四川盆地广安地区须家河组煤生烃过程研究

四川盆地广安地区天然气地质储量丰富,但其烃源岩发育有限。选取广安地区须家河组煤,采用封闭体系进行热解和动力学研究,对该地区的生烃特征和生烃过程进行模拟。研究该地区煤的生烃特征和生烃动力学参数,恢复该地区天然气的生烃史。结果显示,广安地区须家河组煤系烃源岩开始生气时间主要在晚侏罗世(距今168Ma左右),后期由于燕山运动影响,导致地壳抬升,地温骤降,在侏罗世与白垩世之间即140Ma左右结束生烃,其生气持续时间为28Ma左右。生烃转化率多在50%以上,具有短时期快速生气的特点。良好的生储盖组合与断裂不发育是天然气得以长期保存的关键。     

计算机远程综合监控系统在煤矿中的应用

在煤矿远程综合监控系统之中运用计算机技术,能够实现对煤矿监控的分级传输处理,将信息转化为视频图像,从而有效的提高煤矿的监控水平,保证安全监控的实时性以及监控的有效性。提高煤矿监控管理水平,减少煤矿安全事故,提高煤矿的生产效率。     

A molecular dynamics simulation study of PVT properties for H2O/H2/CO2 mixtures in near-critical and supercritical regions of water

Supercritical water gasification technology is an efficient and clean way to use the coal. This technology can convert carbon and hydrogen elements of coal into the mixtures of H₂O/H₂/CO₂ that can be used for electricity generation. The acquisition of PVT properties of H₂O/H₂/CO₂ mixtures is one of the most critical issues in realizing the design and operation of thermal power generation system using this technology. However, no experimental, theoretical and simulation studies exist regarding the PVT properties of H₂O/H₂/CO₂ in the near-critical and supercritical regions of water. In this paper, the molecular dynamics simulations of the PVT properties of H₂O/CO₂ mixtures are carried out and the theoretical calculations are conducted based on the equation of state, and the results are compared with the experimental values. Moreover, the PVT properties for H₂O/H₂ mixtures and H₂O/H₂/CO₂ mixtures in the near-critical and supercritical regions of water are predicted using molecular dynamics simulation and compared with the calculation results of the equation of state. The results of this paper are of great significance to the development of supercritical water gasification of coal, and could offer the reference for the application of H₂O/H₂/CO₂ mixtures in practical production.     

Experimental investigation on the influence of the pyrolysis operating parameters upon the char reaction activity in supercritical water gasification

Supercritical water gasification of coal is a clean and efficient method for coal utilization which can convert coal into H₂ and CO₂. In order to further reduce costs, a novel two-step cascade utilization method was proposed in this study: conducting traditional pyrolysis first and then gasifying the pyrolysis char in supercritical water. The influences of different pyrolysis operating parameters on gaseous products and char gasification in supercritical water were investigated. Quartz tube reactors were used to ensure the complete collection of gaseous products in pyrolysis process. The experimental results showed that both carbon and hydrogen conversion efficiency increased with temperature, and the increasing trend became not obvious after reaction for 5 min. The thermo-gravimetric curves showed that volatilization removal process was completed at the pyrolysis time of 5 min and higher pyrolysis temperatures were beneficial to the subsequent gasification process. The result also showed that residual weight was 15%–20% of the initial weight. Hydroxyl radicals kept stable during pyrolysis process with the absorption peak intensity increasing first and then decreasing, and mineral substance disintegrated gradually as time increased. As pyrolysis temperature increased, the peak of CC double bonds decreased, turning into stable functional groups and carbonyl group increased. Dispersive pores occurred at the surface of coal as residence time increased with particle size decreasing, specific surface area and reactivity increasing. The results might be used for the design of a cascade utilization system based on coal gasification in supercritical water.     

Application of general regression neural network to model a novel integrated fluidized bed gasifier

In order to better understand gasification performance, a general regression neural network (GRNN) was developed to model a novel integrated fluidized bed (IFB) gasifier to research the correlative relationship between the input and output parameters of the IFB gasifier. Additionally, the prediction accuracy of the GRNN model was compared with the multivariate nonlinear regression (MNR) method. The performances of the two methods were evaluated using the mean relative error (MRE), the root mean square error (RMSE) and the coefficient of determination (R²). The GRNN model simulated the IFB gasifier with a higher R², a lower RMSE and a lower MRE demonstrating the prediction accuracy of the GRNN model over the MNR method. Furthermore, the effects of the oxygen to coal ratio, the steam to coal ratio, the oxygen to fly ash ratio and the steam to fly ash ratio on gasification performance were analyzed using the proposed GRNN model.     

Lignite upgrading using a pulsing air classifier

Lignite is difficult to be effectively separated by traditional preparation techniques because of its sliming property and difficulty of subsequent dewatering. A dry separation method of using a pulsing air classifier is applied to decrease the ash content of lignite for improving its effective utilization. The lignite sample used in this study was collected from Inner Mongolia, China. Mineralogical characteristics of the lignite sample were analyzed, and the effects of airflow rate, pulse frequency, and feed rate on the separation efficiency of ?6 + 3 and ?3 + 1 mm size fractions were determined using the lab pulsing air classifier system. The results demonstrated that the ash content of the product was reduced by 10.18% and 30.98% for the ?3 + 1 mm and ?6 + 3 mm size fractions, respectively, and the pulsing air classifier has a better separation efficiency for a larger size fraction.     

Experimental study on pyrolysis characteristic of coking coal from Ningdong coalfield

The thermal decomposition of coal was the essential step of many reactions, thus it was widespread concerned. In order to investigate the behaviors and kinetics of coal pyrolysis, coal samples which obtained from Ningdong coalfield of China were pyrolyzed with a tubular furnace in argon atmosphere at the heating rate of 5 K min^?1. The primary gaseous products including CH₄, H₂, N₂, CO, CO₂, C₂H₄ and C₂H₆ were quantified using a gas chromatogram. It can be seen that with the temperature increasing, the yields of H₂ and CO increased, while the others decreased. In order to produce possibly much tar, the optimal temperature was 923 K. The characteristic of pyrolysis kinetics was determined by thermo gravimetric analysis measurement. The Coats–Redfern and Flynn–Wall–Ozawa methods was used to obtain kinetic parameters. The activation energy range of 50–200 kJ mol^?1 was determined.     

Effects of tertiary air damper opening on flow,combustion and hopper near-wall temperature of a 600 MWe down-fired boiler with improved multiple-injection multiple-staging technology

In consideration of increasing the tertiary air damper opening of a 600 MWe down-fired boiler with prior multiple-injection multiple-staging technology facilitated the coal burnout, while largely increasing the NO_x emissions. Additionally, the flame kernel was greatly moved downwards, thus causing significant temperature variations in the hopper near-wall region and the water wall in the lower furnace was vulnerable to overheating. This work concentrated on the comprehensively improved multiple-injection multiple-staging technology, both 1:20 scale cold aerodynamic tests and industrial experiments were conducted to examine the effects of tertiary air damper opening on flow, combustion, NO_x emissions and especially the hopper near-wall temperatures. The aerodynamic tests indicated that, on increasing the tertiary air damper opening from 40 to 70%, all the flow fields exhibit good symmetry. The tertiary air flows downwards along the hopper near-wall region, with a maximum near-wall dimensionless vertical velocity significantly increasing from 0.48 to 0.66, and accordingly, the dimensionless depth of downward airflow increases from 0.744 to 0.846. The industrial experimental results showed that, upon introducing more tertiary air, the ignition distance of fuel-rich coal/air flow shortens from 1.25 to 0.87 m. The coal burnout is enhanced, carbon in fly ash drops from 6.90 to 6.15%, while the NO_x emissions slightly increase from 593 to 641 mg/m³ at 6% O₂. On reducing the measuring height of hopper near-wall temperature from 9.1 to 3.3 m, the average heating rate increases from 0.44 to 0.63 °C/mm. The increased tertiary air damper opening presents an increasingly obvious cooling effect on the hopper near-wall region, with the temperature reductions around 50 °C, which is conductive to protect the water wall in the lower furnace from overheating.     

Dispersion and flow properties of charcoal oil slurries (ChOS) as potential renewable industrial liquid fuels

This work reports on a preliminary study aimed at developing an industrial liquid fuel derived from charcoal and vegetable oil. Its relevance relies on the high energy potential of charcoal, its renewable nature, storage and transportation capacity in liquid form, as well as on the economic and environmental advantages derived thereof. The ability of a commercially available charcoal to be dispersed in three different organic solvents was assessed through the rheological characterisation of the resulting charcoal oil slurries (ChOS). The charcoal was ground in a conventional ball mill and dispersed with the aid of three different surfactants. The effects of the most relevant factors influencing the rheological properties of the suspensions were evaluated, including: (i) the solvent producing the lowest fuel viscosity (η) at a given charcoal content; (ii) the most efficient surfactant (and its amount) minimising the fuel viscosity (η) at a given solids fraction; and (iii) the charcoal content, which should be as high as possible. High-stability ChOS containing 62 wt% solids and 0.4 wt% surfactant, and exhibiting adequate flow properties and high calorific values, were successfully obtained.     

Effects on enrichment characteristics of trace elements in fly ash by adding halide salts into the coal during CFB combustion

The effects on enrichment characteristics of trace elements (TEs) in fly ash by adding halide salts into the coal during coal combustion were conducted on a 6 kW_th circulating fluidized bed (CFB) experimental device. Results show that unburn carbon content in fly ash has little relationship with the concentration of TEs namely Hg, As, Pb, Cr and Mn. All the TEs are enriched in fly ash for the raw coal CFB combustion. Concentration of Hg and Mn increases with increasing the addition amount of CaCl₂, NH₄Cl and NH₄Br. As, Pb and Cr enrich in fly ash more strongly when adding more CaCl₂ into the coal while more addition of NH₄Cl and NH₄Br leads to the decrease of their enrichment compared to addition amount of 0.1 wt%. On the whole, putting halide salts into the coal results in the TEs enriched in fly ash, which benefits for TEs removal during the coal combustion. Combining this method with the chemical sequential extraction or thermal treatment of the fly ash will be a promising way to realize the TEs removal and their recovery.