Liquid Separation Technologies Research Articles

Impacts of Liquid Fractions from Two Solid–Liquid Separation Technologies on the Soil Porosity, Ammonia, and Greenhouse Gas Emissions

Application of organic manure on farmland is one of the most important tasks in agricultural recycling. However, few studies have investigated the potential impact of different solid–liquid separation (SLS) technologies on soil porosity and greenhouse gas (GHG) emissions as a result of the application of liquid fractions (LFs). A microcosm experiment was conducted to track the emissions of ammonia (NH3), nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) from soils (1) without liquid manure application (CK), (2) with a raw dairy slurry (RM), (3) with the liquid fractions of mechanical solid–liquid separation (MS) technologies, and (4) with the LF of an enhanced solid–liquid separation technology including a flocculant (tannic acid, Ta) (MS + Ta). Soil porosities of different treatments were measured using computed tomography (CT). The saturated water conductivities of the RM and MS treatments were 53.38% and 78.63%, respectively, lower than that of the CK. The application of raw slurry and LFs reduced the gas diffusion due to the strong decrease in pore sizes >500 μm and increased gas emissions compared to the CK. Compared with RM, MS had greater N2O and lower CH4 emissions, whereas MS + Ta had lower NH3 and N2O emissions. MS had the greatest CO2-e emissions, mainly owing to high N2O emissions, followed by RM and MS + Ta. The implementation of a simple SLS led to an increase in nitrogen (N) loss and GHG emissions when the resultant LFs were applied to farmlands, whereas high emissions were reduced when a simple SLS was combined with a flocculant, such as Ta. Further research is required to elucidate the reduction mechanism and its effectiveness under field conditions.

Multi-criteria refrigerant screening and performance optimization comparison of a basic and composition-adjustable dual cooling source system

Climate variability and staff mobility have exacerbated the vulnerability of the indoor environment, which calls for air-conditioning units capable of adapting to the active regulation demand of the changing heat and humidity loads. The identification of the refrigerant constitutes an essential sector of the air-conditioning system design. A composition-adjustable dual cooling source (CADCS) chiller has been proposed utilizing the characteristics of inefficient condensation of the non-azeotropic mixture. Separated flows of the working fluid with flexible mass fraction and flow rate respectively treat the waste heat and moisture. Multi-criteria screening mechanism for the working fluid is established involving: i) application field. The critical temperature is better restricted within 300 K to 400 K for application in air-conditioning. ii) environmental impact. The GWP of the candidate cannot exceed 800. iii) cycle architecture adaptability. The boiling point difference preferably exceeds 20 K. iv) liquid separation potential. The obvious temperature glide and substantial separation range allow for the integration of liquid separation technology. Thermodynamic performance optimization indicates that propane/isobutane outperforms all the candidates at a mass fraction of 0.5:0.5 characterized by obvious temperature glide and close to temperature change of the heat transfer medium. The maximum coefficient of performance (COP) is found to be up to 5.2 for the BDCS cycle and 4.42 during separation at vapor quality 0.436 for the CADCS cycle. The exergy loss of the evaporator is reduced by 17.1 %-73.7 % while the exergy efficiency is improved by 3 %-59.7 % due to temperature match refinement in the CADCS cycle. The refrigerant charge in the CADCS cycle can be saved by 5.54 %-15 %. The accumulating waste heat demands a lower vapor quality during separation, while the moisture load barely exerts an effect. Moreover, the effect of the subcooling degree on the cycle performance is analyzed and suggested at 1 °C. The CADCS cycle constitutes a promising prospect of dynamic treatment for thermal and humidity load in the air-conditioning room due to its flexible function and improved heat transfer match.

Ultrasonic intensification of flocculation filtration for kaolinite: Unraveling mechanisms and performance gains

The mining industry produces substantial tailings, which present environmental challenges. This necessitates the adoption of efficient solid–liquid separation technologies to convert these tailings into a dewatered and environmentally manageable dry stack form. This work aims to investigate the transformative potential of ultrasonic treatment in the context of flocculation filtration for kaolinite dewatering and to elucidate the underlying mechanism. Through Uniform Design optimization, we determined the optimal conditions: 40 W ultrasound power, 12 min duration, and 40 kHz frequency. Experimental validation emphasized the effectiveness of these parameters, revealing a 2.02 % reduction in filter cake water content alongside a significant 2.5-fold enhancement in filtration rate. Furthermore, this combined treatment surpassed the performance of flocculation alone, resulting in the formation of smaller, more desirable flocs. The 3D structural analysis of the filter cake using micro-CT revealed that the synergistic application of ultrasound and flocculation led to a notable decrease in overall porosity. More significantly, there was a substantial reduction of isolated pores (down to 9.32 %). This phenomenon remarkably improved pore connectivity, enlarged pore and channel radii, and effectively mitigated capillary resistance during water transport. Additionally, the filter cake subjected to ultrasound and flocculation treatment showcased a uniform distribution of pore space, indicative of a promising trend towards homogenization across different sections. Ultrasound plays a role in refining flocs and suppressing segregation during tailings flocculation and filtration processes, primarily attributed to the cavitation and acoustic streaming effects of ultrasound. This comprehensive investigation sheds light on the transformative role of ultrasonic treatment in advancing the efficiency and performance of kaolinite dewatering processes.

A Review of Gas Capture and Liquid Separation Technologies by CO2 Gas Hydrate

Gas hydrates, being promising energy sources, also have good prospects for application in gas separation and capture technologies (e.g., CO2 sequestration), as well as for seawater desalination. However, the widespread use of these technologies is hindered due to their high cost associated with high power consumption and the low growth rates of gas hydrates. Previous studies do not comprehensively disclose the combined effect of several surfactants. In addition, issues related to the kinetics of CO2 hydrate dissociation in the annealing temperature range remain poorly investigated. The presented review suggests promising ways to improve efficiency of gas capture and liquid separation technologies. Various methods of heat and mass transfer enhancement and the use of surfactants allow the growth rate to be significantly increased and the degree of water transformation into gas hydrate, which gives impetus to further advancement of these technologies. Taking the kinetics of this into account is important for improving the efficiency of gas hydrate storage and transportation technologies, as well as for enhancing models of global climate warming considering the increase in temperatures in the permafrost region.

Optimization of Air Flotation and the Combination of Air Flotation and Membrane Filtration in Microalgae Harvesting

On account of its small size and poor sedimentation performance, microalgae harvesting is restricted from a wider application. Air flotation is an efficient and fast solid–liquid separation technology, which has the potential to overcome the impediments of microalgae harvesting. In this study, factors influencing microalgae harvesting by air flotation were investigated. The results illustrated that bound extracellular organic matter (bEOM) had a greater effect on microalgae harvesting by air flotation, compared with dissolved extracellular organic matter (dEOM). Microalgae harvesting by air flotation in different growth stages proceeded, and the effect of air flotation in the heterotrophic stage was better than the autotrophic stage. The molecular weight distributions demonstrated that after air flotation, the proportion of high MW substance increased, while the proportion of low MW substance decreased, regardless of whether dEOM or bEOM. Membrane filtration was carried out for the algal solutions before and after air flotation. The membrane of pre-flotation algal solution had a higher critical flux of 51 L/m2·h than that of no-pre-flotation (24 L/m2·h), and, thus, pre-flotation had an active effect on membrane filtration in microalgae harvesting. Moreover, the combination of air flotation and membrane filtration provided an efficient technology for microalgae harvesting.

Potentials of implementing liquid-separation to a transient wrap-around microchannel condenser coil within heat pump water heater

Dynamic characteristics of wrap-around microchannel condenser coil are essential to heat pump water heater (HPWH) during heating-up transient. In this paper, effectiveness of applying liquid-separation technology to the wrap-around microchannel condenser coil is discovered. A mathematical model adopting “quasi-steady-state” and “segment-tube-path” approaches is established for the water tank and microchannel condenser coil. Its predictions on both liquid-separation microchannel condenser coil (LMC) and conventional microchannel condenser coil (CMC) are in good agreements with experimental data. Results show that simply employing separators in the condenser coil (LMC-I) does not bring improvement. The average heat transfer coefficient of LMC-I is enhanced by 10.34% and 5.75% at the entrances of the second and third paths compared to that of CMC, respectively, whereas it is degraded at the outlets of the second and third paths as well as in the entire fourth path. However, LMC-I achieves a significant pressure drop reduction by 34.48%. Thereafter, LMC-II is screened from 963 candidates of path arrangements, and has better performances in terms of higher heat capacity and shorter heating time than both CMC and LMC-I. Its average proportion of 51.83% of two-phase area to the total area is also superior to both CMC and LMC-I.

Permeation Properties of Ions through Inorganic Silica-Based Membranes.

The development of inorganic membranes has mainly found applicability in liquid separation technologies. However, only a few reports cite the permeation and separation of liquids through inorganic nanofiltration membranes compared with the more popular microfiltration membranes. Herein, we prepared silica membranes using 3,3,3-trifluoropropyltrimethoxysilane (TFPrTMOS) to investigate its liquid permeance performance using four different ion solutions (i.e., NaCl, Na2SO4, MgCl2, and MgSO4). The TFPrTMOS-derived membranes were deposited above a temperature of 175 °C, where the deposition behavior of TFPrTMOS was dependent on the organic functional groups decomposition temperature. The highest membrane rejection was from NaCl at 91.0% when deposited at 200 °C. For anions, the SO42− rejections were the greatest. It was also possible to separate monovalent and divalent anions, as the negatively charged groups on the membrane surfaces retained pore sizes >1.48 nm. Ions were also easily separated by molecular sieving below a pore size of 0.50 nm. For the TFPrTMOS-derived membrane deposited at 175 °C, glucose showed 67% rejection, which was higher than that achieved through the propyltrimethoxysilane membrane. We infer that charge exclusion might be due to the dissociation of hydroxyl groups resulting from decomposition of organic groups. Pore size and organic functional group decomposition were found to be important for ion permeation.

Numerical simulation of droplet coalescence behavior in gas phase under the coupling of electric field and flow field

ABSTRACTThe coalescence behavior of droplets in an electric field belongs to the important research contents of electrohydrodynamics. Based on the phase field method of the Cahn–Hilliard equation, the electric field and the flow field are coupled to establish the numerical model of twin droplet coalescence in a coupled field. The effects of flow rate, electric field strength, droplet diameter, and interfacial tension on the coalescence behavior of droplets during the coalescence process were investigated. The results show that the dynamic behavior of the droplets is divided into coalescence, after coalescence rupture, and no coalescence under the coupling of electric field and flow field. The proper increase of the electric field strength will accelerate the coalescence of the droplets, and the high electric field strength causes the droplets to burst after coalescence. Excessive flow rates make droplets less prone to coalescence. Under the coupling field, the larger the droplet interface tension, the smaller the droplet diameter, the smaller the flow rate, and the shorter the droplet coalescence time. The results provide a theoretical basis for the application of electrostatic coalescence in gas–liquid separation technology.

Performance and techno-economic assessment of several solid–liquid separation technologies for processing dilute-acid pretreated corn stover

Solid–liquid separation of pretreated lignocellulosic biomass slurries is a critical unit operation employed in several different processes for production of fuels and chemicals. An effective separation process achieves good recovery of solute (sugars) and efficient dewatering of the biomass slurry. Dilute acid pretreated corn stover slurries were subjected to pressure and vacuum filtration and basket centrifugation to evaluate the technical and economic merits of these technologies. Experimental performance results were used to perform detailed process simulations and economic analysis using a 2000tonne/day biorefinery model to determine differences between the various filtration methods and their process settings. The filtration processes were able to successfully separate pretreated slurries into liquor and solid fractions with estimated sugar recoveries of at least 95% using a cake washing process. A continuous vacuum belt filter produced the most favorable process economics.

An overview of solid–liquid separation of residues from coal liquefaction processes

AbstractDirect coal liquefaction process typically produces mixed oils (60%) and gases (15%). The remainder is a high‐boiling viscous residue that contains oils, asphaltenes, unreacted coal, mineral matter and potentially valuable liquefaction catalyst. Effective separation of the components of the residue stream is important to the economic and environmental performance of the process. Solid–liquid separation technologies, such as filtration, hydrocyclones, centrifugation, critical solvent deashing and distillation have been reviewed in relation to their use in coal liquefaction processes. Individual operations used have not been completely satisfactory, and a better overall result is obtained when they are used in combination. © 2012 Canadian Society for Chemical Engineering

Characterization of tannery wastewater and biomass in a membrane bioreactor using respirometric analysis

Respirometric techniques and an activated sludge model (ASM) were applied for the characterization of tannery wastewater and biomass in a pilot plant membrane bioreactor (MBR) operating at high sludge age. The traditional respirometric tests and the IWA-ASM1 were modified to take into account the specific operating conditions, the solid–liquid separation technology and the wastewater complexity. As a result the wastewater biodegradable COD was fractionated into four components: readily biodegradable, rapidly hydrolysable, slowly hydrolysable and inorganic (due to the presence of reduced sulphur compounds). The kinetic and stoichiometric parameters of the biomass (heterotrophic and nitrifying) were estimated through the integration of model simulations and respirometric tests results. In particular the ammonium and nitrite-oxidizing biomasses were separately characterized: the growth kinetics of ammonium and nitrite-oxidizing bacteria resulted noticeably lower than the traditional reference values ( μ max,AOB = 0.25 d −1 e μ max,NOB = 0.23 d −1 at 20 °C, respectively). The ASM was finally used to confirm that the results of the wastewater and biomass characterization allow to properly simulate the mixed liquor suspended solids in the MBR pilot plant and the COD concentration in the effluent.

A new insight into membrane fouling mechanism during membrane filtration of bulking and normal sludge suspension

Membrane bioreactor (MBR) is an important solid–liquid separation technology employed widely in the wastewater treatment. However, membrane fouling is the major problem that hinders the practical application of membrane bioreactor (MBR) systems. A major obstacle for the application of MBRs is the rapid decline of the permeation flux as a result of sludge filamentous bulking. In this paper a series of membrane filtration tests were performed to evaluate the fouling behaviors of bulking sludge and normal sludge. In order to specify the fouling mechanism of bulking sludge, the floc morphology of bulking sludge and normal sludge was studied based on fractal theory and image analysis. The sludge characteristics was also evaluated in terms of extracellular polymeric substances (EPS), relative hydrophobicity (RH) and sludge viscosity. The results showed that the bulking sludge resulted in a greater flux decline rate than normal sludge. The bulking sludge could cause a severe cake fouling, which was induced by the fixing action of filamentous bacteria. The results also showed that the sludge flocs had a good fractal characteristic, and the boundary fractal dimension of bulking sludge flocs was much larger than that of normal sludge. The flocs of bulking sludge had more irregular shape than the flocs of normal sludge. The irregular shape of bulking sludge would do great harm to membrane filtration process. The higher EPS concentration, RH and sludge viscosity of bulking sludge would speed up membrane fouling further.

Cake layer morphology in microfiltration of activated sludge wastewater based on fractal analysis

Membrane bioreactor (MBR) is an important solid–liquid separation technology employed widely in the wastewater treatment. However, membrane permeability decline rapidly due to membrane fouling, which limited the application of MBR. In order to obtain understanding of the complex membrane fouling mechanisms, analysis of the effect of the microstructure on the cake permeability is necessary. In this regard, study of the distribution and porosity of the cake is very necessary. The pore distribution is strongly influenced by cake compressibility but information on how to describe this effect is very limited. In this paper, fractal theory was used to gain knowledge of cake microstructure and its correlation to macroscopic cake properties. Scanning electron microscopy (SEM) and image analysis were utilized to estimate pore size and pore size distributions. The two-dimensional fractal dimension was determined. The results show that the cake layer had a good fractal characteristic, and the fractal dimension ( D s) was linearly correlated with porosity ( R 2 = 0.929). The fractal dimension had some relation with cake resistance and cake specific resistance. It indicates that fractal dimension provides an approach for quantification of cake structure and cake permeability.

Pore structure and network analysis of filter cake

Filtration is an important solid–liquid separation technology employed widely in the mineral processing industries. The effectiveness of the filtration operation can be influenced by numerous variables, related to the particulate phase, the slurry rheology and the equipment. Continuous filtration of fine particles involves filter cake formation and removal of surface moisture by drawing air through the pore structure network. In order to gain a better understanding of the complex transport phenomena that occur in the filter cake, analysis of the effect of the three-dimensional pore geometry on the effective transport properties of the filter cake is necessary. In this regard, analysis of the pore connectivity in a packed bed of particles should allow for a detailed description of fluid flow and transport in the filter cake structure. Two interrelated approaches, namely computer simulation and experimental measurement, can be used to gain knowledge of pore microstructure and its correlation to macroscopic cake properties. In this regard, a three-dimensional Monte Carlo method was used in this work to simulate cake structure. As the resolution and the techniques for three-dimensional geometric analysis have advanced in the last decade, experimental measurements are now possible to specify in detail the pore structure in three-dimensional digital space using high-resolution X-ray microtomography. Thus in addition to computer simulation, this paper presents preliminary experimental findings of pore structure in three-dimensional using X-ray microtomographic techniques. These experimental results are contrasted to results from computer simulation.