Desulphurization Of Coal Research Articles

Sequential Chemical and Biological Desulphurization of High Sulfur Containing Pakistani Coal

Coal is a rich and affordable source of energy that is extensively used for different industrial purposes. However, its extensive utilization have caused a number of environmental problems. Especially, the release of different oxides of sulfur during combustion have resulted in the ongoing acid rain and global warming issues. To tackle the issue, sequential chemical and biological technologies were applied for the desulfurization of a coal sample, collected from Shahrag coal mines, in Baluchistan, Pakistan. The coal was initially de-pyritized with a 15% nitric acid (HNO3) solution. The chemically treated coal was subsequently biodesulfurized with iron oxide (Fe3O4) coated bacterial consortium IQMJ-5. The de-pyritized and biodesulfurized coal was analyzed with proximate, ultimate, FTIR, XRD, and EDX analysis. The calorific value was determined through an oxygen bomb analyzer. Following desulfurization, about 61% organic sulfur and 86.57% total sulfur were removed from the coal sample. Similarly, an increase of about 93 kcal/kg in the calorific value was detected after the treatment. These results clearly depicts the potentiality of the technology for the desulfurization of fossil fuels at the industrial scale.

Ultrasound-assisted oxidative desulphurization of coal using choline chloride-based deep eutectic solvents

Ultrasound-assisted oxidative desulphurization of coal using choline chloride-based deep eutectic solvents

Desulfurization of coal using SnO2/TiO2 nanocomposite immobilized on glass beads under solar light irradiation

Abstract Coal is one of the important sources of energies and its combustion produce sulfur dioxide in the atmosphere, which needs desulphurization to avoids the pollution issue. Coal desulfurization was performed using SnO2/TiO2 nanocomposite under solar light irradiation. The SnO2/TiO2 was synthesized by co-precipitation method and deposited on glass beads. The prepared SnO2/TiO2 was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transfer infrared spectroscopy (FT-IR) techniques. The SnO2/TiO2 nanocomposite desulfurization efficiency was performed under solar light irradiation and process variables, i.e., irradiation time, H2O2 and pH were optimized for maximum desulfurization of coal. The SnO2/TiO2 nanocomposite showed promising efficiency and 60 % sulfur removal was achieved under optimum conditions. Based on efficiency, the SnO2/TiO2 nanocomposite has potential for the desulphurization of coal under solar light exposure, which will make the process highly economical feasible.

Alkali leaching in dissolved oxygen for efficient desulphurization of low-grade Lakhra coal

ABSTRACT Coal is still a great source of energy, but its high sulfur content causes environmental pollution and problems in its processing. This study used a method of combined oxidation and alkali leaching to desulfurize low-grade, high-sulfur Lakhra coal at different ranges of temperature, alkali concentration, leaching time, partial pressure of oxygen, and agitation speed. The optimum values for the leaching reaction were observed to be an alkali (NaOH) concentration of 0.8 mM, a leaching time of 1.5 h, an oxygen partial pressure of 150 psi, and an agitation speed of 800 rpm. The ash content of the coal initially increased at higher values of reaction time and temperature, and then became saturated at a certain peak. The raw coal was characterized for ultimate and proximate analysis, and the product was characterized for ash content and total sulfur content.

Microwave-assisted desulphurization of coal in alkaline medium and conditions optimization by response surface methodology

Abstract The coal is an imperative source of energy, which on combustion, it emits sulphur dioxide, which cause air pollution. In the present study, microwave mediated desulphurization of coal was investigated and input variables were optimized by response surface methodology (RSM). The proximate analysis and ultimate analysis report indicate the sample belongs to subbituminous having sulphur (6.96%), volatile matter (34.5%) and calorific value (5099 kcal/kg). Under microwave irradiation, up to 68% of sulphur was leached in alkaline medium. The particle size of coal, concentration of potassium hydroxide (KOH), microwave exposure time and power of microwave radiation were systematically optimized for maximum desulphurization of the coal. Under optimum conditions of the process variables, 63.06% desulphurization of coal was achieved. The optimum levels of process variables are as, particle size 500 µm, irradiation time 8.54 min, radiation power 720 W and concentration of KOH 15% (w/v). Findings revealed that the microwave-assisted desulphurization under alkaline condition furnished promising efficiency, which can be employed for the desulphurization of coal.

Study on deashing and desulphurization of coal with heavy medium in enhanced gravity field

ABSTRACT This study carried out component sulfur composition analysis, electron probe microscopic analysis, and particle size and density composition analysis of coal samples from a coal preparation plant in Liupanshui. The influence of various factors on the indexes of clean coal products under different separation medium conditions by enhanced gravity separation technology, including water medium (WM), magnet powder suspension (MPS), and zinc chloride solution (ZCS), is discussed. The results show that the addition of MPS or ZCS has an obvious improvement on coal deashing and desulfurization compared with the WM separation, especially the separation effect of ZCS, which is better than that of MPS because of better uniformity and stability of ZCS. The addition of MPS or ZCS can help the materials stratify strictly according to the density to enhance the sorting function. The clean coal ash and sulfur content are reduced to 13.24% and 2.51%, while the combustible recovery and desulfurization efficiency are up to 71.46% and 49.27%, respectively, under the optimal condition.

Development of rapid CO2 utilizing microbial ecosystem onto the novel & porous FPUF@nZVI@TAC@ASP hybrid for green coal desulphurization

• Coal desulphurization with high CO 2 consumption by bacteria on a hybrid was studied. • FPUF@nZVI@TAC@ASP offered immobilization platform to grow desulphurization bacteria. • nZVI coating enhanced coal desulphurization by breaking C-S bond & iron recycling. • S (43.3), Fe (20), NH 4 (0.08), NO 3 (0.05), PO 4 (0.01) kg/m 3 /day removal witnessed. • 4500 ppm of CO 2 was consumed to remove 1 kg sulphur, makes this study impactful. Self-capturing carbon dioxide (CO 2 ) from the polluted atmosphere and consuming it into the coal reactor for cheap coal desulphurization is an ideal solution to smog and global warming. Herein, a novel engineered microbial ecosystem was developed over zero-valent iron (nZVI) decorated functional polyurethane (FPUF) biocarrier for coal bio-desulphurization coupled with rapid utilization of CO 2 . FPUF was structured with nZVI for quenching sulphur, iron, and nitrogen species from coal, and present them to TAC/ASP microbes for rapid degradation. Self-assembled and rapid CO 2 utilizing microbial ecosystem (FPUF@nZVI@TAC@ASP) was shortly emerged as rapid coal treatment device as it removed CO 2 (54 kg/m 3 /day), sulphur (43.3 kg/m 3 /day), iron (20 kg/m 3 /day), NH 4 + (0.08 kg/m 3 /day), NO 3 – (0.05 kg/m 3 /day), and PO 4 3- (0.01 kg/m 3 /day). Super-high CO 2 fixation along with high sulphur removal rate (43.3 kg/m 3 /day) also yielded 400 mol/h/g protein. That further provided ample supply of HCO 3 – , S 2 O 3 2- and SO 4 2- species to microbes, which ultimately resulted in highly dense microbial ecosystem (14 g/L/h). Highest coal treatment efficiency (90%) was recorded, at sulphur/CO 2 ratio of 20 and 14-h residence time, which was 30 times better performance than previously reported studies. Practical and commercialized application of developed process (tested in 5-liter coal-reactor), was found very impressive, as treatment of 1 kg coal produced 180 g of sulphur and mitigated 4500 ppm of CO 2. The developed process has potential direct industrial application for coal, crude oil, petroleum, flue gas and natural gas desulphurization. This study opens a new gateway for the investigation and design of more innovative desulphurization and CO 2 mitigation researches.

EFFECT OF BIOMASS BLENDING AND DESULPHURIZATION ON FLUE GAS EMISSIONS OF NIGERIAN SUB BITUMINOUS COAL BRIQUETTES

The effect of blending, briquetting and desulphurization of coal and biocoal briquettes of Nigerian sub bituminous coal is discussed. The flue gas of the coal and biocoal samples were analyzed to study the emission characteristics of nitrogen oxide (NO2), sulphur dioxide (SO2) and carbon monoxide (CO) due to environment concern with the use of coal as either domestic or industrial fuel. Sub bituminous coal sample from eight coal mines and sites in five states in Nigeria were collected. The states and sites included Kogi (Ogboyoga, Okaba), Benue(Owukpa),Nassarawa (Lafia/Obi), Ebonyi (Afikpo) and Enugu (Okpara,Onyeama and Ezinmo).The samples were pulverized and blended with sawdust at various constituent ratios of 0:100, 10:90, 20:80, 30:70, 40:60, 50:50 and 100:0 sawdust : coal. Cassava starch was used as binding material while calcium hydroxide was used as desulphurizing agent for the briquettes. Emission tests for various compositions of the briquettes were carried out and the O2, CO2, CO, NO2 and SO2 of the briquettes were compared. Results showed reduction in combustion emission with increase in sawdust concentration with the reduction in smoke and noxious gas emission. The sulphur dioxide range of the coal briquettes is between 0.018ppm and 0.028ppm which decreased to between 0.025and 0.005 ppm in biocoal briquettes. Same for nitrogen oxide which range between 0.034ppm and 0.038ppm but decreased to between 0.025 and 0.019 ppm and carbon monoxide range of between 0.3ppm and 0.48ppm which decreased to between 0.43ppm and 0.12 ppm in the biocoal briquettes. The 50:50 blends of sawdust to coal for Ogboyaga has the lowest carbon monoxide emission of 0.12 ppm; Okpara has the lowest sulphur dioxide emission of 0.005ppm while Onyeama has the lowest nitrogen oxide emission of 0.019 ppm. These are below the national ambient air quality standards which put sulphur dioxide at 1.4 x 10-1 ppm. The biocoal briquette emits less sulphur dioxide because it contains desulphurizing agent which fixes some of the sulphur that would have gone to the atmosphere to ash. Keywords: biocoal briquettes, blending, flue gas emissions, sub - bituminous coal.

A novel computational simulation approach to study biofilm significance in a packed-bed biooxidation reactor

Fe (II) biooxidation has recently gained significant interest. It plays a key role in a number of environmental and industrial processes such as bioleaching, acid mine drainage treatment, desulphurization of sour gases, and coal desulphurization. In this work, a three-dimensional CFD model for gas-liquid flow in a lab-scale packed-bed biooxidation reactor is used. The reactor is randomly packed with spherical particles, and the particles are covered with Leptospirillum ferrooxidans biofilm for Fe (II) biooxidation. A modified Jodrey-Tory algorithm is used to generate random packing with actual porosity of 0.42, and biofilm layer with constant thickness is considered over the particles. A simplified Eulerian–Eulerian model is used to obtain detailed flow field. The concentration profile in the reactor and the conversion of Fe (II) from the present simulations are obtained and validated using experimental data reported in the literature. The results of the study indicate that about three-quarters of the conversion occurs in the upper half of the reactor and Fe (II) concentration on the biofilm surface at the lower quarter of the reactor does not exceed 5 mM (The inlet concentration is 89.6 mM). The findings reveal that rate-limiting phenomena may vary in different parts of the reactor. The results obtained through the simulations represent advantages for the design and optimization of packed-bed biofilm reactors.

Modelling performance evaluation of microbial desulphurization of Waterberg steam coal in CSTR

The first part of this study used microbial desulphurization process as a pre-combustion technique for sulphur content reduction in Waterberg steam coal. This is simulated at the laboratory scale where Continuously Stirred Tank Reactor (CSTR) acts as a biological reaction chamber. Experimental tests were performed by varying coal particle size distribution of -0.85 mm, +1.00 mm, +2.30 mm and 4.60 mm in order to determine the influence and optimum condition for desulphurization process. The second part of this study deals with developing a model based on reaction kinetics, simulate microbial desulphurization process in CSTR system and validate the model under various experimental conditions. Kinetics study and parameter estimations were evaluated and optimized using the Simulation Programme for Aquatic Systems (AQUASIM) 2.0 Software. The average kinetic parameters in the bioreactor were determined for both without inhibition: kd = 1.65 x 10-3 (h-1), Ks = 1.23 x 10-4 mgL-1, X0 = 523 mgL-1 and ?2 = 0.524 and with inhibition, KI = 371 mgL-1 for finer coal particle size. Equally important, these kinetic parameters were determined by means of optimization. Consideration should be given that the developed model may be applied to only wider range of sulphur content range studied.

Formation of Incrustations during the Cocombustion of Biomass in Fluidised Bed Boilers

In this article, we focus on causes of formation of incrustations in fluidised bed boilers that result from combustion of biomass-containing energy-producing raw materials and can significantly limit the efficiency of the respective power equipment operation. We applied laboratory procedures followed for assessment of characteristic eutectics of mixtures of coal ashes, desulphurisation components (dolomite and limestone), and woodchip ashes. Our analysis proved that combustion of these (or similar) raw materials, accompanied by repeated heating and cooling of combustion and flue gas desulphurisation products, leads to the formation of unfavourable incrustations. These incrustations can grow up to several tens of centimetres in size, thereby significantly restricting the power equipment functionality. They arise due to incrust reheating that results in the formation of eutectics, which have lower melting temperatures than that during their first pass through the combustion process. The same holds for desulphuriation components themselves. Formation of these new eutectics can be attributed both to recycling of substances produced during the first pass through the furnace as well as to mixtures formed both from recycled materials and from components initially combusted in the boiler furnace.

Desulphurization of coals of different ranks in the presence of slimes by reverse flotation

In this paper, the flotation separation of pyrite from sub-bituminous and meta-bituminous coals in the presence of slimes was investigated. The sub-bituminous coal and the meta-bituminous coal have significant differences in their surface properties compared with pyrite. The flotation experiments were performed in the presence of potassium amyl xanthate (PAX) collector. The adsorption of PAX on pyrite was significant while that on the coal surfaces was negligible. The recovery of pyrite from sub-bituminous coal increased by 55% when the concentration of PAX increased from 1×10−4mol/L to 5×10−4mol/L. Similarly, pyrite recovery from the meta-bituminous coal increased by up to 60% for the coarser size fraction upon increasing PAX concentration from 1×10−4mol/L to 5×10−4mol/L. Before the de-sliming process, the flotation recovery of pyrite increased with decreasing coal particle size whereas the opposite is true for pyrite grade. Desliming reduced the adsorption amount of PAX on pyrite by more than 50% because of the removal of fine particles that would otherwise be available for adsorption. Desulphurization of fine coal appears to be challenging probably due to the increased entrainment of fine coal particles during pyrite flotation. The de-sliming process increased pyrite grade by >20% for the meta-bituminous coal and by 10% for the sub-bituminous coal. The results suggest that excessive collector consumption by fine particles and slimes, and entrainment are the main challenges in separating pyrite from coal particles.

Effort of ionic liquids with [HSO4]‐ on oxidative desulphurization of coal

AbstractSulphur dioxide and soot produced during coal combustion are the main air pollution sources and increased emission of PM2.5 (particle matter with an aerodynamic diameter less than or equal to 2.5 µm) in China. In this investigation, two imidazolium ionic liquids (ILs), namely, 1‐butyl‐3‐methyl imidazolium bisulphate ([C4C1im][HSO4]) and 1‐carboxymethyl‐3‐methylimidazolium bisulphate([HOOCCH2mim][HSO4]), were used to remove sulphur from coal combined with 30 % hydrogen peroxide (H2O2) based on chemically oxidative desulphurization. The experimental results indicate that H2O2 played a dominant role in removing inorganic sulphur but only partially decreased organic sulphur. The [C4C1im][HSO4]‐H2O2 solution is able to remove 47.44 % of the total sulphur in coal and nearly 100 % of the inorganic sulphur while the [HOOCCH2mim][HSO4]‐H2O2 solution can remove 16.76 % of organic sulphur with a weaker ability to reduce inorganic components. According to the FTIR spectra analysis, the results show that the proportion of –SH, –CH3, –CH2–, and‐OH declined, while −COOH increased after the IL‐H2O2 treatment due to the oxidation enhancement in the presence of ionic liquids. Sulphur element compositions were measured using XPS, and the results also show that ionic liquids are favourable for improving the oxidation of –SH, –S–, and thiophene into sulphoxide and sulphone, which were extracted during the ionic liquid phase.

Lignite oxidative desulphurization: notice 3\u2014process technological aspects and application of products

The study reviews the process of oxidative desulphurization of high-sulphur Ukrainian lignite, which was performed by coal treatment using an air or air–steam mixture. In the process, sulphur-free fuel and tar from the decomposition of coal organic matter was obtained. Hence, the sulphur in the coal was converted into hydrogen sulphide. The coal desulphurization process is critical to power generation, power generation and technology, and technology field of application. The coal desulphurization process ensures the maximum recovery of the highest content of sulphur and hydrogen sulphide (H2S) in desulphurized gases at minimal energy costs. The process also enhances the maximum decomposition of tar and sulphur recovery (> 50%) during coal power generation. Based on summarized field studies, a block schematic diagram coupled with heat and material balances of the process was developed for the calculations. The application of the technology at the first stage of coal combustion in thermal power plants will enable the utilization of over 50% of recovered coal sulphur in the form of concentrated H2S or commercial elemental sulphur. This will, nevertheless, allow for a reduction of sulphur oxide pollution in the environment by at least 53%–56%. It has been suggested that the product of thermal decomposition of coal organic matter (tar) can be used as a component of furnace fuel oil or as a plasticizer of petroleum-based road bitumen.

Performance evaluation of microbial desulphurization of waterberg steam coal as a pre-combustion technique

The current study evaluates pre-combustion microbial desulphurization of medium – sulphur type coal containing total sulphur (1.45 wt. %) and pyritic sulphur (≥ 0.51 wt. %) in a laboratory scale. Coal samples used in the current study were supplied by one of South African Power Utility, Eskom power station as received from the nearby Waterberg coalfield in Limpopo in South Africa... After a stipulated hydraulic retention time (HRT), the coal samples were filtered, washed, dried and analyzed for total sulphur, ash content and calorific values. The calorific value of the coal significantly improved from 20.42 MJ/Kg to 24.16 MJ/Kg on the 5th day. The process removed up to 72 % of the total sulphur content in the coal samples at an HRT of day 9th. Furthermore, ash content reduced by 16 %. This study provides a novel breakthrough of an alternative microbial desulphurization process of Waterberg steam coal as a pre-treatment technique in order to meet stringent environmental emissions standards for SO2.

Bacterial desulphurization of low-rank coal: A case study of Eocene Lignite of Western Rajasthan, India

ABSTRACTHigh sulfur lignite samples collected from Giral mine was subjected to desulfurization using bacteria Burkholderia sp. GR 8–02 isolated from native lignite. A removal of 50.69% of total Sulfur (St) has been observed. The reduction in hydrogen and ash content was found up to 2.92% and 14.78%, respectively. In addition, relative carbon (up to 12.81%) and nitrogen (up to 34.52%) has also been increased. An increase in the relative concentration of volatile matter and fixed carbon (up to 19.47% & 3.29%) has been detected. In addition, the desulfurization of high sulfur lignite with Burkholderia sp. GR 8–02 increased the calorific value from 5.24% to 20.74%.

Desulphurization of medium sulphur waterberg steam coal in a batch operated scale: microbial solution

The current study evaluates pre-combustion microbial desulphurization of medium – sulphur type coal containing total sulphur (1.45 wt.%) and pyritic sulphur (= 0.51 wt. %) in a laboratory scale. Coal samples used in the current study were supplied by one of South African Power Utility, Eskom power station as received from the nearby Waterberg coalfield in Limpopo in South Africa. Coal samples were size fractioned using 13.2, 9.5, 8.0, 6.3, 5.6, 4.7, 2.36, 2.00, 1.00, 0.85 mm and below using automatic screens shaker. Coal sample containing particle size in the range of -0.85 mm was used in the experiments with bacteria isolated from the native coal mine site. After a stipulated hydraulic retention time (HRT), the coal samples were filtered, washed,dried and used for total sulphur and calorific value analysis. The calorific value of the coal significantly improved from 20.42 MJ/Kg to 24.16 MJ/Kg on the 5th day.The process removed up to 41% of the total sulphur content in the coal samples at a HRT of 8 days. This study provides a novel breakthrough of analternative microbial desulphurization process of Waterberg steam coal as a further pre-treatment technique in order to meet stringent environmental emissions standards for SO2.

Effect of complexing agents on desulphurization and deashing of coal by H2O2/H2SO4 leaching

The present study was aimed at investigating the effect of the addition of complexing agents on the removal efficiency of sulphur and ash contents during chemical leaching by acidified hydrogen peroxide. Representative coal sample from Lakhra was subjected to chemical leaching under various conditions of the parameters including time (60 and 120 min), temperature (25 and 50°C), complexing agents (citric acid and phosphoric acid) and the concentration of complexing agents (100 and 1000 ppm). The addition of complexing agents, i.e. citric acid and phosphoric acid imparted significant effects on improving the removal efficiency of sulphur and ash contents. Under optimized conditions, it was found out that the addition of citric acid improved the removal efficiency for sulphur from 63.88 to 83.47% and from 33.12 to 66.25% for ash. In case of phosphoric acid, the removal in sulphur and ash contents was increased from 63.77 to 80.77% and from 33.12 to 59.18%, respectively. Apparently, citric acid happened to be the most effective complexing agent, as compared to phosphoric acid. These results warrant subsequent detailed studies for further optimization of the process, including the use of some other complexing agents, as well.

Effect of some operational parameters on desulphurization of high sulphur Indian coal by KOH leaching

This paper presents an experimental study on the effect of potassium hydroxide concentration and reaction time on coal properties during desulphurization of high sulphur Indian coal. Experimental results showed that maximum of 36.79% of total sulphur can be removed from coal by potassium hydroxide leaching with 20% potassium hydroxide concentration and 24 h contact time at atmospheric condition. Total sulphur reduction was contributed by 45.03–49.01% pyritic sulphur, 24.10–33.73% sulphate sulphur and 20.93–30.62% organic sulphur depending on potassium hydroxide concentration of 5–20% and reaction time of 6–24 h. Experimental result shows that ash% of coal increased from 8.33 to 14.09% due to accumulation of insoluble potassium aluminosilicate in the coal. Gross calorific value of coal decreased from 6854 to 6084 kcal/kg due to increase of ash content of coal and loss of some combustible matter in leaching process. Physico-chemical characterizations of raw and treated coal samples were carried out by using field emission scanning electron microscope, Fourier transform infrared, petrographic analysis, thermogravimetric analysis and differential thermogravimetry to appraise the product quality. Field emission scanning electron microscope and coal petrographic image infer the occurrence of pitting and cavitation in the coal structure due to removal of pyrite sulphur (1.51–1.21%) from coal which causes escalation of vitrinite (67.65–70.43%) and few amounts of inertinite (18.03–18.86%) and liptinite (1.24–1.27%) as macerals. Thermogravimetric analysis–differential thermogravimetry analysis infers the improvement in combustion characteristics of treated coal by reduction in peak combustion temperature.

State of the art in the field of emission reduction of sulphur dioxide produced during coal combustion

ABSTRACTThe need for clean coal technologies to reduce the adverse environmental impact of coal combustion products has been grounded. The article deals with information concerning present and future technologies, directed towards the struggle against air pollution by SO2, produced during coal combustion. Their classification and critical rating from economical and technological points of views (including those developed by authors) have been performed. The method of comparing the effectiveness of flue gas desulphurization (FGD) processes and technologies of coal preventive desulphurization were offered.