High-speed Heating Research Articles

DETERMINATION OF THE FEATURES OF THERMAL DECOMPOSITION OF SUNFLOWER HUSK IN A FLUIDIZED BED

Sunflower husk (SH) is a plant waste fuel. The carbon content in different samples of SH ranges from 40.5% to 54.5% in an operating state, with ash content ranging from 1.5% to 8.5%, moisture content ranging from 6.9% to 9.5%, chlorine content ranging from 0.05% to 0.3%, and lower heating value ranging from 14.5 MJ/kg to 20.5 MJ/kg. These characteristics make it a suitable substitute for fossil fuels in power boilers. Waste-to-energy (WTE) technologies are rapidly developing worldwide, offering the potential for generating renewable energy from waste, including agricultural and food industry waste such as SH. According to our estimates, Ukraine has an annual energy potential of approximately 3.4 million tons of SH or about two million tons of fuel equivalent. Approximately half of this volume is currently being burned in oil extraction plants' boilers; however, up to one million tons of SH end up in landfills annually, resulting in significant energy losses. To develop new and improve existing WTE technologies that utilize SH as a fuel source, it's essential to understand the thermal processing characteristics of SH under conditions similar to those found in different zones within real power boilers - specifically the heating of fuel particles at rates up to 500 °C/s over a temperature range of 500–1000 °C. In this study, we aimed to investigate the thermal processing characteristics by subjecting SH particles within a laboratory fluidized bed reactor to high-speed heating within the aforementioned temperature range. During rapid heating between 500–1000 °C temperatures range, SH particles undergo conversion into volatile compounds and solid carbon residue. Two distinct stages can be observed on the dynamic yield curves for volatiles. The release and burnout of volatiles occurs during the first stage while the second stage involves coke ash residue burnout. We obtained empirical temperature-dependents for total heat treatment time and carbon residue burnout time under fast heating conditions in the investigated temperature range. The stage of carbon residue combustion is the most enduring and determines the overall duration of thermal treatment. This stage determines the degree of fuel transformation, especially in cases where low-reactivity carbon residue enters the low-temperature combustion chamber area of the boiler. The obtained regularities have practical significance in designing combustion chambers for thermal processing of sunflower husk.

Design of a new fast heating device in wireless portable water dispenser in the age of intelligence

Abstract In our daily life, the quickness of water dispensers provides great convenience for our life. By examining the PID control system and fuzzy control system, a fuzzy PID controller has been designed. This system can be used for both automatic and manual parameterization. The problem that the stable operation of the temperature controller cannot be guaranteed in the PID controller has been solved. In this paper, the designed extreme heating and temperature regulation system is installed in the controller of the wireless portable water dispenser to analyze the effects of using this new product. Comparative experiments indicate that the wireless portable water dispenser with a heating and regulating system has an average hot water production capacity of 3.68L/H, which is higher than the standard value of 3.0L/H. The high-speed heating and regulating system in the wireless portable water dispenser shows that it has a better heating capacity than the ordinary wireless portable water dispenser. Based on the regression analysis of this new product on the basis of user satisfaction, the overall innovativeness of the product = 0.62*usability + 0.032*emotion + 0.056*functionality. The “Usability” construct has the best predictive power with 62% explanation. It indicates that the demand for the product is high among users.

Oxygen-free resistance heating with nitrogen and silane as an energy-efficient heating process for hot stamping

Hot stamping is a process for the production of ultra-high-strength components used in the automotive industry for passenger protection. In this process, cut blanks are heated in a roller hearth furnace, which is operated with gas, to approx. 950 °C in 8 to 10 min and then formed and quenched in a water-cooled tool. This extends the yield strength of the components up to 1500 MPa. The long heating time is caused by the coating of aluminium and silicon (AlSi) with a thickness of 70 μm. During the 8 to 10 min, an intermetallic phase forms and ensures that the blank does not scale. Due to the long heating time and the energy carrier gas, the process is very energy inefficient and can only be controlled slowly. Resistance heating provides an energy-efficient alternative. Due to the direct current flow through the sheet, up to 68% of the energy can be saved compared to roller hearth furnace heating. The process is a high-speed heating process that can heat sheets to 950 °C in less than 10 seconds. The heating time is not sufficient for conventional coatings to bond sufficiently with the base material, which means that there are currently no suitable coatings for resistance rapid heating. A new approach is to suppress scale formation by reducing the oxygen during heating. By lowering the oxygen partial pressure to the XHV level, scale formation is not possible. At the same time, this absence of oxygen is an ideal condition for applying coatings. Due to the developed resistance heating device, sheets can be heated within a very short time without scale and without the need for fossil fuels.

Manufacturing carbon storage sintered body using microwave-selective and high-speed heating techniques

Microwave sintering of fly ash samples with large amounts of unburned carbon and CaCO3 was examined in this study. To this end, CaCO3 was mixed with fly ash sintered body to fix CO2. The decomposition of CaCO3 was observed when the raw material was heated to 1000 °C using microwave irradiation; however, a sintered body containing aragonite was obtained when the raw material was heated to 1000 °C with added water. Further, carbides in the fly ash could be selectively heated by controlling the microwave irradiation. The microwave magnetic field created a temperature gradient of 100 °C in a narrow region of 2.7 μm or less in the sintered body, and it helped suppress the CaCO3 decomposition in the mixture during sintering. By storing water in the gas phase before spreading, CaCO3, which is difficult to sinter using conventional heating, can be sintered without decomposing.

THERMALSTRUDING AS AN APPROACH TO GRAIN PROCESSING AND STORAGE

The need to maintain the thermal stability of grain at the stage of its elevator, often many hours, drying and subsequent storage limits the possibility of intensifying these processes. Shaft, column, drum and other dryers, modern granaries are bulky and energy-intensive, weakly or not at all connected with the subsequent stages of grain processing, which, in turn, are lengthy and multi-stage, which often leads to a decrease in the quality of the final product. For a cardinal solution to this problem, it is proposed to deliberately violate its thermal stability already at the stage of post-harvest drying of field grain, using the method of thermal trudging - high-speed heating, drying and explosion (swelling) of grain during its high-temperature processing in oncoming jets for 3-5 seconds. The product of thermal trudging is strudate, a grain in which raw starch is converted into dextrins and sugars, while it is disinfected from harmful inhibitors while maintaining the microelement and vitamin composition. Thus, the process of elevator drying and expensive storage of grain is replaced by thermal trudging with simplified (without drying and ventilation) floor storage of grain and obtaining a finished product of high quality or a semi-finished product used in flour-grinding, alcohol, oil-fat, and other technologies. Implementation of a new approach to the processing and storage of grain is possible on the basis of the developed technology of thermal trudging. Pilot-industrial and industrial thermal struders of two types have been created - autonomous and satellite, re-equipped on the basis of the reconstruction of standard grain dryers. In the article, various modifications of thermostruders and the principle of their work are considered. Long-term operation of thermal struders operating on flue gas heat carriers, hot air, superheated water vapor with a previously unattainable temperature up to +600 °C (even without a special task of grain drying) showed high economic efficiency, which increases when field grain is burrowed with high humidity. The versatility of thermostruders allows the use of heat-labile modes of high-intensity drying for seed grains as well.

High-speed heating of the skin using a contact thermode elicits brain responses comparable to CO2 laser-evoked potentials

ObjectiveTo compare nociceptive event-related brain potentials elicited by a high-speed contact-thermode vs an infrared CO2 laser stimulator. MethodsContact heat-evoked potentials (CHEPs) and CO2 laser-evoked potentials (LEPs) were recorded in healthy volunteers using a high-speed contact-thermode (>200 °C/s) and a temperature-controlled CO2 laser. In separate experiments, stimuli were matched in terms of target surface temperature (55 °C) and intensity of perception. A finite-element model of skin heat transfer was used to explain observed differences. ResultsFor 55 °C stimuli, CHEPs were reduced in amplitude and delayed in latency as compared to LEPs. For perceptually matched stimuli (CHEPs: 62 °C; LEPs: 55 °C), amplitudes were similar, but CHEPs latencies remained delayed. These differences could be explained by skin thermal inertia producing differences in the heating profile of contact vs radiant heat at the dermo-epidermal junction. ConclusionsProvided that steep heating ramps are used, and that target temperature is matched at the dermo-epidermal junction, contact and radiant laser heat stimulation elicit responses of similar magnitude. CHEPs are delayed compared to LEPs. SignificanceCHEPs could be used as an alternative to LEPs for the diagnosis of neuropathic pain. Dedicated normative values must be used to account for differences in skin thermal transfer.

Effect of high-current pulsed electron beam treatment on defect substructure of the high-entropy alloy of Co – Cr – Fe – Mn – Ni system

High-current pulsed electron beam surface treatment is a method of materials modifying, which improves the mechanical properties of metal materials. Due to high-speed heating, evaporation, recrystallization, as well as plastic deformation, dislocations with high density are formed in the surface and, as a result, an increase in indicators of various physical and mechanical properties, such as hardness, wear resistance, etc., is observed. Since currently high-entropy alloys are a relatively new class of materials, the effect of pulsed electron beam treatment on the dislocation substructure has not yet been established. In this work, a non-equiatomic high–entropy alloy of the Co – Cr – Fe – Mn – Ni system, made using a wire-arc additive manufacturing, was subjected to surface treatment using a high-current pulsed electron beam with an energy density of 30 J/cm2. By the method of studying thin foils using transmission electron microscopy, it was found that the treatment does not affect the chemical composition of the alloy, but leads to serious changes in the dislocation substructure. A nonmonotonic change in the scalar density of dislocations was revealed, reaching a maximum value of 5.5·1010 cm–2 at a distance of 25 µm from the irradiation surface. It is shown that an undirected cellular dislocation substructure with cell sizes from 400 nm to 600 nm is formed at this distance from the surface. With further distance from the surface at a distance of up to 45 µm, the dislocation substructure changes from cellular to cellular-mesh. At a distance of 120 – 130 µm, the effect of a high-current pulsed electron beam is not observed – the substructure corresponds to the substructure of the initial alloy with a chaotic distribution of dislocations.

Strengthening of Low-Carbon Alloy Steel by Electrolytic-Plasma Hardening

The global demand for oil and gas products has caused noticeable qualitative and quantitative changes in the applied technological processes of manufacturing parts and equipment for the extraction and transportation of oil products. Kazakhstan is the largest oil-producing country in the world, therefore, the development of advanced technology for the production of oil and gas equipment can stimulate industrial and economic growth. Traditional technologies for hardening critical parts of Wedge-Shaped Columns (WSC) are energy-consuming and labor-consuming, although they are used in many industrial enterprises. For scientific research on chemical-thermal hardening of a low-carbon alloyed die made of steel 20X, GOST 33260-2015 (207 Steel), wedge column piping, an experimental installation for electrolytic-plasma hardening has been developed. Experimental studies of plasma electrolyte hardening were carried out in various processing modes. The dependence of the current-voltage characteristic of the high-speed heating of the part on the temperature of the ionized electrolyte plasma is described. The processes of heat transfer, heating, and quenching in the electrolyte are described by a mathematical model, a regression formula is derived. The main parameters of the electrolytic-plasma hardening are determined, and the optimal processing modes are derived. Raster elemental analysis indicates the surface modification of the hardened layer of low-carbon alloy steel with carbon. The method of electrolytic-plasma hardening allows locally hardening of the mating working surfaces of the PCC die. Investigated the results of changes in the microstructure, an increase in hardness relative to the initial state. The article is financially supported by the "Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan" within the framework of the grant project IRN AR09058518 "Increasing the wear resistance of materials in the engineering industry by electrolyte-plasma modification".

Увеличение ресурса оборудования электромеханической поверхностной закалкой

The paper analyzes traditional methods of hardening. The results of comparative wear tests of the samples made of 20KhNZA steel after nitrocementation and electromechanical surface quenching are presented. The results of the wear tests of the samples made of steel 20KHN3A after nitrocementation and electromechanical surface quenching indicate the high efficiency of the electromechanical processing technology. A competitive feature of the technology of electromechanical surface quenching of parts made of 20KHNZA steel is the possibility of flexible control of the parameters of high-speed electric heating and simultaneous thermoplastic deformation of the material of the surface layer of the most loaded parts in order to form gradient fast-quenched structures at a depth of up to 0.05…0.1 mm in the manufacture and repair of parts. Conclusions and recommendations on the method of using these types of hardening are providedю English version of the article is available at URL: https://panor.ru/articles/increasing-the-equipment-service-life-by-electromechanical-surface-quenching/64911.html

Взаимодействие карбидов WС и Cr3С2 при термообработке сплавов WС – Cr3С2 – Сu

Composite alloys WC – Cr3C2 – Cu were obtained by infiltration of copper melt into uncompacted powders WC and Cr3C2 (reference alloys) and their mixtures with a weight ratio WC: Cr3C2 = 1:1. Impregnation of uncompacted carbide powders with copper melt was carried out at low frequency (~ 80 Hz) vertical vibration (LFV) of the crucible with alloy components for 10 min in a resistance furnace in an atmosphere of flowing argon. The effect of heat treatment of the obtained model composites on the interaction of carbides WC and Cr3C2 under isothermal and dynamic action of temperature, as well as during high-speed cyclic heating of the alloy surface by an electric arc (120 A, 45 V, 2 Hz, 10000 arc interruption cycles) has been studied. The evolution of the structure of alloys has been investigated by means of electron microscopy, X-ray spectral microanalysis, X-ray phase and differential thermal analysis. It is shown that the action on the sample surface of the temperature field created by an electric arc leads to an intense interaction of carbides. In this case, matrix copper, periodically transforming into a melt, plays the role of a transfer medium (diffusion medium). As a result of such heat treatment in the upper layers of the alloys, finely dispersed compositions of complex carbide phases with sizes of ≤ 1 – 2 μm were formed, i.e. 1 – 2 orders of magnitude smaller than the size of the initial carbides.

Influence of technological process parameters on qualitative characteristics of coal thermolysis products

Purpose. To determine and compare the qualitative and quantitative characteristics of products obtained under different coking conditions to streamline the process and consider the deeper use of recycled materials at Shubarkol Komir JSC. Methodology. Based on the existing coking technology on the basis of the enterprise, two variants of temperature exposure to coal were tested. The first option is heating coal to 900 C, which is carried out by slow thermolysis of coal in a stream of ascending gases. The second option is high-speed heating of coal to 900 C with further loading of the released products into the chamber for additional pyrolysis at 800 C, which is carried out with the development of reactions involving oxygen-containing gases from the furnace and from the outside. Findings. At the production site as well as under laboratory conditions, the composition and quality characteristics of the products of heat treatment of long-flame coal under various temperature effects were determined. Differences in the composition of decomposition products were noted and their quantitative yield was determined. Originality. Analytical data on coking products have been obtained and the dependences of their quantitative and physical parameters on different applications of thermolysis on the coals of the Shubarkol deposit have been established. Practical value. The results of the work allow improving the technology of coke production by introducing an additional stage of pyrolysis, which will lead to an improvement in the consumer properties of coke, and also create conditions for the development of methods for using secondary production products.

Method for Infrared CCD Monitoring of High-speed Heating Process of Laser Heat Treatment

Method for Infrared CCD Monitoring of High-speed Heating Process of Laser Heat Treatment

Thermal purification of natural graphite by means of high-speed heating

Thermal purification of natural graphite by means of high-speed heating

Stability of Strength Characteristics of Hardened by Deformation AMg6 Alloy during High-Speed Heating

The results were shown in influence of fast heating parameters on the structure and properties of cold-worked alloy AMg6 with original hot-forged structure. Based on the measured data, the change of mechanical properties of cold-worked alloy AMg6 during the process of short duration heating was evaluated. There was reviewed the role of the temperature and the time of heat on the processes of softening the samples of cold-worked alloy AMg6. The stability of mechanical characteristics of hammer-hardened alloy AMg6 under elevated test temperatures was evaluated. It is shown that the return processes in cold-deformed AMg6 alloy during heating in the temperature range studied receive the most intensive development in the first 5–10 minutes, reducing the hardening effect from cold deformation, determined by tensile strength, respectively: by 8–9% with 100 °C; 26–27% at 150 °C; 37–38% at 200 °C; 42–44% at 250 °C and 50% at 300 °C. A decrease in the yield strength during high-speed heating in the temperature range studied is much faster ,compared with the change in the tensile strength. Hour exposure at 200 °C reduces the hardening effect on the yield strength from 340 MPa to 258 MPa, while the tensile strength decreases from 430 MPa to 385 MPa.

Thermal damage evolution of granite under slow and high-speed heating conditions

Abstract A continuum based numerical approach is used to investigate the effects of slow and high-speed heating, including the ISO 834 fire curve, on thermal cracking of granite. During slow heating, thermal stress variations are mainly controlled by the heterogeneous thermal expansion of mineral grains. As a result, the stress concentrations are more isolated and dispersedly distributed throughout the sample. High-speed heating produces large thermal gradients especially at the outer surface of the samples, inducing big thermal strain increments and subsequent high compressive stresses. Larger cracks are formed due to a wider range of concentrated tensile stresses inside the sample during high-speed heating. At low temperatures, slow heating has a stronger influcence on micro-cracking. Due to larger cracks and newly induced micro-cracks, high-speed heating has an increasingly important impact on crack pattern in granite at high temperatures. Although shear failures show a significant increase at 800 °C, tensile cracks are still the majority of total failures in both, slow and high-speed heating scenarios. The final crack pattern in granite under fire conditions is a result of different cracking behaviors caused by various heating rates. This consequently affects strength and final failure pattern of granite.

Increasing Methods of the Car Valve Tappets Durability

It is established that the admissible size of wear on the restored cemented (nitrocemented) details depends on specifications on operation of the car. An indispensable condition at the same time is preservation in a blanket (a worn-out detail) of carbon not less than 0,4%. It is offered for high-speed heating of worn-out parts of details under plastic deformation to use induction installation and the offered method of restoration of pushers of valves I have shown that details meet specifications of manufacturer.

Study of electrothermically treated metal materials

Scatter of hardness and electrical resistivity of ferromagnetic (steels 25, 50KhFA, 65G, 9KhF, ShKh15, 6KhS, 8Kh6NFT), paramagnetic (titanium alloy VT16) and diamagnetic alloys (D16 and AMg2) after the electrophysical process of high-speed heating for quenching with high density current (108 А/m2) with rapid cooling in oil or in water is studied. Effect of electrophysical parameters of materials on the result (hardness and electric resistivity) of electrothermal processing is determined. Effect of chemical composition, coercive force and Joule component of electric current of metallic materials on variation of hardness is studied. The results can be used in development of technology for treatment of metallic materials by heating with high-density current.

Wear resistance of strengthened layers with nanocrystalline structure in friction with boundary lubrication

Friction treatment refers to surface strengthening (hardening) methods using highly concentrated energy sources. The source of thermal energy occurs in the contact area of the tool-part due to high-speed friction (60–90 m/s) of the tool on the treated surface. The heating rate of the metal surface layer is 105–106 K/s. After moving the energy source from the contact zone, high-speed cooling of the surface layer of the metal takes place. The cooling rate is 104–5∙105 K/s. Under the action of high-speed heating and cooling of the contact area of the tool-part in the surface layers, a strengthened (hardened) nanocrystalline (white) layer is formed. The formed nanocrystalline surface layer has other physical, mechanical, chemical properties in comparison with the base metal of the part. Studies have shown that in the process of friction treatment of working surfaces of parts made of Steel 40NiCr6 (quench hardening and low-temperature tempering) a strengthened layer with a thickness of 250–320 μm with a hardness of 7.6–9.2 GPa is formed. The grain size of the surface strengthened layer was 20–40 nm near the treated surface. The formation of the strengthened layer is influenced by the shape of the working surface of the tool. Thus, a strengthened layer of greater thickness and hardness is obtained when machining with a tool with transverse grooves on the working part than with a tool with a smooth working part. Experimental studies in friction with maximum lubrication of pair “Steel 40NiCr6 and Grey Cast Iron GG20” showed that the strengthened nanocrystalline layer significantly increases the performance during sliding friction. Only samples made of steel were strengthened, counter-samples made of gray cast iron were not strengthened. The wear intensity of strengthened pair is 2.2–3.1 times less compared to unstrengthened pair. During the friction of the strengthened pair, the coefficient of friction and the temperature in the sliding zone also decrease. The best results were obtained when studying the friction pair in which the samples were strengthened with a tool with transverse grooves on its working part.

The Influence of Temperature and High-Speed Heating on Tensile Strength of Granite and the Application of Digital Image Correlation on Tensile Failure Processes

Thermal induced cracks and the tensile strength variation of Eibenstock granite subjected to high-speed heating have been studied through lab testing. The Digital Image Correlation (DIC) technique was used for analysing the tensile behaviour of granite at high-speed heating rate and different temperatures. For samples heated to 800 °C with heating rates of 200 °C/min and 300 °C/min, thermal-induced macrocracks become visible to the naked eyes, while no obvious macrocracks are observed on samples heated according to ISO 834 curve. Compared to the influence of temperature, the selected heating rates only have a negligible impact on tensile strength and axial displacement. The DIC analysis shows the crack initiation and progressive crack propagation before the main crack is formed at failure. Compared to the samples heated up to 400 °C, the samples heated up to 800 °C show less brittle fracture behaviour, and the tensile strength is greatly reduced. The final failure patterns prove that different heating scenarios lead to different microcrack structures and consequently influence the failure mode at the macroscopic scale.

Impact of cooling on fracturing process of granite after high-speed heating

Only very few studies about the influence of cooling on the thermo-mechanical properties of heated rocks exist. This study focuses on high-speed heating followed by slow as well as rapid cooling of granite samples. Target temperatures of 400 °C and 800 °C were reached with heating rates of 200 °C/min, 300 °C/min and ISO 834 standard fire curve. Numerical simulations are used to investigate the temperature evolution inside the sample. The digital image correlation (DIC) technique was used to analyse the strain field evolution during air-cooling with furnace removed. DIC analysis reveals that the microcracks induced by high-speed heating and high temperatures (i.e. 800 °C) can close progressively due to the material contraction during cooling. The closing of microcracks caused by shrinkage plays a more important role than cracking behaviour caused by thermal gradients (i.e. thermal shock). Both rapid (furnace removed) and slow (furnace in place) cooling do not show obvious influence on the stress-strain behaviours of granite samples heated to 400 °C. The samples heated to 800 °C with rapid cooling have a higher uniaxial compression strength than in slow cooling case. This indicates that the contraction effect during rapid cooling might be more intense than in slow cooling cases.