Shale Semicoke Research Articles

Bonding performance of reinforced and oil shale residue concrete

Oil shale residue concrete is prepared by utilizing oil shale semi-coke. It has advantages such as low cost and a high solid waste utilization rate. The study of its bonding-slip characteristics with steel bars is a prerequisite for their application in engineering structures. To study the bonding-slip performance of reinforced oil shale residue concrete, 12 half-beam specimens were designed for the bonding performance test. The test parameters included the substitution rate of oil shale residue, bonding length, and cover thickness. The influences of the aforementioned factors and variables on the stress-slip curve and bonding strength were analyzed. The results showed that the anchoring bond length had the greatest impact on the average bonding strengths of the steel bar and concrete. As the bonding length increases from 5d to 10d, the average bonding strength decreased by approximately 18%. The cover thickness had the second-greatest influence on the bonding strength. As the cover thickness increased from 20 to 30 mm, the average bonding strength increased by more than 12%. The substitution rate of the oil shale residue had the least effect on the average bonding strength, and as the substitution rate increased, the bonding strength decrease with a minor magnitude. Through verification, the bonding-slip constitutive model obtained by fitting the experimental data was found to fit the experimental values well.

Activated Carbon Derived from Waste Oil Shale Semi-Coke for Supercapacitor Application.

As fossil fuels gradually deplete, oil shale, one of the world's largest energy resources, has attracted much attention. Oil shale semi-coke (OSS) is the main byproduct of oil shale pyrolysis, which is produced in large quantities and causes severe environmental pollution. Therefore, there is an urgent need to explore a method suitable for the sustainable and effective utilization of OSS. In this study, OSS was used to prepare activated carbon by microwave-assisted separation and chemical activation, which was then applied in the field of supercapacitors. Raman, XRD, FT-IR, TEM, and nitrogen adsorption-desorption were adopted to characterize activated carbon. The results showed that ACF activated with FeCl3-ZnCl2/carbon as a precursor has larger specific surface area, suitable pore size, and higher degree of graphitization compared with the materials prepared by other activation methods. The electrochemical properties of several active carbon materials were also evaluated by CV, GCD, and EIS measurements. The specific surface area of ACF is 1478 m2 g-1, when the current density is 1 A g-1, the specific capacitance is 185.0 F g-1. After 5000 cycles of testing, the capacitance retention rate was as high as 99.5%, which is expected to provide a new strategy of converting waste products to low-cost activated carbon materials for high-performance supercapacitors.

Laboratory investigation and BP neural network modeling on heat-activated oil shale semi-coke attributable to the mechanical properties of concrete

Concrete construction requires the consumption of large quantities of raw materials. If oil shale semi-coke can be used in concrete projects in a reasonable way, not only will it ease the shortage of raw materials for concrete, but it will also consume oil shale semi-coke and reduce its ecological impact. This investigation aims to study the feasibility of using semi-coke in concrete construction based on its mechanical properties. The chemical components and microstructures of four thermal activation temperature oil shale semi-cokes were first analyzed by X-Ray Fluorescence (XRF) and scanning electron microscope (SEM). Then, by replacing the cement with equal mass of semi-coke, the effect of heat-activated calcination temperature and the amount of semi-coke admixture on the mechanical strength of mortars sand and concrete was tested. Finally, a BP neural network was used to establish a strength prediction model for semi-coke concrete and the evolution of internal pores of semi-coke concrete was analyzed by nuclear magnetic resonance (NMR). The results show that semi-coke is mainly composed of SiO2 and Al2O3, which can be used as a concrete mineral admixture for volcanic ash reaction. The oil shale semi-coke is flaky with a porous surface, resulting in the semi-coke contributing more to the flexural strength of the mortar than to the compressive strength. At the calcination temperature of 500 ℃ and a semi-coke content of 15%, the concrete has the lowest porosity and the best mechanical properties, and is therefore recommended. The developed BP neural network prediction model has a high prediction level and can provide guidance for practical engineering. The increase in the amount of coke admixture leads to a continuous increase in the number of pores in the medium and large pore sizes inside the concrete, which is the main reason for the change in concrete strength due to semi-coke.

Synthesis of biochar/clay mineral nanocomposites using oil shale semi-coke waste for removal of organic pollutants

Due to the poor surface/interfacial interaction and the large gaps in the size and microstructure between biomass and clay mineral, it was difficult to adjust the structure and performance of biochar/clay mineral composites at the molecular level. Herein, oil shale semi-coke composed of multi-minerals and organic matters was used as a promising precursor to prepare biochar/clay mineral nanocomposites via phosphoric acid-assisted hydrothermal treatment followed by KOH activation for removal of organic pollutants from aqueous solution. The results revealed that the nanocomposites presented well-defined sheet-like morphology, and the carbon species uniformly anchored on the surface of clay minerals. With the changes in the pore structure, surface charge and functional groups after two-step modification, the nanocomposites exhibited much better adsorption property toward organic pollutants than the raw oil shale semi-coke, and the maximum adsorption capacities of methylene blue, methyl violet, tetracycline, and malachite green were 165.30 mg g−1, 159.02 mg g−1, 145.89 mg g−1, and 2137.36 mg g−1, respectively. The adsorption mechanisms involved electrostatic attraction, π–π stacking and hydrogen bonds. After five consecutive adsorption–desorption, there was no obvious decrease in the adsorption capacity of malachite green, exhibiting good cyclic regeneration performance. It is expected to provide a feasible strategy for the preparation of biochar/clay mineral nanocomposites with the excellent adsorption performances for removal of organic pollutants based on full-component resource utilization of oil shale semi-coke.Graphical

Steam Activation of Oil Shale to Enhance the Porosity of Produced Semicoke

ABSTRACT Finding a recycling method for waste materials is attracting increasing attention. In Estonia, semicoke from the shale oil industry is a material that can be used for adsorbent production. For this application, it is important to characterize the surface properties and enhance the porosity. In this study, different pyrolysis temperatures (from 500 to 800 °C) and steam activation parameters were applied to determine their influences on the surface properties of oil shale semicoke. It was found that pyrolysis at 700°C resulted in the highest Brunauer – Emmett–Teller surface area of 59 m2/g. To investigate the effect of activation, up to 70% vol of steam was added to the pyrolysis environment for different durations (15–60 min). Although the effect was relatively small, shorter activation times and less steam resulted in larger surface areas. The highest surface areas (68–69 m2/g) were achieved when activation was carried out for 15 to 30 min with 25–50% vol of steam in the environment after pyrolysis at 700°C. It can be concluded that longer activation and more steam causes widening and collapsing of some pore structures, resulting in a decrease in the surface area and total pore volume.

Improved fertilization efficiency of manure compost obtained by using oil shale semicoke as the bulking agent

Oil shale semicoke is a kind of solid waste produced during the retorting process of oil shale, which could cause environmental pollution without reasonable disposing. In our previous study, the abandoned semicoke was recycled as bulking agent to reduce the nitrogen loss and greenhouse gases emission during composting. But influences of the obtained semicoke-blended compost on soil properties and plant growth remained unclear, which would be discussed in this study. Through leaching experiments, it was found that the N/P/K retention capacity of soil mixed with semicoke-blended compost significantly increased for the good nutrients sorption capacity of oil shale semicoke. Subsequently, germination test showed the germination index of semicoke-blended compost could attain 120%, implying its low phytotoxicity. And pot experiments exhibited the biomass of cress and Brassica rapa significantly increased by 2–4 times when applying semicoke-blended compost as fertilizer, exhibiting its great benefits to plants. For the increase of crop yield, it was closely related to their elevated nutrients uptake efficiency, also might be related to the improved soil microbial community and activity as the microbial analysis indicated. Finally, results of pollutant detection showed the concentration of polycyclic aromatic hydrocarbons, Cr, As, Cd and Pb in the mature semicoke-blended compost obtained through composting was 2.82, 95.30, 5.95, 0.34 and 14.45 mg kg−1 respectively, meeting the standard for soil application. The research suggests composting could be an effective method for the harmless disposing and resource recycling of oil shale semicoke waste.

Evaluation of the organic matter product of Huadian oil shale during pyrolysis using multiple approaches: Guidance for the in situ conversion of oil shale

The in situ conversion of oil shale has gradually become the main method of oil shale development, which provides theoretical guidance for the Huadian oil shale in situ conversion programme. In this paper, a retorting simulation experiment of real underground pressure is carried out for Huadian oil shale, and the pyrolysis process of oil shale samples, the subsurface conversion environment and hydrocarbon generation patterns are systematically analysed. The results show that the 375–425 °C stage is the main oil production stage of oil shale. According to the group composition characteristics and low-temperature retorting data of residual oil collected in oil shale semicoke and pyrolysis oil at different pyrolysis temperatures, the heating temperature should not be lower than 350 °C. The pyrolysis evaluation results of oil shale semicoke indicate that the pyrolysis temperature of 425 °C is a turning point. When the temperature reaches 425 °C, the oil shale has no hydrocarbon generation value. The temperature of Huadian oil shale should be controlled within 375–425 °C in the in situ conversion project to obtain the greatest shale oil resources with the lowest energy input cost.

Preparation of efficient adsorbent with dual adsorption function based on semi-coke: Adsorption properties and mechanisms

Solid waste oil shale semi-coke (SC) is considered as a potential material for the preparation of adsorbents due to its rich organic and inorganic components. However, the dense structure and the complex form of the components present make it unsatisfactory for adsorption. In this study, using Alkali corrosion under hydrothermal condition, SC was prepared as an adsorbent material PSSC with excellent adsorption performance for both anionic and cationic dyes. The related characterization analysis showed that most of the organic matter and silicates of SC reacted with inorganic matter to form silicon carbide. The specific surface area of PSSC increased significantly (from 7.47 m2/g to 1353.99 m2/g) leading to the maximum adsorption of PSSC on Methylene blue (MB) and Congo red (CR) reached at 974.66 mg/g and 562.41 mg/g, respectively, which far exceeded the adsorption of SC on both dyes. Finally, the adsorption mechanisms were revealed from the structural and energetic perspectives. The results showed that the modification process increased the type and number of adsorption sites, and that these adsorption sites exhibited different capturing abilities for the two dyes with the change of contact temperature.

Eco-friendly superabsorbent composites based on calcined semicoke and polydimethylourea phosphate: Synthesis, swelling behavior, degradability and their impact on cabbage growth

In this work, novel eco-friendly superabsorbent composites of chitosan-grafted-polyacrylic acid/polydimethylourea phosphate/calcined semicoke (CS-g-PAA/PDUP/CSC) with the semi-interpenetrating network (semi-IPN) were developed via a convenient redox polymerization at room temperature. The redox polymerization was triggered by the calcined oil shale semicoke (CSC) under air atmosphere, in which the iron-compounds of CSC and Na2S2O3 were employed as oxidizing agent and reducing agent, respectively. The CS-g-PAA/PDUP/CSC composites prepared at the optimal conditions exhibited the maximum water absorption capacity of 412.89 and 51.30 g/g in deionized water and 0.9 wt% NaCl solution within 60 min, respectively. The excellent water absorption and retention performance were related to the introduction of CSC, which could be served as an inorganic component weakening the hydrogen-bond interaction between the functional groups in the polymer matrix and the semi-IPN. The superabsorbent composites also showed the favorable degradability, and 42.35 % of superabsorbent was degraded at 90 days. Interestingly, the nitrogen element provided by urea and chitosan could be released during degradation and directly absorbed by the plant to promote the growth. Integration of the above performance, the prepared composites may be used for better water resources management in agriculture taken into account of the corresponding environmental benefits.

Slow Release and Water Retention Performance of Poly(acrylic acid-co-acrylamide)/Fulvic Acid/Oil Shale Semicoke Superabsorbent Composites.

In order to achieve the low cost and multifunction of superabsorbent composites, poly(acrylic acid-co-acrylamide)/fulvic acid/oil shale semicoke (PAMFS) were prepared by free radical copolymerization of fulvic acid (FA), oil shale semicoke (OSSC), acrylic acid (AA) and acrylamide (AM). The characterization results revealed that FA and OSSC were involved in the construction of a three-dimensional (3D) polymeric network via hydrogen bonding and covalent bonding. The water absorbency of PAMFS in distilled water and 0.9 wt% NaCl solution were 724 and 98 g/g, respectively. The FA slow release of PAMFS in distilled water and soil was achieved due to the interaction between FA and the functional groups of polymer matrix by hydrogen bonds and covalent bonds. Furthermore, the potted experiment indicated that the addition of PAMFS to soil can significantly promote plant growth compared with the pure soil, regardless of water stress. Therefore, this superabsorbent composite showed an excellent water absorption and salt resistance performance, as well as nice slow release performance. It has a broad application prospect.

Effect of steel slag bed material on ash deposition and Na migration in circulating fluidised bed during Zhundong lignite combustion

AbstractThis study verified the effect of steel slag as alternative bed material on ash deposition in circulating fluidised bed (CFB) burning high‐sodium Zhundong lignite (ZD). Sample of ZD was burned in a lab‐scale CFB at 950°C, and the obtained fly ash and ash deposits were characterised. Results showed that the presence of steel slag bed material leads to the abundance of Na (2.39 wt%) in fly ash. Na‐bearing minerals such as Na2SO4, Na2Si2O5 and NaCl of low melting points had been identified, resulting in severe ash deposition on heat transfer surfaces than that with quartz as bed material. This could be mitigated by incorporating 10 wt% oil shale semi‐coke (SC) into ZD, among which Na was captured by aluminosilicate and retained in the interior of SC as (Na, Ca)Al(Si, Al)3O8 of high melting point. Na in the fly ash thus decreased to 1.05 wt% and in the form of high melting‐point Na(AlSi3O8). In addition, ESEM confirms that the SC particles after capturing Na still had an ash fusion temperature of 1280°C, which were insufficient to induce bed particle agglomeration.

Calcined Oil Shale Semi-coke for Significantly Improved Performance Alginate-Based Film by Crosslinking with Ca2+

Calcined Oil Shale Semi-coke for Significantly Improved Performance Alginate-Based Film by Crosslinking with Ca2+

Synthesis of an absorption material based on oil shale semi-coke: Discussion to adsorption mechanism and corresponding site energy distribution analysis

Oil shale semi-coke (SC) is an industrial solid wastes, which is urgently needed to be transformed into high value-added products. In this work, a new adsorbent AFSC with high adsorption property for Congo red (CR) (793.62 mg/g) better than SC (46.45 mg/g) were synthesized by hydrothermal reaction of pretreated SC with oxalic acid (OA) and Fe(III). The microscopic structure, chemical composition and adsorption performance of the adsorbent were studied, and the reaction parameters for synthesizing an efficient adsorbent were optimized. The results indicate that AFSC are mainly composed of quartz and humboldtine, the specific surface area of that obviously raised, and the surface negative charge decreased, which developed the adsorption properties of the adsorbent. The adsorption behavior and mechanism are further studied. Site energy distribution (SED) theory suggested that more high-energy sites was generated on AFSC, which resulted in a higher adsorption amount of AFSC for CR. This work provides a better way for the effective application of SC waste.

Research on preparation and properties of a multifunctional superabsorbent based on semicoke and humic acid

. • A novel superabsorbent composite was prepared by introduction of SC and HA. • Superabsorbent composite showed water retention and slow-release fertilizer functions. • Composite containing 15 wt% of HA and 6 wt% of SC could remarkably improve water retention. • The growth promoting effect of plants was clearly found by adding of PAA/SC/HA in soil. Superabsorbent integrated multiple functions, including absorbing water, preserving water and controlled releasing for fertilizer, which has attracted extensive attention in modern agriculture. In this study, a novel multifunctional superabsorbent of polyacrylic acid/humic acid/semicoke (PAA/HA/SC) with high water retention and favorable slow release performance was developed by incorporation of humic acid (HA) and oil shale semicoke (SC) via a simple free radical polymerization. The water retention, swelling kinetics, pH-dependent and swelling reversibility were investigated systematically. The water retention results showed that the prepared superabsorbent exhibited outstanding water-retention capacities of 824 g/g and 80 g/g in distilled water and 0.9 wt% NaCl solution respectively, as 15 wt% of HA and 6 wt% of SC were introduced into the three dimensional polymeric network of PAA. The slow release behaviors in distilled water and various salt solutions indicated that the release amount of HA was relatively fast in the initial stage, and then became flat after 16 days. Besides, the soil column leaching experiment revealed that the release amount of the HA reached the maximum value of 222.14 mg/L after 9 days, and potted experiment confirmed the growth-promoting effect for plant of PAA/HA/SC. This work explored the practical application of SC in green and sustainable chemical engineering area, also provided an important reference for application of multifunctional superabsorbent in modern agriculture.

From the Waste Semicoke to Superabsorbent Composite: Synthesis, Characterization and Performance Evaluation

Oil shale semicoke (SC), which generated during the production of shale oil has attracted much attention in agriculture recently, as the composition of organic matter, clay mineral and else. In this study, a novel superabsorbent composite of poly(acrylic acid-co-acrylamide)/semicoke (P(AA-co-AM)/SC) was prepared by polymerization of the acrylic acid (AA) and acrylamide (AM) via a convenient one-step reaction as the presence of SC. The characterization of FTIR, SEM, XPS and TG indicated that the successful polymerization and the SC had participated into the construction of 3D polymeric network in superabsorbent. The performance testing results showed that the superabsorbent composites exhibited the excellent water absorbency, favorable water retention properties, fast swelling rate, and nice water reusability. And a 10% of SC amount could improve the water absorbency to 643.13 g/g and 79.82 g/g in distilled water and 0.9% NaCl solution, respectively. The potted culture experiments revealed that the increased water retaining capacity of soil and obvious growth promoting effect for crop. In a word, the novel superabsorbent composite could be as a potential water-saving product used in the agriculture, and the approach reported in this work also can be as a new pathway for high value using of SC via a sustainable chemical engineering process.

Gases emission during the continuous thermophilic composting of dairy manure amended with activated oil shale semicoke

NH3 and greenhouse gases emission are big problems during composting, which can cause great nitrogen nutrient loss and environmental pollution. This study investigated effects of the porous bulking agent of oil shale semicoke and its activated material on the gases emission during the continuous thermophilic composting. Results showed addition of semicoke could significantly reduce the NH3 emission by 74.65% due to its great adsorption capacity to NH4+-N and NH3, further the effect could be enhanced to 85.92% when utilizing the activated semicoke with larger pore volume and specific surface area. In addition, the CH4 emission in the semicoke and activated semicoke group was also greatly mitigated, with a reduction of 67.23% and 87.62% respectively, while the N2O emission was significantly increased by 93.14% and 100.82%. Quantification analysis of the functional genes found the abundance of mcrA was high at the massive CH4-producing stage and the archaeal amoA was dominant at the N2O-producing stage in all the composting groups. Correlation and redundancy analysis suggested there was a positive correlation between the CH4 emission and mcrA. Addition of semicoke especially activated semicoke could reduce the CH4 production by inhibiting the methanogens. For the NH3 and N2O, it was closely related with the nitrification process conducted by archaeal amoA. Addition of semicoke especially activated semicoke was beneficial for the growth of ammonia-oxidizing archaea, causing the less NH4+-N transformation to NH3 but more N2O emission.

Semi-coking of oil shale of the Leningrad deposit

Recently, there has been a growing global interest in processing low-grade types of solid fuels, such as oil shale. In the near future, the role of solid fuels in the country's fuel and energy balance is expected to increase, primarily due to their large reserves. Based on this, this work evaluates the semi – coke obtained by semi-coking low-grade types of solid combustible fossils-oil shale of the Baltic basin (Leningrad deposit). The influence of process parameters (temperature and holding time) on the physical and chemical properties of shale semi-coke was studied experimentally. Based on the data obtained, it is concluded that the obtained samples of semi-coke from oil shale and brown coal can be used as a substitute for coke in various industries and the national economy.

Surface Characterisation of Estonian Oil Shale Semi-Coke

Oil shale is a low-grade fossil fuel that has been used in Estonia mostly for electricity and shale oil production. The conventional use of oil shale results in a vast amount of carbon dioxide emissions urging to find alternative ways for sustainable utilisation of oil shale and develop new technologies. Since oil shale contains relatively high amount of organic matter it should be suitable for producing porous carbonised material (semi-coke) that has high surface area and can be used as an adsorbent in various applications. The aim of this research is to determine the effect of thermal treatment conditions on the specific surface area (SSA) of semi-coke. Estonian oil shale from Ojamaa underground mine was pyrolysed in a batch reactor using different temperatures in the range of 550 to 900 °C and atmospheres (N2 and CO2). The surface properties (BET SSA, pore volume and pore size distribution) of obtained samples were studied using N2 adsorption. The results showed that when the pyrolysis temperature was raised in N2 environment, larger SSA of the sample was obtained – it increased from 12 m2/g (pyrolysed at 550 °C) to 31 m2/g (pyrolysed at 900 °C). At higher temperatures the increase of pores less than 5 nm in diameter was also noticed. The semi-coke samples prepared in N2 environment had larger SSA compared to the ones prepared in CO2.

Effect of oil shale semi-coke on deposit mineralogy and morphology in the flue path of a CFB burning Zhundong lignite

The effect of oil shale semi-coke (SC) on the mineralogy and morphology of the ash deposited on probes situated in the flue path of a circulating fluidized bed (CFB) which burns Zhundong lignite (ZD) was investigated. 10 wt% or 20 wt% SC was added to ZD, which were then combusted in the CFB furnace at 950°C. Two probes with vertical and horizontal orientations were installed in the flue duct to simulate ash deposition. Both windward and leeward ash deposits on probes (P1W, P1L, P2W and P2L) were analyzed by using a scanning electron microscopy with energy dispersive X-ray (SEM-EDX), X-ray diffraction (XRD), an inductively coupled plasma optical emission spectrometry ICP-OES, and a particle size analyzer. When ZD was burned alone, the P1W deposit was comprised of agglomerates (< 30 µm) enriched in CaSO4 and Na2SiO3, incurring significant sintering. The P1L and P2W deposits, however, were of both discrete and agglomerated particles in similar mineral phases but with coarser sizes. The P2L deposit was mainly fine ash particles where Na2SiO3 and Na2SO4 were absent. As SC was added, the agglomerates in both P1W and P1L decreased. Moreover, SiO2 and Ca/Na aluminosilicates dominated the mineral phases whereas Na2SiO3 and Na2SO4 disappeared, showing a decrease in deposit stickiness. Likewise, the P2W deposit was found less spread on the probe, decreasing its deposition propensity. Na-bearing minerals turned into (Na, K)(Si3Al)O8 and (Ca, Na)(Si, Al)4O8 in the P2W deposit. Moreover, Na in the deposits decreased from 32 mg/g to less than 15 mg/g as SC presented. The addition of SC would therefore help alleviate the propensity of ash deposition in the flue path in the CFB combustion of ZD.

Effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke

Diffusion of oxygen in the ash layer usually dominated the combustion of oil shale semicoke particles due to the high ash content. Thus, effective diffusivity of oxygen in the ash layer was a crucial parameter worthy of careful investigation. In this paper, the effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke was measured directly using an improved Wicke-Kallenbach diffusion apparatus. The experimental results showed that higher temperature would lead to a higher effective diffusivity and a thicker ash layer had the negative effect. Especially, the effective diffusivity along the direction perpendicular to bedding planes was much lower than that along the direction parallel to bedding planes. In addition, an effective diffusivity model was developed, which could be used to describe the mass transfer of oxygen in the ash layer of oil shale semicoke.