垃圾衍生燃料在水泥窑分解炉内的减氮效应

将垃圾衍生燃料(RDF)作为替代燃料投加到水泥窑炉内进行高温焚烧，是水泥工业降低熟料生产过程中化石燃料消耗的主要技术手段之一。本文在管式炉中研究了粒径和助燃空气温度这两个因素对RDF热解燃烧气体组分的影响，并利用CFD软件模拟了RDF在分解炉内的减氮效应。研究结果表明：对不同粒径的RDF颗粒，总体上呈现出热解燃烧气体中CO、C_mH_n和H₂还原性小分子气体浓度随着助燃空气温度的升高而增加。基于华新某工厂的运行工况进行了CFD模拟计算，当RDF的粒径分布取<50 mm(占80%)，三次风温度为900℃时，过剩空气系数取1.2，燃烧室出口NO_x浓度小于280 ppm，减氮效果明显，与实际情况一致。     

铁浴反应器流场及温度场的数值模拟

以铁浴熔融还原工艺的铁浴反应器为研究对象,基于FLUENT软件,对反应器内流场及温度场进行了数值模拟,考察了侧吹和顶吹操作条件对铁浴熔池均混时间、铁浴上部空间气相组成及温度分布以及煤气二次燃烧率的影响.计算结果表明,铁浴熔池均混时间随侧吹喷枪倾角及插入熔池深度的增加均呈现先减小后增大的趋势.在本计算条件下,当侧吹倾角为50°,侧吹喷枪插入深度为0.3 m时,可获得最短的熔池均混时间.铁浴反应器上部空间煤气二次燃烧率随顶部热风喷枪的升高而增大,项枪距熔池液面距离每增加0.2 m,上部空间煤气二次燃烧率可提高约1.1%;随顶枪位置上移,氧气分布范围扩大,气体环流区也随之上移.     

循环流化床预热燃烧试验研究及数值模拟

循环流化床预热燃烧过程中,预热燃料在下行燃烧室的燃烧过程至关重要。为了研究预热燃料在下行燃烧室中的流动和燃烧特性,采用计算流体力学软件Fluent,结合试验手段,对不同二次风喷口配风方式下,预热燃料在下行燃烧室的燃烧过程进行试验及数值模拟,对比了不同配风方式下,流动特性、温度特性、组分浓度分布特性以及氮氧化物排放特性的差异。结果表明,预热燃料在下行燃烧室的燃烧过程中,二次风会卷吸烟气在下行燃烧室上部产生回流,稀释反应物,在中心喷口配风时回流区域更大。不同配风方式下,下行燃烧室中的温度分布不同。环形喷口配风时下行燃烧室中的温度峰值为1 459 K,而中心喷口配风时下行燃烧室的温度峰值为1 555 K,同时环形喷口配风时下行燃烧室的高温区域较小,温度分布更加均匀。环形喷口配风时,预热燃料和二次风的混合更加充分,高温煤气和空气的反应更加强烈,有助于燃料的着火及升温。而中心喷口配风时下行燃烧室顶部的CO和H_2等还原性气体浓度较高,有助于还原NO_x。同时较高的温度促进了气化反应,生成更多的CO和H_2,在燃尽风喷入前的区域形成还原性气氛,有助于进一步还原NO_x。二次风中心喷口配风时,更多的氮氧化物被还原,尾部烟气中的NO_x排放浓度为107×10~(-6),二次风环形喷口配风时,尾部烟气中的NO_x排放浓度为121×10~(-6)。     

空气冷却式煤粉燃烧室数值模拟研究

双锥煤粉燃烧室在小容量工业锅炉中广泛采用水冷却方式,但随着市场对高容量锅炉需求的增加,双锥燃烧室体积增大、数量增多,如仍采用水冷却的方式将导致安装困难、水系统复杂等问题,亟需开发新的冷却方式。空气冷却形式具有结构简单、预热后的空气可以增加煤粉的着火稳定性等优点,需要考察其首次应用于双锥煤粉燃烧室中的效果。为了确定空气冷却式燃烧室燃烧和壁面冷却情况,采用数值模拟技术对14 MW工业锅炉燃烧室和炉膛进行三维建模,得到50%和100%两种负荷下不同内外二次风配风比例下燃烧室内部燃烧情况、金属壁面温度、出口火焰形状和炉膛充满度。结果表明:控制总空气过量系数不变,随着内二次风比例的逐渐增加,燃烧室内的平均温度逐渐降低;50%负荷下金属壁面温度随二次风比例的增加逐渐降低,100%负荷下金属壁面温度先降低后升高,这是内二次风助燃燃烧和外二次风的冷却共同作用的结果。随着内二次风比例的增加,金属壁面的高温区域逐渐后移,集中于后锥出口区域;在50%负荷下内二次风量占总空气量比例为0.4时,金属壁面具有最高温度930 K,100%负荷下内二次风量占总空气量比例为0.2时,壁面金属最高温度835K,2个最高温度均出现在后锥收缩段,据最高温度推荐壁面材料选取0Cr18Ni9,2种负荷下最高温度出现时燃烧室内的内二次风配风量为2 600 Nm3/h,应尽量使内二次风远离此配风量;50%负荷下燃烧室平均温度、金属壁面平均温度及最高温度均高于100%负荷,是空气冷却结构需要重点考察的工况。随着内二次风比例的逐渐增加,火焰长度先增加后减小,当内二次风过小时,出口气速较小,外二次风具有向中心的速度分量,火焰主要集中在炉膛前部。随着内二次风比例的增加,出口速度增大,火焰变长变细。但随着比例的继续增加,外二次风的轴向速度变小,出口火焰的旋流强度完全由二次风决定,出口旋流强度的增大导致了火焰的变短变粗,在2种负荷下,火焰长度较长时,内二次风比例为0.4~0.5。内外二次风比例为0.5∶0.5时,燃烧室内燃烧情况和壁面温度均匀稳定,火焰在炉膛内的充满度最好,是2个考察负荷下均较适合的运行参数。     

糠醛渣热解特性及热解挥发产物对其燃烧烟气原位控氮作用

通常,具有高含氮资源禀赋生物质在能源化利用过程中需控制NO_x排放。解耦燃烧是可适用于高含水、高含氮燃料的低NO_x燃烧技术,其对NO_x生成的抑制效果优于其他燃烧技术。为揭示解耦燃烧中热解挥发产物的原位控氮潜力、发展双流化床解耦燃烧技术,以糠醛渣为原料,借助固定床装置和双流化床装置,分别开展其热解特性和双流化床解耦燃烧近实际工况模拟研究。具体地,首先在固定床反应器中考察糠醛渣在不同温度下的热解产物分布,继而借助双流化床反应器考察了热解在线挥发产物对热解半焦同步燃烧烟气中NO_x的还原效果。结果表明：在500~700℃热解温度区间内,随温度的升高,半焦产率逐渐减少,从45.2%下降到39.8%;气体产率呈明显上升趋势,从12.4%上升到22.5%,CO、CH₄、H₂等还原性组分产率增加显著;焦油产率略有降低,从15.9%降低到12.9%;水分产率变化不大。双流化床解耦燃烧实验中,糠醛渣热解挥发产物对热解半焦同步燃烧所产烟气控氮效果良好,热解挥发产物对半焦燃烧烟气NO_x减排效果主要受热解温度、二次风占比影响,总过量空气系数ER=1.3,热解温度600℃、二次风过量空气系数ER₂=0.5时,糠醛渣热解挥发产物对相同热解条件下生成的半焦燃烧（900℃,过量空气系数ER₁=0.8）所产烟气原位控氮效果达到最优,NO_x减排率为54.80%。这表明,可通过控制热解挥发分产物产率、氧化程度,充分发挥挥发分的NO_x还原能力,从而明显改善解耦燃烧原位控氮效果。     

内热式回转炉煤热解工艺的焦油产率与性质研究

研究了３ｋｇ／ｈ内热式回转炉煤热解工艺实验装置的热解温度、热解时间、煤粒度、煤气燃烧的空气过剩系统对焦油产率的影响,用正态分布函数模拟了初次焦油产率随热解温度的变化,用韦布乐分布函数模拟了焦油二次裂解率随气相温度的变化,对比了四种煤的焦油产率,分析了热解温度对焦油元素组成、馏分组成、中性油族组成等的影响。     

中氮造气燃烧室改造研究之一——炭粉粒的燃烧利用

这里发表的是使燃烧室室烟道煤在燃烧室内直接用二次空气燃烧利用的设计思想。     

低阶煤低温干馏炉中低温燃烧室温度场分布模拟及结构优化

用CFD Fluent 6.3软件对自主研发的与增收低温焦油炭化室相配套的褐煤热解旋流式低温燃烧室（1500 mm×200 mm×1500 mm）内温度场分布进行了模拟研究和结构优化,结果表明：在燃烧室内坐标为（?25,550,0）和（25,?550,0）处设计两个关于燃烧室中央轴对称半径为100 mm的130°圆弧形挡板,燃烧室内平均温度（755 ℃）满足褐煤低温热解需求（500～650 ℃）;Realizable k-ε湍流模型、P-1辐射模型和非预混燃烧模型适用于计算焦炉煤气和空气低温燃烧室内温度场分布,模拟计算结果与实验结果基本吻合,误差波动幅度为50～70 ℃,满足工业要求。     

民用解耦燃煤炉中的NO_x和CO同时减排

典型民用解耦燃煤炉具有底部连通的两个分别被称为热解室和燃烧室的并列炉膛,煤炭从热解室上部加入,空气通过热解室底部的倾斜炉排引入。结合煤炭燃烧过程中的氮转移路线与解耦炉中的气体循环流动特征,定性分析了民用解耦燃煤炉中的NO_x和CO同时减排机理,并在此基础上对配风和煤种等因素对NO和CO排放的影响进行了定量实验研究。结果表明,民用解耦燃煤炉特有的结构特征和通风方式有利于NO_x和CO的同时减排,解耦炉具与洁净型煤匹配可显著降低综合污染物排放。     

单颗粒油页岩热解产物影响因素试验研究

油页岩是我国重要的非常规油气资源,其开发利用对缓解我国能源短缺问题具有重大意义。油页岩灰分高,使油页岩热解过程中气相物质在颗粒内受到的传质阻力较大,影响热解产物的分布。搭建了单颗粒油页岩热解试验台,针对灰层传质阻力对单颗粒油页岩热解特性的影响进行试验研究,对油页岩热解过程提供更本质的理解,为热解模型搭建提供基础,重点探究颗粒粒径、热解温度等因素对热解产物分布的影响,得到不同气体流速、颗粒粒径和热解温度下单颗粒油页岩热解产物的分布。研究发现,气体流速对油页岩颗粒热解产物分布影响不大;随着颗粒粒径增加,热解一次产物在析出颗粒前,发生更多热解二次反应,通过复杂的热解二次反应使部分热解产物重新被固定于半焦中,导致产物中页岩油比例下降、气体比例增加。颗粒粒径越大,在高热解温度下热解二次反应越明显,导致粗颗粒热解产物中页岩油比例随热解温度的升高,呈先升后降的趋势,而细颗粒热解产物中页岩油的比例随着热解温度的增加而增加。     

Development of can-type low NOx combustor for micro gas turbine (fundamental characteristics in a primary combustion zone with upward swirl)

A low NO_x combustor for kerosene-fueled micro gas turbine based on a new concept was proposed, and the combustion characteristics of the prototype combustor were investigated. The new concept combustor consisted of primary and secondary combustion zones, and they were connected by a throat. A swirler was set between the primary and secondary combustion zones. In order to enhance the recirculation of burned gas in the primary combustion zone, the combustion air was introduced through the swirler and forced to flow upward to the combustor bottom, from where fuel spray was supplied through a nozzle. An optimum configuration of the primary combustion zone such as length of primary zone, swirler vane angle, diameter of throat, etc. were investigated to achieve high combustion stability and low emission in wide ranges of fuel flow rate and excess air ratio. The optimum value of each part in the primary combustion zone was found out by measuring fundamental combustion characteristics such as lean combustion limit, flame luminosity, exhaust gas composition and combustion gas temperature.     

CFB air-blown flash pyrolysis. Part II: Operation and experimental results

The main operational characteristics of a novel gasifier operating in the CFB mode are outlined in this paper, based on the experimental results from a total of 11 runs in the pyrolysis mode. The operation runs constituted the main experiments in the CFB reactor, carried out to derive meaningful mass balance and additional operational data for the CFB pyrolyzer. The experiments were conducted in varying operating conditions determined by the most important parameters, i.e., biomass flowrate, fluidizing gas flowrate, air factor, initial bed inventory), temperature in the CFB riser, vapor residence time and nominal air factor – or equivalence ratio, S_b.The results obtained showed that the reactor configuration successfully operated as a biomass fast pyrolysis system to maximize liquid yields reaching 61.50 wt% on a maf biomass basis, with the novel feature of providing for autothermal operation at 500 °C and with 0.46 s gas–vapor residence time, by utilizing the by-product char energy content in a single reactor. The reactor provides a very high specific throughput of 1.12–1.48 kg/h m² and the lowest gas-to-feed ratio of 1.3–1.9 kg gas/kg feed compared to other fast pyrolysis processes based on pneumatic reactors and has a good scale-up potential, providing significant capital cost reduction. Results to date suggest that the process is limited by the extent of char combustion. Future work should address resizing of the char combustor to increase overall system capacity, improve the solid separation and substantially increase liquid recovery.     

Experimental studies on a novel swirling fluidized-bed combustor using an annular spiral air distributor

This work reports studies on hydrodynamics as well as combustion and emission characteristics of a conical swirling fluidized-bed combustor (SFBC) using an annular spiral air distributor as the swirl generator. In the experimental study on a ‘cold’ SFBC model, hydrodynamic regimes and characteristics of an air-sand bed were investigated for variable bed particle size and static bed height. Depending on the superficial air velocity, the bed exhibited four operational regimes. Based on the results from the ‘cold’ hydrodynamic study, optimum bed characteristics (sand particle size and bed height) and the range of primary air were determined prior to the combustion tests. In the second part of this work, a conical SFBC was tested for firing 80 kg/h rice husk. During the combustion tests, swirl motion of a fluidized bed was induced by primary air injected into the bed through the air distributor and, also, sustained by tangential injection of secondary air into the bed splash zone. Radial and axial temperature and gas (O₂, CO, NO) concentration profiles in the reactor were obtained for 20-80% excess air. Effects of operating conditions on formation and decomposition of major gaseous pollutants (CO and NO) in the reactor are discussed. Both CO and NO were found to be reduced significantly in the bed splash zone, resulting in quite low CO and moderate NO emissions from the reactor. High combustion efficiency, 99.4-99.5%, is achievable when burning rice husk in the proposed conical SFBC at 80 kg/h feed rate and excess air of 40-80%.     

Test results of a catalytic combustor for a gas turbine

A catalytically assisted low NO_x combustor has been developed which has the advantage of catalyst durability. Combustion characteristics of catalysts at high pressure were investigated using a bench scale reactor and an improved catalyst was selected. A combustor for multi-can type gas turbine of 10 MW class was designed and tested at high-pressure conditions using liquefied natural gas (LNG) fuel. This combustor is composed of a burner system and a premixed combustion zone in a ceramic type liner. The burner system consists of catalytic combustor segments and premixing nozzles. Catalyst bed temperature is controlled under 1000°C, premixed gas is injected from the premixing nozzles to catalytic combustion gas and lean premixed combustion is carried out in the premixed combustion zone. As a result of the combustion tests, NO_x emission was lower than 5 ppm converted at 16% O₂ at a combustor outlet temperature of 1350°C and a combustor inlet pressure of 1.33 MPa.     

Combustion of Energetic Fuel for Ducted Rockets (I)

Energetic solid fuels composed of modified GAP (glycidyl azide polymer) propellants were formulated in order to obtain optimized combustion characteristics for variable flow ducted rockets. Burning rate in a primary combustor and the combustion efficiency in a secondary combustor were studied and evaluated as a function of the mixture ration of fuel and air. The energetic fuels consisting of – N₃ groups in its chemical structure burned very rapidly even though the combustion temperature was low when compared with conventional solid propellants for rockets. The pressure exponent of the burning rate was optimized to gain wide range of mass generation rate. The combustion gases generated in the primary combustor burned very efficiently in a secondary combustor. The effective specific impulse of the ducted rockets was obtained to be about 780 s.     

Coal combustion characteristics in a fluidized bed combustor with a draft tube

The effects of gas velocity to draft tube (3–6 U_m), bed temperature (800–900°C) and excess air ratio (0–30%) on the total entrainment rate, overall combustion efficiency and heat transfer coefficient have been determined in an internally circulating fluidized bed combustor with a draft tube. The total entrainment rate increases with an increase in gas velocity to draft tube, but decreases with increasing bed temperature and excess air ratio. The overall combustion efficiency increases with increasing excess air ratio, but decreases with increasing gas velocity to draft tube. The overall combustion efficiency obtained in internally circulating fluidized beds was found to be somewhat higher than that in a bubbling fluidized bed combustor.     

Flow regimes and combustion behaviour in coal-burning spouted and spout-fluid beds

A study of coal combustion was carried out in a 0.15-m diameter half-column spout-fluid bed combustor, in which a sub-bituminous Alberta coal was burned in inert beds of sand. High temperatures promoted spout instability leading to earlier appearance of pulsatory spouting, the jet-in-fluidized-bed regime, and slugging than for room temperature operation. While radial temperature profiles below the bed surface were quite uniform, axial profiles showed a significant temperature jump in the fountain region above the bed surface. Axial profiles of oxygen concentration fell abruptly at the bed surface due to rapid burning there. The size of inert particles and the amount of auxiliary air were found to influence the hydrodynamics and combustion behaviour.     

A new type of coal gas fueled chemical-looping combustion

A new type of coal gas fueled chemical-looping combustion is experimentally investigated by means of a fixed-bed reactor operated at elevated pressure. Chemical-looping combustion may be carried out in two successive reactions between two reactors, a reduction reactor (coal gas with metal oxides) and an oxidation reactor (reduced metal with oxygen in the air), which may lead to a breakthrough in clean coal technology by simultaneously allowing efficient use of energy and greenhouse gas control. We have experimentally examined the kinetic behavior between solid looping materials and coal gas in a high-pressure fixed bed reactor. On the basis of the development of suitable material and the good reactivity with the fixed bed reactor, we have identified that the coal gas fueled chemical-looping combustor has much better reactivity than natural gas combustors, and this phenomenon is completely different from direct combustion with natural gas. The promising results obtained here will be valuable for the design of a practical reactor.     

移动床中内构件对煤热解反应过程调控作用

在外热式内构件（多级折流板和多段集气管）移动床反应器内研究了淖毛湖煤的热解特性,并与常规固定床反应器中煤热解行为进行对比,考察了两反应器内的传热速率以及热解温度对产物分布、热解气组成、焦油组成和品质等影响规律。结果表明：在450℃低温热解时,煤颗粒在内构件移动床内的升温时间比固定床缩短了60%以上,内构件具有显著提高反应器内颗粒间传热速率的作用。随着热解温度的升高,热解气中的C₂H₄/C₂H₆和C₃H₆/C₃H₈的比值变大,挥发分的二次反应程度加大,但裂解程度低于固定床。内构件移动床中的焦油产率随温度的升高先增加后降低,在550℃时达到最高为10.8%（质量分数）,比固定床增高约28.6%。当热解温度越高时,移动床所产焦油中的沥青质组分含量越低,在750℃时焦油中轻质组分质量分数达到85.17%,脂肪烃含量降低到了28.00%。通过与固定床对比,揭示了内构件（多级折流板和集气管）调控淖毛湖煤热解反应并提高热解焦油产率和品质的作用。