O2/CO2气氛下煤燃烧SO2/NO析出特性

在水平管式炉上研究了O₂浓度、CO₂浓度、温度及石灰石添加等各参数对O₂/CO₂气氛下徐州烟煤和龙岩无烟煤燃烧过程中SO₂/NO排放特性的影响。结果发现,O₂/CO₂气氛下,烟煤和无烟煤燃烧SO₂/NO的析出规律与空气气氛下不同,同等O₂浓度下析出量比空气气氛下小。O₂/CO₂气氛下,随着O₂浓度的提高,烟煤和无烟煤SO₂/NO排放量均增大;随着CO₂浓度的升高, SO₂/NO排放量均减小。O₂/CO₂气氛下,石灰石添加对SO₂排放的抑制作用低于空气气氛下;石灰石添加对NO的排放有一定减排作用。对煤灰的元素分析显示O₂/CO₂燃烧对SO₂的抑制主要是由于煤灰的自固硫能力增强,而对NO的减排作用则是促进燃料N向其他含N气体的转换。     

O2/CO2气氛下煤燃烧SO2/NO析出特性

在水平管式炉上研究了O₂浓度、CO₂浓度、温度及石灰石添加等各参数对O₂/CO₂气氛下徐州烟煤和龙岩无烟煤燃烧过程中SO₂/NO排放特性的影响。结果发现,O₂/CO₂气氛下,烟煤和无烟煤燃烧SO₂/NO的析出规律与空气气氛下不同,同等O₂浓度下析出量比空气气氛下小。O₂/CO₂气氛下,随着O₂浓度的提高,烟煤和无烟煤SO₂/NO排放量均增大;随着CO₂浓度的升高, SO₂/NO排放量均减小。O₂/CO₂气氛下,石灰石添加对SO₂排放的抑制作用低于空气气氛下;石灰石添加对NO的排放有一定减排作用。对煤灰的元素分析显示O₂/CO₂燃烧对SO₂的抑制主要是由于煤灰的自固硫能力增强,而对NO的减排作用则是促进燃料N向其他含N气体的转换。     

O2/N2、O2/CO2和O2/CO2/NO气氛下煤粉燃烧NOx排放特性

利用滴管炉研究了O₂/N₂、O₂/CO₂和O₂/CO₂/NO气氛下煤燃烧过程中NO_x的排放特性。实验结果表明,在O₂/N₂和O₂/CO₂气氛下,高温或高O₂浓度均使NO排放量增加。O₂/CO₂气氛下NO排放量比O₂/N₂气氛下NO排放量低大约30%～40%。在O₂/CO₂/NO气氛下,温度不同时,O₂浓度变化对NO排放量的影响规律不同,对循环NO降解的影响规律也不同。高温不利于循环NO降解。随停留时间的延长NO排放量出现两个峰值。     

煤在O2/CO2中燃烧的Nox释放规律

利用一维沉降炉,对3种煤在O₂/CO₂和空气两种气氛下燃烧NO_x析出特性进行了比较,分析了炉膛温度、过量空气系数对NO_x生成量的影响,并对O₂/CO₂气氛下NO_x的生成和破坏机理进行了分析.研究发现两种气氛下NO_x都有一个峰值出现,挥发分含量高的煤种峰值靠前, 挥发分含量低的煤种峰值靠后,O₂/CO₂条件下,峰值出现较空气条件下提前且有所下降;空气条件下NO_x的生成量随温度提高较快地增加,而O₂/CO₂气氛中NO_x的生成量随温度变化比较缓慢;在两种气氛下NO_x的峰值均随过量空气系数的增加而增加,高挥发分煤在O₂/CO₂气氛下NO_x峰值低于空气条件下峰值,而低挥发分煤则受影响较小.     

以煤焦混合物为燃料的循环流化床锅炉SO2排放特性

在工业运行的410 t·h^-1循环流化床锅炉上进行烟煤、70％烟煤＋30％石油焦和50％无烟煤＋50％石油焦的燃烧试验,研究了运行参数对SO₂排放特性的影响。结果表明,3种燃料均能达到良好的燃烧效果,炉内温度场分布均匀。在相同燃烧条件下,不同燃料SO₂排放量与其中的含硫量呈正相关关系。SO₂排放量随温度的升高先减小后增大,存在最佳脱硫温度;随钙硫比的增大而减小;随过量空气系数的增大而减小;随飞灰再循环量的增大而减小。对于不同种类的石灰石,大比表面积和高比孔容积的石灰石对SO₂有较好的脱除效果。考察了燃用不同燃料的最佳温度、钙硫比和过量空气系数,阐述了飞灰再循环和石灰石微观结构在循环流化床锅炉脱硫中的机理和作用,以期对循环流化床的设计和运行工作提供指导。     

基于低温联合脱除的中低温Hg形态转化机理

与其他燃煤污染物联合脱除是解决燃煤汞排放问题的有效手段,促进Hg⁰向Hg²⁺的形态转化可以提高现有污染物控制装置对燃煤汞排放的控制能力。应用汞形态转化实验台,在中低温条件下研究分析Cl₂、SO₂、H₂O以及 NO₂对Hg⁰氧化过程的影响机理,结果表明,中低温条件下,10 μl•L^-1Cl₂可以氧化90%以上的Hg⁰。SO₂对Hg⁰形态转化过程的影响呈现区间性变化,按照SO₂浓度由小到大可划分为3个区间,只有在第（Ⅱ）区间内SO₂浓度才能显著影响Hg⁰的形态转化过程。H₂O与Cl₂反应的生成物HCl可以氧化Hg⁰,但其在中低温条件下氧化Hg⁰的能力弱于Cl₂,使得H₂O的存在抑制了Hg⁰的形态转化。将NO氧化为NO₂后进行脱除是低温条件下联合脱除的重要路线,NO₂在分解过程中释放出自由氧原子可以将Hg⁰氧化为HgO,这增强了低温条件下汞与NO_x联合脱除的技术可行性。     

O2/CO2气氛煤焦的燃烧及其孔隙结构变化

采用热力工况与实际煤粉炉相近的沉降炉实验装置,制备了不同环境气氛下（O₂/N₂及O₂/CO₂气氛）、不同燃尽率的煤焦试样,并采用低温氮吸附仪和扫描电子显微镜测定了其孔隙结构和表面形貌。结果表明,在相同的操作条件下,相同O₂浓度的O₂/CO₂气氛下煤焦的燃烧速率较慢、燃尽率较低,各试样的孔比表面积和比孔容积均较小。两种气氛下燃尽过程孔结构参数（SBET和VBJH）均呈减小趋势,且在孔径变化较明显的区域内（<5 nm）在CO₂气氛下煤焦的孔径分布较小且与煤种相关。SEM图像显示CO₂气氛下的煤焦表面致密,孔隙较少,其定性结果与N₂吸附法的定量测量结果吻合较好。     

黑液水煤浆燃烧固硫特性及机理

为了解黑液水煤浆自身固硫特性及机理,采用热天平、试验炉和工业炉燃烧运行实验,定性定量比较了黑液浆与制浆原煤燃烧烟气SO₂排放特性,并通过对炉内典型燃烧灰样的能谱、电子探针和X射线衍射分析,对黑液浆燃烧固硫机理进行了深入研究。结果表明,与燃煤Ca基固硫机理不同的是,NaOH和Na₂CO₃是两种最主要的固硫剂,黑液浆燃烧产生的SO₂绝大部分被NaOH所吸收而固定在灰渣中,Na₂CO₃在炉内高温环境下经历的硫酸盐化过程也能吸收烟气中部分硫氧化物,固硫物相在灰渣中主要以无水芒硝、硫酸钠、钾芒硝的形态存在。     

化学链燃烧钙基载氧体CaSO4与CO在不同温度下的反应行为

基于热重和红外联用进行等温实验,探讨了化学链燃烧载氧体CaSO₄在CO气氛下的还原反应特性。研究发现：温度对CaSO₄还原反应历程和速率有显著的影响,在10％CO气氛下,温度低于900℃时,发生单一反应,CaSO₄的还原产物只是CaS,气相产物为CO₂;当温度高于950℃后,发生平行反应和连串反应组合成的多重反应,固体产物为CaS和CaO,而产物气中除了有CO₂,还存在SO₂和COS,且气相硫化物的析出以COS为主;随着反应温度的升高,CaSO₄与CO反应速率显著增加,而目标产物CaS在固体产物中所占的摩尔分数呈下降趋势;基于钙基载氧体化学链燃烧中燃料反应器温度不宜高于950℃。     

Pt/CeO2催化分子氧氧化脱除异辛烷中有机硫化物的研究

以空气作氧化剂,含硫1 000 g·g^-1的异辛烷为模型油,考察了Pt/CeO₂催化剂上反应温度、n（O₂）∶n（S）和空速对苯并噻吩氧化脱除的影响。结果表明,在300 ℃、n（O₂）∶n（S）=26.4和空速15.3 h^-1时,苯并噻吩脱除率达95%以上。300 ℃达到95%的硫脱除率时,Pt/CeO₂催化剂上不同硫化物的氧化脱除活性顺序为：正戊硫醇>叔丁基硫醚>苯并噻吩>噻吩>二苯并噻吩。反应后的油品及尾气经脉冲火焰光度监测器色谱(GC-PFPD)和色质联用仪(GC-MS)检测分析发现,SO₂是惟一含硫产物。在200 h的噻吩氧化反应测试中,转化率一直保持在95%,O₂利用率约40%,异辛烷损耗约0.2%,表明Pt/CeO₂催化剂在催化氧化脱硫中具有较好的活性和稳定性。     

Effectiveness of SO2 sorbents by thermogravimetry-combustion with coal

A new experimental method is described for non-isothermal thermogravimetry (TG) involving combustion of mixtures of sieved coal with sieved calcium-containing sorbents. This rapid TG method utilizes a baseline for TG combustion of coal alone, derives an equation that gives a semi-quantitative measure (±10% repeatability) of the coal's reactive sulphur retained by the sorbent, the extent of retention of S0₂ generated in situ during combustion varying with different sorbents. The method permits direct variation in separate experiments of the calcium-to-sulphur ratio during combustion and relative ranking of different sorbents by retention of reactive sulphur in combustion. Relative rankings are presented for three pre-calcined natural stones (two limestones and one dolomite); these results correlate with relative rankings from another TG method reported in the literature. It is suggested that this new method is useful for pre-screening the effectiveness of S0₂ sorbents considered for use in fluidizedbed combustion of coal.     

50 kt/a硫磺回收装置SO2排放情况分析及改造建议

介绍了中国石油天然气股份有限公司独山子石化公司炼油厂50 kt/a硫磺回收装置烟气SO2排放情况.重点分析了影响烟气SO2排放浓度的主要因素,包括净化尾气中硫化物含量高、尾气单元设备有泄漏等.为满足即将实施的《大气污染物综合排放标准》中ρ（SO2）不大于400 mg/m3的排放要求,提出新建1套100 t/h溶剂再生装置并使用高效脱硫剂,更换尾气换热器及泄漏阀门等技改措施和建议.     

煤/钙基载氧体化学链燃烧操作参数分析

化学链燃烧作为一种新颖的燃烧技术,在化石燃料燃烧释放能量的同时能够有效分离CO2。今以CO2为气化剂气化煤炭,基于Aspen Plus流程模拟软件,研究了煤/钙基载氧体化学链燃烧过程。结果表明,以CO2为煤气化剂,各反应器含水分少,可减少热损失。CaSO4载氧体具有载氧能力大以及反应活性良好等优点。气化炉中CO+H2含量随二氧化碳煤比增大逐渐增加后下降;随温度升高其含量先增加,后趋于平稳。燃料反应器中CO2+H2O含量随载氧体煤比增大,呈现先增大后减小的趋势;随温度升高其含量逐渐下降。空气反应器中CaSO4含量随空载比增大先增加后趋于平稳,随温度升高其含量趋于平稳后下降。气化炉中硫化物和氮化物含量随温度升高而下降,而燃料反应器和空气反应器中硫化物含量随温度升高增加趋势明显,氮化物含量变化不明显。最后确定了关键反应器操作参数:气化炉的二氧化碳煤比为1.8;燃料反应器的载氧体煤比为4.5;空气反应器的空载比为10.5和三反应器的操作温度分别为950、1000和1100℃。     

Interactions of CO, HCl, and SOx in pulverised coal flames

The effect of HCl and SO₂ on CO oxidation in pulverised coal flames was investigated experimentally and kinetically in an entrained flow combustion reactor. Two bituminous coals (German ‘Goettelborn’ and a Polish coal) were used as fuels with a feeding rate of 1 or 1.5 kg/h. HCl or SO₂ is introduced into the reactor premixed with the primary air. Experimental results indicate that HCl addition may inhibit CO oxidation in coal flames and increases CO emission. Reducing temperature in the reactor will enhance the inhibitory effect of HCl on CO oxidation. The measured CO profiles along the reactor height clearly show that the addition of HCl may inhibit CO oxidation. In the experimental range of SO₂ addition, the inhibiting effect of SO₂ on CO oxidation is less significant than HCl. A detailed kinetic mechanism is used to model the reactions, and the controlling reactions are analysed.     

煤泥与玉米芯混燃过程TG-MS研究

为了研究煤泥与玉米芯的混燃特性,利用热重-质谱(TG-MS)联用技术研究了煤泥、玉米芯单独及混合燃烧的着火、燃尽等特性,在线监测了气体释放物CO_2、SO_2和NO_2,并分析了其变化规律。结果表明,当升温速率为10℃/min时,煤泥中掺烧玉米芯可以使混合样品着火温度降低204.62℃,燃尽温度降低26.52℃,燃烧性能得到明显改善。随着升温速率提高,混合样品在挥发分析出燃烧阶段,以及固定碳燃烧阶段的燃尽温度和最大失重速率都相应提高,而混合样品的着火温度变化不大。各样品燃烧时,CO_2和NO_2释放峰与其燃烧失重峰对应。煤泥中掺混玉米芯燃烧,降低了SO_2气体的排放。     

In situ diagnostics of Victorian brown coal combustion in O2/N2 and O2/CO2 mixtures in drop-tube furnace

Experimental investigation of the combustion of an air-dried Victorian brown coal in O₂/N₂ and O₂/CO₂ mixtures was conducted in a lab-scale drop-tube furnace (DTF). In situ diagnostics of coal burning transient phenomena were carried out with the use of high-speed camera and two-colour pyrometer for photographic observation and particle temperature measurement, respectively. The results indicate that the use of CO₂ in place of N₂ affected brown coal combustion behaviour through both its physical influence and chemical interaction with char. Distinct changes in coal pyrolysis behaviour, ignition extent, and the temperatures of volatile flame and burning char particles were observed. The large specific heat capacity of CO₂ relative to N₂ is the principal factor affecting brown coal combustion, which greatly quenched the ignition of individual coal particles. As a result, a high O₂ fraction of at least 30% in CO₂ is required to match air. Moreover, due to the accumulation of unburnt volatiles in the coal particle vicinity, coal ignition in O₂/CO₂ occurred as a form of volatile cloud rather than individual particles that occurred in air. The temperatures of volatile flame and char particles were reduced by CO₂ quenching throughout coal oxidation. Nevertheless, this negative factor was greatly offset by char-CO₂ gasification reaction which even occurred rapidly during coal pyrolysis. Up to 25% of the nascent char may undergo gasification to yield extra CO to improve the reactivity of local fuel/O₂ mixture. The subsequent homogeneous oxidation of CO released extra heat for the oxidation of both volatiles and char. As a result, the optical intensity of volatile flame in ∼27% O₂ in CO₂ was raised to a level twice that in air at the furnace temperature of 1273 K. Similar temperatures were achieved for burning char particles in 27% O₂/73% CO₂ and air. As this O₂/CO₂ ratio is lower than that for bituminous coal, 30-35%, a low consumption of O₂ is desirable for the oxy-firing of Victorian brown coal. Nevertheless, the distinct emission of volatile cloud and formation of strong reducing gas environment on char surface may affect radiative heat transfer and ash formation, which should be cautioned during the oxy-fuel combustion of Victorian brown coal.     

Comparisons of pulverized coal combustion in air and in mixtures of O2/CO2

Pulverized coal combustion in air and the mixtures of O₂/CO₂ has been experimentally investigated in a 20 kW down-fired combustor (190 mm id×3 m). Detailed comparisons of gas temperature profiles, gas composition profiles, char burnouts, conversions of coal–N to NO_x and coal–S to SO₂ and CO emissions have been made between coal combustion in air and coal combustion in various O₂/CO₂ mixtures. The effectiveness of air/oxidant staging on reducing NO_x emissions has also been investigated for coal combustion in air and O₂/CO₂ mixtures. The results show that simply replacing the N₂ in the combustion air with CO₂ will result in a significant decrease of combustion gas temperatures. However, coal combustion in 30% O₂/70% CO₂ can produce matching gas temperature profiles to those of coal combustion in air while having a lower coal–N to NO_x conversion, a better char burnout and a lower CO emission. The results also confirm that air/oxidant staging is very effective in reducing NO_x emissions for coal combustion in both air and a 30% O₂/70% CO₂ mixture. SO₂ emissions are proved to be almost independent of the combustion media investigated.