A comparison of thermal condition between pilot- and full-scale furnaces for studying slagging and fouling propensity in PF boilers

The Australian Coal Industry Research Laboratory (ACIRL) furnace is scaled to simulate slagging and fouling in operating boilers. This requires that the gas and target temperatures, the heat flux, and the flow pattern be the same as those in real boilers. The gas and target temperatures are maintained by insulating the wall and cooling the target respectively. The flow pattern of a small burner cannot be the same as a large furnace. However, this flow pattern is partially compensated for by placing the slagging panels in three vertical locations. The paper develops the models of radiant heat transfer from the flame to the deposits both in pilot-scale and full-scale furnaces. They are used to compare the effective radiant heat transfer of the pilot- and full-scale furnaces. The experimental data both from the pilot- and full-scale furnaces are used to verify the incident heat flux and temperature profiles in the pilot- and full-scale furnaces. The results showed that the thermal condition in the pilot-scale furnace meets the requirements for studying the slagging regarding the gas temperature and the incident heat flux, particularly for the panel #1. The gas temperature in the convective section also meets the requirement for studying the fouling.

Radiative Heat Transfer in Boiler Furnaces

Better models are needed for radiative heat transfer in boiler furnaces. If the process is known better, combustion in the furnace can be optimized to produce low emissions. It makes the process to be environmental friendly. Furthermore, if there is a better model of the furnace it can more fully explain what is happening inside the furnace. Using of the model one can quickly and easily analyze how it operates with bio fuels, moist fuels or difficult fuels and improve the operation. Models helps with better estimation of furnace dimensions and result in more accurate understanding of operation. Key component lacking in these models is radiative heat transfer in particle laden gases. If there are no particles than radiative heat transfer can be calculated approximately. There are two problems with current models when used with flow modeling. The first one is a need to account for a particle laden gas and the second one is an absence of a fast algorithm. Fast calculation is needed if radiative heat transfer calculation is done for a large CDF model. Computations slow down if time is required for calculating radiative properties over and over again. This thesis presents a band model for radiative heat transfer in boiler furnaces. Advantage is a quickness of calculation and account of particles in the process.

Modeling of fireside deposit formation in two industrial furnaces

Fireside deposits can be found in many types of utility and industrial furnaces. The deposits in furnaces are problematic because they can reduce heat transfer, block gas paths and cause corrosion. To tackle these problems, it is vital to estimate the influence of deposits on heat transfer, to minimize deposit formation and to optimize deposit removal. It is beneficial to have a good understanding of the mechanisms of fireside deposit formation. Numerical modeling is a powerful tool for investigating the heat transfer in furnaces, and it can provide valuable information for understanding the mechanisms of deposit formation. In addition, a sub-model of deposit formation is generally an essential part of a comprehensive furnace model. This work investigates two specific processes of fireside deposit formation in two industrial furnaces. The first process is the slagging wall found in furnaces with molten deposits running on the wall. A slagging wall model is developed to take into account the two-layer structure of the deposits. With the slagging wall model, the thickness and the surface temperature of the molten deposit layer can be calculated. The slagging wall model is used to predict the surface temperature and the heat transfer to a specific section of a super-heater tube panel with the boundary condition obtained from a Kraft recovery furnace model. The slagging wall model is also incorporated into the computational fluid dynamics (CFD)-based Kraft recovery furnace model and applied on the lower furnace walls. The implementation of the slagging wall model includes a grid simplification scheme. The wall surface temperature calculated with the slagging wall model is used as the heat transfer boundary condition. Simulation of a Kraft recovery furnace is performed, and it is compared with two other cases and measurements. In the two other cases, a uniform wall surface temperature and a wall surface temperature calculated with a char bed burning model are used as the heat transfer boundary conditions. In this particular furnace, the wall surface temperatures from the three cases are similar and are in the correct range of the measurements. Nevertheless, the wall surface temperature profiles with the slagging wall model and the char bed burning model are different because the deposits are represented differently in the two models. In addition, the slagging wall model is proven to be computationally efficient. The second process is deposit formation due to thermophoresis of fine particles to the heat transfer surface. This process is considered in the simulation of a heat recovery boiler of the flash smelting process. In order to determine if the small dust particles stay on the wall, a criterion based on the analysis of forces acting on the particle is applied. Time-dependent simulation of deposit formation in the heat recovery boiler is carried out and the influence of deposits on heat transfer is investigated. The locations prone to deposit formation are also identified in the heat recovery boiler. Modeling of the two processes in the two industrial furnaces enhances the overall understanding of the processes. The sub-models developed in this work can be applied in other similar deposit formation processes with carefully-defined boundary conditions.

Receipt from G. Lloyd, dealer in hot air furnaces, stoves, ranges, gas fixtures and pumps

Receipt from G. Lloyd, dealer in hot air furnaces, stoves, ranges, gas fixtures and pumps, located on King Street, St. Catharines regarding payment received for burners, dampers and other gas fixtures, Jan. 1, 1875.

Province of Ontario Patent issued to Cyrus Dean of St. Catharines for a machine for effecting more perfect combustion of fuel in the furnaces of locomotives

Province of Ontario Patent issued to Cyrus Dean of St. Catharines for a machine for effecting more perfect combustion of fuel in the furnaces of locomotives. This patent was listed in the Records Office of the Registrar General of Canada in Lib. JE, folio 361. This patent is accompanied by a 36 cm. x 57 cm. detailed sketch and explanation of the machine. [Samuel D. Woodruff was the assignee of Cyrus Dean in a in a patent for a rotary washing machine in November of 1869 according to The Commissioners of Patents' Journal by the Great Britain Patent Office], March 23, 1870.

Synthesis and characterization of CaBi4Ti4O15 thin films annealed by microwave and conventional furnaces

CaBi4Ti4O15 thin films were deposited by the polymeric precursor method and crystallized in a domestic microwave oven and conventional furnace. The films obtained for microwave energy are well-adhered, homogeneous and with good specularity, when treated at 700 degrees C for 10 min. The microstructure and the structure of the films can be tuned by adjusting the crystallization conditions. When microwave oven is employed, the films presented bigger grains with mean grain size around 80 nm. For comparison, films were also prepared by the conventional furnace at 700 degrees C for 2 h. (C) 2007 Elsevier Masson SAS. All rights reserved.

Polycyclic aromatic hydrocarbons from wood pyrolyis in charcoal production furnaces

Polycyclic aromatic hydrocarbons (PAH) were measured in smoke samples from wood carbonization during charcoal production, in both particulate matter (PM) and gaseous phases. Samples were acquired using a medium-volume air sampler at 1.5 m distance from the furnace. Particle-bound PAH were collected on Fluoropore polytetrafluoroethylene filters and gas-phase PAH were collected into sorbent tubes with XAD-2 resin. PAH were extracted with dichloromethane-methanol and analyzed using gas chromatography-mass spectrometry. The results showed total emission from the furnace of 26 mu g/m(3) for the 16 PAH and 2.8 mu g/m(3) for the 10 genotoxic PAH (from fluoranthene to benzo[g,h,i]perylene). High emission of 16 PAH in the first 8 h of wood carbonization was detected (64 mu g/m(3); 56% of the total emission). Associated with PM, 11% of the total emission of 16 PAH (in both phases) and 60% of 10 genotoxic PAH were found. Relative ratios (for example, [Phe]/[Phe] + [Ant]) for the PAH of the same molecular weight were obtained and compared with the published data. The concentrations of benzo[a]pyrene equivalent (BaPeq) were estimated using the list of toxic equivalent factors suggested by Nisbet and LaGoy, 1992. The values of 0.30 and 0.06 mg/m3 were obtained for the total concentrations of BaPeq in PM and gaseous phase, respectively. (c) 2006 Elsevier B.V. All rights reserved.

Foundry sand recycling in the troughs of blast furnaces: a technical note

The foundry sand agglomerated with alkaline phenolic resin, used for the manufacture of molds, was found to be a residue which is able to be recycled, minimizing the costs of disposal and the environmental impact. This paper analyzes the thermomechanical regeneration and leaching processes and also assesses the influence of additives on the improvement of the mechanical properties of the sands. Besides, the industrial experiments carried out at CSN aiming at the foundry sand recycling in the covering of the blast furnace troughs are presented. (C) 2003 Elsevier B.V. All rights reserved.

Synthesis, structural refinement and optical behavior of CaTiO3 powders: A comparative study of processing in different furnaces

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Retention characteristics of lanthanum-doped bismuth titanate films annealed at different furnaces

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Probabilistic neural network to predict cracks in taphole mud used in blast furnaces

One of the major problems facing Blast Furnaces is the occurrence of cracks in taphole mud, as the underlying causes are not easily identifiable. The absence of this knowledge makes it difficult the use of conventional techniques for predictability and mitigation. This paper will address the application of Probabilistic Neural Network using the Matlab software as a means to detect and control such cracks. The most relevant BF operational variables were picked through the statistic tool "Principal Component Analysis - PCA." Based upon the selection of these variables a probabilistic neural network was built. A set of BF operational data, consisting of 30 controlling variables, was divided into 2 groups, one of which for network training, and the other one to validate the neural network. The neural network got 98% of the cases right. The results show the effectiveness of this tool for crack prediction in relation to clay intrinsic properties and as a result of the fluctuation in operational variables.

Analysis of aluminum plates under heating in electrical and natural gas furnaces

This paper analyzes the thermal storage characteristics of aluminum plates in furnaces during their heating for lamination under two sources of heat: an electrical resistance bank and a combustion process carried out with natural gas. The set of equations to model the furnace under operation with electrical energy, for air as the fluid, is presented. This supports the theoretical analysis for the system under operation with natural gas combustion products. A numerical procedure, using the software ANSYS, is applied to determine the convection heat transfer coefficients for heating by the air flow. Temperatures measured in a plate inside a real furnace are used as parameters to determine these coefficients. Then convection and radiation heat transfer coefficients are determined for the natural gas combustion products. Results are compared, indicating a possible gain of 5.5 h in relation to a 19.5 h period of conventional electrical heating per plate.

Nationalization of the carbonaceous mortar for injection in the CNS's blast furnaces hearths

The consumption of the carbonaceous mortar for injection in the CSN's blast furnaces hearth has increased in the last years, as a function of the modern situation of the blast furnaces com paign. Allied to the growing consumption background, the devaluation of the Brazilian currency stroke hardly the importation costs of this product.

Analysis of oxy-fuel combustion as an alternative to combustion with air in metal reheating furnaces

Using oxygen instead of air in a burning process is at present being widely discussed as an option to reduce CO2 emissions. One of the possibilities is to maintain the combustion reaction at the same energy release level as burning with air, which reduces fuel consumption and the emission rates of CO2. A thermal simulation was made for metal reheating furnaces, which operate at a temperature in the range of 1150-1250 degrees C, using natural gas with a 5% excess of oxygen, maintaining fixed values for pressure and combustion temperature. The theoretical results show that it is possible to reduce the consumption of fuel, and this reduction depends on the amount of heat that can be recovered during the air pre-heating process. The analysis was further conducted by considering the 2012 costs of natural gas and oxygen in Brazil. The use of oxygen showed to be economically viable for large furnaces that operate with conventional heat recovering systems (those that provide pre-heated air at temperatures near 400 degrees C). (C) 2014 Elsevier Ltd. All rights reserved.

Mathematical modelling of pulverized coal furnaces

The goal of this paper is to show how mathematics and computational science can help to design not only the geometry but also the operation conditions of different parts of a pulverized coal power plant.