Content Of Coke Research Articles

Effects of Furnace Slope and Rotational Speed on the Carbothermic Reduction of Celestite in a Laboratory-Scale Rotary Kiln Furnace

The carbothermic reduction of celestite is the first step in producing many strontium products. The way materials move in the rotary kiln has an essential effect on the carbothermic reduction efficiency as well as the temperature. In this study, the reduction of celestite ore and excess carbon blend in a laboratory-scale rotary kiln was investigated. In the experiments carried out at three different temperatures, the rotational speed and slope of the furnace tube were altered, and their effects on the reaction efficiency were examined. The leachability of the reduced powders and the content of the unburned coke indicated the optimal parameters for the reaction. When the speed was increased to 10 rpm, the powders were more mobile in the stack and could react more easily with the furnace atmosphere. According to the results, celestite can be reduced by carbon at temperatures of 1000–1200 °C, at rates of between 5% and 75%. The maximum reaction yield (75%) was obtained with a slope of 2° and a rotational speed of 6 rpm at 1100 °C.

New Strategy toward Household Coal Combustion by Remarkably Reducing SO2 Emission.

A large amount of sulfur dioxide (SO2) will be released during rural household coal combustion, causing serious environmental pollution. Therefore, it is very urgent to develop a clean and efficient fuel to substitute rural household coal controlling SO2 emission. In this paper, a new strategy toward scattered coal combustion with remarkably reducing SO2 emission was proposed. Coal and compound additive of Al2O3 and CaCO3 were blended and then copyrolysis at 1050 °C was performed to produce clean coke. First, the sulfur content of clean coke was reduced, meanwhile, generating sulfur fixation precursor during pyrolysis. Then, clean coke is used for efficient sulfur fixation during the subsequent combustion process to reduce SO2 emissions. The effects of combustion temperature, Al/S molar ratio, and the mechanism of sulfur retention during clean coke combustion were studied in the tube furnace and muffle furnace. The mechanism can be attributed the following reason: (a) CaS produced during pyrolysis and CaO decomposed by complex additives were oxidized during combustion, and CaO captured the SO2 released from clean coke combustion, which formed CaSO4. (b) CaSO4 reacts with Al2O3 to produce calcium sulfoaluminate at high temperatures, which improves the sulfur fixation efficiency of clean coke combustion at high temperatures. In a word, this new strategy can greatly reduce the emission of SO2, thus helping to solve rural household coal pollution problems.

Effect of heat treatment on desulphurization of petroleum coke

Calcined petroleum coke (CPC) is one of major constituent used for making graphite electrodes. Increasing demand of graphite electrodes requires more and more quantity of high quality-low sulphur calcined petroleum coke. The sulphur content of the petroleum coke strongly depends on the nature of the coking feed stock (crude oil) and its sulphur content. High sulphur coke (>1%) is not desirable for making graphite electrodes because evolution of sulphur causes puffing in the temperature range of 1,400-2,200 °C during graphitization. In this study, attempt has been made to reduce the sulphur of calcined petroleum coke by heat treatment to the acceptable level for making graphite electrodes. A high sulphur coke (approx. 2%) was heat treated up to 1,800 °C in inert atmosphere in order to reduce the sulphur content. It was observed that most of the sulphur goes off up to 1,800 °C. A sample of size 12x80 mm was prepared (by extrusion method) from desulphurized petroleum coke using coal tar binder pitch as binder at 125 °C. The extruded samples were carbonized at 900 °C, followed by graphitization at 2,900 °C. The graphitized rods were characterized for various properties such as apparent density (AD), electrical resistivity (ER), flexural strength (FS) and compared with the properties of samples made from electrode grade CPC.

Role of Coke in the Passive Properties of Vitallium 2000 CoCrMo Casting Alloy in Simulated Oral Environment

The passive behaviors of Vitallium 2000 CoCrMo casting alloy in artificial saliva (AS) and Coke were studied by potentiodynamic polarization, electrochemical impedance spectroscopy, cyclic voltammetry, Mott–Schottky combined with scanning electron microscopy, Auger electron spectroscopy, and x-ray photoelectron spectroscopy surface analysis. The results show that with the increasing content of Coke, the self-corrosion current density of alloy increased sharply, the passive film corrosion resistance showed the best in AS and worst in Coke, and the Rp in Coke is reduced to half of that in AS. The thickness of passive films in AS, AS + Coke, and Coke is about 4.5, 3, and 2.5 nm, respectively. Passive films all exhibit n-type semiconductors; with more defects, the carrier density in Coke is 2.3 times more than that in AS. The Coke inhibits the oxidation of Co, Cr, and Mo, and the Co/Cr rate and Cr6+ concentration within the passive film increase. Coke weakens the formation process of protected oxides, thus reducing the stability of alloy’s passive film.

Experimental investigation of process parameters during graphitization of catalytic coke

The aim of this project is studying the effect of thermal operation parameters on the graphitization of self-diffused ethane-based catalytic coke. The novelty of this study refers to self-diffused metals that had given unique properties to the catalytic coke and had improved the graphitization degree at low temperatures. The main feature of this research is presenting a remarkable energy saving approach that uses low-cost installations for production of graphitized carbon. The experiments were performed in two steps including preparation of self-diffused ethane-based catalytic coke and then low-temperature graphitization of coke samples below 1500 °C. Characteristic tests were performed by determination of electrical resistivity and XRD pattern of graphitized samples including graphitization degree, aromaticity, coke rank, number of carbon rings, graphene thickness and length. The results revealed that the blanket atmosphere, final temperature and exposure time had the greatest impact on the aforementioned criteria, while the role of thermal ramp and sulfur content of catalytic coke was negligible. The electrical resistivity tests on the graphitized sample showed how the electrical resistivity of graphitized samples is a function of graphitization degree.

Study on the Influence Factor of Coke Pulverization Rate and Its Effect on Operating Index of Large Blast Furnace

The carbon dissolving reaction is the main factor for the deterioration of coke in the blast furnace. Therefore, in order to investigate the effect of coke deterioration on the permeability of blast furnace, the Coke Pulverization Rate (CPR) which represented the degree of Matrix carbon loss after carbon dissolution was put forward in this paper. The results showed that the CPR increases with the increase of volatile of coal blending, ash content of coke, M10 and coke reactivity index (CRI), while decreases with the rising of M40 and coke strength after reactivity (CSR). Analysis of the production data of 5BF blast furnace of Meishan Steel showed that under the conditions of coke ash (Ad) 87%, CRI 66%, the CPR would be less than 23%, which is conductive to ensure stable permeability large blast furnace.

Improvisation of Coke Quality by Co-Carbonization of Vacuum Residue and Bio Oil: A Batch Process

Effects of feed properties during co-carbonization of vacuum residue (VR) and bio oil feed mixed in different proportions in a batch reactor at temperature range of 480°C-490°C and at atmospheric pressure on coke lumps produced after reaction was studied and proposed based on experimental results obtained. Detailed experimental study was done on co-carbonization process of bio-oil and vacuum residue mixed in different proportions in an experimental setup capable of producing solid coke comparable to that produced in commercial delayed coker which helps to study effects of parameters like temperature and pressure on product properties. Product yield and specifications of products and feed were recorded and studied in terms of thermogravimetric analysis. Coke produced was analyzed as compared to Anode grade coke, for its spongy appearance and catalogued based on its properties when compared with anode grade coke. Addition of bio oil to vacuum residue up to 1:1 indeed ameliorate the hardness of coke and reduce the VCM content of coke, transforming it to better quality sponge coke and can be used as anode grade coke. Coke yield was improved by increasing micro carbon residue (MCR) weight percentage. Additionally, asphaltene content of feed directly contribute to solid product yield and gas yield reinforce the anisotropy of coke formed that govern the coke quality. Bio-oil enhance the gas yield till 1/1 mixture required to improve the coke quality.

Moisture Content of Wet-Quenched Coke

Analysis of the factors that significantly affect the moisture content of wet-quenched coke provides the basis for measures to stabilize the moisture content at all stages of the process: in the formulation, preparation, and coking of the coal batch and subsequent treatment of the coke. Those measures include the use of batch compositions, preparation techniques, and coking parameters such that uniformly conditioned coke with reasonable levels of porosity and specific surface is produced; uniform intake of coke in the charging car; sprayer configurations in the quenching tower such that the whole coke charge in the charging car is uniformly cooled; appropriate adjustment of the pumps, sprayers, and other equipment in the quenching tower; quenching by means of biochemically treated water without excessive organic pollutants; strict compliance with the quenching conditions (quenching time and residence time of the coke-filled car beneath the quenching tower); uniform distribution of the coke on the ramp; specified holding time of the coke on the ramp since shortening of that time is accompanied by exponential rise in moisture content; systematic identification of incompletely quenched coke on the ramp and its correction by manual quenching on the ramp and automatic quenching during coke transportation for sorting; and the use of air holes in the bunkers holding the blast-furnace coke so as to stabilize its moisture content.

Development of a Novel Shaft Dryer for Coal-Based Green Needle Coke Drying Process

The industry of coal-based green needle coke develops rapidly in recent years. The green coke produced by the delayed coking process usually has a moisture content of 10%–25%, which damages the calcining kiln and needle coke quality. A standing dehydration tank is currently used to reduce the moisture content of green coke. However, this process has several weaknesses such as unstable operation, large land area occupation, and low productivity. To solve this issue, a novel drying system with a shaft dryer proposed in this work is suitable for green coke drying. Moreover, the performances of the green coke are investigated to design the proposed shaft dryer. The experimental result shows that the average vertex angle of the pile of green cokes is 109.2°. The pressure drop of the dryer increases linearly with the green coke bed height, and the green coke with a larger size has a smaller pressure drop. The specific pressure drops are 5714, 5554, 5354, and 5114 Pa/m, with median green coke sizes of 26.85, 29.00, 30.45, and 31.80 mm, respectively. Tooth spacing is another important parameter which influences the mass of green coke leakage. The optimal tooth spacing and rotary speed of the rollers are determined by the required production yield.

Microstructural Evolution of Blast Furnace Coke During Experimental Heating \u2014The IFORS Approach

Blast furnace coke has been experimentally heated between 850 °C and 1100 °C by varying the gas composition and the alkali content of the raw coke. Raman spectroscopy and “Iterative Fitting of Raman Spectra” (IFORS) evaluates the microstructural change of coke during the experiments. The obtained results indicate a significant microstructural variation within a bulk sample. This variation controls significantly the coke quality as estimated from standard experiments (23.9 < CRI > 38.3). A bulk sample with a CRI value <30 is composed dominantly of lumps showing a relatively low structural ordering. During experimental heating, the structural ordering of such lumps increases. A bulk sample with a CRI value >30 is composed dominantly of lumps showing a relatively high structural ordering. During experimental heating, the structural state of such lumps remains unchanged unless a strong reaction is induced by adding alkaline elements. It is supposed that, under laboratory conditions, thermal and chemical energy, affecting a microstructurally low-ordered coke, first reorganizes the structural state of the individual coke lumps, retarding the onset of the Boudouard reaction.

Coke deposition and product distribution in the co-cracking of waste polyolefin derived streams and vacuum gas oil under FCC unit conditions

The effect of co-cracking of high-density polyethylene (HDPE) or its pyrolysis wax together with vacuum gasoil (VGO) has been studied. The aim is to determine the content, nature, and location of coke while analyzing the impact on product distribution in the process. Four different feeds were used (VGO, VGO + 5 wt% HDPE, VGO + 20 wt% of wax, and 100 wt% wax) in experiments performed in a laboratory-scaled riser simulator, with similar conditions to those of the fluid catalytic cracking (FCC) unit: equilibrium catalyst; 530 °C; catalyst/feed mass ratio, 5; contact time, 6 s. The results of the different characterization techniques of the deactivated catalyst and the coke indicate that the catalyst fouling decreases notably by incorporating these waste streams, changing its nature to a more aliphatic (olefinic) one and its location towards the zeolite micropores. On the contrary, the coke formed from the VGO is more evolved and mainly constituted by polyaromatic components deposited on the mesopores of the catalyst matrix. Product distribution is also affected, increasing the yield of light cycle oil and keeping a relatively similar gasoline yield, with greater olefinity and lower aromaticity. Thus, the FCC shows great perspectives to valorize polyolefins, present in waste plastics, at great scale.

Desulfurization of high sulfur petroleum coke by molten caustic leaching

Desulfurization by molten caustic leaching (MCL) at 400–500 °C has been investigated in order to reduce the sulfur content of petroleum coke. Effective parameters on desulfurization of petroleum coke, other than temperature, include alkali to feed (petroleum coke) mass ratio, time and mesh size in the ranges of 0.5–1.5, 1–3 h and 200–600 µm, respectively. In this work, petroleum coke desulfurization conditions using solid KOH have been studied. Maximum petroleum coke desulfurization by MCL method has been obtained by Taguchi L9 design using alkali to feed mass ratio of 1, temperature of 600 °C, time of 2 h and mesh size of 200 µm. The changes in the main groups on the coke surface have been determined using FTIR spectroscopy. In addition, SEM-EDX, TGA and XRD analyses have been used to investigate the changes in coke physical and chemical properties.

Effects of Coke Ash on Erosion of Carbon Composite Brick

Carbon composite brick has attracted increased attention because it is widely used on the hot face of blast furnace hearth. In order to reduce the erosion rate of carbon composite brick and investigate effects of coke ash on the erosion of carbon composite brick, the minerals CaO.Al2O3, CaO.2Al(2)O(3), and CaO.6Al(2)O(3) (CA, CA2, and CA6), which were considered to be the main components of coke ash in hearth, were prepared by heating a mixture of CaCO3 and Al2O3. Experiments of the minerals coupled with carbon composite brick were carried out at different temperatures in a high temperature tube furnace. The mass change fraction of the experimental assembly was calculated using mass measurements before and after the experiment. The reaction products at different temperatures were predicted on the basis of ternary phase diagrams, and the thickness of the reaction layer was measured using scanning electron microscopy (SEM). The results show that the reaction rate of carbon composite brick with the minerals increased with an increase of the Ca content in the minerals. The results of reaction interface analysis show that the diffusion of Ca2+ was the dominant process during reaction. Cation diffusion was considered to be the rate determining step, and this was in agreement with experimental results. Therefore, reducing the ash content of coke, especially the CaO in ash, is the key to reduce the erosion rate of carbon composite bricks below the centerline of taphole.

Study on the Influence of Coal Blending with Waste Rubber on Coke Quality

In order to investigate the influence of coal blending with waste rubber on coke quality, the pyrolysis performance of rubber powder was analyzed, and the coking experiment of coal blending was carried out in 70 kg test coke oven. The experimental results showed that the pyrolysis range of waste rubber was similar to that of blended coal by analyzing the pyrolysis characteristics of waste rubber. The ash content (Ad), coke reactivity index (CRI) and coke strength after reactivity (CSR) would decrease, while the sulfur content (St, d) of coke would increase with the increasing of coal blending ratio of waste rubber. The specific surface area of coke increased from 1.5m2/g to 3.5m2/g, the Lc of coke microcrystalline structure and the degree of graphitization decreased gradually with increasing the ratio of waste rubber from 0% to 6% in coal blending. The optical structure of coke showed that the fine-grained mosaic structure increased and the degree of anisotropy of coke (OTI) decreased.

Effects of Environmental Humidity on the Moisture Content of Casting Coke

The sensitivity of foundry coke to changes in its moisture content depending on the humidity of the environment was studied. The experimental results showed that an increase in the humidity of the environment led to an increase in the amount of moisture in the foundry coke, which led to the loading of about 10 kg of moisture for every 100 kg of coke into the cupola. In this case, an increase in the moisture content of foundry coke of size 60–80 mm was greater, on average, by 26% than that of coke of sizes 40–60 and 80 mm or more.

Hydrotreating of Mixtures of Straight-Run Diesel Fraction with Coker Gas Oil over Modified Co(Ni)-Mo/Al2O3Catalysts

The effect from the P2O5 introduction on the activity of Co(Ni)-Mo/Al2O3 catalysts in hydrotreating reactions of petroleum feedstock was examined. As support served γ-Al2O3, prepared from aluminum hydroxide AlOOH powder TH-60 (Sasol), with the following textural characteristics: SBET = 205 m2/g, Vpore = 0.682 cm3/g, Reff = 48 A. In order to optimize the amount of the modifier the catalyst samples were modified with 0.5, 1.0, 2.0, and 5.0 wt % P2O5. The support was impregnated with an aqueous solution of H3PO4, and this was followed by drying and calcination. The modified supports were impregnated with an aqueous solution of the active phase precursors. The catalyst samples were examined by temperature-programmed desorption (TPD) of ammonia; they were sulfided before the tests. Their catalytic properties were studied in a micro-flow bench-scale reactor under hydrogen pressure in the hydrotreating reactions of mixtures of straight-run diesel fraction with light coker gas oil and of straight-run diesel fraction with catalytically cracked light gas oil. The activities of the catalysts were determined in hydrodesulfurization and hydrogenation reactions. After the test the catalysts were subjected to differential thermal analysis in combination with thermogravimetry (DTA-TGA). The relationship between the acidity of the oxide form of the catalysts and the catalyst activity in hydrogenation reactions was demonstrated. The influence of the amount of the modifier introduced on the catalyst activity and the content of coke on the catalysts after the test was elucidated.

An investigation of the recovery and kinetics during the flotation of residual petroleum coke in lime calcination exhaust tailings

ABSTRACT Flotation is one of the feasible separation methods suggested for recovery of petroleum coke from the tailings of lime calcination furnaces. In this study, analyses of ash content and calorific value of petroleum coke in lime calcination tailings were used to measure its floatability and product quality. In addition, seven most common flotation kinetics models were fitted to the obtained experimental data. Based on the maximum recovery, minimum ash content, and maximum calorific value of the flotation products, optimum dosages for collector (kerosene) and frother (MIBC) were found 30 g/t and 60 g/t, respectively. Regarding the flotation kinetic modeling and the obtained sum of squared errors (SSEs), Agar and Klimpell models were found to have the best and the poorest fits to the experimental data, respectively. Finally, it was concluded that new statistical concepts such as information criteria (IC) and non-linear generalized least squares estimation (NLGLSE) must be applied to the process of model selection owing to consideration of goodness of fit, complexity of a model and model consistency.

Carbothermic reduction of Electric Arc Furnace Dust via thermogravimetry

Abstract Electric Arc Furnace Dust (EAFD) is a solid waste originated from electric steelmaking furnaces. Currently, according to some authors, there is an estimated generation of 15 to 25 kg of dust per ton of steel produced. The formation of the dust is related to the following steps of the process: furnace charge, metal volatilization, iron vaporization under the arc, drag of solid particles and, mainly by the collapse of CO bubbles from metallic bath decarburation. The dust has metals that are harmful to the environment. Otherwise, it is mostly composed of the elements iron, zinc and oxygen. Due to increasing costs for disposal and because it is considered a hazardous waste, industry is looking at the possibility of returning the dust to the steelmaking process. One of the alternatives is by reintroducing the waste in an electric melting shop using self-reducing agglomerates as part of the furnace burden. In this study, self-reducing mixtures are prepared with EAFD and petroleum coke (PET), presenting chemical and physical characterizations. An evaluation about the behavior of the mixtures is carried out in thermobalance, regarding the possibility of use in measuring accurate PET content in self-reducing pellets. As results it could be stated that the elements of economic interest, Zn and Fe, represent, respectively, 34.23 and 22.80%, in weight. These elements are present in chemical species frankilinite, zincite and magnetite and the reducible oxygen was estimated as 17.90%. Also, it was concluded the optimal content of petroleum coke in the mixtures varies from 10 to 15%, in weight. Therefore, the utilization potential of the thermogravimetric technique in the industrial field for adjustment of carbon content in batches of self-reducing pellets is satisfactory.

Determination of Moisture Content in Coke with 239Pu–Be Neutron Source and BGO Scintillation Gamma Detector

A series of experiments has been conducted at the Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research (JINR) in order to study the possibility of determining the moisture content of coke using a standard neutron source. The proposed method is based on a measurement of the spectrum of prompt γ rays emitted when samples are irradiated by fast and/or thermal neutrons. The moisture content is determined from the area of the peaks of characteristic γ rays produced in the radiative capture of thermal neutrons by the proton (Eγ = 2.223 MeV) and inelastic scattering of fast neutrons by 16O (Eγ = 6.109 MeV). The 239Pu–Be neutron source (〈E n 〉 ~ 4.5 MeV) with an intensity of ~5 × 106 n/s was used to irradiate the samples under study. A scintillation detector based on a BGO crystal was used to register the characteristic γ radiation from the inelastic fast neutron scattering and slow (thermal) neutron capture. This paper presents the results of humidity measurement in the range of 2–50% [1, 2].

Intensification of the processes of dehydrogenation and dewaxing of middle distillate fractions by redistribution of hydrogen between the units

The dehydrogenation and dewaxing of hydrocarbons of middle-distillate fractions, which proceed in the hydrogen medium, are of great importance in the petrochemical and oil refining industries. They increase oil refining depth and allow producing gasoline, kerosene, and diesel fractions used in the production of hydrocarbon fuels, polymer materials, synthetic detergents, rubbers, etc. Herewith, in the process of dehydrogenation of hydrocarbons of middle distillate fractions (C9–C14) hydrogen is formed in the reactions between hydrocarbons, and the excess of hydrogen slows the target reaction of olefin formation and causes the shift of thermodynamic equilibrium to the initial substances. Meanwhile, in the process of hydrodewaxing of hydrocarbons of middle distillate fractions (C5–C27), conversely, hydrogen is a required reagent in the target reaction of hydrocracking of long-chain paraffins, which ensures required feedstock conversion for production of low-freezing diesel fuels. Therefore, in this study we suggest the approach of intensification of the processes of dehydrogenation and dewaxing of middle distillate fractions by means of redistribution of hydrogen between the two units on the base of the influence of hydrogen on the hydrocarbon transformations using mathematical models. In this study we found that with increasing the temperature from 470 °C to 490 °C and decreasing the hydrogen/feedstock molar ratio in the range of 8.5/1.0 to 6.0/1.0 in the dehydrogenation reactor, the production of olefins increased by 1.45–1.55%wt, which makes it possible to reduce hydrogen consumption by 25,000 Nm3/h. Involvement of this additionally available hydrogen in the amount from 10,000 to 50,000 Nm3/h in the dewaxing reactor allows increasing the depth of hydrocracking of long-chain paraffins of middle distillate fractions, and, consequently improving low-temperature properties of produced diesel fraction. In such a way cloud temperature and freezing temperature of produced diesel fraction decrease by 1–4 °C and 10–25 °C (at the temperature of 300 °C and 340 °C respectively). However, when the molar ratio hydrogen/hydrocarbons decreases from 8.5/1.0 to 6.0/1.0 the yield of side products in the dehydrogenation reactor increases: the yield of diolefins increases by 0.1–0.15%wt, the yield of coke increases by 0.07–0.18%wt depending on the feedstock composition, which is due to decrease in the content of hydrogen, which hydrogenates intermediate products of condensation (the coke of amorphous structure). This effect can be compensated by additional water supply in the dehydrogenation reactor, which oxidizes the intermediate products of condensation, preventing catalyst deactivation by coke. The calculations with the use of the model showed that at the supply of water by increasing portions simultaneously with temperature rise, the content of coke on the catalyst by the end of the production cycle comprises 1.25–1.56%wt depending on the feedstock composition, which is by 0.3–0.6%wt lower that in the regime without water supply.