Catalysis of coal char gasification by alkali metal salts

A study has been made of the gasification behaviour, in carbon dioxide and steam, of a number of coal chars doped with small amounts of alkali metal carbonates. For a given additive, the magnitude of the catalytic effect increased with the rank of the parent coal. A progressive loss in catalytic activity on thermal cycling during steam gasification was associated with reaction of the alkali salts with mineral matter in the chars. The kinetic data were consistent with catalytic mechanisms involving oxidation/reduction cycles on the char substrates.     

The effect of plastic addition on coal caking properties during carbonization

The recycling process of waste plastics using coke ovens is now being studied. The effect of plastic addition on coal caking property was investigated. It was revealed that thermal decomposition products of plastics interacted with bituminous coal during carbonization in coke ovens. The effect of plastic addition on coal caking property varied with types of plastics. The addition of aliphatic polymers such as polyethylene (PE), polypropylene (PP) and poly(vinyl chloride) (PVC) had only a small effect on coal caking property and coke strength and in some cases PE addition increased coke strength. On the other hand, the addition of polystyrene (PS), poly(ethylene terephthalate) (PET) and terephtalic acid (TFA) inhibited coal expansion and fusion, decreased maximum fluidity and total dilatation, and deteriorated the coke strength. These differences were discussed from the viewpoint of the interaction between thermal decomposition products of plastics and hydrogen in coal. It was suggested that the radical formed as a result of PS or PET thermal decomposition abstracted hydrogen from coal, which resulted in the decrease in coal caking property.     

Change of pore properties during carbonization of coking coal

Porosimetry, sorption and density measurements are reported on two caking bituminous coals, West Virginia Jewel No. 2 medium volatile and a Pennsylvania Pittsburgh seam high volatile C, for final carbonization temperatures between 400 and 1000°C. Samples were not confined and heating rates of 3 and 8.2°/min were employed. The medium volatile samples exhibit pronounced maxima in pore volume, pore surface area and porosity between 600 and 800°C. These temperatures are considerably greater than the characteristic temperature and the temperature at which maximum dilation occurs. The high volatile C coal does not exhibit well defined maxima. Results are interpreted in terms of pore development mechanisms. A mathematical model for pore development is proposed and shown to correlate satisfactorily, the pore volume and surface area measurements.     

低碱度硫铝酸盐水泥干缩性能影响因素的研究

通过配制不同CaSO4/3CaO·3Al2O3·CaSO4比值、不同石灰石掺量的11个低碱度硫铝酸盐水泥,在养护湿度为30%的条件下,对其不同龄期下的干缩率进行测定。试验结果表明:低碱度硫铝酸盐水泥的干缩率随龄期的发展而增长,且到一定龄期后趋于稳定;低碱度硫铝酸盐水泥的干缩主要是由毛细孔和AFt共同失水引起的;AFt的形成数量决定其干缩率大小;就本试验而言,CaSO4/3CaO·3Al2O3·CaSO442%时,干缩率较低;石灰石是通过影响水泥中AFt形成量来影响低碱度硫铝酸盐水泥的干缩率的。     

The role of MCM-41 composition in the creation of basicity by alkali metal impregnation

Three types of mesoporous molecular sieves (silicate MCM-41, niobosilicate NbMCM-41, and aluminosilicate AlMCM-41) were impregnated with alkali metal acetates. The textural stability of the samples was estimated on the basis of XRD measurements and nitrogen adsorption/desorption methods. The acidic–basic properties of the obtained materials were tested in the cyclization of acetonylacetone and studied by FTIR spectroscopy after adsorption of methylacetylene (propyne) and pyridine. Two types of chemical reactions between mesoporous matrix and alkali metal salt/oxide were observed: the reaction between alkali metal salt and silica/silicate and the reaction between basic oxide and silanol groups or Na⁺ cations. In the first one the alkali metal silicate formation decreases from Li to Cs species and leads to the destruction of the material. The second reaction places alkali metal cations in extra framework positions, which increases from Li to Cs species and is only observed in the case of AlMCM-41 and NbMCM-41 materials. As a result of the second reaction Lewis acidity is generated. The average effect of these two interactions leads to the volcanic curve for basicity of M/AlMCM-41 and M/NbMCM-41 with the maximum for K-samples. In contrast, basicity of M/MCM-41 systematically increases from Li to Cs form since the second type of interaction does not occur for these samples.     

The effects of deicer salts on the pressure impregnation of bridge deck type concrete with methyl methacrylate

A group of cylindrical concrete specimens, containing various known quantities of deicer salts, were impregnated from the top surface under a pressure of 75 psig (517 KPa) until complete penetration of the concrete (5 in. or 12.7 cm) was achieved. It was found that increasing salt contents, up to 0.75% Cl^? by weight of the mortar fraction of the concrete, had no effect on quantity of monomer inbibed, the volume percent of porosity filled with the monomer, nor the degree of water absorptivity of the polymer impregnated concrete. A second group of specimens was impregnated from the top surface at various pressures ranging from 0 to 75 psig (101 to 517 KPa) to a given level of monomer loading. For a given pressure, monomer loading was found to vary directly with the square root of time. Also, it was shown that higher pressures provide denser polymer loadings, higher rates of impregnation, and for a given time period, increased depth of penetration.     

Effect of alkali treatment on the caking properties of coal

Three weakly caking and non-caking high volatile bituminous coals from India were converted into good caking derivatives by treatment with alcoholic alkali at 250–300 °C and 22–25.5 MPa. These derivatives showed high Gieseler fluidities with wide plastic range and may be useful as additives to coals for oven charges. During alcoholic alkali treatment, the organic material of coal undergoes extensive degradation into relatively low molecular weight substances which possess sufficient thermal stability to maintain a fluid state on carbonization. Increasing the severity of alkali treatment produces a pitch-like material from coal, with a potential use as a binder for formed coke, carbon electrodes etc.     

Effect of parent coal rank on the yield and properties of carbonization extracts

The paper describes the study of carbonization of solvent extracts derived from coals of different rank. The solvent was hydrogenated anthacene oil. The characteristics of the parent coals and of their extracts are presented here as well as the mass balance from carbonization of each extract at a final heat-treatment temperature of 803 K, the physicochemical and structural analysis of the cokes obtained, and the chemical analysis of the liquid and gaseous products. The experiments showed that the properties of the carbonization products significantly depend on the physicochemical properties of the parent extracts. Parent coal rank had a slight effect on carbonization yields from extracts, but markedly influences the structure and texture of the solid carbonization products.     

低温干馏煤焦油回收工艺改进

低温干馏主要产品为半焦,附产煤焦油和煤气,煤焦油的产率直接影响企业的经济效益。针对褐煤等低阶煤低温干馏析出粗煤气中焦油回收率低的问题,分析了粗煤气中携带大量粉尘对焦油回收造成的影响。通过对煤气净化工艺的改进发现,在煤气湿法降温前先用干法除尘对焦油回收率提高有显著的效果。     

煤种及炭化条件对活性焦表面化学性质的影响

在不同煤种及炭化条件下,于一间歇流化床上制备活性焦(AC)。使用XPS等分析手段考察不同制备条件下制得的活性焦表面化学性质的差异。研究结果表明,煤种不同制得的活性焦的表面性质相差较大;炭化条件(炭化温度400—800℃、炭化时间0—60min)对最终制得的彬县煤活性焦表面化学性质影响很小。     

Characteristics and carbonization behaviors of coal extracts

N-methyl pyrrolidone (NMP) raw coal extract (EXT), hydrogenated coal extract (HEXT) and the blend of EXT and HEXT in NMP (BLD), from two bituminous coals, were studied. The extracts were carbonized in both tube-bomb and a temperature programmable furnace. Elemental analysis, FTIR spectroscopy and optical microscopy techniques were employed to characterize the extracts and the carbonization residues. It was found that the extracts resembled petroleum-derived pitches in the hydrogen content and (C/H)_atomic ratio. Higher oxygen and nitrogen contents differentiated the coal extracts from commercial petroleum pitch. More carbon and hydrogen, and lesser oxygen and sulfur differentiated HEXT from EXT. The ratios of integrated IR band intensity for aromatic and aliphatic CH stretching indicate that the relative content of aliphatic hydrogen in EXT is higher than in HEXT. HEXT contains comparatively more aromatic hydrogen, a feature necessary for thermal stability and fluidity during carbonization. BLD materials are at a place somewhere in between. Kinetic modeling of the aliphatic hydrogen change during carbonization reveals that EXT has high carbonization rate and low apparent activation energy. This can be related to the optical texture size of carbonization residues. The residues made from EXTs exhibited fine mosaic optical texture and limited mesophase development. HEXTs were readily converted into highly anisotropic coke. BLDs produced carbonization residues with intermediate properties. Extracts with similar activation energies produced similar residues in the same coal series. The degree or extent of anisotropy displayed by the carbonization residues was found to be dependent on the relative distribution of aromatic and aliphatic hydrogen.     

Unusual effects of catechol upon the hydroliquefaction of coal

The effect of catechol on coal hydrogenolysis was studied using tetralin as a solvent vehicle. A constant high liquefaction yield was observed when the amount of catechol added was reduced from 10 to 0.1 % based on the weight of coal. Under the same hydrogenolysis conditions, identical conversion yields were observed even when no catechol was added. Separate experiments were carried out, using a new internal vessel and the original stirrer, to examine the effect of the stirrer on liquefaction yield. Improved liquefaction yields were achieved in these experiments (an increase from 31 to 64% at 400 °C and from 46 to 78% at 420 °C for Miike coal; from 26 to 48% at 400 °C and from 36 to 73% at 420 °C for Wandowan coal; and from 16 to 34% at 400 °C and 21 to 55% at 420 °C for Lithgow coal). This suggests that an active catalytic species is formed on the surface of the stirrer and the internal surface of the autocalve.     

Influence of alkali on the carbonization process—III: Dependence on type of alkali and of alkali earth compounds

3,5-Dimethylphenol-formaldehyde resin was carbonized up to 1000°C with various kinds of alkali and alkali earth compounds added. The hydroxides of Li, Na, K, Sr and Ba reacted with the resin to produce large amounts of hydrogen and CO. The order of reactivity was, Li <K <Na and Ca, Mg ? Sr <Ba. Carbonates evolve only a small amount of hydrogen, although evolution of CO was very large. Carbonates cannot react with reactive methylene groups or aromatic hydrogens, whereas hydroxides easily substitute these hydrogens with MO-, liberating hydrogen atoms. The reduction of carbonate with carbon takes place in a similar way as that with hydroxides. The lower the melting point of the alkali or alkali earth compounds is, the lower the temperature of evolution of hydrogen is. This may be due to the good wettability of lower melting alkali or alkali earth compounds.     

Mesoporous carbons synthesized by direct carbonization of citrate salts for use as high-performance capacitors

A simple one-step synthesis methodology for the fabrication of mesoporous carbons with an excellent performance as supercapacitor electrodes is presented. The procedure is based on the carbonization of non-alkali organic salts such as citrate salts of iron, zinc or calcium. The carbonized products contain numerous inorganic nanoparticles (i.e. Fe, ZnO or CaO) embedded within a carbonaceous matrix. These nanoparticles act as endotemplate, which when removed, leaves a mesoporous network. The resulting carbon samples have a large specific surface area up to ∼1600 m² g⁻¹ and a porosity made up almost exclusively of mesopores. An appropriate heat-treatment of these materials with melamine allows the synthesis of N-doped carbons which have a high nitrogen content (∼8–9 wt.%), a large specific surface area and retain the mesoporous structure. The mesoporous carbon samples were employed as electrode materials in supercapacitors. They exhibit specific capacitances of 200–240 F g⁻¹ in 1 M H₂SO₄ and 100–130 F g⁻¹ in EMImTFSI/AN. More importantly, the carbon samples possess a good capacitance retention in both electrolytes (>50% in H₂SO₄ and >80% in EMImTFSI/AN at 100 A g⁻¹) owing to their mesoporous structure which facilitates the penetration and transportation of ions.     

Carbonization of aromatic hydrocarbons—IV: Reaction path of carbonization catalyzed by alkali metals

The carbonization path of aromatic hydrocarbons catalyzed by alkali metals has been investigated to elucidate how aromatic hydrocarbons were converted into the isotropic coke, compared to the same reaction catalyzed by aluminum chloride which gave the anisotropic needle-like coke. Attempts were made to identify the intermediate products by means of elemental analyses, NMR, and mass spectroscopy, and the process was followed by the analysis of evolved gases. Effects of the catalyst migration at the intermediate step of carbonization on the properties of produced coke were also investigated to know when the destiny of the coke was determined. These results indicate that the isotropic nature of the coke obtained from the aromatic hydrocarbons with alkali metals is due to the extensive dehydrogenation of the intermediate at the early stage of carbonization at ca. 250°C. The dehydrogenation may raise the melting point of the carbonizing material. Other factors influencing the nature of the coke are considered to be unimportant in the present case.     

Improvement of wood properties by impregnation with multifunctional monomers

Southern pine samples with different dimensions and bulk densities were impregnated with the multifunctional monomer ethyl α-hydroxymethylacrylate (EHMA) and 5 mol % of fluorinated or nonfluorinated crosslinking agent. The maximum impregnation yield (105% by weight) was achieved under vacuum with good improvement of water repellency. Impregnation with EHMA plus another multifunctional monomer 2-vinyl-4,4-dimethyl-2-oxazolin-5-one (vinyl azlactone) was carried out to improve the mechanical properties of wood samples. Water repellency was also improved depending on the amount of vinyl azlactone in the monomer solution. A maximum of 41% antiswell efficiency (ASE) was obtained by impregnation with a 9 : 1 w/w mixture of EHMA and vinyl azlactone. Improvements of 38–54% in impact strength and 27–44% in compression modulus were achieved depending on the relative amount of vinyl azlactone incorporated. FT-IR and solution or solid-state NMR spectroscopy were used for chemical characterization of the polymers themselves and the wood-polymer composites.     

Removal of mineral matter from coal by alkali treatment

The removal of mineral matter from coal was attempted by caustic digestion followed by acid washing. A mild treatment at 460 K was found to be sufficient to remove most minerals and yet to avoid any substantial loss of heating value. The reaction products were identified by X-ray diffraction. Mass balance of each element was also clarified. The removal of major components, quartz and kaolinite, was rather easy, whereas the removal of Ca and Fe compounds strongly depended on the type of mineral matter.     

煤炭低温干馏技术现状及发展趋势

概述了煤炭低温干馏技术的现状以及目前国内的应用情况,并就煤炭低温干馏技术的发展趋势进行了阐述。     

Effect of mineral components on the reactivity of brown coal carbonization products upon steam gasification (Short Communication)

Data on a study of the activity of brown coals from the Borodino deposit in the Kansk-Achinsk Basin with various mineral matter contents in the course of steam gasification (700°C) are reported. A close correlation of the activity of carbonized coals on gasification with the concentration of native calcium in them was found. The decationization of coals with dilute solutions of hydrochloric, sulfuric, and acetic acids resulted in the almost complete removal of calcium, which was accompanied by a dramatic decrease in reactivity upon gasification and a considerable change in the texture characteristics of gasification products. The found behavior was related to the participation of calcium compounds (in oxide and/or carbonate forms) in the catalysis of carbon gasification reactions with steam.