Effect Of Reflux Ratio Research Articles

Effect of Reflux Ratio on Performance of Pyrite-Based Mixotrophic Sequencing Batch Biofilm Reactor Treating Real Domestic Wastewater

Effect of Reflux Ratio on Performance of Pyrite-Based Mixotrophic Sequencing Batch Biofilm Reactor Treating Real Domestic Wastewater

The effect of reflux ratio on sulfur disproportionation tendency in anaerobic baffled reactor with the heterotrophic combining sulfur autotrophic processes under high concentration perchlorate stress.

In a laboratory scale, an anaerobic baffled reactor (ABR) consisting of eight compartments, the heterotrophic combining sulfur autotrophic processes under different reflux ratios were constructed to achieve effective perchlorate removal and alleviate sulfur disproportionation reaction. Perchlorate was efficiently removed with effluent perchlorate concentration below 0.5 μg/L when the influent perchlorate concentration was 1030 mg/L during stages I ~ V, indicating that heterotrophic combining sulfur autotrophic perchlorate reduction processes can effectively achieve high concentration perchlorate removal. Furthermore, the 100% reflux ratio could reduce the contact time between sulfur particles and water; thus, the sulfur disproportionation reaction was inhibited. However, the inhibition effect of reflux on sulfur disproportionation was attenuated due to dilute perchlorate concentration when a reflux ratio of 150% and 200% was implemented. Meanwhile, the content of extracellular polymeric substances (EPS) in the heterotrophic unit (36.79 ~ 45.71 mg/g VSS) was higher than that in the sulfur autotrophic unit (22.19 ~ 25.77 mg/g VSS), indicating that high concentration perchlorate stress in the heterotrophic unit promoted EPS secretion. Thereinto, the PN content of sulfur autotrophic unit decreased in stage III and stage V due to decreasing perchlorate concentration in the autotrophic unit. Meanwhile, the PS content increased with increasing reflux in the autotrophic unit, which was conducive to the formation of biofilm. Furthermore, the high-throughput sequencing result showed that Proteobacteria, Chloroflexi, Firmicutes, and Bacteroidetes were the dominant phyla and Longilinea, Diaphorobacter, Acinetobacter, and Nitrobacter were the dominant genus in ABR, which were associated with heterotrophic or autotrophic perchlorate reduction and beneficial for effective perchlorate removal. The study indicated that reflux was a reasonable strategy for alleviating sulfur disproportionation in heterotrophic combining sulfur autotrophic perchlorate removal processes.

Establishment and optimization of sulfur-based autotrophic-heterotrophic denitrification biofilters for advanced post-anaerobic treatment of effluent from kitchen wastewater and landfill leachate under low temperature

Landfill leachate treatment is a major challenge in wastewater treatment. In this study, two sulfur-based autotrophic-heterotrophic denitrification biofilters (Ra biofilter with room-temperature molded filler and Rb biofilter with melt molded filler) were used to treat kitchen-landfill leachate at low temperatures. The effects of reflux ratio, concentrations of NaHCO3, and Na2S2O3 on the total nitrogen removal efficiency were analyzed, and based on response surface methodology, the optimum parameters were determined. After optimization, the total nitrogen removal efficiency for the Ra and Rb biofilters increased by 83% and 81%, respectively. Moreover, sulfur-based autotrophic denitrification accounted for more than 70% of the nitrogen removal in both biofilters. Based on high-throughput sequencing results, the functional bacteria exhibited high abundance in the Ra biofilter, indicating that the room-temperature molded filler favored the enrichment of functional bacteria. These findings were important for optimizing the operation of sulfur autotrophic-heterotrophic denitrification biofilters at low temperatures.

Simulation Studies on Recovery of Acetonitrile from Aqueous Acetonitrile Waste from Pharmaceutical Processes

This paper presents simulation studies on the recovery of Acetonitrile from aqueous Acetonitrile waste from pharmaceutical processes. The focus is on atmospheric distillation in two sequential columns to understand the separation feasibility of the system; the first column produces a distillate of azeotropic composition, which is mixed with a fresh stream and fed to a second column, which produces a 99.9% pure Acetonitrile in the residue. The effect of reflux ratio, reboiler duty and the fresh stream flowrate on the purity of the product is analyzed. The study was performed using steady state simulator Aspen Plus, version 11.1. The simulation results indicate that it is possible to obtain a product of 99.9% w/w Acetonitrile from a 1:1 feed with a recovery of ~ 60%.

Investigation of material cost of an ethane-ethylene rectification column

In this study with the tray-by-tray method an ethane-ethylene rectification column was studied. Therefore, the effect of reflux ratio on the material cost of ethane-ethylene rectification column was investigated. In case of the modification of reflux ratio the diameter of the column and the number of trays will modify. Not only these parameters, but also the required wall thickness for strength was determined. In case of the investigated column between the reflux ratio and the diameter of the column there is second degree polynomial relationship. There is a minimum point of the material cost function, which belongs to the optimal reflux ratio.

A combined deodorization reflux system and tidal flow constructed wetland for sewage treatment performance

The biggest problem in the treatment of septic tank wastewater of scattered farmers is the high concentration of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total phosphorus (TP), and odor (threshold odor number, TON). A combined process of reflux deodorization and tidal flow constructed wetland was developed, and its removal efficiencies of COD, NH4+-N, TP, sulfide (S2-), and TON were evaluated. The effect of reflux ratio on system pollutant removal is significant. The removal efficiencies of COD, NH4+-N, S2-, and TON increased as R increased. When R is 150%, the system achieves the optimal operation effect. By analyzing the microbial community and functional bacteria in the system, it was found that Thiobacillus could conduct simultaneous denitrification and deodorization in the deodorization pool. The effects of ρ(NO3--N)/ρ(S2-) and ρ(COD)/ρ(NO3--N) on the denitrification and deodorization of the deodorization pool were studied to further reveal the mechanism and law of denitrification and deodorization in the deodorization pool. It was found that with the increase of ρ(NO3--N)/ρ(S2-), the denitrification effect of the deodorizing pool decreased and the deodorization effect increased. When ρ(NO3--N)/ρ(S2-) is 0.8, good denitrification and deodorization effect can be achieved in the deodorization pool. With the increase of ρ(COD)/ρ(NO3--N), the denitrification effect of the deodorizer was enhanced, but the deodorization effect was weakened. When ρ(COD)/ρ(NO3--N) is 4, good denitrification and deodorization effect can be achieved in the deodorization pool.

Effects of reflux ratio on the anaerobic sludge and microbial social behaviors in an expanded granular sludge bed reactor: From the perspective of acyl-homoserine lactones-mediated quorum sensing

Performance of anaerobic sludge and microbial social behaviors in an expanded granular sludge bed (EGSB) were evaluated by increasing reflux ratio from 50% to 500% stage by stage, with a constant influent chemical oxygen demand (COD) of 5500 mg/L at hydraulic retention time 12 h. The results indicated that the reflux ratio of 100% − 200% was more favorable for the EGSB with a methane production of 2.4 m3/m3·d. It was found that acyl-homoserine lactones (AHLs)-mediated quorum sensing (QS) could balance various microbial populations in the anaerobic digestion process. C4-HSL and C8-HSL were identified as the specific AHLs in enhancing granulation of anaerobic sludge by stimulating protein secretion into extracellular polymeric substances (EPS). 3-oxo-C6-HSL and 3-oxo-C14-HSL were verified for the enhancement of methanogenesis. The present study showed a novel perspective on the performance of EGSB with reflux ratios based on the AHLs-mediated QS.

Simulation analysis of R134a/DMF absorption refrigeration system based on Aspen Plus

In order to explore the performance of R134a / DMF absorption refrigeration system, a model of R134a/DMF absorption refrigeration system was conducted based on Aspen Plus software. The cooling capacity of the system 150kW. The effects of reflux ratio, bottom temperature and refrigerant (R134a) concentration on the system were simulated and analyzed. The results showed that, the reasonable range of reflux ratio and scope of bleed is 0.5∼0.7. The system COP is the best when the mass fraction of R134a, the generating temperature and absorption temperature is respectively 56 %, 131°C and 28 °C.

Nitrogen removal from domestic wastewater in a novel hybrid anoxic-oxic biofilm reactor at different reflux ratios.

A lab-scale hybrid anoxic-oxic biofilm reactor (HAOBR) with one anoxic compartment and two oxic compartments in sequence was constructed to treat domestic wastewater in this study. Performance of the HAOBR was evaluated at 25°C and hydraulic retention time 12hr with reflux ratio increased from 100% to 300% by stages. The results showed that COD, , and TN removal presented an increasing trend with the increase of reflux ratio by stages. At the optimal reflux ratio of 300%, removal of COD, , and TN averaged 83.9%, 99.0%, and 80.8%, respectively. Analysis about pollutant concentration in each compartment of the HAOBR revealed that the excellent pollutant removal was mainly achieved by the cooperation of nitrification in 3rd oxic compartment and denitrification in 1st anoxic compartment. Denitrification in the anoxic zone of 2nd oxic compartment would also contribute to the nitrogen removal. The higher nitrogen removal of the HAOBR at the reflux ratio of 300% is attributed to the presence of the anammox in the 1st anoxic compartment, which is mainly due to the lower COD concentration in the compartment at the higher reflux ratio. PRACTITIONER POINTS: A hybrid anoxic-oxic baffled reactor was built to treat domestic wastewater. Effect of reflux ratio and mechanism of nitrogen removal were investigated. Reflux ratio 300% was favorable for COD, and TN removal. The removal of COD, and TN averaged 84.4%, 99.0% and 80.8%, respectively. Cooperation of nitrification, denitrification and anammox dominated the high nitrogen removal at the higher reflux ratio of 300%.

Influence of reflux ratio on the anaerobic digestion of pig manure in leach beds coupled with continuous stirred tank reactors

The effect of reflux ratio on the anaerobic mono-digestion of pig manure (PM) in leach beds coupled with continuous stirred tank reactors (CSTRs) has been studied in this work, and contents of volatile fatty acids (VFAs) and biogas yields were determined for three groups of leach bed reactor (LBR) – CSTR systems. The obtained results indicated that the reflux of biogas slurry increased both the pH of the acid-producing phase and acetic acid yield and repeatedly degraded the refractory organic matter in the biogas slurry. The larger reflux ratio increased the inoculation volume and substantially enhanced the mass transfer process. The maximum values of the biogas and methane yields equal to 259.49 and 167.44 mL/g volatile solids, respectively, were achieved at a reflux ratio of 100%. Moreover, the weight of the PM leachate residue was reduced by 94.14%, and the total nutrient content (N + P2O5 + K2O) was relatively high (1.48%), which was suitable for vegetable seedling substrates. In conclusion, during the treatment of PM in LBR–CSTRs, the solid phase remains on the leach bed, and the leachate is supplied to a biogas tank, which effectively increases its stability of operation.

Simulation and energy optimization of a reformate stabilizer unit in a petrochemical plant

ABSTRACTIn this study, the reformate stabilizer tower of a petrochemical plant has been investigated for the first time. The main goal of this distillation tower is to separate light components and liquid gas from the reformate product. In order to simulate and optimize the distillation tower and determine the optimum reflux ratio, Aspen HYSYS was used. In order to study the characteristics of non-ideal multicomponent mixture in a stabilizer distillation tower, a stable simulation model was used. Peng–Robinson equation of state was used as the suitable equation of state for this separation that has high accuracy for hydrocarbon systems. The comparison between results and real values proves the validity of the model. The effect of reflux ratio as an independent variable on flow parameters of reformate product, penthane’s flow rate in liquid gas product, and energy consumption in reboiler and condenser was studied, and it was found that the optimum amount of reflux ratio for the stabilizer tower is equal to 4.8. However, the reflux ratio in the current procedure is 6.96. The stabilizer tower was re-simulated with optimum reflux ratio, and the results were promising. Energy consumption of reboiler was reduced by 12.67 percentage, and for condenser, it was reduced by 27.05 percentage.

Dynamic Analysis for the Multi-Steady States in the Dividing Wall Column

The feature of multiple steady states (MSS), a common characteristics phenomenon existing in the fully thermal coupled distillation configurations (dividing wall column, DWC), has a significant effect on the operational costs in the chemical process. Reflux ratio, as an important variable, which connects very directly to the energy cost, was chosen to investigate MSS, namely, exploring its effect on the number of steady states for dividing wall column. In this paper, the effect of reflux ratio on multi-steady states in the thermal coupled distillation column was investigated using Aspen plus simulator and origin software aimed at providing a necessary guidance to engineers and researchers in industrial design and actual operation. In addition, the analysis of differences among these steady states under the same reflux ratio was carried out, based on the dynamic simulation, which can bring a new approach to select the real best design and operational parameters for the chemical process.

Effect of reflux ratio on nitrogen removal in a novel upflow microaerobic sludge reactor treating piggery wastewater with high ammonium and low COD/TN ratio: Efficiency and quantitative molecular mechanism

A novel upflow microaerobic sludge reactor (UMSR) was constructed to treat manure-free piggery wastewater with high NH4+-N and low COD/TN ratio. In the light of the potential effect of effluent reflux ratio (RR) on nitrogen removal, performance of the UMSR was evaluated at 35°C and hydraulic retention time 8h with RR decreased from 45 to 25 by stages. A COD, NH4+-N and TN removal of above 77.1%, 80.0% and 86.6%, respectively, was kept with a RR over 35. To get an effluent of TN not more than 80mg/L with a TN load removal above 0.88kg/(m3·d), the RR should be at least 34. Real-time quantitative polymerase chain reaction of functional bacteria revealed that the RR of less than 34 stimulated ammonium oxidation but badly inhibited anammox, the dominant nitrogen removal pathway, resulting in the remarkable decrease of nitrogen removal in the reactor.

Microwave Reactive Distillation Process for Production of Ethyl Acetate

A novel intensification technology–microwave reactive distillation (MRD) process was developed by coupling the microwave irradiation and reactive distillation (RD) process to break through the limitations of the RD process, such as low esterification reaction rate. The batch MRD process and RD process for acetic acid and ethanol esterification were compared by using a laboratory-scale RD packed column with strong acidic ion-exchange resin as catalyst. The effects of reflux ratio, feed flow rate, microwave power, and reboiler heating power were investigated. The results showed that, with the same total energy consumption, MRD needed less time than RD to obtain 70% overhead EtAc content. Compared with the RD process, the instantaneous improvement of ethyl acetate content achieved by MRD was up to 6.9% under same reflux ratio, and 6.7% under same acetic acid feed flow rate. The variation trend of experimental results matched that of the numerical simulation results.

Microwave-assisted continuous reactive distillation process for preparation of ethyl acetate

AbstractAs a novel process intensification technology, microwave-assisted continuous reaction distillation (MRD) was proposed for the esterification reaction and separation of ethyl acetate (EtOAc). The effects of reflux ratio, mole ratio of acetic acid (HOAc) to ethanol (EtOH), reboiler duty, microwave power on EtOH conversions, EtOAc purity and mass ratio of distillate to feed (D/F) were explored. In comparison with conventional heating, the experimental results revealed that the EtOAc purity in the distillate under microwave conditions (MC) was improved. Computer simulations for conventional and MRD systems were performed using the Aspen Plus non-equilibrium stage model to substantiate the experimental results. The model predictions are in good agreement with the experimental data, revealing the accuracy and reliability of the non-equilibrium model. This new MRD process can be an effective and productive method of ester production.

An investigation in the effects of recycles on laminar heat transfer enhancement of parallel-flow heat exchangers

It was demonstrated that fluid recycling could effectively enhance heat transfer rates of heat exchangers, however, related investigations were limited. In the current work, parallel-flow heat exchangers with basic recycles or revised recycles are investigated in the laminar regime. Theoretical models of thermo-hydraulic performances are established. The effects of reflux ratio, capacitance rate ratio, heat transfer area, and recycle length are investigated. The results demonstrate that the dimensionless heat transfer rate rises with the increase of reflux ratio or capacitance rate ratio, or with the decrease of heat transfer area, and the maximum values reach up to 127% and 121% for basic internal and external recycles, respectively. Basic internal recycles generate larger dimensionless heat transfer rates under larger reflux ratios, while basic external recycles perform more reliably over the whole reflux ratio range. Compared with basic recycles, revised recycles (i.e., partial-length recycles) require smaller pumping powers. Thus, partial-length recycles can improve the dimensionless overall performance of full-length recycle heat exchangers, e.g., half-length recycles increase the dimensionless overall performance by 65%. Fluid recycling does not need to change geometrical structures and fluid flow rates, thus it is a competitive approach of thermal augmentation in heat exchangers.

A New Simulation Model for Design of Distillation Column in a Bio-ethanol/Water System: Effect of Reflux Ratio

Fuel ethanol research development deals with process design integration for improving production of ethanol. This paper investigates the effect of variable reflux ratio on the design of distillation column using developed JAVA based simulation software. This was done by varying reflux ratio as an input parameter and observed the effect it has on the number of trays that produced the column height. Varying reflux ratio arbitrarily from 3.094 to 9.301 produced column height ranging between 5.897 and 6.232 respectively. With the feed composition of ethanol -water mixture set at 45 percent, and the minimum reflux ratio of 3.4. The results showed that th e number of trays decreases with increase in reflux ratio

Study on the Refinement of Phenetole

In this work,technological process of the refinement of phenetole by continuous distillation method is introduced and, the effects of reflux ratio, operating pressure and location of feed tray on the distillation process are analyzed. The optimal operating conditions for refining phenetole in laboratory are: operating pressure is 50Kpa, feed tray location is the 35th theoretical plate, total reflux and product outlet location is the 5th plate. The phenetole of high-purity could be obtained with both water and phenol content under 100ppm.

Simulation for Transesterification of Methyl Acetate and n-Butanol in a Reactive and Extractive Distillation Column Using Ionic Liquids as Entrainer and Catalyst

A new reactive and extractive distillation process with ionic liquids as entrainer and catalyst (RED-IL) was proposed to produce methanol and n-butyl acetate by transesterification reaction of methyl acetate with n-butanol. The RED-IL process was simulated via a rigorous model, and high purity products of methanol and n-butyl acetate can be obtained in such a process. The effects of reflux ratio, feed mode, holdup, feed location, entrainer ratio and catalyst concentration on RED-IL process were investigated. The conversion of methyl acetate and purities of products increase with the holdup in column, entrainer ratio and catalyst content. An optimal reflux ratio exists in RED-IL process. Comparing to the mixed-feed mode, the segregated-feed mode is more effective, in which the optimal feed locations of reactants exist.

Reactive Distillation for Fischer−Tropsch Synthesis: Feasible Solution Space

Fischer−Tropsch synthesis can be advantageously carried out in reactive distillation (RD) mode. Parametric studies like the effect of reflux ratio, pressure, etc. have been reported in our earlier work [Srinivas et al. Ind. Eng. Chem. Res. 2009, 48, 4719−4730] using Aspen Plus. As an extension of this work, multiparameter sensitivity analysis is performed on a simple RD configuration without side-draws or side-coolers in Aspen Plus, retaining the kinetic and thermodynamic models used previously. A feasible solution space in terms of reflux ratio, pressure, and total catalyst loading is identified and possible reasons for the bounds observed are provided. Changes in the column configuration toward various objectives like maximum conversion, maximum gasoline yield, or selectivity, etc. are also investigated. Regions of interest corresponding to different objectives are represented on a Da−reflux ratio plot.