To study the transformation of organic structure and mineral matter in coal-biomass mixtures during co-gasification, the anthracite and rice straw addition with different ratios were isothermally gasified at 1100 °C under CO2 atmosphere in a fixed bed reactor. The phase-mineral composition, morphology and organic structure of solid residues produced at different gasification time were analyzed by X-ray diffraction, scanning electron microscopy coupled with energy dispersive spectrometer, Raman spectroscopy and other methods. Results revealed that the organic structure was changed in char as it became less ordered with the addition of biomass. The bulk concentrations of K and Na and their bearing minerals and phases in char increased with the addition of biomass during gasification process. The transformation of mineral matter played a significant role in promoting the coal gasification.

•The separation is a coupling process of azeotropic and extractive distillation by DMSO.•Solvent ratio of separation is related to the content of phenolics and aromatics.•The coal liquid distillate is separated effectively via one-step batch distillation.Efficient separation of different chemical components in liquid hydrocarbons from direct coal liquefaction is a meaningful process. This paper aims to separate the 150–180 °C coal liquid distillate into three fractions: aromatics, alkanes, and phenolics. The coal liquid distillate is composed mostly of hundreds of single-ring compounds and is not easy to study directly. Therefore, a model of the distillate on a molar ratio was defined as 1 t-butylbenzene (TBB): 1 t-butylcyclohexane (TBC): 1 phenol. And dimethyl sulfoxide (DMSO) was selected as the solvent to separate them from each other. The model compounds' vapor–liquid equilibrium shows that DMSO's effectiveness is obvious. In TBB-TBC-phenol ternary system, DMSO can entrain TBB into the light fraction and keep phenol in the heavy fraction, while TBC is in the middle fraction, which isn't affected. DMSOs' influence was studied and divided as follow: the hydrogen bond terminator between TBB and phenol, an entrainer for TBB, and an extractant for phenol. Finally the 150–180 °C coal liquid distillate is separated via batch distillation into three fractions: 150–160 °C fraction (containing 79.17 wt.% aromatics and 20.25 wt.% alkanes), 160–185 °C fraction (containing 81.30 wt.% alkanes and 17.69 wt.% aromatics) and a bottom product (containing 27.95 wt.% phenolics and 72.05 wt.% DMSO).

The purpose of this study was to reveal the structural evolution of cellulose-derived tars in the biomass/coal co-gasification environment. A two-stage reactor was employed, where the pyrolytic vapors of cellulose were produced in the top stage and the secondary reactions of these vapors took place in the bottom stage under a range of conditions. The roles of anthracite char and steam were examined by implementing three operational modes in the bottom stage: thermal cracking (TC), catalytic cracking (CC), and catalytic reforming (CR), over a temperature range from 600 to 900 °C. Anthracite char was effective in enhancing tar reduction at lower temperatures (≤700 °C), above which its effect diminished. Tar yields under the CC and CR modes were comparable in the studied temperature range, suggesting the minimum effects of steam on the tar amount. However, gel permeation chromatography coupled with a diode array detector (GPC–DAD) and gas chromatography–mass spectrometry (GC–MS) characterization of tars showed that both anthracite char and steam had significant influence on the composition of tar, in terms of the molecular weight distribution and aromatic cluster sizes. Specifically, at a high temperature (900 °C), the presence of anthracite char facilitated the reduction of aromatic compounds, especially those with larger aromatic ring systems (≥3 fused benzene rings). In addition, the used anthracite chars showed lowered specific surface areas, which was postulated to be the main reason for their slightly reduced gasification reactivity.

•Appropriate proportion of silicon phosphates is the guarantee of catalyst having high catalytic performance.•The decomposition of silicon phosphate in oligomerization maintained the activity of the catalyst.•A catalyst with more silicon pyrophosphate shows a better crushing strength.Solid phosphoric acid catalysts have been industrially used for propene oligomerization to improve the gasoline quality. However, solid phosphoric acid catalysts will lose their mechanical strength in the presence of water which is used to hydrolyze silicon phosphates to produce free phosphoric acids for maintaining the catalytic activity. In this case, to harmonize the catalyst lifetime and activity of solid phosphoric acid catalysts, the properties of silicon phosphate were investigated to achieve the maximum catalytic performance. A solid phosphoric acid catalyst was prepared with kieselguhr and concentrated phosphoric acid. Trace water was used to promote the release of active components from silicon phosphates during the reaction. Free phosphoric acid content, as a vital property of a solid phosphoric acid catalyst, was measured by ammonia temperature-programmed desorption. The crystal phase composition of silicon phosphates in a solid phosphoric acid catalyst was analyzed by X-ray diffraction. The catalytic performance was evaluated in a fixed bed under the conditions of 210 °C and 4 MPa. A solid phosphoric acid catalyst with relative content of 51% Si5O(PO4)6 and 49% SiP2O7 showed the best performance in improving catalytic activity and lifetime, and the conversion of propene was above 99% for nearly 70 h.

•An interactive effect was testified to exist in the co-pyrolysis of lignite and DLR.•Interactive effect was caused by the organic components and poor fluidity of DLR.•Optimal conditions for enhancing the yield and upgrading of tar were acquired.To utilize the coal direct liquefaction residue (DLR) and improve the tar yield and quality, experimental studies on co-pyrolysis of lignite and DLR were conducted with a fixed-bed reactor under atmospheric pressure in high purity nitrogen. In-situ micro-Raman experiments, Soxhlet extraction, scanning electron microscope, and X-ray energy spectra analysis were also performed to explore the interaction mechanisms during the co-pyrolysis process. The results indicated that there was an interactive effect between lignite and DLR, which increased the tar yield. This interaction was attributed to the hydrogenation of organic components in the DLR and mass transfer process in pyrolysis of DLR. Also, the co-pyrolysis of DLR and lignite with ratio of 0.15, pyrolysis temperature of 550 °C and particle size range of 0.425–0.85 mm resulted in the most pronounced interactive effect on the high tar yield. Under optimal operational conditions, the tar yield of co-pyrolysis reached 8.8 wt.% and the yield of n-hexane soluble was 61.4 wt.%.

•Impact of biomass on coal gasification was investigated in fluidized-bed reactor.•Energy and element utilization efficiency in co-gasification process were analyzed.•Low heating value and cold gas efficiency are chosen as the indexes.•Co-gasification favors the promotion of element utilization efficiency.•Co-gasification elevates the low heating value and cold gas efficiency.Co-gasification of coal and biomass has many merits with regards to feasibility in fuel supply and synergetic catalytic effect. In this paper, the influence of biomass on energy and element utilization efficiency during co-gasification is studied to further reveal the essence of the synergistic effect. Coal gasification, biomass gasification and the co-gasification were all performed in the same fluidized-bed reactor. It was found that the dry gas yield, the cold gas efficiency and the carbon conversion efficiency all increased with an increase of both biomass ratio (BR) and gasification temperature. The co-gasification temperature and the amount of water in the co-gasification process were seen to decrease with an increase of BR when keeping the H2/CO ratio as a fixed value. The elements utilization efficiency of carbon (C_EUE) and oxygen (O_EUE) were increased with the increase of BR while hydrogen element utilization efficiency (H_EUE) was decreased. H_EUE, O_EUE and C_EUE increased as the gasification temperature was increased, but O_EUE was observed to decreased when there was an increase in the steam flowrate and BR. H_EUE and C_EUE are optimized with an increase in the oxygen equivalent ratio.

A novel coal-based polygeneration system with CO2 recycling for CO2 capture is proposed. Two CO2 recycling schemes exist in this system. In the first, CO2 is recycled into the gasifier as the gasifying agent. In the second, CO2 is recycled into the gas turbine as a diluent. Compared with conventional CCS systems, this new system avoids the use of water gas shift and CO2 separation processes to capture CO2, and, more importantly, a part of CO2 can be converted into CO in coal gasification and be used to synthesize chemicals, improving carbon element utilization and chemical output. By means of exergy analysis, comparison with four conventional single production systems shows that the proposed system provides more than 11% in energy savings and more than 25% in capital investment saving. The exergy efficiency, CO2 emission, and internal rate of return may be expected to reach 46.3%, 0.47 t·(t-coal)−1 and 14.76%, respectively.

In order to utilize lignite in a clean and highly efficient way, an energy system for lignite pyrolysis by solid heat carrier coupled gasification is proposed in this study. The process is simulated and analyzed by Aspen Plus 11.1 on the basis of experimental data. The energy consumption distribution of the system and the mass ratio of the solid heat carrier to lignite, the most important technological parameters, are revealed. The choice of gasifier has the greatest impact on the energy efficiency of the system. Results show that, with a lignite handling capacity of 41.7 t·h–1, the yields of tar and coal gasified gas are 1.6 and 25.7 t·h–1, respectively, and 17% of the char is burnt to supply energy for the system while the remainder is used in the gasifier. Also, the surface moisture present in lignite and the phenol water from the tar can be utilized as the gasification agent in the coupled process, saving up to 8.9 t·h–1 water and decreasing the handling capacity of phenol water by 2.7 t·h–1, thereby reducing the net volume of polluted water emitted by the system. It is possible for the system as a whole to achieve an energy efficiency of up to 85.8%. The study also shows that the majority of the energy used by the system is consumed during the drying and pyrolysis processes. Exploiting new technology, integrating and optimizing the energy use of the system to reduce energy consumption will be beneficial to improving the overall system performance.

A new coal-based polygeneration system with CO2 recycle is proposed in this paper. With the gasified coal gas containing 23 vol % CO2 and the coke oven gas containing 25 vol % CH4 as the dual gas sources, the system mainly produces methanol, dimethyl ether, and electric power. The system adopts CO2/CH4 reforming to modify the C/H ratio of the syngas. Particularly, the CO2, coming from the distillation tower, is recycled separately back to be a reactant during gasification and the resource gas in the reforming unit. As the CO2 concentration in the exhausted gas from the distillation tower is more than 95 wt %, this system does not require a CO2 separation unit. The system avoids the conventional water–gas shift reaction that is used to adjust the ratio of C/H in the syngas, but fully uses the CO2 produced from coal gasification, which solves the problems of CO2 capture and storage. The performance of the whole system’s energy, CO2 emission, and economics are analyzed by Aspen Plus 11.1 and Aspen Icarus 11.1 software. Results indicate that the new system realizes 11.5% increase of chemical energy, 1.3% increase of internal rate of return and 33.8% reduction of CO2 emission at the expense of 8.4% of power output. Especially, the new system can save about 13–18% on energy versus single product systems. The scheme in which CO2 is recycled back to the gasifier and the reforming unit plays the most significant role in the comprehensive evaluation of energy utilization, CO2 emission control, and economy benefits of the system.

The influence of hydrogen bonding on the solubility of carbazole and anthracene in N,N-dimethylformamide (DMF) and isopropanolamine (IPA) is investigated accordingly by 1H nuclear magnetic resonance (NMR) analysis. The chemical shift for the free and hydrogen-bonding proton of the anthracene and carbazole solution in DMF, IPA, and the mixture of the two was collected by a 600 MHz 1H NMR spectrometer. It is proposed that DMF, IPA, and a mixture of the two would be able to efficiently refine carbazole from crude anthracene oil. This phenomenon is shown to be the result of the intermolecular hydrogen bond of N–H···O and N–H···N formed between carbazole and the DMF/IPA mixture solvent, which greatly enhanced the solubility of carbazole in DMF and IPA. The arising steric hindrance effects derived from the intermolecular hydrogen bonding between DMF and IPA result in the significant solubility decline of anthracene and carbazole in the DMF and IPA mixture.

To study the effects of operational parameters on gasifying characteristics in the jet-fluidized-bed reactor and illustrate the scaling relationships of jet-fluidized-bed coal gasifier in a scale-up process, we established an equivalent reactor network model for the gasifier using CHEMKIN 4.1 software. The model is based on hydrodynamic properties in the gasifier and knowledge of the burning zone and gasifying zone of the reactor. It involves two-phase flow between materials, heat and mass transfer, as well as the coal gasification process in the presence of mixed gases, most notably H2O, O2, N2, etc. The model was validated by comparing it to the experimental data of outlet gas compositions. To optimize characteristics of the jet-fluidized-bed coal gasifier, the influence of the oxygen feed rate into the center nozzle and the coal feed rate on the gasification process and gas composition were studied by the equivalent established reactor network. Within the calculation range, with the increase of the oxygen feed rate into the center nozzle, the jet region nearly doubled, the temperature increased by 306 K, carbon conversion efficiency rose from 68 to 97%; however, the temperature of the jetting region should be controlled within the coal ash-softening temperature, and in generated gases, the CO and H2 contents had clearly changed. With the increase of the coal processing capacity, the jet region temperature decreased by 252 K, the gasifier overall temperature decreased, and carbon conversion reduced from 98 to 74%.

•Cellulose and lignin volatiles were subjected to interactions with coal char.•Lignin tars were more refractory to reforming/cracking than cellulose tars.•Lignin tars had higher ratio of large aromatic ring systems than cellulose tars.•Both tars underwent the transition from phenolics to PAHs with temperature.•Biomass volatiles resulted in coke deposition on anthracite chars below 800 °C.The reforming characteristics of biomass volatiles on anthracite chars were investigated by comparing the structural evolution of tars derived from cellulose and lignin as the major biomass components. In a two-stage quartz reactor, the pyrolysis volatiles of cellulose and lignin were produced in the first stage and then reformed in the second stage with or without the presence of anthracite chars between 600 and 900 °C. The results show that the presence of anthracite chars enhanced the destruction of volatiles of both feedstocks. Furthermore, the tar yields of lignin showed a slower decreasing trend with temperature than those of cellulose, suggesting that the lignin volatiles were more refractory to be reformed. The lignin tars had higher molecular weights and contained higher percentage of compounds with large aromatic ring systems (≥3 fused benzene rings) than cellulose tars in the studied temperature range. Compositional analysis revealed that tars of both feedstocks experienced the transition from phenolic compounds to polycyclic aromatic hydrocarbons with increasing temperature. The surface areas of anthracite chars were reduced because of coke deposition after interacting with the volatiles of both feedstocks below 800 °C, above which the net gasification of chars took place.

•Promoted Ni2Mo3N catalyst by K improved the sulfur tolerance.•K used as an electronic donor caused an electron enrichment of the Ni phase.•Increasing reaction temperature is favorable to sulfur tolerance.Ni2Mo3N catalysts with different amounts of potassium were prepared by an impregnation method, and their sulfur tolerance in benzene hydrogenation in the presence of different amounts of thiophene was investigated. The results showed that the lower potassium loading samples (≤ 0.07 wt.% K) improved the sulfur tolerance obviously due to the electronic modifier of potassium, giving rise to an electron enrichment of the Ni phase, decreasing the chances for the formation of Ni–S bonds. At the same time, increasing the reaction temperature resulted in better sulfur tolerance of the un-promoted and potassium-promoted catalysts.Download full-size image