Rheological Behavior Of Coal Water Slurry Research Articles

Combined effect of particle size distribution and cationic –anionic mixture surfactant on high ash coal water slurry

With the shortage of petroleum products and the depletion of the oil layer, the most significant scientific challenge is to use fuel most economically. Due to easy availability and low cost, more than decades of coal has been used in India for power generation in power plants. As CWS (coal-water slurry) has been accepted in many industries due to its low cost, easy handling, and low emission, still more research is needed to be done to work with multimodal high ash coal and simultaneously to save energy (like pumping power and to enhance the combustion temperature). In this experiment, the effect of high ash content coal in multimodal coal water slurry with additives and without additives and particle size distribution, shear rate, and shear stress on the rheological behavior of CWS has been investigated. By suitable combination, adding fine coal particles with the coarser, different samples were prepared and found that coal concentration of 67 % by weight having a viscosity within permissible value and after mixing with additives concentration of 50 % of CTAB (Cetyltrimethyl ammonium bromide) and SDC (Sodium di-dodecyl sulphate) the apparent viscosity reduces to the minimum value. Adding more CTAB in the slurry will increase the viscosity, and in the presence of these additives, the stability of MSA-1 is 18 days at a weight concentration of 67 %, meaning the slurry will work for 18 days. Significantly less work has been done in high-ash coal with multimodal samples. Here, an attempt has been made with this high ash multimodal sample along with the combination of mixture surfactant to achieve high concentration with less viscosity.

Synthesis and performance of a novel bio-oil-based dispersant as coal water slurry

With pyrolytic bio-oil as raw material, an efficient bio-oil-based dispersant (BOBD) applied to coal water slurry (CWS) has been synthesized successfully by grafting polymerization of the organic fractions from the bio-oil and acrylic acid (AA) in the mild condition. As a comparison, two commercial dispersants, namely poly (styrene sulfonic acid) sodium (PSS) and sodium lignosulfonate (SL) were employed. The structures and properties of the synthesized BOBD were characterized by using FTIR, 1H NMR, GC/MS, GPC, zeta potential, contact angle, and surface tension. The results showed the molecular weight of the BOBD was concentrated at 832 g/mol and 1954 g/mol. The surface tension and contact angle of BOBD aqueous solution were 47.71mN/m−1 and 60.8° respectively. The zeta potential of the suspension prepared from BOBD-water-coal was −67.1 mV. Using BOBD as a dispersant, the apparent viscosity of CWS loading 66 wt% coal dropped to 288 mPa·s at 0.3 wt% BOBD, and the maximum coal content reached 72 wt%. BOBD exhibited better viscosity reduction and stability enhancement capabilities than PSS and SL. The excellent dispersion performance of BOBD was due to the large electrostatic repulsion and steric hindrance derived from the grafted acrylic polymer, which effectively dispersed the coal particles uniformly. The rheological behavior of CWS with BOBD belonged to pseudoplastic fluid. The synthesized BOBD not only had an excellent dispersion performance but also could overcome the shortcomings of secondary pollution caused by PSS and SL containing element sulfur as dispersants in combustion. In addition, the synthetic route possessed simple, environmentally friendly and sustainable characteristics. The research opened up a new way for the utilization of bio-oil.

Rheological behavior of coal-water slurries of Indian coals using carboxymethylcellulose as dispersant- a comparative study

ABSTRACT The rheological nature of coal-water suspensions of two Indian coal samples (namely coal 1 and coal 2) was reported and compared in the shear rate range of 60–160 s−1 at constant pH of 8. Proximate and ultimate analysis were used to characterize the coal, and zeta potential and turbidity measurements were carried out to test the suitability and selection of carboxymethylcellulose (CMC) as a dispersant for the Coal Water Slurry (CWS). The effects of percentage solid loading, dispersant dosage on the rheological nature were studied. The rheological data was fitted for the power law model to categorize the slurry flow nature with reference to the calculated flow behavior index of the model. At lower solid loadings (10%, 20%), the shear stress-shear rate relation did not alter with the dispersant dosage and the slurries exhibited shear thickening behavior. The effects of the slurry parameters were quite predominant at 30%, 40%, and 50% solid loadings as they exhibited the shear thinning behavior. The slurry with 30% solid loading showed transition from shear thickening to shear thinning with the increase in dispersant dosage. For a given percentage of solids, a lower magnitude of shear stress versus shear rate, a wider distribution of flow behavior index and favorable pumpable characteristics were seen for coal 1 in comparison to coal 2 owing to their chemical nature and amount of ash-bearing mineral constituents.

Rheological behavior of coal-water slurry using sodium tripolyphosphate as a ​dispersant

ABSTRACT The rheological nature of coal-water suspensions of an Indian coal variety is reported in the shear rate range of 60–160 s−1. Sodium tripolyphosphate (STPP) is used as a dispersant or chemical additive for the slurries. The effects of percentage solid loading, dispersant dosage and pH on the rheological nature are comprehensively studied. The rheological data is fitted for power-law model to categorize the slurry flow nature with reference to the calculated flow behavior index of the model. At lower solid loadings (10% 20%), the shear stress-shear rate relation did not alter with the dispersant dosage or pH and the slurries of exhibited dilatant behavior. The effects of the slurry parameters are quite predominant at higher solid loadings (30%, 40%, and 50%). For pH ≥ 8.0, dilatancy of the slurries were observed for 30% solids loadings with dispersant in some cases. Excluding this, the higher percent solid loadings exhibited shear thinning behavior. For a fixed shear rate, the shear stress decreased with increasing pH at higher dispersant dosages which confirms the sharp effect of pH on the slurry rheology with the dispersant addition. The increased adsorption of the anionic dispersant (STPP) on the solids at higher pH values is the reason for this trend.

Influence of Particle-Size Distribution and Temperature on Rheological Behavior of Coal Slurry

The rheological behavior of coal-water slurry of Indian coal is studied using rheometer. The effect of particle size, solid concentration, and temperature on the rheology of the coal-water slurry has been investigated. The settlement analysis of various size ranges of coal particles has been carried out. A particle size less than 75 µm is used for analysis of rheological behavior of coal slurry and it is found that the increase in solid concentration caused the increase in apparent viscosity of the coal-water mixture. Also, it is observed that as the solid concentration increases the coal-water mixture converts to a non-Newtonian fluid. The rheological behavior of the slurry is also analyzed by blending the coal samples with mixture of coarse and fine particles, hence making a bimodal particle-size distribution. The slurry having the bimodal particle-size distribution is prepared by blending the fine particles of 53–75 µm with the coarse particles of 106–150 µm or 150–250 µm with various proportions. The optimum fraction obtained in bimodal slurry sample is 30% at which point the apparent viscosity is minimum. The change in the flow behavior of coal slurries are fitted to rheological models and the model parameters are calculated.

Effect of the Interfacial Agents with Different Types of Hydrophilic Functional Groups on the Rheological Properties of Coal-Water Slurry

Five interfacial agents with different hydrophilic groups (DBS, SDS, SO, TX, CTAB) are used as model additives to prepare coal-water slurry (CWS). The effects of different interfacial agents on the rheological properties of CWS are systemically investigated, the microscopic aggregation behavior of coal particles in the suspensions and the zeta potentials in coal-water interface are also studied. Based on the interpretation of the results, the rheological behavior of CWS is greatly influenced by the adsorption pattern of the interfacial agents in coal-water interface. The adsorption patterns of anionic interfacial agents on coal surface are mainly influenced by the combining force between the anionic hydrophilic groups with Ca2+, the stronger combining force with Ca2+ leads to the apparent viscosity increase and heavier pseudo-plastic property of CWS. The adsorption pattern of nonionic interfacial agent on coal surface is seldom influenced by the hydrophilic polyoxyethylene chain, and the addition of nonionic interfacial agent reduces the apparent viscosity of CWS. The adsorption pattern of cationic interfacial agent on coal surface is determined by its cationic head, and the addition of cationic interfacial agent increases the apparent viscosity of CWS. The concluded adsorption models of the interfacial agents with different hydrophilic groups can be guidance for the molecular design of high-performance additives of CWS.

Studies on Preparation of Coal Water Slurry Using a Natural Additive

An eco-friendly additive isolated from a natural plant has been developed in the laboratory for preparation of coal water slurry (CWS) of some specific Indian coal. The effect of additive concentration, the rheological behavior of CWS at weight concentrations varying from 55–63.7% using a rotational viscometer, the static stability tests, etc., have been investigated. The nature of the slurries followed Bingham plastic behavior in these range of concentrations, and the slurry viscosity recorded over these solid weight concentrations varied between 0.42–0.97 PaS by using the natural additive. The rheological behavior of CWS was compared with commercial additives with a possibility to replace it with the natural additive. The static stability studies on CWS of the low- and medium-ash coal water slurries were found to be 27 and 21 days, respectively.

Rheological Behavior of Coal-Water Slurry

The rheological behavior of some Indian coal-water slurry (CWS) was investigated using a HAAKE RV30 viscometer. The objective was to study the effect of solid concentration, ash content, pH, and temperature on the rheology of CWS. It was found that CWS exhibits pseudoplastic behavior. The apparent viscosity varies with the amount of coal in the slurry, pH, and temperature, which is the highest around pH 6 and the lowest near pH 8. The effect of temperature on the viscosity could be described using an Arrhenius type of relation.

97/04490 Characterization of dispersant structures and their effect on rheological behavior of coal-water slurries: Sun, C. et al. Ronliao Huaxue Xuebao., 1997, 25, (3), 213–217. (In Chinese)

Late Jurassic organic-rich shales from Shabwah sub-basin of western Yemen were analysed based on a combined investigations of organic geochemistry and petrology to define the origin, type of organic matter and the paleoenvironment conditions during deposition. The organic-rich shales have high total sulphur content values in the range of 1.49–4.92 wt. %, and excellent source rock potential is expected based on the high values of TOC (>7%), high extractable organic matter content and hydrocarbon yield exceeding 7000 ppm. The high total sulphur content and its relation with high organic carbon content indicate that the Late Jurassic organic-rich shales of the Shabwah sub-basin were deposited in a marine environment under suboxic-anoxic conditions. This has been evidenced from kerogen microscopy and their biomarker distributions. The kerogen microscopy investigation indicated that the Late Jurassic organic-rich shales contain an abundant liptinitic organic matter (i.e., alginite, structureless (amorphous organic matters)). The presence of alginite with morphology similar to the lamalginite alga and amorphous organic matter in these shale samples, further suggests a marine origin. The biomarker distributions also provide evidence for a major contribution by aquatic algae and microorganisms with a minor terrigenous organic matter input. The biomarkers are characterized by unimodal distribution of n-alkanes, low acyclic isoprenoids compared to normal alkanes, relatively high tricyclic terpanes compared to tetracyclic terpanes, and high proportion of C27 and C29 regular steranes compared to C28 regular sterane. Moreover, the suboxic to anoxic bottom water conditions as evidenced in these Late Jurassic shales is also supported based on relatively low pristane/phytane (Pr/Ph) ratios in the range of 0.80–1.14. Therefore, it is envisaged here that the high content of organic matter (TOC > 7 wt.%) in the analysed Late Jurassic shales is attributed to good organic matter (OM) preservation under suboxic to anoxic bottom water conditions during deposition.