STRUCTURE OPTIMIZATION OF A CIRCULATING MOVING BED REACTOR

A stress distribution model for a liquid-solid circulating moving bed reactor that consists of a bottom reaction chamber, a top regeneration chamber, a coupling standpipe, a particle transportation system, and a bottom standpipe is established based on the equations of continuity and momentum balance. Simulations show that the stress concentration regions are at the bottom of the regeneration chamber and the coupling standpipe. To reduce the maximal stress and increase the operation flexibility in a reactor for the 2000-ton-per-year production of linear alkylbenzene, the regeneration chamber should have a low height-to-radius ratio (about 9), a suitable half-conical angle between 28° and 35°, and standpipe radius of about 0.05 m.     

Study on the stress distribution and modeling of the stand pipe in a circulating moving bed

The liquid-solid circulating moving bed reactor is a novel one, which consists of two reaction chambers and a particle transport system. Particles move down to the lower reaction chamber from the upper reaction chamber through a coupling standpipe and to the particle transport system through a bottom standpipe, and are then conveyed into the upper reaction chamber through a riser. A stress distribution model based on the equations of continuity and momentum balance in the reactor is established and used for simulations which shows that the stress concentration regions are at the coupling standpipe and the bottom of the regeneration chamber. To reduce the largest stress in the stress concentration regions and to minimize catalyst consumption, the regeneration chamber should be designed to give a low ratio of height to diameter. Zoning diagrams of the flow patterns in the bottom standpipe are proposed and the flow patterns can be readily deduced from the pressure gradient.     

循环流化床煤燃烧/热解双反应器系统稳定性分析

为了考察循环流化床煤燃烧/热解双反应器系统的稳定性,在冷态实验装置上以电厂锅炉灰为实验物料,其中提升管的内径为100 mm,高为6.7 m,与热解室相连立管的内径为44 mm,高3 m,热解室的截面积为200 mm×200 mm,高770 mm。分别考察了影响系统稳定运行的主要因素,并对系统中存在的几对平衡关系进行了分析。结果表明,旋风料腿内的固体料位高度、热解室内的料位高度以及热解室内的压力等是影响系统稳定运行的关键因素,尤其是热解室内压力的增加有可能使立管内料封破坏,最终导致系统瘫痪。而提升管与热解室立管之间压力的平衡以及提升管与旋风分离器料腿之间压力的平衡等在操作过程中必须保持稳定,否则也会发生窜气、架料、旋风分离器效率下降等现象,影响系统稳定运行。     

CFB煤燃烧／热解双反应器立管内气固流动模型分析

在循环流化床（CFB）煤燃烧／热解双反应器冷态实验装置上,以硅胶和电厂锅炉灰为实验物料,考察了立管内的气固流动特性,其中立管的内径44mm、高3m。研究结果表明,立管内的气固流动形态为移动床流动,Leung的立管流动模型适合对该系统中立管内移动床流动的描述,经拟合分别得到了立管内气、同速率以及气同相对速率与固体速率之间的经验方程,对热态实验过程中判断立管内的气固流动型态以及料封的稳定性均具有一定的参考价值。     

负压差立管内的气固两相流

在φ800 mm×12000 mm流化床实验装置上对150 mm×11500 mm负压差立管内气固两相流的轴向压力、空隙率和气体流动特性进行了测量和分析.立管出口无约束淹没在密相流化床内,颗粒质量流率范围G_s<1200 kg&#8226;m^-2&#8226;s^-1.立管内气固两相流态有两种存在形式,当颗粒质量流率G_s<200～250 kg&#8226;m^-2&#8226;s^-1时,流态是稀密两相共存形式;当G_s>200～250 kg&#8226;m^-2&#8226;s^-1时,流态是浓相输送流态.两种流态之间可以相互转换,主要取决于颗粒质量流率的变化.影响立管内气固两相流的轴向压力、空隙率分布、气相的流动特性和气固流态存在形式的主要参数是颗粒质量流率G_s、旋风分离器入口速度V_i、下端流化床流化速度u_f,质量流率G_s是主要的影响因素.     

Determination of standpipe pressure profiles and slide valve orifice discharge coefficients on synthol circulating fluidized-bed reactors

A Synthol Circulating Fluidized-Bed (CFB) reactor utilizes a finely divided, reduced iron oxide catalyst to convert (CO + H₂) to gaseous and liquid fuels. The reactor consists essentially of a fast-fluidized bed with a hopper and standpipe providing a pressure seal sufficient to maintain a high catalyst inventory in the reaction zone. For optimum reactor operation, the catalyst must flow down the standpipe in the dense-phase fluidized-flow regime so giving maximum pressure recovery.Tests carried out on the Sasol 1 commercial reactors showed that the dense-phase flow regime could be maintained with minimal use of added aeration. Work carried out on a large cold-model hopper and standpipe showed that added aeration was vital in maintaining dense-phase flow and in achieving a high pressure recovery. The relatively high pressure operation of the commercial reactors and consequent low compression effect going down the standpipe is such that the entrapped aeration entering the standpipe is sufficient to prevent a flow regime transition to a packed bed. Orifice discharge coefficients determined on the commercial reactors and the cold model agreed closely with values reported in the literature.     

Optimization of Reaction Conditions and Regeneration Procedure of the PdSb/TiO2 Catalyst for Acetoxylation of Toluene

The catalytic activity of a PdSb/TiO₂ catalyst for the acetoxylation of toluene to produce benzyl acetate was investigated. The reaction was carried out in a fixed bed Hastelloy^® C reactor. The effects of various reaction parameters such as reaction, temperature, space velocity, acetic acid, toluene (Tol), and oxygen concentration in the feed mixture on the catalytic performance were examined and optimized. Interestingly, this catalyst sample displayed reasonably good performance (X-Tol = 54% and S-BA = 91%) with significant decrease in induction period and improved long-term stability compared to previously used catalysts. In addition, regeneration of the catalyst was also carried out at different temperatures in the range from 250 to 400 °C in air. Effective regeneration of the catalyst was achieved at 300 °C; temperatures higher than 300 °C revealed to be not suitable. Furthermore, the duration of regeneration has also been optimized. Doing this, suitable regeneration procedure was established for effective restoration of activity that is lost during the process of deactivation.     

催化裂化装置待生立管磨损原因分析及处理措施

对催化裂化装置同轴式沉降再生器待生立管磨损原因进行分析,认为原设计不合理是主要原因,对待生立管及密封结构进行了改进。     

Fracture toughness of reactor graphite at high temperature

By means of a disk test, fracture toughness values of reactor graphite are measured at high temperature up to 2600°C. In the disk test in which a circular disk with a central crack is compressed diametrally, the stress intensity factor is analyzed with due consideration of the Hertzian contact by compressive anvils. As specimens, all the four kinds of isotropically molded and anisotropically extruded graphite are measured. The results obtained about fracture toughness values are found to increase with increase in temperature. At 2000°C, for instance, the values indicate figures about 1.5 times that of the room temperature. From the tensile properties up to 2400°C, the equivalent lengths of cracks and sizes of plastic zones have been deduced and have been discussed in their temperature dependencies.     

Analysis of chemical intermediates from low-temperature steam gasification of biomass

A reactor system was developed to study the process of lignin and biomass gasification at low temperatures (100 °C to 350 °C) and high pressure (up to 375 atm). The reactor allowed for withdrawal of samples from either the top or bottom of the reaction environment throughout the period of the experiment while maintaining the reaction temperature and pressure. An analytical method was developed for separating and standardizing the initial decomposition products formed during steam-alkali gasification of kraft pine lignin and Douglas fir wood flour.     

Performance of a ZVI‐UASB reactor for azo dye wastewater treatment

BACKGROUND: Zero valent iron (ZVI) is expected to be helpful for creating an enhanced anaerobic environment that might improve the performance of the anaerobic process. Based on this idea, a ZVI packed upflow anaerobic sludge blanket reactor (ZVI‐UASB) was developed to enhance azo dye wastewater treatment. RESULTS: The ZVI‐UASB reactor was less influenced by a decrease in the operational temperature from 35 °C to 25 °C than a reference UASB reactor that did not contain ZVI. In addition, chemical oxygen demand (COD) and color removal efficiencies of the ZVI‐UASB reactor at an HRT of 12 h exceeded those of the reference reactor at an HRT of 24 h. The hydraulic circulation in the ZVI bed enhanced the function of ZVI so that it improved the COD and color removal efficiencies. Moreover, fluorescence in situ hybridization experiments revealed that the abundance of Archaea in the sludge of the ZVI bed was significantly higher than that at the reactor bottom, which made the reactor capable of greater COD removal under low temperature and short HRT conditions. CONCLUSION: This ZVI‐UASB reactor could adapt well to changes in the operational conditions during wastewater treatment. Copyright © 2010 Society of Chemical Industry     

Materials Challenges in Reverse‐Flow Pyrolysis Reactors for Petrochemical Applications

Currently, the pyrolysis of hydrocarbons for the production of light olefins is almost exclusively carried out in steam crackers operating around 900–1000°C. However, cracking hydrocarbons at much higher temperature results in high selectivity to acetylene, which can be converted into many petrochemical products including ethylene. The desired hydropyrolysis reaction from hydrocarbons to acetylene can be realized in a reverse‐flow reactor at very high temperatures (>1700°C) in a scalable manner. The reactor elements include ceramic components that are placed in the hottest regions of the reactor and must withstand a temperature that is in the range of 1500–2000°C. In addition, the temperature rises and falls with the reverse‐flow cycle; a fluctuation that could be as high as 100–500°C over a period of several seconds. Moreover, the materials in the hot zone are exposed alternately to a regeneration (heat addition) step that is mildly oxidizing, and a pyrolysis (cracking) step that is strongly reducing with a correspondingly high carbon activity. This article addresses the thermodynamic stability of selected ceramic materials based on alumina, zirconia, and yttria for such an application. Results from laboratory tests involving the exposure of these ceramic materials to simulated process conditions followed by their microstructural characterization are compared with expectations from thermodynamic predictions.     

Effect of Regeneration Temperature on the Composition and Carbon Dioxide Sorption Ability of a K2CO3/Al2O3 Solid Sorbent in a Bubbling Fluidized Bed Reactor

The effect of the regeneration temperature (150°, 250°, and 350°C) during multiple CO₂ cyclic sorption-regeneration cycles of a K₂CO₃/Al₂O₃ solid sorbent in a bubbling fluidized bed reactor was evaluated in terms of the CO₂ capture capacity and chemical composition of the solid sorbent. The CO₂ capture capacity after regeneration at 150° and 250°C decreased with increasing cycle numbers, reaching approximately 57 and 78%, respectively, and 19.0 and 39.3%, respectively, of the original capacity after one and five regeneration cycles. This decline in the CO₂ capture capacity was due to the accumulation of KHCO₃ (at 150°C) and KAl(CO₃)₂(OH)₂ (150° and 250°C) from their incomplete degradation back to the K₂CO₃/Al₂O₃ solid sorbent. When regenerated at 350°C, the CO₂ capture capacity remained essentially constant in each cycle number because of complete desorption (no residual KHCO₃ and KAl(CO₃)₂(OH)₂). The formation mechanism of complex structure occurred similar to the one in a fixed bed reactor/thermogravimetric analyzer with lower regeneration temperature. The general operation conditions for K₂CO₃/Al₂O₃ solid sorbents are summarized.     

Carbon dioxide separation and dry reforming of methane for synthesis of syngas by a dual‐phase membrane reactor

High‐temperature CO₂ selective membranes offer potential for use to separate flue gas and produce a warm, pure CO₂ stream as a chemical feedstock. The coupling of separation of CO₂ by a ceramic–carbonate dual‐phase membrane with dry reforming of CH₄ to produce syngas is reported. CO₂ permeation and the dry reforming reaction performance of the membrane reactor were experimentally studied with a CO₂–N₂ mixture as the feed and CH₄ as the sweep gas passing through either an empty permeation chamber or one that was packed with a solid catalyst. CO₂ permeation flux through the membrane matches the rate of dry reforming of methane using a 10% Ni/γ‐alumina catalyst at temperatures above 750°C. At 850°C under the reaction conditions, the membrane reactor gives a CO₂ permeation flux of 0.17 mL min^?1 cm^?2, hydrogen production rate of 0.3 mL min^?1 cm^?2 with a H₂ to CO formation ratio of about 1, and conversion of CO₂ and CH₄, respectively, of 88.5 and 8.1%. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2207–2218, 2013     

Effect of adding different silane coupling agents on metal friction and wear in mixing process

The function of silane coupling agent in rubber mixing field is to combine inorganic matrix with rubber organic matrix. Silica is commonly used in the rubber mixing field to strengthen rubber. The size and amount of silica aggregates in the mixing process are important factors affecting the wear of the mixing chamber. The wear of the mixing chamber would lead to a increasing gap between the mixer chamber and the rotor, which caused the mixing efficiency reducing. It also affected the dispersion effect, then affected the mechanical and physical properties of the vulcanized rubber. In this paper, the effects of rubber compound on metal friction and wear were studied by using four silane coupling agents commonly used in rubber mixing field. The experiment was carried out at 15°C, and the attention should be paid to drying during sample preparation to avoid the deviation of the experiment caused by hydrolysis of silane coupling agent. The results showed that silanization reaction occured between silica and silane coupling agent in the mixing process. The mixing temperature was usually maintained at 145 to 155°C for 1 min in the mixer, and the silanization reaction rate was the fastest during this time. We took this rubber compound as the research object and studied the friction and wear of the rubber compound on the mixing chamber in the mixing process. The products of the silylation reaction are alcohol and water. This paper studies the corrosion and abrasion of the mixing chamber by water at high temperatures. In the mixing process, abrasive wear was the main wear form, but the corrosion wear caused by high temperature steam still occupied a large proportion.     

CO2 capture in a multistage CFB: Part II: Riser with multiple cooling stages

A 1 m in diameter and 3.55 m tall fluidized bed riser internally with water tubes, which required six equilibrium stage of riser‐sorber for capturing about 95% of CO₂ emitted from a coal power plant, were designed to replace the multisingle risers. At the optimum operating condition, the temperature of the cooling tubes in the bottom, the middle and the top of the riser were kept constant values at 50, 40, and 30°C, respectively. The hot water (57°C) from lowest exchanger section can be used to preheat the spent sorbent for the regeneration in a downer. The rest of the heat for the regenertion is obtained from the stack gas (100–130°C). This new concept promises to reduce the energy consumption for CO₂ removal from flue gas. The only energy requirement is for pumping fluid and fluidizing particles in the bed. © 2017 American Institute of Chemical Engineers AIChE J, 63: 5280–5289, 2017     

Regeneration of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-based high-temperature coal gas desulfurization sorbent in atmosphere with sulfur dioxide

Regeneration of a high-temperature coal gas desulfurization sorbent is a key technology in its industrial applications. A Fe₂O₃-based high-temperature coal gas desulfurizer was prepared using red mud from steel factory. The influences of regeneration temperature, space velocity and regeneration gas concentration in SO₂ atmosphere on regeneration performances of the desulfurization sorbent were tested in a fixed bed reactor. The changes of phase and the composition of the Fe₂O₃-based high-temperature coal gas desulfurization sorbent before and after regeneration were examined by X-ray diffraction (XRD) and X-ray Photoelectron spectroscopy(XPS), and the changes of pore structure were characterized by the mercury intrusion method. The results show that the major products are Fe₃O₄ and elemental sulfur; the influences of regeneration temperature, space velocity and SO₂ concentration in inlet on regeneration performances and the changes of pore structure of the desulfurization sorbent before and after regeneration are visible. The desulfurization sorbent cannot be regenerated at 500°C in SO₂ atmosphere. Within the range of 600°C–800°C, the time of regeneration becomes shorter, and the regeneration conversion increases as the temperature rises. The time of regeneration also becomes shorter, and the elemental sulfur content of tail gas increases as the SO₂ concentration in inlet is increased. The increase in space velocity enhances the reactive course; the best VSP is 6000 h^?1 for regeneration conversion. At 800°C, 20 vol-% SO₂ and 6000 h^?1, the regeneration conversion can reach nearly to 90%.     

Regeneration of Fe2O3-based high-temperature coal gas desulfurization sorbent in atmosphere with sulfur dioxide

Regeneration of a high-temperature coal gas desulfurization sorbent is a key technology in its industrial applications. A Fe₂O₃-based high-temperature coal gas desulfurizer was prepared using red mud from steel factory. The influences of regeneration temperature, space velocity and regeneration gas concentration in SO₂ atmosphere on regeneration performances of the desulfurization sorbent were tested in a fixed bed reactor. The changes of phase and the composition of the Fe₂O₃-based high-temperature coal gas desulfurization sorbent before and after regeneration were examined by X-ray diffraction (XRD) and X-ray Photoelectron spectroscopy(XPS), and the changes of pore structure were characterized by the mercury intrusion method. The results show that the major products are Fe₃O₄ and elemental sulfur; the influences of regeneration temperature, space velocity and SO₂ concentration in inlet on regeneration performances and the changes of pore structure of the desulfurization sorbent before and after regeneration are visible. The desulfurization sorbent cannot be regenerated at 500°C in SO₂ atmosphere. Within the range of 600°C–800°C, the time of regeneration becomes shorter, and the regeneration conversion increases as the temperature rises. The time of regeneration also becomes shorter, and the elemental sulfur content of tail gas increases as the SO₂ concentration in inlet is increased. The increase in space velocity enhances the reactive course; the best VSP is 6000 h⁻¹ for regeneration conversion. At 800°C, 20 vol-% SO₂ and 6000 h⁻¹, the regeneration conversion can reach nearly to 90%.     

Recovery of indan derivatives from polystyrene waste

The recovery of indan derivatives from polystyrene waste for the purpose of efficient utilization of plastic wastes was studied. An attempt was made to construct the apparatus, in which thermal decomposition of polystyrene and catalytic reaction of its decomposition products over silica–alumina catalyst could be controlled continuously at the same time. The reaction temperature for thermal decomposition of polystyrene in the upper part of a reactor tube was 420°C, while that for catalytic reaction of the thermal decomposition products in the bottom of a reactor tube was 300°C. These results indicated that the composition of thermal decomposition products of polystyrene could be controlled by the use of a flow reactor. The indan derivatives recovered were two 1-methyl-3-phenylindans, one 1-methyl-1-phenylindan, and 1-phenylindan. The yields of these indan derivatives were 20% of the weight of the liquid products recovered. On the basis of the results obtained in the present work, the most suitable reaction conditions to recover indan derivatives from polystyrene waste is discussed.     

Einfluß der mechanischen spannung und der temperatur auf die photooxidation von polyethylen

The tensile stress and temperature effects on the Polyethylene photooxidation kinetics have been investigated. Subjects are light stabilized and not stabilized high density Polyethylene films. The tensile stress used were 10% and 20% of the breaking stress. Temperatures of 50°C, 30°C, 5°C were realized in a chamber for an artificial climate with an irradiation source mercury ark lamp type ??PK-2. The duration of exposure was up to 1500h. The oxidation degree has been appreciated by the carbonyl index determined by means of a IR spectrophotometer. It was established that the photooxidation process rate depends on the temperature as well as on the mechanical stress. At the tensile stress used it was found a decrease of the oxidation rate in comparison with the unloaded samples. The mechanical stress influence was stronger when testing unstabilized Polyethylene.