我国煤炭应急管理存在的问题与对策

煤炭应急管理是能源安全的重要,近年来我国应急管理建设取得了初步成就,但同时面临着应急预案不健全、应急体制有待理顺、应急观念有偏颇、应急不全面等问题,需要坚持在依法行政、提高行政效率和信息公开等原则指导下,重塑应急理念、健全应急预案、理顺管理体制、完善应急。     

A simulation study on the enhancement of the shift reaction by water injection into a gasifier

Although coal gasification is a clean and efficient use of coal, a reduction of CO₂ emissions is needed to mitigate global warming. The aim of this study was to improve the thermal efficiency of fuel production and electricity generation by dry coal feed gasification. The primary cause of thermal efficiency loss is steam use in a water-gas shift reactor. The shift reactor, installed downstream from the gasifier, uses a catalyst to adjust the H₂/CO ratio of the syngas. We have proposed a new process in which water is injected at the outlet of the gasifier and is vaporized to enhance the extent of the shift reaction. This process utilizes the high temperature of the syngas, which is sufficient for the shift reaction to occur without a catalyst. We have developed a model that incorporates the shift reaction velocity to evaluate our proposed process. In an optimized 5-stage water supply case, we found that the CO conversion reaches 9.9% at a water/syngas ratio of 0.14 mol/mol (water/CO = 0.25 mol/mol); the CO conversion needed for dimethyl ether production is 31%. This new process can improve the efficiency and reduce the cost of coal gasification.     

煤炭消费减量化和清洁利用国际经验

目前中国仍处于煤炭经济阶段,煤炭在能源结构中占据主导地位.放眼全球,发达国家煤炭消费都已经实现或正在经历减量化和清洁利用,他们所经历的社会经济发展,以及处理与能源关系的经验,都值得正处于工业化和城镇化进程中的中国借鉴和参考.本文选取英国、德国、美国和日本四个典型国家作为案例,介绍四国煤炭消费发展的不同阶段以及采取的措施,并为中国煤炭消费控制提出建议.     

制定和实施全国煤炭消费总量控制方案

近几年来全国大范围重复出现的重度化雾霾强烈警示：以煤炭为主体的不合理的能源消费结构亟需改变.实践证明,除了继续实施能源强度和能源总量控制外,必须制定和实施全国煤炭消费总量控制.本文从能源系统改革、生态环境和气候变化约束、技术研发和应用、能源安全和协同效应等方面,对全国、地区和部门煤炭消费总量目标的设置进行了分析,并提出了政策、方案和市场为基础的实施建议.     

Influences of different comminution methods on maceral segregations,ignition, and pyrolysis of superfine pulverized coal

The same bituminous coal is grinded by three representative grinding systems, respectively. Tendencies of maceral segregations in three systems are analyzed. The influences of maceral segregations on ignition temperatures and flash pyrolysis products are compared and discussed.     

Study of chemical looping co-gasification (CLCG) of coal and rice husk with an iron-based oxygen carrier via solid–solid reactions

The chemical looping gasification (CLG) is a promising gasification technology for syngas production. It reduces the demand for pure oxygen and heat from outside by the cycle of oxygen carriers. The lattice oxygen is transferred by oxygen carrier like Fe₂O₃ in CLG. Considering the synergy between lignite and rice husk, the chemical looping co-gasification (CLCG) of lignite and rice husk with Fe₂O₃ as oxygen carrier was studied in this work. The mass loss of lignite increased by about 3% with the help of rice husk. Due to the synergetic effect, rice husk developed the pyrolysis of coal in the co-gasification. It is found that the most contributing reaction at around 800 °C–1000 °C in CLG is the gasification of char with Fe₂O₃via solid-solid reactions. The kinetic fitting was used to explore the reaction mechanism of CLCG. The modified random pore model (MRPM) fitted the experimental data well, which confirmed the solid-solid reactions between char and Fe₂O₃, and the synergy between lignite and rice husk in CLCG. Finally, the gas analysis was conducted in a fixed bed system with gas analyzers. It is found that Fe₂O₃ enhanced the concentration of CO and CO₂ in CLG process.     

Coal char particle secondary fragmentation in an entrained-flow coal-water slurry gasifier

Coal char particle size in the gasifier has an influence on the carbon conversion, gasifier slagging as well as the particle matter content in raw syngas. The particle size distribution in a bench-scale opposed multi-burner (OMB) gasifier illustrated that the secondary fragmentation behavior exists in the entrained-flow gasifier after the particles moving from high temperature impinging flame region to the gasification chamber outlet region. Particles larger than 200 μm in the impinging flame region have porosity structures with fragile shapes. Particle size distributions under different oxygen to carbon ratios (O/C) also indicate that there is an obvious fragmentation while the particle size is larger than 200 μm. As long as the coal char particles move from the impinging flame region towards the gasification chamber outlet region, the secondary fragmentation is probably taken place as a result of percolative fragmentation, undergoing gasification reactions and thermal stress. However, thermal stress fragmentation only has an influence on the particle sizes larger than 350 μm according to the calculation by a simplified mathematical model.     

660MW四角切圆锅炉混煤燃烧数值模拟分析

为了优化煤粉燃烧,提高电厂效益,以660MW超超临界四角切圆锅炉作为研究对象,利用CFD数值模拟方法对该锅炉混煤燃烧状态进行模拟分析。通过对多种掺混比例沿炉膛高度方向O2浓度、NOX浓度、CO2浓度等云图分布,对比分析了炉内燃烧状态。结果表明,在设计煤种与现有煤种掺混比例为4:1时,NOX浓度在炉膛中心明显增加,O2浓度在三种掺混方式下分布较为接近。在距一次风喷口较近区域,CO2的浓度相对较少;在壁面处,部分煤粉颗粒流动受阻,局部CO2变高。对比分析确定了该锅炉掺混的最佳比例,对合理选择煤种配比提供参考。     

Thermodynamic analysis and techno-economic assessment of synthetic natural gas production via ash agglomerating fluidized bed gasification using coal as fuel

Implementing coal to synthetic natural gas (SNG) is a key way to deal with the conflict between supply and demand of natural gas in China. For the coal to SNG process, gasification is a crucial unit, which determines the syngas composition and influences cost of coal to SNG system. In this current study, a coal to SNG system using ash agglomerating fluidized bed gasification is designed and modeled. According to the above results, the thermal performance and technoeconomic assessment of the coal to SNG system are performed. The research demonstrates that exergy efficiency and energy efficiency of the whole system are 55.37% and 61.50%, respectively. Additionally, the results of the economic evaluation show that the SNG production cost is 1.87 CNY/Nm³ with a coal price of 250 CNY/t and an electricity price of 0.65 CNY/kWh. Sensitivities to variables such as water price, electricity price, total equipment cost and coal price are performed. Coal price represents the most important sensitivity, but the sensitivity to water price is relatively small.     

Full-scale evaluation of SO2 capture increase for semi-dry FGD technology

This paper reports on a full-scale investigation of a possible increase of the SO₂ capture ratio in current semi-dry flue gas desulphurization (FGD) technology. The FGD unit is used for two 130 t/h steam PC boilers burning a blend of lignite and hard coal with dry ash-free sulphur content at 1.83%. The FGD unit has been designed to reach an SO₂ emission limit of 1350 mg/Nm³. The aim of the experimental work presented in this paper was to investigate the possibility of reaching SO₂ emission targets of 500 and 200 mg/Nm³. The investigation sought to determine the real correlation of SO₂ capture ratio with Ca/S and with the difference of dry-bulb temperature and dew point in the absorber Δt_AD. Generally, the SO₂ capture correlation with Ca/S has flat characteristics at a capture ratio >90%, which is required to reach the 200 mg/Nm³ target. In this case, lowering the Δt_AD in the absorber has only a weak effect. The 500 mg/Nm³ target requires an SO₂ capture ratio of about 80%; in this case lowering the Δt_AD by about 7 °C increases the SO₂ capture by 10% points at the same Ca/S ratio.