Wet Solids Research Articles

Characterization of suspended solids in thermo-treated red musts

<p style="text-align: justify;"><strong>Aims</strong>: Thermo-treatment of grapes, followed by pressing and fermentation in liquid phase, is a growing practice in red winemaking to obtain light and fruity wines. Must clarification before fermentation, a key step to get the expected wine profile, is hardly controlled and strongly varies between different musts. To better understand this variability and its potential impact on quality, suspended solids in several red musts were characterized and the performances of different clarification techniques compared.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Results show a large variability in turbidity and total wet suspended solids between different raw and clarified musts, and a lack of correlation between these values. Clarification is always higher for vacuum filtration than for disk-stack or decanter centrifugation, with strong differences between musts for a given process. Despite a large size distribution, most of suspended particles are micronic and sub-micronic. TEM observations and analyses indicate that they are mostly membrane and organelle fragments along with (macro)molecular aggregates formed during juice extraction. Their overall composition differs from that found in white musts.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Particle heterogeneity and size distribution account for the difficulties encountered in red must clarification. Results also raise the question of the relationship between must turbidity and content in compounds likely to affect wine quality. </p><strong>Significance and impact of the study</strong>: This study constitutes a first characterization of suspended solids in thermo-treated red musts. It provides elements to (i) reason their clarification and (ii) identify the technological and qualitative impact of must suspended solids.

Extractability and characteristics of proteins deriving from wheat DDGS

Wheat Distillers’ Dried Grains with Solubles (DDGS) and in-process samples were used for protein extraction. Prolamins were the predominant protein components in the samples. The absence of extractable α- and γ-gliadins in DDGS indicated protein aggregation during the drum drying processing stage. Prolamin extraction was performed using 70% (v/v) ethanol or alkaline–ethanol solution in the presence of reducing agent. DDGS extracts had relatively low protein contents (14–44.9%, w/w), regardless of the condition applied. The wet solids were the most suitable raw material for protein extraction, with recovery yields of ∼55% (w/w) and protein content of ∼58% (w/w) in 70% (v/v) ethanol. Protein extracts from wet solids were significantly rich in glutamic acid and proline. Mass balance calculations demonstrated the high carbohydrate content (∼50%, w/w) of solid residues. Overall, the feasibility of utilising in-process samples of DDGS for protein extraction with commercial potential was demonstrated.

Addition of cellulolytic enzymes and phytase for improving ethanol fermentation performance and oil recovery in corn dry grind process

Application of hydrolytic and other enzymes for improving fermentation performance and oil recovery in corn dry-grind process was optimized. Non-starch polysaccharide enzymes (BluZy-P XL; predominantly xylanase activity) were added at stages prior to fermentation at optimum conditions of 50°C and pH 5.2 and compared with conventional fermentation (30°C, pH 4.0). Enzyme applications resulted in faster ethanol production rates with a slight increase in yield compared to control. The thin stillage yield increased by 0.7–5% w/w wet basis with corresponding increase in solids content with enzyme treatment after liquefaction. The oil partitioned in thin stillage was at 67.7% dry basis after treatment with hydrolytic enzymes during fermentation. Further addition of protease and phytase during simultaneous saccharification and fermentation increased thin stillage oil partitioning to 77.8%. It also influenced other fermentation parameters, e.g., ethanol production rate increased to 1.16g/g dry corn per hour, and thin stillage wet solids increased by 2% w/w. This study indicated that treatments with non-starch hydrolytic enzymes have potential to improve the performance of corn dry-grind process including oil partitioning into thin stillage. The novelty of this research is the addition of protease and phytase enzymes during simultaneous saccharification and fermentation of corn dry-grind process, which further improved ethanol yields and oil partitioning into thin stillage.

Investigation into the use of cement kiln dust in high density sludge (HDS) treatment of acid mine water

The purpose of this study was to investigate the potential to replace lime with cement kiln dust (CKD) in high density sludge (HDS) treatment of acid mine drainage (AMD). The bench-scale study used two water samples: AMD sampled from a lead-zinc mine with high concentrations of iron (Fe), zinc (Zn), and arsenic (As) (Fe/Zn-AMD) and a synthetic AMD solution (Syn-AMD) spiked with ferric sulfate (Fe2(SO4)3). Arsenic was found to be significantly reduced with CKD-HDS treatment of Fe/Zn-AMD compared to lime-HDS treatment, to concentrations below the stringent mine effluent discharge regulation of 0.10 mg As/L (i.e., 0.04 ± 0.02 mg/L). Both CKD- and lime-HDS treatment of the two AMD samples resulted in settled water Fe concentrations above the stringent discharge guideline of 0.3 mg Fe/L. CKD addition in the HDS process also resulted in high settled water turbidity, above typical discharge guidelines of 15 mg TSS/L. CKD-HDS treatment was found to result in significantly improved settled solids (i.e., sludge) quality compared to that generated in the lime-HDS process. HDS treatment with CKD resulted in 25–88% lower sludge volume indices, 2 to 9 times higher % wet solids, and 10 to 20 times higher % dry solids compared to lime addition. XRD and XPS testing indicated that CKD-HDS sludge consisted of mainly CaCO3 and SiO2 with Fe3+ precipitates attached at particle surfaces. XRD and XPS testing of the lime-HDS generated sludge showed that it consisted of non-crystalline Fe oxides typical of sludge formed from precipitates with a high water concentration. Increased sedimentation rates were also found for CKD (1.3 cm/s) compared to lime (0.3 cm/s). The increased solids loading with CKD addition compared to lime addition in the HDS process was suggested to both promote surface complexation of metal precipitates with insoluble CKD particles and increase compression effects during Type IV sedimentation. These mechanisms collectively contributed to the reduced water content of CKD-HDS sludge. The results of this study suggest that solids loading is a significant factor in increased sludge density found with the HDS process compared to conventional lime precipitation-sedimentation.

Effects of rheological properties on reactivity of energetic thin films

Magnesium (Mg) and manganese dioxide (MnO2) powders were mixed with polyvinylidene fluoride (PVDF) binder and n-methyl pyrrolidone (NMP) solvent and blade cast onto stainless steel foil. The rheological properties of these mixtures were investigated to quantify the mixing condition. Parameters including wet film thickness, equivalence ratio and solids loading were varied. Flame speed and calorific output were investigated for each of these parameters. Results show energy propagation rates increased as a function of dry film thickness, although calorific output remained relatively constant. Stoichiometrically fuel rich compositions were self-quenching, demonstrating the necessity of available oxygen for reaction propagation. A 0.45 solids–liquid mixing ratio resulted in up to an order of magnitude higher energy propagation rate for both open and confined configurations. Rheometry measurements and physical characterizations of the films reveal that the solids loadings resulting in the most stable suspensions also produced the highest energy propagation. Changing solids loading affects the density of the film, which in turn affects energy propagation. Capillary drying forces at high liquid loadings result in higher porosity leading to reduced deposition density and thickness. Very high solids loading results in films with dilatant properties and poor mixing. These results show solids loading affects mixing and energy propagation and could impact slurry cast energetic materials as in additive manufacturing processes.

Bench-scale comparison of conventional and high rate clarification treatment processes for acid mine drainage

Acid mine drainage (AMD) is characterized as having low pH and high concentrations of sulfate and dissolved metals. This study compared treated water quality and sludge properties of three process technologies for AMD: conventional sedimentation, high density sludge (HDS), and ballasted flocculation. All three processes were found to be capable of removing regulated metals to concentrations below current Canadian discharge guidelines. However, ballasted flocculation was the only technology found to be able to meet the more stringent federal guidelines proposed for future implementation under the Fisheries' Act's Metal Mining Effluent Regulations. Specifically, arsenic and zinc concentrations in AMD treated by the conventional and HDS processes were above proposed future guidelines of 0.10 and 0.25 mg/L, respectively, while lead, copper, and nickel all met respective guidelines. Concentrations of all regulated contaminants were below proposed guidelines when treated by ballasted flocculation. The HDS process was found to produce a significantly more concentrated sludge than conventional sedimentation (i.e., higher solids content (19 ± 1% versus 7 ± 4% wet solids) and lower sludge volume index (SVI; 8.4 ± 0.8 versus 230 ± 20 mL/g)).

Performance assessment of centrifuge dewatering unit using multivariate statistical approach: a case study of a centralized sludge treatment facility (CSTF) in Malacca, Malaysia

The performance of the centrifuge dewatering unit in Sungai Udang centralized sludge treatment facility has been studied using multivariate statistical approach. The relationships between bio-solids production and 14 parameters were analyzed using principle component analysis (PCA) and multiple linear regression (MLR) analysis. PCA was used to simplify the complexity among variables affecting the production of bio-solids in the treatment facility. All varimax factor (VF) values obtained from the PCA were used as independent variables in MLR analysis. It was found that VF1 (wet sludge and mixed liquor suspended solids) and VF4 (polymer dosage) had significant linear relationships with bio-solids production, which accounted for 74.32% of variations in the bio-solids production. This approach could be used to precisely estimate the amount of sludge produced by the centrifuge dewatering unit and for better evaluation of system performance that meets the design criteria and future requirements for sludge disposal.

Simulation and validation of a model for a batch wall heated fluidized bed dryer

Drying of wet particulate solids is carried out in a novel way in a wall heated fluidized bed dryer. The experimental data shows that drying occurs effectively. The temperature variation with respect to time reveals that there is evaporative cooling occurring in the solids. Initially, there is lowering of temperature, then an increase is noticed and finally it reaches steady state. This phenomenon of wall heated drying is modelled first by percolation model by taking radial average of temperature of air, temperature of solids and moisture content of solids but accounting for axial variation along the height of the cylindrical fluidized bed. The drying rate is considered to depend on the local temperature of the solids in the fluidized bed. This procedure produced three coupled partial differential equations: one for temperature of air, second for temperature of solids and third for moisture content of solids. The axial convective heat transport equation and drying rate equation are solved using an explicit Euler numerical method. Well-mixed (CSTR) model and CSTRs-in-series model are also presented to account for recirculations in the bubbling regime of fluidization. The simulation results of CSTRs-in-series model show a good agreement with experimental data for temperature and moisture variation. Especially, the evaporative cooling phenomenon is captured successfully through simulation.

Bio-oil via catalytic liquefaction of unhydrolyzed solids in aqueous medium

Bioethanol can be produced from lignocellulosic feedstock using a biochemical route involving enzymatic hydrolysis followed by microbial fermentation. During these processes, about 30 to 40% of the biomass is left behind as wet unhydrolyzed solids (UHS), depending on the type of biomass, enzyme loading, and duration of enzymatic hydrolysis. The UHS is mostly composed of lignin, bound enzymes, undigested recalcitrant carbohydrates and ash. The efficient conversion of UHS into bio-oil will increase the overall conversion efficiency of biomass to liquid fuels (bioethanol and bio-oil) and has the potential to reduce the cost of biofuel production from lignocellulosic biomass. In this paper we report the results of bio-oils production from UHS via hydrothermal liquefaction (HTL) under varying temperatures (280–350°C) and subcritical water conditions. The effects of K2CO3 and supported bimetallic CoMo/Al2O3 catalysts during HTL process were investigated. The UHS used in this study was produced after enzymatic hydrolysis of Ammonia Fiber Expansion (AFEX) pretreated corn stover (ACS). Bio-oil yields at different HTL temperatures were quantified and characterized using 1H-NMR, 13C-NMR, GC-MS, and elemental analysis. The yield of bio-oil was higher in the presence of 5 wt% of K2CO3 during HTL in comparison with CoMo/Al2O3 catalyst. The highest degree of liquefaction (DL) and bio-oil yield were respectively 43.4% and 30.1 wt% at 350°C in the presence of K2CO3 while the highest ECR was 57.1% at 320°C in the presence of K2CO3. The study is one of the first of its kind where unhydrolyzed solids, left behind after bioethanol production, were used for making bio-oils with traditional and reduced bimetallic CoMo/Al2O3 catalysts in an aqueous medium. The results of the study can contribute to the development of the lignocellulosic biomass-based biorefinery concept.

Biomass properties and permeability in an immersed hollow fibre membrane bioreactor at high sludge concentrations.

This study aimed to investigate the influence of biomass properties and high mixed liquor suspended solids (MLSS) concentrations on membrane permeability in a pilot-scale hollow fibre membrane bioreactor treating domestic wastewater. Auxiliary molasses solution was added to maintain system operation at constant food-to-microorganisms ratio (F/M = 0.13). Various physicochemical and biological biomass parameters were measured throughout the trial, comprising pre-thickening, thickening and post-thickening periods with reference to the sludge concentration and with aerobic biotreatment continuing throughout. Correlations between dynamic changes in biomass characteristics and membrane permeability decline as well as permeability recovery were further assessed by statistical analyses. Results showed the MLSS concentration to exert the greatest influence on sustainable membrane permeability, with a weaker correlation with particle size distribution. The strong dependence of absolute recovered permeability on wet accumulated solids (WACS) concentration, or clogging propensity, revealed clogging to deleteriously affect membrane permeability decline and recovery (from mechanical declogging and chemical cleaning), with WACS levels increasing with increasing MLSS. Evidence from the study indicated clogging may permanently reduce membrane permeability post declogging and chemical cleaning, corroborating previously reported findings.

Characterization of moisture distribution in a fluidized bed

The determination of moisture distribution in a sample of wet solids is important as it can provide information on how well a liquid reagent has been sprayed in a fluidized bed reactor. The moisture is divided into three groups: (i) free moisture, or water coating individual particles; (ii) micro-agglomerates, which are fluidized; and (iii) macro-agglomerates, which are too large to remain fluidized and, consequently, settle to the bottom of the bed. This study evaluates various methods for the determination of the moisture distribution in a sample of wet solids, such as funnel flow, angle of repose, compressibility index, avalanche tests and electrical conductance. In addition, a different method is implemented to obtain directly the moisture distribution from the bed fluidization quality, based on image processing and on the variation with time of the conductance of the de-fluidized bed after a liquid injection.A solids sample was taken from the fluidized bed. Its free moisture was estimated through the abovementioned tests and its overall moisture was used to obtain the fraction of water trapped in micro-agglomerates. The amount of water in the macro-agglomerates was then obtained by subtracting the measured free and micro-agglomerates moistures from the total mass of liquid injected into the bed.

A novel exergy recuperative drying module and its application for energy-saving drying with superheated steam

A novel exergy recuperative drying module with superheated steam as the drying medium was developed. The process is based on self-heat recuperation technology which can recirculate both the sensible and latent heats without heat addition. This drying module was applied as an exergy recuperative process for the drying of wet solids. The energy consumption for the exergy recuperative drying system could be reduced to 1/7–1/12 that required for a conventional heat-recovery drying system in the case of drying wet solids from 65 to 10wt% (wet basis, wb) of water content. The effects of adiabatic efficiency of the compressor and the final water content of the dried samples on the energy consumption of the proposed drying system were calculated by the process simulator PRO/II.

CH4 and total GHGs emission from urban landfills in southwest Iran

High population growth and immigration rate from rural areas to urban centers have led to increased waste production and numerous urban landfill sites in different parts of Iran during the past three decades. The present study was carried out in southwest Iran where the aforementioned factors have occurred at an extremely high rate. There are four cities in this part of the country with a population of about 2.250 million and three landfill centers are located near these cities. The main aim of the present study was to estimate the CH4 and total GHGs emission rate from the mentioned sites. So, the components of urban solid wastes and the share of wet waste were determined in the areas of study. The results revealed that the share of wet solids was between 65 and 73%. Also, methane and total GHGs emission in landfill sites were estimated at about 2244.7 tons/year and 8405 tons/year during 2010, respectively. Moreover, the amounts of CH4 and total GHGs emission for the next 75 years, respectively, are estimated to be about 1.98 × 106 tons and 5.2 × 106 tons for the aforementioned three landfill centers. The high volume of the produced biogas shows that by correctly designing the gas pipeline, the application of the produced gas will be very beneficial with regard to environment and economic approaches.

Effect of temperature and air flow rate on carbon and nitrogen compounds changes during the biodrying of swine manure in order to produce combustible biomasses

AbstractBACKGROUND: Manure is the main waste of raising livestock, when spreading in soils can cause surface and ground water pollution. The management of manure is associated with emissions of greenhouse gases and odours. Dry manure contains at least 45% of carbon. This is an attractive characteristic for energetic valorisation. To use manure in the production of energy, it must be previously dried.RESULTS: Wet solids from swine manure containing 30% of dry matter were dried in laboratory scale biodryers. Four levels of aeration rate from 0.4 to 4 L min−1 kg$^{-1}_{\rm {DM}}$ and five levels of temperature from 25 to 65 °C were tested. The highest emissions of CO2, NH3 and N2O occurred at the highest air flow rate of 4 L min−1 kg$^{-1}_{\rm {DM}}$. For all operating conditions, the high calorific power had a mean value of 15 ± 0.4 MJ kg$^{-1}_{\rm {DM}}$. The dried biomass obtained had an energetic potential to valorise by combustion.CONCLUSION: The bed temperature and aeration rate have an effect on carbon and nitrogen bio‐cycles. These operating parameters can also control the release quantity and gaseous form of nitrogen. Several problems related to swine manure management can be solved by using biodrying, an economic and environmental friendly technology. Copyright © 2012 Society of Chemical Industry

Biodiesel Production from Wet Algal Biomass through in Situ Lipid Hydrolysis and Supercritical Transesterification

In an effort to process wet algal biomass directly, eliminate organic solvent use during lipid extraction, and recover nutrients (e.g., N, P, and glycerol) for reuse, we developed a catalyst-free, two-step technique for algal biodiesel production. In the first step, wet algal biomass (ca. 80% moisture) reacts in subcritical water to hydrolyze intracellular lipids, conglomerate cells into an easily filterable solid that retains the lipids, and produce a sterile, nutrient-rich aqueous phase. In the second step, the wet fatty acid-rich solids undergo supercritical in situ transesterification (SC-IST/E) with ethanol to produce biodiesel in the form of fatty acid ethyl esters (FAEEs). Chlorella vulgaris grown sequentially under photo- and heterotrophic conditions served as the lipid-rich feedstock (53.3% lipids as FAEE). The feedstock and process solids were characterized for lipid components using highly automated microscale extraction and derivatization procedures and high-temperature gas chromatography. Hydrolysis was examined at 250 °C for 15 to 60 min; solids recovered by filtering contained 77−90% of the lipid originally present in the algal biomass, mainly in the form of fatty acids. The effects of reaction time (60 or 120 min), temperature (275 or 325 °C), and ethanol loading (approximately 2−8 w/w EtOH/solids) were examined on the yield and composition of biodiesel produced from the SC-IST/E of the hydrolysis solids. Longer time, higher temperature, and greater ethanol loading tended to increase crude biodiesel and FAEE yields, which ranged from about 56−100% and 34−66%, respectively, on the basis of lipid in the hydrolysis solids. Isomerization and decomposition of unsaturated FAEEs was quantified, and its effect on fuel yield is discussed.

Simulation and Optimization of Drying of Wood Chips With Superheated Steam in a Rotary Kiln

The present work reports a computer simulation and optimization study of heat transfer in a rotary kiln used for drying and preheating wood chips with superheated steam at 1 bar. A rotary kiln employed for drying and preheating wet solids consists of a refractory lined cylindrical shell mounted at a slight incline from the horizontal plane. The kiln is slowly rotated about its longitudinal axis. Wet solids are fed into the upper end of the cylinder, and during the process, they are dried and heated by the counter-current flow of the hot gas. Finally, it is transferred to the lower end, where it reaches the desired temperature and is discharged. The heat transfer model includes radiation exchange among hot gas, refractory wall and the solid surface, transient conduction in the refractory wall, and mass and energy balances of the hot gas and solids. A finite-difference based computational heat transfer approach is used. A univariate search method has been used to obtain the minimum kiln length with respect to various kiln operating parameters subject to a constraint on the inlet gas temperature. The parametric study lent a good insight into the physics of the drying process in a rotary kiln. The optimization study reveals that for the same predicted kiln length, lower inlet steam temperature can be used, which will result in saving of energy cost.

Liquid Feed Injection in a High‐Density Riser

AbstractInitial investigations on liquid feed injection in a high density circulating fluidized bed of fluid catalysed cracking (FCC) particles were performed by means of fast responding thermocouples and capacitance probes. The results imply very limited radial mixing between dry solids, wet solids, and liquids for injection parallel to the hot up‐streaming gas‐solid flow.

Rag Layers in Oil Sand Froths

During the settling stages in some oil sands froth treatments, a rag layer (an undesirable mixture of dispersed oil, water, and solids) can form at the water−oil interface. To investigate rag layer formation, oil sand froths were diluted with mixtures of toluene and heptane and the diluted froths were centrifuged in steps of increasing rpm. The volumes of oil phase, rag layer, free water, and sediment were measured after each step. The data obtained from the experiments were used for material balances to determine the composition of the rag layers. The size and properties of the rag layer solids were also measured. Two mechanisms were found to influence rag layer formation: slow coalescence of emulsified water between 1500 and 3000 rpm (200−1000 times gravity); trapping of fine intermediate to oil wet solids at higher rpm and residence times. The main process factors affecting rag formation appear to be the type of diluent and asphaltene precipitation. As well, higher quality oil sand produced much smaller rag layers.

Numerical study of the thermal ablation of wet solids by ultrashort laser pulses

The ablation by ultrashort laser pulses at relatively low fluences (i.e., in the thermal regime) of solids wetted by a thin liquid film is studied using a generic numerical model. In comparison with dry targets, the liquid is found to significantly affect ablation by confining the solid and slowing down the expansion of the laser-heated material. These factors affect the relative efficiency of the various ablation mechanisms, leading, in particular, to the complete inhibition of phase explosion at lower fluences, a reduced ablation yield, and significant changes in the composition of the plume. As a consequence, at fluences above the ablation threshold, the size of the ejected nanoclusters is lower in presence of the liquid. Our results provide a qualitative understanding of the effect of wetting layers on the ablation process.

Phase Diagram for the Na2O—Al2O3—H2O System at 130 °C.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.