Blast Air Research Articles

CLASSIFICATION OF LOCAL EXERGETIC LOSSES IN HEAT RECOVERY SYSTEMS OF DIFFERENT TYPES

The results of classification and analysis of local exergy losses in heat recovery systems of various types are presented. The combined heat recovery system of a boiler plant, designed for heating water and blast air, as well as heat recovery systems with anti-corrosion methods for protecting gas exhaust tracts, are considered. On the examples of these systems, a classification of local exergy losses was carried out and their type and place in heat recovery systems were established. For research, a complex methodology was used, combining structural-variant methods of exergy analysis with methods for presenting exergy balances in matrix form. Structural diagrams of heat recovery systems are presented and exergy equations are obtained for calculating exergy losses in places of localization. For a combined heat recovery system, a comparative analysis of local exergy losses was carried out. It has been established that the smallest exergy losses are observed in the hot air heat exchanger and in the gas heater. The total contribution to the total exergy losses of the pumping system and the piping system is quite significant for all boiler power values. With an increase in boiler power from 30 to 70% of the installed power, there is a slight increase in exergy losses in the heat recovery system and in the hot water heat recovery unit. In this section, the main exergy losses are in the pumping system and in the pipeline system. With a further increase in the power of the boiler, the exergy losses in the heat recovery system and in the hot water heat recovery unit begin to increase more significantly. In this case, the main exergy losses fall on the hot water heat exchanger. It is concluded that the optimal mode of operation of the installation is carried out at the boiler power, which is 50 ... 60% of its installed power.

Damage assessment of prefabricated prestressed channel slab under plane charge blast

The study of the mechanical properties of prestressed concrete channel slabs under different plane charge air blasts for applications in civil defense engineering is significant. For this reason, similar simulation tests were conducted on the anti-explosive performance of three 1:3 scale prestressed concrete channel slabs under 9 times plane charge air blast. The positive duration was more than 260 ms to simulate the uniform distribution load of a strong blast air shock wave on the prestressed concrete channel slab. The results showed that the designed prestressed concrete channel slab had good displacement ductility without brittle destruction, which significantly reduced the damage of the blasting impact on the structure. The channel slab could resist an air shock load of 0.467 MPa without damage. On the other hand, the positive duration was not only related to the quality of the overlying soil but also related to the air shock wave overpressure design value. The channel plate is regarded as a rigid-plastic component to calculate its plastic dynamic response under explosive load. In addition, the reliability of the theoretical calculation results and ABAQUS software simulation were verified by experimental data, which provided a feasible analytical method for calculation and simulation research in civil air defense engineering.

Granulation performance by hybrid centrifugal-air blast technique for treatment of liquid slag

Dry centrifugal granulation technique for treatment of liquid blast furnace (BF) slag stands out by its compact structure, easy adjustability, and smaller energy consumption. It is crucial to obtain fine particle characteristics for achieving high granulation performance and then high heat recovery rate. A three-dimensional model was established in this paper to describe theparticle characteristics of liquid BF slag by new hybrid centrifugal-air blast granulation technique. The intuitive granulation evolutions, particle mass distribution, and size uniformity, were acquired as well as accumulative mass fraction. As a result, the vertical breakage effect of blast air (20 m/s) accelerated the granulation process and led to a reduction of 14–18% in particle size, with more obvious optimization effect at low disk speed. Moreover, the general prediction correlation of particles size suitable for both the hybrid centrifugal-air blast technique and the classical centrifugal granulation technique, was established to optimize the granulation performance.

Optimization of geometric parameters and analysis of exergy efficiency of heat recovery units glass furnaces

The paper presents the results of optimization of the geometric parameters of the heat exchange surface of water and air-heating heat exchangers of glass-making furnaces and an analysis of their exergy efficiency. Ensuring the efficient operation of heat recovery units in various thermal circuits is an urgent problem of heat power engineering. The aim of the work is to establish the optimal areas of the geometric parameters of the heat exchange surface of heat recovery units of glass-melting furnaces and to analyze their exergy efficiency. The paper presents the results of solving the tasks necessary to achieve the goal: - using statistical methods for planning the experiment, determine the levels of variation of the parameters of the geometric surface of heat transfer for the heat recovery units under study and calculate the values of the criteria for evaluating the efficiency at the points of the central orthogonal compositional plan; - to obtain the regression equations for the investigated heat exchangers, to determine the optimal areas of change in the geometric parameters of the heat exchange surface and the corresponding exergy efficiency criteria. To determine the optimal areas of geometric parameters of the heat exchange surface, a complex methodology is used based on the methods of exergy analysis and statistical methods of the theory of experiment planning. It has been established that when designing heat recovery schemes for heating water in heat supply systems and for heating blast air, heat recovery units with the following values of the areas of variation of the geometric parameters of the heat exchange surface can be used: - the values of the area of variation of the distance between the panels for heat recovery units with a staggered and corridor arrangement of pipes in a bundle s1 = 58.0-62.0 mm. - the values of the areas of change in the diameter of pipes for a hot water heat exchanger with a corridor arrangement of pipes d = 41.0-43.0 mm and for an air heating heat exchanger with a staggered and corridor arrangement of pipes d = 29.0-31.0 mm. - the use of the values of the ranges of change of other parameters is carried out taking into account additional technological factors. It has been established that the exergy efficiency of hot water heat recovery units is in all cases higher than the exergy efficiency of air heating units. For hot water heat exchangers, the values of exergy criteria are lower than for air heating ones: k – 2.0 times, ε – by 7.5%, m0 – 1.9 times. The expediency of using the investigated heat recovery units in heat recovery circuits of glass melting furnaces has been established, taking into account the results obtained and in the presence of certain technological factors. The results obtained and further developments in the field of optimization of the operating parameters of heat recovery units for glass-melting furnaces will provide an increase in the efficiency of heat recovery equipment for power plants.

Simulation and Application of NOX Emission Characteristics in the Vertical Flue of 6 m Coke Oven

In view of the formation process of nitrogen oxide in the vertical flue of coke oven, a three-dimensional steady-state mathematical model of heat transfer, mass transfer and combustion process was established, and the numerical method was used to solve the problem. The effects of exhaust gas circulation ratio, preheating temperature of blast furnace gas and air and the blending ratio of coke oven gas on the NOX generation characteristics were studied. The above parameters were further optimized to the model that was applied to 6-m coke oven of Ansteel. The results show that the numerical simulation results are in good agreement with theoretical combustion temperature and the NOX emission data of 6-m coke oven in Ansteel. Through the optimization scheme, the preheating temperature of gas and air is the most significant one, followed by ratio of exhaust gas circulation and coke oven gas blending. The optimized model is applied to 6 m coke oven of Ansteel, and the average content of NOX in the exhaust gas is reduced from 364 to 228 mg/m3, with good effect.

Blast-Induced Noise Level Prediction Model Based on Brain Inspired Emotional Neural Network

Although a major portion of the emitted energy from mine blast is sub-audible (lower frequency), there exist a component that is audible (high frequencies from 20 Hz to 20 KHz) and as such within the range of human hearing as noise. Unlike blast air overpressure (low frequency occurrence), noise prediction from mine blasting has received little scholarly attention in mining sciences. Noise from mine blast is considered a major detrimental blasting effect and can be a menace to nearby residents and workers in the mine. In this paper, a blast-induced noise level prediction model based on Brain Inspired Emotional Neural Network (BENN) is presented. The objective of this paper was to investigate the implementation possibility of the proposed BENN approach along with six other artificial intelligent methods, such as Backpropagation Neural Network (BPNN), Radial Basis Function Neural Network (RBFNN), Generalised Regression Neural Network (GRNN), Group Method of Data Handling (GMDH), Least Squares Support Vector Machine (LSSVM) and Support Vector Machine (SVM). The study also implemented the standard Multiple Linear Regression (MLR) for comparison purposes. The statistical analysis carried out revealed that the BENN performed better than the other investigated methods. Thus, the BENN achieved very promising testing results of 1.619 dB, 3.076%, 0.0925%, 0.911 and 82.956% for root mean squared error (RMSE), mean absolute percentage error (MAPE), normalised root mean squared error (NRMSE), correlation coefficient (R) and variance accounted for (VAF). The implemented BENN can be useful in managing noise from mine blasting using site specific data.

Numerical investigation of bus stop structures in Seoul for the reduction of fine dust entry

Fences and air curtains can effectively reduce fine dust entry into roadside bus structures, thus decreasing the exposure of passengers to particulate matter. In this study, bus stop structures that reduce the entry of fine dust formed or dispersed by vehicles was derived through simulation models. These bus stop structures consist of a fence that blocks particle entry from a relatively low position in front of the bus stop and an air blast structure that blocks particle entry from a relatively high position. Three bus stop styles were considered: a bus stop without a fence, that with a vertical flat fence, and that with a vertical curved fence toward the road. Among these styles, the curved fence model was superior to other models, and particle entry into the bus stop was estimated to be reduced by 15.5% for the curved fence model compared with the model without a fence. After the selection of the fence model, three air blast structures were considered: canopy, wall, and fence types, which blast air from the ceiling of the bus stop, toward the direction of the road from the rear wall of the bus stop, and upward from the top of the curved fence, respectively. The canopy-type air blast structure was found to be the most effective in decreasing particle entry into bus stops, with a reduction rate of 88% compared with the reference model without a fence and air blast system.

Effect of Shock Wave on Constant Load Behaviour of Pb-Free/Cnt Solder Joint

The constant load behaviour of SAC305 solder joint with addition of carbon nanotube (CNT), exposed to shock wave condition was investigated. Formulated SAC305-CNT solder pastes with 0.04 wt. % CNT were manually printed to the printed circuit board (PCB) with copper surface finish to form solder joint. The solder joint was exposed to the shock wave condition via open field blast air test using Trinitrotoluene (TNT) explosive. Nanoindentation approach was used to determine the constant load behavior of the SAC305-CNT solder joint under shock wave condition. The results showed that addition of CNT reduced the indentation depth of SAC305 solder joint at 10 mN peak load for blast test sample and control sample. Indentation depth displacement of SAC305-CNT solder joint for blast test sample and control sample were reduced about ~ 42 and ~56%, respectively, if compared to the SAC305 solder joint for blast test sample and control sample. SAC305-CNT solder joint was experienced minimal changes of stress exponent when exposed to the shock wave. The existence of CNT in the solder joint slows down the depth displacement due to constant load.

From Henry Bessemer’s invention to comprehensive converter process optimization

The Bessemer process enabling to produce high-quality steels was implemented at steel mills of the Urals region more than 200 years ago. At the beginning of the 20th century, the process was modified by scientists from the Mining Institute and was then adopted by copper and nickel alloy producers. The converter process became one of the key processing stages with Russian copper and nickel smelters. This paper examines certain ways to improve the tuyere air flow in a horizontal converter. The authors came up with a generic equation for calculating specific blast air pressure and discuss the use of hydrothermal and aerodynamic techniques for tuyere purging. The blast air limit was determined for a horizontal converter that is characterized with massive melt ejections. The authors demonstrate that, in spite of all the process and design improvements, the modern converter process still has three major drawbacks. They include process cycling, the gas ductwork not being completely tight, unbalanced thermal and chemical status of the vessel leading to excessive thermal and chemical loads on the tuyere zone and incomplete slag formation in zones that are farther from the tuyeres. Research work is ongoing on a novel continuous converter design which involves the use of special-design unsubmerged tuyeres. Such tuyeres produce spatially oriented high-pressure blasts which enable consistent rotation of the molten matte in a tight cylindrical vessel.

The blast air preheating of an power boiler CHP ZIGM

To improve the efficiency of the steam-turbine thermal power plant by reducing heat loss in a cold source by regenerating part of the heat of condensation of steam exhaust in the turbine, it is proposed to preheat the boiler blast air in a heat exchanger with circulating water heated in a steam turbine condenser. Saving of heat energy in monetary terms due to the use of part of the heat of condensation of steam in the turbine during preheating of the blast air of the ener-gy boiler BKZ-420-140 NGM of the Samara Thermal Power Plant to 20 °C is 13.244 mln rub/year. The design of an air-preheating unit for preheating the blast air of the power boiler BKZ-420-140 NGM has been developed, in which the heating coolant is circulating water heated in a steam turbine condenser. Variant calculations were carried out, as a result of which the main thermal performance parameters of the installation were determined at different boiler loads and outdoor temperatures.

Predicting the reliability of auxiliary equipment of heat sources

Service equipment of the heat sources taken by supervision consisted of centrifugal water pumps, blast air fans and exhausters. Robust and fail safe operation of the heat sources is impossible without the effective operation of this service equipment. Malfunctions of the service equipment resгде in disruption of heat supply, losses and emergencies. Consequently, to provide a robust operation of the equipment there were found the impending failure, classified and described. The main type of the electric engines used for the electric drive of the working organs of the service equipment are asynchronous electric drives with a short-circuited rotor which is mostly exposed to the external influence. In this work there are collected and analyzed reasons of fault inception of the service equipment as well as methods to define the complex parameter of technical state is developed and its functional dependence on failure interval is set. The acquired data may be used to define the readiness of the equipment for operation to the coming period as well as plan its maintenance operation and overhaul.

ENHANCING THE ENERGY AND ENVIRONMENTAL EFFICIENCY OF SURFACE HEAT EXCHANGERS OF SMOKE GASES OF WATER BOILER HOUSES

Background. In water-heating boiler houses, where natural gas is burned to produce heat in the form of hot water, it is necessary to reduce its consumption by reducing the temperature of the wasting flue gases from the boilers and, accordingly, increasing their efficiency. But nowadays, a more important problem is the problem of environmental protection, one of the directions of its solution is the reduction of emissions of nitrogen oxides with flue gases in gas boiler houses. Objective. The purpose of the paper is to improve the energy efficiency of moderate-centralized and centralized heating boiler houses by reducing the temperature of the exhaust flue gases and the beneficial use of heat in heat exchangers for own needs of the boiler houses or external consumers, and optimize the operating modes of the surface heat exchangers for humidification of blast air, used for reducing nitrogen oxide emissions. Methods. The analysis of the influence of surface utilizers of the temperature and moisture content of humidified air fed into the boiler furnaces on the energetic and environmental efficiency was made by using the numerical calculation method. Results. The dependences of the bypass coefficient, the specific amount of the heat removed from the heaters and its increment from the final flue gas cooling temperature, as well as the emissions of nitrogen oxides into the environment when humidifying blast air with temperatures of 50 and 60 °С, at various initial flue gas temperatures in the range of 140–190 °C were obtained. Conclusions. It is shown that, from the point of view of practical implementation in boiler houses, air humidification at the temperature of 50 °C is the main priority, while its moisture content is 85 g/kg d.a., and the flue gas at the inlet to the utilizer is 190 g/kg d.g. the optimum temperature of the gases leaving the air heater is 27–32 °C, the bypass coefficient is 0.26–0.33, the specific amount of the heat removed from the heaters compared to the non-humidified mode can be increased by 28%, and the emissions of nitrogen oxides with flue gases into the environment can be reduced by more than 3 times.

Theoretical and practical research on relationship between blast air condition and hearth activity in large blast furnace

From the results calculated by theoretical derivations, it was found that the characteristics of tuyere raceway determined by the operation condition for blast air played a critical effect on the heart activity. The speed and kinetic energy of blast air should be proportional to the volume of blast furnace (BF), and the comprehensive optimization of air volume and tuyere which should vary with the quality of raw materials was essential. The calculation methods of air volume ratio and coefficient for different BFs were put forward. Moreover, the details on hearth activity recovery of a 4747 m3 blast furnace in China were elaborated. Based on the extensive experience in blast furnace production, the various phenomena used to judge air speed and kinetic energy whether reasonable were discussed. In summary, hearth activity was closely related to the characteristics of BF raceway and reasonable air speed and kinetic energy could effectively improve the activity.

Preheating Boiler Blast Air with Exhaust Gases in Cooling Them Below the Dew Point

It has been suggested that, before being fed into the boiler′s air heater, blast air be preheated in a condensation surface heat exchanger with natural combustion products cooled below the dew point. A thermal calculation has been made of a condensation heat exchanger installed behind a BKZ-420-140 NGM power boiler, which has made it possible to determine for different values of the temperature of ambient air: the heating power of the heat exchanger, the consumption of exhaust gases for preheating boiler blast air provided they are cooled below the dew point, the share of exhaust gases delivered to the heat exchanger, consumption of the steam condensate from gas fuel combustion products, the temperature, moisture content, and dew point of the exhaust gases on exit from the boiler unit, the increase in the boiler′s combustion efficiency due to the work of the condensation heat exchanger, the coefficient of heat transfer from the gases to the wall and from the wall to the air being heated, and the heat-exchange coefficient. It has been established that the share of the exhaust gases supplied to the heat exchanger for preheating the blast air of a BKZ-420-140 NGM boiler with cooling them below the dew point, depending on the ambient air temperature, is 3.9–20.7% and 7.6–24.4% of their amount in heating the air to 20 and 30°C respectively. A calculation has been made of economic efficiency due to preheating the blast air of the BKZ-420-140 NGM boiler at the Samara Heat and Electric Power Plant of the Samara Branch of the PJSC (Public Joint-Stock Company) "T Plus" in the condensation heat exchanger installed behind it.

Improvements to Mixing of Natural Gas and Hot-Air Blast in the Air Tuyeres of Blast Furnaces with Thermal Insulation of the Blast Duct

Using natural gas as an additional fuel in a blast furnace is known to reduce coke consumption during blast-furnace production. In a standard tuyere, the hot blast pushes the natural gas up against the surface of the blast duct, resulting in poor mixing between the natural gas and the hot blast, which in turn leads to incomplete combustion and pyrolysis of the natural gas. One approach for improving mixing between the natural gas and the hot blast is to modify the blast-channel geometry. An engineering design solution was proposed, and the gas dynamics, thermal conditions, and stress/strain state of the air tuyere for this solution were analyzed via ANSYS modeling. Toroidal protrusions on an insert near the outlet of the air tuyere (swirlers) or on the gas inlet nozzle flange (rim) were considered; these protrusions also protect the insert against premature damage in areas subject to the most severe mechanical damage. The following assumptions were made: The model scope includes both the fluid medium within the blast duct and the thermal insulation insert, i.e., this can be thought of as a conjugate heat exchange problem, and heat transfer to the cooling system water was taken into account using the generalized boundary conditions. We show that modifying the insert geometry so that there is a protrusion on the working surface or installing a rim in the area where the insert starts to show damage, will increase mixing of the natural gas into the blast air and during combustion. This then increases the blast temperature at the tuyere outlet, which in turn increases the natural-gas flow rate and reduces coke usage. A similar result was achieved for wear on the insert.

Using Oxygen-Enriched Blast During the Operation of Shaft Furnaces of the Mednogorsk Copper–Sulfur Combine LLC

The practice of shaft smelting of copper-bearing charge using oxygen-enriched air at the Mednogorsk Copper–Sulfur Combine is considered. After increasing the rate of oxygen enrichment of the blast air from 30 to 36%, the output increased by 20.1% and the copper content was 33.0–35.3% in the matte and 0.5% Cu in the waste slag. The material and heat balances are presented. The effect of increasing the rate of oxygen enrichment on the furnace productivity, solid fuel consumption, composition and amount of smelting products is shown.

Investigation of the possibility of carbon dioxide reduction by Waelz processing of oxidized zinc-containing material

The results of model studies on the possibility of reducing energy costs and carbon dioxide emissions during the Waelz processing of oxidized zinc-containing material in waelz kilns are presented. The studies were carried out using a specialized software product METSIM widely known in the world practice of metallurgical process and production modeling that allows analyzing the effect of changes in technological modes on the final results of the process. Model calculations showed that the greatest decrease in specific energy consumption and CO 2 emissions is observed when using blast air heated to 200 °C with an increase in its flow rate from 1000 to 7000 n.m 3 /h and concomitant decrease in atmospheric air suction. The estimated reduction in the specific costs of carbon and CO 2 emissions amounted to 30,2—35,5 %, and the total specific cost of energy carriers — 28—32 %. At the same time, blast air heating to 200 °C in the heat exchanger of the recovery boiler does not require additional energy inputs, in contrast to the use of oxygen blast with the cost of electricity for producing oxygen. Intensification of the waelz process using additional oxygen blasting (or air blast enrichment with oxygen) and heated blast air supply with concomitant decrease in air suction into the furnace from the atmosphere leads not only to a decrease in the specific consumption of the carbon energy carrier, but also to an increase in the degree of carbon utilization. The maximum estimated increase in the degree of carbon utilization was 6,2 rel.% — from 60,3 % on cold air blast without oxygen to 66,5 % on an air-oxygen blast (7000 n.m 3 /h of air and 185 n.m 3 /h of oxygen) heated up to 200 °C without atmospheric air. Maintaining optimal oxidation-reduction and thermal modes of the process requires correct regulation of the kiln draft mode taking into account atmospheric air suction in the unloading head of the kiln. Uncoordinated changes in the specific consumptions of charge, carbon, blast air and rarefaction in the dust chamber lead to a concomitant decrease in the extraction of zinc to sublimates and increase in its losses with clinker.

Numerical Simulation on Dynamics and Heat Transfer Characteristics of Granulated Molten Slag Particle by Air with Moisture

In order to investigate the dynamics and heat transfer characteristics of granulated molten blast furnace slag by blast air, a mathematical model for the dynamics and heat transfer of high temperature molten slag granulated b... | Find, read and cite all the research you need on Tech Science Press

Field Tests on the Attenuation Characteristics of the Blast Air Waves in a Long Road Tunnel: A Case Study

After an explosion occurs in a tunnel, the blast waves take on diverse forms of attenuation in different regions when it propagates along the tunnel. However, the prediction of the overpressure decay laws proposed in previous studies has not taken into account the influence of the different regions in the tunnel. The present paper uses the example of the Micangshan highway tunnel in China and considers many factors that influence the propagation of the blast waves by dividing the tunnel into four zones. The paper modifies the decay equation proposed by Smith and applies it to the Micangshan highway tunnel in China. The decay equations are different in different zones. Field tests in this tunnel show that the modified equation is more suitable to describe the attenuation of the blast waves in the tunnel than the original equation.

On a certain method of power boiler blast air pre-heating

The method for preliminary heating of boiler blast air has been developed; as per this method, the air before being blown to boiler air heater is pre-heated with exhaust natural gas combus-tion products in surface heat exchanger with combustion products cooled below dew point temperature. It is suggested to use water vapor condensate produced by this process as heat system make-up water. Thermal calculation for condensing heat exchanger installed down-stream of BKZ-420-140 NGM power boiler is made, as a result of the calculation, the following parameters were obtained for different values of ambient air: heating power of heat exchanger; consumption of exhaust gases for pre-heating of boiler blast air provided that they are cooled below dew point temperature; proportion of exhaust gases transferred to heat ex-changer; consumption of water vapor condensate produced from gas fuel combustion prod-ucts; temperature, moisture content and dew point of exhaust gases on exit of boiler unit; in-crease in boiler fuel consumption coefficient due to operation of condensing heat exchanger; heat transfer coefficient. Cost effectiveness due to pre-heating of BKZ-420-140 NGM boiler blast air in condensing surface heat exchanger at Samara Power Station has been determined.