石灰石煅烧产物活性分析

为有效利用小颗粒（~10 mm）石灰石,采用静态煅烧的方法对粒径为0.5~10 mm的石灰石进行煅烧,分析了煅烧温度、煅烧时间、石灰石粒径对煅烧产物活性的影响。结果表明煅烧温度和煅烧时间对石灰活性都有影响,煅烧温度低、时间短,石灰石煅烧不完全,石灰活性差;煅烧温度高、时间长,石灰石又容易过烧,石灰活性依然不高,且温度越高过烧出现的越快;石灰石在950 ℃煅烧60 min得到的产物活性最佳;石灰石粒径对煅烧产物活性有影响,石灰活性并未随着石灰石粒径的增大而呈现单一趋势,大致是先增大后减小,实验中石灰活性最佳的石灰石粒径是2~3 mm。     

循环捕集CO2后煅烧石灰石的硫化特性

ZEC(zero emission coal)系统中,粗煤气进入碳酸化/重整炉前需先脱除H₂S,提出利用经过多次碳酸化/煅烧捕集CO₂循环的煅烧石灰石(CaO)脱除H₂S,并研究循环碳酸化/煅烧次数、硫化温度、H₂S浓度和微观结构对循环CaO硫化特性的影响。结果表明,多次循环碳酸化/煅烧捕集CO₂后CaO仍具有较高H₂S吸收性能。前20次循环,CaO硫化转化率随循环次数增加迅速降低;20次循环后,CaO硫化转化率缓慢下降。硫化120 min后,未循环CaO的硫化转化率接近100%,而经历1、20和100次循环后CaO的硫化转化率分别为94%、81%和74%。H₂S浓度对循环CaO硫化性能影响较大。硫化温度(800～1000℃)对循环CaO的硫化性能影响较小,最佳硫化温度为900℃。随循环次数增加,CaO颗粒发生高温烧结,导致比表面积降低和20～150 nm内孔隙减少,而这是与H₂S吸收密切相关的孔隙,导致CaO硫化转化率降低。     

Reactivity of calcined limestone and dolomite with sulfur dioxide

Under the conditions prevailing in in-situ desulfurization of fluidized bed combustion two types of limestone and two types of dolomite were tested for their reactivity with sulfur dioxide. Experimental variables were sorbent size, sulfur dioxide concentration and reaction temperature. In general reactivity increased with temperature with activation energy ranging 15.9 to 19.5 kcal/mol for initial reaction rate. Reaction order with respect to sulfur dioxide was close to one and reactivity decreased with increase of sorbent size. With continuous feeding of coal and sorbent sulfur dioxide concentration in the effluent gas decreased with increase of Ca/S ratio.     

SO2 removal from flue gas with dry limestone

SO₂ removal from flue gas with an efficiency of over 90% can be achieved by the furnace limestone injection (FLI) process in combination with the recently developed ash recycle activation (ARA) process. The ARA process uses a mixture of fly ash and CaO sorbent that comes out of the furnace for further SO₂ removal. The dust is separated from the flue gas, treated with low pressure steam and then added to the flue gas again. The activation of the Ca compounds occurs during steam treatment. Capillary condensation occurs and aqueous electyrolyte solution reactions within the particle become effective. A differential particle model is formulated.     

循环流化床锅炉内石灰石脱硫研究进展

循环流化床（CFB）锅炉是燃用劣质煤的最佳设备，炉内石灰石脱硫具有操作简单、成本低等优势，但也存在脱硫效率不够高、石灰石利用率低等问题，在当前燃煤超净排放的背景下，有必要探索CFB内石灰石高效脱硫的理论和技术。本文综述了近年来石灰石脱硫研究的新进展，包括水蒸气对CaO硫化反应的影响及机理、石灰石同时煅烧硫化反应及模型等；介绍了近年来提出的改善炉内脱硫效果的方法，包括采用小粒径石灰石和吸收剂的活化等。着重介绍了石灰石同时煅烧/硫化反应新概念，阐述了CFB内石灰石可能无法完全热解的现象及原因，以及该反应的研究进展和需要继续开展的工作。介绍了CaO硫化反应模型的研究进展，并提出了石灰石同时煅烧硫化反应的随机孔模型，将石灰石煅烧、烧结和CaO硫化反应同时考虑在内，更精确地描述炉内石灰石反应的过程。指出研究者应重视炉内脱硫的真实反应过程，避免对CFB脱硫过程做过度简化，否则研究结论很难反映炉内脱硫的真实规律。     

Numerical analysis of a finite cylindrical pellet model in solid-gas reactions

A two-dimensional grain model has been developed to describe solid-gas reactions in a cylindrical pellet of finite length. The grains are assumed to be spherical. Numerical solutions of the model have been compared to infinite cylinder solutions, infinite slab solutions, and the approximate infinite cylinder and infinite slab solutions developed by Szekely et al. (Szekely J., Evans J. W. and Sohn H. Y., Gas—Solid Reactions. Academic Press, New York 1976). Pellet sizes and reactor conditions under which one or more of these solutions is valid have been indicated. The accuracy of the other models depends on whether they are to be used to determine rate constants from initial rate data or whether they are to be used to relate conversion to time.When the Theile-type reaction modulus σ_L = L[3(1 - ε₀)K/D_ear_g]^{$\text{1}\text{2}$}, has a value 2.2 with a cylinder half-length of L = 0.2 cm and a cylinder radius of R_p = 0.8 cm the conversion levels after about 8 min are 40% by an infinite slab model, 50% by the 2-D model and 65% by the approximate infinite slab solution. If one determines a rate constant from the initial slope of the rate curve, then the infinite slab model gives a value 14% high. The approximate infinite slab solution is inappropriate for the latter purpose. Similar results are obtained when the cylinder radius is much smaller than the half-length.Pellets with R_p/L > 4 or <0.25 can be described by infinite slab or infinite cylinder models, respectively, if the diffusional resistance is not large.     

Reaction of SO2 and NO2 with polymers

A number of polymers have been exposed to SO₂ and NO₂ gas under various conditions. Chain scission, crosslinking reactions, and changes in infrared spectra have been noted. All polymers suffer some deterioration, which may be considerable with exposure over long periods of time. Elastomers form a separate group, being appreciably more susceptible to these gases than saturated polymers; however, they are still more sensitive to ozone.     

三聚氰胺与SO2反应及再生行为

以固体有机胺三聚氰胺（MN）为脱硫剂,对MN与SO₂反应及再生行为进行研究。结果表明,烟气组成0.35% SO₂+5% O₂+N₂,40℃、4% MN（质量分数）条件下,MN可维持140 min脱硫率>99%,穿透硫容（出口SO₂浓度200 mg/m³）0.33 g SO₂/（g MN）。MN脱硫及再生产物XRD、FTIR、SEM及TG-MS等表征分析表明,MN与SO₂反应首先生成三聚氰胺亚硫酸盐,随后被烟气中的氧气氧化为三聚氰胺硫酸盐,加入0.1%对苯二胺可有效抑制三聚氰胺亚硫酸盐氧化;三聚氰胺亚硫酸盐在75~150℃可加热再生,三聚氰胺硫酸盐不能加热再生。烟气含5% O₂条件下,加入0.1%对苯二胺,三聚氰胺亚硫酸盐氧化率由36%降低至13%,150℃下再生2 h,再生率由58%提高至94%,MN抗氧二次脱硫性能优良。     

A method of evaluating limestone reactivity with SO2 under fluidized bed combustion conditions

The reactivity of limestone with sulphur dioxide has been evaluated during conditions similar to those existing in a fluidized bed combustor using a fixed-bed quartz reactor. The reactivity of up to 11 particle sizes of 2 limestones were evaluated, and an exponential decay function was found to best describe the rate behaviour versus conversion of CaO to CaSO₄. The two constants in the exponential decay approximation could both be expressed as functions of particle size. Subsequently, the limestone reactivity as a function of both size and conversion could be reasonably well described by a total of 4 to 6 constants. An analytical sulphur capture model for fluidized bed boilers (FBB) that incorporates this type of reactivity function is proposed.     

Analysis of reaction zone thickness in non-catalytic solid-gas reactions

An expression for determining the reaction zone thickness in a slab type solid pellet is derived based on the grain model for first order and isothermal reaction. It is shown that during reaction, the zone thickness remains constant for slab type pellets and varies for cylindrical and spherical shaped pellets. An approximate criterion is obtained from the expression for the applicability of the widely used shrinking core and homogeneous models. The expression is also useful for determining the rate parameters. The expression is found to be very satisfactory in predicting the experimental reaction zone thickness values and the activation energy value for the zinc sulphide oxidation reaction.     

Absorption of HCl by limestone in hot flue gases. Part III: simultaneous absorption with SO2

In this work, the simultaneous absorption of HCl and SO₂ with limestone was studied using thermogravimetry. The objective was to investigate the effects of the temperature and gas atmosphere on the absorption results. Special emphasis was placed on elucidating the formation of the molten phases while these gases were being absorbed. Partially reacted absorbent particles were examined using scanning electron microscopy and energy dispersive spectrometry to study the reaction patterns inside them. This research showed that the chlorination of both calcined and uncalcined limestone was considerably suppressed when simultaneous sulphation occurred. Furthermore, the experimental results indicated that limestone sulphation was significantly enhanced by the presence of HCl. The results for both the suppressed chlorination and enhanced sulphation were similar under all experimental conditions, i.e. for all the temperatures and gas atmospheres studied. Molten phases were observed to have been formed in the samples at both 850 and 650 °C, and our thermodynamic modelling results for the CaCO₃–CaSO₄–CaCl₂ system indicated that the system has a eutectic point at approximately 580 °C. The formation of molten product phases could explain the enhancement seen in SO₂ absorption, although it cannot explain the suppressed chlorination during the simultaneous absorption of HCl and SO₂. The results of this study suggested that the calcium chloride initially formed is consumed in a subsequent reaction with SO₂.     

Analytical prediction of conversion-time behaviour of gas-solid noncatalytic reactions

A procedure has been suggested for analytical prediction of conversion-time behaviour of gas-solid non-catalytic reactions which are first order with respect to the gaseous reactant but of any general form with respect to the solid species. Based on this method analytical solutions have been presente for some of the commonly encountered rate forms including the grain model. These solutions predict the behaviour of the system extremely well upto abou 50–70% conversion of the solid.     

硫酸钾催化环氧氯丙烷与三乙胺的反应研究

首次将硫酸钾作为催化剂,引入到环氧丙基三乙基氯化铵中间体的合成反应中。与无催化剂体系相比,催化下的反应速率大幅度提高,反应时间显著缩短。以环氧氯丙烷的转化率和产物中环氧基保留率的乘积作为中间体性能的评价指标,通过正交实验优化出最佳条件:甲醇水溶液为溶剂,反应温度50℃、n(硫酸钾)∶n(环氧氯丙烷)=0.010、n(三乙胺)∶n(环氧氯丙烷)=1.0、反应时间为1.5 h。该条件下,环氧氯丙烷的转化率可达92.02%,产物中环氧基保留率达到70.67%。可见硫酸钾用于催化环氧丙基三乙基氯化铵的合成反应是适宜的。     

水蒸气对煅烧石灰石碳酸化反应影响的实验与模型分析

利用热重分析仪,对比了不同反应温度、不同水蒸气浓度对煅烧石灰石碳酸化反应的影响。碳酸化反应温度在500℃时,反应初期水蒸气对碳酸化反应的影响并不明显,反应10 min之后,在含有1.5%、10%和20%(体积分数)水蒸气条件下碳酸化转化率比无水蒸气条件下转化率分别提高了19.8%、27.2%和30.5%。水蒸气的存在有助于提高碳酸化反应转化率,但随着水蒸气浓度的增加转化率增加幅度减小。利用随机孔隙模型,对产物层扩散阶段扩散系数及反应活化能进行了计算。高温条件下,气氛中含有1.5%的水蒸气使反应活化能从237.7 kJ·mol^-1降低到179.9 kJ·mol^-1,提高水蒸气浓度到10%和20%后,反应活化能从156.6 kJ·mol^-1降低到148.6 kJ·mol^-1。不同水蒸气浓度条件下,碳酸化反应存在两个明显特征:一是大约在550℃处存在一个明显扩散系数的斜率变化,这一温度与气氛中是否存在水蒸气无关;另一特征是随着反应温度的提高,水蒸气的促进作用减弱。依据实验和模型计算结果,推测了当反应处于产物层扩散阶段时水蒸气对碳酸化反应影响的作用机理。     

Application of the zone model to multiple noncatalytic fluid-solid reactions

The effect of intraparticle diffusion on the multiple gas-solid reactions occurring in a porous solid reactant is analyzed by the zone reaction model. In parallel reactions for gases and a consecutive reaction for the solid, the solutions of transient concentration profiles of two solid reactants are given by classifying three zones, viz. Reaction zone and reaction-diffusion zone and diffusion zone in the course of the reaction progression. As an example, the simultaneous reduction-sulfidation of porous iron oxide sorbent in the desuifurization from low BTU coal gases is analyzed by the present model. The Thiele modulus of the reaction governs the behavior of the moving boundary between the reaction zone and the diffusion zone. When the Thiele modulus tends to be infinite, the present model is consistent with the solutions based on the unreacted shrinking core model.