The Chinese Journal of Process Engineering

Low rank coal pyrolysis poly-generation and hybrid power system

Wenli SONG Songgeng LI Lin DU Weigang LIN Lijie CUI Jianzhong YAO

Chin. J. Process Eng.. 2018, 18(5): 893-899. DOI: 10.12034/j.issn.1009-606X.218219

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Low rank coal account for 80% of coal resources in China. Coal pyrolysis will result in liquid tar, pyrolysis gas and solid char products. Liquid tar could be used to obtain chemicals or fuel oil, pyrolysis gas could be used as fuel or production of methane, char could be used as clean solid fuel. Continuous research and development on Chinese low rank coal pyrolysis fundamentals, process and equipment scale-up were carried out in the Institute of Process Engineering, Chinese Academy of Sciences. Laboratory scale coal fast pyrolysis experiments between 500? 850℃ showed that, the production of pyrolysis gas was increasing with the increase of temperature, while the production of liquid tar reached the maximum value at the temperature of 650℃. The ignition temperature of char increased with the increase of pyrolysis temperature. The combustion rate of char decreasd with the increase of pyrolysis temperature, but much higher than that of anthracite. A 10 t/d capacity coal pyrolysis/combustion pilot plant was build up in Langfang campus. Experimental results of Erodes sub-bituminous coal showed that, when the char was burned as fuel, the co-production of liquid tar was 6.6% and 2.5% of dried coal, pyrolysis gas was 10.3% and 18.8% of dried coal at pyrolysis temperatures 640 and 760℃ respectively. The IPE-Power, a pyrolysis bridged hybrid power system was proposed for low rank coal poly generation for coal power plant. The technical and economic analysis showed that, the IPE power system was technical and economical feasible for new power plant for coproduction of liquid tar and power. Retrofitting of 300 MW subcritical coal power plant with this technology was also discussed, the results indicate that for the retrofitted power plant the net coal consumption was decreased from 355 g/(kW?h) to 303 g/(kW?h).

The role of microglia in Alzheimer's disease

Xiaoge LIU Lun ZHANG Xiaolin YU

Chin. J. Process Eng.. 2018, 18(5): 900-907. DOI: 10.12034/j.issn.1009-606X.218206

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Microglia, the innate immune cells of the central nervous system (CNS), serve as resident phagocytes that dynamically survey the environment and play crucial roles in CNS health and disease. Various roles are emerging for microglia in the healthy brain, from sculpting developing neuronal circuits to guiding neural plasticity. Understanding the physiological functions of microglia is important to evaluate their roles in disease. At pathological state, conditions associated with loss of cerebral homeostasis induce several dynamic microglial processes, including changes of cellular morphology, surface phenotype, secretory inflammatory mediators and proliferative responses, termed as an “activated state”. Activation and proliferation of microglia in the brain represents a prominent feature of several neurodegenerative diseases including Alzheimer's disease (AD). AD is a progressive neurodegenerative disorder that is the most common cause of dementia, which is defined as a significant, persistent, and progressive memory loss combined with cognitive impairment and personality change. The key features of AD pathology are amyloid plaques by extracellular accumulation of amyloid-β (Aβ) and intracellular neurofibrillary tangles composed of tau proteins. There is mounting evidence that microglia protect against the incidence of AD, as impaired microglial activities and altered microglial responses to Aβ are associated with increased AD risk. In CNS, microglia have protective functions by phagocytosis and clearance of toxic Aβ oligomers, which prevent the development of AD. Once activated, microglia can mediate synapse loss by engulfment of synapses via a complement-dependent mechanism, secrete inflammatory factors and exacerbate tau pathology, resulting in the neuron injury and cognitive deficits. Therefore, microglia show the double-edged sword function in AD pathogenesis. Understanding the multiple states of microglial activation and their roles in AD pathology will provide breakthrough ideas for developing AD therapeutic strategies. In this review, the role of microglia in the pathogenesis of AD and the modulation of microglia activity as a therapeutic potential will be discussed.

Research progress on green production of sugar from sugarcane by membrane technology

Jianquan LUO Xiaofeng HANG Wei LIU Zhaoshuai WANG Xiangrong CHEN Ribo HUANG Yinhua WAN

Chin. J. Process Eng.. 2018, 18(5): 908-917. DOI: 10.12034/j.issn.1009-606X.218209

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The green production of sugar by membrane technology is promising because the impurity removal, clarification, decolorization and concentration of sugarcane juice can be achieved by only physical separation. This technology has the advantages of not adding harmful substances, efficient, automatic and stable process, full utilization of by-products and product diversification. In this review, the research progress on green production of sugar from sugarcane by membrane technology in lab-scale experiments, pilot-scale tests and demonstration project was introduced respectively. The studies on membrane selection for sugarcane juice clarification, decolorization and concentration/purification were summarized, and the performances of ceramic and organic membranes were compared and analyzed. It was concluded that the ultrafiltration membrane with pore size from 30 nm to 100 nm was suitable for the clarification of sugarcane juice, and a loose nanofiltration membrane could achieve both high color retention and high sucrose transmission, while a tight nanofiltration was selected for the separation of sucrose and reducing sugar/salt in order to further increase the purity of juice. The recovery of residual sucrose from the membrane retentate, membrane fouling mechanisms and cleaning strategies were underlined. Diafiltration operation could recover most of sugar in the membrane concentrates, leading to a high sucrose recovery of up to 98% in the clarification and decolorization stages. Permeate flux of the ultrafiltration was dominated by membrane fouling, while for the nanofiltration, osmotic pressure played a more important role in the flux decline. Recently, the demonstration project for green production of sugar by membrane technology was successfully constructed in Guangdong Province, China, and the continuous and stable operation of such membrane filtration system was achieved, and the first batch of white sugar refined by membrane technology in China was obtained. Beside, several issues (e.g. pretreatment optimization, on-line monitor system upgradation, membrane fouling control, highly-valued product development and marketing as well as cost accounting) that need to be addressed for the industrialization of sugarcane juice refining by membrane technology were discussed.

High-solid and multi-phases bio-reaction engineering

Lan WANG Yang LIU Hongzhang CHEN

Chin. J. Process Eng.. 2018, 18(5): 918-923. DOI: 10.12034/j.issn.1009-606X.218232

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Low solid loading bio-reaction system lead to high energy and water consumption, as well as environment pollution in fermentation industries, ing the development of high-solid bio-reaction system. High-solid bio-reaction system has the advantages of low energy consumption, less used water and environmentally-friendly. Additionally, high-solid loading leads to higher concentration of substrate and products which are benefit to reduce cost and realize the economical efficiency in production. However, many difficulties have existed in high-solid bio-reaction system apart form so many advantages. Therefore, it is of great mean to get knowledge about the characteristics and problem of high-solid bio-reaction system which will help to make the most use of its advantages. Taking enzymatic hydrolysis and fermentation of lignocellulose for an example, increasing solid loading leads to ‘solid effects’ and ‘water constraint’. Those phenomenon result in the formation of complex multi-phase system consisted by solid, liquid, gas and the microorganism. Mass transfer performance in this high-solid and multi-phases system is deficient, thus affecting lignocellulose conversion performance. Additionally, the changes of rheology characteristics in high-solid and multi-phases bio-reaction system caused by increasing solid loading make it inappropriate to apply traditional mechanical agitation which is based on shear force (i.e. shear force can results in activity loss of the enzyme and microorganism) to high-solid and multi-phases bio-reaction system, putting new requirements on agitation methods, design and amplification of bioreactor and process of high-solid and bio-reaction system. Based on several-years studies, the conception of high-solid and multi-phases bio-reaction engineering was proposed. Key factors which affect the reaction performance were analyzed from the perspective of solid matrix characteristic. Intensification method based on periodical normal force is innovated and periodic peristalsis high-solid and multi-phases bio-reaction system was developed with the expectation of providing theory and technical support for studying high-solid and multi-phases bio-reaction engineering.

A review of crystal chemistry application in copper oxide minerals flotation

Yingqiang MA Qiuyue SHENG Youduo LI Langfeng TANG

Chin. J. Process Eng.. 2018, 18(5): 924-933. DOI: 10.12034/j.issn.1009-606X.217430

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Crystal chemistry is the theory that study the crystal structure at the atomic level. It is a branch of physics and chemistry that reveals the internal relations between the chemical composition, structure and properties of the crystal and the related principles. The law of constancy of angles, the zone law and the Pauling's rules have laid the foundation of crystal chemistry. Crystal structure and chemical composition are important factors affecting minerals flotation separation, and are also the main research contents of crystal chemistry. Crystal chemistry has been widely used in the copper oxide minerals flotation, including the study on the minerals crystal structure and surface characteristics, such as the mode of occurrence of elements, the type of chemical bond, the polarity of ionic bond, ion radius, solubility and copper ion exposure on the surface of the mineral. The relationship among the copper oxide minerals crystal structure, surface properties and copper oxide minerals floatability and the influence of collector and various adjusting agents on copper oxide minerals flotation and its mechanism analysis are also discussed. Crystal chemistry is one of the important theoretical bases for minerals separation, and plays an important role in minerals flotation. The azurite, cuprite, malachite and chrysocolla are main copper oxide minerals which have industrial utilization values. This paper summarized the research contents of crystal chemistry and its application in copper oxide minerals flotation, introduced the research status of the minerals crystal structure, ionic bond and polarization degree of copper oxide minerals, and the research progress of surface properties and floatability of copper oxide minerals. The application of crystal chemistry in the study of flotation reagent action mechanism and flotation condition control were reviewed, the research directions of crystal chemistry in minerals flotation were pointed out, including that crystal chemistry combined with tests and analysis technologies and a variety of basic theories and disciplines.

Structural design and numerical simulation of axial-swirling type micro-bubble generator

Guodong DING Jiaqing CHEN Chunsheng WANG Chao SHANG Meili LIU Xiaolei CAI Yipeng JI

Chin. J. Process Eng.. 2018, 18(5): 934-941. DOI: 10.12034/j.issn.1009-606X.217413

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A swirling-type micro-bubble generator was designed in this paper. The main structure of swirling-type microbubble generator consisted of annular gas injection mechanism and new-type bubble breaking mechanism. Among this, the annular gas injection mechanism adopted the structure of “center ring+micro-plate”. The new-type bubble breaking mechanism was composed of the static swirl element and the venturi tube. The static swirl element was coaxially set in the inlet section of venturi tube. Compared with traditional venturi tube, the new-type bubble breaking mechanism had some technical advantages and may produce much smaller microbubbles. With the help of ANSYS FLUENT software, the numerical simulation of the flow path of the new bubble breaking mechanism was carried out and compared with the conventional venturi flow path. The simulation results showed that the velocity, radial velocity gradient, turbulent kinetic energy and turbulent dissipation rate in the new bubble flow path were larger than those of the conventional venturi channel. By introducing the simulated data into the empirical formula, the calculated particle size of micro-bubbles produced at the exit of traditional venture tube was about 2 times of the new bubble breaking mechanism. The results indicated that the new bubble breaking mechanism can produce smaller microbubbles. In order to improve the bubbling efficiency of axial swirling type microbubble generator, the optimization design of new type bubble breaking mechanism was taken. The structure of the rotating element was optimized by the corresponding surface method. The optimized blade exit angle was 35°, the center cylinder diameter was 12.3 mm, and the leaf length was 10 mm. The particle size of micro-bubbles produced by the optimized bubble breaking mechanism was calculated to be 75% before optimization, which indicated that the optimized new type bubble breaking mechanism can deeply improve bubbling efficiency of axial swirling type microbubble generator.

Characters of erosion evolution on upstream surface of floating ball valves used in gas flow line

Sijia ZHENG Min LUO Qin BIE Ying LIU Jiaqiang JING

Chin. J. Process Eng.. 2018, 18(5): 942-950. DOI: 10.12034/j.issn.1009-606X.217346

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The erosion evolution phenomenon usually renders the erosion model unable to accurately calculate the dynamic change of the wall thickness. Based on an erosion experiment and numerical simulation, the erosion evolution on the upstream surface of floating ball valves with 30% opening was described using 3D imaging and moving grid techniques. An erosion evolution model that can summarize the temporal variation of each factor was proposed. The resulting erosion rate in the severely eroded area (points B, E and H in the middle portion of the upstream surface) showed a decreasing trend during erosion. The erosion rate was 0.9 times that prior to surface thinning after 250 kg sand load and was 0.825 times and 0.755 times that after 350 kg sand load and 450 kg sand load, respectively. The error of the erosion evolution model when applied to the erosion of the ball valve core upstream was less than 20% under a flow velocity of 9~80 m/s, sand particle size of 35~500 μm, and volume concentration of 1.6×10–13 to 5.7×10–6. When the erosion evolution model was applied to 19~80 m/s flow velocity, 150~230 μm sand particle size, and 1.68×10–7 to 2.6×10–5 volume concentration and with the geometrical model dissimilar to the ball valve upstream surface curvature, the prediction value can be controlled within the same order of magnitude as the experimental value.

Simulation on convective heat transfer of MPCMS in minichannel heat exchanger based on DPM model

Jinli LU Yongjun Lü Yafang HAN Fuping QIAN

Chin. J. Process Eng.. 2018, 18(5): 951-956. DOI: 10.12034/j.issn.1009-606X.217395

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With the advantage of high apparent specific heat capacity, high energy storage density, and better comprehensive heat transfer performance, the microencapsulated phase change material suspension (MPCMS) has wide application prospect in the field of energy storage and transport. In this paper, the discrete phase model (DPM) was employed to simulate the pressure drop and heat transfer characteristics of microencapsulated phase change material suspension flow in heat exchanger consisting of a series of parallel minichannel. The piecewise function that representation microencapsulated phase change material particle specific heat capacity varies with temperature was used to describe the phase change process. The inlet and outlet pressure drop and temperature difference of heat exchanger under different flow rates were discussed and compared with pure water. Meanwhile, the temperature distribution of microencapsulated phase change material suspension and heat surface were also concerned. The modified local Nusselt number in three representative channel of heat exchanger were calculated simultaneously. The results showed that the pressure drop of microencapsulated phase change material suspension in heat exchanger was consistent with that of pure water, but the value was bigger than pure water. With introducing the microencapsulated phase change material particle, the temperature increasing rate of outlet and heat surface was reduced slightly. Therefore, the outlet and heat surface of heat exchanger present low temperature compared to pure water. Because of the influence of inlet/outlet location, the temperature in heat exchanger present the distribution law as middle channel low and two sides channel high. So, there was a difference of the local Nusselt number along the flow direction in different channels. The phase change materials were melted in two sides channels of heat exchanger. However, in middle channel of heat exchanger, the phase change material was melting partly. Therefore, the location of inlet/outlet should be changed or interior structure of heat exchanger should be optimized so that to receive better flow distribution and heat transfer performance.

Investigation of structural dynamic characteristics of molten-salt pump rotor based on fluid-thermal-structure coupling

Yang ZHU Can KANG Qing LI

Chin. J. Process Eng.. 2018, 18(5): 957-964. DOI: 10.12034/j.issn.1009-606X.217372

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The molten-salt pump is used to transport high-temperature membrane caustic soda, carbonate, nitrate, phthalic anhydride and other mediums in industrial loops. The temperature of the medium in the molten-salt pump is generally above 400℃. In order to study the operation stability of the pump transporting high-temperature molten salt, the stress and the deformation of the pump rotor were simulated using ANSYS commercial code. At different medium flow rates, the effect of unsteady flow on the rotor was considered. The modal performance of the rotor was investigated as well. The results indicated that static pressure increases gradually with the increase of the flow rate. The temperature in the rotor decreased gradually from the impeller to the bearings along the shaft, and the influence of temperature deserves a full consideration during the pump design in view of high temperature gradients arising at both ends of the rotor. The maximum equivalent stress in the impeller at different flow rates occurred at the junction of the blade leading edge and the front shroud. A distinct stress concentration was found at the position of the bearings. The maximum deformation in the rotor emerged at impeller outer edge. The maximum equivalent stress and deformation degraded with the increase of the flow rate. Under the design condition, both the maximum equivalent stress and rotor deformation fluctuated slightly. The first six order natural frequencies rise slightly with the introduction of pre-stress, but the change of vibration amplitude was insignificant. Furthermore, the effect of flow rate on the modal performance was negligible. The modal deformation of the pump rotor was concentrated on the impeller, which was determined by the supporting manner and operation characteristics of the pump rotor. Natural frequencies corresponding to each mode of the pump rotor deviate considerably from the blade passing frequency and its second harmonic frequency as well. Therefore, the resonance caused by hydraulic excitations will not occur for the molten-salt pump considered.

Mass transfer performance of methanol absorption in layered packing cross-flow rotating beds

Jie DU Zhiguo YUAN Pengfei LIANG Shanshan DUAN Hangtian LI

Chin. J. Process Eng.. 2018, 18(5): 965-971. DOI: 10.12034/j.issn.1009-606X.217396

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The methanol was adsorpted by water via the layered packing cross-flow rotating bed. The effects of operating parameters such as high gravitational factor (?), empty bed gas velocity (u), liquid spray density (q) and inlet methanol concentration on the overall volumetric gas-phase transfer coefficient (KGa) of methanol were explored. The results indicated that KGa increased with the increases of ?, u and q, but the inlet methanol concentrations had a negligible effect on the KGa of methanol. Under the conditions of ?=100, u=0.9 m/s, q=17.6 m3/(m2?h), the inlet concentration of methanol was 14000 mg/m3, the absorptivity of methanol on rate was 97%, the KGa values of methanol reached 27 s?1, which was 1.1~3.9 times of the countercurrent-flow rotating packed bed with blade packing, 2~7.7 times of the cross-flow rotating packed bed with blade packing. It showed that the device can effectively reduce the mass transfer resistance of gas film control. When the inlet concentration of methanol gas was stable, high u and low q, ???value had great influence on the KGa of methanol. The mass transfer efficiency in the process of methanol absorption was effectively enhanced. The empty bed gas velocity of this equipment reached 1 m/s, which was 3~12 times of the countercurrent-flow rotating packed bed with blade packing.

Separation and recovery of potassium, aluminum and silicon after decomposition of potassium feldspar using sub-molten salt method

Anrui DONG Mengjie LUO Wei JIANG Chenglin LIU Ping LI Jianguo YU

Chin. J. Process Eng.. 2018, 18(5): 972-980. DOI: 10.12034/j.issn.1009-606X.218111

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Potassium feldspar is the typical insoluble potassium ore with enormous reserves in the whole world, which contains mainly potassium, aluminum and silicon valuable elements. It will be of great strategic significance to produce soluble potassium fertilizer, aluminum potassium sulfate, alumina and silica gel from potassium feldspar. Instead of the traditionally high temperature roasting (more than 700℃), in this work, potassium feldspar from Hebei province was decomposed using KOH sub-molten salt method at low-temperature (less than 240℃) and normal-pressure. The excess unreacted KOH was recovered through extraction of ethanol aqueous solution, and then the decomposed sample was dissolved with 2 mol/L sulfuric acid solution to transfer K, Al, Si in the mineral powder into the liquid phase, called the mother solution for the separation and recovery of K, Al, Si. Here, sol?gel method and stepwise alcohol precipitation method were used to separate and recover Si, Al and K from the mother solution. The preparation conditions of silica gels, aluminum potassium sulfate and K2SO4 from the mother liquor and the conditions to produce Al2O3 from KAl(SO4)2?12H2O pyrolysis were investigated. An efficient and clean technological route for the comprehensive utilization of potassium feldspar resources was developed. The results showed that the main compositions of potassium feldspar were K2O 13.13wt%, Al2O3 16.66wt% and SiO2 58.28wt%. Silica gel was easy to be formed in the mother solution at 95℃ and concentration of H+ 3.800 mol/L, the desilication rate was over 98%, and SiO2 content of silica gel was more than 99.0%. The BET surface area was more than 700 m2/g, pore volume was about 1.0 cm3/g and pore size was 5?6 nm. The separation of potassium and aluminum from the mother solution was enhanced by the stepwise alcohol precipitation. Firstly, aluminum potassium sulfate with high purity was precipitated at 25℃, the volume ratio of ethanol to feed 1.0, stirring speed 200 r/min, time 5 min, the precipitation rate of aluminum reached 98%, and then the temperature in the solution was decreased to 5℃ with the volume ratio of ethanol to feed 2.0, and potassium sulfate was precipitated, the recovery rate of potassium reached 89%. Alumina was prepared by pyrolysis of aluminum potassium sulfate. When the pyrolysis time was 2 h, the decomposition rate of aluminum potassium sulfate reached 99.8% at 1000℃, and the purity of the alumina product could reach 94%.

Separation and extraction of nickel and molybdenum by alkaline reduction smelting-water leaching from high carbon Ni-Mo ore

Long CHEN Chaobo TANG Yongming CHEN Yun LI Jianguang YANG Jing HE Shenghai YANG

Chin. J. Process Eng.. 2018, 18(5): 981-988. DOI: 10.12034/j.issn.1009-606X.217408

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The reserves of nickel?molybdenum ore resources are very rich in China. However, the existing processes suffer from lots of shortcomings, such as low recovery rate of valuable metals, environment pollution of sulfur dioxide and large reagent consumption. A new clean metallurgical process that Ni?Mo ore alkaline-reduction smelting and water leaching was proposed in this paper. Under the conditions of alkaline medium and strong reducing atmosphere, nickel in nickel?molybdenum ore was reduced to high grade nickel?iron alloy and molybdenum was converted to soluble molybdate. On the basis of theoretical analysis, a new clean metallurgical process with two steps of alkaline-reduction smelting and water leaching was proposed to recover Mo and Ni from nickel?molybdenum ores adopted from Zunyi city of Guizhou province. The effects of various parameters, including the dosage of sodium carbonate, smelting temperature, the dosage of reducing agent and smelting time, on the direct recovery rate of nickel and leaching rate of molybdenum were investigated by single-factor experiments. Under the optimum conditions, the enlargement experiment was carried out. The results showed that under the conditions of alkaline medium and strong reducing atmosphere, nickel in nickel?molybdenum ore was reduced to high grade nickel?iron alloy while molybdenum was converted to soluble molybdate. The optimum conditions were obtained as follows: the Na2CO3 consumption was double of the theoretical amount, the smelting temperature of 1000℃, the reductant consumption of 5wt% equal to Ni?Mo ore dosage and the reaction time of 90 min. The recovery rate of nickel reached up to 94.92%, the volatilization rate of molybdenum was 9.36%, the leaching rate of molybdenum was 99.94% and the sulfur capture capacity was close to 100%. Finally, nickel?iron alloy and molybdenum leaching solution were obtained and nickel and molybdenum were separated effectively.

Competition mechanisms in separation of vanadium and chromium with extraction method

Ying SUN Pengge NING Hongbin CAO Wenzhao LIU

Chin. J. Process Eng.. 2018, 18(5): 989-995. DOI: 10.12034/j.issn.1009-606X.217427

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In our country, a lot of chromium-bearing vanadium slag was produced in metallurgy and phosphorous chemical industries. The utilization of these resources to recover vanadium and chromium is not only a way to prepare high-value vanadium production, but also an efficient method to resolve the environmental pollution issue. For the best separation of vanadium(V) and chromium(IV), primary amine N1923 was used to extract V(V) selectively from V(V) and Cr(IV) aqueous solution with various concentrations ratios under different initial pH values. Besides, the interact between V(V) and Cr(IV) was investigated though comparing their extraction rate in complex solution and single solution respectively. The results indicated that their extraction rates both increased with the decrease of initial pH value in solution and primary amine N1923 created great selectivity on the separation of V(V) and Cr(IV). The higher Cr(IV) concentration was, the lower initial pH values was needed for the best separation efficiency. The extraction rate of V(V) in complex solution was higher than that in its single solution, but that of Cr(IV) was just on the contrary. Affected by V(V), the extraction rate of Cr(IV) in complex solution went up and then went down with time going. That was because Cr(IV) reach equilibrium pH value ahead of V(V) and part of Cr(IV) in organic phase could be reversed by V(V), where the competition mechanisms in separation of V(V) and Cr(IV) with extraction method was discussed that the combination abilities of the two metal with hydrogen ion and primary amine molecule were different. As a theory favour, the revelation of competition mechanisms in extraction makes great contribution to the separation of V(V) and Cr(IV), while this paper would guide the resourceful recovery of vanadium and chromium from waste slag in metallurgical industry and make great benefits in economy, environment and society.

Isobutane/butene alkylation catalyzed by rare earth La modified X-zeolites

Jiakuo XU Zhiqiang YANG Zihang LI Hongguo TANG Baozeng REN Ruixia LIU Tao LI

Chin. J. Process Eng.. 2018, 18(5): 996-1002. DOI: 10.12034/j.issn.1009-606X.218123

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Five kinds of rare earth La-modified X-zeolite catalysts were prepared by liquid-phase ion exchange procedures with different time of ion exchange and calcination. Their catalytic performance were tested in isobutane/butene with a continuously operation fixed bed reactor. The crystallographic structure of catalysts were characterized by XRD, and the acidity were examined by NH3-TPD and infrared spectroscopy for pyridine adsorbed (Py-IR). The results showed that the preparation process had significant effects on the structure and properties of the catalyst. The structure of zeolites did not change fundamentally after the introduction of lanthanum, but their crystallinity decreased significantly. The distribution of acid sites depend strongly on the lanthanum ion exchange procedures, especially the rehydration process of zeolite after the first calcined for ion exchange, which could significantly improve the strong B acid capacity of zeolite. The introduction of La3+ could increase the acidic sites of the zeolite, enhance the strong B acid, and reduce L acid of the catalyst. Among the five catalysts, catalytic performance of 2+3 when its ion exchange twice before calcination and thrice after calcinations occurred and it was calcinated again exhibited best, the initial conversion rate of butene was 89.94% and the yield of C8 products was 66.71%. This is because the enhancement of acidity due to the modification of La facilitate the hydrogen transfer, which is the determine step of alkylation, resulting in inhibiting the side reactions. The reaction temperature and feeding speed have strong effects on alkylation catalyzed over the La-modified X-zeolite. C5?C7 products increased from 9.64% to 36.74% when the reaction temperature was increased from 80℃ to 100℃. When the feed rate of butene was reduced from 0.1 h?1 to 0.05 h?1, the oligomeric generated C9+ products increased from 7.2% to 31%.

Dynamic control of pressure-swing distillation for separating azeotropic system of methanol/benzene

Liping Lü Hang LI Bing LI Jianhua XU

Chin. J. Process Eng.. 2018, 18(5): 1003-1012. DOI: 10.12034/j.issn.1009-606X.217378

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The design and control of the pressure swing distillation (PSD) for the separation of methanol and benzene binary minimum azeotropic system were explored based on the pressure sensitivity of the azeotropic composition. Aspen Plus (8.4 V) software was used to simulate and optimize the steady state process by the minimization of total annual cost (TAC). Based on the optimal steady state results, three kinds of the control structure including basic control structure, ratio control structure and double ratio and temperature?component combined control structure for the PSD process were put forward to maintain the purity of the product. According to the temperature slope criterion by Luyben, the stage 13th in the low pressure distillation is selected as the temperature sensitive stage. However, it was somewhat difficulty for selecting the temperature sensitive stage for the high pressure distillation. Because the maximum value of the temperature slope was the stage 21th which was the bottom of this column. If the stage 21th was chosen to the temperature sensitive stage, it was very difficult to maintain the temperature as a constant value. So the stage 20th was selected as the suitable temperature sensitive stage by the liquid composition distribution. The ±20% feed flowrate and composition disturbances were used to test the dynamic performances of these control structures. The results showed that the selection of the temperature sensitive stage was reasonable and the basic control structure can basically achieve robust control, but the problem of product purity deviation due to component disturbances cannot be solved. Ratio control structure can achieve relatively robust control, but the purity of methanol in the bottom stream of the LPC (B1) still cannot return back to the desired value. The double ratio and temperature?component combined control structure can effectively maintain the product purity of 99.90% when the control loop arrives at a new steady state after encountering ±20% changes in feed flowrate and feed methanol.

Melting temperature and viscosity characteristic of dephosphorization slag contained CaO-SiO₂-FeO-B₂O₃-MnO

Shuangping YANG Qishu WEI Chen WANG Bo YANG Jinkun PANG

Chin. J. Process Eng.. 2018, 18(5): 1013-1019. DOI: 10.12034/j.issn.1009-606X.217385

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In order to reduce the melting temperature and viscosity of dephosphorized slag, many metallurgical workers added CaF2 as the melting agent, but fluorine ion was very harmful to the environment, and it eroded the lining of the furnace, and dephosphorized slag was difficult to be reused. Therefore, for the sake of solving the above problems, it was necessary to explore a new fluorine-free or low-fluorine dephosphorizer. Boron element were beneficial to the plant, the choice of B2O3 dephosphorization slag flux, the better preparation of fertilizer by the dephosphorization slag. Boron resources were rich in our country, therefore, in the hot metal dephosphorization, B2O3 can displace CaF2. In order to systematically study the melting temperature and the comprehensive effect of viscosity characteristics of iron water pre-melting dephosphorized slag, the melting temperature and viscosity of CaO?SiO2?FeO?B2O3?MnO pre-melting dephosphorization slag of type of fluorine-free were calculated and the influence law of alkalinity and composition ratio on melting temperature and viscosity of dephosphorization slag seeking reasonable dephosphorization slag into distribution ratio and control interval, suitable bath temperature were investigated by using FactSage simulation software and the modified Einstein?Roscoe formula. The alkalinity and composition ratio was optimized by orthogonal analysis, variance analysis and main effect analysis. The results showed that the viscosity of the slag decreased with the increase of alkalinity, FeO content and flux content. At 1400℃, the optimum ratio were alkalinity of 4.0, the content of B2O3 9%, MnO of 10%, FeO of 45%. By caclution, the melting temperature was 1195.51℃ and the viscosity was 0.207 Pa×s. By the experimental verification, the measured melting temperature was 1192.21℃, the viscosity was 0.199 Pa×s. After comparison, the calculated date was similar to the measured data. It was known that the orthogonal method had its rationality and accuracy in the actual production process. Based on the analysis results, the optimal combination of slag components was selected to provide theoretical basis and data support for the dephosphorization production of steelmaking.

Analysis of gas-liquid filtering characteristics under different working pressures

Runpeng WANG Xiaolin WU Zhen LIU Zhongli JI

Chin. J. Process Eng.. 2018, 18(5): 1020-1028. DOI: 10.12034/j.issn.1009-606X.217432

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The oil droplet and powder in gas will caused serious damage to the equipment in the processes of dry gas seals, long-distance transmission of natural gas and large rotating machinery crankcase ventilation, the filter test under atmospheric pressure cannot accurately show the filter performance. According to the ISO-12500 standard, a performance testing system of compressed air filter was established, the experimental operating pressure can be adjusted from 0.1 MPa to 0.7 MPa. The effects of operating pressures on lipophilic and oleophobic filter’s liquid distribution, saturation and pressure drop were analyzed. The results showed that the pressure had a significant effect on the initial pressure drop, liquid migration and saturation of the oleophobic filter. When the operating pressure rose 0.2 MPa, the initial pressure drop of the filter rose by 0.32 kPa, the wetting pressure drop of the filter element (the difference between the equilibrium pressure drop and the initial pressure drop) fluctuated between 4.5 kPa and 5.1 kPa under each operating pressure. Compared with 0.1 MPa, the saturation of the last layer increased by 71% under 0.7 MPa. The number of small wetting area increased and there was a short jump stage before the pressure drop reached equilibrium under 0.7 MPa, this may aggravate the re-entrainment of the filter element, resulting in an increase in the number of droplets in the downstream pipe of the filter, reducing the efficiency of the filter. Influence of operating pressure on the initial pressure drop of lipophilic filter was remarkable, when the operating pressure rose 0.2 MPa, the initial pressure drop of the filter rose by 0.39 kPa. Operating pressure had little effect on fluid migration and saturation, each layer had the same filter saturation distribution, liquid distribution under different operating pressure.

Flame spread characteristics of latex foam at different ignition positions

Mingzhen ZHANG Dongmei HUANG Qi YUAN Shuwen WANG

Chin. J. Process Eng.. 2018, 18(5): 1029-1036. DOI: 10.12034/j.issn.1009-606X.217415

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Natural latex based furniture is widely used in our daily lives. However, it is very easy to be ignited. Once ignited, fire could spread remarkably fast companied with a large amount of heat, smoke and fumes, which are extremely harmful to human beings. It makes sense to study the flame spread of latex foam. In this paper, the influence of ignition positions on the flame spread characteristics of latex foam were analyzed experimentally using a small-scale experimental setup and the ignition point was put on the center and edge of the specimen. The surface temperature profiles, flame height and flame spread rate were measured. The results showed that the latex foam combustion process can be divided into 5 stages: heat absorption, pyrolysis, ignition, heat transfer and flame spread. The flame spread direction was from the center to the edge showing a circle shape for the center ignition conditions. For the edge ignition condition, flame spread from one edge point to the diagonal point with the shape of sector. The average flame rate and the time of flame spread to whole surface of material for edge ignition condition were much higher than that of the center ignition condition. The average flame rates for edge and center ignition conditions were 0.42 and 0.24 cm/s, respectively. However, maximum flame height under edge ignition condition showed a lower value than those under center ignition condition, which is 68.6 cm comparing to 82.7 cm. The scale of burnt zone under two conditions expanded gradually with an increase of flame temperature. Therefore, more energy was passed to unburnt zone, which led to the speed up of material pyrolysis and the increase of flame spread rate. The heat transfer mechanism of the sample was investigated. In practice, this study can have a practically guiding meaning for fire protection and rescue.

Effects of composite alloying on machinability of austenitic medium manganese steel and fuzzy comprehensive evaluation of machinability

Rui JIN Zhiying REN Hongbai BAI Yangyang YANG Yujie ZHANG

Chin. J. Process Eng.. 2018, 18(5): 1037-1044. DOI: 10.12034/j.issn.1009-606X.218108

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Austenitic manganese steel has been widely used in various fields as wear-resisting material, but it belongs to the typical difficult-to-machine material with extremely poor cutting performance, which limites the scope of its application to a large extent. The composition of traditional austenite medium manganese steel added with Mo, Cr, Nb and RE to combine alloying treatment was studied. The thermal conductivity and machinability of prepared manganese alloy in the austenite was tested. The effect of composite alloying on machinability of austenitic manganese steel was explored. A second-level fuzzy comprehensive evaluation model to quantitatively analyze machinability with the austenitic manganese steel hardness, tensile strength, elongation, impact toughness and thermal conductivity as influencing factors was established. The results showed that the composite alloying treatment can improve machinability of austenitic manganese steel to a certain extent when contents of alloying elements Mo, Cr, Nb were 1.87wt%, 2.43wt% and 0.059wt%, the tool flank wear width (VB value) of the sample reduced by 14.3% compared to the non-alloyed ZGMn13. The correlation between the evaluation index obtained by the two-level fuzzy comprehensive evaluation model and the VB value obtained by the tool wear experiment was significant. The linear correlation coefficient was –0.87334, which indicated a high degree of linear negative correlation, and the result was generally consistent with the VB value. In this way, it is proved that the evaluation model adopted was in line with actual production, and the evaluation result was accurate and effective.

Prediction for CH₄ adsorption isotherm based on DA model

Gaowei YUE Chunlin ZENG Xinjun ZHENG Liupeng HUO

Chin. J. Process Eng.. 2018, 18(5): 1045-1051. DOI: 10.12034/j.issn.1009-606X.217375

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Methane adsorption characteristics in coal play an important role in the gas content estimation and gas productivity prediction in coal-bed, one group of methane adsorption data in coal under a certain temperature is only applicable to the adsorption isotherm in this temperature which can't predict methane adsorption capacity under other temperature and pressure conditions. In the practical work, both the coalbed methane resources exploration and the prevention and control of gas disaster in coal mine need to know methane adsorption characteristics in coal seam at certain temperatures and depth. Because there are differences of methane adsorption isotherms at different temperatures, so many adsorption isotherms need to test at each temperature, which will cause high cost and long time. So according to the metamorphic grade of coal, gas-fat coal, cooking coal, meager coal and anthracite coal were chosen as test coal samples, methane isothermal adsorption tests at 243.15, 263.15, 283.15, 303.15 and 323.15 K were carried out with high and low temperature environment test system for gas adsorption and desorption. Based on Dubinbin?Astakhov (DA) equation and polanyi adsorption potential theory, the relationships of saturated adsorption quantity and characteristic adsorption energy with temperature can be gotten by fitting the measured data, and then the gas adsorption isotherm of coal at other temperature were predicted. The results showed that the gas adsorption capacity of coal with different metamorphic degree increased with the temperature decreasing, and there had good linear relationships between the gas saturated adsorption capacity and the characteristic adsorption energy of different metamorphic coals, which correlation coefficients reached above 0.98. At the same temperature, as the coal metamorphism degree increases, the methane adsorption amount increases under the same adsorption equilibrium pressure. Under different temperatures the predicted adsorption isotherms of coal based on the DA model with different metamorphic degrees agreed well with the experimental results. The relative error was no more than 5%. With little measured data of isothermal adsorption tests, DA model can accurately predict the adsorption abilities of coal at different temperatures and pressures, which will greatly reduce the workload and provide an important basis to study the coal reservoir adsorption properties.

Preparation of high specific surface area Cu(OH)₂ nanowires/nanorods by coordinated precipitation

Shuang XU Jingkui QU Guangye WEI Tao QI

Chin. J. Process Eng.. 2018, 18(5): 1052-1060. DOI: 10.12034/j.issn.1009-606X.217426

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Nano-copper hydroxide powder with different morphologies was synthesized by coordinated precipitation using CuSO4?5H2O, ammonia and NaOH as materials. The effects of amounts of NaOH and ammonia, and CuSO4 concentration on the morphology, particle size and specific surface area were investigated. The results showed that for different amounts of NaOH, when CuSO4 initial concentration was 0.1 mol/L, molar ratio of NH3:CuSO4=7 and molar ratio of NaOH:CuSO4=2~4, the prepared Cu (OH)2 was assembled into flower clusters by nanowires, and the numbers of flower-like structure of single head decreased and the double head flowers increased with amounts of NaOH increasing. For different amounts of ammonia, when CuSO4 initial concentration was 0.1 mol/L, molar ratio of NH3:NaOH=2 and molar ratio of NH3:CuSO4=7, the flower-like copper hydroxide of which the diameter was 0.3?1 μm and the length was 1?3 μm composed of nanowires the aspect ratio of which was 20?60 was obtained, and the Cu(OH)2 particles the surface on which had adsorbed water had uniform particle size distribution and the specific surface area of the powder was as large as 83.3 m2/g. For CuSO4 concentration, when molar ratio of NH3:CuSO4=3, and molar ratio of NaOH:CuSO4=2, the Cu(OH)2 nanowires tended to assemble into flower-like cluster structures with CuSO4 initial concentration decreasing.

Graphene quantum dots modified flexible silicon nanowires array for NO₂ detection

Qian PAN Wenyu SHANG Rongxin ZHU Hongying LIU

Chin. J. Process Eng.. 2018, 18(5): 1061-1067. DOI: 10.12034/j.issn.1009-606X.218101

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The detection of toxic and harmful gas NO2 is an important measure to reduce environmental pollution. In the field of gas detection, silicon nanowires array is an excellent material because of its high specific surface area, high surface activity, surface functionalized modification and admirable biocompatibility. Therefore, silicon nanowires array has attracted a wide range of attention in the field of gas detection. Graphene quantum dots exhibit excellent optical, electrical, quantum confinement effects and other unique properties. It is widely used in photovoltaic devices, electronic devices, biosensors and other fields. The nano size of graphene quantum dots makes it possess great biocompatibility and chemical stability, furthermore, its aqueous solution can functionalized modify different types and sizes substances. The chemical etching method was combined with the metal assisted etching method, based on P monocrystalline silicon, to prepare high-quality flexible silicon nanowires array with uniform morphology. A flexible graphene quantum dots/silicon nanowires core?shell structure array with stable surface and strong carrier transport ability was obtained through the further modification with graphene quantum dots on its surface, the array was used to detecting NO2. The results showed that, by the modification of graphene quantum dots, the surface oxidation of silicon nanowires array can be avoided and the surface stability of silicon nanowires array is improved. What’s more, owing to the strong ability of graphene quantum dots to attract and store the electrons, the carrier migration rate of the device is further improved. When the device is used for gas detection, resistive gas sensor based on this array had extremely high sensitivity and repeatability of NO2, and the detection limit of NO2 reached to 20 mg/m3. The gas sensing properties of the flexible graphene quantum dots/silicon nanowires array could be maintained with different bending angles. The response current peak when the bending angle was 90o can still hold as 70% of the value before bending.

Preparation and photocatalytic properties of ZnO/C/TiO₂ nanoparticles

Guixiang XIE Jijian WEI Zhibiao HU Ruijuan ZHENG

Chin. J. Process Eng.. 2018, 18(5): 1068-1074. DOI: 10.12034/j.issn.1009-606X.218127

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The use of materials such as grapheme and metal organic framworks to enhance the electronic transmission capacity of semiconductor photocatalytic materials has become increasingly popular. In the experiment, ZnO/C was obtained from the metal organic framework MOF-5, which was used as precursor, by high-temperature treatment under nitrogen atmosphere. Then the nanocomposite photocatalyst ZnO/C/TiO2 composite was prepared by hydrothermal method using TiO2 as the basic particles. The crystal structure, morphology and composition properties of the samples were characterized by the approaches such as XRD, SEM, energy spectrum, surface area analyzer and porosity analyzer. By using orthogonal experiment method, the effects of MOF-5 treatment temperature was evaluated, and the influence of doping amount of ZnO/C and adding amount of butyl titanate on the photocatalytic properties of photocatalyst to methyl orange degradation were investigated by the orthogonal test as well. The results showed that the particle size of ZnO/C/TiO2 composite was 11.89 nm, the size of the sample was evenly distributed, and the particle size was nano-level, no agglomeration, the specific surface areas of TiO2 and ZnO/C/TiO2 were 87.5 and 109.0 m2/g, the average pore radius of them were 2.72 and 2.61 nm. The best conditions for the preparation of ZnO/C/TiO2 were as follows: MOF-5 was treated under 600℃, ZnO/C doping amount of 0.07 g, and addtion 1.5 mL of butyl titanate. After 90 min irradiation under UV light, the degradation rate of methyl orange was 62.1% with TiO2 as photocatalyst, the degradation rate was improved greatly to 99.5% with ZnO/C/TiO2 as photocatalyst. The catalytic activity increased substantially.

Preparation and biological evaluation of electrospun collagen membrane

Yujie MOU Xiongxin LEI Fangyu XING Jianping GAO Gongze PENG Guifeng ZHANG Minglin WANG

Chin. J. Process Eng.. 2018, 18(5): 1075-1081. DOI: 10.12034/j.issn.1009-606X.217440

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Collagen bio-membrane possesses excellent biochemical characteristics, it has been widely used in the field of biomedicine. However, the existing membrane preparation techniques have series problems such as uneven membrane formation, low mechanical strength, and short degradation time after membrane formation. The modification method of compounding collagen with other polymer materials has the problems of immunological rejection and uncontrollable of degradation time. In this study, the collagen (CoL) membrane using spray electrospinning technique with hexafluoroisopropanol as the solvent was prepared. The synchronous crosslinking process was carried out during electrospinning with glutaraldehyde (GA) as crosslinking reagent. In order to optimize the suitable glutaraldehyde cross-linking concentration, the morphology, structure, mechanical properties, thermal denaturation temperature and the water contact angle (wettability) of the membrane were characterized by SEM, FT-IR, XRD, compressive test, DSC?TGA and contact-angle test respectively. Moreover, vitro experiments including co-culture assay, CCK-8 assay were executed to evaluate the biocompatibility of materials to cells. Series of tests and characterizations indicated that the optimal concentration of GA was 9wt%. The GA?CoL co-spun membrane obtained had uniform structure, in which the fiber diameter in the membrane was 450~750 nm. The FT-IR and XRD results reflected that the triple helix of collagen kept the native state. The mechanical properties test results indicated that the maximal strength of GA?CoL membrane was 1.21?0.03 MPa and the maximal elongation at break was 6.48%. The water contact angle of the spinning membrane was 45.4°, indicating the good hydrophilicity of the membrane. The biocompatibility test in vitro showed that MC3T3-E1 could adhere well on membrane and there was no significant difference in proliferation rate compared with the control group (P>0.05). Conclusively, the collagen-based biofilm prepared by spray electrospinning technique at a GA concentration of 9wt% had good physicochemical properties compared to other group of concentration, and this bio-membrane has good biocompatibility to MC3T3-E1 in vitro.

Synthesis of zirconium substituted mesoporous molecular sieve using mixed surfactants as templates

Yue LIU Lei CAO Da LI Kun CAO Fusheng SUI Wei ZHAO Wei Lü Tao QI

Chin. J. Process Eng.. 2018, 18(5): 1082-1087. DOI: 10.12034/j.issn.1009-606X.217433

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The rapid economic development has also brought many environmental problems while providing people with a high quality of life. In particular, a large number of industrial solid wastes have become increasingly prominent. This facilitates the synthesis of highly active and doped mesoporous molecular sieves inexpensively because some industrial solid wastes contain both silicon species and transition metal elements. In this paper we used mixed surfactants system as template and the industrial silicon slag with zirconium as raw material for the synthesis process of zirconium substituted mesoporous molecular sieve. In the synthesis process, cationic surfactants (cetyltrimethylammonium bromide CTAB was used in this paper) were mainly used, and other surfactants (such as nonionic surfactant polyphenol vinyl ether-10, OP-10; neutral primary amine dodecylamine, DDA, and anionic surfactant sodium dodecyl benzene sulfonate, SDBS and sodium dodecyl sulfate SDS) supplemented, the effect of different mixed surfactants systems on the synthesis of zirconium substituted mesoporous molecular sieves in hydrothermal system were studied. In order to improve the synthesis repeatability, the effects of various factors on the proprietary of zirconium substituted mesoporous molecular sieves, such as the molar ratios of water to silicon and mixed surfactants to SiO2, crystallization temperature and crystallization time were also studied. The sample obtained under optimum conditions were characterized with different methods. The results showed that the optimized synthesis system was the mixed anionic and cationic surfactants (CTAB and SDBS), the suitable mole ratios of surfactant/SiO2 and H2O/SiO2 were 0.15 and 58, respectively. The optimized crystallization temperature and time were 100℃ and 48 h. The zirconium substituted mesoporous molecular sieves had a clear diffraction peak in the low angle region, indicating that the sample had a certain long-range order. The interplanar spacing d was 9.71 nm, the average pore diameter was 5.55 nm and the wall thickness was 4.16 nm. The zirconium substituted sample had a three-dimensional worm-like pore structure. For the mixed dyes solution of methylene blue, rhodamine B and methyl orange, the sample showed a good selective adsorption ability to methylene blue, the adsorption rate was 90.31%.

Optimizing preparation of chemical modified desulfurization ash/styrene butadiene rubber composite materials based on BP neural network

Hao ZHANG Qing GAO Xiuyu LIU Ying LIU

Chin. J. Process Eng.. 2018, 18(5): 1088-1092. DOI: 10.12034/j.issn.1009-606X.217431

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Chemical modified desulfurization ash/styrene butadiene rubber composite materials were prepared using chemical modified desulfurization ash replacing partial carbon black，BP neural network optimization model of preparation process parameters (amounts of accelerator, sulfur, amount of stearic acid, and zinc oxide and curing time) and mechanical properties were established by uniform design in a combination with BP neural network to acquire parameter of optimal chemical modified desulfurization ash/styrene butadiene rubber composite materials. Tensile properties of chemical modified desulfurization ash/styrene butadiene rubber composite materials were tested by referring to rubber, vulcanized or thermoplastic-determination of tensile stress-strain properties, tear strength of chemical modified desulfurization ash/styrene butadiene rubber composite materials were tested by referring to rubber, vulcanized or thermoplastic-determination of tear strength, hardness of chemical modified desulfurization ash/styrene butadiene rubber composite materials was tested by referring to rubber, vulcanized or thermoplastic-determination of indentation hardness, Duromerer method (Shore hardness) (trouser, angle and crecent test pieces). Microstructure of optimal chemical modified desulfurization ash/styrene butadiene rubber composite materials were observed by SEM, mineral composition of optimal chemical modified desulfurization ash/styrene butadiene rubber composite materials were analyzed by XRD. The results showed that the parameters of optimal chemical modified desulfurization ash/styrene butadiene rubber composite materials were amount of accelerator 1.2 g, amount of sulfur 1.3 g, amount of stearic acid 1.1 g, amount of zinc oxide 2.4 g and curing time 27 min. Mechanical properties of optimal chemical modified desulfurization ash/styrene butadiene rubber composite materials were tensile strength 20.31 MPa, tear strength 45.68 kN/m and Shore A hardness 66. The optimal measured values and the model optimal predictive values were in good agreement, the relative error was 3.03%?3.22%. The above research provides technical support and theoretical basis for the development of cheap inorganic filler which can replace partial carbon black.

Simulation on hydrogen absorption process of metal hydride based hydrogen storage reactor coupled with phase-change thermal storage

Jing YAO Pengfei ZHU Jiawei REN Zhen WU

Chin. J. Process Eng.. 2018, 18(5): 1093-1101. DOI: 10.12034/j.issn.1009-606X.217438

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A transient two-dimensional mathematical model of solid-state hydrogen storage reactor coupled with phase-change material (PCM) as heat exchanger was developed on the basis of metal hydride hydrogen absorption reactions. The influences of the operating and thermophysical parameters, including the initial hydrogen pressure, the PCM melting temperature, PCM solid (liquid) thermal conductivity and melting enthalpy, on the hydrogen absorption performances of the reactor were further investigated. The simulation results showed that different thermophysical parameters of PCM affect the reactor performance in varying degrees. The influences of the PCM solid thermal conductivity and melting enthalpy on the hydrogen absorption behavior of the reactor were small, while the PCM melting temperature and liquid thermal conductivity had a great impact on the hydrogen absorption process. It was found that the hydrogen storage reactor presented an improved hydrogen absorption behavior when the PCM melting temperature was reduced or the PCM liquid thermal conductivity becomes large. This is because that both the reduction of the PCM melting temperature and the increase of the PCM liquid thermal conductivity help to enhance the heat transfer between metal hydride and PCM, thus facilitating the hydrogen absorption reaction in the reactor. By contrast, the larger PCM solid thermal conductivity only accelerates the temperature rise process of the PCM and has few influences on the hydrogen absorption reaction of metal hydride. Besides the thermophysical parameters of PCM, the operating parameter such as hydrogen pressure also presents a great impact on the reactor performance. Improving the hydrogen pressure under the conditions of the optimized PCM thermophysical properties contributes to the improvement of the reaction rate, which subsequently enhances the heat transfer between metal hydride and PCM. Through the parametric analyses, the key affecting parameters and their optimization strategy are obtained for the metal hydride reactor coupled with the PCM as heat exchanger, which is significant and valuable for the development of advanced hydrogen storage reactors.

Combustion characteristics of CH₄ at O₂/H₂O atmosphere and gas hydrate co-production process

Duoduo HU Yindi ZHANG Chang LIU

Chin. J. Process Eng.. 2018, 18(5): 1102-1111. DOI: 10.12034/j.issn.1009-606X.218114

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Based on the improvement of O2/CO2 combustion technology, O2/H2O (oxy?steam) combustion technology has been widely concerned by scholars at home and abroad. Because of its advantages of small system coupling, easy start-up and low concentration of pollutants, it may become the next generation potential oxygen-rich combustion technology. At present, most studies have studied the effect of N2, CO2, and H2O(g) as diluents on the combustion characteristics of methane in single or pairwise comparisons. However, the combustion characteristics of methane in O2/N2, O2/CO2 and O2/H2O atmospheres are rarely analyzed comprehensively. And there are few researches on related applications of O2/H2O combustion technology at home and abroad. In this paper, the combustion characteristics of CH4 and the generation of main pollutants under the three atmospheres of O2/N2, O2/CO2 and O2/H2O were studied. Based on this, a new technology case based on O2/H2O atmosphere combustion and replacement of natural gas hydrates was proposed. The effects of three combustion atmospheres on combustion temperature, combustion rate, generation of pollutants (NOx, Soot), and combustion efficiency of methane were compared and analyzed. Simultaneously, the size of the outlet O2 concentration was taken as a synergistic consideration for pollutant emissions. The results showed that compared with O2/N2 and O2/CO2 atmospheres, the combustion temperature was the lowest, the combustion rate was the highest, the generation of pollutants (NOx, Soot) was the least, the combustion efficiency was the highest, and the export O2 concentration was the lowest under the atmosphere of O2/H2O. Therefore, O2/H2O combustion technology stood out. On this basis, the concentration ratio of O2/H2O matching with the characteristic curve of traditional combustion temperature distribution was determined: 32%O2/68%H2O. Based on the results of the simulation study, a new set of O2/H2O combustion technology and the development of natural gas hydrates co-production process was proposed, which can provide theoretical and technical support for future industrial applications of advanced combustion technology.

Polymer-based spherical active carbon and its VOCs adsorption performance for fluidized bed application

Yuan CHANG Jiale ZHENG Lin DU Songgeng LI Wenli SONG

Chin. J. Process Eng.. 2018, 18(5): 1112-1118. DOI: 10.12034/j.issn.1009-606X.217418

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Volatile organic compounds (VOCs) are the most common air pollutants emitted from chemical, petrochemical and allied industries. Adsorption is one of the most effective methods of controlling VOCs emission. Fluidized bed adsorption/desorption process is proposed for handling large flows of contaminated gaseous streams. The expected advantages are continuous processing, the ability to treat large flows under moderate pressure drop, the possibility to handle dusty gases, good mass and heat transfer between fluid and particles. For fluidized bed adsorption process the adsorbents are subject to strong attrition and conventional active carbons particles are not suitabe. A perfectly spherical activated carbon with strong attrition resistance and good VOC adsorption ability is developed for fluidized bed application. Polystyrene beads were used as precursor to make polymer-based active carbon (PCB) adsorbent through different activation methods, including steam activation, ZnCl2 activation and synergistic activation with both steam and ZnCl2. The active carbon adsorbent with synergistic activation presented high specific surface area (1702.49 m2/g) than that from other activation process. The measurement of static adsorption capacity of PCB with dimethylbenzene, acetone, ethyl acetate and hexane for different PBS adsorbents are conducted and presented. In the research of dynamic adsorption, a fixed bed reactor was used to explore the ethyl acetate adsorption behavior on PCB adsorbents and the mass transfer zone length was obtained. Yoon?Nelson model was used to describe the adsorption behavior of ethyl acetate on adsorbents and model parameters are compared for different active carbon adsorbents. The particle size distribution of PCB adsorbents is between 0.208?0.832 mm, with the averaged particle diameter of 0.495 mm. The PCB adsorbents had good abrasion resistance with attrition index less than 0.1% and that is suitable for fluidized bed application.

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