Furnace Efficiency Research Articles

Анализ фактического КПД электродуговой сталеплавильной печи

Анализ фактического КПД электродуговой сталеплавильной печи

Assessing energy efficiency of electric car bottom furnaces intended for thermal energization of minerals

The paper deals with a new concept of electric furnaces for roasting and thermal energization of vermiculite and other minerals with vibrational transportation of a single-layer mass under constant thermal field. The paper presents performance calculation and comparative assessment of energy data for furnaces of different modifications: flame and electric furnaces with three units, furnaces with six units and ones with series-parallel connection of units, and furnaces of new concept.

Construction and Performance analysis of Pit furnace by using Biodiesel

From the past years coal is used as major fuel source for melting nonferrous metal in many foundry industries which is hazardous. The coal should be replaced by environmental friendly or reduced pollutant fuels. Biodiesel is derived from non-edible oil seeds, contains calorific value is almost equal to 90% diesel. Biodiesel emits low carbon, sulfur emissions during its combustion. This research concentrates on utilization of biodiesel as a fuel in pit furnace to melt aluminum scrap. An attempt is made to study the performance of Karanja biodiesel on pit furnace. The developed furnace melts 20 kg of aluminum in 40 minutes and attains a maximum temperature of 10000C. The thermal efficiency of furnace is found to be 18.71%. Normal thermal efficiency of pit furnace lies between 4-19 %. The furnace is fitted with medium exhaust pipe for easy escape of combustion gases. The blower is used to supply air and to atomize the fuel into the furnace chamber. The top surface of furnace is closed to avoid conventional and radiation losses. An air gap is provided as insulation of furnace. This furnace can effectively be used in academic laboratories to melting of nonferrous metal.

Two Dimensional Thermal-Hydraulic Analysis for a Packed Bed Regenerator Used in a Reheating Furnace

Packed bed is widely used for different industries and technologies, such as heat exchangers, heat recovery, thermal energy storage and chemical reactors. In modern steel industry, packed bed regenerator is widely utilized in the reheating furnace to increase the furnace efficiency. This study established a two dimensional numerical model to simulate a packed bed used in regenerative furnaces. The physical properties of fluids and packed stuffing (such as density, thermal conductivity, and specific heat) are considered as functions of temperature to adapt the large temperature variation in operation. The transient temperature profiles of the flue gas, packed bed, and air during the heating and regeneration period are examined for various switching time (30, 60, 120, and 240 s). The results reveal that, during the heating period, the spanwise averaged heat transfer coefficient is decreased along the longitudinal downstream direction, while during the regeneration period, the opposite trend is true. Moreover, the regenerator thermal effectiveness is decreased by increasing the switching time.

Life-cycle carbon footprint analysis of magnesia products

Liaoning Province in China contains significant magnesite deposits and thus has become the country’s largest production and export base for the magnesia raw materials and refractories. Unfortunately, the processing of such materials and refractories contributes significantly to the carbon emissions of the magnesite industry. In the present study, the carbon footprints associated with magnesia production processes were analyzed and compared using the life cycle assessment method of cradle-to-gate in order to provide a theoretical basis for improving the production processes, optimizing the product structure and for the formulation of energy conservation and emission reduction measures. In order to show the results against changes in key parameters, the sensitivity analysis was carried out. The results show that the total carbon footprints of light calcined magnesia and fused magnesia are the lowest and highest, respectively. In addition, one-step calcination method with the material of magnesite was found to be cleaner than the two-step calcination method with the material of light calcined magnesia. The direct carbon footprints resulting from the magnesite decomposition processes in the making of all magnesia products are very similar, while the emissions resulting from fuel combustion to produce sintered magnesia are high, especially in the case of two-step calcination. To reduce the total carbon footprints of light calcined magnesia and sintered magnesia, emphasis should be placed on the direct carbon footprints resulting from the production processes. In the case of fused magnesia, the key to reducing the carbon footprint is to decrease electricity consumption by improving the thermal efficiency of heating furnaces. CO2 emissions from the magnesite decomposition process can best be managed through capture and reuse. Overall, it is recommended that various enterprises should take action to implement CO2 recycling.

Three-dimensional modeling of biomass fuel flow in a circulating fluidized bed furnace with an experimentally derived momentum exchange model

In modeling of large-scale circulating fluidized bed (CFB) furnaces, semi-empirical 3D process models are used in furnace analysis, design and optimization as their accuracy versus computational times make them more favorable than high resolution computational fluid dynamics (CFD) in many engineering type of studies. One of the key aspects in determining the furnace performance and efficiency is the correct modeling of the fuel flow as it determines where the thermochemical reactions take place in the furnace, affecting the temperature and gaseous species distributions. In modeling, this requires the suitable approximation of the momentum exchange between the fuel and the gas phase as well as the fuel and the bed material. To model the momentum exchange with current models presented in the literature, information on the material properties, namely the fuel particle size has to be given. The determination of particle size is affected by the particle shape and for irregular, non-spherical material, such as biomass, currently there are no readily applicable methods to determine the effective momentum exchange based on the particle geometry.In this work, a new gas–fuel momentum exchange model is developed for the fuel flow, which acknowledges the effect of physical properties of the fuel, namely the shape and size. Due to impracticality of determining a representative fuel particle size, characterization data is utilized to directly obtain information on the gas–fuel momentum exchange and the particles are classified based on their elutriation behavior, rather than particle size. The new momentum exchange model is utilized with an existing semi-empirical 3D process model and applied in simulation of a utility-scale CFB furnace firing biomass. The simulation results are compared with measurements and are found to be in good agreement, which demonstrates the applicability of the modeling approach. The presented method improves the modeling of fuel flow with CFB process models, especially with irregular, non-spherical fuels such as biomass. The improved modeling of fuel flow within large-scale CFB furnaces enables faster and more reliable design and analysis of CFB furnaces.

Electro- or Turbo-Driven?—Analysis of Different Blast Processes of Blast Furnace

There has always been a dispute about the energy efficiency and energy cost of electro-driven and turbo-driven blast furnace (BF) blast processes. In order to find where the problem lies, energy efficiency analysis models and energy cost analysis models of electro-driven and turbo-driven blast processes were established, and the differences between the two driving processes in terms of theoretical minimum steam consumption, energy efficiency and energy cost were studied. The results showed that the theoretical minimum steam consumption of a blast process depends on steam thermodynamic properties and is unrelated to drive mode and drive process. A certain overlapped interval between electro-driven and turbo-driven blast processes in terms of energy efficiency exists. The equation for calculating the standard coal coefficient of steam was proposed, and the relationship to judge strengths and weaknesses of the two driving modes in terms of energy efficiency and energy cost was established. Finally, two companies were selected for case study research. The results led to different conclusions because of the differences between energy media in terms of standard coal coefficient and unit price. To select the best driving mode, plant-running conditions and energy prices of the region of operation in addition to other relevant factors should all be taken into account.

Analysis of electric arc furnaces efficiency via frequency spectrum-based arc coverage detection

We introduce the analysis of variables measured outside a direct current electric arc furnace that are related to the arc coverage and its electric energy efficiency. We derive an on-line reference to the arc coverage suitable for control decisions. In order to do so, we study the furnace shell vibration frequency spectrum as structure-borne sound sensed by a microphone. The data is analysed using real time software tools to obtain the sound signal spectrum associated with arc coverage likewise related to the optimal performance of the furnace. A statistical test is performed to prove the relationship between sound and electric energy efficiency.

Measurements of temperature and gas composition within the burning bed of wet woody residues in a 4 MW moving grate boiler

Moving grate firing systems are widely used for biomass combustion. The characteristics of the fuel bed combustion in moving grate boilers are of practical interest as they are directly related to the release of pollutants and affect the furnace efficiency. Measurements of temperature and gas species concentrations inside the fuel bed are necessary to improve our understanding of the highly complex processes involved in biomass combustion. There have been few experimental studies of the fuel bed of industrial scale grate furnaces. The present study measured temperature and gas species concentrations within a thick burning bed of wet woody biomass, in a 4MW reciprocating grate boiler. Measurements were carried out under three different operating conditions through ports located in the wall of the furnace using a stainless steel probe incorporating a thermocouple. Temperatures of about 1000°C were measured close to the grate, indicating intense combustion at the bottom of the fuel bed. The temperature distribution along the bed height showed that different stages of the combustion process take place in horizontally adjacent layers along the grate. Higher flow rates of the primary air resulted in relatively higher CO and lower CO2 and NO concentrations in the fuel bed.

Evaluation of Furnaces Performance of Glass Factories in Thailand

The objective of this project is to evaluate the energy consumption and the efficiency of glass melting furnaces using a thermodynamic principle and heat (energy) balance analysis. The approach can carry out more accurate result of wall losses than the direct temperature measurement at the furnace walls. Six furnaces from different factories in Thailand were studied. To construct the heat balance of glass furnace, the amount of heat for melting raw materials batch to glass melt (Hex), input energy (Hin) and the heat of content of offgas had to be known. The heat (energy) balance indicated the performance of glass furnaces in term of energy consumption.Glass furnace, Efficiency, Heat balance

Economic Feasibility Study of an HTS DC Induction Furnace

Conventional induction furnaces have been in operation in nonferrous metal and related industries with poor energy efficiencies of only 50-60%. Moreover, the efficiency of atmosphere furnace, one of the various heating facilities for metal billets, is about 20%. For ensuring high energy efficiency in these heating furnaces fields, as one of the better counterplans, a novel dc induction heating method using HTS magnets has been suggested. To realize the HTS dc induction furnace (HIF) in the industrial field, the most important issue is to guarantee economic favor in comparison with two different types of conventional furnaces. In this paper, we performed an economic feasibility study of an HIF in terms of electricity fee minimization. Net present value, internal rate of return, and pay-back period methods were used to evaluate the investment returns of an HIF. All indicators related to direct benefits were calculated and analyzed for finding economic feasibility. The analysis results will be applied to decision making process for the commercialization of the HIF.

Numerical simulation of copper recovery from converter slags by the utilisation of spent potlining (SPL) from aluminium electrolytic cells

An innovative method was devised to improve copper recovery and operational efficiency of the Cu converter slag-cleaning furnace, by utilising both carbon and fluoride values of an otherwise environmental hazardous material (i.e. spent potlining (SPL)) produced from the aluminium industry. Results based on numerical modelling show that 90% Cu recovery could be achieved by adding as little as 3–4 wt-% of SPL to the molten converter slag. The fluorides and sodium-containing compounds in the SPL reduced the slag viscosity, resulting in a much faster settling rate of matte droplets. In this process, the SPL could be detoxified by destroying the cyanides to form harmless N2 gas, and inertising the fluorides in a much diluted form in the ferro-silicate slag, ensuring a safe disposal to the environment.

Effects of excess air and preheating on the flow pattern and efficiency of the radiative section of a fired heater

Since boilers and industrial furnaces are one of the largest consumers of fossil fuels, optimization and retrofitting these facilities are of the most essential tasks which can be done to reduce fuel consumption and pollutant emission into the environment. The objective of this paper is to investigate the effects of excess air and inlet air preheating on temperature, flow, and efficiency of the furnace of a fired heater used in an oil refinery. For this purpose, a three-dimensional modeling was performed, using CFD, to simulate the furnace and one of the swirling bluff-body burners. Examining the result of several turbulence and radiation models, it was found that Reynolds stress model (RSM) can simulate turbulence caused by swirling and bluff-body burners more precisely than k–ε models. Moreover, discrete ordinate (DO) model offers better performance than P1, for radiation. Comparisons between the numerical results, and field measurements showed the simulation can predict the flow and temperature fields in the heater with acceptable accuracy. The results show that internal and external recirculation zones (IRZ & ERZ) are caused by swirling and bluff-body flows, respectively. In addition, the flow is asymmetric and two recirculation zones form near the vertical walls. Variation of excess air has more impact on IRZ, and high percentage of excess air leads to narrower IRZ, while preheating totally affects ERZ. The optimal value of excess air is 18% and increasing excess air beyond 18% reduces the flame temperature and the furnace efficiency. Furthermore, it is found that preheating increases the furnace temperature as well as the efficiency, and the effect of preheating is reduced at high inlet temperatures.

Fundamental research on iron coke hot briquette – A new type burden used in blast furnace

In order to improve blast furnace efficiency, reduce CO2 emission and accelerate energy utilisation, a new preparation process of iron coke hot briquette (ICHB) based on the raw materials conditions in China, a new type blast furnace ironmaking burden, was experimentally investigated in this paper. The new preparation process was researched and optimised through single factor experiment and orthogonal experiment. Meanwhile, the reactivity and the post-reaction strength of ICHB prepared under the optimised conditions were tested and the effect of ICHB on the thermal performance of conventional coke was researched. In addition, softening and dripping properties of mixed burden with optimised ICHB charging was simultaneously investigated. The results showed that the optimised preparation parameters of ICHB include 15% iron ore, 65% bituminous coal, 350°C hot briquetting temperature, 1100°C carbonisation temperature and 4 hours carbonisation time. The reactivity and the post-reaction strength of ICHB prepared under the optimisation conditions are 62.4 and 10.6%, respectively. ICHB has protective effect on conventional coke and the protective effect is more obvious with 10% ICHB adding. With the increase of ICHB charging ratio, softening interval T40–T4 of mixed burden is widened while melting interval TD–TS (namely cohesive zone) is narrowed. Additionally, the permeability of mixed burden becomes better and dripping ratio is first increased then decreased. The suitable charging ratio of ICHB in mixed burden is about 30%.

Performance of an effectively integrated biomass multi-stage gasification system and a steel industry heat treatment furnace

The challenges of replacing fossil fuel with renewable energy in steel industry furnaces include not only reducing CO2 emissions but also increasing the system energy efficiency. In this work, a multi-stage gasification system is chosen for the integration with a heat treatment furnace in the steel powder industry to recover different rank/temperature waste heat back to the biomass gasification system, resulting higher system energy efficiency.A system model based on Aspen Plus was developed for the proposed integrated system considering all steps, including biomass drying, pyrolysis, gasification and the combustion of syngas in the furnace. Both low temperature (up to 400°C) and high temperature (up to 700°C) heat recovery possibilities were analysed in terms of energy efficiency by optimizing the biomass pretreatment temperature.The required process conditions of the furnace can be achieved by using syngas. No major changes to the furnace, combustion technology or flue gas handling system are necessary for this fuel switching. Only a slight revamp of the burner system and a new waste heat recovery system from the flue gases are required.Both the furnace efficiency and gasifier system efficiency are improved by integration with the waste heat recovery. The heat recovery from the hot furnace flue gas for biomass drying and steam superheating is the most promising option from an energy efficiency point of view. This option recovers two thirds of the available waste heat, according to the pinch analysis performed. Generally, depending on the extent of flue gas heat recovery, the system can sustain up to 65% feedstock moisture content at the highest pyrolysis temperature studied.

Comparative performance evaluation of blast furnace flame temperature prediction using artificial intelligence and statistical methods

The blast furnace (BF) is the heart of the integrated iron and steel industry and used to produce melted iron as raw material for steel. The BF has very complicated process to be modeled as it depends on multivariable process inputs and disturbances. It is very important to minimize operational costs and reduce material and fuel consumption in order to optimize overall furnace efficiency and stability, and also to improve the lifetime of the furnace within this task. Therefore, if the actual flame temperature value is predicted and controlled properly, then the operators can maintain fuel distribution such as oxygen enrichment, blast moisture, cold blast temperature, cold blast flow, coke to ore ratio, and pulverized coal injection parameters in advance considering the thermal state changes accordingly. In this paper, artificial neural network (ANN), multiple linear regression (MLR), and autoregressive integrated moving average (ARIMA) models are employed to forecast and track furnace flame temperature selecting the most appropriate inputs that affect this process parameter. All data were collected from Erdemir Blast Furnace No. 2, located in Ere\u{g}li, Turkey, during 3 months of operation and the computational results are satisfactory in terms of the selected performance criteria: regression coefficient and root mean squared error. When the proposed model outputs are considered for the comparison, it is seen that the ANN models show better performance than the MLR and ARIMA models.

Numerical Analysis of Influential Parameters on the Performance of Vertical-Cylindrical Refinery Furnaces

An integrated heat transfer modeling of vertical-cylindrical refinery furnaces was carried out to determine the influential parameters on the fired heaters efficiency as well as the process and flue gas temperature variations. The model was developed considering separate sections of the heater encompassing heat of the flue gas. The model was solved by an iterative procedure with initial boundary conditions. The developed model along with its solution was compiled in MATLAB R2013a environment. The parameters involved into the devised model form the basis for the determination of the most influential parameters on the performance of fired heaters. The sensitivity analysis was accomplished via examining five parameters including excess air, tube pitch, inlet air temperature, fuel composition, and fuel flow rate. Model validation reveals that the model results reasonably agree with the experimental data with less than 4% deviation. The sensitivity analysis demonstrated that varying the five influential parameters by 5% from a base case altered the furnace efficiency by 2.69%, 0.93%, 0.22%, 0.21%, and 0.07%, respectively. The devised model can be employed to reduce computing time and technical costs afforded by the use of computational fluid dynamics (CFD) analysis.

Radiative modelling by the zonal method and WSGG model in inhomogeneous axisymmetric cylindrical enclosure

Nongray radiation calculations are carried out for a case problem available in the literature. The problem is a non-isothermal and inhomogeneous CO2-H2O- N2 gas mixture confined within an axisymmetric cylindrical furnace. The numerical procedure is based on the zonal method associated with the weighted sum of gray gases (WSGG) model. The effect of the wall emissivity on the heat flux losses is discussed. It is shown that this property affects strongly the furnace efficiency and that the most important heat fluxes are those leaving through the circumferential boundary. The numerical procedure adopted in this work is found to be effective and may be relied on to simulate coupled turbulent combustion-radiation in fired furnaces.

Analysis of gas-fired NH3-H2O generator with cross flow gas burner

This paper presents a model to simulate the combined heat and mass transfer processes that occur in a gas-fired generator of an ammonia water absorption heat pump. The model comprises three interconnected components: the gas furnace, the distillation column and the rectifier. The furnace is modeled like a well-stirred single volume. The distillation column and the rectifier are discretized along their axial dimension. Several heat transfer mechanisms are simultaneously solved: radiative and convective heat transfer between combustion products and generator finned surface, flow boiling and pool boiling in the two-phase ammonia water mixture inside the distillation column. The model is applied to operating conditions of interest in real applications. The generated outputs provide insight on the internal gradients, the quantification of gas furnace efficiency, and effectiveness of solution boiling and internal heat recovery. The model can be used for the simulation of absorption heat pumps with modulating gas burners.

Mineral Matter in Nigerian Coals and Tar Sand and Their Implications in Binary Blend Formulation and Co-Carbonisation

Abstract In blend simulation for metallurgical applications, the knowledge of the type and amount of mineral matter in coal and other additives, as well as their derivatives as a result of combustion is important in assessing the coke quality and blast furnace efficiency. X-ray diffraction (XRD) and X-ray fluorescence (XRF) techniques were used in assessing the mineral matter contents and oxides produced up on combustion of the following Nigerian coals: Afuze (AFZ), Garin-Maiganga (GMG), Lamza (LMZ), Shankodi-Jangwa (SKJ), and Chikila (CHK) in addition to a tar sand from Ondo (OTS). Coal samples from Afuze (AFZ) and Chikila (CHK) were found to contain quartz, hematite, and anhydride as the dominant minerals. The Garin-Maiganga coal sample (GMG) was found to contain quartz, magnetite, anhydride, and magnesite. Quartz and hematite were dominant in Lamza coal (LMZ), while Shankodi-Jangwa coal (SKJ) is associated with dolomite and quartz. The bitumen was found to contain quartz, kaolinite, and rutile. The XRF analysis revealed the presence of sixteen elemental oxides: the most abundant being silicon dioxide, ferric oxide, aluminium oxide, sulphur trioxide, calcium oxide, and titanium oxide. Amongst the coal samples, CHK, AFZ and GMG coals have low acidic/basic and basic/acidic ratios, which indicate that cokes originating from them may form the least slag with the best blast furnace efficiency.