热解温度对依兰煤热解特性的影响分析

本论文在处理量为2.5 kg/h的热解实验装置上,分别以两种烟煤和一种油页岩为原料,考察了热解温度对热解产物产率、组成和性质的影响规律。实验结果表明,当反应温度分别为481℃、514℃、519℃时,六级煤、油页岩、造气入炉煤的焦油产率依次达到最高,产率分别为13.58%、12.54%、4.23%;在实验温度范围内,随着温度的升高,气体产率不断增加,且气体组分不断变化。     

煤的理化性质对生物质和煤共热解焦油性质的影响

将木屑分别与黑山煤、神木煤以不同比例掺混,利用自制热解干馏炉进行共热解实验。比较木屑的添加对共热解焦油、水和轻质焦油产率的不同影响,结合煤和生物质的热重分析结果与煤的13C核磁共振分析表征,探讨煤的结构、煤和生物质的热化学反应特性,对共热解焦油产率和品质的作用机理。结果表明:在一定配比范围内,木屑和煤之间的交互作用明显提高了共热解焦油中轻质组分的产率,同时热解水产率低于计算值;轻质焦油中的脂肪烃组分主要由木屑和煤热解产生的烷基自由基相互化合生成;煤热解产生的芳烃类自由基由于与生物质热解产生的羟基自由基生成杂酚化合物,从而抑制了热解水的生成。     

煤热解过程中碱金属对碳黑形成的影响

通过分析担载碱金属Na的酸洗煤热解产物的浓度分布、化学结构与微观结构,研究碱金属对煤衍生碳黑形成的影响.结果表明煤热解产物的粒数与质量浓度分布分别在0.12μm与0.20μm附近存在峰值,无Na酸洗煤超细颗粒生成量较多;随着煤中含量增加,热解使Na先赋存于半焦中,抑制焦油的释放;之后过量的Na气化并抑制焦油向碳黑转化;Na可增加样品中含氧官能团含量,减少脂肪族化合物尤其是短链或支链化程度较高脂肪族化合物含量、增加芳香族化合物含量并降低芳香环稠化度;气化的Na可以造成碳黑微晶体晶格缺陷,形成一些嵌套或类晶体特异结构.     

温度对生物质热解产物有机结构的影响

在管式炉上研究了生物质在不同温度下的热解过程,采用傅立叶红外光谱仪研究了热解温度对稻草热解固体产物半焦和液体产物焦油的有机结构变化的影响,用色质联用仪(GC/MS)分析了焦油的主要成分随温度的变化。研究表明,生物质的热解主要集中在200～600℃,高温有利于气体产物的析出,半焦的量及其所含的有机官能团(C=O,C=C,C-H,C-O和OH等)随热解温度的升高快速减少;焦油的量随温度的升高先增大后减小,在500℃时达到最大值,焦油中官能团的种类较稳定,但是吸收峰强度随温度的升高呈减弱的趋势。     

煤与生物质共热解工艺的研究进展

热解是将固态原料转化为液体燃料、可燃气和焦的重要途径,是实现生物质资源清洁、高效利用的重要技术。将生物质与煤混合共热解是生物质资源利用的重要方法,两者混合热解不仅有助于降低CO_2的排放量,还能有效地解决能源短缺和环境污染带来的问题。文章综述了煤与生物质共热解技术的研究进展,系统地介绍了共热解过程中煤与生物质的相互作用以及热解温度、混合比例、滞留时间、升温速率、矿物质成分、物料粒径和热解反应器类型等因素对热解过程的影响,并对煤与生物质共热解技术的发展前景进行了展望。     

煤热解研究的分析方法

为了让更多的科研工作者了解煤热解试验仪器及其分析方法,对热重-差热、红外、气相色谱、质谱等仪器分析方法的特征性能进行了综述,重点描述了其在原煤、半焦、焦油、热解气体等分析研究中的应用,同时简要介绍了一些先进的联合分析法在煤热解研究中的应用。另外还对热重分析仪(瑞士METTLER-TOLEDO公司生产TGA/SDTA851e热重/同步差热分析仪)、傅立叶变换红外光谱仪(Nicolet公司生产的5700型)、气相色谱仪(5975MSD)、质谱仪(6890GC)进行了介绍。     

我国煤热解多联产技术的发展概况

目前煤热解多联产已成为一项提高煤炭资源综合利用率的高新技术,是未来洁净煤主要的发展方向.以煤热解为核心的多联产工艺已成为我国煤炭利用的主要途径,通过煤热解多联产技术可有效地将煤炭化工和电力工业结合起来,不仅解决了煤炭利用率低下、化工产品制造成本高等问题,而且对我国的环境保护有着重要影响.介绍了国内外煤热解多联产工艺的研究状况,并对国内几种典型的煤热解多联产工艺进行了评述,总结了当前煤热解多联产工艺的优缺点和主要发展方向.     

生物质气流床气化的热解前处理工艺

考察了热解作为生物质气流床气化前处理工艺的可行性,热解温度对气、液、固3种形态产物的产率和各方面的性能有不同程度的影响。通过半焦的电镜图片分析,证实了热解后生物质的多孔结构比较明显,使其有一定的吸附能力;通过元素分析比较了原料和热解产物中各元素含量的差别,说明热解可以显著提高半焦中碳元素含量,降低半焦中氧元素含量;考察了热解气中各组分在不同温度下的变化规律;通过原料和产物的热值比较,证实了热解可以显著提高气化原料的热值,为下一步的气化反应提供了有利条件。     

弱粘煤和不粘煤的快速热解及其团聚研究

对弱粘煤和不粘煤的快速加氢热解及在快速热解情况下发生的团聚现象进行了研究．研究发现,在高温加压快速加热条件下,氢气气氛中,煤的热失重率比煤的挥发分高,而在氮气气氛中,煤的热失重率低于煤的挥发分。同时,在高温加压快速加热条件下,在氮气气氛中的热失重率远低于氢气气氛中的热失重率。大多数弱粘煤和不粘煤,在高温下快速热解,无论在氢气气氛还是在氮气气氛中都发生团聚现象,即煤热解残炭团聚为圆柱状,且有一定的强度。有些煤(如Strongman煤和兴隆煤)在氢气气氛中残炭强度大于氮气气氛中的残炭强度。     

High-temperature solar pyrolysis of coal

Subbituminous coal from Western United States was pyrolyzed by directly exposing 50 mg powdered samples to concentrated solar radiation. It was found that exposure to flux levels > 200 W/cm² for 12.5 s devolatilized 51 per cent of the coal. At flux levels between 100 and 200 W/cm² devolatilization was slightly less. Gas yield was a maximum of 31 mmol/g coal at a flux of 100 W/cm² and decreased slightly with increasing flux. Gas yields were more than twice as great as those obtained by a laser technique developed to simulate solar pyrolysis. In experiments with spectral cut-off filters there was no effect due to changing the wavelength distribution of sunlight.     

Finding order in coal pyrolysis kinetics

A number of experiments have suggested that the rate constants for the release of tar and for the thermal decomposition of the various functional groups in coal pyrolysis depend on the nature of the bridging bond or of the functional group, but appear relatively insensitive to coal rank for lignites, subbituminous and bituminous coals. The principal variation of pyrolysis behavior with rank is due to variations in the concentrations of functional groups and hence, the amount of each pyrolysis product. If the insensitivity of coal pyrolysis kinetics to coal rank can be generally demonstrated, it represents an important simplifying assumption in any general theory of coal pyrolysis. But the rank insensitivity of rate constants is controversial. There are two major questions. What species exhibit rank insensitive kinetics? Quantitatively, what does insensitivity mean, variations less than factors of two, ten, hundred, etc.? This paper considers whether pyrolysis data in the literature support the hypothesis of rank insensitive kinetic rate constants. The experiments considered vary in duration from 1.4 msec to 12 hr and in temperature from 350°C to 1800°C. Considering the available data, it appears that the decomposition of aliphatic, methyl and aromatic functional groups and the evolution of tar and hydrocarbon species have rates which are relatively insensitive to rank variation. The rate varies by at most a factor of five between lignite and bituminous coals. Oxygen species are somewhat more rank sensitive. The factor of five variation in rate due to coal rank is substantially less than the factors of 100–10,000 in variation typical of reported rates. Rank variation appears therefore to be a minor cause for these differences which consequently must be attributed to the effects of heat and mass transfer and to the assumptions used in deriving a kinetic rate. The observation that pyrolysis rates are insensitive to rank over such a wide range of conditions suggests that using this approximation in a pyrolysis theory can have wide applicability.     

Upgrading of flash pyrolysis oil and utilization in refineries

Flash pyrolysis oil from an ENSYN RTP pilot plant was upgraded in a continuous bench scale unit with commercial CoMo and NiMo catalysts in anticipation of scaling up the process. Large amounts of product were produced in a pilot plant for use in an extended analytical characterisation programme.

In bench-scale experiments, high deoxygenation rates of 88–99.9% were achieved. Low liquid and high water yields were obtained. The fractionated products of the production run did not fulfil the requirements for direct use as gasoline and diesel.

The process is restricted by several operational problems such as rapid catalyst deactivation, coking and plugging. Due to high feedstock and hydrogen addition costs, pyrolysis upgraded oil by the process tested is significantly more expensive than petroleum-derived oil at present oil prices.     

Clean and highly-efficient utilization of coal

The International Symposium on Coal Combustion(ISCC-9)was held at the Qingdao City,China in July,21-24,2019.It attracted over 270 engineers and scientists from ...     

油泥-煤混合燃料热解产物的研究

利用色谱分析技术对油泥-煤混合燃料热解产物的析出规律进行研究。研究表明油泥-煤混合燃料热解主要产物为H2、N2、CO2、CO、CH4、C2H6、C2H4、C3H8和C3H6。无机气体产量在热解温度900℃达到最大值,烃类气体产量在热解温度650℃达到最大值。热解产物产量在煤占混煤比例为40%时达到最大值。     

Structural characteristics and flammability of low-order coal pyrolysis semi-coke

This study focused on the effects of pyrolysis temperature on the structural characteristics and combustion properties of low rank coal. The combustion performance of semi-coke at different temperatures was studied by using low-temperature pyrolysis technology and non-isothermal thermogravimetric analysis. The variation of functional groups and carbon structure was quantitatively analyzed. The results show that the temperature has a significant effect on the semi-coke structure and flammability. In the middle and low temperature pyrolysis stage, the removal of water, volatile matter and functional groups is mainly carried out, and the degree of condensation and graphitization of carbon atoms is not obvious. The semi-coke performance with a pyrolysis temperature of 1023K is close to that of anthracite. The pyrolysis process is accompanied by the destruction of carbonaceous and the formation of mesopores, which affects the combustion performance. As the temperature increases, the flammability of the semi-coke is lowered, and the chemical structure of the semi-coke is a major factor affecting the flammability. The method of Coast-Redfern integration was used to calculate the kinetic parameters of the semi-coke. As the pyrolysis temperature increases, the activation energy of the combustion reaction increases, which is consistent with the trend of combustion performance change.     

Energy from municipal solid waste: A comparison with coal combustion technology

The conversion of municipal solid waste (MSW) to energy can conserve more valuable fuels and improve the environment by lessening the amount of waste that must be landfilled and by conserving energy and natural resources. The importance of utilizing MSW was recognized in the 1991 U.S. National Energy Strategy, which sought to “support the conversion of municipal solid waste to energy.” One route to utilizing the energy value of MSW is to burn it in a steam power plant to generate electricity. Coal has long been the predominant source of energy for electricity production in the U.S.; therefore, a considerable science and technology base related to coal combustion and emissions control can be, and has been, applied with substantial benefit to MSW combustion. This paper compares the combustion of coal and MSW in terms of fuel characteristics, combustion technology, emissions, and ash utilization/disposal. Co-combustion of coal and MSW is also discussed. MSW issues that can be addressed by research and development are provided.The major environmental issues that designers of MSW combustion systems have had to address are emissions of trace organic compounds, particularly polychlorinated dioxins and furans, and trace elements such as mercury, lead, and cadmium. Emission of trace organics is generally the result of a poorly designed and/or operated combustion system; modern MSW systems use good combustion practices that destroy organic compounds during the combustion process. Proper control of air/fuel mixing and temperature, and avoidance of “quench” zones in the furnace, help to ensure that potentially harmful organics are not emitted. Computer codes and other design and troubleshooting tools that were developed for coal combustion systems have been applied to improve the performance of waste-to-energy systems.Trace element emissions from both coal and MSW combustion result primarily from vaporization of elements during the combustion process. Most of the trace elements that are vaporized condense on fly ash as the combustion products cool downstream of the furnace and can be effectively controlled by using an efficient particulate removal device. However, volatile elements, particularly mercury, are emitted as a vapor. Several mechanisms are available to capture mercury vapor and some are in use. The development of satisfactory control technology for mercury is a topic currently of high interest in coal burning.The potential for leaching of trace elements and organics from MSW residues after disposal raises issues about the classification and management of ash. Results of laboratory leaching tests, especially for lead and cadmium, have not been consistently supported by field experience. Careful interpretation of the available test protocols is needed to make sure that residues are properly managed.Because of the large scale of coal-fired boilers for electricity production, co-firing of MSW with coal in such boilers could consume large quantities of waste. Several short-term demonstrations have shown that co-firing is feasible. The issues involved in co-firing are emissions of trace elements, trace organics, and acid gases; boiler slagging and fouling; and long-term effects, such as corrosion and erosion of boiler tubes.Areas where research and development has contributed to improved MSW combustion include (a) the formation mechanisms of polychlorinated dioxins/furans, especially low-temperature, catalytic mechanisms, (b) methods of combustion air distribution in incinerators that result in better combustion and reduced emission of organic compounds, (c) the use of gas reburning to control NOx and reduce emission of organic compounds, (d) practical methods for removing organic compounds and mercury from MSW flue gas, (e) the performance of electrostatic precipitators in removing MSW fly ash, particularly when co-firing MSW and coal in existing coal-fired boilers, and (f) burning MSW in fluidized beds or of pulverizing refuse-derived fuel and firing it in suspension-fired, pulverized coal boilers.     

Static model of coal pyrolysis in a circulating fluidised-bed reactor

Four different coals were investigated: two sub-bituminous, one bituminous and lignite, which were processed in the temperature range 750–950 °C. The heat for pyrolysis was generated by partial gasification of the char produced. Air was used as the gasifying medium with amounts of 0.6–1.5 m³/kg of coal, depending on the required gasification-temperature. Two sequential phenomena were taken into account: char gasification and coal devolatilisation in respect of temperature. The experimental data on carbon dioxide and monoxide concentrations in a LCV gas produced were used for the correlation of Boudouard's equilibrium and the data on carbon burn-off and final volatile matter content in char were used for the solid-products yield. The equations for the quasi-equilibrium state were developed and calculated values were compared with the measurements. The model takes into account the equations developed and the total energy-balance assuming the heat losses of the experimental system. The investigated coal throughput amounted to 200–300 kg/h depending on the coal properties. Process characteristics were discussed, namely: the effect of air/coal ratio on the pyrolysis temperature; char and gas yield, volatile matter and ash content in a char; as well as the gas calorific value.