烘焙预处理对高含氮木质废弃物气流床气化特性与含氮污染物分布的影响研究

在螺旋热解反应器上进行不同温度和停留时间下高含氮木废弃物的烘焙预处理,将烘焙后的固体产物进行气流床气化,考察烘焙对高含氮木质废弃物气流床气化特性与含氮污染物分布的影响,结果表明:烘焙预处理可提高气化产气的H_2/CO值与产气热值,降低碳转化率;烘焙后气流床气化产物含氮污染物浓度与直接气化有明显区别,其中NH_3与HCN的浓度均明显低于未烘焙气化,NH_3浓度由未烘焙时的708mg/m~3降至348mg/m~3,HCN浓度降低了27%。在较高的烘焙温度和较长的烘焙停留时间条件下,NH_3与HCN的浓度有所增大,但仍低于未烘焙气化。     

高含氮木质废弃物加压气化含氮污染物生成研究

进行高含氮木质废弃物的加压气化试验，研究反应压强对于气化的影响。结果表明：在高压热重上，高压可抑制挥发分析出，提高700℃以上气化反应速度，使气化结束温度从1104降至1076℃；在加压气流床装置上，增大压强可明显提高合成气的品质，CO与H₂浓度明显增大，气化碳转化率、产气率与低位热值均有提高；随着压强的增大，高含氮木质废弃物气化产气中HCN与NH₃浓度出现下降趋势，从4606和2405 mg/m³分别降至393和622 mg/m³。     

生物质气流床气化制取合成气的试验研究

利用一套小型生物质层流气流床气化系统,研究了稻壳、红松、水曲柳和樟木松4种生物质在不同反应温度、氧气/生物质比率(O/B)、水蒸汽/生物质比率(S/B)以及停留时间下对合成气成分、碳转化率、H2/CO以及CO/CO2比率的影响.研究表明4种生物质在常压气流床气化生成合成气最佳O/B范围为0.2～0.3(气化温度.1300℃),高温气化时合成气中CH4含量很低,停留时间为1.6s时其气化反应基本完毕.加大水蒸汽含量可增加H2/CO比率,在S/B为0.8时H2/CO比率都在1以上,但水蒸汽的过多引入会影响煤气产率.气化温度是生物质气流床气化最重要的影响因素之一.     

填料塔中碳酸丙烯酯脱除沼气中的CO_2

以木薯渣发酵产生的沼气为原料气,采用10 m3/d脱碳工艺试验装置,以碳酸丙烯酯为吸收剂脱除沼气中的CO2,分别考察了吸收气液比、吸收压力、吸收温度、空气气提气液比、原料沼气中硫化氢浓度对脱碳效果的影响。试验结果表明,吸收气液比为55、吸收压力为800 kPa、吸收温度15℃、空气气提气液比为10时,净化气中CO2浓度为(6.44±0.34)%,CO2脱除率为(92.48±0.39)%。原料沼气中H2S浓度对碳酸丙烯酯的脱碳效果影响显著,当H2S浓度增加到0.4%时,与以脱硫后沼气为原料气时的脱碳情况相比,净化气中CO2浓度增加了1.66%。     

不同气化剂下海藻粉在气流床下气化特性试验研究

为考察O2/水蒸气和O2/CO2作为气化剂对海藻粉气化特性的影响,在自制的小型生物质气流床气化炉上开展海藻粉在气流床下气化特性试验研究。当氧气/生物质比（O/B）为0.3、气化温度为1200℃时,不同水蒸气/生物质比（S/B=0～1.2）对合成气组成有较大影响,其中H2产量的上升趋势最为明显,S/B=1.2时比单纯氧气气化提高了81.4%。而在O2/CO2气化条件下,由生物质产生的CO2随二氧化碳/生物质比（CO2/B）的增加而下降,当CO2/B=0.9时,H2、CO的产量分别比单纯氧气气化提高了33.9%和75.8%,热值由5521 kJ/m3上升至8576 kJ/m3。结果表明,如果以提高热值为制取合成气的目标时,添加CO2在一定范围内可以达到水蒸气的效果,同时降低了系统能耗及简化了气化设备。     

多孔床料对生物质产气特性影响实验研究

在小型常压流化床内采用多孔介质为床料,对生物质进行了空气、空气.水蒸汽气化实验并与普通工业用砂为床料的气化结果进行了对比,分析不同气化介质、温度及流量时多孔床料对生物质产气特性的影响.实验结果表明:产气中可燃气含量随气化温度升高而增大,流量对生物质气化影响存在最佳范围.与普通床料相比,多孔床料对H2和CO的生成以及对低碳氢化合物(CxHx)的催化裂解有较强的促进作用.     

生物质快速热解及水蒸气气化实验研究

对生物质气流床气化过程进行了小型台架实验研究,建立生物质气流床气化小型实验台架,进行生物质快速热解和水蒸气气化的实验,实验表明:温度提高有利于提高产品气的产率、气化过程的碳转化率和气化效率,但温度过高会促进CH_4的重整反应、水气变化反应、降低CO、甲烷含量,从而影响产品气热值。粒径对气化结果有着一定影响,粒径对气化结果的影响主要体现在固相内部升温速率和最终温度上,粒径越小,颗粒升温越快,能达到的最终温度越高。水蒸气气化过程中,适当的水蒸气的通入能大量提高产气中的H_2、CO的占比,提高碳转化率和H_2/CO的比值,碳转化率在S/B比为1.4时达到最大值96%,此时气化效率也高达94%,水蒸气的通入过量会导致炉内温度下降,各项评价指标均开始下降,降低燃气品质。     

生物质鼓泡床富氧-水蒸气定向气化实验研究

以制备合成气为目标,采用自供热鼓泡床对木屑进行提高H/C的富氧-水蒸气定向气化实验。分析当量比(ER)、水蒸气配比(S/B)、富氧浓度(OC)变化时对产气各组分及H_2/CO(H/C)的影响。结果表明:相同O_2浓度和水蒸气配比条件下,当量比在一定范围内越高,H/C越高;产气H/C主要受水蒸气配比和O_2浓度的影响;自供热鼓泡床富氧-水蒸气气化工艺中,制备合成气最佳工艺条件:O_2浓度为60%~70%、当量比为0.33~0.38、水蒸气配比约为0.56,对应最佳H/C为1.13。     

生物质蒸汽气化模拟研究

利用化学热力学软件(GasEQ)模拟了生物质蒸汽气化过程中温度、水蒸气与物料质量比(S/M)以及CO2浓度对H2,CH4和CO的影响;研究了冷合成气低位热值(LHV)和气化能量转化效率(q)随各参数变化的规律,并且考虑了外部能量的消耗。模拟研究得到:随着温度的升高,合成气的LHV总体表现出降低,并且q先增加后微弱下降,认为存在一个最优的气化温度(800⁹00℃);高S/M有利于H2的生成,提高H2的体积浓度,但水蒸气的增加,降低了LHV值,并且q先增加后减少,因为水蒸气会消耗大量外部能量,存在一个最经济的气化S/M;随着反应气中CO2浓度的升高,促进了生物质气化,并使CO浓度升高和H2浓度降低。     

氧煤比对气流床煤气化过程的影响

为研究氧煤比对气流床煤气化炉气化过程的影响,对某厂运行的Texaco气化炉进行了数值模拟研究。利用所建立的数学模型,分析了Texaco气化炉内的气化过程,以及氧煤比对炉内温度、气相成分及炉膛出口合成气成分的影响规律。结果表明:Texaco气化炉内下行火焰的长度约占气化炉高度的1/3,炉膛上部火焰高度区域内气相温度及主要成分浓度的变化梯度最大,而在炉膛下部气相成分及温度的变化均不明显;随着氧煤比的增大(0.95~1.10),气化炉出口合成气有效成分(H2+CO)浓度逐渐降低,CO2和H2O的浓度及气化炉内气相温度逐渐升高;在保证顺利排渣和合适的出口合成气成分的条件下,存在一个最佳氧煤比。     

基于铁矿石载氧体25 kWth串行流化床生物质化学链气化实验研究

设计并建立了25kW_(th)串行流化床生物质气化反应器,基于此反应器,以赤铁矿石作为载氧体,开展生物质化学链气化实验研究,考察气化反应器温度、S/B、载氧体添加比例对生物质气化特性的影响。当赤铁矿占床料比例高于40%时,该气化装置的气化反应器温度保持平稳,铁矿石载氧体的再生及传热性能优良。燃料反应器出口烟气的成分为H_2、CO_2、CO、CH_4和少量的C_2H_4。随着气化反应器温度升高,气化反应器出口烟气中CO、CH_4和C_2H_4体积分数逐渐降低,相应的CO_2体积分数逐渐升高。随着S/B由0.6升高到1.4,气化反应器出口烟气中H_2和CO_2体积分数逐渐升高,CO、CH_4和C_2H_4体积分数逐渐降低。另外,载氧体添加比例增加,生物质气化反应器出口烟气中CO、H_2、CH_4和C_2H_4体积分数呈减小的趋势,而CO_2体积分数显著增加。     

Experimental assessment of woody biomass gasification in a hybridized solar powered reactor featuring direct and indirect heating modes

Solar thermochemical gasification is an opportunity for the production of sustainable fuels from carbonaceous resources including biomass. Substituting conventional gasification processes by solar-driven technologies may enable cleaner production of H₂-rich syngas while saving feedstock resources and alleviating CO₂ emissions. This work addresses hybrid solar-autothermal gasification of mm-sized beech wood particles in a lab-scale 1.5 kW_th spouted-bed reactor. Hybridization under reduced solar power input was performed by injecting oxygen and additional biomass inside the gasifier for complementary heat supply. Increasing O₂:C molar ratios (in the range 0.14–0.58) allowed to heat the reactor cavity and walls progressively, while gradually impairing the reactor performance with an increase of the syngas CO₂ content and a decrease of the reactor cold gas efficiency (CGE). Gasification with mixed H₂O and O₂ was then assessed at thermodynamic equilibrium and global trends were validated experimentally, showing that control of H₂:CO ratio was compatible with in-situ combustion. The impact of reaction temperature (1200–1300 °C) and heating mode (direct or indirect) was experimentally studied during both allothermal and hybrid gasification. Higher H₂ and CO yields were achieved at high temperatures (1300 °C) under direct reactor heating. Hybridization was able to counterbalance a 40% drop of the nominal solar power input, and the measured CGE reached 0.82, versus values higher than 1 during allothermal gasification.     

碳酸盐中CO2气化生物质制合成气

以杉木屑为原料,CO₂为气化剂,熔融碳酸盐Li2CO3-Na2CO3-K2CO3(LNK)为热介质和催化剂进行气化制合成气(H2+CO)的研究,考察气化剂CO₂流量、CO₂通入方式、复合熔盐体系中添加的金属氧化物种类和Cr2O3含量等因素对气体产物组成分布及产率的影响。结果表明:CO₂流量显著影响气化反应的平衡;以鼓泡法通入CO₂时生物质的气化效果优于吹扫法的情况,CO₂流量为99.8 L/h时气化效果较好,合成气含量和产率分别达到61.4%和350.2 mL/g生物质;添加的金属氧化物中Cr₂O₃对生物质气化过程的促进作用优于MgO和Fe₂O₃,随着Cr₂O₃含量的增大,合成气含量先增大后略微减小,在Cr₂O₃含量为10.0%时最高,为67.9%。     

Potential of molten lead oxide for liquid chemical looping gasification (LCLG): A thermochemical analysis

Molten lead oxide is revealed to have favourable thermodynamic performance for gasification in a new process employing chemical looping of a molten liquid metal oxide. In this process, the feedstock is partially oxidized with molten lead oxide in the fuel reactor, while the reduced molten lead is oxidized in the air reactor. As with other chemical looping processes, this avoids direct contact between air and fuel, which prevents the undesirable dilution of the gaseous product with nitrogen. The Gibbs minimization method was employed together with thermo-chemical equilibrium analysis to assess the feasibility of the gasification process using graphite as a surrogate for more realistic, but complex carbonaceous fuels, together with steam and/or carbon dioxide as the gasifying agent. It was found that both the reduction and oxidation reactions of molten lead oxide with carbonaceous fuel are spontaneous. Likewise, the ratio of H₂:CO can be as high as 2.5, while the carbon conversion can reach 94% based on the thermochemical analysis. An energetic performance analysis was also employed for the case of a supercritical steam turbine cycle to extract work from the hot gaseous co-products. On this basis, the first law efficiency of the power cycle was estimated to be up to 33.8%, while the syngas co-product stream for applications such as Fischer-Tropsch synthesis has a chemical exergy efficiency of 41%.     

The influence of temperature and heating rate on the slow pyrolysis of biomass

The slow pyrolysis of biomass in the form of pine wood was investigated in a static batch reactor at pyrolysis temperatures from 300 to 720°C and heating rates from 5 to 80 K min⁻¹. The compositions and properties of the derived gases, pyrolytic oils and solid char were determined in relation to pyrolysis temperatures and heating rates. In addition, the wood and the major components of the wood—cellulose, hemicellulose and lignin—were pyrolysed in a thermogravimetric analyser (TGA) under the same experimental conditions as in the static batch reactor. The static batch reactor results showed that as the pyrolysis temperature was increased, the percentage mass of solid char decreased, while gas and oil products increased. There was a small effect of heating rate on product yield. The lower temperature regime of decomposition of wood showed that mainly H₂O, CO₂ and CO were evolved and at the higher temperature regime, the main decomposition products were oil, H₂O, H₂, hydrocarbon gases and lower concentrations of CO and CO₂. Fourier transformation infra-red spectroscopy and elemental analysis of the oils showed they were highly oxygenated. The TGA results for wood showed two main regimes of weight loss, the lower temperature regime could be correlated with the decomposition of hemicellulose and the initial stages of cellulose decomposition whilst the upper temperature regime correlated mainly with the later stages of cellulose decomposition. Lignin thermal decomposition occurred throughout the temperature range of pyrolysis.     

秸秆类生物质催化合成甲醇的实验研究

为了将农业废弃物转变为燃料甲醇，对玉米秸秆燃气进行合成气优化实验，在5MPa压力下，采用等温积分反应器和国产C301铜基催化剂，对合成气进行催化合成甲醇的实验研究。     

Characterization of free radicals by electron spin resonance spectroscopy in biochars from pyrolysis at high heating rates and at high temperatures

The concentration and type of free radicals from the decay (termination stage) of pyrolysis at slow and fast heating rates and at high temperatures (above 1000°C) in biomass char have been studied. A room-temperature electron spin resonance spectroscopy study was conducted on original wood, herbaceous biomass, holocelluloses, lignin and their chars, prepared at high temperatures in a wire mesh reactor, an entrained flow reactor, and a tubular reactor. The radical concentrations in the chars from the decay stage range up between 7·10¹⁶ and 1.5·10¹⁸ spins g⁻¹. The results indicated that the biomass major constituents (cellulose, hemicellulose, lignin) had a minor effect on remaining radical concentrations compared to potassium and silica contents. The higher radical concentrations in the wheat straw chars from the decay stage of pyrolysis in the entrained flow reactor compared to the wood chars were related to the decreased mobility of potassium in the char matrix, leading to the less efficient catalytic effects of potassium on the bond-breaking and radical re-attachments. The high Si levels in the rice husk caused an increase in the char radical concentration compared to the wheat straw because the free radicals were trapped in a char consisting of a molten amorphous silica at heating rates of 10³–10⁴ K s⁻¹. The experimental electron spin resonance spectroscopy spectra were analyzed by fitting to simulated data in order to identify radical types, based on g-values and line widths. The results show that at high temperatures, mostly aliphatic radicals (g = 2.0026–2.0028) and PAH radicals (g = 2.0027–2.0031) were formed.     

Experimental study on hydrogen-rich syngas production via gasification of pine cone particles and wood pellets in a fixed bed downdraft gasifier

The main objective of this research is to investigate gasification of pine cones particles and wood pellets in a pilot scale 10 kWth downdraft fixed bed gasifier using air as an oxidizing agent. In this work, it was found that syngas produced by gasification of pinecones particles is rich in environmentally friendly hydrogen and that would be a clean alternative energy carrier for the production of clean energy. In addition, the effect of gasification temperature and equivalence ratio on the composition of syngas and gasification performance for pine cones and wood pellet were analysed comparatively. During the experimental works gasification took place with air, in a temperature range of 701–1046 °C, for various air equivalence ratios (0.14–0.37) and under atmospheric pressure. It is found that H₂ and CO production increased by increasing reactor temperature. Another finding is that the mean cold gas efficiency was 65% for pinecone particles and 80% for wood pellet gasification.     

Neutron physics of the liquid‐fuel heat‐pipe reactor concept with molten salt fuel—Static calculations

A liquid‐fuel heat‐pipe reactor (LFHPR) is a novel fast heterogeneous reactor developed by Harbin Engineering University, China, on the basis of liquid‐fuel reactor designs and the heat‐pipe reactor concept. In the concept, the reactor abandons the graphite moderator and keeps neither fuel tubes arranged in the graphite nor fuel rings around the heat pipe. Instead, the reactor applies molten salt fuels, molten metallic eutectic fuels, or other fuels in liquid form. The heat generated in the reactor is removed by the heat pipes driven by liquid metals. With this change, an LFHPR is much more flexible in design and application and able to achieve several advanced features compared with conventional heat‐pipe reactors. In this paper, we describe the general reactor design of an LFHPR, discuss its potential advantages, and give a preliminary verification of the neutron physical feasibility for the reference case, which uses molten salt as the fuel, by using both Monte Carlo and deterministic methods. Results show that the LFHPR yields a hard neutron spectrum that brings a very good neutron economy and is a promising application for breeding. From our approach, we conclude that the proposed LFHPR has a very high power density and high negative temperature feedback coefficient.