Treatment of methanol wastewater in external circulation anaerobic reactor with different inoculums

In order to guide the inoculums selection for the anaerobic treatment of methanol wastewater in the engineering application,two 7 L bench-scale external circulation (EC) anaerobic reactors were operated to investigate the inoculums of anaerobic granular sludge and anaerobic digested sludge,focusing on the efficiency and process stability.The effect of impact concentration and temperature on the performance was studied.The results demonstrated that anaerobic granular sludge as the inoculums could complete the start-up more rapidly than the anaerobic digested sludge,and above 90% COD removal were achieved at the organic loading rate of 10 to 15 kgCOD/(m3·d).The effect of impact COD on the methanogenic activity of sludge was weak and the removal efficiencies recovered gradually in the two reactors.The COD removal efficiencies reduced swiftly to 50%-60% due to the impact temperature.The results indicated that the complex bacterial groups in anaerobic digested sludge benefited to enhance the reactor's capacity for withstanding the temperature shock at some extent.

Highly efficient synthesis of 1-methoxy-2-propanol using ionic liquid catalysts in a micro-tubular circulating reactor

The catalysis of ionic liquids (ILs) in the traditional stirred reactor suffers from insufficient mass and heat transfer, which always needs a long reaction time and results in a low reaction rate. In this work, highly efficient synthesis of 1-methoxy-2-propanol via the alcoholysis reaction of propylene oxide (PO) with methanol was proposed and achieved by the combination of micro-tubular circulating reactor with the IL [N4444] [Buty] catalyst. Compared with the stirred reactor, the rate of alcoholysis reaction in a micro-tubular circulating reactor was found to be significantly improved. The reaction time was remarkably shortened to 20 min from 180 min as well as the yield of 1-methoxy-2-propanol reached 92%. Moreover, the kinetic study further demonstrated that the main reaction rate to 1-methoxy-2-propanol (K1) was about 20 times larger than the side reaction rate to byproduct 2-methoxy-1-propanol (K2) in the temperature range of 363–383 K. Such combination of micro-tubular circulating reactor with IL catalysts is believed to be a class of effective process intensification technique for highly efficient synthesis of 1-methoxy-2-propanol.

Numerical simulations and comparative analysis of two- and three-dimensional circulating fluidized bed reactors for CO2 capture

Carbon dioxide(CO2),the main gas emitted from fossil burning,is the primary contributor to global warming.Circulating fluidized bed reactor(CFBR)is proved as an energy-efficient method for post-combustion CO2 capture.The numerical simulation by computational fluid dynamics(CFD)is believed as a promising tool to study CO2 adsorption process in CFBR.Although three-dimensional(3D)simulations were proved to have better predicting performance with the experimental results,two-dimensional(2D)simulations have been widely reported for qualitative and quantitative studies on gas-solid behavior in CFBR for its higher computational efficiency recently.However,the discrepancies between 2D and 3D simulations have rarely been evaluated by detailed study.Considering that the differences between the 2D and 3D simulations will vary substantially with the changes of independent operating conditions,it is beneficial to lower computational costs to clarify the effects of dimensionality on the numerical CO2 adsorption runs under various operating conditions.In this work,the comparative analysis for CO2 adsorption in 2D and 3D simulations was conducted to enlighten the effects of dimensionality on the hydrodynamics and reaction behaviors,in which the separation rate,species distribution and hydrodynamic characteristics were comparatively studied for both model frames.With both accuracy and computational costs considered,the viable suggestions were provided in selecting appropriate model frame for the studies on optimization of operating conditions,which directly affect the capture and energy efficiencies of cyclic CO2 capture process in CFBR.

Cold-modeling study of a circulating fluidized bed reactor for flue gas desulfurization (FGD)

Short residence time of the sorbent in the gas stream and formation of a dense layer of reaction product surrounding its surface influence the sulfur removal efficiency. A practical means of improving the process performance is to employ fluidized bed reaction in replacement of entrained bed reaction on normally used in cool side desulfurizaiton. This paper describes cold modeling study of a circulating fluidized bed reactor. Several aspects of the problem are discussed: fluidization behavior of CaO, attrition of the sorbent and solids entrainment from the fluidized bed. Mechanisms and key controlling parameters are identified, and an integral model based on rate of attrition and mass balance is developed for predicting steady state mass flows and particle size distributions of the system. A process flow scheme is finally presented for conducting desulfurization tests in the second stage of the study.

Insights into sludge granulation during anaerobic treatment of high-strength leachate via a full-scale IC reactor with external circulation system

In this study, a full-scale internal circulation（IC） reactor coupled with an external circulation system was developed to treat high-strength leachate from a municipal solid waste（MSW）incineration plant, in which anaerobic sludge granulation was intensively investigated. Results showed that the IC reactor achieved excellent treatment performance under high organic loading rates（OLR） of 21.06–25.16 kg chemical oxygen demand（COD）/（m3？ day）. The COD removal efficiency and biogas yield respectively reached 89.4%–93.4% and 0.42–0.50 m3/kg COD.The formation of extracellular polymeric substances（EPS） was closely associated with sludge granulation. Protein was the dominant component in sludge EPS, and its content was remarkably increased from 21.6 to 99.7 mg/g Volatile Suspended Solid（VSS） during the reactor operation. The sludge Zeta potential and hydrophobicity positively correlated with the protein/polysaccharide ratio in EPS, and they were respectively increased from-26.2 m V and 30.35% to-10.6 m V and 78.67%, which was beneficial to microbial aggregation. Three-dimensional fluorescence spectroscopy（3 D-EEM） and Fourier transform infrared spectroscopy（FT-IR）analysis further indicated the importance of protein-like EPS substances in the sludge granulation. Moreover, it was also found that the secondary structures of EPS proteins varied during the reactor operation.

Numerical Study on the Process of Chemical Looping Hydrogen Production with Multiple Circulating Fluidized Bed Reactors

Hydrogen is an attractive energy carrier due to the high conversion efficiency and low pollutant emission.Chemical looping hydrogen production(CLHP)is an available way for producing high purity hydrogen with relatively low penalty energy and CO_(2)is captured simultaneously.Three reactors are usually contained for CLHP system including air reactor(AR),fuel reactor(FR)and steam reactor(SR).In current work,we focus on the performance of CLHP system,which is the basement for operation and design.Numerical simulations are carried out for analyzing the flow behavior and the numerical structure is built according to the experimental unit constructed at Southeast University,China.Results show that the operation of L-valve influences most the solid circulating rate of system and particles pass L-valve easily with large aeration rate.Mass distribution results indicate that fuel reactor has the capacity for particles storage.Increase of gas inlet rate of steam reactor leads to more particles leave steam reactor and accumulate into fuel reactor.L-valve can prevent the gas leakage between reactors and it will be adopted for reactive unit.Combining the operation of fuel reactor and L-valve,the system can reach steady state and get the regulating ability.