关于燃气加热炉低温腐蚀的原因与对策

低温腐蚀是困扰燃气加热炉安全运行与炉效提高的主要问题。以某石化公司120万t/a焦化加热炉为例进行了换热计算和腐蚀原因分析,提出了以下改进方法:①提高脱硫工艺温度,降低燃料中的H2S含量;②增加吹灰器;③降低烟气中的水含量;④调整好烟道挡板的位置;⑤控制烟气酸露点温度。     

丘东集气站燃气水露点的计算及系统的工艺改造

本文对丘东集气站加热炉燃气的水露点温度进行计算和分析,找出了燃气含水高的根源之所在,提出了对加热炉燃气系统进行工艺改造的方案并付诸实施,改善了加热炉的运行状况,保证了集气站装置的安全平稳运行.     

炼厂加热炉余热回收系统空预器低温腐蚀原因分析及技术改造

本文针对某大型炼厂芳烃装置加热炉余热回收系统空预器低温段酸露点腐蚀严重、排烟温度偏高等问题,进行原因分析。通过方案比选,选择组合式两相流空预器余热回收系统进行技术改造,项目成功运行,解决了低温段露点腐蚀的问题,并将排烟温度维持在120℃左右,降低加热炉能耗,提升稳定性和经济性。     

硫酸装置炉气露点对余热回收系统设计的影响

分析了硫酸装置中影响露点腐蚀的主要因素,以硫磺制酸、硫铁矿制酸和硫化氢湿法制酸项目提供的工艺参数为例,分别计算了通过余热回收系统设备的炉气露点,并从余热回收系统设备设计的角度提出防止露点腐蚀的措施。     

WSA湿法制酸工艺中酸露点的计算及应用

使用3个常用的公式对WSA湿法制酸工艺中主要部位的酸露点进行计算,并与托普索公司的试验数据进行对比。分析了烟气中三氧化硫含量和水蒸气含量对酸露点的影响。从避免酸露点腐蚀角度,对WSA湿法制酸工艺的设计、设备选型及生产运行提出了一些建议。     

生活垃圾焚烧烟气净化系统酸露点计算方法

生活垃圾焚烧电厂经过20多年的高速发展,烟气排放指标日趋严苛,对烟尘、SO2、NOx的脱除工艺在原有“SNCR炉内脱氮+半干法脱酸+干法脱酸+活性炭吸附+布袋除尘”的基础上,增加了低温SCR和湿法洗涤塔,不同的工艺路线,烟气中的酸露点计算方法也就不同,本文就目前垃圾焚烧厂常见的工艺路线,分别进行分析计算烟气酸露点。此计算方法也适用于水泥、火电等行业,为烟气酸露点的准确核算提供参考依据,指导实际工程应用。     

回收柴油和烟气余热降低加热炉燃料消耗

加热炉设计时,为考虑露点腐蚀或初投资限制等问题,排烟温度很难达到目前炼油企业节能考核指标,影响加热炉热效率.本文作者对大庆石化炼油厂常减压加热炉进行节能改造,采取同时回收柴油和烟气低温余热措施,降低了露点腐蚀,排烟温度达到了节能考核指标,热效率提高5%,节约燃料油气5000吨/年,一年即收回投资.随着余热回收技术的发展、热管传热技术的成熟,国家节能政策的要求,多利用余热提高加热炉效率势在必行.应大力开展加热炉节能改造,特别推荐回收装置低温余热加热冷风和回收烟气余热降低排烟温度的措施,减少排烟损失提高热效率.     

管式加热炉低温露点腐蚀的防护对策

烟气低温露点腐蚀是影响加热炉安全平稳操作和进一步提高热效率的障碍,本文通过介绍上海高桥800万t／a常减压装置常压炉改造中为防止低温露点腐蚀采取的措施,探讨加热炉深度余热回收时防止烟气低温露点腐蚀的方案选择。     

热管式空气预热器的设计

热管式空气预热器广泛应用于烟气的余热回收.在设计过程中,各排热管的壁面温度必须高于烟气的酸露点温度,以防止壁面被腐蚀.如果某排热管壁温低于烟气的酸露点温度,则需调整该排热管的几何参数以提高壁温至酸露点温度以上.本文提出并采用冷,热流体温度连续分布模型,导出了热管换热器换热量的表达式,并应用其对热管式空气预热器进行了调壁温设计.温度连续分布模型比已有的离散模型更为合理.利用连续分布模型给出了一个热管预热器调壁温设计实例,结果表明,该设计方法行之有效.     

超细飞灰对烟气酸露点与酸凝结的影响研究

准确预测燃煤锅炉尾部烟气的酸露点和酸凝结对深度降低排烟温度、保障尾部换热设备的安全高效运行十分重要。尾部烟气中存在的飞灰颗粒对酸露点和酸凝结液滴的发生有很大影响，不可忽略。考虑烟气中超细飞灰颗粒对酸露点和酸凝结的影响，提出了飞灰粒径对考虑局部凝结质量传输效果的酸露点和酸凝结迭代计算方法，实现了酸露点和壁面温度下酸凝结的准确预测。当飞灰粒径低于中肯半径（r_ash0）时，飞灰粒径对凝结率有显著影响；随着飞灰粒径的降低，硫酸蒸气、水蒸气以及酸液凝结率明显增加，尤其是硫酸蒸气凝结率；飞灰粒径越小，凝结越易发生。然而，过冷度超过30℃时，烟气中超细飞灰颗粒对低温壁面酸凝结的影响可以忽略不计。烟气携带而不被低温壁面捕获的凝结酸液量较少，烟气中超细飞灰颗粒对烟气酸蒸气的降低作用可以忽略不计。理论计算方法为分析现场酸-灰作用积灰层提供理论依据，对于优化燃煤锅炉尾部烟道的安全高效运行有重大指导意义。     

铝–油酸/正庚烷基纳米浆体燃料液滴着火燃烧特性

采用液滴悬挂法研究了正庚烷液滴、油酸/正庚烷混合燃料液滴、含20wt%纳米铝粉的铝–油酸/正庚烷基纳米浆体燃料液滴在不同温度下(600~800℃)的着火燃烧特性。用高速摄像机观测液滴进入管式电阻炉后的着火燃烧过程，使用热电偶记录液滴周围的气相温度变化，同时通过对应的温度曲线计算液滴的着火延迟时间。结果表明，纳米铝粉和油酸的添加均能降低正庚烷液滴的着火延迟时间。随温度升高，正庚烷、油酸/正庚烷混合燃料、铝–油酸/正庚烷基纳米浆体燃料液滴的着火延迟时间显著降低，但变化趋势逐渐趋于平缓。铝–油酸/正庚烷基纳米浆体燃料液滴的着火延迟时间与环境温度满足阿累尼乌斯方程。与纯正庚烷、油酸/正庚烷混合液滴的燃烧过程相比，铝–油酸/正庚烷基浆体燃料液滴的燃烧过程有显著差异，其燃烧经历3个阶段：正庚烷稳定燃烧阶段、正庚烷微爆炸阶段和表面活性剂微爆炸阶段。铝–油酸/正庚烷基浆体燃料液滴燃烧时间延长，火焰熄灭后又复燃，且燃烧过程中发生剧烈的火焰形变和铝颗粒溅射现象，大部分铝以团聚体形式在第三阶段完成氧化还原反应。     

Differences in the ignition characteristics of coal–water slurries and composite liquid fuel

The processes of the inert heating, ignition, and combustion of the drops of typical coal–water slurries and promising composite liquid fuel were experimentally studied with the use of high-speed (to 10⁵ frame/s) video recording facilities. The particles of brown and black coals with of sizes 80–100 μm were used as the basic components of the coal–water slurries and composite liquid fuel. Spent automobile oil (from an internal combustion engine) was also added to the composite liquid fuel (relative mass concentration, 0–15%). The characteristic stages of the processes of the inert heating and evaporating of liquid components and the ignition and combustion of coal–water slurries and composite liquid fuel (the initial radii of drops varied from 0.5 to 2 mm) were established. The ignition delay and complete combustion times of the drops of fuel compositions were determined under changes of the temperature of an oxidizing agent (air) in a range from 600 to 900 K at fluid velocities from 0.5 to 5 m/s. Representative temperatures at the centers of coal–water slurry and composite liquid fuel drops were measured at all of the established stages of the combustion initiation process. The necessary and sufficient conditions for the steady ignition of the drops of the test fuel compositions were recognized.     

石油焦与煤混烧特性及动力学

以石油焦与煤的混合燃料为研究对象,采用TG—DTG—DSC联用实验技术对混合试样进行了燃烧热重实验。分析了混烧特性曲线,计算了各个燃烧特性指数,并采用差减微分法Freeman—Carroll计算了燃烧反应动力学参数。结果表明：各混合试样均只出现一个位于高温区段的DTG曲线峰和方向向下的DSC曲线的热量释放峰,混合试样的燃烧过程主要是高温阶段焦炭的着火燃烧过程;混合试样s2,S3及S5热量释放相对较少且不集中,燃烧时间长且不完全;混合试样S4及S6的热量释放集中且时间短,燃烧释放的热量相对较多;烟煤含量最多的混合试样s6的着火特性、燃尽特性指数及综合燃烧特性参数均高于其它混合试样以及石油焦的各个相应值,且试样s6的可燃特性指数也大于石油焦的可燃特性指数;混合试样活化能均小于石油焦燃烧的活化能,混合试样比石油焦更易着火燃烧;只要石油焦与煤的混合比例适当,石油焦掺烧烟煤后的燃烧特性优于石油焦单独燃烧特性,此为解决石油焦难以单独燃烧利用提供了方法。     

Process simulation of natural gas steam reforming: Fuel distribution optimisation in the furnace

This paper describes a two-step method to simulate the natural gas steam reforming for hydrogen production. The first step is to calculate reforming tube length and fuel distribution with equilibrium approach associated with heat transfer. The second step is to calculate and validate reforming performance with kinetic model. A short-cut simulation of hydrogen plant has also been performed to calculate inputs for the reformer model, such as total flow rate and composition of mixed fuel burning in the furnace chamber. Heat transfer, especially radiative heat transfer, is the key role in the steam reforming technology, due to the high heat fluxes involved. For this reason, energy modelling of the furnace chamber has been performed. The simulation evaluates the most important design variables, as tubes height, maximum tube-wall temperature, and tube pressure drop. The heat flux profile can be selected to have suitable metal temperatures to lengthen the reformer tube life. The model calculates the design parameters for reforming tube and fuel distribution among burners.     

Catalytic combustion technology to achieve ultra low NOx, emissions: Catalyst design and performance characteristics

A catalytic combustion system has been developed which feeds full fuel and air to the catalyst but avoids exposure of the catalyst to the high temperatures responsible for deactivation and thermal shock fracture of the supporting substrate. The combustion process is initiated by the catalyst and is completed by homogeneous combustion in the post catalyst region where the highest temperatures are obtained. Catalysts have been demonstrated that operate at inlet temperatures as low as 320°C at 11 atm total pressure and conditions typical of high performance industrial gas turbines. The ignition temperature is shown to correlate with the specific catalytic activity of the washcoat layer over a rather broad range of activities. A reaction model has been developed that can predict ignition behavior from the measured catalytic activity.     

Implications of fuel selection for an SI engine: Results from the first and second laws of thermodynamics

The current work examines the detailed thermodynamics of the use of eight (8) fuels by an automotive, spark-ignition engine using a thermodynamic engine cycle simulation. The fuels examined were methane, propane, hexane, isooctane, methanol, ethanol, carbon monoxide, and hydrogen. Both overall engine performance parameters and detailed instantaneous quantities are determined for each of the fuels. Results include thermal efficiencies, heat transfer, and exhaust gas temperatures as functions of engine speed and load. In general, the overall engine results were similar for the various fuels. The second law results showed that, for the same operating conditions, the destruction of exergy during the combustion process ranged between about 8% (for carbon monoxide) and 21% (for isooctane) of the fuel exergy depending on the specific fuel. The differences of the exergy destruction during combustion appear to be related to the complexity of the fuel molecule and the presence (or lack) of oxygen atoms in the fuel molecule.     

Syngas combustion in a 500 Wth Chemical-Looping Combustion system using an impregnated Cu-based oxygen carrier

Chemical-Looping Combustion (CLC) is an emerging technology for CO₂ capture because separation of this gas from the other flue gas components is inherent to the process and thus no energy is expended for the separation. For its use with coal as fuel in power plants, a process integrated by coal gasification and CLC would have important advantages for CO₂ capture. This paper presents the combustion results obtained with a Cu-based oxygen carrier in a continuous operation CLC plant (500 Wth) using syngas as fuel. For comparison purposes pure H₂ and CO were also used. Tests were performed at two temperatures (1073 and 1153 K), different solid circulation rates and power inputs. Full syngas combustion was reached at 1073 K working at f higher than 1.5. The syngas composition had small effect on the combustion efficiency. This result seems to indicate that the water gas shift reaction acts as an intermediate step in the global combustion reaction of the syngas. The results obtained after 40 h of operation showed that the copper-based oxygen carrier prepared by impregnation could be used in a CLC plant for syngas combustion without operational problems such as carbon deposition, attrition, or agglomeration.     

燃烧法制备纳米ZnO及光催化降解甲基橙的研究

分别以甘氨酸和柠檬酸为燃料,Zn（NO3）2为氧化剂,采用燃烧法制备纳米ZnO粉体并采用模拟太阳光进行甲基橙光催化降解研究。XRD和SEM表征样品表明,燃烧法能简单、快速制备纳米ZnO粉体。研究表明,燃烧剂和氧化剂的配比以及反应温度对制备的纳米ZnO降解甲基橙效果有较大影响。Zn（NO3）2与甘氨酸之比为0．2～0．5（物质的量比）,反应温度为5000C;Zn（NO3）2与柠檬酸之比为1．5,反应温度为600℃进行反应制备得到的纳米ZnO降解甲基橙效果较好。降解实验的结果表明,纳米ZnO能有效地光催化降解甲基橙染料。以柠檬酸为燃料制备的ZnO样品,在1h内对10mg·L^-1甲基橙溶液的降解率为90％。     

Citrate–nitrate auto-combustion synthesis of perovskite-type nanopowders: A systematic approach

Citrate–nitrate auto-combustion synthesis is used to prepare an iron, a cobalt and a cerium-perovskite. The influence of different synthesis conditions on the combustion process, phase composition, textural and morphological properties is studied in detail by X-ray diffraction, nitrogen adsorption and scanning electron microscopy.Results show that the combustion intensity increases from iron, to cerium, to cobalt-perovskite. Conversely, the combustion intensity decreases and thus the safety and the gain of the combustion process increase by using high fuel/oxidant ratios, low pH values or combustion reactors with high heat dispersion capacity.High fuel/oxidant ratios increase particle size and may enhance dopant segregation. Low citric acid/metal nitrates ratios may cause precipitation of the most insoluble compounds or segregation of the dopant. High citric acid/metal nitrates ratios increase the formation temperature of the perovskite-type structure. Low pH values are deleterious for the phase composition and/or for the morphology of the final product, although at high pH values dopant segregation may occur.     

Chemical-looping combustion in a 300 W continuously operating reactor system using a manganese-based oxygen carrier

Chemical-looping combustion (CLC) is a method for the combustion of fuel gas with inherent separation of carbon dioxide. This technique involves the use of two interconnected reactors. A solid oxygen carrier reacts with the oxygen in air in the air reactor and is then transferred to the fuel reactor, where the fuel gas is oxidized to carbon dioxide and water by the oxygen carrier. Fuel gas and air are never mixed and pure CO₂ can easily be obtained from the flue gas exit. The oxygen carrier is recycled between both reactors in a regenerative process. This paper presents the results from a continuously operating laboratory CLC unit, consisting of two interconnected fluidized beds. The feasibility of the use of a manganese-based oxygen carrier supported on magnesium stabilized zirconia was tested in this work. Natural gas or syngas was used as fuel in the fuel reactor. Fuel flow and air flow was varied, the thermal power was between 100 and 300 W, and the air ratio was between 1.1 and 5.0. Tests were performed at four temperatures: 1073, 1123, 1173 and 1223 K. The prototype was successfully operated at all conditions with no signs of agglomeration or deactivation of the oxygen carrier. The same particles were used during 70 h of combustion and the mass loss was 0.038% per hour, although the main quantity was lost in the first hour of operation. In the combustion tests with natural gas, methane was detected in the exit flue gases, while CO and H₂ were maintained at low concentrations. Higher temperature or lower fuel flows increases the combustion efficiency, which ranged from 0.88 to 0.99. On the other hand, the combustion of syngas was complete for all experimental conditions, with no CO or H₂ present in the gas from the fuel reactor.