Multi-criteria comparative analysis of the pressure drop on coal gangue fly-ash slurry at different parts along an L-shaped pipeline

Disposing of coal gangue and fly-ash on the surface is a risky method with tremendous potential catastrophic consequences for the environment.Backfill mining is a promising practice for turning those hazardous wastes into functional backfill materi-als.Unfortunately,how to efficiently deliver the slurry to the desired places remains under-researched.To address this issue,the computational fluid dynamics software Fluent was used in the current study in addition to a laboratory rheological test to simulate the impact of various parameters on the evolution of pressure at a particular section of the pipeline.Furthermore,the response surface method was employed to investigate how the various components and their corresponding influencing weights interact to affect the pressure drop.This study demonstrates that the pressure drop of the slurry is highly influenced by slurry concentration,speed,and pipe diameter.While conveying speed is the main component in the bend section,pipe diameter takes over in the horizontal and vertical pipe sections.

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 3065 Pa/s, while the highest value of dry sludge is 1798 Pa/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.

Experimental research on Phanerochaete chrysosporium as coal microbial flocculant

The flocculation effect of the Phanerochaete chrysosporium on the coal slurry were studied by orthogonal experimental method in this study.The results of research show that the P.chrysosporium has a good effect on flocculating coal slurry.The optimum combination of the experimental is the P.chrysosporium,which is cultured in 2 days,mixed with 2 mL coagulant and 2 mL broth.The flocculant is a broken liquid with pH value of 6.The hightest flocculation ratio is 93.5%.The result of FTIR shows that the biological extraction of P.chrysosporium contains a lot of acidic polysaccharides that has the effect on flocculation.Microbial flocculant molecules and particles of coal slurry could be flocculated by‘‘absorption bridge’’.

Settling,consolidation and shear strength behaviour of coal tailings slurry

The volume change and shear strength behaviour of tailings slurry with the changes in gravimetric moisture content is important to effectively utilise the storage volume and analysis of dam failure potential.Consolidation testing of tailings from a slurry-like to soil-like state is a critical task,and conventional consolidation apparatus does not have the capability of doing such testing,as the tailings slurries contain high water content.Settling tests conducted on slurries having a 25%solids concentration showed very low efficiency;final sediment was still slurry-like.An intrinsic point was identified based on pore water pressure dissipation during consolidation tests in a slurry consolidometer that can define two states of the tailings i.e.slurry-like and soil-like.In the slurry-like state,the volume change was greater for Slurry 2 than Slurry 1,while the inverse was observed in the soil-like state.The evolution of peak vane shear strength with the changes in moisture content was almost similar for both samples and obeyed the power function.Regression models have been developed and validated to predict the shear strength of materials at any gravimetric moisture content or void ratio.

Discussion on Wear Mechanism of High Chrome Brick Used in Coal Slurry Gasifier

The microstructure and phase composition of high chrome brick used in coal slurry gasifier has been analyzed by means of SEM and Energy Spectrum. The results indicate that the used brick can be divided into different zones as slag-adhered zone, reaction zone, penetration zone and unaltered zone. The phase composition and microstructure are different and cracks occurred in different degree at these zones. A dense ring belt was formed with complex spinel (Mg,Fe)(Cr,Al,Fe 2O 4) in the reaction zone near the hot face. The wear mechanism of the brick during its employment has been discussed. It is considered that the reaction and penetration of coal slag and strong reductant bring about the composition change of the brick and destroys its original network inlayed structure and consequently result in its structure spalling and weakening strength, which is the main wear mechanism of the brick and followed by temperature fluctuation and high mechanical impact of flowing fluid with high-speed.

Main Influencing Factors on Service Life of High Chrome Refractories for Coal Water Slurry Gasifiers

The main characteristics of high chrome refractories for coal water slurry gasifiers were introduced. The damage mechanism of the refractories was analyzed by observing the microstructure of the used high chrome refractories with the aid of SEM. The main influencing factors on the service life of the refractories were summarized.

Aggregating structure in coal water slurry studied by eDLVO theory and fractal dimension

Coal water slurry gasification is a main source of hydrogen in the developing hydrogen economy.Moreover,biomass and waste can be added,making gasification process greener.To expand the application of coal water slurry and gasification process,it is necessary to understand the micro-structure in this large particle suspension system.In this paper,the micro-structure in coal water slurry was studied by extended DLVO(eDLVO)theory and fractal dimension,which is used to explain the mechanism of stability in large particle suspension systems.The interaction between two coal particles was characterized from the interparticle potential and energy barrier based on the eDLVO theory.The rheology and stability between different types of coals are measured and explained by the aggregating structure and fractal dimension in coal water slurry.The results indicated that there would be an aggregating structure in high rank coals,due to the interparticle potential caused by the surface properties,but probably not in low rank coals.This aggregating structure can be described and characterized by fractal dimension.The aggregation of particles is the source of the stability for high rank coals,as the close-packed 3D network structure in large particle suspension can support coal particles from settling down.The results have demonstrated that the combination of the eDLVO theory and rheological measurement is an effective way to investigate the stability of large particle suspension systems.

Systematic physicochemical characterization,carbon balance and cost of production analyses of activated carbons derived from(Co)-HTC of coal discards and sewage sludge for hydrogen storage applications

Hydrothermal carbonization(HTC)technologies for producing value-added carbonaceous material(hydrochar)from coal waste and sewage sludge(SS)waste might be a long-term recycling strategy for hydrogen storage applications,cutting disposal costs and solving waste disposal difficulties.In this study,hydrochars(HC)with high carbon content were produced using a combination of optimal HTC(HTC and Co-HTC)and chemical activation of coal tailings(CT),coal slurry(CS),and a mixture of coal discard and sewage sludge(CB).At 850℃and 800℃,respectively,with a KOH/HC ratio of 4:1 and a residence time of 135 min,activated carbons(ACs)with the highest Brunauer–Emmett–Teller specific surface(S_(BET))of 2299.25 m^(2)g^(−1)and 2243.57 m^(2)g^(−1)were obtained.The hydrogen adsorption capability of the produced ACs was further studied using gas adsorption isotherms at 77 K.At 35 bars,the values of hydrogen adsorbed onto AC-HCT(AC obtained from HTC of CT),AC-HCS(AC obtained from HTC of CS),and AC-HCB(AC obtained from HTC of the blending of coal discard(CD)and SS)were approximately 6.12%,6.8%,and 6.57%in weight,respectively.Furthermore,the cost of producing synthetic ACs for hydrogen storage is equivalent to the cost of commercial carbons.Furthermore,the high proportion of carbon retained(>70%)in ACs synthesized by HTC from CD and SS precursors should restrict their potential carbon emissions.

Monte Carlo Method and Its Variance Reduction Techniques for On-stream Coal Slurry Parameter Determination

The special purpose Monte Carlo program McMesh was used to study neutron transport in coal slurries for on stream determination of the slurry parameters. McMesh uses the mesh weight window method as the major variance reduction technique with other methods such as exponential transforms and correlated sampling included as options. There was good agreement between the calculated results from McMesh and from MCNP, a general Monte Carlo program, but McMesh was more efficient and more convenient.