodically changed with the gas temperature and velocity fluctuations.The brick corrosion rate increased with the decrease of fluctuation frequency.Compared with the gas-phase velocity fluctuation,the gasphase temperature fluctuation had a more significant influence on the brick corrosion rate.When the fluctuation frequency was 0.01 Hz and the gas temperature fluctuation amplitude was 200 K,the corrosion rate of refractory bricks increased by 25%.It could be concluded that the fluctuation of gas-phase temperature was the main cause for the low service life of refractory bricks in the tapping hole.

Refractories Utilizability for Slagging Gasifiers

Slagging coal gasification process became a highlight of coal chemical industry in China during the last decade. Refractory lining＇ s life of slagging gasifiers is one of the most critical factors for a cost - effective operation. The paper introduces current status of coal gasification in China, lining structure of slagging gasifiers and performance of refractory lining. It also summarizes the major factors impacting on refractory wear in slagging coal gasifiers in four Chinese chemical plants, based on ten years of industrial experience. The utilizability is discussed in terms of cost -effectiveness of high chromia refractories and possibility of the alternatives.

Energy Recovery from MSW Treatment by Gasification and Melting Technology

The increase of waste production, joined to the difficulties concerning both the identification of new disposal sites and the construction of big conventional incinerators, led in recent years to the development of new technologies for waste management such as gasification and melting treatments. The possibility to introduce in the Italian context the DMS （direct melting system） technology, designed and manufactured by Nippon Steel Engineering Co. Ltd., has been taken into account for the scope of proposed work. DMS technology consists in MSW gasification, slags melting and combustion of the syngas produced, with the consequent generation of electric energy through a steam cycle. The system minimizes environmental impact, thanks to an effective recycling of useful resources such as inert melted slags and metals, featuring high flexibility in terms of treatment capacity due to its modular design. The aim of this article is to consider different plant configurations in order to optimize the energy recovery downstream the DMS module. As a case study, landfill gas exploitation integrated in the DMS plant will be considered as a typical situation that could occur in the Italian scenario. The energetic input provided by the biogas allows improving the thermo-economic performances according to market incentives.

Analysis of Steel Slag Treatment Process and Comprehensive Utilization

As a by-product of steel enterprises,steel slag has a huge output and is rich in valuable minerals,but its comprehensive utilization rate is very low.The article mainly introduces the hot splashing method,hot sealing method,and drum method for the treatment of steel slag outside the furnace,and compares and analyzes the advantages and disadvantages of the production operation process and steel slag treatment process.At the same time,it also introduces the residual slag+double slag process and gasification dephosphorization slag circulation steelmaking technology for steel slag treatment inside the furnace,providing direction for steel enterprises to clean and comprehensively utilize steel slag.

基于CFD-DEM方法的煤气化渣气流分级提炭模拟研究

【目的】煤气化渣提炭分质是实现其减量化、无害化、资源化利用的重要手段,气流分级法因其能够高效处理细粒级物料且无废水、废气排放而具有独特优势。【方法】基于CFD-DEM模拟,研究卧式涡轮气流分级机内气固流动状况,探明进气方向和涡轮转向的匹配关系,明确炭颗粒和灰颗粒的流动机制。优化涡轮气流分级机中进气口方向,预测入口气速和涡轮转速对气化细渣气流分级提炭效率的影响。【结果】结果表明:涡轮气流分级机的进气方向对流场分布和气化细渣提炭效率有显著影响。切向进气口易导致在分级区和淘洗区产生相互干扰的次级漩涡,影响气化渣炭和灰颗粒分离效率。优化切向进气为垂直向上后,避免了淘洗区和分级区相互干扰,消除了涡轮和叶片之间次级漩涡,改善并稳定了分级区内的流场,提高了气化细渣提炭效率。在优化后的涡轮气流分级机中,通过匹配入口气速与涡轮转速,富炭渣产品中的炭含量可达80.95%,炭回收率可达59.83%。

气化细渣、铝灰的活化及其吸附性能

以工业废渣——煤气化细渣(FS)、铝灰(AA)为原料,一步碱熔法制备介孔吸附材料。研究了上述介孔材料对水中亚甲基蓝的吸附性能,结果表明,FS的最佳处理条件为:mFS∶mNaOH=5∶10、煅烧温度450℃、处理时间5h;AA的最佳处理条件为:mAA∶mNaOH=5∶8、煅烧温度550℃、处理时间3h。经碱熔处理后,FS材料对水中亚甲基蓝(MB)的吸附容量由1.16mg/g(FS-0)提升到67.85mg/g(FS-2),增长了近58倍;AA对水中亚甲基蓝的吸附容量由1.4mg/g(AA-0)提升到23.95mg/g(AA-2),增长了近17倍。X射线衍射、扫描电子显微镜、比表面积分析及傅里叶变换红外光谱等表征结果表明,两种材料在碱熔过程中形成的介孔孔道、带有氧缺陷位的Si—O—基团以及大量的Al—OH和Si—OH键是其对亚甲基蓝吸附性能得到大大提升的原因。本研究表明FS和AA可以应用为一种廉价的亚甲基蓝吸附剂,为二者的资源化利用和印染废水的处理提供了一种潜在的方法。

煤气化渣的改性及其在水泥增强中的应用研究

为了解决煤气化渣在工业生产中大量产生但难以得到有效利用,以及传统水泥材料的强度提升受限的问题,本文研究了煤气化渣的改性以及在水泥中的应用。采用特定的溶剂,在适宜的温度和搅拌条件下,对煤气化渣进行改性处理,再将改性后的煤气化渣作为掺合料加入水泥中,评价了其作用效能。结果显示,随着煤气化渣的掺量增加,水泥强度先升后降,掺量为15%时强度最优。使用溶剂对煤气化渣进行改性,15%掺量下,2.5%的改性剂可使水泥块7d和28d的抗压强度分别达到2.15MPa和7.0MPa。在水泥碎石中,3%的改性剂可使水泥块7d和28d的抗压强度达到12MPa和18MPa。本文优化了煤气化渣的改性条件,优选了掺量和改性剂用量,将其掺入水泥后,提升了水泥基材料的强度,为煤气化渣在水泥工业中的高值化利用提供了理论和数据参考。

Structural and microwave absorption properties of CoFe_(2)O_(4)/residual carbon composites

Electromagnetic interference,which necessitates the rapid advancement of substances with exceptional capabilities for bsorbing electromagnetic waves,is of urgent concern in contemporary society.In this work,CoFe_(2)O_(4)/residual carbon from coal gasification fine slag(CFO/RC)composites were created using a novel hydrothermal method.Various mechanisms for microwave absorption,including conductive loss,natural resonance,interfacial dipole polarization,and magnetic flux loss,are involved in these composites.Consequently,compared with pure residual carbon materials,this composite offers superior capabilities in microwave absorption.At 7.76GHz,the CFO/RC-2 composite achieves an impressive minimum reflection loss(RL_(min))of-43.99 dB with a thickness of 2.44 mm.Moreover,CFO/RC-3 demonstrates an effective absorption bandwidth(EAB)of up to 4.16 GHz,accompanied by a thickness of 1.18mm.This study revealed the remarkable capability of the composite to diminish electromagnetic waves,providing a new generation method for microwave absorbing materials of superior quality.

Robust online temperature estimation of a membrane-wall gasifier

The gasifier temperature is a key parameter in the operation of a slag-tapping entrained-flow gasifier.However,there is no effective method for measuring the operating temperature of a membrane-wall-lined gasifier.In this study,a novel robust method for estimation of the online temperature was developed for a membrane-wall gasifier and applied in an industrial SE gasifier.The industrial test results show that the method can estimate the gasifier temperature within 0.04 s,and its value can be reliably obtained.Based on the combination of bench-scale gasifier validation,commercial-scale gasifier operation experience,and the comparison of different simulation methods,the proposed method is accurate and reliable for measuring the operating temperature of a membrane-wall-lined gasifier.

煤气化渣结构组成及其主要金属元素赋存形态

煤气化渣的减量化、资源化和无害化是目前煤化工行业的研究热点,对其物理化学特性及重金属含量与环境风险的研究是实现以上目标的基础。以宁东基地某煤化工生产企业的煤气化渣为研究对象,研究了粗渣和细渣的结构组成及主要金属元素赋存形态与环境风险。结果表明,煤气化渣由残炭和灰分(主要成分为SiO_(2)和Al_(2)O_(3),质量分数分别为50%和15%左右)组成。粗渣灰分含量高(质量分数>90%)且颗粒致密光滑,细渣残炭含量高(质量分数约20%)且孔隙丰富。含量高于500µg/g的金属元素主要富集在粗渣中,低于200µg/g的金属元素在细渣中富集。细渣中金属元素稳定性较低,特别是Cd,其非稳定态占比高于70%,且风险评价指数为34.16,环境风险高。本研究旨为煤气化渣的资源化和无害化处理提供基础数据。