Slurry Ability Research Articles

The effect of modified oily sludge on the slurry ability and combustion performance of coal water slurry

Abstract The aim of this study is to find a solution to the challenging problem of disposing oily sludge (OS). Three different types of modifiers, namely, sodium hydroxide (NaOH), sodium dodecylbenzene sulfonate (SDBS), and polyoxyethylene polyoxypropylene polyether (AE) were employed for the simple modification of OS. The influence of modified OS on slurry ability and combustion performance were investigated. The results showed that OS modified by NaOH and SDBS can increase the concentration of coal OS slurry. However, the influence of AE modification on slurry concentration is intricate. In terms of combustion performance, the change in activation energy results in NaOH and SDBS modifications decrease T i and T h of coal OS slurry, while AE modification increases T i and T h of coal OS slurry.

Slurry-ability mathematical modeling of microwave-modified lignite: A comparative analysis of multivariate non-linear regression model and XGBoost algorithm model

In the preparation of microwave-modified lignite (ML) water slurry (MLWS), its specific surface area, oxygen functional groups and oxygen-carbon atomic ratio are important factors affecting the slurry ability. Based on the relationship between the physicochemical properties of 23 ML samples and their maximum solid concentrations, a multivariate nonlinear regression (MNR) model and a machine learning model based on XGBoost algorithm were established to predict the slurry ability. The determination coefficient (R2), the mean average error (MAE) and the mean squared errors (MSE) for MNR mode is 0.928, 0.507 and 0.391, respectively. The R2, MAE and MSE for XGBoost model is 0.582, 0.619 and 0.667, respectively. Hence, the MNR model with less error percentage has a higher accuracy than the XGBoost model, but the XGBoost model is highly efficient, flexible and portable with strong generalization ability to unknown data. Overall, the proposed models in this study have a good effect on the prediction of the slurry ability of ML, and serve as a technical reference for future predicting the slurry ability of other types of coal.

Insights into the Dispersion Mechanism of Microfine Coal Particles Modified with Naphthalene Sulfonate Formaldehyde Based on EDLVO Theory

Coal water slurry (CWS) fuel prepared using microfine coal particles with a size distribution of 1–10 μm is a promising way to cleanly utilize solid resources in engines, even catering a popular application for clean coal technology. In an attempt to address the problems in coal aggregation in microfine coal water slurry (MCWS), dispersants are used to improve the dispersing status of microfine coal particles. Based on the experimental results and extended Derjaguin–Landau–Verwey–Overbeek (EDLVO) theory calculations, the role of naphthalene sulfonate formaldehyde (NSF) in MCWS performance was explored. The measurement of the slurry ability of microfine coals demonstrated that the apparent viscosity and yield stress of MCWS were decreased significantly with 1.5% NSF addition, which was consistent with the saturated adsorption value of NSF on microfine coals. Furthermore, the ζ-potential and contact angle of microfine coals were both decreased as a function of the NSF dosage, indicating that a larger electrostatic repulsion force and better wetting ability of the coal surface would be obtained in the presence of NSF. The thickness calculation results showed that the thickness is increased with NSF addition, which is attributed to that the NSF molecule extends into the surrounding solution to form a hydrophilic film. The EDLVO calculations illustrated that the total interaction was turned from an attractive force into a repulsive force in the case of NSF, noting that the better dispersion of microfine coals mainly resulted from the better hydrophilicity of the coal surface modified with NSF. The findings might provide guidance for MCWS preparation by revealing the interaction mechanism of microfine coals modified with NSF.

Study on prediction model of slurry concentration of low-rank coal and anionic sulfonate additives

In this work, eight kinds of low-rank coal and four kinds of anionic sulfonate additives including lignin series, naphthalene series, humic acid series, and aliphatic series dispersants were selected for slurry experiments. The Spearman correlation analysis method was used to investigate the influence of coal quality factors including moisture, ash, volatile matter, fixed carbon, O/C value, and peak area ratio CO/CO value on the slurry ability of low-rank coal under different dispersant conditions. The results show that moisture, volatile matter, O/C value, and CO/CO value in coal are negatively correlated with slurry ability, while ash and fixed carbon are positively correlated with slurry ability. According to the Spearman correlation coefficient, moisture, volatile matter, O/C value, and CO/CO value in coal are closely related to the slurry ability of low-rank coal. The prediction model of slurry concentration of low-rank coal and anionic sulfonic acid additive based on coal characteristic factors is established by partial least squares (PLS):ySLS=75.859-0.498x1+0.566x2-5.786x3-157.895x4yNSF=79.706-0.123x1+0.567x2-7.123x3-182.900x4ySHS=80.642+0.012x1+0.387x2+4.503x3-180.657x4ySAF=80.702+0.271x1+0.508x2-18.743x3-182.057x4Where yi is the constant-viscosity concentration, the unit is %; x1 is moisture (Mad), the unit is %; x2 is volatile (Vdaf), the unit is %; x3 is the O/C value; x4 is CO/CO value. By comparing the experimental value with the predicted value, the R2 value of the linear regression fitting is larger than 0.95, the error rate is within ± 3 %, and while using the constant-viscosity concentration to determine the matching performance of coal and dispersant, the predicted value is consistent with the experimental value, which verifies the rationality and accuracy of the model.

Influence and mechanism of alkali-modified sludge on coal water slurry properties.

Municipal sludge (MS) is used to prepare coal water slurry (CWS). This practice is beneficial for resource utilization and reduces treatment costs and environmental pollution. In this study, alkali-modified municipal sludge (AMS) was prepared with Ca(OH)2 as modifier and mixed with coal to produce AMS-CWS. The effect and mechanism of MS and AMS on slurry ability, stability, and combustion characteristics of the CWS were explored. The results of the pulping experiments showed that the slurry concentration of the AMS-CWS was approximately 10% greater than that of MS-CWS. The water separation rates of MS-CWS and AMS-CWS were 5% and 5.26%, respectively, which were 13.62% and 13.36% less than that of CWS (18.62%). The zeta potential experiments verified these results. Combustion performance research shows that both MS and AMS have positive effects on combustion performance. The results of the contact angle experiments showed that the hydrophobicity of AMS was enhanced, which was beneficial for improving the pulping capacity of MS-CWS.

Eco-friendly utilization of waste oil for preparing coal water slurry: Additive suitability and dispersion mechanism

Industrial waste oil is a type of hazardous waste with a high calorific value. Mixing it with coal for combustion or gasification is an environmentally friendly and efficient way of recycling. Here, the suitability of additives for waste oil-coal slurry and waste oil-coal-water slurry was investigated experimentally, and their dispersion and stabilization mechanisms were also explored. The results show that water-soluble additives such as Tween 80, MF and xanthan gum form reverse micelles in the oil phase of the waste oil-coal slurry, which results in agglomeration and failure to function as intended. Of the different additives, the viscosity reduction effect of Tween 80 in the waste oil-coal-water slurry was best. Further, the comprehensive performance of the waste oil-coal-water slurry, including slurry ability, stability and fluidity, was found to be best at a water content of 10% and a Tween 80 content of 5%. Under these conditions, a solid concentration of 45.75% results in a continuously flowing slurry with good dispersion and stability. The interface properties of coal particles, oil, and water were studied by means of Fourier transform infrared spectroscopy (FTIR) and contact angle measurements, and a dispersion and stabilization mechanism for the waste oil-coal-water slurry was proposed. In this mechanism, some of the coal particles enter the reverse micelle, causing the water core to become a hydration film on the surface of the particles, which blocks hydrophobic particle aggregation. In addition, the surfaces of some coal particles are rapidly coated with an oily film, which also inhibits particle aggregation.

Gel Stability of Calcium Bentonite Suspension in Brine and Its Application in Water-Based Drilling Fluids.

With the development of the oil industry and the increasingly complex drilling environment, the performance of drilling fluids has to be constantly improved. In order to solve the problem of bentonite dispersion and hydration in a saline medium, a drilling fluid additive with good performance and acceptable cost was sought. The effects of several water-soluble polymers, such as cellulose polymers, synthetic polymers and natural polymers, on the rheology and gel suspension stability of calcium-based bentonite were compared in this study. Among the examined polymers, the xanthan gum biopolymer (XC) was the least negatively affected in the saline medium used. However, its high price limits its industrial application in oil and gas drilling fluids. In this study, a salt-tolerant polymer, modified vegetable gum (MVG), was prepared by a cross-linking modification of a natural plant gum, which is abundant and cheap. Then, a salt-tolerant polymer mixture called SNV was prepared, composed of the salt-resistant natural polymer MVG and the biopolymer XC. The salt tolerance and slurry ability of SNV and common water-soluble polymers were evaluated and compared. We then selected the most suitable Herschel–Bulkley model to fit the rheological curve of the SNV–bentonite aqueous suspension system. SNV improved the rheological properties of the calcium-based bentonite slurry and the dispersion stability of bentonite. In an SNV concentration of 0.35%, the apparent viscosity (AV) of the base slurry increased from 2 mPa·s to 32 mPa·s, and the low shear reading value at 3 rpm increased from 0 dia to 5 dia. This could greatly improve the viscosity and cutting carrying capacity of the bentonite drilling fluid. The bentonite drilling fluid prepared with SNV could be directly slurried with brine and even seawater; this means that when drilling in ocean, coastal saline water and high-salinity-surface saline water areas, the slurry preparation cost and preparation time can be conveniently reduced.

Development and application of guar gum crosslinked gel with adjustable gelation time for total loss treatment

To remediate the problem of severe or total losses, and meet the requirements of borehole plugging and pumping at different well depths, a novel crosslinked polymer gel (named HPG/Zr gel) with controlled gelation time and high gel strength was developed as loss circulation material, which mainly comprised hydroxypropyl guar gum, zirconium compound and triethanolamine. The influence of hydroxypropyl guar gum concentration, zirconium compound concentration, triethanolamine concentration and temperature on the gelation time of HPG/Zr gel was evaluated. In addition, the performance of HPG/Zr gel was investigated in terms of temperature resistance and shear resistance property, plugging ability and supporting cement slurry ability. According to the results, HPG/Zr gel can form a viscoelastic body with a network structure, and its gelation time can be practically adjustable. The results of the plugging experiment at different temperatures, pressures and pore sizes of quartz sand revealed that HPG/Zr gel could effectively plug sand pores at 150°C, and its pressure-bearing capacity can be up to 5 MPa. Employing its flow resistance and ability of supporting cement slurry, HPG/Zr gel was successfully applied in two geological boreholes by combining with cement slurry. Overall, the results of laboratory research and field tests indicate that HPG/Zr gel is useful for mitigating the lost circulation, and it is of huge importance to engineering applications.

Improve the slurry ability of lignite through co-slurrying and microwave co-pyrolysis with direct coal liquefaction residue

This study is devoted to demonstrating experimentally the advantages of direct coal liquefaction residue (DCLR) on improving the slurry ability of lignite through co-slurry and microwave co-pyrolysis. The results show that: as the lignite/DCLR mass ratio decreased from 10:0–5:5 the maximum solid concentration (MSC) of the mixed slurry increased from 42.14 wt% to 54.25 wt%, simultaneously, the pseudoplasticity and static stability gradually decreased. This is because the organic matter and abundant minerals in DCLR remarkably changed the slurry ability of mixed slurry. And during microwave pyrolysis with the assist of 12 wt% DCLR the slow drying stage of lignite pyrolysis was shortened, and the constant temperature stage was extended, thus, the coal quality was improved, the oxygen-containing functional groups was removed significantly and the BET specific surface area increased. These changes caused the MSC of upgraded lignite water slurry (ULWS) increased to 64.54 wt%; but the “shear-thinning” characteristic became inconspicuous, and the static stability became slightly worse. In general, DCLR could effectively improve the slurry ability of lignite through co-slurry with lignite at a mass ratio of 5:5 and co-pyrolysis with lignite at a microwave power of 1000 W.

Physicochemical properties and slurry ability changes of lignite after microwave upgrade with the assist of lignite semi-coke

Microwave pyrolysis is a promising technique for the clean and effective utilization of low-rank coal, which has aroused widespread concern during the past decades. This paper applied microwave energy with the assist of 10 wt% lignite semi-coke (LSC) to upgrade lignite and prepared the solid residue into lignite water slurry (LWS). The physicochemical property and slurry ability changes of upgraded lignite were analyzed. The micro-mechanisms on interactions between dispersant molecules and upgraded lignite particles were investigated through Molecular Dynamics (MD) simulations. It turns out that LSC could effectively prompt the rapid heating of lignite in the microwave field. And after microwave upgrade the coal quality of lignite was improved, the oxygen-containing functional groups was removed remarkably. The adsorption conformation of dispersant on the lignite-water interface exhibited a double adsorption, while that on upgraded lignite-water interface gradually showed single-layer and multi-point adsorptions. Besides, the physicochemical property changes varied most when lignite was upgraded under 800 W, which leads to the maximum solid concentration of LWS improved most, from 51.84 wt% to 61.45 wt%. It further increased to 62.43 wt% as the LWS was directly prepared from the solid residues after microwave irradiation. Morever, the pseudoplasticity of LWS became weaker, but the static stability became better. Therefore, LSC, a self-product of lignite, exerted an enormous function on improving the slurry ability of lignite.

Effect of Hydrothermal Dehydration on the Slurry Ability of Lignite.

The high moisture content limits the large-scale utilization of lignite. Hydrothermal dehydration (HTD) has been confirmed as an effective method to improve the quality of lignite for further utilization. In this study, the effects of the changes in the lignite interface properties caused by the HTD modified final temperature on the slurry ability were investigated in the range of 160–200 °C. The results indicated that with the gradual rise of the HTD modified final temperature, the content of the carboxyl groups and phenolic hydroxyl groups on the surface of lignite decreased by 21.95 and 36.34%, respectively. In the meantime, the atomic ratio of oxygen/carbon, the content of equilibrium moisture, and the thickness of the hydrated film were reduced from 0.293, 14.63%, and 34.26 nm to 0.252, 9.43%, and 13.33 nm, respectively. Therefore, these changes of interfacial properties improved the slurry ability of lignite, with higher fixed-viscosity solid concentration, lower yield stress, increased pseudo-plasticity, and gradually decreased static stability of the prepared lignite coal water slurry. hydrothermal dehydration; slurry ability; oxygen-containing functional groups; hydrated film

The Enhancement on Rheology, Flowability, and Stability of Coal Water Slurry Prepared by Multipeak Gradation Technology

Multipeaking gradation technology is an essential method for improving the slurry ability of coal particles. In this study, the coarse (150–300 μm), fine (54–74 μm), and micro (1–10 μm) coal partic...

Improvement on slurry ability and combustion dynamics of low quality coals with ultra-high ash content

It is a significant subject that low quality coals could be used for high concentration slurry preparation because of the large reserve and low price. Nevertheless, due to the microstructure and surface properties of low quality coals, it is difficult to prepare qualified coal water slurry (CWS) directly. In this study, an improved flotation technique was employed to upgrade two low quality coals, then Jinda raw coal (JD-RC) and its upgraded coal (JD-UC), together with Jisuo raw coal (JS-RC) and its upgraded coal (JS-UC) were applied to CWS preparation and combustion dynamics analysis. Results showed that after two samples of low quality coals were upgraded, the maximum slurry concentration could be increased by 6%. It was attributed to the variation of free water content, which was mainly influenced by composition and pore structure of coal particles. Because of the remarkable decrement on specific surface area and porosity after flotation, the ignition temperature and apparent activation energy of CWS prepared by JD-UC were increased comparing to JD-RC. However, the ignition temperature and apparent activation energy of CWS prepared by JS-UC were lower than JS-RC, which was resulted from the higher combustible content in JS-UC. The results of this study provided a method for the preparation of high concentration CWS using low quality coals with ultra-high ash content.

Effects of coal slime on the slurry ability of a semi-coke water slurry

As a by-product of the coal washing process, the methods involving the resource utilization of coal slime are very few because of its strong agglomeration and large water content. In this work, we propose a new way to dispose of coal slime, which involves preparing semi-coke water slurry (SCWS) with coal slime. When using sodium humate as dispersant at a dosage of 0.8wt%, the solid concentration of ordinary SCWS reached a maximum (63.8wt%) , and the concentration improved to 65.3wt% after adding 15wt% coal slime, and the calorific value of the slurry (18.07MJ/kg) that can meet the Chinese standard (GB/T 18855–2002). The role of coal slime in improving the ability of SCWS is to optimize the particle size distribution as a small size material; additionally, it can improve the hydrophilicity of particulates through oxygen-containing groups and minerals, which increased the performance of SCWS.

Effect of injection parameters on proppant transport in rough vertical fractures: An experimental analysis on visual models

The understanding of proppant flow through fractures is critical in evaluating the performance of hydraulic fracturing operations. As a continuation of our experimental efforts devoted to understanding how proppant flows in rough vertical fractures, in this paper, we examine the effect of injection parameters on the proppant transport in rough vertical fractures. The effects of polymer concentration, injection rate, proppant concentration, and type of proppant were investigated in detail. Experimental results show that, in general, two types of settling patterns can be observed in the proppant transport in a rough fracture: sand-dune settling pattern and tree-like settling pattern. The following conditions tend to suppress the tree-like settling behavior of proppants in the rough fracture: a higher density of the proppants, a lower viscosity of the polymer solution, and a lower injection rate. This is attributed to a higher settling velocity of the proppants in the fracture under these conditions. A sufficiently high polymer concentration is needed to enable effective proppant flow in rough fractures. In general, the relative coverage of proppants increased dramatically as the polymer concentration increased, implying that the higher viscosity of fracturing fluid could enhance the slurry's ability to place more proppant vertically into the fracture and help to maintain a better conductivity after fracturing treatment. A sufficiently high injection rate of the slurry is also needed to enable effective proppant flow in rough fractures. At certain low injection rates, the proppants carried by a low polymer solution might not exhibit a tree-like settling pattern, diminishing the effect of roughness on the proppant transport. This means that even in rough fractures, the tree-like settling pattern of the proppants did not necessarily occur for sure; the injection rate should be properly selected to enable such phenomenon. With other conditions being kept constant, a higher proppant loading led to a higher final relative coverage of the proppants in the rough fractures. But if the injection rate used for delivering the proppants is not sufficiently high, we may encounter injectivity issues; in our lab experiments, this caused the choking of the pump. The heavier proppant (ceramic proppants) in the rough fracture models tended to suppress the tree-like settling pattern that was experienced by the lighter proppant (silica sands). This is attributed to the larger density of the ceramic proppants, leading to a larger settling velocity. In order to maximize the spreading of a given proppant over a rough fracture model, we should determine the proper values of all the essential injection parameters (including polymer solution, injection rate, proppant concentration) by striking a good balance among them. The conclusions obtained in this study shed light on how to optimize slurry injection parameters to achieve an optimal proppant-filling ratio during hydraulic fracturing.

Study on the slurry ability and combustion behaviour of coal‐bioferment residue of drugs‐slurry

AbstractBioferment residue of drugs (BRD) is one kind of harmful and hazardous substance which has complex compositions. Thus, proper treatment of these residues has become an important concern. BRD can be utilized harmlessly and economically by mixing it with coal powder, water, and dispersant to prepare slurry fuel, named as coal‐BRD‐slurry (CBRDS). In this study, the influence of BRD on the slurry ability and combustion behaviour of CBRDS was investigated with coal water slurry (CWS) as reference. Results showed that the dispersant can reduce the slurry viscosity of CBRDS and CWS, and its optimum dosage was 0.6 wt% on the dried coal basis. The fixed‐viscosity concentration of CBRDS decreased with increasing BRD dosage. CBRDS and CWS exhibited shear‐thinning behaviour. The rheological behaviour was fitted by the power law. CBRDS exhibited higher apparent viscosity and stronger shear‐thinning behaviour because of the flocculent structure and well‐developed pores of the BRD. BRD can improve the stability of CWS by decreasing solid‐liquid separation of the slurry. Addition of BRD decreased the ignition temperature and increased the ash residues, suggesting a synergistic effect of CWS and BRD occurred during the combustion of CBRDS.

Improvement on slurry ability of lignite under microwave irradiation

Under 900W, the effects of microwave irradiation time on the solid concentration, rheology and static stability of lignite water slurry (LWS) were investigated. The results showed that with the gradual increase of microwave irradiation time the hydrated film on lignite became thinner and it contributed to the maximum solid concentration of lignite increased from 51.63% to 55.30% (irradiated for 12min). At the same time, the oxygen/carbon and hydrogen/carbon atomic ratios decreased, the moisture content and oxygen-containing functional groups gradually removed, and the lignite surface became smooth. The changes of these interfacial properties improved the pseudo-plasticity and reduced the yield stress of LWS. Besides, the changes in lignite surface caused larger dispersant adsorption on lignite surface and therefore enhanced the static stability of LWS.

Characteristics of coal sludge slurry prepared by a wet-grinding process

Coal sludge slurry (CSS) is an alternative fuel and a potential competitive method for sludge reduction. Based on the researches of coal water slurry, we studied CSSs by using a wet-grinding process with different types of regional municipal sludge (sludge) in an orthogonal experiment. The sludge type, sludge mixing proportion, dosage of dispersant, and grinding time were tested in this study. The results show that water content and its occurrence characteristics in the sludge have primary hindering influences on slurry ability. The range of fixed-viscosity concentrations with raw wet sludge is from 50.78% to 44.40% (by weight), while the range is from 53.35% to 51.51% (by weight) with dry sludge. All of the CSSs exhibit shear-thinning behaviors with different variation trends, especially the CSSs with more than 15% (by weight) raw wet sludge in it. Adding the same proportion of raw wet sludge increases the thixotropic properties of CSSs and the highest area of thixotropy loop is 3065Pa/s, while the highest value of dry sludge is 1798Pa/s. Hydrophilic group plays an important role in adsorbing water and building three-dimension networks with other particles, which is the main reason for CSS properties. Therefore, the mechanism can be used to find the way for making high quality CSS.

Fractal characteristics of pore structures in 13 coal specimens: Relationship among fractal dimension, pore structure parameter, and slurry ability of coal

The fractal characteristics of pore structures in 13 different coal specimens were investigated. Insights into the relationship among fractal dimension, pore structure parameter, and slurry ability of coal were provided. N2 adsorption/desorption at 77K was applied to analyze the pore structure of coal. Two fractal dimensions, D1 and D2, at relative pressures of 0 to 0.45 and 0.45 to 1, respectively, were calculated with the fractal Frenkel–Halsey–Hill model. Results reveal that the value of D1 is mainly affected by the influence of meso- and macro-pores with an average pore size range of 10nm to 220nm on the specific surface area; therefore, D1 can be utilized to quantitatively describe the surface roughness of these meso- and macro-pores in coal. Meanwhile, the value of D2 is mainly related to the effects of fine mesopores with an average pore size range of 2nm to 10nm on the total pore volume; therefore, D2 can be utilized to quantitatively describe the volumetric roughness of these mesopores in coal. D1 has no apparent linear correlation with the pore structure parameters and maximum solid loading of coal, and D2 has a positive linear correlation with the specific surface area and total pore volume of coal. The increase in specific surface area, total pore volume, and D2 has negative effects on the slurry ability of coal. High-rank coals with high ash content and low volatile matter relatively have higher D1 and lower D2. Meanwhile, with increasing coal rank, D2 has a decreased trend. The fine mesopores with an average pore size range of 2nm to 10nm in coal have direct effects on the pore structure parameters and D2 of coal; thus, the slurry ability of coal may be improved if the number of these mesopores in coal is reduced by modification processes, such as microwave irradiation, hydrothermal treatment and so on.

The properties of Chinese typical brown coal water slurries

ABSTRACTEight typical Chinese brown coals were evaluated for their potential as coal water slurries (CWSs). The solid ratios and stability of brown coal water slurries were studied and compared with bituminous coal slurries. Results showed the amounts of oxygen functional groups in brown coals are much higher than that in bituminous. Thus, solid ratios at fixed viscosity for brown coal slurries are about 46–55%wt, much lower than those for the bituminous samples that are about 65%wt. Most slurries of brown coals exhibit good stability. Moreover, additives never universally improve slurry ability and stability simultaneously.