Low Quality Coal Research Articles

The performance and dispersing mechanism of anionic dispersants in slurries prepared by upgraded coal

It remains a significant subject on preparing high concentrated coal water slurry (CWS) from low quality coals to address the raw material supply for slurry preparation. The performance and dispersing mechanism of anionic dispersants in slurries prepared by upgraded coal, which was refined from a low quality coal, had been investigated systematically. The rheological behaviors of CWS prepared with each dispersant, i.e. sodium lignosulfonate (SLF), naphthalene sulfonate formaldehyde (NSF) and sodium polystyrene sulfonate (PSS), were studied at first; afterwards the governing factors on slurry concentration improvement and dispersion mechanism of coal particles modified by dispersant were investigated. The results illustrated that the maximum coal loading of CWS prepared with SLF, NSF and PSS were 67%, 70% and 68%, respectively, which suggested that the improvement of slurry concentration by each dispersant was NSF > PSS > SLF. According to the surface tension, yield stress and UV measurement, the effect of dispersants on slurry concentration improvement mainly relied on the adsorption by coal particles instead of surface tension reduction on solvent or its inherent steric hindrance. Subsequently, the contact angle and zeta potential analysis further indicated the excellent dispersing performance obtained by anionic dispersant was mainly attributed to the enhancement of zeta potential instead of wetting property on coal surface. The Derjaguin-Landau-Verwey-Overbeek (DLVO) calculations revealed that the electrostatic repulsion energy was improved significantly among coal particles after dispersant adsorption. A model on dispersion mechanism by anionic dispersants has been proposed. These results demonstrated that the promotion effect on slurry concentration by anionic dispersant in CWS was mainly attributed to enhancement on electrostatic repulsive force among upgraded coal particles.

Simultaneous measurements of urban and rural particles in Beijing – Part 2: Case studies of haze events and regional transport

Abstract. Two parallel field studies were conducted simultaneously at both urban and rural sites in Beijing from 1 to 29 November 2016. An online single-particle chemical composition analysis was used as a tracer system to investigate the impact of heating activities and the formation of haze events. Central heating elevated EC-Nit (elemental carbon-nitrate), EC-Nit-Sul (EC-nitrate-sulfate), and ECOC-Nit (ECOC: internal-mixed elemental carbon and organic carbon) levels by 1.5–2.0 times due to the increased use of coal in the urban areas. However, in the rural areas, residential heating, which mainly consumes low-quality coal, and biomass burning elevated ECOC-Nit-Sul, NaK-Nit, and OC-Sul levels by 1.2–1.5 times. Four severe haze events (hourly PM2.5 > 200 µg m−3) occurred at both sites during the studies. In each event, a pattern of transport and accumulation was found. In the first stage of the pattern, particles were regionally transported from the south and southwest and accumulated under air stagnation, creating significant secondary formation, then PM2.5 was elevated to 300 µg m−3. At both sites, the severe haze occurred due to different patterns of local emission, transport, and secondary processes. At Pinggu (PG), the sulfate-rich residential coal burning particles were dominant. The regional transport between PG and Peking University (PKU) was simulated using the Weather Research and Forecasting HYbrid Single-Particle Lagrangian Integrated Trajectory (WRF-HYSPLIT) model, confirming that the transport from PG to PKU was significant, but PKU to PG occurred occasionally. These cases can explain the serious air pollution in the urban areas of Beijing and the interaction between urban and rural areas. This study can provide references for enhancing our understanding of haze formation in Beijing.

SO2 and HCHO over the major cities of Kazakhstan from 2005 to 2016: influence of political, economic and industrial changes

Satellite observations of the Ozone Monitoring Instrument (OMI) for tropospheric sulfur dioxide (SO2) and formaldehyde (HCHO) column mass densities (CMD) are analyzed for the period 2005–2016 over the atmosphere of Kazakhstan. Regarding SO2 the major hot spots relate to regions with high population and large industrial facilities. Such an example is the city of Ekibastuz that hosts the biggest thermal power plants in the country and exhibits the higher SO2 CMD at national level. The annual average CMD in Ekibastuz reaches 2.5 × 10−5 kg/m2, whereas for the rest of the country respective values are 6 times lower. Other hotspots, mostly urban conglomerates such as Almaty and Nur-Sultan, experience high CMDs of SO2 in particular years, such as 2008. One of the main reasons for this behavior is the financial crisis of 2008, forcing the application of alternate heating sources based on cheap low-quality coal. Regarding HCHO, an oxygenated Volatile Organic Compound (VOC), the main hot spot is noticed over the city Atyrau, the oil capital of the country where two massive oil fields are located. The highest HCHO CMD (9 × 1015 molecules/cm2) appears in the summertime due to secondary production as a result of the photo-oxidation of VOCs emitted by industrial sectors, oil refinery plants and vehicles. Strongly elevated HCHO amounts are also observed in Nur-Sultan in 2012 that could be due to the residential coal combustion and vehicle exhaust under poor winter dispersion conditions. Significant reductions in HCHO observed between 2012 and 2015 can be attributed to two significant measures implemented in the country in 2013 that aimed at the improvement of air quality: the introduction of the emission trading system (ETS) for greenhouse gases and Euro-4 standards for new vehicles entering the national vehicle fleet.

STUDI EKSPERIMENTAL GASIFIKASI UPDRAFT SEKAM PADI DAN BATUBARA KUALITAS RENDAH BERKATALIS BENTONIT UNTUK PRODUKSI SYNGAS

This Research aims to determine the amounts generated in the gas liquefactiongas process rice husk with lowcoal quality at temperatures at 500 ° C and to know the speed of the updraft gasification process rice husk and the low coal quality of Bentonite catalyst. This research uses updraft type gasification where the gas that can be generated from the gasifer section will flow into the flowmeter and will be accommodated in the urine bag. In this study obtained syngas results on the process of updraft rice husk gasification and low quality coal berkatalis bentonit. Most Syngas produce on sample A SP 200 gr: BB 0 gr: B 100 gr equal to 36,72L. In sample B 180gr: 20gram: 100gr at 31,47L. In the sample C 140gr: 60gr: 100gr At 27.3L. and the lowest volume of syngas produced on the D sample 100gr: 100gr: 100gr at 24.28L. The heating rate that can be used in the gas filtration process and the low quality coal catalyzed bentonite is obtained at the highest heating rate in sample A 200gr: 0gr: 100gr at 16.89 ° C / min. In sample B 180gr: 20gr: 100gr at 15.25 ° C / min. In sample C 140gram: 60 grams: 100 grams of 13.13 ° C / min The lowest heating rate was obtained in D 100gr: 100gr: 100gr at 11.26 ° C / min.

Environmentally friendly thermal power plant based on the principle of a multi-product complex at vortex burning of the Berezovsky coal of the Kansko-Achinsk basin

According to the Energy Program of Russia until 2030, the formation of coal power is associated with large thermal power plants on low-grade coals and supercritical steam parameters. An increase in the proportion of low-quality coal leads to a sharp increase in toxic emissions in flue gases, liquid effluents and ash and slag waste. The article considers the scientific and technical bases and circuit solutions for the creation of environmentally friendly thermal power plants (EFTPP) on the Berezovsky coal of the Kansko-Achinsk Basin (KAB) with vortex combustion technology based on the principle of a multi-complex with the production of not only the main products (electric and thermal energy), but additional waste with consumer properties. Multi-product complex (MPC) is a series of road construction plants and agricultural enterprises, associated with the TPP and efficiently using wastes for construction, metallurgy and various agricultural products. The performed calculations and analysis of technical and economic indicators have shown that with the existing equipment, prices and tariffs for the products, the EFTPP will pay off more than two times during the life cycle. After 8 years from the beginning of construction the MPC starts generating profit.

Improved surface morphology by reforming of oxygen functional groups of Indian coal upon irradiating with microwave radiations

ABSTRACT The high-rank coal reserves are limited and getting depleted at an escalating rate to meet the demands of growing population. This concern has compelled the scientific community to use the young high ash coals. The coal water slurry fuel is one promising way to use low-quality coal as an economical liquid fuel. Due to poor physico-chemical and surface properties of such coals, these systems appear to be unsustainable. This research presents a sustainable solution to use the existing low-quality coals efficiently without any modification in the already installed systems. The Indian coal possessing high moisture and oxygen functional groups was successfully irradiated with microwaves, resulting in the improvement of morphological, physical, chemical and rheological characteristics. These changes are due to the elimination of the Hydroxyl (-OH−) and Carboxyl (-COOH−) groups, which are observed to contribute the most to the hydrophilicity of the coal particles. The morphological investigations reveal the breaking up of the bigger particles into fines upon microwave irradiation. The treated coals exhibit physico-chemical and surface properties similar to high-rank coals but still possess high ash that does not pose any issue with the normal operation of the system.

Optimization of staged combustion in a 600 MWe tangentially fired boiler with wall air injection

Low NOx combustion technology is used in coal-fired boilers to reduce the generation of NOx cost-effectively. However, this technology causes the problem of high temperature corrosion and slagging of water-cooled walls. In this study, a wall air injection technique is presented to effectively alleviate these problems, especially for the low quality coal. The wall air is injected vetically into the furnace to reduce the tangential circle diameter through the nozzles installed on the water wall. In a 600 MWe tangentially fired boiler, the wall air injection technique was retrofitted to study the influences of the wall air velocity and the tangential circle direction on the boiler combustion performance by simulation method. The applicability of the wall air injection technique for the combustion of the design coal and the low quality coal was also studied. The results showed that the wall air velocity of ~ 40 m/s was optimum for the combustion of the low quality coal. The following improvements in the combustion performance were observed at the wall air velocity of 40 m/s: 1) the actual tangential circle diameter was close to the design value of 14 m; 2) the mean flue gas temperature on the water wall decreased by about 600 K while that in the furnace center increased by about 80 K at most; 3) the mean CO mole fraction reduced by about 0.03; and 4) the NOx generation reduced by 38 mg/Nm3. When the wall air injection direction was clockwise, the NOx generation at furnace outlet decreased by 6 mg/Nm3.

Laboratory-Scale Tests for the Utilization of High Ash Non-Coking coal in Coke-Making Process

India has vast coal resources all over the country; however, the presence of high ash content makes them invulnerable for industrial usage. To compensate for the rapid depletion of high-quality coking coals and to compensate for the demand for coal in iron and steel sectors, coal cleaning or beneficiation and blending techniques have come into limelight for the usage of low-quality coal. In this paper, laboratory-scale experiments were performed on the utilization of Indian high ash non-coking coal (NCC) and imported semi-coking coal (SCC) for the coke preparation. At first, washability characteristics of Indian high ash coal were investigated by using jigging, spiral concentration, and sink and float density separation methods. The optimum cut-off density NCC and SCC coals were blended and sent for the caking properties analysis. Proximate and ultimate analysis, vitrinite reflectance, crucible swelling number, and caking index or roga index have been taken as the measure for the caking ability of coal blends.

Characterization of bio-coal briquettes blended from low quality coal and biomass waste treated by Garant\xae bio-activator and its application for fuel combustion

Experimental research was carried out on the manufacturing of bio-coal briquettes from a blend of two different types of low-quality coal and biomass waste in the absence of coal carbonization, where the third blend of the material was fermented by adding a bio-activator solution before pressurizing the components into briquettes. The coal samples from Caringin–Garut Regency (BB–Garut) had a low calorific value and a high sulfur content (6.57 wt%), whereas the coal samples from Bayah–Lebak Regency (BB–Bayah) had a higher calorific value and a lower sulfur content (0.51 wt%). The biomass added to the coal blend is in the form of fermented cow dung (Bio–Kohe), and it had a calorific value of 4192 kcal/kg and a total sulfur content of 1.56 wt%. The main objective of this study is to determine the total decrease in the sulfur content in a blend of coal and biomass in which a fermentation process was carried out using a bio-activator for 24 h. The used bio-activator was made from Garant® (1:40) + molasses 1 wt%/vol, and its used amount was 0.2 L/kg. Also, the total sulfur content in the blend was 1.00 wt%–1.14 wt%, which fulfills the necessary quality requirements for non-carbonized bio-coal briquettes. The pyritic and sulfate content in the raw coal was dominant, and the organic sulfur, when fermented with Garant®, was found to be less in the produced bio-coal briquettes by 38%–58%.

Efforts to control air pollution in the Asia-Pacific region.

Efforts to control air pollution in the Asia-Pacific region.

Changes in Soil Physicochemical Properties and Maize Production Following Improvement of Salt-Affected Soils Using Coal Bio-Briquette Ash in Northeast China

Soil degradation due to salinity and sodicity is one of the most important impediments to agricultural production. Coal bio-briquettes (CBB) made from coal, biomass, and desulfurizers have been proposed for use in desulfurization and usage of sustainable energy for coal and biomass in China. CBB ash contains calcium compounds such as calcium sulfate, calcium carbonate, and fly ash. The potential improvement of salt-affected soils using ashes from CBB made from two low-quality coals and/or organic manure (OM) was investigated in northeast China. The CBB ash application rates were 0 kg/m2 (control), 1.16 kg/m2, 2.32 kg/m2, 4.64 kg/m2, and 6.96 kg/m2. Following the application of CBB ash and/or co-application of OM, maize production increased significantly, compared to control plots. Moreover, co-application with OM resulted in higher maize production than application of CBB ash only. Soil pH, sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP), and Na+, HCO3−, and CO32− concentrations decreased, and Ca2+, Mg2+, and SO42− concentrations increased from the start of the experiment to harvesting time. Maize production showed a tendency to increase with increasing CBB ash/OM application rates. The decrease in pH, ESP, and HCO3−, and increase in Ca2+ in the application plots over time was particularly remarkable. Moreover, saturated hydraulic conductivity (Ks) after CBB ash application in the slightly and moderately salt-affected soils increased with increasing application rates. In case of the highest application rate (6.96 kg/m2), using ash from CBB made from lower quality coal, pH and ESP decreased from 9.47 to 7.61, and from 7.0% to 0.98%, respectively, and Ks increased drastically by three orders of magnitude. Therefore, not only soil chemical properties, but also Ks, were improved in salt-affected soils using CBB ash. In addition, the heavy metal content in CBB ashes was below the standard values according to Chinese guidelines. Taken together, these results demonstrate the feasibility of sustainable methods for energy usage and environmental application in China.

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.

Development of a roof-to-floor convergence index for longwall face using combined finite element modelling and statistical approach

Immediate roof of a longwall panel in India is composed of mostly low quality coal and shale and as a result, several roof fall incidents have occurred in between canopy tip and the face causing delay in production. The mine has several longwall panels and it is expected that similar conditions may prevail in all the panels. Roof-to-floor convergence at the face, shield leg pressure and abutment load in chain pillar are monitored to evaluate the stability of longwall face in terms of displacement as well as stresses. In view of that, a study is conducted to understand the deformation behaviour of roof-to-floor convergence and development of pressure in hydraulic legs after the web cut considering different combinations of main roof thickness, its overhung length behind the shield, and material type and setting load. This paper describes a methodology for estimation of roof-to-floor convergence using 3D finite element models before and after web cut. A statistical procedure is also enumerated for development of a unique roof-to-floor convergence index combining input parameters. For this purpose, a total of 216 3D finite element models are analysed considering Drucker-Prager material nonlinearity and having two legged powered support of 2 × 1152 tonne capacity surrounded by coal, rock mass and goaf. This study also compares the roof-to-floor convergence measured in the field to those estimated using the proposed convergence index.

Analysis of the efficiency of a solid fuel boiler depending on the choice of combusted fuel

In the municipal and residential sector in Poland, as many as 50% of households are heated by solid fuel boilers. Most often these are, unfortunately, inefficient boilers, fired with low-quality coal. This study characterizes the market of boilers for solid fuels in Poland, and also presents the main apportionment of these devices, due to the different criteria that characterize them. The current legal changes in the scope of energy and emission requirements for solid fuel boilers are also discussed. The main purpose of this work is to analyze the real efficiency of the solid fuel over-fired boiler used, depending on the fuel burned in it. The process of burning selected fuels (seasoned wood, coal and pea coal) in the boiler was preceded by tests of these fuels to determine their energy parameters, such as moisture, ash content, the share of volatile matter and calorific value. In the next step, the energy efficiency obtained by the tested solid fuel boiler during the combustion of selected solid fuels was compared. The highest efficiency was achieved during the combustion of pea coal, and the lowest was achieved during the combustion of wood. In any case, the nominal efficiency value was achieved. Solutions that could improve the quality of the combustion process in this type of boiler were proposed.

The co-combustion performance and reaction kinetics of refuse derived fuels with South African high ash coal

This research focuses on the co-firing of low-quality coal with refuse derived fuel (RDF) as a means to reduce the volume of waste dumped in landfill sites. The co-combustion behaviour and kinetics of various RDF/coal blends at different weight ratios, along with their physicochemical characteristics were investigated. The physicochemical analysis revealed that the run-of-mine and discard coal have relatively low calorific values of 21.7 MJ/kg and 16.7 MJ/kg, respectively. The RDF samples, plastic blend (31.2 MJ/kg) and paper blend (22.4 MJ/kg), were found to have higher energy contents. The thermogravimetric analysis was performed in an atmosphere of air, over a temperature range of 25–850 °C, and the results showed that the RDF samples had lower ignition, devolatilisation, and burnout temperatures compared to the coals. The ignition temperatures for the blended fuel occurs in the lower temperature region when RDF is added to the blend, likewise the peak temperatures and burnout temperature shifted to a lower temperature zone. The activation energies (Ea) were determined using the Coats-Redfern method. The Ea for the run-of-mine (ROM) coal of 104.4 kJ/mol, was found to reduce to 31.4 kJ/mol for the 75% PB + 25% ROM coal blend and 35 kJ/mol for the 75% PL + 25% ROM coal blend, respectively. The discard coal which had an Ea of 109.9 kJ/mol was reduced to 30.9 kJ/mol for the 75% PB + 25% discard blend, and 33.5 kJ/mol for the 75% PL + 25% discard coal blend. It was determined that the most favourable blend for co-combustion was 70% discard coal + 30% PL RDF due to the similarity of the combustion profile to that of 100% coal and the simultaneous reduction in apparent activation energy.

Lignite flotation in inorganic salt solutions

ABSTRACT The flotation of low-quality lignite coal in the presence of NaCl, MgCl2 and CaCl2 inorganic salts with/without the use of kerosene and MIBC as flotation chemicals was investigated in this study. In addition, the zeta potential and contact angle measurements were performed. The lignite sample exhibited a negative surface charge over a broad pH range and had no isoelectric point (iep). It was determined that the magnitude of negative charge significantly decreased above 10−2 M concentration of the salts and the flotation of lignite without flotation reagents also started to take place at concentrations higher than the same value. The contact angles measured on the lignite surfaces also increased with increasing salt concentration. The lignite sample was hydrophilic, and therefore very difficult to float. Consequently, the flotation of lignite with collector and frother was not achieved to the desired extent, even using high reagent concentrations. In the absence of flotation chemicals, high concentrations of these salts also provided low flotation performances. However, the flotation of lignite could be achieved with kerosene and MIBC in the presence of inorganic salts. In addition, it was determined that MgCl2 and CaCl2 salts were more effective on the lignite flotation than NaCl salt.

Ultimate and Proximate Analysis of Coal Samples from Different Regions in Pakistan for their Future Utilization

A comparison of coal samples obtained from various regions of Pakistan was done based on their proximate and ultimate analysis and gross calorific values to discern the processing technique which may be applied for these coals e.g. liquefaction, gasification, carbonization etc. The samples of coal were got from different coal fields in Pakistan. Different nomenclature were chosen to differentiate the regions of coal e.g., SRGE for coal obtained from Sor-Range and Degari coalfields near Quetta, Baluchistan, LKR for coal obtained from Lakhra, Sindh, SLGE for coal obtained from Salt Range coalfields near Chakwal, Punjab, KTL for coal obtained from Kotli, Azad Jammu Kashmir (AJK), MCH for coal obtained from Mach, Baluchistan and THR for coal sample obtained from Tharparkar, Sindh. MCH coals were reported with highest calorific value of 13305.35kcal/kg. THR coals were classified as class (2) coals as they were found with calorific values & carbon contents of 12337.13 kcal/kg and 69.9% respectively. KTL coal samples were reported with lowest carbon contents of 57.9% in ultimate analysis experiments. MCH & SRG coals were nominated as low quality coals because of their highest ash contents i.e., 50%. SRGE and SLG coals were found hazardous for our ecosystem because of their high sulfur contents. SRGE, LKR, SLG and THR were classified as class (2) bituminous coals and were found best gas coals, while MCH and KTL were found class (1) and class (4) bituminous coals respectively.

Data‐driven control for combustion process of circulating fluidised bed boiler

Owing to the advantages of burning low-quality coal (coal slime and coal gangue), furnace desulfurisation, low N O x emission and deep load adjustment, the circulating fluidised bed (CFB) combustion technology becomes one of the few fossil fuel utilisation technologies funded continuously by the Chinese government. However, compared with the pulverised coal boiler, the combustion process of CFB boiler is more complicated because of the larger time delay, significant uncertainty and more coupled variables. In this study, a data-driven proportional–integral-derivative (DD-PID) control strategy is presented for the combustion control of CFB boiler to improve the operating performance under full operating conditions. By analysing the running mechanism of combustion process, an inverse decoupler is introduced to transfer the combustion object to the generalised controlled object, which has relatively independent input–output relationship. After that, a normative procedure of DD-PID, including PID-parameter database establishment, information-vector neighbourhood selection, active PID-parameter determination, database update, and redundant vector deletion, is given. Finally, a series of case study, including numerical tests applied to the proposed combustion model and application test employed on 330 MW CFB simulation platform proves the feasibility of DD-PID control strategy.

A study of coal upgrading in briquette making based on briquette characteristics using heated mechanical metods

Indonesia has low quality coal reserves which are quite abundant. The low quality of coal is due to the inherent water content that is still quite high. Therefore, an upgrading process is needed. The upgrading process is intended to increase the calorific value of coal. The upgrading process can be applied to the process of coal briquettemaking. Generally, the manufacturing of low quality coal briquettes uses mechanical and heating methods in two different processes. In this study, the manufacturing of the briquettes uses the tools in a series of processes. The working principle of this tool is based on the strength of pressure and heating temperature. The maximum pressure is 900 psi, and the maximum heating temperature is 150°C. One of the important factors that determines the success of the upgrading process is the magnitude of heating temperature. The variations of heating temperature used are 50°C, 75°C, 100°C, 125°C, 150°C. The heating temperature affects the characteristics of coal briquettes produced. The heating temperature that produces the best quality coal briquettes is 150°C. The results of analysis of the coal briquette’s composition are as follows: the inherent water content is 11.00%, the volatile substance level is 46.48%, the ash content is 6.13%, the fixed carbon value is 36.39, and the calorific value is 5.235cal / gr.

Production of High-Strength Coke from Low-Quality Coals Chemically Modified with Thermoplastic Components

Production of High-Strength Coke from Low-Quality Coals Chemically Modified with Thermoplastic Components