Furnace System Research Articles

Online Identification and Temperature Tracking Control for Furnace System With a Single Slab and a Single Heater Over the Wirelessly Connected IoT Controller

Online Identification and Temperature Tracking Control for Furnace System With a Single Slab and a Single Heater Over the Wirelessly Connected IoT Controller

Numerical and experimental study to examine methods to increase the convectional heat transfer of recuperator tubes

The use of structured tubes in tube bundle recuperators is intended to improve the energy efficiency of gas-fired industrial furnace systems with central air preheating. Currently, smooth tubes as well as smooth tubes with internal twisted tape are commonly utilised. The increased surface area of structured tubes leads to an increased heat transfer between the off-gas and the combustion air. However, structuring leads to an increased pressure loss. The aim is to find an optimal operating range in which the pressure losses are still acceptable and the greatest increase of heat transfer compared to the reference will be achieved. Smooth tubes and also smooth tubes with twisted tapes are considered as reference systems in comparison to two concave structured tubes. CFD simulations were used to investigate the influence of the operating parameters of combustion air velocity and off-gas velocity on heat transfer according to industrial scale. The simulations have shown that the heat flow increases with the honeycomb depth and strongly depends on the operating conditions. Experimental measurements in a test bench were carried out to validate the model and confirm the positive influence of structuring on heat transfer.

A novel layout of the heat-sink base with a high cooling efficiency for polysilicon reduction furnace

The performance of the heat dissipation system for polysilicon reduction furnaces could influence the crystal quality of polysilicon and the service life of electrodes. The heat-sink base of the polysilicon reduction furnace is a key cooling component because it is the foundation for the electrodes. This study presented a novel layout that slightly adjusted the layout of the inlet or outlet for the base and it could acquire a better cooling effect compared to the traditional layout. The influence of the location, size, and number of outlets has been a numerical study. The results showed that increasing the number of outlets and setting the inlet on the bottom could significantly improve the average temperature of the upper surface. The temperature decreased by 13% using the layout with two outlets and an inlet set on the bottom compared to the traditional layout. Reducing the size of the inlet also could further improve the cooling effect. However, reducing the size of the outlet has little influence on the cooling effect, but would greatly increase the internal pressure. This research could provide a novel layout for the design of the heat-sink base of polysilicon reduction furnaces.

Optimal cyclic scheduling of ethylene plants in backup furnace mode with separation capacity constraints

Ethylene plants (EPs) are a critical output source of ethylene. The cyclic scheduling optimization is crucial to increase the profitability of an EP. The EP comprises the ethylene cracking furnace system (ECFS), quenching, compression, separation sections, etc., which culminates in a large-scale optimization problem. In addition, the performance-decaying and semi-continuous characteristics of the ECFS inevitably lead to fluctuations in product throughput, resulting in an unstable production process and product quality decline. To address this issue, we propose a mixed-integer quadratic programming (MIQP) model for the cyclic scheduling of the EP in backup furnace mode with separation capacity constraints. This novel model can reduce fluctuations in product throughput by running a backup furnace when one furnace is shut down for decoking. Besides, the separation capacity constraints ensure that high-quality products can be separated from the cracked gas downstream. Moreover, the reformulated normalized multiparametric disaggregation technique (RNMDT), which relies on convex envelopes, is employed to relax the proposed MIQP model into a mixed-integer linear programming (MILP) model by partitioning the domain of the variables in the quadratic terms. Subsequently, an optimization framework based on the RNMDT is established to enhance the solution efficiency of the original problem. Finally, a case study from the real world reveals the effectiveness of the proposed method, which can provide instructive optimal cyclic scheduling for the EP.

Determining the oxidation behavior of matrix graphite

This work presents the oxidation behavior of matrix graphite in air. Matrix graphite, graphite powder/flakes bonded by a small amount of non-graphitic carbon, surrounds coated fuel particles in order to form cylindrical fuel compacts (in prismatic core designs) or spheres (in pebble-bed reactor designs). This work focuses on oxidation tests conducted on two matrix graphite materials, one provided by Kairos Power and the other A3 matrix graphite. Some of the tests followed American Society for Testing and Materials (ASTM) oxidation testing standards using a vertical furnace system and others were performed in a thermogravimetric analyzer (TGA). It was determined that, at temperatures of 450 °C–700 °C, the oxidation rate of the Kairos matrix graphite follows the Arrhenius equation. In comparison with A3 matrix graphite, the Kairos matrix graphite shows better oxidation resistance at high temperatures (≥550 °C), but also a higher oxidation rate at low temperatures. Both the A3 matrix graphite and the Kairos matrix graphite materials may experience preferential oxidation of the partially graphitized binder. An oxygen penetration gradient was also observed when using the three characterization methods (i.e., optical microscope, x-ray tomography [XCT], and density profile by the lathe) enlisted in this research. The oxygen penetration depth increases with decreasing isothermal oxidation temperature, while the center of the oxidized samples (10% weight loss) remains almost untouched even at 500 °C.

Evaluation, Prediction, and Feedback of Blast Furnace Hearth Activity Based on Data‐Driven Analysis and Process Metallurgy

For complex, difficult‐to‐control, and hour‐delay blast furnace (BF) systems, the quantitative characterization, prediction, and adjustment of the BF hearth activity are significant in improving the furnace status. In this study, data including raw fuel, process operation, smelting state, and slag and iron discharge during the entire BF process are analyzed, with a total of 171 variables and 5033 groups of data. Based on the knowledge of BF technology, a comprehensive index of hearth activity is then proposed to quantitatively characterize and grade the activity level of the BF hearth; the rationality of this method is verified from the two aspects of furnace heat level and furnace status coincidence. Compared with the traditional single‐machine learning algorithm, the performance of the proposed method that combines genetic algorithm and stacking exhibits significant improvement. The hit rates for 10% and 5% errors in the prediction and estimation of hearth activity are 94.64% and 80.36%, respectively. To enhance the BF hearth activity, quantized and dynamic actions and suggestions are also simultaneously pushed. The model of BF hearth activity is successfully applied in practical online production. During the application period, the average furnace hearth activity increases by 10% compared to the historical value.

A Critical Review of The Process and Challenges of Silicon Crystal Growth for Photovoltaic Applications

AbstractCrystalline silicon (c‐Si) solar cells have been accepted as the only environmentally and economically acceptable alternative source to fossil fuels. The majority of commercially available solar cells of all Photovoltaic (PV) cells produced worldwide, are made of crystalline silicon. Due to their excellent price/performance ratio and their demonstrated ecological durability, crystalline silicon wafers are by far the most common absorber material used in the production of solar cells and modules today. These wafers are primarily made using either a directional solidification that produces large‐grained multi‐crystalline (mc‐Si) wafers with a greater defect density or a solar‐optimized Czochralski (Cz) growing method that produces crystalline silicon with low defect density (c‐Si). The grown crystalline wafer contains foreign atoms that enhance the wire saw damage, reduce the minority carrier lifetime as a result get the minimum conversion efficiency of the solar cells. The current review illustrates how the elements of the furnace system affect impurity production and distribution of the developed silicon ingot and how the growth process affects the chemical reaction. Additionally, it covers the outcomes of simulations and experiments conducted on the growing process of c‐Si and mc‐Si ingots and recommends the most appropriate processing parameters, geometrical system, and argon gas flow rate.

Improving the oxidation resistance of carbon fibers via B4C coating by modified boron oxide chemical vapor deposition

Carbon fiber is one of the engineering materials frequently used in high-temperature applications despite its very poor oxidation resistance. To enhance the oxidation resistance of C fibers and improve the service temperature, boron carbide coatings were prepared by the modified reactive boron oxide chemical vapor deposition (BOCVD) method. For the coating process, a tube furnace system was utilized. Experiments were performed at 1100–1400 °C for up to 6 h under a flowing Ar atmosphere. Coatings were analyzed by SEM, Raman, XRD, and XPS analysis. B4C coatings were found to be in nodular form around 30–50 nm. Oxidation tests performed in flowing air up to 1500 °C by DTA-TG analysis and oxidation mechanisms were explained in details. We revealed that the base oxidation resistance increased up to 180 °C with no net mass gain or loss.

Effect of ammonia and coal co-firing on the formation mechanism and composition characteristics of particulate matter

Ammonia-coal co-firing is considered to be an effective method to reduce carbon dioxide emissions and the existing researches mainly focus on the combustion characteristics and NOx emission characteristics. In this study, co-firing of coal and ammonia was carried out in the high temperature drop tube furnace system with a large co-firing ratio of 0–50%. Firstly, the unburned fuels and the main composition of flue gas were measured as a baseline result. The results showed that ammonia co-firing will lead to the increase of NO and NOx concentration. Further, the particulate matters generated under different conditions were collected and tested. It was found that ammonia co-firing will affect the formation characteristics of particulate matter, especially sub-micron particulate matter. With the increase of co-firing ratio, the concentration of PM1 showed an overall increasing trend, but decreased at 20%. And ammonia co-firing will have an effect on the content of Si, Al, S and trace elements (As, Pb) in submicron particles. The content of water vapor, NOx in flue gas and combustion temperature have changed and affected the formation of SO3 and the gasification of silica and trace elements.

Comprehensive insight into co-pyrolysis of sewage sludge and tobacco stalk: Effects of mixing ratio and pyrolysis conditions on product distribution and characteristics

Co-pyrolysis of sewage sludge (SS) and tobacco stalk (TS) was conducted, where TS are rich in inorganic elements. The effects of the mixing ratio and pyrolysis temperature on pyrolysis products were investigated through the tube furnace system. The components of gas and tar were determined. In addition, the N/S ratio, pore distribution characteristics, surface functional group characteristics, aromatisation characteristics and inorganic element content of char were studied. Results show that the addition of TS to SS has a significant synergistic effect. Particularly, when the ratio of SS to TS is 1:3, the pyrolysis gas yield is the largest. The inorganic elements with a catalytic effect can promote the conversion of char and tar into pyrolysis gas. However, with the increase in pyrolysis temperature, the synergistic effect will gradually weaken. The increase in pyrolysis temperature will promote the development of mesopores in char but will reduce the order degree of the char structure. The addition of TS in SS will further increase the number of mesopores in char, and the obtained char carbon structure is more ordered. When the pyrolysis temperature is 600 °C, the tar yield is the highest, and the higher the mixing ratio of SS, the better the formation of polyaromatic compounds and aliphatic hydrocarbons.

A Hybrid Cluster Variational Autoencoder Model for Monitoring the Multimode Blast Furnace System

Efficient monitoring of the blast furnace system is crucial for maintaining high production efficiency and ensuring product quality. This article introduces a hybrid cluster variational autoencoder model for monitoring the blast furnace ironmaking process which exhibits multimode behaviors. In contrast to traditional approaches, this method utilizes neural networks to learn data features and effectively handles the diverse feature types observed in different production modes. Through the utilization of a clustering process within the hidden layer of the variational autoencoder, the proposed technique facilitates efficient fault detection in the context of multimodal blast furnace data. Based on the variational autoencoder model, this study further establishes a unified monitoring index and defines a method for computing the control limits. The application of the model to real blast furnace data reveals its proficiency in accurately identifying faults across diverse modes; compared with the probabilistic principal component analysis based on the local nearest neighbor standardization method and the recursive probabilistic principal component analysis, the model shows a reduction in false positives by up to 10.3% and a substantial reduction of 19.2% in the missed detection rate. This method achieves a remarkable false detection rate of only 0.2% and 0 instances of missed detection.

Numerical Investigation of the Effect of Modified Heat Exchanger Block on Thermal Stress and Dislocation Density of DS‐Grown mc‐Si Ingot

AbstractThe present work is based on the numerical investigation of thermal stress and the dislocation density of the directional solidification (DS) grown multi‐crystalline silicon (mc‐Si) ingot. The heat exchanger block (HEB) plays the main role in the growth process, which decides the thermal stress and melt‐crystal interface of the mc‐Si ingot. The conventional furnace is modified to increase the quality of the mc‐Si ingot. The modification on the conventional furnace is done in the insulation block replaced by 1/3rd of the HEB. The HEB enhances the huge amount of heat extraction from the bottom of the crucible. The von Mises stress, dislocation density, and thermal gradient are analyzed. The thermal stress is reduced by the low thermal gradient influenced by the modified HEB. The modified HEB reduces the von Mises stress and dislocation density. The modified furnace system overcomes the conventional case ingot. The result shows that the modified furnace grown mc‐Si ingot improves the efficiency of the solar cell.

Theoretical Exergoenvironmental Analysis of a Tunnel Furnace and Drying System in a Brick Production

The performance of a tunnel furnace and a tunnel dryer in a brick production was exergoenvironmentally assessed. The real production data of a brick factory in Turkey with a daily production capacity of 392 tons of fired bricks were used in the analysis. The exergoenvironmental factor of the control volume was calculated as 0.87. The specific exergoenvironmental cost of the control volume was determined to be 559.55 €/h, 3.39 €cent/ kg fired brick and 1.94 €cent/MJ. The specific exergoeconomic cost and the environmental damage prevention cost were obtained to be 0.41 € cent/MJ and 1.53 € cent/MJ, respectively. Because the ratio of exergoenvironmental cost to sales price of 2.41 € cent / kg fired brick was 1.41 (above 1), it was concluded that the brick production in Turkey was not sustainable in terms of exergoenvironmental analysis.

Novel Control System Strategy for the Catalytic Oxidation of VOCs with Heat Recovery

A theoretical study of the dynamic closed-loop behaviour of a reactor/feed-effluent heat exchanger (FEHE)/furnace system for the catalytic combustion of volatile organic compounds (VOCs) is presented. A 1D pseudohomogeneous plug-flow model is proposed to simulate the non-steady-state operation of the monolith reactor and the FEHE, while the furnace behaviour is described by means of a heterogeneous model of lumped parameters. Positive energy feedback is a source of instability that leads to strong thermal oscillations (limit cycles) and may cause damage to the equipment and sintering of the catalyst. The design of a robust and flexible control system and an efficient control strategy are, therefore, required to ensure safe and stable operation. The response of the system under three different control strategies to the most frequent disturbance variables—the feed flowrate (FV0) and feed concentration of VOCs (C0Et)—was evaluated. One of the control strategies consisted of a single-loop feedback system with servomechanism changes in the reactor inlet temperature (T0) that manipulated the bypass valve and, sequentially, the natural gas flowrate in the furnace (FNG). This approach made it possible to meet the control objective (reducing VOCs) without losing controllability and while minimizing the use of external fuel.

A data-driven strategy for industrial cracking furnace system scheduling under uncertainty

Cyclic scheduling of ethylene cracking furnace system (CSECFS) has a significant impact on raising economic performance of ethylene plants. However, in actual plants, optimal results of deterministic models may be suboptimal or ineffective because of various uncertainties. This paper proposes a novel data-driven adaptive robust optimization (DDARO) strategy that effectively bridges robust optimization and machine learning methods. A mixed-integer nonlinear programming (MINLP) model for CSECFS is developed initially. Second, data-driven uncertainty sets are generated using the historical data of processing flow rates: maximally correlated principal component analysis (MCPCA) is employed to partition the data into two subspaces, which are then delineated by support vector clustering (SVC) and generalized norm approaches, respectively. Third, a multi-stage DDARO model is established using the derived uncertainty sets and afterward transformed as a tractable single-stage model. Finally, a real-world case is performed to exemplify the effectiveness of the proposed framework.

Distributions of and environmental risks posed by Cr and Zn when co-treating solid waste in different kilns

In order to dispose solid waste reasonably and provide reference data for solid waste co-treatment in industrial kilns, coal chemical products were co-treated in a pulverized coal furnace and refuse-derived fuel was co-treated in a gasifier-coupled pulverized coal furnace system. The distribution and environmental risks of Cr and Zn in different kilns were compared and analyzed. The Cr and Zn distributions in the solid products from the pulverized coal furnace tests were similar. Fly ash contained > 80% of the Cr and Zn. In the gasifier, cyclone dust and gasification gas contained only ∼ 60% of the Cr and Zn, and gasification slag contained > 40% of the Cr and Zn. The gasification gas contained ∼ 33% of the Cr and Zn volatilized. The pulverized coal furnace temperature was > 1,500 °C. Most of the Cr and Zn volatilized and then condensed, so became enriched in the fly ash. The gasifier temperature was ∼ 750 °C, so less volatilization occurred and Cr and Zn became enriched in the gasification slag. The Cr and Zn concentrations in leachates of the solid products were lower than the limits of “GB 5085.3–2007”. However, the Cr and Zn concentrations in the gasification slag and cyclone dust leachates were close to the limits and tens to hundreds of times higher than the concentrations in the pulverized coal furnace fly ash and slag leachates. The low temperatures and low-oxygen environments of gasifiers are not conducive to heavy metals being stable in the solid products, and the environmental risks posed by heavy metals in the solid products are high. The risks to the environment are less serious for co-treating solid waste in pulverized coal furnaces than gasifiers.

The Design and Verification of a TBP/OK Pyrolysis Incineration Stable System

This project designed and created a large-scale pyrolysis incineration system that decomposes waste tributyl phosphate/kerosene (TBP/OK) solvent from the plutonium/uranium process (PU-REX) in the nuclear industry. This system consists of a suspension preparation system (SPS), a pyrolysis and ash discharge system (PADS), and a combustion furnace and gas treatment system (CGS). The preparation of a waste TBP/OK emulsified suspension in the SPS, continuous operation experiments of the PADS and CGS, and pyrolysis incineration experiments were conducted. The results show that the SPS achieved the automatic preparation and feeding of emulsified suspensions at 30 kg/h. The PADS decomposed 99.99% of the TBP/OK emulsified suspensions and fixed more than 99% of phosphorus. The CGS burned the pyrolysis gas without diesel oil and purified more than 99.995% of the radioactive nuclides. This system showed great feasibility, stability, continuity, and safety, proving the compatibility between multiple systems of this new design. This paper marks a significant step in pyrolysis incineration technology for the nuclear industry.

Variations in the physicochemical properties of spent honeycomb V2O5-WO3/TiO2 catalysts from PC and CFB boilers SCR denitration systems

The massive production of spent honeycomb V2O5-WO3/TiO2 catalysts has caused serious environmental hazards. Revealing the physicochemical property variations of the spent catalysts is of great significance to clarify the deactivation mechanism of catalysts and the recovery of the spent catalysts. This study focused on the changes of typically spent catalysts, selected from pulverized coal (PC) and circulating fluidized bed (CFB) boiler deNOx systems, morphologies, pore structure, chemical composition, carrier, and active components properties, etc. The activities of most spent catalysts could be to more than 95% at 300–400 °C after vibration cleaning. The pore blockage caused by fly ash and sulfur deposition is the major deactivation factor of the catalysts from the two furnace systems. The catalysts from CFB furnaces are more easily deactivated, which is owing to they are more prone to occur severe pore structure loss. The transformation of anatase to rutile TiO2 as one of the major factors causing the pore structure loss would form the irreversible deactivation of the catalysts. The valence state of the active component V has shifted. The spent catalysts from PC systems typically exhibit higher V4+/Vn+ ratios. However, those from CFB systems display a noticeable decrease, which may be attributed to the formation of CaWO4, resulting in the destruction of dispersed active sites on the surface. Finally, the deactivation mechanism of the spent catalysts from different furnaces of coal-fired power plants was summarized. This research is beneficial for further modification of SCR catalysts under different application conditions and provides valuable insights into the classification and recycling of the spent catalysts.

Batch Furnace Chemical Vapor Deposition of Pure Boron Layers on Si and GaN Substrates for Low-Leakage-Current Diode Fabrication

Boron deposition on both n-Si and n-GaN in the temperature range 250 - 500 °C, has been shown to form diodes with low saturation currents, i.e., electron injection from the n-substrate into the B-layer was efficiently suppressed. Moreover, down to 3-nm-thick B-layers on Si were shown to form a material barrier to Al, opening the possibility of fabricating Au-free gates for gallium-nitride high-electron-mobility transistors (GaN HEMTs). Several different chemical- and physical-vapor deposition (CVD/PVD) methods for depositing B have been studied for fabricating p+n-like Si diodes, called PureB diodes, all with comparable results. In this paper, the deposition of B-layers from diborane in a CVD batch furnace system is evaluated, particularly for use as a barrier material to enable Al-contacting of GaN diodes. These Al-B diodes could provide an option for fabricating low-leakage diodes that are compatible with complementary metal-oxide-semiconductor (CMOS) processing at industrially attractive high throughput. The bulk B has high resistivity, which, combined with the fact that non-uniformities in the nm range, are typical due to gas depletion along the furnace tube and gives uncontrollable, often high diode series resistance. A simulation study shows that Al-B could, nevertheless, be used as a gate stack in HEMTs for low-frequency power applications.

Design And Build The Appropriate Technology Machinery For Shredded Fish Processing

The Shredded fish is produced by machines automatically, which can facilitate the production process. Previously the process was done conventionally in one production run. This problem prompted researchers to create a machine by combining three tool systems to become a shredded fish processing machine, including a system for separating meat and fish bones, a cooking furnace system, and a shredded dryer/spinner system that can be controlled electrically in the production process, in addition to the shredded produced more cleanly and efficiently in one production process. This machine utilizes the power of an electric motor of ¾ Hp, which is the driving force for the meat separator machine with a rotation speed of 2840 rpm and a production capacity of 30 Kg/hour.