Fixed-bed pyrolysis of coal under hydrogen pressure at low heating rates

Fixed-bed hydropyrolysis has been investigated by treating 100 g coal up to 900°C and 10 MPa. The devolatilization rate of Beringen coal (32.8 wt% volatile matter) treated on a fixed bed approximates to that obtained by flash hydropyrolysis. However, the oil yield is smaller because of the slower heating of the coal and the rather longer residence time of the primary volatile matter in the reaction space. The product gas is mainly methane. The oil composition depends on the temperature of pyrolysis. The benzene content of the oil rises with temperature. At constant temperature, the influence of hydrogen partial pressure is important between 0–1 MPa. At higher pressure, the yields and compositions vary only slightly with pressure. It has also been shown that from 580°C pyrolysis under hydrogen yields an additional quantity of water, when compared with pyrolysis under inert atmospheres or under atmospheric pressure. This additional water comes from the hydrogenation reactions of the hydroxyl functions of heavy phenols and xylenols. This implies a hydrogen consumption (from 0.2–0.3 wt% of the coal), varying with the pyrolysis temperature.     

Liquefaction of Yallourn brown coal at low pressures and rapid heating rates

Liquefaction of Yallourn brown coal in solvents at high temperature for short contact times and low pressures has been studied. Very high asphaltene yields are achieved with hydrogen-donating solvents (hydrogenated Ashland pitch A240, hydrogenated anthracene oil, and hydrogenated pyrene). For hydrogenated pyrene, yields of almost 90% were obtained during reaction at 450°C for 10 min or at 510°C for 1 min. The average molecular weight of the asphaltene found was 270, with 40 wt% being accounted for by three-and four-ring polynuclear hydrocarbons. The effect of liquefaction temperature, time, and solvents on the asphaltene yield have been examined to clarify the properties required for the solvent under the present conditions used. The behaviour of the asphaltene during pyrolysis and hydrotreatment has also been studied. Some mechanistic aspects of high-temperature, short contact time liquefaction are discussed with regard to the reactivities of the brown coal and the solvents.     

Influence of transport effects on pyrolysis reaction of coal at high heating rates

The kinetics of coal pyrolysis may be influenced either by chemical reaction or by transport processes, the latter becoming rate-determining at increasing heating rate, particle size and pressure. Quantitative data are reported for those parameters which cause pyrolysis to become transport-controlled. The experiments have been performed with three different coals in H₂ and N₂, at heating rates ranging from 10³ to 10⁴ K s^?1, pressure from 0.1 to 150 bar and particle size from 0.063 to 0.8 mm.     

Investigation of an iron-based additive on coal pyrolysis and char oxidation at high heating rates

Iron-based catalysts have been shown to enhance coal pyrolysis and char oxidation at low to moderate temperatures and heating rates (< 1250 K and 1–1000 K/s). Such catalytic activity has not been demonstrated at high heating rates and temperatures approaching pulverized coal combustion applications. The effect of an iron-based additive on coal pyrolysis and char combustion was studied in a flat-flame burner system at high particle heating rates using a Kentucky bituminous coal. Pyrolysis and char reactivity of two treated coals with different catalyst loadings were studied and compared with the untreated coal. The total volatiles yield for the treated coals increased between 14 and 18% (absolute) on a dry ash-free basis compared to the untreated coal in experiments conducted at 1300 K. A first-order char oxidation model was used to compare the apparent char reactivities of the treated and untreated coals measured at 1500 and 1700 K. An increase in apparent char reactivity was observed for both treated samples.     

Viscosity of nitrogen gas at low temperatures up to high pressures: A new appraisal

The absolute viscosity of nitrogen gas was determined experimentally for the pressure and temperature range 1 to 150 atmospheres and 90°K to 400°K respectively. The maximum error in the data presented is believed to be better than ±1.5%, and ±1% for the high and low pressure data respectively. Two general correlating equations, one for atmospheric pressure and the other for all the available high pressure data, (i.e. densities up to 0.4 g/cc or 1.5 ρ (critical)) are presented, together with a table of recommended smoothed data, which are felt to be accurate to ±1.5% or better. Values for the low velocity collision diameter σ and maximum energy attraction functions are also presented for the low pressure data.     

Phase equilibria in the H2/CO2 system at temperatures from 220 to 290 K and pressures to 172 MPa

Phase equilibria in the system H₂/CO₂ have been studied experimentally using a vapor-recirculating apparatus. Measurements of vapor and liquid phase compositions were made for ten temperatures ranging from 220 to 290 K and pressures to 172 MPa. The mixture critical line and the pressure-temperature trace of the three-phase region solid-liquid-vapor have been located. The three-phase region and the critical line intersect at T ? 234.8 K and P ? 198 MPa to form an upper critical end point. Experimental results have been compared with previous studies and with predictions of three equations of state, Peng-Robinson, Redlich-Kwong and Deiters. Expressions have been derived for temperature dependent critical parameters that account for quantum effects in H₂, in calculations for H₂/X systems using the Peng-Robinson equation.     

Dehydration of d-glucose in high temperature water at pressures up to 80 MPa

Reaction of d-glucose in water to yield 5-hydroxymethylfurfural (5-HMF), 1,2,4-benzenetriol (BTO) and furfural was studied at high temperatures (up to 400 °C) and high pressures (up to 80 MPa) using a continuous flow reactor. Maximum temperature and pressure conditions gave maximum furfural yield. Increasing pressure from 40 to 70 and 80 MPa enhanced dehydration reactions to 5-HMF, but also enhanced hydrolysis of 5-HMF leading to the production of BTO and thus lead to lower yields of 5-HMF (below 10%). Remarkably, the dehydration reaction to 5-HMF and the hydrolysis of 5-HMF were both enhanced by the increase in water density at 400 °C.     

Integrated kinetics and heat flow modelling to optimise waste tyre pyrolysis at different heating rates

Pyrolysis is a promising technology to tackle the waste tyre disposal problem via converting the waste tyres into hydrocarbon fuels. This paper uses the experimental data of tyre pyrolysis (TGA/DTG and DTA) to examine both the kinetics and the heat flow at various heating rates for large tyre particles. An integrated model that considers the mass loss kinetics, exothermic kinetics, and heat flow together was developed. With the aid of the model, a multi-stage pyrolysis operation strategy is proposed. The strategy firstly starts with a heating stage to initialise the exothermic reactions in the pyrolysis. Then it changes to an adiabatic stage, where the exothermic heat is captured to facilitate the endothermic reactions afterwards. The multi-stage operation strategy achieves a significant energy saving comparing with the conventional operation strategy.     

Influence of carrier gas flow and heating rates in fixed bed hydropyrolysis of coal

Fixed bed hydropyrolysis experiments on a UK bituminous coal (82% dmmf C) at 580–650 °C and pressures up to 300 bar have indicated that tar yields depend strongly on the velocity of the hydrogen carrier gas relative to the static coal particles. Tar yields increase with increasing pressure provided that the superficial gas velocity is not reduced. Otherwise, tar yields can actually decrease because the beneficial hydrocracking reactions that occur are no longer sufficient to counter the increased char formation resulting from the slower rates of intra-particle diffusion and devolatilization of tar molecules. While raising the heating rate from 1 to 20 °C s⁻¹ had little effect on overall conversions, hydrocarbon gas yields increased significantly at the expense of tar. Moreover, the higher heating rate gave more aromatic tars, and the available evidence strongly suggests that the primary volatiles are hydrocracked before escaping from the coal particles as well as in the vapour phase.     

惰性气体对高真空蒸发与冷凝过程的影响

采用Bhatnagar Gross Krood(BGK)模型方程,建立了计算多组分稀薄气体流动的数学模型和求解方法。应用该模型对邻苯二甲酸二丁酯(DBP)和癸二酸二丁酯(DBS)物系在有惰性气体存在条件下的一维蒸发和冷凝过程进行了数值模拟,考察了各操作工艺参数对该过程的影响。研究结果表明惰性气体分压远大于蒸发液体的饱和蒸气压时,蒸发效率趋近于零;升高蒸发温度、冷凝温度以及增大蒸发面和冷凝面之间的距离都将使得蒸发效率降低,其中冷凝温度的升高将使蒸发效率显著减小。     

Relation between formation rates of methane and hydrogen on pyrolysis of coal under pressure

In an earlier paper¹ it became clear that secondary-methane formation occurs under certain experimental conditions during pyrolysis of coal. In order to study this more deeply, the evolution rates of methane and hydrogen were measured simultaneously for an anthracite and a lignite. The secondary-methane formation was accompanied by a corresponding decrease in hydrogen formation. It is suggested that secondary-methane formation occurs according to the equation C + 2H₂ = CH₄ on an average and is proportional to the partial pressure of evolved hydrogen.     

The pH of CO2-saturated water at temperatures between 308 K and 423 K at pressures up to 15 MPa

We report pH measurements for CO₂-saturated water in the pressure range from (0.28 to 15.3) MPa and temperatures from (308.3 to 423.2) K. Commercially available pH and Ag/AgCl electrodes were used together with a high pressure equilibrium vessel operating under conditions of precisely controlled temperature and pressure. The results of the study indicate that pH decreases along an isotherm in proportion to −log₁₀(x), where x is the mole fraction of dissolved CO₂ in H₂O. The expanded uncertainty of the pH measurements is 0.06 pH units with a coverage factor of 2. The reported results are in good agreement with the literature in pressure ranges up to 16 MPa at temperatures below 343 K. An empirical equation has been developed to represent the present results with an expanded uncertainty of 0.05 pH units. We also compare our results with a chemical equilibrium model and find agreement to within 0.1 pH unit.     

The solubility of H2S and CO2 in a diethanolamine solution at low partial pressures

The solubility of H₂S, CO₂ and their mixtures in a 2.0 kmol m^?3 aqueous solution of diethanolamine has been determined at 40°C and 100°C at partial pressures of the acid gases between 0.003 and 6.5 kPa. The results have been compared with values calculated by a method of prediction.     

Phase equilibria for the 2-ethoxyethyl acetate and 2-(2-ethoxyethoxy)ethyl acetate in supercritical CO2 at various temperatures and pressures up to 20 MPa

The (CO₂ + 2-ethoxyethyl acetate) and (CO₂ + 2-(2-ethoxyethoxy)ethyl acetate) systems at 313.2, 333.2, 353.2, 373.2 and 393.2 K as well as pressures up to 20.59 MPa have been investigated using variable-volume high pressure view cell by static-type. The solubility curve of 2-ethoxyethyl acetate and 2-(2-ethoxyethoxy)ethyl acetate in the (CO₂ + 2-ethoxyethyl acetate) and (CO₂ + 2-(2-ethoxyethoxy)ethyl acetate) systems increases as the temperature increases at a constant pressure. The (CO₂ + 2-ethoxyethyl acetate) and (CO₂ + 2-(2-ethoxyethoxy)ethyl acetate) systems exhibit type-I phase behavior. The experimental results for the (CO₂ + 2-ethoxyethyl acetate) and (CO₂ + 2-(2-ethoxyethoxy)ethyl acetate) systems correlate with the Peng–Robinson equation of state using a van der Waals one-fluid mixing rule including two adjustable parameters. The critical properties of 2-ethoxyethyl acetate and 2-(2-ethoxyethoxy)ethyl acetate are predicted with the Joback–Lyderson group contribution and Lee–Kesler method.     

煤制乙炔裂解气提浓工艺简介

介绍了高温等离子体裂解煤制乙炔裂解气提浓的工艺流程和运行情况,并根据工艺特性制定了安全预防措施。提浓装置经多次调试后运行稳定,当裂解气中乙炔体积分数为10％时,提浓后的乙炔体积分数可达99％。     

Solubility of isobutane and propane in polyethylene at high temperatures and low pressures

A novel procedure was developed to measure the solubility of isobutane and propane in both low and high-density polyethylene at temperatures to 500°F (260°C) and vapor pressures from 1 to 1500 torr (33 psia). These measurements represent the first known solubility measurements at these combined extremes of pressure and temperature. Excellent agreement was found when our data were extrapolated to higher pressures and compared with data from another source. In the temperature and pressure regions of interest in this work, the linear isotherms were fit with a form of the Flory–Huggins equation. With the equation in that form we can now estimate the ratio of solubilities of two solutes in a given polymer from pure solute data only. We can also predict the absolute solubility of nonpolar solutes in polyethylene at various temperatures and pressures using only critical temperatures and acentric factors of the solutes.