Coal Carbon Research Articles

Synergistic effects of process-generated organic acids during co-hydrothermal carbonization of watermelon peel and high-sulfur coal

Substandard fuel properties and high sulfur levels remained bottlenecks for the utilization of biomass and low-grade coal for energy generation. This work systematically studied the synergistic effects of co-hydrothermal carbonization (co-HTC) of watermelon peel (WP) and high-sulfur coal using process-derived organic acids. Fuel properties, desulfurization efficiency, and combustion behaviors of co-HTC derived hydrochars and fuel blends of WP hydrochar and coal prepared by the typical post-hydrothermal carbonization (HTC) blending technique were compared. The physical and chemical compositions of WP/coal hydrochars were investigated to evaluate their corresponding fuel properties. In addition, flame characteristics were studied via single pellet combustion, while the chemical compositions of residual HTC process water were examined by gas-chromatography mass spectroscopy. Note-worthily, the co-HTC derived hydrochars were characterized by higher heating values in the range of 27.3–28.8 MJ/kg and fuel ratios of 2.67–6.95. HC-3:7, HC-5:5 and HC-7:3 showed higher desulfurization efficiencies (57.9–77.7%) compared to the post-HTC blending method (8.5–33.5%). Moreover, the co-HTC derived hydrochars exhibited lower post-combustion ash contents (8.8–12.0%) compared to CC-3:7 (17.3%), CC-5:5 (17.9%) and CC-7:3 (10.5%). Remarkably, HC-5:5 demonstrated the strongest synergistic effect of 70%. The flame observation results indicated that co-HTC derived hydrochars exhibited more stable combustion flames than the post-treatment blended samples. Hence, co-HTC provides a low-cost and eco-friendly approach for converting WP and high-sulfur coal into cleaner solid fuel.

Structural dependent persulfate activation by coke powder for aniline degradation

• Structural dependent PS activation by CP is investigated. • CP holds excellent activity for PS activation over a wide pH range. • Dissolved oxygen plays an insignificant role in ROS generation. • The carbonaceous component on CP involves in PS activation but ash does not. • PFRs, OFGs, sp 2 -hybridized carbon and defects contribute to persulfate activation. Coke powder (CP), the by-product of coal carbonization, its activity of persulfate (PS) activation was systematically investigated. Structural dependent organic pollutant degradation performances and the related mechanisms were discussed in detail. The structural characteristics of CP were studied using X-ray diffraction, Raman, Fourier transform infrared spectra, X-ray photoelectron spectra, and electron paramagnetic resonance (EPR) etc. Characterization results indicate that CP contains ∼ 78% carbon and presents highly disordered amorphous structures with abundant oxygenated functional groups (OFGs) and persistent free radicals (PRFs). The catalytic application reveals that CP held excellent activity for PS activation across a wide pH range from 3 − 11. In the presence of 0.5 g/L CP, 0.25 mM PS and 0.021 mM aniline (pH 7 ± 0.2), >99% aniline was degraded within 40 min. Under the interference of inorganic anions (Cl − , HCO 3 − and SO 4 2− ), 98% aniline degradation efficiency still could be achieved. Meanwhile, quenching tests and EPR demonstrated that the superoxide anion radical (O 2 − ) was responsible for aniline degradation in CP/PS system, and its generation was independent of dissolved oxygen. The outstanding performance of aniline degradation and ROS generation were attributed to the existence of PRFs, sp 2 -hybridized carbon, OFGs and defects on CP inducing O–O bonding homolytic cleavage of PS into sulfate radicals. Besides, the OFGs including C–OH and –COOH as electron donors facilitated PS decomposition to generate O 2 − . The findings imply that CP is an excellent PS activator, and clarify the development of remediation materials by using by-products of coking process for wastewater treatment.

Functional group chemistry and its functions in coal carbonization: a scientific intelligence from infrared spectroscopy

Functional group chemistry and its functions in coal carbonization: a scientific intelligence from infrared spectroscopy

Modeling and Optimization of Biochar Injection into Blast Furnace to Mitigate the Fossil CO2 Emission

Most modern blast furnaces (BFs) operate with Pulverized Coal Injection (PCI), but renewable and carbon neutral biochar could be applied to reduce the fossil CO2 emission in the short term. In the present study, heat and mass balance-based model (MASMOD) is applied to evaluate the potential of biochar in partial and full replacement of injected pulverized coal (PC) in the ironmaking BF. The impact of biochar injection on the raceway adiabatic flame temperature (RAFT) and top gas temperature (TGT) is evaluated. Three grades of biochar, produced from the pyrolysis of sawdust, were evaluated in this study. The total carbon content was 79.2%, 93.4% and 89.2% in biochar 1, 2 and 3, respectively, while it was 81.6% in the reference PC. For each type of biochar, 6 cases were designed at different injection levels from 30 kg/tHM up to 143 kg/tHM, which represent 100% replacement of PC in the applied case, while the top charged coke is fixed in all cases as reference. The oxygen enrichment, RAFT, and TGT are fixed for certain cases, and have been calculated by MASMOD in other cases to identify the optimum level of biochar injection. The MASMOD calculation showed that as the injection rate of biochar 1 and biochar 2 increased, the RAFT increased by ~190 °C, while TGT decreased by ~45 °C at 100% replacement of PC with biochar. By optimizing the moisture content of biochar and the oxygen enrichment in the blast, it is possible to reach 100% replacement of PC without much affecting the RAFT and TGT. Biochar 3 was able to replace 100% of PC without deteriorating the RAFT or TGT.

Effects of Cofiring Coal and Biomass Fuel on the Pulverized Coal Injection Combustion Zone in Blast Furnaces

CO2 emissions are a major contributor to global warming. Biomass combustion is one approach to tackling this issue. Biomass is used with coal combustion in thermal power plants or with blast furnaces (BFs) because it is a carbon-neutral fuel; therefore, biomass provides the advantage of reduced CO2 emissions. To examine the effect of co-firing on pulverized coal injection (PCI) in BFs, two coals of different ranks were blended with the biomass in different proportions, and then their combustion behaviors were examined using a laminar flow reactor (LFR). The PCI combustion primarily functions as a source of heat and CO to supply the upper part of the BF. To create a similar PCI combustion environment, the LFR burner forms a diffusion flat flame with an oxygen concentration of 26% with a flame temperature of ~2000–2250 K at a heating rate of 105 K/s. The combustion characteristics, such as the flame structure, burning coal particle temperature, unburned carbon (UBC), and CO and CO2 emissions were measured to evaluate their effect on PCI combustion. With the increase in the biomass blending ratio, the brightness of the volatile cloud significantly increased, and the particle temperature tended to decrease. The fragmentation phenomenon, which was observed for certain coal samples, decreased with the increase in the biomass blending ratio. In particular, with an increase in the biomass blending ratio, the optimum combustion point occurred, caused by the fragmentation of coal and volatile gas combustion of biomass.

The coal as high performance and low cost anodes for sodium-ion batteries

With good electrochemical performances and cost advantages, sodium-ion batteries (SIBs) have great potential in energy storage and other fields. It is crucial to research anode materials for SIBs with high performance and low cost to promote large-scale industrialization. In this study, the amorphous carbon-based anodes prepared by one-step carbonization of bituminous coal were firstly reported. When the materials were worked as anodes for SIBs in the voltage range of 0–1.5 V, an excellent reversible capacity of 270 mAh·g−1 and an initial coulombic efficiency (ICE) of 84.4% were achieved at a current density of 35 mA·g−1. More impressively, the carbon anodes possess merits of low cost, making the designed carbon anodes practicable to the industrial applications.

Study on electrochemical improvement of flotation reagents for carbon recovery from coal gangue

ABSTRACT A novel collector to improve the collecting capacity of the coal gangue and to reduce the consumption of the medicament was proposed in this paper, which the potassium permanganate is used as a catalyst to carry out electrochemical catalytic oxidation modification on the kerosene. The effects of electrolysis time, electrolytic current density, catalyst dosage, electrolyte concentration, different catalysts and electrodes on the oxidation of the kerosene were investigated, and the compositions and properties of before and after kerosene oxidation employing FTIR and GC-MS. Results showed that the oxidation effect is the best which the acid value of the product is 7.32mgKOH/g when the electrolysis time is 40 minutes, the amount of catalyst is 500 mg/L, and the electrolytic current density is 2000 A/m2. The flotation results showed that the amount of collector could be saved by 200 g/t dosage and the frother can be saved by 80 g/t dosage by using oxidized kerosene as a collector when combustible matter recovery was 20−25% higher than that of common kerosene and clean coal yield was 8−10% higher than that of common kerosene. The FTIR and GC-MS analysis of the product revealed that some carbonyl compounds and unsaturated hydrocarbons are formed in the product after electrochemical treatment of kerosene, which enhances the collection performance of kerosene. At the same time, alcohol, ether, and ester-creating in the product make the product has been specific foaming performance. This work provides a new reagent for coal gangue carbon recovery.

Current practice and future projection for coal-to-SNG in China

With the rapid development of economy in recent years, China's supply and demand gap for energy gradually increased. To alleviate the problem of the insufficient reserves of natural gas in China, coal to substitute natural gas (coal-to-SNG) is considered to be a promising option, especially for urban use. However, the coal-to-SNG industry of China started late and the technology is relatively backward. Therefore, the development of China's coal-to-SNG industry needs the corresponding recommendations. Based on the understanding of the current technical conditions and market environment of coal gasification in China, as well as the endowment of coal resources and the policy environment, this paper makes a strategic analysis on China's coal-to-SNG industry. This paper mainly uses the PEST (Politics, Economy, society, Technology) analysis method and SWOT (Strengths, Weaknesses, Opportunities, Threats) analysis method. Policy factors are mainly analyzed from three aspects of political system, policy promulgation and international agreements. Economic factors are focused on three aspects of Industrial structure, natural gas demand and economic costs. Social factors are discussed from three aspects of social status quo, environmental protection and social development. Technical factors are evaluated from three aspects of coal type, water consumption and carbon emissions. The SWOT analysis method is the analysis of the coal-to-SNG industry in four aspects including the advantages, disadvantages, opportunities and threats. Through the coal-to-SNG analysis, this paper puts forward some suggestions for the development of the industry.

Soil pollution of the Labin city area with polycyclic aromatic hydrocarbons derived from Raša coal mining and associated industries

The aim of this study was to determine the mass fraction of polycyclic aromatic hydrocarbons (PAHs) in the soil of the Labin city area (west Croatia) as a consequence of the pollution caused by centuries old Raša coal mining and associated metal processing and foundry industries. Samples of topsoil down to 10-cm depth, following the removal of plant cover, were collected, air-dried, and sieved to <2 mm. Afterwards, they were extracted, and PAH levels were measured by high performance liquid chromatography using a fluorescence detector with a varying wavelength of excitation and emission (HPLC/FLD). The results showed substantially elevated levels of PAHs across the study area. The soil pollution with PAHs increased in the direction towards the Raša Bay, where a former coal separation unit was in operation decades ago. The results demonstrated the presence of pyrolitic PAHs that resulted from Raša coal combustion at high temperatures in power plants, and unburnt coal-derived PAHs formed by Raša coal carbonization. This paper for the first time reports levels of PAHs in soil of the Labin city area, establishing them as higher than the values set by Croatian legislation. Therefore, this study clearly calls for immediate clean-up measures in order to solve the environmental pollution issue of the vulnerable local karst area.

Simultaneous Saxs-Waxs Study on Carbonization of Coking Coal

Simultaneous Saxs-Waxs Study on Carbonization of Coking Coal

Oxidation characteristics of soot in different entrained flow gasification processes

The morphological structure of six samples including the rapid pyrolysis soot of solid fuels (coal, biomass), the soot from non-catalytic partial oxidation(NCPOX) of natural gas in a laboratory pilot plant and an industrial plant, the commercial carbon black in natural gas furnace/coal tar furnace, were characterized by using a transmission electron microscope. Based on atmospheric thermogravimetric analyzer, the non-isothermal method (50–800 °C) was adopted to study the ignition point and the oxidation reaction rate of soot, and the oxidation reaction kinetic parameters of soot was obtained. Studies showed that the physical and chemical properties of various soot were quite different. The soot from the rapid pyrolysis of coal and biomass presented a higher sphericity and a larger particle size. The Lab-NCPOX-soot was formed at a lower temperature which caused the particle being wrapped by a carbon capsule. The Ind-NCPOX-soothad a hollow structure and a small particle size. The reactivity of the Lab-NCPOX-soot is close to that of the Ind-NCPOX-soot, which is 3.1 times that of the commercial natural gas furnace carbon black and 3.2 times that of the commercial coal tar furnace carbon black; the reactivity of NCPOX-soot is 9.0 times of the rapid pyrolysis soot of coal, and 26.6 times of the rapid pyrolysis soot of biomass. The activation energy of 2 kinds of NCPOX-soot and 2 kinds of commercial carbon blacks present staged forms with increasing temperature. The activation energy of the 2 rapid pyrolysis soot was basically unchanged with increasing the temperature.

The Effect of Alkalized Biomass On Pulverized Coal Molding and Carbonization of Bio-Briquette

The Effect of Alkalized Biomass On Pulverized Coal Molding and Carbonization of Bio-Briquette

A small furnace for in-situ SAXS/WAXS study on medium temperature carbonisation of coal

The medium temperature carbonisation of coal refers to the process of decomposition of coal by heating to 700°C in absence of air. It is one of the important ways of coal utilisation. Small/wide angle X-ray scattering (SAXS/WAXS) can be used to study the pore and carbon matrix structure of coal. Recently, a small furnace for in-situ study of medium temperature carbonisation of coal by simultaneous or respective SAXS and WAXS was developed and integrated into the SAXS instrument at the 1W2A station of Beijing Synchrotron Radiation Facility (BSRF). A test on a kind of non-caking coal shows that the furnace works well, and the experimental result is reasonable. [Received: January 5, 2021; Accepted: March 2, 2021]

A small furnace for in-situ SAXS/WAXS study on medium temperature carbonisation of coal

A small furnace for in-situ SAXS/WAXS study on medium temperature carbonisation of coal

Enhanced Combustion of Bituminous Coal and Semicoke Mixture by Ferric Oxide with Thermographic and Kinetic Analyses.

We study the specific catalytic effect of the catalyst on the combustion process of pulverized coal of increasing the proportion of semicoke in the mixture of semicoke and bituminous coal, and reducing the cost of blast-furnace coal injection. A combination of thermogravimetric and kinetic analyses were used to study the catalytic effect of Fe2O3 on semicoke and bituminous coal, and to improve the amount of semicoke in the mixed coal powder of bituminous coal and semicoke. Experimental results showed that Fe2O3 had a catalytic effect on both semicoke and bituminous coal, but there were differences in the catalytic stages of the same catalyst for different pulverized coal types. The addition of 2 wt % Fe2O3 to semicoke and bituminous coal each led to the ignition temperature and maximal burning rate temperature of the semicoke decreasing, indicating that the catalyst promoted the precipitation of a volatile fraction from the semicoke. The maximal burning rate temperature and burnout temperature of the bituminous coal decreased, and maximal weight loss rate increased, indicating that the catalyst promoted the combustion of the fixed carbon of bituminous coal. The optimal proportioning amount of semicoke in the mixed coal powder without the addition of a catalyst was 25%. After adding 2 wt % Fe2O3, the proportional amount of semicoke increased by 10%. The addition of the catalyst resulted in even lower activation energy for the same conversion rate. When the conversion rate was in the ranges of 0.1–0.2 and 0.5–0.7, the activation energy decreased by 22% and 26%, respectively, compared with that without a catalyst. Fe2O3 promoted the combustion of bituminous coal and semicoke. This enhanced the combustion performance of the pulverized coal mix and increased the proportion of semicoke in the mix, which has certain guiding significance in reducing the cost of blast-furnace iron making.

Fabrication of photoacoustic cell and thermal diffusivity measurement of coal carbon black using it

Photoacoustic spectroscopy (PAS) is an important technique for the characterization of materials by measuring heat generation in the sample. The photoacoustic (PA) signal detection is rather difficult due to the weaker signal intensity and unavailability of sensitive detectors of acoustic waves. In this work, authors have fabricated a photoacoustic cell and made parametric studies to get the maximum signal. For the optimum signal, the volume of acoustic cell cavity was found to 9.42 × 10−7 m3. After the optimization, thermal diffusivity of coal Carbon black was measured and it was found to be 2.206 × 10−4 m2/s which is very close to the standard diffusivity value of coal carbon.

Combustion and slagging characteristics of hydrochar derived from the co-hydrothermal carbonization of PVC and alkali coal

This work investigated on the effect of co-hydrothermal carbonization (co-HTC) of polyvinyl chloride (PVC) and alkali coal on combustion and slagging characteristics of the generated fuels (hydrochar). Fuel properties were assessed in terms of ultimate and proximate analysis, functional groups evolution, and ash melting characteristics. The loss of C–O functional groups in coal would be accompanied by the liberation of some elements such as Na and Ca, which were often associated with such groups. The hydrochars presented higher ignition temperature and average combustion rates compared with raw coal. The hydrochar generated from co-HTC at 250 °C showed the best combustion performance due to the enhancement of air contacting and transformation, which was attributed to its porous structure, smaller uniform particle, and relative higher surface area. The activation energy of hydrochars was increased at the ignition stage while was decreased at the combustion stage according to the kinetic analysis. The fusion temperature was increased resulting from the removal of alkali and alkaline earth metals (AAEMs) during the co-HTC process. From the perspective of waste-to-energy, the co-HTC of high-alkali coal and PVC seems to be a feasible solution to improve combustion and slagging characteristics.

ULASAN: PEMBANGUNAN TEKNOLOGI PENGGASAN DAN PENGGUNAAN

Gasification technologies have the potential to produce clean and efficient energy sources. This technology is capable of producing synthesis gas from low or negative carbon -based raw materials such as coal, petroleum coke, high sulfur fuel oil, waste or waste materials and biomass. The gas produced from the process is used to replace natural gas to generate electrical power, or acts as basic raw material for producing chemicals and liquid fuels. Gasification is a process which utilizes heat, pressure, and steam to convert materials directly into gases, such as carbon monoxide and hydrogen gases. Despite differing in various aspects, gasification technologies have four common engineering factors such as atmospheric gasification reactors (oxygen or air content level), internal and external heating, reactor design and operating temperature. Raw materials, either in dry form or small granules, are fed into the reactor chamber called gasifier. Raw materials subjected to heat, pressure as well as an environment with rich or low oxygen content. Hydrocarbon gas (also known as Syngas), liquid hydrocarbon (oil) and coal (carbon black and ash) are the three main products of gasification. Syngas can be used as a fuel to produce electricity or steam, or acts as a basic block for various types of chemicals. When mixed with air, Syngas can be used in petrol or diesel engines with slight modifications to the engine.

Value-added products from pyrolysis of hydrochar derived from polyvinyl chloride and alkali coal

This work targets to produce multi value-added products by pyrolysis of hydrochars obtained from co-hydrothermal carbonization (co-HTC) of PVC and alkali coal. The hydrochars pyrolysis was carried out with a downdraft fixed bed reactor. The results indicate that HTC promoted the damage of oxygen functional groups, and the fixed carbon content and calorific value were considerably improved after co-HTC. The entire pyrolysis was delayed for coal hydrochar due to the increase of stable compositions in coal structure and improvement of coal rank. Besides, the PVC addition weakened this delay because of its instability, which could be verified by the activation energy. The H2 and CH4 yields increased in syngas, while the CO2 yield was concurrently reduced because of the removal of oxygen by decarboxylation. The obtained H2/CO ratio of syngas from hydrochar pyrolysis ranged from 1.34 to 4.33 depending on the pyrolysis parameters. The tar yield from hydrochar pyrolysis was lower than that of raw coal, which was ascribed to the lower degree of crosslinking in hydrochar facilitating the release of tar. The aromatic degree and rich pore structures of char indicated its great potential for contaminants adsorption which was further confirmed by the malachite green adsorption experiments. These findings could provide comprehensive knowledge on producing multi value-added products (hydrogen-rich syngas, poly-aromatic tar and adsorbent-char) from hydrochar pyrolysis, which would promote the economical utilization of high alkali coal and chlorinated wastes.

Utilization Prospects of Carbon Concentrate – a Product of Aluminium Smelting Carbon Dust Processing

The possibilities of utilization of technogenic products of aluminum production: coal foam and carbon concentrate (СС) are considered. It is proposed to utilize CC in order to extract valuable components. The regularities of the utilization process of CC by the combustion method have been studied. It was found that the content of germanium in ash is determined by the temperature and the oxygen partial pressure in the system. Gallium is concentrated in ash in an amount of 0.8 wt.% during the combustion in a fluidized bed at a temperature of 1200 °C, the germanium extraction into sublimates reaches 90 %. The results of the leaching of gallium from the ash residue in acidic and basic media are presented; the maximum gallium extraction was 90 and 94 %, respectively.