The Chinese Journal of Process Engineering

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The Chinese Journal of Process Engineering. 2021, 21(5): 0.

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Denitration mechanism of sintering flue gas on activated carbon

Yunlong HAN Jie JI Xiaobai YANG Fuping QIAN Yongmei HU

The Chinese Journal of Process Engineering. 2021, 21(5): 495-505. DOI: 10.12034/j.issn.1009-606X.220118

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Nitrogen oxides (NOx) emission of sintering flue gas accounts for more than half of the total NOx emission in the steel industry. With the increasingly stringent environmental regulations, the existed and new sintering machines equipped only with the denitration equipment of flue gas can meet the requirements of NOx emission regulations. Activated carbon has an abundant microporous structure, large specific surface area, and strong absorption capacity. SO2, NOx, dust, and other harmful gases of flue gas can be removed simultaneously by activated carbon at low temperature. Therefore, denitration of sintering flue gas on activated carbon has significant technical characteristics and advantages at low temperatures. However, the poor sulfur and water resistance of activated carbon limits its wide utilization in the denitration of low-temperature flue gas. The denitration mechanism of low-temperature flue gas on activated carbon was reviewed in this work, and three denitration mechanisms were described in detail, namely physical adsorption, chemical adsorption and selective catalytic reduction (SCR) reactions. The oxidation as a result of the presence of oxygen in flue gas can effectively improve the denitration efficiency of flue gas on activated carbon. However, the competitive adsorption of SO2, H2O, and NO in flue gas can reduce the denitration performance of activated carbon. The inhibition and influence of SO2 and H2O on the denitration of low-temperature flue gas over activated carbon was also discussed. Chemical modification of activated carbon loading transition metal oxides and rare earth metal oxides and their effect on the activity of activated carbon were described. The mechanism of activity improvement of activated carbon loading transition metal oxides and rare earth metal oxides was also reviewed. The loading of multi-metals oxides on activated carbon and their synergistic effects on performance improvement of activated carbon were also introduced. Finally, the research direction and the industrial application of low-temperature denitration technology of sintered flue gas on activated carbon were prospected.

Staged injection and aerodynamic characteristics of staggered lobe nozzles in aeroengine combustor

Lijun WANG Kuo MEN Yijun XU

The Chinese Journal of Process Engineering. 2021, 21(5): 506-515. DOI: 10.12034/j.issn.1009-606X.220057

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A 13 lobe nozzles with a 5×5 fork row aero-engine staged combustion chamber water model test bench was set up to achieve different working loads by changing the staged injection mode of each nozzle. The aerodynamic flow field characteristics of the model combustion chamber under two kinds of loads, such as 30% and cruise, were studied by water simulation tracer experiments and mathematical modeling under the two-stage and three-stage combustion organization modes. The aerodynamic characteristics of complex vortex structure and vorticity induced by each level of flap nozzle in size, shape, interaction and evolution were studied by experiments and numerical simulation for the two fractional combustions when the oil and gas ratio under the two loads was changed. The results showed that the vortex structure of the two kinds of staged injection modes can be divided into initial section, transition section and development section. The vortex systems have undergone evolution and interaction from independence to merger and reorganization, and then evolve into new vortex systems. When the oil?gas ratio increased, it had a greater impact on the transition of the two kinds of staged injections. The calculation results of the air and water model flow fields were consistent with the experimental results, which verified the feasibility and credibility of the research results.

Numerical simulation of dust-cleaning performance of new structure microporous membrane filter plate

Zhe LIU Lumin CHEN Fuping QIAN Mengmeng YE Min WEI Yunlong HAN Jinli LU

The Chinese Journal of Process Engineering. 2021, 21(5): 516-529. DOI: 10.12034/j.issn.1009-606X.220126

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In order to explore the influence of different factors on the dust-cleaning performance of the new structure microporous membrane filter plate used in the rotary pulse-jet cleaning microporous membrane dust collector, the CFD method was used to simulate the flow field of pulse-jet cleaning, and the accuracy of the numerical calculation model was verified by comparing with the experimental data in the literature. On this basis, the influence of pulse-jet pressure, pulse-jet distance, diameter ratio of the end to the inlet of the injection pipe, nozzle diameter, and length of filter plate on the average peak pressure of the wall surface of the new structure filter plate were studied, and the law of the change of the side pressure of filter plate with the pulse-jet time was explored. At the same time, a five-factor three-level orthogonal test was designed, and the average peak pressure of the filter plate was used as the design index to analyze and obtain the best pulse-jet cleaning system parameters. The results showed that the average peak pressure of the filter plate can be increased by increasing the pulse-jet pressure, the nozzle diameter and reducing the diameter ratio of the end to the inlet of the injection pipe, which was beneficial to improve the dust-cleaning performance of the new structure microporous membrane filter plate. The pulse-jet distance had little effect on the average peak pressure of the filter plate wall, but increasing the pulse-jet distance can effectively reduce the size of the negative pressure at the top of the filter plate, the reduction of the negative pressure on the top of the filter plate was beneficial to increase the service life of the microporous membrane filter plate. The side pressure of the filter plate changed with the pulse-jet time, making the filter plate at different times. The pressure distribution of the side wall was different. With the increase of the length of the filter plate, it had a negative impact on the dust-cleaning effect of the middle and lower part of the new structure microporous membrane filter plate.

Performance analysis of dimpled tube based on skewness and kurtosis

Wenling LIAO

The Chinese Journal of Process Engineering. 2021, 21(5): 530-540. DOI: 10.12034/j.issn.1009-606X.220101

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In this work, the numerical simulation model of the hexagonal tube with different parameter dimples has been established considering thermal-hydraulic performance. The effect of dimple types, dimple depth, and dimple diameter on the flow field characteristics, and heat transfer characteristics of dimple tubes were discussed under Reynolds numbers between 5000 and 40000. Skewness and kurtosis of dimpled tube wall surface were calculated by discrete method, and then the thermal-hydraulic performance of dimpled tube was analyzed based on the influence of dimple parameters on skewness and kurtosis. The results showed that the dimpled tube had a better thermal-hydraulic performance due to the recirculation flows and flow separation was a significant increase, and the effect of pit dimple was better than that of bulge dimple. In addition, the influence of different dimple types was that the less the skewness, the better the thermal-hydraulic performance of the heat transfer tube. However, for the pit dimple tube, the larger skewness and the smaller the kurtosis was, the better comprehensive performance of the thermal-hydraulic got. With the increase of the pit dimple depth and diameter, the skewness gradually increased, while the kurtosis value gradually decreased.

Numerical simulation of influence of fiber layers with different arrangement structures on performance of PM2.5 capture

Minghao CHU Yongfa DIAO Li'an ZHANG Jiawei ZHUANG

The Chinese Journal of Process Engineering. 2021, 21(5): 541-549. DOI: 10.12034/j.issn.1009-606X.220152

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Based on the discrete phase model, the trapping performance of fiber layers with different arrangement structures under two trapping mechanisms of interception and inertial impaction was simulated by numerical simulation method. The effects of particle diameter, inlet velocity and fiber layer filling rate on the trapping performance of fiber layers with different arrangement structures were analyzed. The results showed that large particle size particles with inertial impaction as the main trapping mechanism were more easily affected by the arrangement structure of fiber layers. The vertical arrangement structure effectively improved the trapping performance of large particle size particles by fiber layers, and the trapping performance showed a trend of increasing first and then decreased with the increase of particle diameter. The trapping efficiency of fiber layers with different arrangement structures for large particle size increased with the increase of inlet velocity. The trapping efficiency of fiber layers with single-layer vertical arrangement structure was higher than that of the other two arrangement structures, and its trapping performance decreased with the increase of inlet velocity. The trapping efficiency of fiber layers with different arrangement structures increased with the increase of filling rate, while the trapping performance decreased with the increase of filling rate. Compared with the fiber layers with the three arrangement structures, under the conditions of low filling rate and low inlet velocity, the single-layer vertical arrangement structure fiber layer had the most obvious improvement in the trapping performance of large particle size particles. The single-layer vertical arrangement structure fiber layer had the highest trapping rate for particulate matter.

Effect of area ratio of variable cross-section dividing manifolds on performance of fluid distribution in high Reynolds number

Honggang YANG Nan WANG Yi WANG Lei YAO Xiaofan CAI

The Chinese Journal of Process Engineering. 2021, 21(5): 550-557. DOI: 10.12034/j.issn.1009-606X.220393

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As a fluid distribution device, the dividing manifold is widely used in engineering systems such as air supply ducts, heat exchangers, and large bag filters. The flow distribution uniformity of the dividing manifold directly affects the overall performance of the system. A geometric model of dividing manifold was proposed to prevent dust accumulating with consideration of the problem of preventing dust and particles from accumulating in dust-containing airflow in practical engineering. With the aim of providing theoretical guidance and basis for the design of shunt manifold, the numerical simulation study on the fluid distribution performance of dividing manifolds with different main pipe shapes and area ratios was carried out to obtain the optimal flow distribution uniformity of the dividing manifold. The effects of Re, main pipe shape and area ratio (AR) on the flow distribution performance of the dividing manifold were analyzed. The results showed that at high Reynolds number, the flow distribution uniformity of dividing manifold was hardly affected by the inlet Reynolds number. When the inlet Reynolds number and area ratio remained unchanged, the flow distribution uniformity of the manifold with a triangular main pipe shape was obviously better than that of the other two main pipe shapes. As the increase of area ratio of the dividing manifold, the flow distribution uniformity index U of the dividing manifold generally decreased. When the area ratio was greater than 1.0, the flow distribution uniformity of all dividing manifolds was decreased. When the area ratio was between 0.8 and 1.0, the flow distribution uniformity index of dividing manifold did not change significantly.

Analysis and evaluation of oil-water two-phase centrifugal separation performance in horizontal pipe

Lei XING Minghu JIANG Lixin ZHAO Yi QIAO Guoxin HAN

The Chinese Journal of Process Engineering. 2021, 21(5): 558-566. DOI: 10.12034/j.issn.1009-606X.221002

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The particle image velocimetry technology, separation performance experiment and numerical simulation methods of separation performance were applied to analyze the separation performance of three kinds of hydrocyclones. The method for evaluating the performance of oil?water two-phase separation in a horizontal circular pipe was established. The results showed that the helix separator and the diversion vane separator can form axial reflux in a axial central region of the flow field, and there were different locus of zero vertical velocity in the two structures. When the inlet Reynolds number was 6.68×104, although the diversion vane separator formed a rotating flow with the maximum tangential velocity, the attenuation rate of tangential velocity was also the largest, and the value of maximum tangential velocity attenuation rate within the 500 mm length was 94.05%. The oil core formed by the helix separator had a better degree of aggregation with the maximum oil volume fraction at the axis of the pipe. In order to quantitatively evaluate the performance of separators with different structures, the calculation method of oil?water separation efficiency in circular pipe was established by taking the concentration of oil core and the extension length of oil core in the pipe. By comparing the separation efficiency of the three structures under different Reynolds numbers, the helix separator showed the best separation performance. When the inlet Reynolds number increased in the range of 4.14×104~10.7×104, the oil?water separation efficiency of the helix separator increased from 16.6% to 82.1%, which was higher than those of the other two structures. The evaluation results of oil?water separation efficiency showed the consistent regularity as the experimental results, which verified the accuracy of the proposed separation efficiency evaluation method.

Dynamic adsorption of low concentration gallium ion by LX-92 resin in sulfuric acid system

Chaolu WEN Zhenhua SUN Shaopeng LI Zhibin MA Huiquan LI

The Chinese Journal of Process Engineering. 2021, 21(5): 567-578. DOI: 10.12034/j.issn.1009-606X.220142

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The dynamic adsorption-desorption behavior of gallium in simulated sulfuric acid leach solution of fly ash on polystyrene resin (LX-92) was investigated by fixed bed device. The dynamic adsorption process was analyzed by Thomas, Yoon-Nelson, and Adam-Bohart empirical models. The results showed that decreasing the flow rate (Fad) and the initial concentration of gallium(III) (C0), increasing the bed height (Z) were conducive to improve the fixed bed adsorption efficiency and equilibrium adsorption capacity. According to experiments data, the optimum conditions for dynamic adsorption process was as follow: Fad=5.0 mL/min, C0=260 mg/L and T=55℃, and the maximum adsorption capacity was 56.65 mg/g. The elution rate of gallium could reach 94.40% at the conditions of 3.0 mol/L H2SO4 and 1.0 mL/min flow rate. After the process of adsorption and desorption, the concentration of gallium ions could be enriched more than 10 times. The dynamic adsorption behavior of gallium by the resin was well fitted by the Yoon-Nelson dynamic adsorption model. The corresponding equations of the dynamic adsorption rate constant KYN and the half-through time τ value constant with the initial Ga(III) ion concentration, flow rate, and bed height were established. The dynamic adsorption results would be used for engineering purpose of the of low-concentration gallium ions recovery.

Factors affecting the critical flux in a forward osmosis membrane process

Ye YANG Rui TANG Yuzhu SUN Xingfu SONG Jianguo YU

The Chinese Journal of Process Engineering. 2021, 21(5): 579-586. DOI: 10.12034/j.issn.1009-606X.220134

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Critical flux is an important concept in fouling control for membrane-based processes. Operation below the critical flux can maintain the membrane flux and reduce the maintenance cost which is associated with membrane cleaning and replacement in forward osmosis (FO) processes. In this research, the effects of foulant type, binding ions concentration, and cross-flow velocity on the critical flux in FO processes were investigated using a draw solution concentration stepping method. The results showed that the draw solution concentration stepping was feasible for the critical flux determination in FO processes. The thin-film composite (TFC) membranes exhibited a low critical flux for sodium alginate (SA) fouling with a value of 29.32 L/(m2?h), then followed nano-silica (SiO2) with a critical flux value of 32.17 L/(m2?h) and humic acid (HA) of 46.35 L/(m2?h). This indicated that the critical flux behavior in FO processes was dependent on the properties of both the membrane and foulants, including the membrane surface roughness, intermolecular adhesion of foulants, and the interaction between foulants and membrane. The atomic force microscopy (AFM) results revealed the deposition of foulants onto the ridge-and-valley structure of the membrane surface, leading to the deviation of water flux from the baseline with the increasing draw solution concentration. As the Ca2+ concentration increased from 0 mmol/L to 10 mmol/L, the critical flux for alginate fouling dramatically decreased from 29.22 L/(m2?h) to 9.48 L/(m2?h), which can be attributed to the interaction between alginate and membrane as well as the intermolecular aggregation of alginate and the interaction by Ca2+ binding. Moreover, the critical flux for SA?Ca2+ complexes fouling increased from 9.48 L/(m2?h) to 31.59 L/(m2?h) with the cross-flow velocity ranging from 5 cm/s to 15 cm/s, which indicated the improvement of the solution turbulence can enhance the critical flux, thereby expanding the operating ranges of flux.

Green synthesis of m-xylylene dicarbamate using urea as carbonylation reagent

Xiaoyu HUANG Junya CAO Fenggang HAN Liguo WANG Yan CAO Peng HE Shuang XU Jiaqiang CHEN Fan YI Huiquan LI

The Chinese Journal of Process Engineering. 2021, 21(5): 587-593. DOI: 10.12034/j.issn.1009-606X.220087

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M-xylylene diisocyanate (XDI) is an important special isocyanate that draws more and more attention in recent years. The introduction of the –CH2– group between the benzene ring and isocyanate group, which makes it resistant to yellowing, can be applied in the fields of high value-added polyurethanes, such as high-grade coatings, medical polyurethane, high-grade optical polyurethane, and so on. M-xylylene dicarbamate (XDC) is the key intermediate for the synthesis of XDI via the non-phosgene thermal decomposition route. In this work, a novel methodology for the synthesis of XDC via carbonylation of m-xylylenediamine (XDA) using urea as carbonylation reagent over TiO2 catalyst was proposed. The standard XDC sample was first synthesized by the reverse reaction between XDI and ethanol, and then, the qualitative analysis of the standard XDC sample was characterized by FT-IR and 1H-NMR to confirm its structure. The standard curve of XDC was then successfully established in liquid chromatography with a correlation coefficient of more than 0.999. The qualitative analysis of the target product was carried out by GC-MS, and the reaction path was primarily speculated. Furthermore, the effects of different catalysts, reaction temperature, reaction time, the molar ratio of raw materials, and catalyst dosage on the yield of XDC were studied. The results showed that using TiO2 as the catalyst, under the optimized conditions, the reaction temperature of 205℃, the reaction time of 6 h, n(urea):n(XDA) of 3:1, the amount of catalyst was 15wt% XDA, the conversion of XDA was 100%, and the yield of XDC could reach to as high as 82.4%. Therefore, this process not only provides a feasible route for green, effective, and economic production of XDC, but also provides a theoretical basis for the non-phosgene synthesis of special isocyanate XDI.

Preparation of a Pickering emulsion for treatment of bacterial biofilm infection

Xieru BAO Jie WU Guanghui MA

The Chinese Journal of Process Engineering. 2021, 21(5): 594-600. DOI: 10.12034/j.issn.1009-606X.220140

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Bacterial biofilms are closely associated with persistent infections. E?ective penetration of antibacterial drugs is necessary for the treatment of bacterial biofilms. In this study, a nanoparticle-stabilized Pickering emulsion with strong permeability and high antibacterial activity was fabricated for the treatment of bacterial biofilms. This Pickering emulsion was composed of clove oil core and chitosan nanoparticles. The clove oil was used as an antibacterial agent, and the chitosan nanoparticles provided a positively charged shell, which could interact with the negatively charged extracellular matrix to achieve strong penetration through bacterial biofilms. Both of the chitosan nanoparticles and the Pickering emulsion with narrow size distribution and good dispersity were prepared successfully. The average size of chitosan nanoparticles was 590.30±3.90 nm with 0.125±0.003 of polydispersity index (PDI), and the average Zeta potential was 15.60±0.40 mV. The average size of the Pickering emulsion was 2312±53 nm with 0.137±0.013 of PDI, and the average Zeta potential was 26.45±0.55 mV. The experiments of bacterial biofilms penetration and antibacterial test revealed that the Pickering emulsion could effectively penetrate the bacterial biofilms and kill bacteria. Besides, the cytotoxicity test in vitro showed that the Pickering emulsion had good biosafety. All these results indicated that the Pickering emulsion had promising prospects for the treatment of persistent infections associated with bacterial biofilms.

Impacts of operating parameters of closed-type heating tower on the performance of heat pump system

Rong FENG Ye LIU Xin MENG

The Chinese Journal of Process Engineering. 2021, 21(5): 601-608. DOI: 10.12034/j.issn.1009-606X.220079

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The fan of the heating tower and circulation pump for the antifreeze solution of the heating tower are the main electrical equipment in the heating tower heat pump system, besides the compressor. By controlling the working frequencies of the fan of the heating tower and circulating pump for the anti-freezing solution, the effects of operation parameters of the closed-type heating tower on its heat absorption and the performance of its heat pump system were investigated under heating conditions in winter. The results indicated that, firstly, the reduced fan?s frequency leads to the heat absorption capacity of the heating tower reduced, as well as the system?s heating capacity and the COP. However, the SEER was increased. Secondly, the reduced frequency of circulating pump results in the heat absorption capacity of the heating tower increased firstly and then decreased, and the maximum heat absorption capacity was achieved when the frequency of the circulating pump was 25 Hz. In addition, the heating capacity of the system also increased firstly and decreased later, but with the fan?s frequency increasing, the frequency of the circulating pump which was related to the maximum heating capacity was altered from 35 Hz to 25 Hz, and the increase in frequency caused the COP increased but SEER decreased. Thirdly, when the frequency of the fan and pump dropped to 15 Hz, the evaporation temperature of the heat pump decreased, and it led the compressor works under a high compression ratio, which was not favorable for the safe operation of the heat pump. Fourthly, the maximum heating capacity exceeded 14.30 kW, the maximum COP was up to 3.31, and the maximum SEER was up to 2.37.

Molecular size distribution characteristics of cellulose pyrolysis bio-oil

Yasi WANG Kaiyin ZHANG Huili LIU Baoping DING Min ZHENG

The Chinese Journal of Process Engineering. 2021, 21(5): 609-616. DOI: 10.12034/j.issn.1009-606X.220097

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The shape selectivity of molecular sieve catalyst is caused by the difference between the pore size of molecular sieve catalyst and the molecular size of bio-oil. The data of the pore size of molecular sieve catalysts are derived from crystal structural analysis, while the data of the molecular size of bio-oil are rather difficult to obtain. It is very necessary to estimate the molecular size of bio-oil. The pyrolysis of cellulose was carried out by prolysis-gas chromatography/mass spectrometry (Py-GC/MS), and the variation of the composition of cellulose pyrolysis bio-oil with the temperature was studied. The kinetic diameter of the components of cellulose pyrolysis bio-oil were calculated on the basis of Joback group contribution method, and the characteristics of molecular size distribution were analyzed. The results showed that cellulose pyrolysis bio-oil was mainly composed of anhydrosugars, furan derivatives and ketone compounds in the temperature range from 350℃ to 600℃. The kinetic diameter of cellulose pyrolysis bio-oil were mainly distributed in the range of [0.500, 0.600) nm. When the pyrolysis temperature increased from 350℃ to 600℃, the peak area of bio-oil molecules with the kinetic diameters in the range of [0.550, 0.600) nm decreased from 88.72% to 64.53%, and the peak area of bio-oil molecules with the kinetic diameters in the range of [0.500, 0.550) nm increased from 2.88% to 21.95%. For the preparation of high-quality liquid fuels by catalytic cracking of cellulose, molecular sieve catalysts ZSM-5, ZSM-11 and IM-5 with pore size of 0.500 to 0.600 nm can be selected.

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