工业锅炉膜法富氧燃烧技术探讨

<正> 1 前言膜法富氧技术是70年代国际上兴起的用高分子膜将含氧浓度为21％的空气制成氧浓度较高的富氧空气技术。虽然传统的深冷空分法(制氧机制氧法)和分子筛变压吸附制氧技术较成熟,但在一定规模上,膜法富氧投资少、运行费用低。因此,各国都在积极研究、开发。英、     

富氧燃烧对不同气体燃料特性的对比分析

为有效利用工业副产煤气,改善锅炉低负荷稳定燃烧,现针对某动力厂燃气锅炉运行过程中水平烟道氧含量不满足运行条件的情况,采用助燃空气富氧燃烧方案,分析高炉煤气、转炉煤气和按9∶1比例混合出的混合煤气经助燃空气富氧后对烟道氧含量及其燃烧特性的影响。结果表明:助燃空气富氧增容后,排烟量与空气量均减少;转炉煤气、混合煤气以及高炉煤气在送风量不变的情况下,助燃空气分别富氧增容至27%、29%、33%时,可提高锅炉水平烟道氧含量,使其达到2%左右。燃气锅炉采用助燃空气富氧燃烧的技术方案,在实现工业副产有效利用的同时,极大程度地减少了污染物的排放。     

用于焦炉煤气重整合成气的管式透氧膜反应器的研制及其运行性能

采用热注浆法成功地制备了致密的混合导体BaCo0.7Fe0．2Nb0.1O3-δ（BCFNO）透氧膜管,应用在焦炉煤气中甲烷部分氧化制合成气反应中,可以利用透氧膜以空气为氧源和焦炉煤气中的甲烷反应制合成气,实现膜分离制氧和甲烷部分氧化反应的一体化。试验结果表明,当反应温度在875℃时,膜的透氧量为8．7mL／（cm^2·min）,焦炉煤气中甲烷的转化率可以达到94％以上,H2的选择性在90％左右。试验结果还表明,透氧膜管的性能可靠稳定,经过长时间的运行膜管没有出现破裂,在富氢焦炉煤气气氛下表现出很好的稳定性。     

富氧燃烧方法及其节能效果

所谓富氧燃烧,就是利用氧富化膜把燃烧所必须的空气中的氧富化成23％～28％的浓度,然后再参与燃烧的一种方法。本方法由松下技研株式会社、松下电器产业株式会社和大阪煤气株式会社共同研制。     

大功率柴油机磁法富氧燃烧技术探讨

富氧燃烧能够显著改善柴油机的动力性能与经济性,能够显著降低排放物中除氮氧化合物之外的污染物排放量。磁法富氧作为一种新的制备富氧空气的方法,较传统的膜法富氧方法相比,有不可比拟的优势,使用成本更为低廉。大功率柴油发动机使用磁法富氧技术的基本原理,通过柴油发动机的燃烧与排放理论对柴油机富氧燃烧的动力性能、经济性能与排放性能进行分析。探讨了大功率柴油机使用磁法富氧燃烧技术的可能性,得出利用磁法富氧技术与大功率柴油机进行结合研究有着重要的意义,并提出了大功率柴油机磁法富氧燃烧技术的理论模型。     

离子迁移膜氧（ITM）技术

据《Gas Turbine World》2008年1～2月号报道,现低温空气分离装置建造和运行的费用十分大,约占IGCC（整体煤气化联合循环）装置总投资费用的15％,并耗费约15％装置总输出功率。 DOE（美国能源部）正在进行的先进的IGCC技术计划继续把开发ITM（离子迁移膜）技术作为目标,以比低温空气分离装置更低的投资费用和能源消耗来生产氧。     

小功率供暖锅炉利用富氧供风的技术-经济性

据《Энергетика》2013年11-12月刊报道,白俄罗斯国立技术大学的专家研究和分析了小功率供暖锅炉利用富氧供风所取得的经济效益。分析表明,用氧气代替空气供风或大量使用富氧空气使气体燃料燃烧温度提高500-900℃,使火焰的辐射能力增加到原来的1.5-2倍,燃烧产物的体积减少到原来的1/2-1/3.5,并相应地使燃烧产物带走的热量减少到原来的1/2-1/3.5,进一步提高锅炉装置效率。上述性能数据为燃料在炉内的燃烧过程中广泛应用氧气创造了先决条件。     

LPG点燃式发动机冷起动首循环进气富氧试验研究

基于循环控制,详细研究了LPG点燃式发动机冷起动首循环进气富氧的燃烧及排放特性。试验在一台电控LPG进气喷射单缸风冷四冲程125 mL发动机上进行,采用膜式富氧方法实现富氧进气燃烧。研究表明:当过量空气系数大于0．7时,富氧进气燃烧缸压峰值与空气相比增加不显著,此后随混合气加浓,富氧进气燃烧缸压峰值开始明显大于常规空气进气燃烧;过量空气系数在0．4～0．876时,富氧进气燃烧与常规空气进气燃烧相比,HC排放没有较大降低,在此范围之外,富氧显著降低HC排放;过量空气系数在0．4～0．7,富氧与空气相比CO显著降低;富氧进气燃烧,使得首循环NO排放大幅增加;计算放热率发现,富氧燃烧速度比常规空气进气燃烧更快,放热更集中。     

220 t/h锅炉富氧燃烧改造及其系统分析

针对某220 t/hП型高压锅炉,综合考虑锅炉现有设备和系统的特点,根据方案简单易行、投资少以及同时兼顾空气燃烧和富氧燃烧等原则提出了富氧燃烧改造方案。为实现一次风和二次风的分离加热,改造方案采取将后三级受热面分仓隔离的方式。锅炉其他受热面保持不变。通过对不同的漏风形式采取相应的处理措施,确保改造方案的漏风率降至较低水平。对改造方案进行性能分析,结果表明:改造后的富氧燃烧条件下的锅炉热效率高于空气燃烧条件,富氧燃烧条件下的绝热燃烧温度低于空气燃烧条件约200℃,锅炉各级受热面的烟气侧出口温度均略低于空气燃烧条件,锅炉本体排烟温度高于烟气酸露点。     

应用于燃油锅炉的富氧空气助燃技术探讨

介绍富氧助燃技术,并论述该技术应用于燃油锅炉的节能减排效果。通过对燃烧过程进行热工分析得知,采用含氧浓度为28%的富氧空气进行助燃时,烟气排放明显减少,燃烧室理论温度可由1340K左右提高至1720K以上。在富氧空气气氛下,柴油燃烧速度也有一定提高。以常见的系统工艺及实际情况为例,对富氧空气助燃的经济可行性加以论述,并初步提出了技术改进方案。结果显示,采用富氧空气助燃技术可以达到节约能源、降低排放的效果。     

双调风燃烧器锅炉燃烧参数优化的试验研究

通过对双调风燃烧器锅炉影响燃烧的主要运行参数的试验研究,分析得了氧量,一次风量,燃烧器各挡板开度,磨煤机给煤量等主要燃烧参数对锅炉经济性的影响规律,并对这些参数进行优化选择,使锅炉的运行经济性得到了明显提高,试验得出的一些结果对同类型锅炉有一定的参考价值。     

煤富氧燃烧对节能与环境的影响分析

分析了煤富氧燃烧的节能效果及对环境的影响,煤富氧燃烧可显著减少助燃空气量、烟气生成量,显著节约能源,且有利于减少和控制SO2、CO2的排放,但会明显增加NOx的排放。     

An improved thermal control of open cathode proton exchange membrane fuel cell

Proton exchange membrane fuel cell is a well-known technology that has shown high efficiency and performance as a power system compared to conventional sources such as internal combustion engines. Especially, open cathode proton exchange membrane is growing more popular thanks to its simple structure, low cost and low parasitic losses. However, the open cathode fuel cell performance is highly related to the operating temperature variation and the airflow rate which is adjusted through the fan voltage. In this regard, the present study investigates the thermal management of an open cathode proton exchange membrane fuel cell. The objectives are the stack performance improvement and the stack degradation prevention. Indeed, a safety and optimal operating zone governed by the load current, the stack temperature and the air stoichiometry, is designed. This optimal operating zone is defined based on the system thermal balance and the operating constraints. Hence, the proposed control strategy deals concurrently with the stack temperature regulation and the air stoichiometry adjustment to guarantee the goals achievement. The performance of the proposed control strategy is verified through experimental studies with different operating conditions and results prove its efficiency. To properly design an appropriate control strategy, a multiphysic fuel cell model is developed based on acausal approach by mean of Matlab/Simscape and experimentally validated.     

燃尽风率对四角切圆锅炉燃烧及NOx生成特性的影响

对某电厂一台300 MW四角切圆锅炉低氮改造后的NOx生成特性进行了数值模拟计算,分析了燃尽风率对NOx生成特性的影响。分析结果表明:燃尽风率增大时,在主燃烧区喷入空气量减少,导致煤粉燃烧不完全、温度降低;燃尽区的富氧氛围使未燃尽的煤粉进一步完全燃烧;主燃烧区的还原性氛围使得该区域NOx会随着燃尽风率的增大而减少;燃尽区的高温以及较低的CO浓度降低了该区域的还原性氛围,使NOx排放量增加。综合考虑NOx排放和消旋效果,该炉型锅炉采用30%的燃尽风率是比较合理的。     

Simulation of methane conversion to syngas in a membrane reactor. Part II: Model predictions

A one-dimensional non-isothermal model was employed in the simulation of partial oxidation of methane to syngas in a dense oxygen permeation membrane reactor. The model predicts that if methane is consumed completely in the reactor, a temperature runaway occurs. The reactor inlet temperature is chosen as a major factor to demonstrate the correlativity of the reactor performance and this phenomenon. A borderline inlet temperature (BIT) is defined. Simulation results showed that when the reactor inlet temperature approaches this value, an optimized reactor performance is achieved. This temperature increases with the increase of the air flow rate and carbon space velocity. The surface exchange kinetics at the oxygen-rich side has a small effect on this temperature, while that at the oxygen-lean side has a significant effect.     

Bifunctional activation of a direct methanol fuel cell

We report a novel method for performance recovery of direct methanol fuel cells. Lowering of air flow rate below a critical value turns the cell into bifunctional regime, when the oxygen-rich part of the cell generates current while the rest part works in electrolysis mode (electrolytic domain). Upon restoring the normal (super-critical) air flow rate, the galvanic performance of the electrolytic domain increases. This recovery effect is presumably attributed to Pt surface cleaning on the cathode with the simultaneous increase in catalyst utilization on the anode.     

High performance PEMFC stack with open-cathode at ambient pressure and temperature conditions

An open-air cathode proton exchange membrane fuel cell (PEMFC) was developed. This paper presents a study of the effect of several critical operating conditions on the performance of an 8-cell stack. The studied operating conditions such as cell temperature, air flow rate and hydrogen pressure and flow rate were varied in order to identify situations that could arise when the PEMFC stack is used in low-power portable PEMFC applications. The stack uses an air fan in the edge of the cathode manifolds, combining high stoichiometric oxidant supply and stack cooling purposes. In comparison with natural convection air-breathing stacks, the air dual-function approach brings higher stack performances, at the expense of having a lower use of the total stack power output. Although improving the electrochemical reactions kinetics and decreasing the polarization effects, the increase of the stack temperature lead to membrane excessive dehydration (loss of sorbed water), increasing the ohmic resistance of the stack (lower performance).     

链条炉排横向燃烧不均匀及对策

链条炉排易发生横向燃烧不均匀的问题。通过进行原因分析，采用不均匀开孔的新型横向配风装置，改进了风室密封结构，同时采取均匀给煤的方法。为检验改进的链条炉排工作性能，对其进行了供风系统冷态性能试验，并对采用该炉排的锅炉进行热工试验及环保测试。结果表明，燃烧均匀稳定，提高了燃烧效率，取得显著的节能效果。     

An experimental study on vapor transport of a hollow fiber membrane module for humidification in proton exchange membrane fuel cells

Water management is key in the optimization of proton exchange membrane fuel cell performance and durability. Humidifiers can be used to provide water vapor to cathode air, ensuring the proper operation of proton exchange membrane fuel cells. In this study, water vapor transport characteristics of hollow fiber membrane modules were investigated in shell-tube humidifiers under isothermal conditions, using two different test jig constructions: a convection jig and a diffusion jig. The mass transfer rate of water vapor was evaluated via the impact of various operating parameters, including temperature, flow rate, pressure, and relative humidity of inlet wet air, flow arrangements, and surface area of the tube side. The result was presented by the water vapor transport rate from wet air flow to dry air flow across the hollow fiber membrane. It was found that humidification performance could be improved with higher operating temperature, flow rate, and relative humidity of inlet wet air, lower pressure, larger membrane surface area, higher convection effect, and substituting co-current with counter-current flow configuration.     

不同过量空气系数下射流点火发动机燃烧、排放和爆震特性的试验研究

基于单缸试验机研究了过量空气系数对射流点火发动机性能的影响。通过分析发动机性能曲线、缸内燃烧情况及爆震特性探究射流点火最佳运行区间,并与火花点火燃烧方式进行对比。结果表明,射流点火可以有效提升瞬时放热率并拓展发动机稀燃极限,缩短缸内混合气滞燃期与燃烧持续期,同时燃油经济性有一定提升。在稀燃条件下氮氧化物排放极低。爆震方面,随着点火提前角增大,射流火焰的多点点火效应会在缸内产生明显压力震荡,继续增大点火提前角会诱导末端混合气自燃。因此射流点火爆震缸压表现为两阶段压力震荡,爆震因子集中性高。提升过量空气系数可以降低射流点火爆震因子幅值,使发动机工作在轻微爆震或无爆震状态。