Coke Layer Research Articles

Temperature Programmed Oxidation Coupled with In Situ Techniques Reveal the Nature and Location of Coke Deposited on a Ni/La2O3‐αAl2O3 Catalyst in the Steam Reforming of Bio‐oil

AbstractThe characterization of coke deposited on a Ni/La2O3‐αAl2O3 catalyst used in the steam reforming of bio‐oil has been studied by temperature programmed oxidation (TPO) coupled with different in situ techniques: thermogravimetry (TG), modulated thermogravimetry (MTG), FTIR spectroscopy with mass spectrometry (MS), Raman spectroscopy, and differential scanning calorimetry (DSC). The steam reforming of bio‐oil was carried out in a reactor equipment with two steps in series, comprising bio‐oil thermal treatment (500 °C) and subsequent reforming in a fluidized bed reactor (550–700 °C; and steam‐to‐carbon ratio, 1.5–6). TG/MS‐TPO experiments identify encapsulating and filamentous coke, and a more detailed analysis using other in situ techniques enable to characterize the nature and location of 4 types of coke: (i) an encapsulating coke with aliphatic nature placed in the most superficial layers; (ii) an encapsulating coke with higher aromatic nature in inner layers; (iii) the most superficial layers of a filamentous coke, further from active sites and with a more carbonized structure compared to encapsulating coke; and (iv) an innermost and mainly polyaromatic filamentous coke with a low oxygenates content.

The distribution and migration of sodium from a reclaimed upland to a constructed fen peatland in a post-mined oil sands landscape

Post-mine landscape reclamation of the Athabasca Oil Sands Region requires the use of tailings sand, an abundant mine-waste material that often contains large amounts of sodium (Na+). Due to the mobility of Na+ in groundwater and its effects on vegetation, water quality is a concern when incorporating mine waste materials, especially when attempting to construct groundwater-fed peatlands. This research is the first published account of Na+ redistribution in groundwater from a constructed tailings sand upland to an adjacent constructed fen peat deposit (Nikanotee Fen). A permeable petroleum coke layer underlying the fen, extending partway into the upland, was important in directing flow and Na+ beneath the peat, as designed. Initially, Na+ concentration was highest in the tailings sand (average of 232mgL−1) and lowest in fen peat (96mgL−1). Precipitation-driven recharge to the upland controlled the mass flux of Na from upland to fen, which ranged from 2 to 13tons Na+ per year. The mass flux was highest in the driest summer, in part from dry-period flowpaths that direct groundwater with higher concentrations of Na+ into the coke layer, and in part because of the high evapotranspiration loss from the fen in dry periods, which induces upward water flow. With the estimated flux rates of 336mmyr−1, the Na+ arrival time to the fen surface was estimated to be between 4 and 11years. Over the four-year study, average Na+ concentrations within the fen rooting zone increased from 87 to 200mgL−1, and in the tailings sand decreased to 196mgL−1. The planting of more salt-tolerant vegetation in the fen is recommended, given the potential for Na+ accumulation. This study shows reclamation designs can use layered flow system to control the rate, pattern, and timing of solute interactions with surface soil systems.

ВЛИЯНИЕ МОДИФИКАТОРОВ НА ХАРАКТЕРИСТИКИ ПЕНОКОКСА, ОБРАЗУЮЩЕГОСЯ ПРИ ТЕРМИЧЕСКОМ РАЗЛОЖЕНИИ ДРЕВЕСИНЫ

Introduction. Currently, wood-based construction materials are in high demand in the field of construction around the globe. The study of the original wood composite in order to improve its characteristics through various methods is scientific pre-requisity for such development. When wood burns, it forms a surface coke layer, which can differ in mechanical and thermal stability. These parameters produce a significant effect on the fire resistance rating of building structures due to a change in the reduction rate of the structure useful cross section. Materials and methods. The studies carried out during the work are related to the evaluation of the characteristics of coke layer formed during thermal decomposition of wood. Thermal analysis methods, the scanning electron microscopy method and the water adsorption method were used. The original sapwood of pine, as well as the wood modified with effective fire-retardant agents were used in the course of work. Results. Based on conducted experiments process graphic dependences of thermal decomposition have been obtained, as well as images, obtained by an electronic microscope. In addition, the dependence of adsorptive capacity of wood after thermal decomposition has been obtained. Discussions. As a result of the study, it was found that with the use of modifiers based on organophosphorous compounds, entering into effective reaction with wood, structuring of the surface layer occurs after thermal decomposition while reducing the size of specific surface area of wood. Conclusions. Based on the analysis of experimental data, we can conclude that because of the use of efficient wood surface layer modifiers, thermal decomposition takes place under “mild” conditions that is the shift of the first stage of thermal decomposition to the area of lower temperatures with non-severe exothermic effects. The loss of weight of samples during combustion is significantly reduced. This causes high fire-retardant efficiency and low smoke-generating capacity.

ИССЛЕДОВАНИЕ ВЫСОКОТЕМПЕРАТУРНЫХ СВОЙСТВ ЖЕЛЕЗОРУДНЫХ МАТЕРИАЛОВ В ЛАБОРАТОРНЫХ УСЛОВИЯХ

The aim of the study is to simulate in laboratory conditions the behavior of iron ore materials in the zone of softening-melting DP and drip flow using an integrated method developed at the Institute of Ferrous Metallurgy. It is shown that the widespread idea of the formation in the blast furnace of primary slag melt based on FeO takes place mainly in the initial period of slag formation and is true for low basicity iron ore materials. For pellets, the nature of the formation of liquid phases differs significantly from the agglomerate. Experimentally established changes in the composition of the slag melt as heating. It is shown that under the conditions of temperature and heat treatment of raw materials, each temperature has its own composition of the liquid phase. When the pellets are melted, the primary melt is formed in the temperature range of 1330–13600C, in which the proportion of primary slag is 16–25%. Melt from high-silicon lumpy ore is formed at high temperatures of 1490-15200С. The mass of the primary slag with 42-48% FeO is 4-8% by weight of iron ore materials. The main part of the melt hangs on the coke nozzle on the coke layer at temperatures above 16000C. Melts formed from mixtures of iron-containing materials, as a rule, have averaged characteristics. The observed patterns make it possible to predict the behavior and properties of multicomponent charge mixtures in a blast furnace.

АНАЛИЗ МЕТОДОВ УПРАВЛЕНИЯ ДОМЕННОЙ ПЛАВКОЙ НА ОСНОВЕ ИНФОРМАЦИИ О ФОРМЕ И ПОЛОЖЕНИИ ПЛАСТИЧНОЙ ЗОНЫ

The aim of the work is to formulate recommendations on the adoption of control actions on the course of smelting in modern conditions. The ideology of the modern intellectual decision support system for blast smelting management is based on providing the optimal plastic zone in the blast furnace (DP). Blast furnace melting control methods are based on information on the shape and position of the plastic zone in the blast furnace. According to the results of research carried out by various scientists, it was shown that the plastic zone is a hollow cone, the walls of which consist of alternating horizontal coke layers with high gas permeability and low-permeable for gas layers of iron ore materials that are in a softened, semi-molten state. The work describes the factors that determine the shape and position of the plastic zone in the DP. The analysis carried out showed that the mode of loading of charge materials has the main influence on the formation of the plastic zone. It was noted that, in addition to various modeling methods, it is advisable to create a criterion for assessing the shape and position of the plastic zone, which would take into account its thickness, profile and position in the DP, to control and control the blast smelting process. Developed recommendations for making management decisions during smelting.

Influence of carbon additives on operational properties of the intumescent coatings for the fire protection of building constructions

In work ability of the intercalated graphite entered into the fireproof intumescent compositions to act as catalytically active additive raising operational characteristics of the classical distending coverings intended for fire protection of building constructions. It is established that thermal expanded graphite, as well as nano-additives, increase frequency rate, durability, elasticity, density and uniformity of a coke layer of a fireproof covering for increase of fire resistance of a building construction.

Establishment of the mechanism and fireproof efficiency of wood treated with an impregnating solution and coatings

Description of the behavior of fireproof means and coatings, including those swelling, in the moment of the formation of a thermal insulating structure is a special and complex task. In general, it covers both stages of the process of thermal protection: both heat transfer and subsequent swelling of the coating, which is formed during fire protection. In necessitates studying conditions for the formation of barrier to thermal conductivity and the establishment of a mechanism of fire protection from layer to a layer of coke. Given this, we examined the process of fire protection with work of an impregnating solution and at swelling of a fireproof coating. Data that we obtained revealed that the formation of volatile products under the effect of coating at high temperature occurs with the formation of noncombustible substances. We established experimentally that under the action of heat flow on the fireproof samples, intense release of inert gases occurs, as well as a reduction in the combustible, which leads to the effectiveness of fire protection in reverse order. It was found in the course of conducted tests that the intensity of the formation of noncombustible gases shifts toward elevated temperature with the formation of coked cellular material. Results of determining a swelling capacity of coating for the intumescent system demonstrated that under the influence of high-temperature flow, material combustion and weight loss of the coating is reduced by more than twice due to the formation of high-temperature compounds; in this case, the time to reach a limit temperature grows as well. A coating under the influence of high temperature forms a significant coefficient of swelling, contributes to the formation of a thermal insulating layer of coke, which prevents wood from burning, as well as the passage of high temperature to the material. In general, the efficiency of wood fire protection revealed that the goods belong to the materials that are difficult to combust, which spread the flame over surface slowly and with low smoke-generating capacity. protection means; fire resistance; volatile products; loss of weight; surface treatment; efficiency of protection

Dynamic simulation of fouling in steam cracking reactors using CFD

Recently computational fluid dynamics (CFD) has been successfully applied for the evaluation of the start-of-run performance of three-dimensional (3D) coil geometries in steam cracking reactors. However, determining the full economic potential of a coil involves tracking its performance throughout the run and not only at start-of-run. Therefore in this work a novel method has been developed that allows to assess the most debated characteristic of these 3D coil geometries, i.e. the potential extension of the run length in combination with the evolution of the product yields during the time on stream. An algorithm based on dynamic mesh generation is presented for simulating coke formation in 3D steam cracking reactor geometries, tracking the apparent geometry deformation caused by the growing coke layer. As a proof-of-concept, a Millisecond propane cracker is simulated over the first days of its run length, and this for three different coil designs: a bare tube, a finned tube and a continuously ribbed reactor design. Our simulations show that the ribbed reactors overall outperform the others although in these enhanced tubular geometries the growth of the coke layer is far from uniform. Because of this, the reactor geometry will change over time, which will in turn influence the fluid dynamics, product yields and successive coke formation substantially.

Change of the petrographic composition of lignite during the ex-situ lignite gasification

The study examined the impact of the process of underground gasification on the petrographic composition of lignite from the Turów deposit. The lignite fed into the reactor is mainly xylodetritic and sapropelic lignite.As a result of the gasification process in the reactor, a cavern and lignite residues were formed. The samples collected from the individual areas were subjected to a detailed petrographic analysis. On the basis of petrographic analyzes it can be concluded that lignite is being transformed as a result of thermal gasification process. Transformation areas, closely related to the temperature prevailing in the reactor, are clearly visible. Moving from the cavern, the following areas can be distinguished: ash area, coke area, degassed area containing dried lignite, cracked transversely to stratification and dried lignite area.These areas can be easily correlated with the distribution of temperature in the reactor. A burned out cavern was formed in the place where the temperature exceeded the ignition temperature of lignite (approx. 500 degrees Celsius).The layers of sapropelic lignite were heavily dried and degassed during the gasification process. Both gelification and fusain layers are not observed within these layers.The ash and portions of coked lignite, characterized by the highest temperature and the largest concentration of oxygen, are mainly observed in the fire channel. The examination has confirmed that a large part of coal was only dried. The biggest changes were observed directly at the cavern and in the fire channel. Sapropelic coal has changed to a lesser extent. The changes include drying and partial degassing. In some places, a thin layer of coke can be observed.The most commonly observed transformations include strong gelification and the formation of fusain.

Investigation on Coking Performance with Sulfur / Phosphorous-containing Additive and Anti-coking SiO2/S Coating during Thermal Cracking of Light Naphtha

Coke deposits during thermal cracking of light naphtha in the presence of the sulfur/phosphorous-containing additive and the anti-coking SiO2/S coating were investigated. The structure of the coke layer was studied. The results show that the coke is more amorphous with the additive mass concentration of 200μg.g-1. The additive has altered the microstructure of the coke layer by effecting the dehydrogenation reaction during coke formation. Coke deposits on the SiO2/S coating prepared by atmosphere pressure chemical vapor deposition (APCVD) method are mainly composed of coke granules. The TGA results show that the coke deposits are mainly composed of a small amount of volatile coke and a large amount of hard coke. The results of the low H/C ratios show the highly condensed structure of the coke deposits. When additive is added, inorganic sulfur is mainly formed in the cokes based on the analysis of XPS spectra. Phosphorus in the cokes is in the form of PO43- and phosphide species. The analyses of Raman spectra indicate that the coke deposits formed during thermal cracking are mainly composed of amorphous carbon. Cokes deposited on the SiO2/S coating are more disordered, which may make the decoking operation facilitated.

Simulation of the phase transformation front advancement during the swelling of fire retardant coatings

Description of the intumescent coating behavior at the time of formation of the porous structure is a separate and challenging task, covering both stages of the thermal insulation process: swelling of the coating and subsequent heat transfer which is formed by the swelling. Therefore, there is a need to study the formation conditions of a barrier for heat conduction and reveal a mechanism of phase transition from the coating film to the coke layer. In this regard, the mathematical model of the phase transformation front advancement during the swelling of fire-proof coatings is developed. According to the dependencies, it is found that the front line of the phase transformations of the coating under high temperature passes instantly. It is foundexperimentally that under the action of the heat flux on the samples for a short time at 190÷200 °C, there is an intense swelling of the coating, the height of the expanded foam coke layer increased to 22÷38 mm. As a result of testing, it is revealed that the phase transformation front moves in the direction of high temperature to form foam coke. The foaming front boundary line in the form of a thin layer, which is slightly shifted towards the temperature, divides the coating into two parts. On the one side, there is a swollen coke layer, the outer part of which moves at a certain speed, on the other side – the layer of the source material, where the temperature is not sufficient to start the foaming process and the speed of transformations is zero.

Incident Radiative Heat Flux Based Method for the Coupled Run Length Simulation of Steam Cracking Furnaces

Due to the significant economic penalty associated with decoking steam cracking furnaces, accurate run length predictions are crucial for assessing their techno-economic performance. Therefore, for the first time, a full coupled run length simulation of an industrial naphtha steam cracking furnace was performed using detailed computational fluid dynamics (CFD) simulations for the furnace side. The results show that the unevenly deposited coke layer within the reactors leads to a redistribution of the thermal power over the time on stream, which is beneficial for the uniformity of the coke growth in the reactor. These effects were not observed in traditional standalone run length simulations, which justifies the high computational cost. However, the high computational cost of these CFD iterations can be overcome by using a novel method which correlates the incident radiative heat flux (IRHF) to the flue gas bridge wall temperature obtained from an overall zero-dimensional heat balance. This so-called IRHF ...

Development and study of elastomer heat-shielding materials containing zirconium dioxide

The effect exerted by introduction of a combination of zirconium dioxide and thermally expanding graphite on the structure of the coke layer of an elastomer fireproofing and heat-shielding material based on ethylene–propylene rubber was studied. The presence of acute angles on the surface of a zirconium dioxide particle enhances its physicochemical activity in sorption (owing to excess surface energy) and promotes coking at high temperatures.

The effects of calcium and potassium on CO2 gasification of birch wood in a fluidized bed

Birch wood was leached of its naturally occurring ash forming elements and doped with three concentrations of calcium or potassium before being gasified in a laboratory bubbling fluidized bed reactor. The wood samples were pelletized and inserted into a fluidized bed reactor where they were first pyrolyzed with N2 and then gasified with CO2. In addition to tracking the gas concentration of the exit gas, char samples were taken from the fluidized bed and analyzed to study the char properties. The presence of potassium in the biomass was found to have a significant influence on the structure of the resulting char, however potassium did not have an observable catalytic effect on the overall gasification reaction rate with CO2 due to the formation of a unreactive coke layer on the char surface. In contrast, calcium did increase the char conversion rate and is likely the primary active catalyst in gasification of birch wood with CO2.

Physicomechanical, thermal, and flame-retardant properties of elastomer compounds based on ethylene–propylene–diene rubber and filled with hollow aluminosilicate microspheres

The effect of hollow aluminosilicate microspheres on the Payne effect and on physicomechanical, thermal, fire-retardant, and heat-protecting properties of elastomer compounds based on ethylene–propylene–diene rubber was studied. Based on the results obtained, the mechanism of the interaction of the elastomer matrix with the microspheres was suggested. Enhancement of the filler–matrix and filler–filler interaction favors additional three-dimensional cross-linking, which influences the set of the physicomechanical and thermal properties, and manifestation of the reinforcing effect in a coke layer under the conditions of erosion removal and detachment of the material with a high-velocity gas flow.

Dripping and evolution behavior of primary slag bearing TiO2 through the coke packed bed in a blast-furnace hearth

To investigate the flow of primary slag bearing TiO2 in the cohesive zone of blast furnaces, experiments were carried out based on the laboratory-scale packed bed systems. It is concluded that the initial temperature of slag dripping increases with decreasing FeO content and increasing TiO2 content. The slag holdup decreases when the FeO content is in the range of 5wt%–10wt%, whereas it increases when the FeO content exceeds 10wt%. Meanwhile, the slag holdup decreases when the TiO2 content increases from 5wt% to 10wt% but increases when the TiO2 content exceeds 10wt%. Moreover, slag/coke interface analysis shows that the reaction between FeO and TiO2 occurs between the slag and the coke. The slag/coke interface is divided into three layers: slag layer, iron-rich layer, and coke layer. TiO2 in the slag is reduced by carbon, and the generated Ti diffuses into iron.

Estimation of the structure-related share of radiation heat transfer in a carbonised packed coal bed

The contribution of radiation to heat transfer in a packed bed of coal during its thermal decomposition in a coke oven chamber has been investigated. The phenomenon was analysed while considering the structure change that the coal experiences. The study focused on the increased role of radiation in the processing stage following coal re-solidification. This is when the macrocracks begin to propagate. A simple fissure development model was proposed to describe the influence of varying textures of coke oven charge on the heat transfer process. The results show that the length of fissures penetrating the coke layer perpendicularly to an oven wall is the main factor affecting heat transport due to radiation. This leads to a significant increase in effective thermal conductivity of the coke layer. The work underlines an anisotropic character of thermal radiation in carbonisation beds.

Modelling of Coke Layer Collapse during Ore Charging in Ironmaking Blast Furnace by DEM

A technical issue in an ironmaking blast furnace operation is to realize the optimum layer thickness and the radial distribution of burden (ore and coke) to enhance its efficiency and productivity. When ore particles are charged onto the already-embedded coke layer, the coke layer-collapse phenomenon occurs. The coke layer-collapse phenomenon has a significant effect on the distribution of ore and coke layer thickness in the radial direction. In this paper, the mechanical properties of coke packed bed under ore charging were investigated by the impact-loading test and the large-scale direct shear test. Experimental results show that the coke particle is broken by the impact force of ore charging, and the particle breakage leads to weaken of coke-layer strength. The expression of contact force for coke in Discrete Element Method (DEM) was modified based on the measured data, and it followed by the 1/3-scaled experiment on coke’s collapse phenomena. Comparing a simulation by modified model to the 1/3-scaled experiment, they agreed well in the burden distribution.

Investigation of Payne effect in heat protective materials containing microspheres modified by element organic modifiers.

The paper considers the impact of the introduction of alumino silicate microspheres on value of the effect Payne and physico-mechanical properties of the elastomer compositions used in the thermal protective materials. It has been shown that the use of pre-modified microspheres can increase the degree of interaction between the rubber-filler. It is found that increasing the filler-filler interaction contributes to the formation of additional spatial crosslinks exerting a reinforcing effect in the coke layer under conditions ablation erosion and breaking of the material the high velocity gas stream.

Evaluating Effect of Coke Layer Thickness on Permeability by Pressure Drop Estimation Model

Evaluating Effect of Coke Layer Thickness on Permeability by Pressure Drop Estimation Model