Preparation Of Coal Water Slurry Research Articles

Characterization of coal water slurry prepared for PRB coal

Powder River Basin (PRB) coal, which accounts for over 40% of the coal consumed for power generation in the United States, was investigated for preparation of coal water slurry (CWS). The static stability and rheology of the CWS were characterized as a function of loading. The coal loading was varied from 30% to 50% and both ionic (sodium polystyrene sulphonate (PSS)) and nonionic (Triton X-100) surfactants were employed as additives. The addition of PSS to PRB slurries was found to yield poor static stability. On the other hand, Triton X-100 was found to be an effective surfactant, reducing the sedimentation by more than 50% compared to the one without surfactant in 45% CWS. Adding Triton X-100 reduces the viscosity of the CWS for coal loadings of 30% and 40%. Although the viscosities for coal loading of 42.5% and 45% are higher when Triton X-100 is added, the static stability is significantly better than for samples without surfactant. The highest coal loading for PRB slurry with acceptable viscosity for pumping is 42.5%.

Effects of Modified Sodium Lignosulfonate on Rheological Properties of Coal–Water Slurry with Low-Rank Coal

Coal–water slurry (CWS) is a new type of oil-replaceable liquid fuel with low pollution. The cost of CWS preparation will be greatly reduced if low-rank coal is used as the preparation material. In this work, chemical modification was used to prepare the modified sodium lignosulfonate (SL-M) hyper-dispersant, having larger molecular weight and more sulfonic groups than sodium lignosulfonate (SL), which was widely used for preparation of CWS from low-rank Shenhua coal due to its rich source and lower price. Effects of preparation conditions and molecular structure of SL-M on rheological properties of CWS were studied by using Haak rheometer. Results showed that the CWS transfered from viscous fluid to swelling fluid when the coal particle size decreased. The consistency coefficient of CWS decreased with the increase of additive dosage. The rheological properties of CWS became much better with the addition of the stabilizer, sodium carboxymethyl cellulose (CMC), compared with that of CWS without CMC. The prepared CWS changed from yield viscous fluid into yield swelling fluid with the increase of the molecular weight of SL-M. The rheological index was lower than 1 when the sulfonic group content was low, then it was increased with the increase of the sulfonic group content.

Synthesis, characterization and application of polycarboxylate additive for coal water slurry

Coal water slurry (CWS), a highly-loaded suspension of coal in water, is regarded as one of the most important alternatives for fuel oil. Generally, additives are required for the preparation of CWS, of which polycarboxylate (PC) is the most promising and applicable one. PC was synthesized by free radical polymerization of acrylic acid, acrylamide and macro-monomer, and was further characterized by FTIR and 1H NMR. The performance of PC as additives for CWS was evaluated and the dispersion mechanism was also studied. Results showed that the additive was a polymer with comblike branched chains modified by COOH and CONH2 groups. The CWS based on bituminous coal with PC additive displayed excellent fluidity and stability (i.e. the apparent viscosity and penetration ratio of CWS with 65wt% coal and 0.4wt% additive were 305mPa.s and 79.8%, respectively) for the most suitable coal type. The properties of the CWS can be further enhanced by using simultaneously PC and aliphatic additives because of the steric hindrance effect and electrostatic force.

Papermaking Waste Water Resource Recovery - A New Approach of Preparation of Coal Water Slurry

Papermaking waste liquid instead of water to prepare coal water slurry, which aim is turning waste into treasure. Not only can the waste fundamentally eliminate environment pollution, but also saving a lot of water resources. Because the waste contains large amounts of sodium, which is one of the main reasons of heating surface slagging of boiler. So it is necessary to improve and increase the soot blowing device of heating surface of boiler.

Study on the Effects of Coal Blending on the Slurry Ability of Shenmu Coals

Shenmu coals as low rank coal are difficult to prepare for Coal Water Slurry (CWS). The maximum slurry concentration of Shenmu CWS is lower than 60%, which is not available for practical application. Coal blending is a simple operation and low cost method to improve the slurry ability of low rank coal. Two different kinds of anthracite and bituminous coal samples were blended in Shenmu coal to study the effect on the preparation of CWS, respectively. The results showed that the maximum solid concentration of CWS increased as the proportion of high rank coal rise. And the viscosity of CWS is dropped at the same concentration. Different coals blending have different effects on the elevation of slurry ability for Shenmu coal. The raw coal with best slurry ability is not always the most suitable for blending in low rank coal. HuanNan bituminous coal is the best choice for blending in Shenmu coal. The maximum solid concentration of CWS can be increased by 6% when the proportion of HuanNan coal reached to 70%.

Stability of coal-water slurries made from ultrafinely divided coals of different metamorphic grades

The feasibility of mechanochemical preparation of coal-water slurries from coals of different metamorphic grades with the use of various chemical additives was examined. The effect of surfactants on the settling dynamics of particles in slurries at different particle sizes and different degrees of coal metamorphism was revealed as a result of the experiments.

Effect of Flotation on Preparation of Coal-Water Slurries

In order to study the effect of flotation reagents on the properties of coal-water slurry, a sub-bituminous coal was cleaned via either forward flotation or reverse flotation. The froth product from the forward flotation, obtained with the use of diesel oil and MIBC, and the tailings of the reverse flotation, carried out with dextrin-tannic acid depressants and dodecyltrimethylammonium chloride collector, were used in the preparation of coal-water slurries. It was shown that while it was possible to obtain the coal-water slurry with a high-solids content from the coal rendered hydrophilic (tailings from the coal reverse flotation), in the case of the hydrophobic product (froth product from the forward flotation) a dispersing agent was required to obtain the coal-water slurry of the same high-solids content.

Study on the stability of coal water slurry using dispersion-stability analyzer

Effect of modified lignin series and naphthalene series dispersants on the stability of coal water slurry (CWS) and sedimentation behavior of coal particles were investigated using Turbiscan Lab dispersion-stability analyzer. The results indicate that the sedimentation behavior of coal particles of CWS belongs to differential sedimentation and there is a conglobation between coal particles in CWS preparation. Stability of CWS prepared with lignin series dispersants is better than that prepared with naphthalene series, and the height and mean sedimentation rate of clarifying zone is about 68% of that of FDN when the dosage of additives is 1.0%. The Turbiscan Lab dispersion-stability analyzer can analyze the stability of CWS and also can be useful to investigate the stability mechanism 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.

Blended coals for improved coal water slurries

Three coal samples of different ranks were used to study the effect of coal blending on the preparation of Coal Water Slurry (CWS). The results show that by taking advantage of two kinds of coal, the coal concentration in slurry made from hard-to-pulp coal can be effectively improved and increased by 3%–5% generally. DLT coal (DaLiuTa coal mine) is very poor in slurryability and the stability and rheology of the resulting slurry are not very good. When the amount of easily slurried coal is more than 30%, all properties of the CWS improve and the CWS meets the requirements for use as fuel. Coalification, porosity, surface oxygenic functional groups, zeta potential and grindability have a great effect on the performance of blended coal CWS. This leads to some differences in performance between the slurry made from a single coal and slurry made from blended coal.

Evaluation of sulphonated acetone–formaldehyde (SAF) used in coal water slurries prepared from different coals

Abstract A new type of water-soluble polymer, sulphonated acetone–formaldehyde resin (SAF), was developed as dispersant for the preparation of highly-loaded coal water slurry (CWS). In this study, in order to evaluate the practical use in industry, the SAF and a naphthalene sulfonate formaldehyde condensate are used to prepare CWS using four Chinese coals with different coalification degrees. The evaluation of the properties of CWS shows that SAF has better ability in reducing CWS viscosity at lower dosage than naphthalene sulfonate formaldehyde condensate, and that the CWS prepared from SAF has excellent stability within 48 h and exhibits shear-thinning apparent viscosity/shear rate behavior at lower dosage. Based on the results, the SAF is an effective and promising dispersant for highly-loaded CWS.

High-performance dispersant of coal–water slurry synthesized from wheat straw alkali lignin

Environmental concerns have stimulated interest in utilizing plant-derived materials in various industrial fields. The main objective of the present study was to synthesize a new type of high-performance lignin series dispersant of coal–water slurry (CWS) from wheat straw alkali lignin (WAL), and determine the affecting factors in the reaction and the application performance for CWS preparation. The experimental results showed that the inherent viscosity and the sulfonic group content of the modified wheat straw alkali lignin (MSL) are the key factors affecting its dispersing effect for CWS. In the reaction, the reactant mass concentration and the sulfonating agent amount were changed to obtain the MSL with different inherent viscosities and sulfonic group contents, and the MSL with intermediate inherent viscosity (6.0 ml/g) and higher sulfonic group content (1.80 mmol g − 1 ) was found to have excellent dispersing effect for CWS. The MSL obtained from optimized process was used as dispersant for CWS preparation, the studies of the properties of CWS showed that MSL has similar dispersing effect with naphtalenesulfonate–formaldehyde condensate, and far better dispersing effect than lignosulphonate. Recently this kind of new dispersant has been applied in several power plants in China.

The effect of carboxymethyl cellulose (CMC) on the stability of coal-water slurries

In this study, the effect of carboxymethyl cellulose (CMC) used as stabilizer in the preparation of coal-water slurries on the stability has been investigated. Experiments have been carried out on the coal samples which differ in rank. Besides two different Turkish Lignites (Soma and İstanbul) also a bituminous coal (Thermal Code No. 434) of Turkish origin (Zonguldak) with medium volatile matter has been used. The results of the experiments showed that polymeric anionic CMC agent has much greater effect on the stability of CWS prepared from bituminous coal. Also, we found that inorganic mineral matters were able to be used as a stabilizer for preventing the sedimentation and separation of CWS.

00/01252 Manufacture and storage method for gelled coal slurries

The effects of ultrasonic irradiation on the properties of coal water slurry (CWS), such as apparent viscosity, rheological behavior and static stability, were investigated. The ultrasonic intensity was varied from 40 to 80 W cm−2 and irradiation time from 2 to 10 min. Ultrasonic irradiation distinctly improves both rheological behavior and static stability of CWS with a slight increase in the apparent viscosity of CWS containing 1% additive. The mechanisms having a remarkable improvement on the properties of CWS were proposed by measuring the changes of coal particle size distribution and dissolved ions in CWS before and after ultrasonic irradiation. The ultrasonic irradiation may provide a new technology for CWS preparation.

Study on the ultrasonic irradiation of coal water slurry

The effects of ultrasonic irradiation on the properties of coal water slurry (CWS), such as apparent viscosity, rheological behavior and static stability, were investigated. The ultrasonic intensity was varied from 40 to 80Wcm−2 and irradiation time from 2 to 10min. Ultrasonic irradiation distinctly improves both rheological behavior and static stability of CWS with a slight increase in the apparent viscosity of CWS containing 1% additive. The mechanisms having a remarkable improvement on the properties of CWS were proposed by measuring the changes of coal particle size distribution and dissolved ions in CWS before and after ultrasonic irradiation. The ultrasonic irradiation may provide a new technology for CWS preparation.

97/03481 Benefits of advanced coal cleaning in MCWS preparation

In micronized coal water slurry preparation the coal is pulverized to obtain the desired particle size distribution. The need for introducing a pre-cleaning stage prior to the final slurry formulation and the potential advantages and disadvantages of an integrated cleaning/size reduction process are discussed.

Kinetics of agglomerate growth in a continuous coal-oil purification process

A continuous coal-oil agglomeration process has been developed in a pilot plant for continuous coal purification prior to coal-water slurry preparation. The kinetics of agglomerate growth has been studied and a model has been adopted for the continuous process. This model is in a good accordance with the model proposed by Rao and Vanangamudi, for bath coal-oil agglomeration conditions. The size distribution of coal particles after agglomeration has been predicted using a characteristic curve, which utilizes the value of the feed top size of coal and the estimation of the mean size d sv (surface-volume) of agglomerates. It becomes also possible to quantify the coal recovery after passing agglomerates over a given sieve-bend. A description of agglomerate characteristics is then possible in terms of relationships giving the agglomerate mean diameter versus other characteristics of coal agglomerates, such as included moisture and rate of ash removal after separation process.

The role of dispersants in CWS agglomeration during combustion

This paper examines the possibility that the dispersants used in the preparation of coal-water slurries contribute to agglomeration during combustion. Particle size distribution measurements and SEM photographs were used to compare the agglomeration behaviour of subbituminous micronized coal-water slurries with and without dispersant. The measurements indicate that dispersants can provide a mechanism for binding agglomerates together.

Recent developments in stirred ball milling

In recent years the applicability of high-speed stirred ball mills has been extended to process coarser feedstock and to produce finer product particle size. This development has been made possible by design- and process-related innovations, like the invention of new agitating and media separating systems and a device for continuous grinding processes that avoids separate slurry preparation completely. Due to higher power density and better grinding efficiency high-speed stirred ball mills are an interesting alternative to conventional tumbling ball mills for fine-grinding in the mineral industry. As a typical example the grinding of coal for coal-water slurry preparation is discussed. Experimental results are given which prove the potential of stirred ball milling.