Effectiveness of Polish lignites as reburn fuels

The effectiveness of four Polish lignites as reburn fuels was studied in the laboratory-scale drop-tube furnace. The established rank of the lignites and chars used correlates with concentration of calcium in lignite. A comparison of the reburning effectiveness of partially devolatilized chars with that of the parent lignites showed that the parent lignites achieved a higher NO reduction than the chars.     

The effect of hydrothermal pretreatment on the structure and fast pyrolysis behaviors of ShengLi lignite

The structure and composition of coal determine its fast pyrolysis characteristics,and the study of the relationship between them can play an important role in the efficient and clean utilization of coal.So,in this work,hydrothermal pretreatment was used to artificially change the structure and composition of ShengLi (SL) lignite,which was used to investigate the influence of structural changes on pyrolysis.The physicochemical structure and composition of samples were characterized by X-ray diffraction,specific surface area and porosity analyzer,solid-state 13C nuclear magnetic resonance,Fourier transform infrared spectroscopy,and elemental analyzer.Pyrolysis experiments were carried out in a powder-particle fluidized bed reactor,and the distribution and composition of the pyrolysis products were ana-lyzed.The gasification activity of char was investigated by thermogravimetric analysis with a CO2 atmo-sphere.The results show that hydrothermal pretreatment (HTP) can destroy the cross-linking structure of SL lignite,and affect its aromaticity,pore structure,functional group,and carbon structure to change the distribution and composition of pyrolysis products of SL lignite,especially the composition of tar.Finally,the structure-activity relationship between the structure,composition,and pyrolysis characteristics of coal was comprehensively studied.     

Study on the liquefaction of Shengli lignite with NaOH/methanol

The behavior of liquefaction of Shengli (SL) lignite with NaOH-methanol was studied. Based on high content of water in lignite and the economy of the process (amounts of NaOH used), the effects of NaOH concentration, methanol content and water content on the liquefaction behavior of SL lignite were preliminarily investigated. The results show that SL lignite has a good reaction activity, and its conversion and product yield reach 98% and 99% at 300 °C for 1 h respectively, when the ratio of SL lignite, NaOH and methanol is for 1 g:1 g:10 ml. NaOH participates in the reaction. The increase of the amount of NaOH significantly increases the amount of tetrahydrofuran soluble (THFS) fraction. Methanol plays a promotion role in the liquefaction, which makes the product yield increase for about 16-23%. Water content has little effect on the SL lignite conversion, product yield and the product distribution. Solvent-extraction components of liquefaction products of SL lignite with NaOH-methanol are mainly THFS, toluene soluble (TS), hexane soluble (HS) and water soluble fractions (WS). The FTIR analyses of solvent-extraction components show that all of the fractions contain OH group, aromatic structure, carbonyl group and aromatic ether oxygen group.     

过热蒸汽携湿在褐煤干燥中的应用

通过调整过热蒸汽温度与流量,得到了理想的褐煤产品,并确定了最佳的携湿参数,为褐煤干燥携湿技术提供了理论依据。     

The investigation of coal-pyrite/lignite concentration and their separation in the artificial mixture by oil agglomeration

In this study, the concentration of coal-pyrite and lignite taken from Yozgat-Ayridam (Turkey) Coal Management was investigated by oil agglomeration.In the previous studies, the agglomeration of coal-pyrite was investigated using different bridging liquids (fuel oil, diesel oil and kerosene) and the combination of reagent (KEX, Acorga M5397)+kerosene. When using only bridging liquids, the agglomeration recovery of pyrite was very low. To increase the hydrophobicity of pyrite, KEX was used. However, the pyrite was not agglomerated with an acceptable recovery. But when using Acorga M5397, which is a chelating reagent, the agglomeration recovery of pyrite was increased. The pyrite was agglomerated with a recovery of 76.70 wt% by single-stage agglomeration.In the optimum conditions which were determined for coal-pyrite, the agglomeration recovery of lignite was investigated. It was found that the lignite could not be agglomerated with an acceptable recovery.To investigate the separation of coal-pyrite and lignite, the artificial mixture of coal-pyrite and lignite was prepared with the weight ratio of 1/4 of coal-pyrite and lignite. It was found that the pyrite could be agglomerated at a recovery of 96.54% with three-stage agglomeration process. The lignite concentrate was produced with a recovery of 73.96 wt% and the pyrite content of 0.86 wt%.These findings showed that the coal-pyrite and lignite could be separated by oil agglomeration using appropriate reagent and bridging liquid.     

Synergies in co-pyrolysis of Thai lignite and corncob

The results from TGA experiments at the temperature range of 300–600 °C evidently distinguished the different pyrolysis behaviours of lignite and corncob; however, no clear synergistic effects could be observed for the mixture. The investigation of co-pyrolysis in a fixed-bed reactor, however, found significant synergies in both pyrolysis product yields and gas product compositions. The solid yield of the 50:50 lignite/corncob blend was much lower (i.e. 9%) than expected from the calculated value based on individual materials under the range of temperatures studied, and coincided with the higher liquid and gas yield. The synergistic effect in product gas composition was highly pronouncing for CH₄ formation, i.e. three times higher than the calculated value at 400 °C. Possible mechanisms were described including the interaction between corncob volatiles and lignite particles, and the effect of the heat profiles of lignite and corncob pyrolysis on the temperature dependent reactions. The enhanced devolatilisation of the blend was explained by the transfer of hydrogen from biomass to coal as well as the promotion of low-temperature thermal decomposition of lignite by exothermic heat released from corncob pyrolysis. Moreover, water, which was one of the major components in corncob volatiles produced mainly at around 200–375 °C, can also be expected to act as a reactive agent to promote the secondary tar cracking producing more CH₄.     

The investigation of the floatability improvement of Yozgat Ayr?dam lignite using various collectors

In this study, the floatability of Yozgat Ayr?dam lignite using kerosene, kerosene+emulsifier and kerosene+emulsifier+surfactant has been investigated. It was determined that the combination of both kerosene+emulsifier and kerosene+emulsifier+surfactant were stable (except anionic), easily dispersible in water and formed very small oil droplets compared to the kerosene. It was concluded that all of the collectors except kerosene investigated in this study increased the floatability of Yozgat Ayr?dam lignite. However when the combustible recovery and flotation efficiency index were considered, the best results were obtained from the combination of both keresone+Acorga M5640 and keresone+Acorga M5640+Flotigol CS (non-ionic). It was based on the high binding and spreading tendency of both collectors over the coal surface.The concentrates having a relatively low ash content were obtained with the kerosene+Acorga M5640+Flotigol CS. Consequently, the floatability improvement of Yozgat Ayr?dam lignite was achieved by using the combination of both kerosene+emulsifier and kerosene+emulsifier+surfactant.     

Co-gasification of a lignite/waste-tyre mixture in a moving bed

The thermal treatment of waste-tyre by co-gasification with lignite was investigated on a commercial scale during the Lurgi gasification process. The experiments proved that this material can be treated in a mixture with lignite in the process of oxygen–steam pressure co-gasification in a moving bed, because a waste-tyre admixture improves the net calorific value of the raw gas obtained by 3% in comparison with that from the gasification of lignite alone. Further, it was found that the H₂S and CH₃SH contents in the raw gas are lower in the case of co-gasification than those from the gasification of lignite alone. Considering the very low reactivity of the char from waste-tyre and the resultant unburned carbon in the ash, the optimal content of the waste-tyre admixture in the gasified feed should not exceed 10 wt.%, whereas short-term increases of up to 20 wt.% will not cause any technological problems or significant economic losses.     

基于湿法气化的褐煤液化分级转化技术

分析了褐煤液化理论及影响因素,结合湿法气化技术,提出褐煤部分液化、液化残渣气化的分级转化技术,探索褐煤综合化、洁净化、集成化的利用途径。分析表明,褐煤具有较高的加氢液化活性,通过气化与液化技术结合,能够实现褐煤的高效利用。     

Characterization of nitrogen-containing aromatics in Baiyinhua lignite and its soluble portions from thermal dissolution

Soluble portions (SPs) 1-4 (SP₁-SP₄) were afforded from sequentially dissolution and alkanolyses of Baiyinhua lignite (BL) in cyclohexane, CH₃OH, CH₃CH₂OH, and (CH₃)₂CHOH at 300℃. They were analyzed with a gas chromatograph/mass spectrometer and quadrupole exactive orbitrap mass spectrometer (QEOTMS) with an atmosphere pressure chemical ionization source in positive-ion mode, while BL was characterized with an X-ray photoelectron spectrometer (XRPES). The results show that the yields of SP₂ and SP₃ are much higher than those of SP₁ and SP₄, and the total SP yield is ca. 39.0%. According to the analysis with XRPES, pyrrolic nitrogen atoms are the most abundant nitrogen existing forms in BL. Thousands of nitrogen-containing aromatics (NCAs) were resolved with QEOTMS and their molecular masses are mainly in the range of 200-450 u. The main NCAs are N₁O₁ and N₁O₂ class species with double bond equivalent values of 4-18 and carbon numbers of 7-30. The nitrogen atoms appear in pyridines, quinolines, benzoquinolines or acridine, and dibenzoquinolines or naphthoquinolines, while the oxygen atoms exist in methoxy and furan rings.     

Synthesis of weakly crystallized hydroxyapatite with Zn substitution and its effect on the calcium phosphate and calcium sulfate cements

Zn is an essential trace element in the normal growth and loading Zn into biomaterials for biomedical applications has always been a hot topic due to its immune regulation. The preparation and characterization of Zn-substituted weakly crystallized hydroxyapatite (WCH) are studied in this work, and Zn-substituted WCH was added to calcium phosphate and calcium sulfate cements (CPC and CSC) to address the effect of Zn²⁺ on the hydration crystallization behavior of calcium phosphate and calcium sulfate. Our results demonstrate that Zn²⁺ will inhibit the transformation of α-TCP to HA during the hydration reaction of CPC. And the adding of Zn²⁺ in CSC changed the crystallization morphology of calcium sulfate. The regulation of Zn on the crystallization behavior of calcium phosphate and calcium sulfate resulted in the different in vitro degradation behaviors of CPC and CSC. With the purpose of improving the biological effects of materials, the polarization of Zn²⁺ released from cements on macrophages was also characterized in this work, and the results showed that appropriate concentrations of Zn²⁺ can inhibit inflammation after stimulating RAW264.7 cells for an appropriate period of time. The presented results may be useful guidelines for the preparation and design of composite bone cement with specific Zn content.     

Development of a low cost micro-porous ceramic membrane from kaolin and Alumina,using the lignite as porogen agent

The manufacturing of low cost ceramic flat and tubular membranes via dry pressing and extrusion, using low cost material, namely, natural kaolin, Alumina, and lignite as a pore forming agent was the purpose in this study. These membranes are designed to be used as a support for multilayer ceramic membranes.This study includes the preparation and the characterization of the different membranes.The selected composition was 20% of lignite, 15% of Alumina and 65% of Kaolin, the membranes have been obtained at 1200 °C as a sintering temperature. The membranes show good behavior for both configurations, with a porosity above 36% and a mechanical strength of 39 MPa or the tubular membranes and 34% for the flat ones.     

Generalized desorption equilibrium equation of lignite in a wide temperature and moisture content range

Brown coal is the most abundant and economically viable source of energy. To increase the efficiency of power generation from brown coal predrying of lignite is probably the first step to be taken. Both air drying, or more energy efficient superheated steam drying, may be considered. For the design of both processes an equilibrium relationship between water activity, moisture content and temperature in a form of working desorption isotherm is needed. This work presents experimentally obtained results of sorption isotherms measurements at seven temperatures and one sorption isobar at atmospheric pressure obtained for Be?chatów brown coal. These results were compared to the results obtained by other authors for Australian and USA coals and due to relatively close fit of all data points one generalized equation of desorption equilibrium was fitted covering a wide range of temperatures from 5 to 260 °C and moisture contents up to 1.5 kg/kg. Adsorption isotherms are not described by the same equation since strong sorptional hysteresis was observed.     

Release of volatiles from the pyrolysis of a Victorian lignite at elevated pressures

A Loy Yang lignite sample was pyrolysed in a wire-mesh reactor at pressures from 1 to 61 bar. The char yield did not show considerable sensitivity to changes in pressure or heating rate and was mainly a function of temperature. However, the tar yield was sensitive to changes in pressure, holding time and heating rate. The tar yield at 1000 K s⁻¹ showed a minimum at around 6-11 bar. The tar yield at 1 K s⁻¹ increased slightly with increasing pressure from 1 to 20 bar. The UV-fluorescence spectroscopy of the tar samples indicated that the release of larger (three or more fused rings) aromatic ring systems was also greatly affected by increases in pressure. It is believed that increases in pressure have slowed down the bulk diffusion within meso- and macro-pores in the pyrolysing lignite/char particles. During the extended stay within the char particle, volatile precursors were thermally cracked to form mainly gaseous species as well as very small amounts of char. At very high pressures where the diffusion was very slow, the formation of light gases caused the pressure to build up within the particles, inducing the forced flow of volatile precursors out of the particles and leading to increased tar yield.     

Identification of reaction zones in a commercial Sasol-Lurgi fixed bed dry bottom gasifier operating on North Dakota lignite

The Sasol-Lurgi fixed bed dry bottom gasification technology has the biggest market share in the world with 101 gasifiers in operation. To be able to further improve the technology and also to optimise the operating plants, it is important that the fundamentals of the process are understood. The main objective of this study was to determine the reaction zones occurring in the Sasol-Lurgi fixed bed dry bottom (S-L FBDB) gasifier operating on North Dakota lignite. A Turn-Out sampling method and subsequent chemical analyses of the gasifier fuel bed samples was used to determine the reaction zones occurring in the commercial MK IV, S-L FBDB gasifier operating on North Dakota lignite. The reaction zones were further compared with the same reactor operating on bituminous coal.Based on the results obtained from this study it was found that about two thirds of the gasifier volume was used for drying and de-volatilising the lignite thus leaving only about a third of the reactor volume for gasification and combustion. Nonetheless, due to the high reactivity of the lignite, the char was consumed within a third of the remaining gasifier volume. Clear overlaps between the reaction zones were observed in the gasifiers thus confirming the gradual transition from one reaction zone to another as reported in literature. Due to the high moisture content in the lignite, the pyrolysis zone in the gasifiers operating on North Dakota lignite occurred lower/deeper in the gasifier fuel bed as compared to the same gasifier operating on South African bituminous coal from the Highveld coalfield. All the other reaction zones in the gasifier operating on bituminous coal were also higher in the bed compared to the lignite operation. This can therefore explain the higher gas outlet temperatures for the S-L FBDB gasifiers operating on higher rank coals when compared to the gasifiers operating on lignite. The fact that the entire reactor volume was utilized for drying, de-volatilisation, gasification and combustion with carbon conversion of >98% makes the S-L FBDB gasifier very suitable for lignite gasification.     

Experimental and numerical simulation of lignite chemical looping gasification with phosphogypsum as oxygen carrier in a fluidized bed

Phosphogypsum (PG) is a solid waste produced in the wet process of producing phosphoric acid.Lignite is a kind of promising chemical raw material.However,the high sulfur of lignite limits the utilization of lig-nite as a resource.Based on fluidized bed experiments,the optimal reaction conditions for the production syngas by lignite chemical looping gasification (CLG) with PG as oxygen carrier were studied.The study found that the optimal reaction temperature should not exceed 1123 K;the mole ratio of water vapor to lignite should be about 0.2;the mole ratio of PG oxygen carrier to lignite should be about 0.6.Meanwhile,commercial software Comsol was used to establish a fuel reaction kinetics model.Through computational fluid dynamics (CFD) numerical simulation,the process of reaction in fluidized bed were well captured.The model was based on a two-fluid model and coupled mass transfer,heat transfer and chemical reac-tions.This study showed that the fluidized bed presents a flow structure in which gas and solid coexist.There was a high temperature zone in the middle and lower parts of the fluidized bed.It could be seen from the results of the flow field simulated that the fluidized bed was beneficial to the progress of the gasification reaction.     

Effect of industrial microwave irradiation on the physicochemical properties and pyrolysis characteristics of lignite

The surface functional groups and pyrolysis characteristics of lignite irradiated by microwave were comparatively studied to evaluate the feasibility of using industrial 915 MHz for lignite drying. The drying kinetics, micro structure, chemical functional groups, re-adsorption properties, and pyrolysis characteristics of the dried coal were respectively analyzed. Results indicated that for typical Chinese lignite studied in this paper, 915 MHz microwave drying was 7.8 times faster than that of the hot air drying. After industrial microwave drying, the sample possessed much higher total specific surface area and specific pore volume than that of air dried sample. The oxygen functional groups and re-adsorption ratio of microwave irradiated coal decreased, showing weakened hydrophilicity. Moreover, during the pyrolysis of the coal dried by hot air and microwave, the yield of tar largely increased from 1.3% to 8.5% and the gas production increased correspondingly. The composition of the tar was also furtherly analyzed, results indicated that Miscellaneous hydrocarbons (HCs) were the main component of the tar, and microwave irradiation can reduce the fraction of polycyclic aromatic hydrocarbons (PAHs) from 26.4% to 22.7%.     

Experimental study on the effects of drying methods on the stabilities of lignite

The drying processes are always applied prior to the transportation or utilization of lignite, and result in notable changes in the stabilities of lignite. In this paper, the study on the effects of nitrogen and MTE drying process on the physico-chemical properties and stabilities of Zhaotong lignite was carried out. The briquettes produced by MTE drying in this study were 150 mm in dimension, and so had a much larger particle size than nitrogendried samples. Nitrogen adsorption, mercury intrusion porosimetry and scanning electron microscopy all suggested that drying was accompanied by the transformation of larger pores into smaller ones. Compared to nitrogen drying, the pore structures could be stabilized by the MTE process. The soluble salts were removed during MTE drying which resulted in the decrease in ash and the concentrations of some of the major metals.The removal of water enhanced the hydrophilicity of nitrogen dried samples, but did not affect the hydrophilicity of MTE dried samples. The moisture holding capacity of MTE dried samples reduced faster than nitrogen dried samples with the decrease of residual moisture content. Themoisture readsorption processes of MTE dried sampleswere strongly inhibited due to themuch larger particle size of sample produced byMTE drying than nitrogen drying. The susceptibility to spontaneous combustion, indicated by cross point temperature and self-heating tests, of nitrogen and MTE dried samples increased with the decrease of residual moisture content. The MTE dried samples are more liable to spontaneous combustion than nitrogen dried samples with the same residual moisture and particle size. However, the larger particle size of the MTE product made it more stable with respect to spontaneous combustion and also moisture readsorption.     

The effect of sodium on the Pd-catalyzed reduction of NO by methane

The kinetics of NO reduction by methane over Pd catalysts supported on 8 mol% yttria-stabilised zirconia (YSZ) has been studied at atmospheric pressure in the 620–770 K temperature range. Langmuir–Hinshelwood type kinetics are found with characteristic rate maxima reflecting competitive adsorption of NO and methane: NO adsorption is much more pronounced than that of methane within the temperature range of this investigation. Pd is an effective catalyst: 100% selectivity towards N₂ can be achieved at 100% conversion of NO over this wide temperature range. Sodium causes strong poisoning of the reaction. The response of the system to variations in NO and methane concentrations, temperature, and sodium loading indicate that this is due to the Na-induced enhancement of NO chemisorption and dissociation relative to methane adsorption, i.e. sodium enhances oxygen poisoning of the catalyst. These results stand in revealing contrast to the strong promotional effect of sodium in the reduction of NO by propene over the same catalysts. The very different response of the two hydrocarbon reductants to Na doping of the Pd catalyst receives a consistent explanation.     

基于缅甸褐煤为燃料的水泥烧成系统调试

缅甸金山水泥厂1500t/d熟料生产线采用褐煤为燃料。该厂针对褐煤挥发分高、热值低、灰分比例高,分解炉系统易发生结皮、结圈导致堵塞的特点,设计中进行了烧成系统的主要技术参数优化配置,以及窑尾预分解系统结构的设计优化。文章针对该预分解窑系统调试过程中遇到的问题,采取了以下措施:1选择适宜的配料方案(KH=0.93±0.01,SM=2.5±0.1,IM=1.6±0.1);2按制好煤、料、风、窑速的匹配;3稳定烧成系统热工制度,做到三稳一快。同时,对系统可能进一步实现优化提出了建议。