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Although cellulose nanomaterials have promising properties and performance in a wide application space, one hinderance to their wide scale industrial application has been associated with their economics of dewatering and drying and the ability to redisperse them back into suspension without introducing agglomerates or lose of yield. The present work investigates the dewatering of aqueous suspensions of cellulose nanofibrils (CNF) using ultrasound as a potentially low-cost, non-thermal, and scalable alternative to traditional heat-based drying methods such as spray drying. Specifically, we use vibrating mesh transducers to develop a direct-contact mode ultrasonic dewatering platform to remove water from CNF suspensions in a continuous manner. We demonstrate that the degree of dewatering is modulated by the number of transducers, their spatial configuration, and the flow rate of the CNF suspension. Water removal of up to 72 wt.% is achieved, corresponding to a final CNF concentration of 11 wt.% in 30 minutes using a twotransducer configuration. To evaluate the redispersibility of the dewatered CNF material, we use a microscopic analysis to quantify the morphology of the redispersed CNF suspension. By developing a custom software pipeline to automate image analysis, we compare the histograms of the dimensions (length, width) of the redispersed dewatered fibrils with the original CNF samples and observe no significant difference, suggesting that no agglomeration is induced due to ultrasonic dewatering. We estimate that this ultrasound dewatering technique is also energyefficient, consuming up to 36% less energy than the enthalpy of evaporation per kilogram of water. Together with the inexpensive cost of transducers (

This chapter describes the treatment of fine coal tailings from a coal preparation facility, starting from the acceptance of tailings, or fine raw coal, into a plant thickener, which concentrates the tailings as a slurry, and produces clarified water for recirculation to the process plant. The methods of disposal of the thickened slurry tailings are discussed, from the types of filtration technologies available, to new methods, including deep cone paste thickening. All these dewatering processes are designed to recirculate the maximum amount of water to the plant and offer alternatives for the tailings solids disposal to the older solution of pumping to tailings pond, or dam.

Beneficiation of coal is a water intensive process, and the water is recovered in downstream operations in the high rate thickener (HRT) and vacuum belt filtration (VBF). Clean coal particles entering the HRT have an inherent tendency to enter the overflow because they are extremely fine and hydrophobic. Hence, flocculants (polymers) are used to floc the ultrafine particles so that they settle and enter the underflow. Ultrafine coal particles (−37 μ), which are highly hydrophobic, if present in the stream, will not be efficiently captured by using flocculants alone. This is observed in the normal plant operation at one of the beneficiation plants in the Jharia region, Jharkhand, India. Approximately 6–7% of the feed to the HRT enters the over flow (supernatant water). Hence, this amount of clean coal particles is not recovered and account for production losses. A comprehensive settling and dewatering test work was conducted with clean coal slurry using several commercially available reagents. Studies were also done on different combinations of reagents, including coagulants and surfactants along with flocculants, to improve the settling behavior of the coal particles. The reagents were assessed based on their performance with respect to settling rates, overflow water clarity, and compaction of the underflow solids. Emphasis was given to the ability of the reagents in compacting thickener underflow to higher densities so that maximum water could be recovered from the thickener. Pretreatment of highly hydrophobic coal slurry with a combination of coagulant and surfactant followed by flocculation showed very good settling characteristics with clear overflow.

Dewatering is considered as extremely significant and primary step to enhance the quality of lignite. A great number of research focus on conventional fluidized-bed drying technology or dynamics. I...

Hydraulic fracturing is the main stimulation technique that enables the economic production of coalbed methane reservoirs. However, massive invasion and retention of coal fines in proppant packs can clog the pore spaces and lead to an impairment of fracture conductivity. In this study, the effects of proppant wettability and size on retention of coal fines in proppant packs during the dewatering stage were investigated, for their optimization to achieve a long-term and effective control of fines retention. First, a series of transport and retention experiments of coal fines were performed on saturated proppant packs with different proppant sizes and wettabilities. Herein, standard quartz sand was used as the proppant carrier, and its surface wettability was modified to either hydrophobicity or stronger hydrophilicity by treatment with fluorocarbon resin and piranha solution, respectively. The experimental results indicated that both the retained amount and the deposition rate coefficient of coal fines decreased with increasing proppant hydrophilicity (or decreasing proppant hydrophobicity) and size. For the proppants treated with piranha solution, almost no coal fines were retained in proppant packs. Second, the forces/torques acting on coal fines in the vicinity of proppants were analyzed to elucidate the underlying mechanisms responsible for the influence of proppant wettability and size on fines retention. The effective filter surface (EFS) parameter was estimated by analyzing forces/torques to evaluate the filtration performance of proppant packs. Theoretical results illustrated that the EFS value decreased with increasing proppant hydrophilicity and size. The EFS value for proppants treated with piranha solution was near zero, which was due to the chemically "unfavorable"retention condition induced by piranha solution treatment. The EFS exhibited a similar tendency to the retention of coal fines observed in experiments, which validated the model. Finally, the recommendations on fines retention control in proppant packs were provided.

Flotation is the common method for fine low rank coal upgrading while it is always inefficient due to the rough surface morphology and rich oxygen-containing functional groups. Hydrothermal pretreatment is widely used in dewatering for low rank coal. The physicochemical properties of coal surface considerably vary following the hydrothermal pretreatment. In this study, hydrothermal pretreatments at different temperatures for different times were applied to enhance lignite flotation. The hydrothermal pretreatment at 200 °C can significantly improve the flotation efficiency, while the temperature raised to 300 °C, the flotation recovery did not increase or even decrease. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Zeta potential, Brunauer–Emmett–Teller, and particle size distribution analysis were conducted to explain the underlying mechanism. The contents of pore and crack on coal surface considerably decreased and more fresh and smooth surfaces exposed following hydrothermal pretreatment, according to SEM analysis. The FTIR spectroscopy and XPS showed that the contents of oxygen-containing functional groups were decreased, while the hydrophobicity of lignite was increased following pretreatment. The decrease of Zeta potential also indicated the decrease of oxygen-containing functional groups and increase of hydrophobicity on coal surface. However, excessive temperature of hydrothermal pretreatment could increase the pore diameter and fine particle fraction, leading to a higher collector consumption and lower bubble–particle collision efficiency. Consequently, the flotation recovery was not improved or even decreased at the hydrothermal pretreatment temperature of 300 °C.

Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines, but negative effects may occur as the fracturing fluids are absorbed into the coal seam. Gas wettability alteration (GWA) technology can be used as it can enhance the gas and water mobility during dewatering process as a result of capillary pressure change. However, there have been few reported field tests in coal mines using GWA technology. This paper describes a pilot-scale field test in Xinjing coal mine, Yangquan, China. The fluorocarbon surfactants perfluorooctyl methacrylate monomer-containing polymethacrylate (PMP) was used to alter the wettability of coal seam to strong gas-wetness during the hydraulic fracturing process. The study focuses on the comparison of two boreholes (Boreholes #9 and #10) and one other borehole (Borehole #8) with and without using GWA approach. A well-defined monitoring program was established by measuring the dewatering volume of the fracturing fluid and the drainage volume of methane as well as the concentration. The field test results showed that the average methane drainage rates of Boreholes #9 (39.28 m3/d) and #10 (51.04 m3/d) with GWA treatment exceeded that of Borehole #8 (21.09 m3/d) without GWA treatment, with an increase of 86.3% and 142.1%, respectively. The average methane concentrations of Boreholes #9 (4.05%) and #10 (6.18%) were 64.6% and 151.2% higher than that of Borehole #8 (2.46%), respectively. On the other hand, the dewatering ratio of Boreholes #9 (4.36%) and #10 (3.11%) was almost 19 times and 13 times greater than that of Borehole #8 (0.22%). These field test results were in agreement with the experimental data. The significant increase in both methane concentration and dewatering ratio demonstrated that GWA technology could be applied for enhanced methane drainage in coal mines. Important lessons learned at Xinjing coal mine might be applied to other coal mines in China and elsewhere.

In mineral processing, dewatering and drying are critical aspects from the technical and economical viewpoints. These operations should be considered carefully to achieve optimal water/moisture rem...

Electrohydrodynamic (EHD) drying is a novel nonthermal technique using cold plasma in high electric field for dewatering of heat-sensitive foods. It is highly acclaimed for energy efficiency, envir...

The filtration and dewatering of fine clean coal not only ensure industrial water recycle in coal washing plant, but also reduce the moisture of coal product in order to meet the requirements of combustion or coking industry. Fine clean coal is mainly composed by organic matter, and the property difference of different organic matter determines the filtration and dewatering behavior. In this investigation, vitrinite and inertinite were separated from a clean bituminous coal, and the comparative filtration and dewatering behavior of vitrinite and inertinite were conducted. The results showed that inertinite has lower dewatering rate and higher filter cake moisture than vitrinite. The analysis of filter cake structure showed that inertinite particle is easier to be broken into small particles due to the difference of mechanical properties, thus forming more compact filter cake than vitrinite. The analysis of particle surface properties showed that vitrinite is more hydrophobic than inertinite, which makes water easier drained from filter cake. The simulation study showed that the structure of inertinite is more porous than that of vitrinite, and the interaction between inertinite and water is stronger than that between vitrinite and water. This study provides a theoretical basis for improving coal dewatering by selectively improving coal maceral hydrophobicity.

This article describes a method of dewatering press felts using a blow-through device. The essence of this method is pressing out free water contained in the felt with unheated air at a slight overpressure. The usefulness of this method for various types of felt used in tissue machines was tested. The results showed that the effectiveness of this process depends mainly on the proper selection of the pressure difference on both sides of the dewatering felt and of the blow-through time (dwell time). The increase in the dryness of felts dewatered by means of the air blow-through method is closely related to the structure and contamination of the felt. In the second part of the study, the felts were additionally dewatered using a suction chamber with a vacuum of 20 kPa. Unfortunately, the increase in the dryness of the felts by means of a vacuum was not very high, only up to 2.8%.

Well log analysis and production testing in coal are the initial requirements to judge the prospectivity of a coalbed methane (CBM) reservoir. The process of prospect identification through laboratory studies is accurate although it is time-consuming and expensive. Therefore, we developed a methodology to identify prospective coal seam by establishing multiple regression models of geophysical well log parameters vs. organic/inorganic contents from laboratory-tested core samples for one seam. The Langmuir’s equation and methane adsorption isotherm were used to estimation of gas and saturation content by developing a regression model from organic content. Gas and coal contents (ash, moisture, fixed carbon, and volatile matter) were obtained from the subsequent propagation of the established equations to other wells. Gas saturation increased with depth from 60 to 69%. Mapped seam thickness and gas content were in the ranges of 10.0–54.0 m and 6.1–28.2 cc/g, respectively. Overlaying of seam thickness and gas content identified the sweet spots in releasing potential future well locations. Errors within the permissible limit between the predicted and observed values indicate the gas estimation to be reliable. Another application for electro-facies classification was demonstrated by applying multi-resolution graph-based clustering architecture to capture texture parameters from histogram and auto-covariance function in resistivity image log. Determination of lithology by correlation of resistivity image and geophysical well log corroborated with the depositional environment having fining upward formational sequence. Thus, this study helps in estimating proximate components, gas content, and saturation with depth in coal seam for production optimization to better understand its implications on the dewatering and gas production periods in the Bokaro CBM reservoir situated in India.

Investigation and uptake of filtered tailings continues to grow throughout the globe. This is driven by a wide range of site-specific considerations, which include such factors as tailings characteristics (e.g., amenability to filtration), production rates, climate, water availability, cost drivers, environmental requirements, and social factors. Despite the aforementioned technological growth, the currently available filtration technology is not able to meet the needs of many operations and projects that would otherwise adopt the technology. Experience with large-scale industrial filtration shows that vacuum belt filter systems meet the needs of many modern users, exceptions being the inability to effectively dewater tailings at altitude and/or with a fine particle size distribution: a potential fatal flaw. This paper presents a case study on the utilization of the patented Viper Filtration technology on gold tailings to overcome this challenge and shares the resultant full-scale plant design, highlighting the features designed to overcome cost and scalability deterrents. This technology is a novel mechanical process which complements the vacuum pressure in dewatering the filter cake as it travels along the belt filter. This project commenced with a pilot testing program, which successfully met the objective to rigorously test, measure and record any performance improvements achieved when engaging the Viper technology. Of the two tailings products tested, gross improvements of 4.2%w/w and 5.7%w/w were achieved when compared to the conventional vacuum belt filter operation. This pilot testing facilitated measurement of operating and design data, which forms the basis of the full-scale system design and resultant equipment supply of three vibration roller assemblies for retro-fitting on the existing vacuum belt filter.

The surface of low-rank coal has many oxygen functionalities, which leads to poor coal slime dehydration. To improve the effect of coal slime dewatering, sodium dodecyl benzene sulfonate (SDBS) was...

We analyzed the regional nature of China’s coal mine water disasters based on three aspects: the main water source, water-conducting passages, and threat level of water hazards. The development of water hazard control technology in China’s coal mines, including exploration and assessment of hydrogeological conditions, water inrush mechanisms, and predictive technology were all reviewed. We then focused our discussion on the calculation theory and methods behind mine inflow prediction, methods of dewatering and depressurizing, and technology for mining under water pressure and water-blocking grouting. Finally, we present the evolving trend of coal mine water disaster prevention and control technology, which is characterized by accuracy, transparency, environmental considerations, informatization, and intelligent technology.

Lignite is difficult to obtain highly efficient indexes by conventional flotation due to its poor surface hydrophobicity. Although the modification of flotation reagents has made some progress in improving the flotation performance, they all remain at the stage in the laboratory. Here, we proposed to improve the flotation performance by hydrothermal treatment dewatering (HTD) for lignite. Combined with the 13C NMR and FT-IR analysis, the impact of the HTD process on lignite’s chemical structural evolution and flotation performance was investigated. The results showed that the HTD process is an effective means for dehydration and deoxygenation to increase lignite quality and the metamorphic degree of coal. The content of oxygen-containing functional groups generally decreases during the HTD process, especially carboxyl acid and ether groups. Therefore, surface properties and wettability of HTD coal samples were changed, and the contact angle gradually increases with the HTD temperature increased, which enhance the hydrophobicity and decrease hydrophilia of the lignite surface. The HTD process effectively improves the flotation performance of lignite during the conventional flotation operation condition, even if the coal pulp after HTD was directly used as a flotation feedstock. Specifically, the coal oil and capryl alcohol were used as collector and forming agents, respectively, and the pulp concentration was adjusted to 60 g/L. The yield of the cleaned coal increased from 12.14% of the raw coal to 55.58% of HTD310, and combustible matter recovery increased from 13.83% of the raw coal to 65.17% of HTD310 by raw coal basis.

To neutralize the waste pickling solutions and rinsing water, resulting from cleaning metal products s surface of rust by acids solutions, lime is used. Being cheap, this method of sewage neutralization has considerable drawbacks. Forming in the technological pipes strong gypsum depositions and low specific productivity of the equipment for sediment dewatering are most significant of them. Characteristic of aggressive industrial sewage, formed at pickling of ferrous metals presented. Methods of elimination of drawbacks of industrial sewage neutralization by lime considered, including stabilization of neutralized industrial sewage and control of properties of the sediment formed. It was noted, that stability of the circulating water can be provided by accelerating of crystallization of the forming gypsum sediments by introducing in it fine priming powder and heating the neutralized water up to 65-70 °С followed by thermal softening of a part of circulating water, removed out of the circulating system. It was shown, that the heating of the water and the ongoing changes of the composition and properties of the sediment result in decrease of filtration resistance 2-3 folds, increase of deposition speed 3-4 folds and decrease the sediment volume 1.5-2 folds comparing with lime neutralization in cold water. Calculated dozes of lime at the heating were taken the same as at the regular lime neutralization. Elimination of the circulating water oversaturation by bi-water gypsum can be reached also by addition into the water of powder-like gypsum pulp - priming powder for microcrystals of the gypsum, followed by aeration during 30-40 min. This method was tested under industrial conditions. Technological properties of the forming sediment can be improved by sediment treatment by flocculants and preliminary heating of the neutralized water up to 65-70 °С. Control of technological properties of the sediment is done by addition of flocculants and heating of the neutralized water. Recommendations for improving operation of the neutralization facilities presented with indicating particular technological parameters of the equipment operation for sewage and sediment treatment.

Brewers’ spent grains (BSGs) represent the largest quantity of solid waste from brewing, while xylooligosaccharides (XOS) produced from BSG show promising applications in food, beverage and health products. Production of XOS from a Weiss and malt BSG was scaled-up in steam explosion hydrothermal treatment using process conditions from bench-scale liquid hot water optimisations in stirred batch reactors. Three levels of moisture (15, 25 and 32% dry matter) achieved by screw press dewatering were evaluated by varying the treatment temperatures and times. Results show the highest XOS yields (> 73.1%) were obtained, for both BSGs, at process condition selected (180 °C, 10 min) with 25% initial dry matter content. These yields were higher than reported bench-scale optimisations (61%), but obtained using 60% less water; hence, initial dry matter content was an important variable affecting XOS yield. The pilot-scale steam explosion results provide a departing point for a cost-effective commercial production of XOS from BSG.

The properties of sewage sludge-derived biochar (BC) pyrolyzed at 300–900 °C were characterized, and which exhibited the basic properties of coagulant. When 1 g BC500 was added to 100 mL waste-activated sludge (WAS), the maximum mean settlement rate reached 8.20 mL min−1 within 10 min, and the volume of the settlement with settling time decreased to 13 mL. The capillary suction time of BC500 (12 s) was superior to those of municipal solid waste incineration (MSWI) fly ash (13.40 s), coal fly ash (14.20 s), and activated carbon (12.20 s). In addition, added BC may reduce the moisture content of sludge cake, especially for BC500. It can be that soluble cations and organic functional groups neutralize the negative charge of WAS which is helpful to shorten settling time. Meanwhile, the pore structure is beneficial for reducing moisture content of sludge cake. As results shown, BC was feasible to improve sewage sludge dewatering used as a coagulant.

The article highlights one of the important problems in oil refining, the compatibility of components in the formation of feedstock blends and marketable petroleum products. The principles of determining and controlling the kinetic stability of oil blends to phase separation are set out. Examples of incompatibility of components (crude oils, components of light and dark products, fuel additives) are presented. At the same time, it has been noted that phase separation is the target process in some cases, such as dewatering of crude oil and oil products, lube oil production, etc.

In this paper, the semi-theoretical kinetics equations were proposed and the electro-dewatering experiments of sludge were conducted to analyze the kinetics laws of electro-dewatering under constan...

Coal refuse slurry impoundments have potential environmental concerns associated with water contamination and impoundment stability. Pressure filtration can be used as an alternative method of hand...

The development of electrokinetic dewatering technologies for clay and soil materials has steadily advanced for over 100 years. A review of the origins, important contributions, and recent work on the topic are presented. Research into the electrokinetic mechanisms have informed the design process and resulted in prototypes and pilot-scale implementations that are economically viable additions to current processes. The power demand and availability of dimensionally stable anode materials are the current challenges to industrial adoption of electrokinetic dewatering.

Coal mining by PT. Tambang Bukit Tambi uses an open pit mining system where one of the factors that can affect mining is water that entering the mining area, so water control must be carried out, one of the ways is by using mine dewatering system. The purpose of this study is 1) To know the debit of water entering the mining area. 2) To design a pumping plan 3) To create an ideal sump design for handling water that entering the mining area. Based on the research, the daily discharge is 32,243.36 m3 / day where the water discharge that can be released by 2 Kenflo XA 125 / 40B pumps is 640 m3 / hour in 50.38 hours and the water control effort is made a sump that must accommodate water amounting to 19,427.26 m3 and after the calculation is obtained a trapezoid-shaped sump design with size length and surface width of 63.7 m, length and width of the base of the sum of 60.9 m and depth of 5 meters.

In chemical recipes there can be found guidelines for efficient chemical production typically based on chemistry. However, such guidelines have never been checked with engineering methodologies for...

The efficiency of solid phase retention and dehydration of finely dispersed products of a coal processing plant and a metallurgical enterprise on the module for cleaning and dewatering sludge is investigated. A technique for selecting the operating parameters of equipment based on the determination of the strength criterion of flocs is proposed. A methodology for technological tests has been developed to control the flocculation process and optimize the flow of flocculant depending on the concentration of the solid phase. Industrial tests on the module for wastewater treatment and sludge dewatering using flocculants proved the effectiveness of the developed methodology. It is shown that the conditions for conducting tests on flocculation should correspond to the operating conditions of the circuit apparatus for cleaning and dewatering sludge. These conditions include sludge performance, sludge flow rate in the cross section of pipes and apparatuses, and the flow time from the flocculator to the centrifuge. During the testing of the Module, the solids retention efficiency of 97–99% was achieved with the strength criteria of flocs in front of a centrifuge of 2–2.5mm/s. The conditions for the high efficiency of the apparatus chain are the optimization of the aggregation process itself. It is revealed that for the formation of strong flocs it is necessary to regulate the concentration of the solid phase. For coal sludge, the concentration of the solid phase before the flocculant is fed must be maintained no higher than 50–60g/l, and for gas treatment sludge – no higher than 20–25g/l. Correction of the concentration of sludge before the flocculator is possible by diluting it with clarified water to the optimum concentration for aggregation. It is found that the moisture content of the sediment and the efficiency of the retention of the solid phase depend on the strength criterion of the flocs. Therefore, the optimization of the flocculant flow rate is possible by controlling and the residual floccule deposition rate after mechanical action in front of the dewatering equipment. The flocculant flow rate must be adjusted depending on the concentration of the solid phase in the sludge to achieve the desired criterion for the strength of the flocs

At present, large-scale engineering construction activities, especially deep foundation pit dewatering, are important factors of land subsidence in Shanghai, which induces uneven land subsidence. To solve this problem, this paper puts forward a technical approach to prevention and control the land subsidence. Based on the practice of joint work by multiple administrative departments in Shanghai, this paper further combines the technology and management measures effectively, and summarizes the management system of land subsidence control for deep foundation pit dewatering. Meanwhile, this paper provides the key workflow, starting from the whole process control of construction project for feasibility demonstration, design, construction and completion. The practice shows that the whole process of deep foundation pit dewatering control and management provides a powerful guarantee for land subsidence prevention and control.

In this study, wild-type microalgae species isolated from Porsuk river (Central Anatolia, Turkey) investigated as energy production feedstock and carbon dioxide sink. The obtained experimental data have been used for energy evaluation of the whole process and size estimation of large scale microalgae plant. Growth rate, CO2 mitigation rate, lipid, carbohydrate and protein content and natural settling behavior of the isolated species were investigated. The microalgae Gleocystis ampula had the highest growth rate equal to 0.138 +/- 0.008 g l(-1) d(-1) which also was observed to fix carbon dioxide with the highest rate of 0.281 +/- 0.025 g l(-1) d(-1). The highest measured lipid content of 47.32 +/- 0.40 wt% belonged to Scenedesmus quadricauda (I) with an estimated lipid production rate of 51.9 +/- 0.4 mg l(-1) d(-1). The species Kirchneriella lunaris showed the highest carbohydrate proportion being 72.43 +/- 6.40 and Micrococcus sp. had the highest protein content of 58.11 +/- 8.5 wt%. Promising large scale application of microalgae was concluded for biodiesel production and carbon dioxide mitigation just when efficiency of processes improved substantially. An Energy Efficiency of 1.62 was estimated following an ideally designed cultivation and dewatering approach.

Supercritical CO2 (sCO2) dewaters coal through two mechanisms. For bituminous coal of 9.5% average moisture content the water is dissolved out of the coal and the concentration of water in the bulk...

The use of water from mine dewatering has become increasingly important issue in northern China. Much of this water is discharged to the environment, which wastes a valuable resource and pollutes the ecosystem. To help address this, a feasibility analysis was carried on using deep Ordovician limestone water from dewatering at the Xinglongzhuang coal mine. First, a safe hydraulic pressure was estimated using the conventional water inrush coefficient method. Then, based on the results of a water release test (drilled into an artesian aquifer), a model representing the geology and hydrology of the study area was subsequently established and calibrated to existing conditions and water release test results, using the numerical simulation program FEFLOW. Finally, according to a contract signed between the mine and a local industrial water consumer, two cases of dewatering were discussed using the model to maintain a balance between mining safety and supplying water for nearby industrial operations. During the calibration and prediction analysis, the permeable faults were identified as the most important factor in water management and a key factor for balancing the aforementioned needs.

Tunneling slurry waste causes multiple problems, including environmental pollution, and requires transportation and a large landfill space, and therefore, it is important to find a method that can quickly separate water from tunneling slurry waste for metro construction. This paper proposes a practical method to improve the effect of slurry waste separation by implementing five laboratory tests. The results of these tests reflect that vacuum combined electro-osmosis is a suitable and practical method for treating tunneling slurry waste. The water content after treatment by vacuum combined horizontal electric field electro-osmosis method is not only lower than that after other methods but also close to the liquid limit, which fully meets the requirements of engineering transportation. However, vacuum and filter press dewatering cannot give full play to the drainage effect when the slurry permeability coefficient is too low. This combined technique can improve water separation from the slurry and works well in engineering applications.

Drying is the most critical process of the first heating cycle of monolithic dense refractories, as the reduced permeability of the resulting microstructure may lead to explosive spalling and mechanical damage associated with dewatering. The first part of this review series pointed out the various drying stages, the role of the binder components and the techniques that can be used to follow the water release in as-cast refractory materials, when they are exposed to heat. Although defining a suitable heating schedule is a great challenge, some tools can be applied to minimize the spalling risks associated with steam pressurization. In this context, this second review article points out (i) the main drying agents and how they affect the resulting castables’ microstructure (organic fibers, metallic powders, permeability enhancing active compounds, silica-based additives and chelating agents), and (ii) the effects related to the procedures commonly applied during the designing of heating routine (i.e., the role of the heating rate, ramp versus holding time), as well as the influence of the castable’s dimension on the overall drying behavior. Considering the recent advances regarding the design of refractory formulations and their processing, one may expect that incorporating suitable drying additives into the prepared composition should lead to a suitable and safer water release in such dense consolidated structures. Besides that, novel engineering opportunities, such as the use of in-situ based experimental techniques (i.e., neutron and X-ray tomography) to obtain more accurate data and the development of numerical models, might help in simulating and predicting the steam pressure developed in refractory systems during their first heating. Consequently, instead of designing conservative drying schedules based on empirical knowledge, the novel optimized heating procedures should be based on technical and scientific information.

Worldwide, every day human beings generate millions of tons of Faecal Sludge (FS), which is rich in water, nutrients, energy, and organic compounds. Yet FS is not being managed in a way that permits us to derive value from its reuse, while at the same time, millions of farmers struggle with depleted soils and lack of water. In most of the developing countries, energy for cooking is mainly derived from cutting of trees, either as wood or charcoal. Resource recovery and reuse from FS can create livelihoods, enhance food security, support green economies, reduce waste and contribute to cost recovery in the sanitation chain. Many studies have reported on the different technologies used for FS treatment, such as dewatering and bio-stabilization. The commonly used dewatering technology is sand drying bed, which occupied a large space and has a low dewatering rate. To enhance the dewatering rate of FS as well as reducing the size of the sand drying bed, the use of chemical conditioners has been done. Despite the fact that they have been used successfully, chemical conditioners are expensive, have health and environmentally hazardous. In recent years, attempts have been made to use local conditioners to tackle the drawbacks experienced from chemical conditioners. Although the feasibility of applying local conditioners for FS dewatering has been studied, its potentials on FS treatment have not been well documented. This review indicates that there is potential for local conditioners linked with dewatering, enhancing of FS resources recovery and in reducing costs of operating and maintaining FS treatment plant. Moreover, local conditioners have the potential in contribution to socio-economic development in Tanzania through renewable energy production, income generation and food- health security, soil and water conservation, eco-sanitation and reduction of environmental degradation. Keywords : Faecal sludge, Local conditioners, Resource recovery, Sanitation, Treatment.

Excessive coal moisture leads to a lower heating value and power plant efficiency, and increased transportation costs. Therefore, coal stockpile management and moisture control are particularly important in regions with heavy precipitation. This paper and Part 2 address factors influencing moisture retention and migration in coal stockpiles. Part 1 of this paper series simulates phenomena of runoff, infiltration, and drainage in a stockpile after a rainfall event. Part 2 reports the effect of coal particle size and climate conditions on the rate and depth of moisture evaporation process within a coal stockpile. To perform this study, two coal samples were collected from the Witbank mine in South Africa. The results of the present study showed that smaller interparticulate void spaces because of the compaction or fines particles (−0.5 mm fraction) inhibited infiltration, leading to increased runoff volume. An increase stockpile slope increased the amount of runoff due to coal–water contact time reduction. The ability of heavy rainfall to destroy near-surface structures (erosion) happened more readily at stockpiles with high slopes and high fine content. The fine content significantly influenced the dewatering efficiency of drainage. Coals with higher ash contents had stronger moisture retention ability than that of other coals even though coals with low ash contents had a high fine content. This was ascribed to the contribution of the clay minerals, such as kaolinite, in the high ash coal. The results of this paper can be used for the effective management of coal stockpiles to prevent excessive moisture in stockpiles for the best possible utilisation of coal in power plants.

In order to better improve the efficiency of the concentrate filter press dehydration operation, this paper studies the mechanism and optimization methods of the filter press dehydration process. Machine learning models of RBF-OLS, RBF-GRNN and support vector regression (SVR) are constructed respectively, and Perform laboratory simulation and industrial simulation separately. SVR achieves the best accuracy in industrial simulation, the simulated mean relative error (MRE) of moisture and processing capacity are respectively 1.57% and 3.81%. Finally, a simulation model of the filter press dehydration process established by SVR, and the optimtical simulation results Obtained by optimization method based on control variables. The results show that the machine learning method of SVR and optimization methods based on control variables are applied to industry, which can not only ensure the stability of expected production indicators, but also shorten the filter press dehydration cycle to less than 85% of the original.

Microalgal research has made significant progress in terms of the high-value-added industrial application of microalgal biomass and its derivatives. However, cost-effective techniques for producing, harvesting, and processing microalgal biomass on a large scale still need to be fully explored in order to optimize their performance and achieve commercial robustness. In particular, technologies for harvesting microalgae are critical in the practical process as they require excessive energy and equipment costs. This review focuses on microalgal flocculation, dewatering, and drying techniques and specifically covers the traditional approaches and recent technological progress in harvesting microalgal biomass. Several aspects, including the characteristics of the target microalgae and the type of final value-added products, must be considered when selecting the appropriate harvesting technique. Furthermore, considerable aspects and possible future directions in flocculation, dewatering, and drying steps are proposed to develop scalable and low-cost microalgal harvesting systems.

The dewatering of flocculated high density slurry presents a significant challenge to most mining industries. The new technologies to treat high density slurry require a consistent and robust flocculation method in order to enter the market of tailings management. The flocculation of high density slurry, however, due to its complexity, is always a challenge to be undertaken appropriately and to evaluate the dewatering performance correctly. This paper probes the complexity by using a torque-controlled mixing technique to demonstrate the influence of feed properties, polymer type, polymer dosage, and mixing conditions on dewatering performance. The study shows that flocculant should be dosed at the optimal range to achieve the highest dewatering performance. A full dosage responsive curve including under dosage, optimal dosage, and overdosage is critical to evaluate the dewatering performance of high density slurries and flocculants. The mixing conditions such as mixing speed, mixing time, and geometry of the mixing impeller affect the flocculation efficacy. It was found that the dewatering performance of high density slurry is sensitive to solids content, water chemistry, and clay activity. High sodicity and high clay activity in the high density slurry decreases the dewatering performance. Therefore, it is critical to evaluate flocculants across multiple feeds and dosages with replication in order to select optimal dewatering performance. Using multiple key performance indicators (KPIs) to build technical and economic criteria is also critical for polymer evaluation.

Microalgae are a sustainable rich source of high-added value metabolites, as omega-3 and carotenoids, for their ability to grow and accumulate these compounds also in wastewaters or in seawaters. Molecular distillation is a valid techinque respect to conventional distillation for fractionation of these thermosensitive products without affecting their nutritional and biological values. In this work a fractionation process using molecular distillation for separating fatty acids (in part omega-3) as esters and carotenoids from a microalgal lipidic extract, was designed and optimized. A Response Surface Method (RSM) analysis was carried out in order to find the optimal operative conditions of the molecular distiller in terms of temperature, pressure and purification ability. Furthermore, to complete the process scheme, also the design of the other equipments, including in particular the esterification reactor and the dewatering column, was done. In order to complete the feasibility study of the process, an estimation of the Operating Expense (OPEX) and Capital Expenditure (CAPEX), using the results of the simulations in terms of energy and utilities’ consumption, was done. All of these informations, both technical and economical, will be the basis for future industrial implementations of the designed process.

Postaeration, where digested sludge is introduced into aerobic conditions, is a technology that could improve the quality of sludge and sludge liquor in many ways. Although it is a fairly simple process, only few data about the effect of postaeration have been published. In this study, batch experiments have been performed first, indicating that postaeration affects the total ammonia nitrogen (TAN) and sludge dewaterability. In the removal of TAN, both stripping and biological oxidation can play an important role depending on specific condition. Then the postaeration was investigated in a semicontinuous batch reactor. In addition, the effect of postaeration on the concentration of selected micropollutants such as pharmaceuticals, EOX and AOX was studied. The hydraulic retention time (HRT) of 8, 6, 4 and 2 days and different aeration intensities were tested. The TAN removal efficiency achieved was about 40–60%, sludge dewaterability expressed by sludge cake total solids (TS) concentration after dewatering improved relatively by 5–30%. In addition, TS degradation is also taking place and therefore the reduction of the amount of final sludge to be disposed could be even higher. The biggest changes in observed parameters were recorded at the longest HRT.

Abstract The potential health risks associated with sludge cake application to agricultural land are managed by controlling the levels of Escherichia coli (E. coli) bacteria which indicate the risk of pathogen transfer. Analyses undertaken following post-digestion sludge dewatering have shown unpredictable levels of E. coli increase in stored sludge cake. Presently there is limited understanding on environmental parameters controlling the indicator bacteria density in storage and the contributory effects dewatering may have. This review aims to establish the state of current knowledge on innate and environmental factors influencing E. coli dynamics and survival in biosolids. A key factor identified is the effect of mechanical dewatering processes, which transform the sludge matrix environmental conditions through the increased availability of growth factors (e.g. nutrient and oxygen). Examples of storage practices from the agricultural and food industries are also discussed as successful methods to inhibit bacterial growth and survival, which could be extrapolated to the biosolids sector to regulate E. coli concentrations. Graphic Abstract

Dewatering in mineral processing industries is of paramount importance as most wet beneficiation of minerals needs removal of water. For this purpose, we have evaluated a 50.8 mm diameter hydrocycl...

The water contained in lignite generally exists in various forms and the energy required to remove them from coal is also different. Thus, two different rank lignites with different water contents from Yunnan and Inner Mongolia provinces in China were selected for analyses of water forms and dewatering energy consumption. The forms of water contained in these two lignites were classified using differential scanning calorimetry (DSC). The results show that the water in the lignite mainly contains freezable water and non-freezable water, and further the freezable water can be divided into free water and freezable bound water. The water above 40% moisture content of dry coal weight in coal sample is free water; that between 27% and 40% of dry coal weight is freezable bound water; and that less than 27% of dry coal weight is non-freezable water, which is nearly independent of coal rank. Then, the microwave drying and the fixed bed drying devices were employed to dry these two lignites, and the dewatering energy consumption during drying processes were measured and calculated to compare the change of energy consumption for removing different types of water. The results show that 500–600 W microwave field is suitable for drying lignite because the water is difficult to be completely removed under 450 W and slight pyrolysis is prone to occur for lignite when the microwave power is higher than 700 W. The dewatering energy consumption of total moisture in microwave field under 500–600 W is 8.6–15.3 kJ/g H2O, and those of freezable water and non-freezable water are 8.7–12.5 kJ/g H2O and 8.5–21.8 kJ/g H2O respectively. In addition, the dewatering energy consumption of 50 g lignite in fixed bed drying at 120–160 °C is 1.3–3.6 kJ/g H2O. In order to take advantages of microwave and fixed bed, these two methods are coupled to dry lignite for reducing energy consumption and improving drying efficiency. For the best compromise between drying energy and drying time, it is recommended to use 600 W power microwave field to remove free water in lignite, and then to use the fixed bed to remove the remaining water at 160 °C. The water re-adsorption amount of the upgraded coal is about 1/3 lower than that of raw coal.

A new method, i.e., flocculation–solidification combined method (FSCM), is proposed for building a working platform efficiently and economically at the surface of newly reclaimed ground filled with hydraulically dredged mud slurry at extra high water content (EHW-MS). A number of laboratory experiments are performed in this paper to identify the feasibility and mechanism of the proposed FSCM. First, the reasonable flocculant dosage range suitable for FSCM is determined by the simple sedimentation tests. Second, the engineering properties of FSCM, pure cement solidification method (PCSM) and pure flocculation conditioning method (PFCM) treated EHW-MS are compared in detail via a series of model tests, to demonstrate the superiority of FSCM over PCSM and the influence of flocculant dosage on FSCM efficiency. Third, the superiority of FSCM over PCSM is rationalized from the perspective of intrinsic working mechanism of flocculant and PCSM. Results demonstrate well that FSCM shows substantial superiority over PCSM, and at the reasonable flocculant dosage, the strength of FSCM-treated EHW-MS is at least 5.7 times larger than that of the corresponding PCSM-treated EHW-MS. The superiority of FSCM over PCSM can be attributed to two aspects, i.e., the dewatering effect and the other detrimental effect. The former is predominant and primarily governs the strength gain of FSCM-treated EHW-MS, while the latter is less significant but not negligible.

The optimisation of solid-liquid separation or dewatering processes for more efficient operation and reuse of material streams is of high importance. Suspension dewatering aims to increase the solids concentration and exhibits two limitations: the dewatering extent and the rate. A novel dewatering device, called High Pressure Dewatering Rolls (HPDR), has been developed. It combines shear and compression while maintaining a short filtration length between the rollers. The HPDR challenges the limitations of dewatering processes through the application of high pressures and induced shear to aid the extent of dewatering, and a short filtration length to allow fast dewatering. A prototype HPDR is described along with a performance assessment for different operating conditions as well as a comparison against state-of-the-art technology for a variety of industrial suspensions. The results demonstrate that the HPDR prototype, without any optimisation, outperforms or achieves comparable cake solids concentrations to existing equipment in a continuous mode of operation. Analysis of energy consumption and throughput remain outstanding and require further prototype development.

Microalgae-based biofuels have the potential to replace fossil fuels and contribute towards carbon sequestration. However, the growth of this industry is challenged by the financial viability of scale-up at various production stages. Dewatering is a critical stage which accounts for 20–30% of biofuels‘ production costs, therefore a techno-economic assessment of two dewatering cases was conducted. The first case was a conventional clarifier-centrifuge dewatering system (Case 1), while the second case investigated a single stage dewatering approach, using the wet-end of a paper machine (Fourdrinier former; Case 2). Mass and energy balances were modelled at a process scale of 175 t/d to produce biomass with 25% dry substance content, from which the associated costs were calculated. The minimum selling price (MSP) to achieve a return of 12% at a corporate tax rate of 30% over a 20-year plant life, was AU$354.28/t and AU$59.68/t for Case 1 and Case 2 respectively. Electricity cost was 90% of operational expenditure for two-stage dewatering and 38% for single stage. Case 2 made a better investment case with an annual profit after tax of AU$131,020 and net present value (NPV) of AU$164 million, as against that of Case 1 with an annual profit after tax of AU$112,610 and NPV of AU$71 million. The single stage dewatering deserves further investigation to fully explore the cost reduction potentials. The adoption of low cost technologies with reduced energy use implies lower embedded GHG emissions and process costs when compared to conventional technologies. This is desired for the near-term actualization of sustainable and clean production pathways for microalgae based biofuels.