考虑脱硫的电站温室气体排放计算模型改进

湿法脱硫(WFGD)工艺以石灰石作为吸收剂,制成石灰石浆液与烟气中的二氧化硫反应,生成的副产品为石膏。针对石膏—石灰石湿法脱硫对电站温室气体排放计算模型影响的问题,在燃烧方程的基础上重新建立计算模型。通过新的计算模型对采用石膏—石灰石湿法脱硫的燃煤电站锅炉CO2排放量进行计算分析。结果表明:新的计算模型适用于该电站锅炉CO2排放量的计算。由新的计算模型看出采用石膏—石灰石WFGD的燃煤电站锅炉要比采用干法脱硫的电站锅炉要多排放2(1-η)SO2的CO2,式中的η为烟气脱硫效率。针对该电厂锅炉进行计算,在机组负荷100%的情况下,二氧化碳每小时将多排放8.41t。     

撬装式注汽锅炉烟气脱硫脱硝装置的开发

为减少移动式注气锅炉烟气中二氧化硫及氮氧化物的排放,以11.5 t/h燃油注气锅炉为研究对象,通过撬装式脱硫脱硝装置的开发及现场试验,对注气锅炉烟气SO₂和NO_x的排放及现场环境因素等问题进行了研究。研究表明,采用氢氧化钠和双氧水作为吸收剂的脱硫脱硝装置能明显降低烟气中的SO₂和NO_x的浓度,其中SO₂脱除效率高于95%,NO_x脱除效率在65%以上;通过余热利用可有效降低系统的运行费用。撬装模式的开发,可有效解决设备移动性差、占地面积大、浆液补给困难等影响注气锅炉运行的问题。     

三炉一塔石灰石/石膏湿法脱硫在中小型热电厂的应用

为使现有2×75 t/h CFB锅炉和新建1×145 t/h CFB锅炉SO2排放达到GB 13223—2011和当地政府要求的100 mg/m3(标态)限值,在从技术、经济方面比较分析单炉单塔和三炉一塔的基础上,结合实际场地紧张的特点,选用三炉一塔石灰石/石膏湿法脱硫(WFGD)方式,对设计中遇到的问题(如是否设置烟气换热器、增压风机、烟气旁路等)采取针对性应对措施,并介绍了三炉一塔WFGD的运行效果。     

湿法氧化技术在燃煤锅炉启动阶段的脱硝应用

通过实验室试验研究了过硫酸钠(Na₂S₂O₈)溶液浓度、温度和pH等对NO脱除效率的影响。在某320 MW燃煤锅炉启动阶段添加过硫酸钠至脱硫系统使烟气中NO浓度在较短时间内满足环保排放要求,脱硝效率达到6.4%～47.4%。脱硫浆液分析结果显示过硫酸钠的添加对脱硫系统的运行无影响。     

基于多物流测试的循环流化床锅炉汞迁移和排放特性研究

在某额定蒸发量为410t/h的循环流化床(CFB)锅炉上对Hg的迁移排放特性进行了研究。采用OHM法对静电除尘器(ESP)前、后和湿法脱硫塔(WFGD)后烟气中的Hg进行了取样分析,分别对各电厂的入炉燃料、底渣、飞灰、石膏、脱硫废水、新鲜浆液和清洗水等进行了多物流取样测试,并建立了质量平衡。结果表明:Hg的质量平衡率为101.10%~117.58%,测试结果具有良好的可靠性;迁移至飞灰中的Hg最多,占总排放Hg的70.95%;有27.37%的Hg排放到大气环境中,且以气相元素Hg为主;ESP和WFGD对Hg的脱除效率分别为58.1%和36.2%,CFB电厂配备的ESP+WFGD装置对烟气中Hg的排放有很好的控制能力。     

混燃石油焦CFB锅炉汞排放特性研究

为研究烟煤与石油焦混燃的循环流化床锅炉汞的迁移排放特性,采用安大略法(OHM)对机组布袋除尘器(FF)前后和湿法脱硫装置(WFGD)后的烟气进行取样,并同时对入炉燃料、飞灰、脱硫浆液、清洗水、石膏和脱硫废水进行了取样并分析。通过汞的质量平衡核算得到了汞在燃煤副产物中的分配比例以及汞的迁移排放特性。结果表明:飞灰中排放的汞占总汞排放的62.31%,大约30.38%的汞排放到大气中。FF可以高效地脱除颗粒态汞,对总汞的脱除率可达67.36%。WFGD对可溶性的二价汞脱除性能较好,对总汞的脱除率达24.24%。单质汞的排放因子远大于氧化汞,说明电厂大气汞的排放主要以单质汞为主。     

450t/d垃圾焚烧锅炉设计特点和炉内污染物的控制

介绍了450 t/d垃圾焚烧锅炉的设计特点,分析了入炉垃圾、一二次风温以及高低温腐蚀对垃圾焚烧锅炉的影响;对降低污染物排放提出了相应的对策和措施,尤其对炉内控制二噁英、颗粒物、二氧化硫(SO₂)和氮氧化物(NO_x)的排放处理进行了分析。最后,对垃圾焚烧锅炉的设计和运行提出了相应的建议。     

石灰石抑制石油焦和煤混烧过程NO排放机理的研究

循环流化床(CFB)锅炉进行石油焦和煤混烧,是高效、清洁利用高硫石油焦的有效途径。混烧过程中,为满足SO₂排放要求,通常采用炉内添加石灰石的脱硫工艺,而该工艺会引起炉内氮氧化物浓度的变化。基于工业CFB锅炉投停石灰石NO_x“突降缓升”的实验现象,在实验室规模的20 kW CFB锅炉和立式管式炉中,结合机理实验、物相分析和Factsage计算的方法,明确了石灰石抑制NO排放的机理。结果表明：CFB内强烈的氧化还原交变气氛下,固硫中间产物CaS是抑制NO排放的关键物质;CaS不仅能够促进CO还原NO,而且自身参与了分解NO的化学反应而被消耗,且反应在低温下更容易进行。研究结论可为深挖CFB低氮燃烧潜力,实现炉内NO和SO₂的一体化脱除提供有价值的指导方案。     

三炉一塔石灰石/石膏湿法脱硫技术在热电厂的应用

正石狮热电厂2001年投产的2×75t/h CFB锅炉,以燃烧含硫量低(St,ar≤1%)的福建无烟煤为主。原采用运行经济、成本低廉的炉内添加石灰石脱硫方式,满足《火电厂大气污染物排放标准要求》(GB13223-2011)中排放限值200mg/Nm3要求。但难以稳定达到福建省政府燃煤发电锅炉SO2排放限值100mg/Nm3要求。因此对其进行脱硫改造,并与1台新建的145t/h CFB锅炉脱硫系统同     

基于TD—PLS模型预测前馈的垃圾焚烧锅炉脱酸自动控制策略研究与应用

针对垃圾焚烧锅炉半干法脱酸系统自动控制投运率低、控制效果差的问题,在分析脱酸系统运行特性的基础上,设计了一种以PID控制和模型预测前馈相结合的HCl-SO₂协同控制策略。采用以HCl排放浓度作为主要控制目标,SO₂排放浓度作为次要目标的串级PID协同控制策略。在串级PID控制的基础上,基于时间差分偏最小二乘法(TD—PLS)建立HCl排放浓度预测模型作为控制前馈。该控制策略应用于某500 t/d垃圾焚烧机组脱酸系统,实际应用效果表明：脱酸控制投入前,HCl排放浓度波动变化较大,小时排放均值范围20～40 mg/m³,小时排放均值浓度相对标准偏差(RSD)为15.95%。脱酸自动控制投入后,HCl小时排放均值范围在25～30 mg/m³,小时排放均值浓度RSD为6.22%。在协同控制作用下,HCl小时排放均值波动显著减小,单位锅炉蒸发量的石灰浆液消耗量由0.034 m³/t降低到0.027 m³/t,相比投运前降低了21%,在保证出口HCl和SO_2...     

440t_h CFB锅炉掺烧石油焦二氧化硫排放特性研究

在440 t/h大型循环流化床锅炉上进行了燃烧不同比例煤和石油焦混合燃料时二氧化硫排放特性的试验研究。研究了燃烧不同比例的混合燃料、炉膛温度、过量空气系数和钙硫摩尔比对二氧化硫排放特性的影响。研究结果表明,过量空气系数和钙硫摩尔比的增加可以降低二氧化硫排放浓度。存在一个最佳脱硫温度,二氧化硫排放浓度最低,对于各种混合燃料最佳脱硫温度应在830～850℃之间。     

大型燃煤电站锅炉脱硫塔脱硫效率的数值模拟

利用双膜理论建立了脱硫过程的理论模型,以国内某百万千瓦级火电机组烟气脱硫系统的脱硫塔为例进行了数值计算,分析了浆液pH值、入口SO2质量浓度、液气比、锅炉负荷、浆液液滴粒径、喷淋层投运方式及吸收塔塔径等参数对脱硫效率的影响,并与工程实际数据进行了比较.结果表明:数值计算结果与生产现场运行数据比较吻合;各喷淋层的脱硫能力不一样,第3喷淋层的脱硫能力最强,第2喷淋层和第1喷淋层的脱硫能力次之;脱硫效率随浆液pH值和液气比的增大而提高,随入口SO2质量浓度、锅炉负荷和浆液液滴粒径的增加而逐渐降低.     

液幕式双流程烟气脱硫塔内气液流动与脱硫传质性能的研究

对液幕式双流程脱硫塔的气液流动性能以及脱硫传质特性进行相关的实验研究.通过实验测试,提出烟气流量、浆液循环量、液气比值等主要参数对液幕式脱硫塔内的气液流动特性和脱硫效率性能的影响.实验发现,随着液气比增加,射流高度和气液两相流阻力系数相应增加;气相雷诺数增加时,射流高度相应增加而气液两相流阻力系数相应减小.浆液循环量和...     

Experimental study on desulfurization efficiency and gas–liquid mass transfer in a new liquid-screen desulfurization system

This paper presents a new liquid-screen gas–liquid two-phase flow pattern with discarded carbide slag as the liquid sorbent of sulfur dioxide (SO₂) in a wet flue gas desulfurization (WFGD) system. On the basis of experimental data, the correlations of the desulfurization efficiency with flue gas flow rate, slurry flow rate, pH value of slurry and liquid–gas ratio were investigated. A non-dimensional empirical model was developed which correlates the mass transfer coefficient with the liquid Reynolds number, gas Reynolds number and liquid–gas ratio (L/G) based on the available experimental data. The kinetic reaction between the SO₂ and the carbide slag depends on the pressure distribution in this desulfurizing tower, gas liquid flow field, flue gas component, pH value of slurry and liquid–gas ratio mainly. The transient gas–liquid mass transfer involving with chemical reaction was quantified by measuring the inlet and outlet SO₂ concentrations of flue gas as well as the characteristics of the liquid-screen two-phase flow. The mass transfer model provides a necessary quantitative understanding of the hydration kinetics of sulfur dioxide in the liquid-screen flue gas desulfurization system using discarded carbide slag which is essential for the practical application.     

低硫低负荷运行对FGD系统的影响分析

锅炉因一些特殊原因存在低硫低负荷长期运行情况,石灰石-石膏湿法脱硫系统对此工况的脱硫效 率并没有影响.但系统长期运行后会出现吸收塔入口堆积堵塞;浆液外排时间间隔长、浆液更新慢而引起浆液起泡,设备管道堵塞,喷嘴压力降低等.喷嘴压力降至0.044 MPa,RSF变化不大,液滴粒径D32:2 257 μm,大于设计值2 00...     

CFB锅炉炉内高效脱硫技术应用与运行管理

文中简述了某公司CFB锅炉采用的炉内脱硫系统工艺,对制约CFB锅炉炉内脱硫效率的石灰石选择、石灰石投入量和运行床温控制等进行了的总结,某公司的运行管理经验显示,这有助于CFB锅炉炉内脱硫系统的稳定运行和二氧化硫的达标排放,可为国内CFB锅炉机组提供借鉴。     

Biomass as a reburning fuel: a specialized cofiring application

Reaction Engineering International has performed a series of combustion tests to evaluate the potential for utilizing wood biomass as a reburn fuel for nitrogen oxides (NO_x) control. Reburning is an effective NO_x reduction technology that utilizes fuel injection above the main burner zone. Studies with other hydrocarbon fuels such as coal and natural gas as reburn fuels have shown that NO_x emissions can be reduced by more than 50–60% with about 15% of the heat input coming from the reburn fuel. Two different biomasses, a hardwood and softwood, were evaluated as reburning fuels and compared to coal and natural gas. The use of wood to reduce NO_x is attractive for several reasons. First, wood contains little nitrogen, as compared with coal which is also used as a reburning fuel. This results in lower NO_x production from fuel nitrogen species for wood. In addition, wood contains virtually no sulfur, so sulfur dioxide (SO₂) emissions are reduced in direct proportion to the coal replacement. Wood is a regenerable biofuel; when a fossil fuel is replaced by a biofuel, there is a net reduction in carbon dioxide (CO₂) emissions. Finally, since the reburning fuel is normally 10–20% of the total heat input, large quantities of wood are not necessary. Experimental results showed NO_x reductions of as high as 70% were obtained with approximately 10–15% wood heat input. The stoichiometric ratio in the reburn zone was the single most important variable affecting NO_x reduction. The highest reductions were found at a reburn stoichiometric ratio of 0.85. NO_x reduction fell to about 40–50% at slightly higher stoichiometric ratios (0.9x reduction was strongly dependent on initial NO_x concentration and only slightly dependent upon temperature, where increased temperature increased NO_x reduction. Finally, the experimental results suggest that wood is as effective as natural gas or coal as a reburning fuel. In addition, REI has completed computer simulations of a full-scale boiler to evaluate the conditions that maximize the NO_x reduction efficiency using biomass as the reburn fuel. Computer modeling of the TVA Allen Station Unit 3, a 265 MW_e cyclone-fired boiler, showed that NO_x reductions as high as 50–60% could be achieved within the constraints set by the boiler and operations. The most important parameters affecting final NO_x emissions are the cyclone barrel stoichiometry, residence time in the reburn zone, and mixing in both the reburn and overfire air zones. The combination of computer simulations and experimental programs has provided the engineers with the tools needed to optimize biomass as a reburn fuel to maximize NO_x reduction.     

Optimization of excess air for the improvement of environmental performance of a 150 MW boiler fired with Thai lignite

The results of an experimental study of the excess-air-dependent heat losses, as well as gaseous emissions (NO_x, SO₂ and CO), on a 150 MW boiler firing Thai lignite are discussed. The NO_x emissions were found to increase with the higher excess air ratios; the NO_x values in the flue gas (at 6% O₂) ranged from 257 to 325 ppm, whilst the excess air ratio varied from 1.06 to 1.32 at the economizer outlet. Owing to the highly-efficient operation of the flue gas desulfurization units, the SO₂ emissions from the unit were maintained at a relatively low level, 50–76 ppm for the above excess-air ratios, whereas they accounted for about 3100–3300 ppm at the inlet of the FGD units. The CO emissions were determined for the extremely low excess air ratios. Two approaches for the optimization of the excess air ratio were analyzed in this study. For the first, i.e. the conventional approach, the optimization was carried out based on minimizing the total excess-air-dependent heat losses. The second, the environmentally friendly approach, proposed in this work, was aimed at minimizing the “external” costs (or the costs of damage done by the boiler emissions to the environment and humans). As shown in this paper, the lignite firing at the optimal excess air results in a lower environmental impact by the boiler unit.     

A model analysis of clean development mechanisms to reduce both CO2 and SO2 emissions between Japan and China

It is necessary for Japan to support the development of desulfurization policies of China to solve global and local environmental problems. This study proposes a “double clean development mechanism” to reduce both CO₂ and SO₂ emissions at the same time. The purpose of this study is to investigate the consequences for both countries' energy economies of following double clean development mechanism between Japan and China. A dynamic optimization model is developed to estimate the effects of Japanese investments in China for carbon dioxide recovery-disposal and emission desulfurization technologies. The simulation results suggest that a double clean development mechanism can effectively mitigate the damage caused by SO₂ emissions because the clean development mechanism itself can reduce SO₂ emissions, e.g. by switching to fuels. However, China might not be willing to accept restrictions on SO₂ emissions. This study also examines whether China will be able to maintain high growth rates with a clean development mechanism under the CO₂ and SO₂ restriction. The analysis shows that increasing the upper limit of investment from Japan to China can enhance the economies of the both nations. The effect of nuclear power installation on economic performance is also investigated for the both nations.