Coke Layer Research Articles

The design of ignition systems and a study of the development of the high temperature zone in well-type underground coal gasification

To investigate temperature field expansion behavior during the ignition stage, the variation of temperature fields of 12 sites versus time were studied using thermocouples during the ignition process. The results showed that the temperatures measured, and combustion processes, were not uniform. At the position where the igniter had started successfully, igniter 10 showed the smoothest flow in its exhaust holes, followed by igniters 4 and 1, successively. At the position of igniter 10, the ignition materials burned well and the temperature curve was smooth, but the highest combustion temperature of oil-containing split wood layer and coke layer was only 393 °C, the highest combustion temperature of block coal layer and solid coal wall was only 591 °C and 936 °C respectively. At the position of igniter 1, the ignition materials burned inadequately and the temperature curve was rough, but the highest combustion temperatures of oil-containing split wood layer, coke layer, block coal layer and solid coal wall were as high as 960 °C, 983 °C, 899 °C and 1280 °C respectively. The presence of the ignition source ensured, but did not determine, the occurrence of ignition. The temperature field in the gasified area could expand transversely by spreading combustion of the burning front and transverse movement of high-temperature gases to ignite the ignition materials away from fire sources. In locations with high exhaust resistance, the temperature field expanded primarily through the spreading of the burning front, while in the area with low exhaust resistance, the temperature field mainly through expanded the transverse movement of high-temperature gases.

Research of the process of spread of fire on beams of wood of fire-protected intumescent coatings

The article presents the results of the protection of wooden building structures with intumescent coatings for the resistance to high-temperature flame resistance. The essence of the method of determining the effectiveness of the coating was the impact of standardized flames on fireproof wood and the definition of values. Based on the data obtained, criteria were established that correspond to the degree of damage to the specimens and the increase in the combustion temperature, resulting in a decrease in weight loss. To determine the effectiveness of fire protection in the developed coatings studies on the combustibility of wood in terms of weight loss and flue gas temperature were conducted, and it was found that with coating the degree of damage to the samples in length does not exceed 26%, the degree of damage by mass does not exceed 2% and the flue gas temperature does not exceed 115°C. However, a protective layer that is of considerable thickness to the building structure should be applied to ensure its protection, since, at a higher intensity of thermal action, the fire resistance of the wood may decrease due to the formation of a low coke layer. Full-scale tests using model specimens of wooden beams under the action of a high-temperature flame furnace have shown that the intumescent coating can withstand high temperatures, effectively preventing the penetration of heat into the material due to the formation of a swollen coke layer, which affects the speed and depth of the temperature.

Gasification Characteristics and Kinetics of Unburned Pulverized Coal in Blast Furnaces

Pulverized coal injected into a blast furnace (BF) burns incompletely in a very limited amount of time. A considerable amount of unburned pulverized coal (UPC) escapes from the raceway to the coke layer. The unburned pulverized coal reacts with CO2 in the coke layer, and this has a very significant impact on the operation of the BF. The gasification reaction characteristics of the UPC with CO2 were assessed by thermogravimetric analysis. The microstructure and specific surface area of the pulverized coal and UPC were characterized by scanning electron microscopy (SEM), and a specific surface area testing apparatus together with the Brunauer-Emmett-Teller (BET) method, respectively. The results showed that Qingding UPC requires a higher temperature to complete the gasification reaction. At the same heating rate, the Tm (maximum reaction rate temperature) of the Shenhua UPC is much lower and the reaction rate is larger than those of the Qingding UPC. An increased heating rate is beneficial for the gasification reaction of the two UPCs. The kinetics analysis results showed that the optimal mechanism function models for the Shenhua and Qingding UPCs are chemical reaction models. The apparent activation energies of gasification of the Shenhua UPC and Qingding UPC under different conditions were 269.89–223.41 KJ/mol and 266.70–251.54 KJ/mol, respectively.

Flame retarded polyamide-6 composites via in situ polymerization of caprolactam with perylene-3,4,9,10-tetracarboxylic dianhydride

Flame retardant polyamide 6 (PA6) composites (PA6/PTCDA) were prepared by in situ polymerization of caprolactam with adding 0.01–2.5 wt% perylene-3,4,9,10-tetracar-boxylic dianhydride (PTCDA). The structure and properties of PA6/PTCDA composites were studied by Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, thermal conductivity, and limiting oxygen index (LOI) measurements. The results indicated that the crystallization of the PA6 chains was suppressed with 2.5 wt% PTCDA, and the LOI of the composite was 29.5. At the same time, the addition of PTCDA made the composites form a coke layer in the process of combustion, protecting the flammable components from volatilization and enhanced the flame retardant performance of the composites. This indicated that the PA6/PTCDA composite prepared by in situ polymerization possessed good flame retardant properties.

Estimation of fire protection efficiency of articles made from reed under an external action of gasoline flame

Our study into the process of reed ignition has established the mechanisms of heat transfer to a material, which makes it possible to influence this process. It has been proven that the process of ignition implies heating a material to the critical temperature when an intensive decomposition begins with the release of the required amount of combustible gases. Knowing this process makes it possible to determine the efficiency of fire protection and the properties of roofing compositions on the process of reed ignition deceleration. Under a thermal action on fire-proof samples, a swollen layer formed at the surface resulting from the decomposition of the retardants under the influence of the temperature, with the release of non-combustible gases that inhibit the oxidation processes of the material and substantially increase the formation of a thermoprotective layer of coke at the reed surface. This leads to an increase in the thickness of the coke layer and to the deceleration of heat transfer of high-temperature flame to the material. Given this, it has become possible to determine conditions for protecting reed from fire by forming a barrier to thermal conductivity. In addition, when applying a fire-proof coating, temperature influence is carried out in the direction of reactions in a pre-flame area towards the formation of ash-like products at the surface of the natural combustible material. That allows us to argue about feasibility of the established mechanism that forms the properties of fire protection of reed by swelling compositions and about practical significance of the proposed technological solutions. The latter, in particular, relate to determining the amount of a polymeric component as reed is characterized by hydrophobicity and an aqueous solution of the fire retardant flows down from the surface. Adding a PVA-dispersion leads to a decrease in the intensity of washing the flame retardant out of the material by larger than 6...8 times. Our experimental research has shown that when exposed to a gasoline flame the untreated model sample of a thermal insulation mat made from reed ignited on second 205, which led to its complete combustion while the flame-retardant sample did not ignite under thermal action, the flame did not propagate; in this case, we observed the swelling of a protective coating on the area of about 0.028 m2, which reached 3...4 mm. Thus, there is reason to argue about the possibility of targeted control over the processes that protect reed from fire by using an integrated roofing composition of a mixture of fire retardants, which contains a natural polymer capable of forming a fire-protective film on the surface of the material

Modelling coke formation in an industrial ethane‐cracking furnace for ethylene production

AbstractThe development of a model for predicting coke formation in an industrial ethylene cracking furnace is described. Expressions for predicting the rates of catalytic and pyrolytic coke formation are developed and a differential equation is derived to predict changes in coke thickness with time and position. An expression is developed to account for a decline in the rate of catalytic coke formation with increasing thickness of the coke layer. The proposed coke model equations are used to extend a previously developed ethane pyrolysis furnace model that ignored coke. Three model parameters related to coke formation are estimated using industrial data to obtain reliable model predictions. Two of these parameters are coefficients that appear in the catalytic and pyrolytic coke formation rate expressions. The third is a characteristic‐length parameter used to reduce the rate of catalytic coke formation as the coke layer grows. The resulting dynamic model matches the industrial data well and can be used to simulate furnace operation and predict coke thickness profiles over a variety of the operating conditions, thereby helping process engineers who plan the decoking process.

Small ZSM-5 crystals with low defect density as an effective catalyst for conversion of methanol to hydrocarbons

Abstract This work presents the synthesis of nearly defect-free ZSM-5 nanosized crystals, prepared in fluoride medium by seeding with silicalite-1. This material was carefully characterized and its catalytic performances in the methanol to hydrocarbons (MTH) reaction were assessed. Such fluoride-based material was compared to a reference ZSM-5, produced through a conventional alkaline synthesis but from the same seeding. Despite both the materials show closely identical morphology and they have a comparable acid site population, the catalyst prepared using the fluoride route showed significantly longer lifetime in MTH compared to the catalyst prepared using conventional synthesis at high pH. The slower deactivation for the samples prepared using the fluoride route was ascribed, thanks to a thorough in situ IR spectroscopy study, to its lower density of internal defects. According to the UV-Raman characterization of coke on the spent catalyst, the fluoride-based ZSM-5 catalyst produces less molecular coke species, most probably because of the absence of enlarged cavities/channels as due to the presence of internal defects. On the basis of these observations, the deactivation mechanism in the ZSM-5 synthesized by fluoride medium could be mostly related to the deposition of an external layer of bulk coke, whereas in the alkali-synthesized catalyst an additional effect from molecular coke accumulating within the porous network accelerates the deactivation process.

The influence of coking on heat transfer in turbulent reacting flow of supercritical hydrocarbon fuels

Significant influence from coking (aggregation and formation of a non-desirable carbonaceous porous layer on a solid metal surface) on the heat transfer in a cooling system of hypersonic aircraft with hydrocarbon fuel as the coolant is observed. In the present work, an explanation was proposed to understand the influence mechanism of coking on the heat transfer in cooling channel. In addition, a numerical model was further established to verify the explanation by comparing the heat transfer in cooling channel with different thicknesses of coke layer. The results indicated that critical thicknesses of coke layer with respect to effective thermal conductivity (δcl,λc) and heat transfer (δcl,hc) existed. More specifically, the heat transfer was noticeably enhanced when δcl <δcl,hc, while the heat transfer is deteriorated as δcl > δcl,hc. A transition thickness with length of (δcl,hc–δcl,λc) existed between δcl,λc and δcl,hc under the combined influences of convection of core flow and coke layer. By comparing the heat transfer in cooling channel after coke deposit at different inlet Reynolds number, it was further found that δcl,λc and δcl,hc decrease with increasing the turbulent intensity. This implied that the influence of inlet Reynolds number on the coke deposition rate and turbulent heat transfer were dissimilar. This study is expected to provide further insight into the optimization of cooling channel for the purpose of reducing the heat transfer deterioration caused by coke.

Model Study of Blast Furnace Operation with Central Coke Charging

Blast furnace (BF) remains the dominant ironmaking process worldwide. Central coke charging (CCC) operation is a promising technology for stabilizing BF operations, but it needs reliable and quantified process design and control. In this work, a multi-fluid BF model is further developed for quantitatively investigating flow-thermal-chemical phenomena of a BF under CCC operation. This model features the respective chemical reactions in the respective coke and ore layers, and a specific sub-model of layer profile for the burden structure for the CCC operation. The simulation results confirm that the gas flow patterns and cohesive zone’s shape and location under the CCC operation are quite different from the non-CCC operation. Under the CCC operation, the heat is overloaded at the furnace center while the reduction load is much heavier at the periphery regions; the profiles of top gas temperature and gas utilization show bell-shape and inverse-bell-shape patterns, respectively. More importantly, these differences are characterized quantitatively. In this given case, when the CCC opening radius at the throat is 0.35 m, the cohesive zone top opening radius is around 0.50 m, and the isotherms of CCC operation become much steeper (~ 80 deg) than those of non-CCC operation (~ 60 deg) near BF central regions. In addition, it is confirmed that carbon solution-loss reaction rate can be decreased significantly at BF central regions under CCC operation. The model helps to understand CCC operation and provides a cost-effective method for optimizing BF practice.

Heatfireprotection Polymer Coatings on the Basis of EPDM-40 with Additives

Triple ethylene-propylene copolymers (EPDM) are used for the making of structural elements exposed to mechanical loads and are heat-resistant [1, 2], but their widespread use in aviation and shipbuilding equipment and other industries is limited due to Flammability. Double ethylene-propylene rubbers are practically limiting, and triple (EPDM), Dicyclopentadiene is used as the third component, due to the small content of double bonds in the side chains, have high heat resistance compared to diene rubbers [2], and therefore the issues of fire resistance of rubber-technical products based on them remain more and more urgent [3-7]. In [7] it is shown that if the values of the oxygen index (OI) and PP and EPDM are equal 17 % and 18.5 %, respectively, the coke numbers (CN) - 0 % and 0.5 %, and the copolymer is a PP/EPDM = 37,5/62,5 OI increases to 19.5% and CN up to 1.5 %. For copolymer PP / EPDM = 61.5 / 38.5 OI and CN are 21% and 3.4%, respectively, i.e. fire resistance in copolymers does not increase, which is an urgent problem. Polyolefins as it is shown in [7] and other works, at pyrolysis in soft conditions decompose practically without the rest, at thermal blows the mechanism of destruction changes and the carbonized rest is formed. The presence of cross-linked structures in the macromolecules of polyolefins also leads to the appearance of a carbonized residue. In work [8] the formulations of rubber mixtures resistant to wet chlorine, aqueous solutions of sodium hydroxide and sodium chloride, hydrogen, for the production of gaskets for electrolyzers and in [9] the effect of dithiophosphate accelerators on the complex properties of rubbers based on rubber grade EPDM-40. In [10] investigated the effect of a modified alumino-silicate intumescent microfiber filler kaolin microfiber (KMF) on the fire and heat protective properties (FHP) of vulcanizates based on ethylene-propylene-diene rubber EPDM-40. The compositions contained from 3 to 15 Weight Part (W.P.) KMV with a fractional composition of 25-110 microns and a fiber diameter of about 10 microns. As modifiers used a phosphorus boron containing oligomer (FBO), contributing to the increase of fireheat protective properties and multifunctional additive - hexachlor-p-xylene. It has been established that the modification of the kaolin microfiber leads to an improvement in the fire and heat protective properties at high temperature exposure: the rate of linear combustion decreases by 14%, the formation of the coke layer (CL) increases. It is shown that in conditions of erosion ablation, the fire-protective material has a 10 to 15% increase in tearing strength of CL, the time of onset of fire increases by 20-40% and the time of CL separation by 30%. In [ 11 ], the effect of HYPERLINK "https://translate.google.com/translate?hl=ru&amp;prev=_t&amp;sl=ru&amp;tl=en&amp;u=https://elibrary.ru/keyword_items.asp%3Fid%3D12826492" microcarbon fiber, a solution of FBO, HYPERLINK "https://translate.google.com/translate?hl=ru&amp;prev=_t&amp;sl=ru&amp;tl=en&amp;u=https://elibrary.ru/keyword_items.asp%3Fid%3D2483721" elastomers and HYPERLINK "https://translate.google.com/translate?hl=ru&amp;prev=_t&amp;sl=ru&amp;tl=en&amp;u=https://elibrary.ru/keyword_items.asp%3Fid%3D4285142" elastomeric materials on the fire-protective properties of EPDM-40 was investigated. The aim of the study was to investigate the processes of pyrolysis in the condensed phase, improving the properties of incombustibility and the creation of flame retardant rubber based on EPDM-40 for metal constructures.

Effect of Coke Particle Arrangement on Reduction and Gasification Reaction in Mixed Layer of Ore and Coke

To reduce CO2 emissions from steel works, low reducing agent rate (low coke rate) operation of the blast furnace is desired. Mixing nut coke in the ore layer is one effective measure for realizing this type of operation. Therefore, the effect of coke mixing on the reduction reaction rate of ore and the gasification reaction rate of coke in the mixed layer of ore and coke was investigated. The reduction rate of the ore and the gasification rate of the coke in the mixed layer of ore and coke was estimated by a reduction and gasification experiment, and the packing structure of the coke in the mixed layer was estimated by a mathematical model analysis using the discrete element method. The reduction rate of the ore and the gasification rate of the coke in the mixed layer was affected by the degree of contact between the ore and coke. In addition, the reduction rate of the ore and the gasification rate of the coke in the mixed layer was accelerated by the effects of mutual utilization of the gases generated by the reactions.

Design of fire-resistant heat- and soundproofing wood wool panels

The conducted research revealed the possibility to manufacture heat- and soundproofing materials for the arrangement of buildings. Wood fibers, which are produced in the form of flat panels, are the raw materials for their production. The mechanisms for the process of heat- and soundproofing during energy transfer through the material, which enables influencing this process, were established. It was proved that they are related to the porosity of the material. Thus, at a decrease in volume weight of the material, thermal conductivity and sound transmission are reduced, and vice versa. In addition, heat- and soundproofing building materials from wood should meet the following requirements: to have stable thermal insulation and acoustic indicators within the whole operation period and to be fire resistant, not to give off hazardous substances into the environment. Experimental research proved that the material based on wood wool and inorganic binder at the ratio of 1:1 belongs to combustible materials, because there was its smoldering during the temperature exposure. Thus, under thermal exposure for 90 seconds, the sample caught fire, the flame propagated around the first three zones within 41 s. At the same time, an increase in the amount of the binder on inorganic base and application of organic-mineral binder does not lead to the ignition of material, the maximum temperature of flue gases made up around 120 °C and flammability index amounted to 0. This became possible due to the decomposition of fire retardants under the influence of temperature with emitting non-combustible gases, inhibiting the processes of material oxidation and significantly increasing the formation of the heat protective layer of coke on the surface of the material. This leads to inhibition of heat transfer of high-temperature flame to the material. This made it possible to determine the conditions for fire-resistance of the material through the formation of a thermal conductivity barrier. This makes it possible to argue about the relevance of the detected mechanism of formation of properties of the material based on wood wool and inorganic or organic-mineral binder, as well as practical attractiveness of the proposed technological solutions. The latter, in particular, relate to determining the amount of the binder component (the ratio of wood wool to the binder is not less than 1:2), because in small quantities (ratio 1:1), the burning process occurs. Thus, there are the grounds to argue about the possibility of directional regulation of the processes of formation of heat- and soundproofing wood materials through the use of wood wool and the binder. In this case, it was proposed to use the inorganic and organic-mineral coatings as a binder, which can form a fireproofing film at the surface of the material.

Phase and mineral behavior of coke in cohesive zone

The metallurgical coke sample collected from the lower section of cohesive zone was examined by SEM/EDS. It was observed that the outer layer of coke was covered with slag and iron, and the solid solution of Ti(C,N) and V(C,N) was distributed around the slag-iron interface and iron droplets. The composition of the slag was unevenly distributed, mainly the crystalline phases of gehlenite or anorthite. The macroscopic coke pores near the slag-iron layer were filled with a large number of slag, and the interconnected pores generated by severe coke gasification reaction provide effective channels for the liquid slag to flow into the coke. The Fe-rich phase, the Ca-rich phase, and the alkalis element were also observed in the coke. Meanwhile, the octahedral spinel crystals were found in the coke pores, and the stress generated by the growth of spinel crystals may cause the formation of cracks in cohesive zone coke.

Effect of a flame­retardant coating on the burning parameters of wood samples

The studies of influence of wood fire protection on ignition have established parameters of flame propagation and combustion suppression which makes it possible to influence this process. It was proved that fire protection consists in creation of a layer on the material surface which prevents the material from warming up to its critical temperature. Experimental studies confirmed that the untreated wood specimen ignited under thermal action resulting in its combustion with a burnout rate of 18 g/(m2∙s). With an increase in intensity of combustion of the ignition gas mixture by 25 % and 50 %, rate of the specimen weight loss increased by 1.4 times and 1.8 times, respectively. In the case of wood impregnation, the rate of weight loss was reduced to 4.8 g/(m2∙s) due to decomposition of flame retardants under thermal action with release of non-combustible gases which inhibited material oxidation and formed a coke layer. When treating wood with an inorganic coating, a heat-resistant ceramic film is formed on the wood surface which reduces the burnout rate 3.8 times. But with an increase in intensity of combustion of the igniting gas mixture by 50 %, the wood specimen has ignited which was reflected by increase in the weight loss rate. Application of organic-mineral coatings under thermal action has resulted in formation of a layer of foamed coke, inhibition of heat transfer from high-temperature flame and reduction of burnout rate to 3 g/(m2∙s). This has made it possible to determine conditions of change and inhibition of the combustion parameters for fire protection of wood by creation of a barrier for thermal conductivity. The results of comparison of experimental data on the wood burning rate with the derived analytical equations have shown conformity between them. Thus, there are grounds to assert about the possibility of directed regulation of processes of wood fire protection by using flame retardant coatings capable of forming a protective layer on the material surface that reduces the wood burnout rate

Establishment of heat­exchange process regularities at inflammation of reed samples

The conducted studies into the influence of induction period on reed inflammation have established the mechanisms of the process of heat transfer to material which makes it possible to influence this process. It was proved that these mechanisms consist in heating material to a critical temperature at which an intensive decomposition of the material occurs with release of a critical amount of combustible gases and their inflammation. This makes it possible to establish effect of fire protection and properties of roofing formulations on inhibition of the reed inflammation process. Experimental studies have confirmed that untreated reed inflames under thermal action in 58 seconds which is respectively equal to the induction period of material decomposition and flame spreads throughout the material surface which results in a complete combustion of material. Duration of the induction period extends to 587.45 s due to decomposition of flame retardants under thermal action with emission of non-combustible gases inhibiting material oxidation and significantly intensifying formation of a heat protective layer of coke on the reed surface. This leads to a growth of the coke layer thickness and inhibition of heat transfer from high temperature flame to the material. The study has made it possible to determine conditions of fire protection of reed by creating a barrier for thermal conductivity. In addition, when a flame-retardant protection coating is applied, the temperature effect manifests itself in reactions in the pre-flame region with formation of soot-like products on the surface of a natural combustible material. This gives grounds to assert that the mechanism of imparting fire protection properties to the reed by means of bloating formulations is feasible and that the proposed technological solutions have practical attractiveness. The latter, in particular, relate to determination of quantity of the polymeric component since the reed is characterized by hydrophobicity and the aqueous solution of the flame detergent flows off the surface. Thus, there are grounds to assert that the controlled fire protection of reed can be ensured through the use of a complex roofing formulation of a mixture of flame retardants and a natural polymer capable of forming a flame-retardant film on the material surface

A Novel Measurement of Voidage in Coke and Ferrous Layers in Softening and Melting under Load Test Using Synchrotron X-ray and Neutron Computed Tomography

A Novel Measurement of Voidage in Coke and Ferrous Layers in Softening and Melting under Load Test Using Synchrotron X-ray and Neutron Computed Tomography

Reactivity Indices of Polyaromatic Hydrocarbons for the Radical Reactions of Coke Layer Formation on the Visbreaking of Hydrocarbon Raw Materials

The results of the calculation of the reactivity descriptors of structurally different polyaromatic hydrocarbons (PAHs), which act as starting compounds in condensation and polymerization reactions and the subsequent formation of coke occurring on the heating of hydrocarbon raw materials in the course of visbreaking in tube furnaces are presented. The activation energies and preexponential factors of chemical reactions of hydrogen atom removal from PAH molecules, which simulate the local environment of a coke layer, as a result of their interaction with the radical ⋅CH3 were calculated using quantum chemical methods.

Effects of Particle Diameter and Coke Layer Thickness on Solid Flow and Stress Distribution in BF by 3D Discrete Element Method

In order to reduce ironmaking-related CO2 emissions, hydrogen-enriched blast furnace (BF) operation is currently under development. In hydrogen-enriched BF operation, coke layer thickness can be decreased to reduce CO2 emissions. However, BFs operating with thin coke layers may experience instability or discontinuous phenomena such as particle slip and gas channeling problems, so it is important to optimize the particle diameter and coke layer thickness for optimal BF operation. In this study, the effects of particle diameter and coke layer thickness on the solid flow and stress distribution in a BF were analyzed using a three-dimensional discrete element method. Furthermore, the effects of particle diameter and coke layer thickness on the burden layer stabilities, particle velocities, and particle stress distributions have been investigated. The results show that decreasing the coke layer thickness caused instability owing to the mixing of the coke and ore layers in the BF-cohesive zone and slight increases in both the average particle velocities and the average normal particle stress magnitudes. In addition, the average particle velocities and average normal particle stresses were higher for the smaller particles than for the larger ones during the simulations.

Modelling of Blast Furnace with Respective Chemical Reactions in Coke and Ore Burden Layers

The ironmaking blast furnace (BF) is an efficient chemical reactor for producing liquid iron from solid iron ore, where the solids of coke and iron ore are charged in alternative layers and different chemical reactions occur in the two solid layers as they descend. Such respective reacting burden layers have not been considered explicitly in the previous BF models. In this article, a mathematical model based on multi-fluid theory is developed for describing the multiphase reacting flows considering the respective reacting burden layers. Then, this model is applied to a BF, covering the area from the burden surface at the furnace top to the liquid surface above the hearth, to describe the inner states of a BF in terms of the multiphase flows, temperature distribution and reduction process. The results show that some key important features in the layered burden with respective chemical reactions are captured, including fluctuating iso-lines in terms of gas flow and thermochemical behaviours; particularly the latter cannot be well captured in the previous BF models. The temperature difference between gas–solid phases is found to be larger near the raceway, at the cohesive zone and at the furnace top, and the thermal reserved zone can be identified near the shaft. Three chemical reserve zones of hematite, magnetite and wustite can also be observed near the stockline, in the shaft near the wall and near centre, respectively. Inside each reserve zone, the corresponding ferrous oxides stay constantly high in alternative layers; the overall performance indicators including gas utilization efficiency and reduction degree also stay stable in an alternative-layered structure. This model provides a cost-effective tool to investigate the BF in-furnace process and optimize BF operation.

Influence of modifiers on coked foam structure and properties formed with thermal decomposition of wood

Wood is a material that forms a surface layer of coke when burning. Properties of the coke layer significantly impact the fire resistance of structures due to the change of the structure working section reduction rate. This paper discusses the research of how the wood surface layer modifiers influence the structure and properties of the coke layer formed with thermal decomposition of wood. As modifiers have been used phosphorus flame-retardants. To evaluate how the modifiers influence the coke layer formation process, the source and modified samples of pine have been analyzed before and after thermal decomposition using the element analysis, electron microscopy, and adsorption. Thermal analysis has been accomplished using the thermogravimetry (TG), differential thermogravimetry (DTG), and differential scanning calorimetry. To evaluate the fire protection efficiency of the modified wood, fire tests have been accomplished. Such tests were tests to determine the magnitude of weight loss during combustion, flame spread index and the coefficient of smoke-ability. Based on the acquired data, it was identified that when the modifiers are used, and these modifiers enter into efficient superficial chemical reaction with wood under mild conditions, the thermal decomposition occurred under mild conditions - the first stage of thermal decomposition transits to the lower temperatures zone. This reduces the thermal effect of thermal decomposition reaction. There is a decrease in weight loss during thermal decomposition. This results in formation of the strong and structured, thermally stable surface, which is less adsorption ability, specific surface area and porosity reduction. This explains high rate of fire protection and low smoke-generating capacities.