Coal Mixture Research Articles

Process simulation of Chemical Looping Combustion using ASPEN plus for a mixture of biomass and coal with various oxygen carriers

Chemical Looping Combustion (CLC) is an emerging technology that has shown great promise for capture of almost pure CO2 in combustion of fossil fuels in power plants. In this paper, the CLC process is modeled in ASPEN Plus and then validated using experimental data from combustion of three types of biomass as fuel, and Hematite (Fe2O3) as an oxygen carrier (OC). Three types of biomass used in the simulation are pine sawdust, almond shells, and olive stones. The effect of the fuel reactor temperature on gas concentrations (namely CO2, CO, H2, and CH4) in the fuel reactor, and the carbon capture efficiency are examined. It is found that all three biomass types have very high carbon capture efficiencies, with pine sawdust and almond shell reaching nearly 100% capture efficiency when temperatures are greater than or equal to 950 °C, while olive stones reach a capture efficiency of nearly 100% at temperatures greater than 980 °C. It is also found that the CO2 concentrations in the fuel reactor vary across the three biomass types. The effect of using Mn2O3 as OC in place of Fe2O3 was also investigated. It was found that switching the oxygen carrier to Mn2O3 caused the concentrations of CO and H2 in the fuel reactor to decrease slightly, while the concentration of CO2 increased slightly. Additionally, a mixture of coal and biomass at 895 °C was used with each of the two oxygen carriers. The results show that the system using Fe2O3 had a greater power output than the one using Mn2O3, and that power output increased as the fraction of coal in the coal-biomass mixture increased.

Fast co-pyrolysis of a massive Naomaohu coal and cedar mixture using rapid infrared heating

Few studies on co-pyrolysis of a massive low-rank coal and biomass mixture with a high heating rate were conducted. This study adopted a novel infrared heating technique to minimize the secondary reactions process and further to explore the co-pyrolysis interactions of primary volatiles-volatiles from Naomaohu coal and cedar, based on co-pyrolysis products distribution, tar quality and compositions, char compositions at varied pyrolysis temperatures and blending ratios. The results show that infrared heating technique was successfully used to confirm the existence of synergies from primary volatiles of coal and biomass. The highest coal tar yield in the infrared-heated reactor with 1200 °C/min is 20.27 wt%, which is 1.54 times as the Gray-King assay. Higher cedar content can promote the generation of char and suppress the pyrolysis of NMH coal. At the pyrolysis temperature of 600 °C, light tar content in tar exhibited an increasing trend from 58.0 wt% to 75.5 wt% with the cedar content, and the best synergistic performance was obtained at 75% of cedar content. In addition, the significantly higher methyl-contained phenols and naphthalenes and lower CH4 revealed the fact that cedar can obviously act as hydrogen donor during co-pyrolysis process. The analysis of char compositions shows that the H has been transferred to gas and liquid products from solid char during co-pyrolysis, which can well interpret the improvement of tar quality.

Comparative study of the explosion pressure characteristics of micro- and nano-sized coal dust and methane\u2013coal dust mixtures in a pipe

Coal dust explosion accidents often cause substantial property damage and casualties and frequently involve nano-sized coal dust. In order to study the impact of nano-sized coal on coal dust and methane–coal dust explosions, a pipe test apparatus was used to analyze the explosion pressure characteristics of five types of micro-nano particle dusts (800 nm, 1200 nm, 45 μm, 60 μm, and 75 μm) at five concentrations (100 g/m3, 250 g/m3, 500 g/m3, 750 g/m3, and 1000 g/m3). The explosion pressure characteristics were closely related to the coal dust particle size and concentration. The maximum explosion pressure, maximum rate of pressure rise, and deflagration index for nano-sized coal dust were larger than for its micro-sized counterpart, indicating that a nano-sized coal dust explosion is more dangerous. The highest deflagration index Kst for coal dust was 13.97 MPa/(m·s), indicating weak explosibility. When 7% methane was added to the air, the maximum deflagration index Kst for methane–coal dust was 42.62 MPa/(m·s), indicating very strong explosibility. This indicates that adding methane to the coal dust mixture substantially increased the hazard grade.

Influence of Coal Gangue Volume Mixing Ratio on the System Contact Response When Multiple Coal Gangue Particles Impacting the Metal Plate and the Study of Coal Gangue Mixing Ratio Recognition Based on the Metal Plate Contact Response and the Multi-Information Fusion

In order to clearly grasp the influence rules of the coal gangue volume mixture ratio on the system contact response, and finally realize the coal gangue mixing ratio recognition according to the contact response differences, on the basis of the Hertz contact theory and Flores nonlinear spring-damping contact theory, this paper proposed and established the theoretical model when multiple coal gangue particles elastic impacting the metal plate for the first time simultaneously in an undisturbed way with the consideration of the particles micro-compression, the macro-deflection of the metal plate and the functional transformation of the system. To further study the system response, the simulation when multiple coal gangue particles with the variable mixing ratio impacting the metal plate was carried out with consideration of the coal gangue brittleness and the elastic-plastic of metal plate. Then, broken response of coal gangue particles and the contact response of the metal plate under the different coal gangue mixing ratios were studied. After that, EMD decomposition and time-frequency domain parameters calculation were conducted for the vibration acceleration signal of the metal plate, and the influence law of gangue mixing ratio on the vibration acceleration signal time-frequency domain parameters of the metal plate was obtained. Finally, in line accordance with the self-proposed data standardization processing method, Kalman filtering, multi-information fusion method as well as the simulation data, the recognition of coal gangue mixture ratio based on the vibration acceleration signal multi-time-frequency domain parameter fusion and the recognition of coal gangue mixture ratio based on the metal plate multi-response information fusion were marched respectively, and the coal gangue mixture ratio multi-dimension recognition strategy based on Kalman filter and the energy fusion is proposed. The research results show that the proposed recognition method can greatly improve the recognition rate and the applicability of the identification strategy.

Bloomery Production of Ferronickel Using High-Iron Oxidized Magnesia Nickel Ores

The reducing roasting of low-grade high-iron saprolite ores in the temperature range 1300–1350°C is studied to form nickel-rich ferronickel balls. The nickel-lean (1.01%) high-iron (24.3% Fe) nature-mixed ore of the Buruktal deposit is analyzed. The influence of the amounts of a solid reducer (mixture of brown coal and coke) and flux additives (limestone, quartz sand, bauxite, kaolin clay, fluorite) on the limitation of the reduction of iron oxides from a silicate slag and on the coarsening of metallic particles in roasting is investigated. When 18–21% kaolin clay and 2–4% limestone are added to a charge, the reduction of iron from a slag to a metallic phase is strongly limited. The introduction of 1% fluorite into a charge leads to a noticeable decrease in the melting temperature and the viscosity of an acid silicate slag and creates favorable conditions for the coarsening of metallic particles during reducing roasting of the charge in the temperature range 1300–1325°C. As a result, the optimum charge composition and roasting parameters are determined. At these composition and parameters, metallic ferronickel granules rapidly form, and a slag becomes almost fully free of fine metallic particles because of a high surface tension between the slag and metallic phases. The nickel content in metallic granules reaches 10–13% under these roasting conditions in the presence of an excess solid reducer.

Insights into the co-combustion of coal and biomass mixtures using a copper-based oxygen carrier in chemical looping combustion

Insights into the co-combustion of coal and biomass mixtures using a copper-based oxygen carrier in chemical looping combustion

Insights into the co-combustion of coal and biomass mixtures using a copper-based oxygen carrier in chemical looping combustion

Chemical looping with oxygen uncoupling (CLOU), variant to chemical looping combustion (CLC), is working on strategies to transport gaseous oxygen for fuel combustion. The present work reports the process simulation of CLOU of a coal-biomass mixture with CuO oxygen carrier. Variations in the different parameters are compared by replacing pure coal with an equal fraction of coal-biomass mixture. The presence of alkaline earth metals in biomass is seen to increase the coal char conversion in the fuel reactor. The predicted carbon capture efficiency is found to increase with the fuel reactor temperature range of 900 to 965°C irrespective of fuel used. The carbon capture efficiency was also varied with the solids flow rate varying from 3.48 to 13.64 kg/h. The thermal power output for the coal-biomass mixture is further compared with published literature for pure coal in context of its CLOU mode of operation. [Received: March 2, 2018; Accepted: November 26, 2018]

Proposals on establishing a methodology for the systematic analysis of energy coal mixtures in judicial practice

There are several situations in which it is necessary to clarify the types of coal that enter into the composition of mixtures: technical expertise and/or establishing the nature of some coal wastes, often from old stockpiles, in order to eliminate them. The proposed method is based on the identification and description of those mineralogical-petrographic and physico-chemical properties whose pursuit can lead to a diagnosis in differentiation of coal types. Systematic analysis involves in the first stage the identification of the different types of coal present in the sample by mineralogical analysis. From the sample subjected to mineralogical analysis, granules are extracted from the different types of coal present in the sample and the characteristics defining them are determined: moisture and hygroscopic moisture content, volatile matter content, fixed carbon content, agglutination characteristics, etc. Further, the characteristics of the mixtures are determined on another part of the sample and their structure is determined by algebraic methods.

Improving the Coke Property through Adding HPC Extracted from the Mixture of Low-Rank Coal and Biomass

To effectively utilize low-rank coal and biomass in the coking process, through the dissolution method, hypercoal (HPC) was produced, and its performance as an additional component in the coking process was also investigated. The cold strength of coke was tested using an I-type tumble tester and a universal testing machine; the carbon structure of the HPCs was examined via thermogravimetry (TG), X-ray diffraction (XRD), and Fourier transform infrared spectrometry (FT-IR) analyses. The results revealed that the thermoplastic properties of HPCs and the coke cold strength increased compared to raw coal. There is a positive linear relationship between the cold strength of coke and the order degree of the HPCs. As the biomass amount increased, the order degree of the HPCs greatly decreased, resulting in a decrease in the coke cold strength. When the amount of biomass was 20%, the caking index (G), drum strength, and compressive strength achieved maximum values of 95.21%, 83%, and 7.13 MPa, respectively. In addition, a caking mechanism of the HPCs is proposed.

Co-combustion of coal and carbonaceous wastes: thermogravimetric analysis

ABSTRACT The co-combustion characteristics of coal, two types of carbonaceous wastes (HDPE and scrap tire) and their blends were investigated in this study via a non-isothermal thermogravimetric method. The temperature indices and burnout index were used to evaluate the combustion performance of fuel. Strong synergistic effect emerged between carbonaceous wastes and coal, which showed the enhancement effect on devolatilization and the inhibition effect on char oxidation for the mixtures of coal and scrap tire while the opposite result for the mixtures of coal and HDPE. However, the addition of HDPE into coals can promote the release of volatile in advance. Moreover, the shape of TGA curves and the strength of the synergistic effect was different when carbonaceous wastes blending with different ranks of coal, which related to the combustion temperature zone and volatile content of coal.

Energy-size reduction of mixtures of anthracite and coking coal in Hardgrove mill

Aiming to maximize the utilization of coal resource, heterogeneous grinding of coal in various coalification degrees is common. Interaction among particles of different coals in mixture breakage results in changes of energy-size reduction characteristics if compared with that of single grinding. In this paper, anthracite and coking coals of low ash are ground together in a Hardgrove mill, and resistance to be broken is compared based on the classical breakage model. Product t10 of component after mixture breakage are determined by the relation between characteristic ratio (ratio of height and full width at half maximum of 002 peak) and yield of anthracite coal in mixture. Results indicate that product t10 of anthracite coal increases as more coking coal is added, and that of coking coal shows the contrary trend. A new method is proposed for the determination of energy split factors of components based on the assumption that the relation t10 and spilt energy of component still can be modelled by the classical breakage model. Besides energy split factors of components, breakage indictors are also determined according to above assumption and energy balance by genetic algorithm. Soft coking coal promote the energy-size reduction of hard anthracite coal in mixture breakage, with the increase of breakage indicator (A and b) and energy efficiency compared with those of single breakage. Energy split factors of anthracite coal is above one, and increases with the product fineness. And coking coal shows the contrary trend.

Parameters of strength and deformability of ash and slag mixture of Ekibastuz coals

The article assesses the possibility of using ash and slag mixture for the construction of a road bed. To this end, the traditional and modern methods of calculation of road surfaces are analyzed, which allow establishing the parameters of strength and deformability that require experimental determination. Experimental determination of strength and deformability parameters is performed by laboratory tests. For the implementation of tests the authors make samples of ash and slag mixture of different density. During the experiments, the metal stamp is pressed into the model and the experimental dependences of the sediment on the pressure are determined. This makes it possible to calculate the California Bearing Ratio, the deformation modulus, and to establish the pressures at which the mixture of ash and slag operates under compaction or shear conditions. Mathematical models are developed to calculate the parameters of strength and deformability from the value of pressure.

Transformation Characteristics of Hydrogen-Donor Solvent Tetralin in the Process of Direct Coal Liquefaction.

The aim of this study is to investigate the transformation of hydrogen-donor solvent tetralin in the direct liquefaction process of coal. Pure tetralin liquid as well as mixture of tetralin and Wucaiwan coal (WCW) were separately reacted under a liquefaction condition, and constituents of liquid product were analyzed by GC-MS. The results show that after the tetralin liquid reacts with high-pressure hydrogen, 90% of the reaction product is in liquid state, the gaseous products mainly include alkane gas and COx gas. When the reaction temperatures were set at 380 and 420°C, respectively, the corresponding transformation rates of tetralin can be 34.72 and 52.74%. At 380°C, the tetralin mainly plays a role of passing active hydrogen, while at 420°C, it mainly occurs dehydrogenation transformation to provide active hydrogen, as well as generate naphthalene, methyl indan, and substituted benzene, etc. Taking tetralin as the hydrogen-donor solvent, the WCW was performed liquefaction reaction, and the obtained results show that the transformation rates of tetralin are 69.76 and 83.86% at liquefaction temperatures of 380 and 420°C, respectively. Tetralin mainly occur to dehydrogenation transformation to generate naphthalene, followed by methyl indan, where contents order of main constituents of the liquefaction products were: naphthalene> tetralin > methyl indan.

Sustainability of Using Low-Rank Coal as Energy Source through The Upgrading Brown Coal (UBC) Process by Adding Waste Cooking Oil

The use of coal which is dominated by hard coal is projected as the main energy source (± 25%) in 2050 according to the Indonesian Government Regulation No. 79 of 2014. The use of low-rank coal as a substitute for hard coal through the Upgrading Brown Coal (UBC) process is supported by the Indonesian Government Regulation No. 77 of 2014 concerning the obligation to increase the added value of mining products. The use of UBC products can reduce the amount of coal consumption by up to 50% of the use of low-rank coal The UBC process is still being developed, as in this study, a mixture of low-rank coal and waste cooking oil is used as a coating material to cover the coal pores after the watering process. The variation in the mixing ratio of low-rank coal and waste cooking oil is 1:1; 1:2; and 1:3, with a variation of the heating temperature and mixing mixture of 100°C; 125°C; 150°C; 175°C; and 200°C. The analysis showed that the best conditions are found at a ratio of 1: 3 with a temperature of 175°C, wherein the results of the inherent moisture showed a decrease of 21.95% with a calorific value of 7462.82 cal/g. The high calorific value obtained was proven by the flame that occurred for 14 minutes for 50 g of the UBC product sample in the best variable with ash content of 2.92 %, and volatile matter by 64.77%.

The emissions from co-firing of biomass and torrefied biomass with coal in a chain-grate steam boiler

ABSTRACTIn this study, biomass of rice straw (RS) and wood (WD) and their torrefied biomass (RST and WDT) were used as solid biofuel (SBF) for co-firing individually with coal in a commercial continuous chain-grate steam boiler system, which was conducted at fixed input rate of heating value of mixture of SBF and coal and at fixed airflow rate. The effects of key system parameters on the gaseous and particulate pollutions and ash were examined. These include SBF type and blending ratio (RBL) of biomass (i.e., SBF) in the mixture of coal and biomass based on heating values for co-firing.The results indicated that wood, which possesses high heating value while less amount of ash, is more suitable for co-firing with coal than rice straw. Torrefaction can increase the heating value of biomass and homogenize its property, being beneficial to co-firing. Also, torrefaction can decompose the hydroxyl group of biomass, which makes biomass tending to possess hydrophobicity. This, in turn, helps the storage and transportation of biomass. Generally, adding the RS (with RBL = 5-10%), WD (2-15%), RST (2-10%) and WDT (2-20%), respectively, with coal decreases the emissions of NOx and SO2, but increases that of CO (except RST). The emission of HCl is little. The addition of biomass also increases the emission of fine particulate matters (PM) especially PM2.5 in the flue gases, raising PM2.5/PM100 from 34.87 to 78.35 wt.% (Case 50%WDT). These emissions for the Cases tested satisfy with Taiwanese emission standards of stationary sources which set limitations of NOx, SO2, CO and HCl < 350, 300, 2000 and 80 ppmv, while PM < 50 mg/m3, respectively. The results support the use of RS, WD, RST and WDT for co-firing with coal.Implications: This study examined the suitability of using solid bio-fuels to co-fire with coal in an industrial chain-grate steam boiler system with a capacity of 100 kW, in order to achieve carbon-free emissions. Both biomass and torrefied biomass of solid bio-fuel were tested. The findings would be useful for proper design and rational operation of solid bio-fuel/coal co-firing combustion matching the appeal of sustainable material management and circular economy of biomass, and of adaptation of global warming induced by greenhouse gases. It also provides information for policy-makers to promote the co-firing application of biomass and related bio-waste materials.

Non-isothermal gasification of biomass char and coal char mixture in CO2 condition

ABSTRACTNon-isothermal thermogravimetry method was used in the paper to investigate the gasification properties of biomass char (BC), coal char (CC), and their blended char at different mass ratios of 1:3, 1:1,3:1 under CO2. The results showed that with the increase of heating rate, the gasification curve moved to high-temperature zone and the peak rate of gasification increased, the gasification reactivity improved, and the gasification time reduced from 26.8 min to 6.78 min. Increasing BC share, the gasification rate also increased and the gasification time was shortened as the high specific surface area of BC had a great influence on gasification reactivity. The volumetric model (VM), the shrinking core model (SCM), and the random pore model (RPM) were applied to describe the reaction behavior of the chars and the results showed that all three models could describe the gasification process of char, while among them, RPM model achieved the best-fitting result. By RPM model, the activation energy of BC/CC at mass ratios of 0:4,1:3,1:1,3:1,4:0 was obtained, which were 240.74 kJ/mol, 129.16 kJ/mol, 108.54 kJ/mol,102.53 kJ/mol, and 97.01 kJ/mol, respectively. The decrease in activation energy with the increase of biomass char content could be ascribed to the higher specific surface area of BC and the lower carbon structure uniformity of BC.

PERBANDINGAN KUAT TEKAN MORTAR DENGAN MEMANFAATKAN COAL ASH WASTE

The utilization of coal ash waste (Fly ash) which is processed into raw material in making mortar, is expected to be useful in daily life, in addition to improve the economy of the community, can also reduce the impact of environmental pollution due to waste from coal ash (Fly ash). And provide information to the public about the effect of addition of coal ash (Fly ash) to the quality of mortar. From the results of this study it can be seen that the strength of mortar pressure without the mixture of coal ash or normal is 109.33 kg / cm, while for the average compressive strength of mortar mixed with coal ash is 9%, 12%, and 15% respectively, were 156 kg / cm2, 125.33 kg / cm2, and 110.6 kg / cm2. From the results of the study. it can be seen that mortar strength is highest if the variation of coal ash mixture is 9% of cement amount. While mixing more than 9% of mortar compressive strength will decrease. Thus the use of coal ash with a content of 9% is the optimum mixture content in this mixture. If a mixture of coal ash exceeds that level, it will decrease the strength of mortar. This decrease is thought to be due to the less strong bonds between aggregates (mixed materials) on the use of coal ash over 9%&#x0D;

Combustion reactivity of low rank coal by the mixture of candlenuts shell

Mixture of Low-Rank Coal (LRC) with Candlenuts Shell (CNS) has been carried-out to improve the quality of combustion. The quality of combustion is affected by combustion reactivity, thermal efficiency and combustion emission. This study investigated the effect of the mixture of CNS and LRC to find-out its combustion reactivity. An experimental study has been done to investigate the combustion reactivity of mixing LRC and CNS with the addition of CNS to LRC of 10%, 30%, 50%, 70% and 90% respectively. Testing methods including proximate and ultimate analysis following ASTM Standard and sample combustion in electric furnaces were applied with a combustion temperature of 500 °C, 625°C, 750 °C and 875°C respectively. Oxygen was used as an oxidizer in this experiment. The result of the experimental test shows that the addition of CNS into LRC generally increased its combustion reactivity. This fact indicates that adding CNS into LRC improves significantly the combustion quality of CNS and LRC mixture. The optimum addition of CNS into LRC to increase combustion reactivity is 10%.

Solids flow pattern in cold flow mockup of fluidized bed gasifier

We report solids flow pattern in a laboratory-scale fluidized bed of coal and ash mixtures. Suitable tracers were designed and deployed to determine the solids flow path of a typical particle through Radioactive Particle Tracking (RPT). Experiments were conducted in a cylindrical bed of 0.1 m in i.d. with two inventory compositions, namely, 70% Coal + 30% Bottom Ash (Composition I) and 20% Coal + 80% Bottom Ash (Composition II). Comparative analysis of RPT measurements yielded overall bed behavior, which was quantified in terms of time-averaged mean velocity, solids flux, RMS velocity, and kinetic energy per unit volume of the coal – bottom ash mixture. The mean axial velocity and solids flux profile indicated the influence of strong slugs on the solids flow patterns.

Study on Freeze-Thaw Damage Features of Coal Gangue-Fly Ash-Lime Mixture Based on Computed Tomography Scan

Considering the freeze-thaw damages of coal gangue-fly ash-lime (CG-FA-L) mixture road base, this paper applies the computed tomography (CT) scan to investigate the freeze-thaw damage features of the mixture. Several freeze-thaw tests were carried out to disclose the attenuation law of the frost-resistance coefficient of the mixture. The micro-defect propagation of the CG-FA-L was analyzed by comparing the gray level histograms of the CT images on each specimen before and after freeze-thaw cycles. The loss of cross-sectional area in each specimen was calculated quantitatively by image segmentation. The results show that the frost-resistance index attenuated linearly with the increase in the number of cycles; the defects induced by freeze-thaw cycles were mostly less than 15mm deep, and grew at an increasingly fast speed as the number of cycles surpassed 5; the micro-defect caused by freeze-thaw action mainly affected the depth between 15 and 35mm; under the freeze-thaw cycles, the micro-defects inside the mixture mostly appeared in the cementitious materials of the fly ash and lime; the CT technology was applied satisfactorily in the analysis on the freeze-thaw features of the CG-FA-L mixture