Furnace Chamber Research Articles

Influence of calcining temperature on the pozzolanic characteristics of elephant grass ash

The influence of calcining temperature on the pozzolanic properties of elephant grass ash (EGA) for application as a supplementary cementitious material is reported. Five different calcining temperatures were used (ranging from 500 to 900 °C for 3 h at 100 °C increments) after a first calcining step at 350 °C for 3 h, a 10 °C/min heating rate, and a 0.04 constant volumetric ratio between the sample and the internal furnace chamber. After calcining and high energy grinding, all ashes were characterized based on particle size distribution, oxide composition, loss on ignition, B.E.T. specific surface area, X-ray diffraction, and scanning electron microscopy. The pozzolanic behavior was investigated based on pozzolanic activity index test and compressive strength of concretes up to 180 days of curing. An expressive decrease in loss on ignition values and, consequently, increase in silica content of EGA produced at higher temperatures were observed. Overall, the results demonstrated that 600 °C was the most suitable temperature for producing EGA. Additionally, the replacement of 20% (in volume) of cement by 600 °C-calcining EGA did not change significantly the 28-day compressive strength of concrete, and increased the strength after 180 days of curing in relation to a reference concrete.

A numerical study on the combustion process for various configurations of burners in the novel ultra-supercritical BP-680 boiler furnace chamber

This paper presents preliminary results of numerical investigations into the combustion process in the BP-680 boiler furnace chamber with swirl burners placed on the furnace front wall. The calculations were performed using the ANSYS FLUENT commercial code. The swirl burner operates with the secondary air swirl angle of 50°. The boiler is supplied by outermost sets of mills – the mills and either the bottom or the upper burners. A proposal is made to change the secondary air swirl angle to 45°. Therefore, four cases of the furnace chamber operation are simulated: the furnace is supplied by either the bottom or the upper burners with the secondary air swirl angle of either 50° or 45°. It is found that a reduction in the secondary air swirl angle in the burner from 50 to 45° extends and carries the flame away from the waterwalls. Comparative charts of CO and O2 contents in flue gases, of the flue gas temperature and of the heat flux along the height of the furnace chamber for the four cases under analysis are presented.

Low-temperature ignition of droplets of suspension organic water–carbon fuels

The conditions and integral characteristics of stable low-temperature ignition of droplets of suspension organic water–coal fuels are established by using the means of high-speed video-detection. The oxidizer temperature for these conditions varies in the range of 600–900 K (much below the temperatures in furnace chambers of modern power installations exceeding 1200 K). The velocity of the oxidizer-flow motion varies from 0.5 to 5 m/s, and the sizes (conditional radii) of droplets vary from 0.5 to 1.5 mm. The times of initiation of burning under conditions of low-temperature heating and the duration of the complete combustion of droplets of the corresponding compositions of organic water-coal fuels are determined. The necessary and sufficient conditions of stable ignition are singled out for promising organic water–coal fuels.

Simulation of heat transfer in combustion chamber waterwall tubes of supercritical steam boilers

Abstract The paper presents the results of numerical computations performed for the furnace chamber waterwalls of a supercritical boiler with a steam output of 2400 × 103 kg/h. A model of distributed parameters is proposed for the waterwall operation simulation. It is based on the solution of equations describing the mass, momentum and energy conservation laws. The aim of the calculations was to determine the distribution of enthalpy, mass flow and fluid pressure in tubes. The balance equations can be brought to a form where on the left-hand side space derivatives, and on the right-hand side – time derivatives are obtained. The time derivatives on the right-hand side were replaced with backward difference quotients. This system of ordinary differential equations was solved using the Runge-Kutta method. The calculation also takes account of the variable thermal load of the chamber along its height. This thermal load distribution is known from the calculations of the heat exchange in the combustion chamber. The calculations were carried out with the zone method.

Development of Metakaolin as a Pozzolanic Material from Local Natural Material, Soorh

This research aims to investigate and present the effect of extent of temperature and duration of heating on the pozzolanic properties and reactivity of the local available natural material, Soorh. The Soorh is activated by heating in a furnace chamber at temperatures 650, 700, 750 and \({800~^{\circ} {\rm C}}\) for 2, 3 and 6 h and at 900 and \({1000~^{\circ} {\rm C}}\) for 2-h duration. The energy- dispersive spectrometry and X-ray diffraction (XRD) are conducted to verify the presence of silica content and amorphous silica in developed metakaolin. The strength activity index (SAI) of developed metakaolin is determined with 20 % replacement of cement with metakaolin as per ASTM. The obtained results of SAI verdict that the optimal activation temperature is \({800~^{\circ} {\rm C}}\) with 2-h duration. The XRD analysis confirmed pozzolanic activity of developed metakaolin and validated the results of SAI. Moreover, it is observed that the activated metakaolin has an appreciable influence on the increase in compressive strength of the mortars.

Experimental investigation of convective heat exchange in chamber furnaces at heat treatment of cylindrical solids

In this paper, the process of convective heat exchange between the cooling air and the cylindrical solid is experimentally studied in a chamber furnace at double-sided cross-flow around the solid, and the corresponding criterial equation is obtained.

Dust formation in the arc heating of zinc-plated steel

Dust formation in the plasma-arc heating of zinc-plated steel in argon is studied, when the current is 170–190 A, the argon flow rate is 0.06 m3/h, and the pressure in the furnace chamber is 0.1 MPa. Zinc evaporates practically completely in the first 30 s of heating. The structure of the trapped zinc-bearing dust is heterogeneous: the particles are of different shape (spherical, acicular, or membranous particles), different size, and different composition. The composition of individual dust particles is analyzed on an iCAP 6300 spectrometer (Thermo Electron, United States). On that basis, their oxide composition is estimated by means of Terra software. The dust includes particles consisting of ZnO, Fe2O4, carbon, and pure iron. The results indicate that, in the plasma heating of zinc-plated steel, the zinc-bearing dust may be captured separately from the other dust in the initial smelting period.

Vermicular kaolinite relics in fly ash derived from Bokaro and Jharia coals (Jharkhand, India)

During a study of fly ash from two pulverized fuel power plants (Bokaro and Chandrapura) burning coal from the Bokaro Coalfield in Jharkand state, India, glassy and vermicular mineral forms were found associated with the char. A combination of optical microscopy, XRD, SEM/EDS, and XRF analysis has shown that this morphotype, reported here for the first time, originated from kaolinite that expanded during heating inside the furnace chamber under relatively low combustion temperatures. The morphotype has an internal structure that resembles the fanning-out structure formed during vermicular kaolinite development.

The effect of heating power on impurity formation and transport during the holding phase in a Bridgman furnace for directional solidification of multi-crystalline silicon

Oxygen and carbon are the most common impurities in multi-crystalline silicon. The general mechanism for formation and transport of O and C in the solidification furnace is as follows: oxygen from the silica crucible comes into the melt and combines with a silicon atom and evaporates at the gas/melt interface in the form of silicon oxide (SiO). Argon inert gas, injected into the furnace chamber, carries the SiO to the hot graphite fixtures, where it reacts with carbon to form carbon monoxide (CO) and silicon carbide (SiC). CO is carried by the gas to the melt free surface, where it dissociates into carbon and oxygen. Finally, during solidification oxygen and carbon are incorporated into the crystal. A global furnace model accounting for heat transfer, melt flow, gas flow and impurity transport has been applied to investigate the oxygen and carbon formation and transport in a vertical Bridgman furnace during the holding phase when the furnace is at its hottest. A case study is performed to investigate the effect of the applied heating power on the carbon and oxygen concentrations in the melt prior to solidification.

Thermal stability of NdBCO/YBCO/MgO thin film seeds

Thermal stability of the Nd1+xBa2−xCu3O7−δ (Nd-123 or NdBCO) thin films deposited on MgO substrate, with YBa2Cu3O7−δ (Y-123 or YBCO) buffer layer (NdBCO/YBCO/MgO thin film), has been experimentally studied in order to determine the optimal film thickness acting as seed for bulk YBCO growth. YBCO bulk superconductors with Y2BaCuO5 (Y-211) and CeO2 addition were prepared by the top seeded melt growth process in a chamber furnace using NdBCO/YBCO/MgO thin film seeds of different thicknesses (200–700 nm with 20 nm YBCO buffer layer) and different maximum temperatures, Tmax. The maximum temperatures varied in the range of 1040 °C–1125 °C. The highest thermal stability 1118 °C was observed in the case of NdBCO/YBCO/MgO thin film of 300 nm thickness. These results are corroborated with differential scanning calorimetry and high temperature x-ray diffraction measurements, as well as microstructure observations.

Production of Hydrogen‐Rich Syngas from Lignite using Different Pyrolysis Methods

AbstractThe efficiency of hydrogen production by the pyrolysis of lignite from Dongsheng in Inner Mongolia was investigated. Three pyrolysis methods, namely, temperature‐programmed pyrolysis, isothermal pyrolysis, and microwave pyrolysis, were applied and compared. The online analysis of the composition of the pyrolysis gas showed the effects of the different pyrolysis methods on the gas composition and the yield of hydrogen. The reasons were discussed on the basis of infrared thermography of the semicoke samples, FTIR spectroscopy, and SEM analysis. The microwave pyrolysis was improved by the addition of a shimming device to the furnace chamber. Consequently, the efficiency of hydrogen production by the pyrolysis of lignite was increased substantially, and the yield of hydrogen surged by 430 % compared with the yield for the original microwave pyrolysis.

Modeling of dynamic properties thermal systems' using fuzzy approach

The paper presents the fuzzy model which enables to calculate temperature changes in the flat resistive wall of the furnace chamber. The rules the model is based on, are associated with the thermal state of object, more specifically with the instantaneous changes of its temperature. By using the concepts of initial time constant, initial gain, saturation time constant, saturation gain good approximation of temperature changes in a flat wall of resistance chamber furnace has been achieved.

Thermal calculation for a furnace with three-tiered near-wall burners

The paper considers using a differential method for thermal calculation of a furnace with finding the thermal and aerodynamic parameters within the radiation chamber of a tube furnace. The furnace is equipped with acoustictype burners allocated in three tiers on the lateral walls. The method implies joint numerical solution of 2D radiation transfer equations using the S 2-approximation of the discrete ordinate method, of energy equations, flow equations, k-e turbulence model, and single-stage modeling of gas fuel combustion. Typical results of simulation are presented.

Computational fluid dynamic analysis of innovative design of solar-biomass hybrid dryer: An experimental validation

A solar-biomass hybrid dryer is designed and constructed for natural rubber sheet drying. The dryer consists of solar collector cum drying chamber, heat exchanger and biomass furnace. There is indirect heating of rubber sheet instead of direct exposure to smoke in ribbed smoked rubber drying. An attempt has been done to reduce consumption of biomass by introducing solar energy application. Computational fluid dynamics technique is used to simulate the temperature and air flow distributions in an innovative design of drying chamber. The simulation results for temperature are found very close to experimental values in terms of statistical parameters. CFD simulation is done for air flow distribution inside solar-biomass hybrid dryer to ensure the utility of air circulating fans. The solar-biomass hybrid dryer is tested for drying of 100 number of natural rubber sheets. Moisture content of rubber sheet is reduced from 34.26% to 0.34% (db) in only 48 h, a notable reduction in drying time as well as consumption of biomass. The color and texture of the natural rubber sheet were noticed better than the traditional smoke rubber drying.

Combustion and NOx Emission Characteristics of Shenmu Char in a Circulating Fluidized Bed with Post-combustion

Combustion and NOx emission characteristics of Shenmu char have been investigated in a circulating fluidized bed test platform composed of a circulating fluidized bed and a post-combustion chamber. The effect of the combustion temperature in the circulating fluidized bed furnace and arrangement of post-combustion air were examined on the post-combustion of Shenmu char. NOx emission is below 100 mg/m3 in all post-combustion experiments. The effect of the temperature in the circulating fluidized bed furnace or post-combustion chamber on NOx emission is not obvious. When the post-combustion air injection position moves upstream, NOx emission decreases. In a reducing atmosphere, most fuel nitrogen is converted to N2. NOx is mainly formed from the reaction of residual N in the char contained in fly ash and O2 from post-combustion air in the post-combustion chamber. Nitrogen in char is gradually released and converted during combustion and not instantaneously.

Numerical investigation of combustion of biomass, methane, and gasoil fuels and emissions from a furnace chamber

ABSTRACTThe aim of this study was to compare gaseous emissions from the combustion of conventional fuels (methane and gasoil) and biomass fuels (wood and peat) by the application of the CFD code FLUENT software in a furnace combustion chamber. According to the results, the combustion temperature obtained for conventional fuels was higher than it obtained for biomass fuels. Results also showed significantly lower emissions of CO2, NOx, and soot with the combustion of biomass compared to the methane and gasoil, but SO2 emissions from combustion of the conventional fuels were higher than that of biomass fuels. Also, results showed that the quantity of gaseous emissions is closely related to combustion temperature, molecular structure, and fuel characteristics.

INVESTIGATION OF LINING PARAMETERS IMPACT ONTO METAL AIR-COOLING PROCESS IN CHAMBER FURNACE

The appropriate mathematical model was created for the investigation of lining parameters impact onto metal air-cooling process in chamber furnace. Numerical computing for various lining composition was conducted: fully dense refractory material, made from chamotte brick; refractory ceramic fi bers on the wall and arch with fully dense refractory of hearth; conceptual lining of entire chamber furnace with refractory ceramic fi bers. Processing of the results allowed to illustrate the impact of the lining type on the length of aircooling process, thereby showing possible reserves for accelerating of this process step.

Сравнительное исследование насыщающей способности борирующих сред различного состава

Comparison of the ability of saturating media for Boriding based on boron carbide and amorphous boron and mixtures for simultaneous saturation of boron, chromium and titanium. As the object of study were selected boride coatings on carbon steels: 45 and U8A. Borating made from powder mixtures in a chamber furnace. The Microstructure and the thickness of the diffusion coatings was investigated on cross microsections by optical microscopy. Identification boride phases produced by the "color etching" and with the help of X-ray diffraction. It is shown that while saturation with boron, chromium and titanium carbon steel, diffusion processes are much more intense. Introduction inside the boriding mixture carbide-forming elements such as chromium and titanium, facilitates significant acceleration of diffusion of boron within steels 45 and U8A. With simultaneous multicomponent saturation with boron, titanium and chromium the rate of formation of the diffusion layer on the carbon steels higher than under one-component boriding. In the case of multicomponent saturation boron together with the strong carbide-forming elements (chromium and titanium) increase the carbon content of the saturated carbon steel of 0.45 to 0.8 wt.% has little effect on the formation of a diffusion layer in contrast to the one-component boron saturation. In case of the one-component boriding carbon steels, content the carbon of the steel is significantly affects both the thickness and of microstructure of the boride coating. With simultaneous saturation the carbon steels of boron, titanium and chromium carbon content of the steel is practically no effect on the diffusion coating thickness.

Evaporator Heating with Optimum Fluid Temperature Changes

In order to speed up the boiler start-up, especially from the cold state, the boiler evaporator may be flooded with hot water at the beginning of the process. The temperature of water supplied to the boiler evaporator through lower chambers of the boiler furnace chamber waterwalls will be found from the condition of equality between allowable stresses and circumferential thermal stresses on the edge of the opening for the downcomer. Two mathematical models of the evaporator hot-water heating are presented in this paper – one with lumped and the other with distributed parameters. In both cases, the water level is identical. The hot water needed to fill the boiler evaporator may be supplied from the feed water tank of another operating boiler or from a hot water vessel.

Система диагностики теплового состояния металла в камерной печи

Система диагностики теплового состояния металла в камерной печи