Frank R. Steward

Gas composition, temperature and pressure measurements in a lead blast furnace

Measurements of the gas composition, temperature and pressure within a commercial lead blast furnace are presented. These measurements are interpreted in terms of an oxygen potential diagram from which the thermodynamic driving force for various reduction reactions may be seen. A semiquantitative model of the furnace is presented. The effects of oxygen enrichment of the air blast are discussed.

Initiation step of boiling liquid expanding vapour explosions

Abstract Two sets of experiments have been performed to study the initiation of a BLEVE (Boiling Liquid Expanding Vapour Explosion). One litre tanks were caused to BLEVE while the pressure at the end of the tank was recorded. Experiments were then conducted in a shock tube equipped with windows. Liquid at the same conditions as the previous experiments was suddenly exposed to atmospheric pressure while a spark schlieren photograph was taken and the pressure response recorded. R12 and R22 were the fluids used in these experiments. Results show that the initial drop in pressure is followed by a rapid pressure rise, caused by the boiling of liquid. The initial depressurization results in superheated liquid in the vicinity of the break. The homogeneous nucleation of this liquid results in a local explosion. The blast wave from this explosion can be the cause for the catastrophic failure of the container. This study shows that a BLEVE is an explosion which can be initiated by the depressurization of a pressure-liquefied gas through a break. This depressurization causes the fluid near the break to be in a superheated state. There is a local explosion caused by a rapid, homogeneous boiling of this superheated fluid. Pressure records indicate that the local explosion near the break in the tank occurs before the expansion wave has propagated far from the break. The blast wave from the explosion eventually stops any further boiling. The volume of the fluid involved in the initial explosion determines the magnitude of the blast (pressure) wave. The blast wave is the cause for the catastrophic failure of the container as observed in many accidents.

Energy Aspects of a Lead Blast Furnace

The energy effects accompanying the processing of the feed material to a lead blast furnace are considered in terms of a reversible model. Relative to this model the efficiencies of operating furnaces are found to be in the range 18 to 35 pct. The effects of the effluent gas CO2/CO ratio and temperature and oxygen enrichment of the blast air in the thermodynamic efficiency are quantified. Improvements in efficiency achieved in industrial furnaces as a result of oxygen enrichment of the blast air are substantially greater than those predicted. Mass and enthalpy balances on an industrial lead blast furnace are presented from which it is estimated that approximately 9 pct of the carbon charged to the furnace is lost due to the solution loss reaction in the upper regions of the furnace.

Exergy analysis of a chemical metallurgical process

The concept of available work or exergy is used to develop an expression from which the causes of exergy losses in a chemical reactor are identified. The concept is illustrated by application to a lead blast furnace. The performance of the sinter plant and the lead smelter are assessed by the same procedures. The possibilities of exergy recovery are discussed and a heat pump installation is described. The advantages of the exergy method of process assessment relative to the traditional heat balance are discussed.

Modeling Two-Phase Flow in Pipe Bends

In order to have a better understanding of the interaction between the two-phase steam-water coolant in the outlet feeder pipes of the primary heat transport system of some CANDU reactors and the piping material, themalhydraulic modelling is being performed with a commercial computational fluid dynamics (CFD) code-FLUENT 6.1. The modeling has attempted to describe the results of flow visualization experiments performed in a transparent feeder pipe with air-water mixtures at temperatures below 55°C. The CFD code solves two sets of transport equations-one for each phase. Both phases are first treated separately as homogeneous. Coupling is achieved through pressure and interphase exchange coefficients. A symmetric drag model is employed to describe the interaction between the phases. The geometry and flow regime of interest are a 73 deg bend in a 5.9 cm diameter pipe containing water with a Reynolds number of ∼IE5-IE6. The modeling predicted single-phase pressure drop and flow accurately. For two-phase flow with an air voidage of 5-50%, the pressure drop measurements were less well predicted. Furthermore, the observation that an air-water mixture tended to flow toward the outside of the bend while a single-phase liquid layer developed at the inside of the bend was not predicted. The CFD modeling requires further development for this type of geometry with two-phase flow of high voidage.

Comparative analysis of the consumption of energy of two wood pulping processes

Abstract Equations are presented for the cumulative energy analysis of a process with numerous recycle streams and multiple products. The equations enable a quantitative assessment for alternative processes in the production of a particular product. This method was applied to the production of chemical pulp from wood by the Kraft process and a proposed alcohol extraction process. The Kraft process was found to be superior to the alcohol extraction process in terms of specific cumulative energy consumption for the production of chemical pulp (50% consistency) as the only useful product: 14.5 vs. 19.9 MJ/kg. However, if by products of the alcohol extraction process are considered as useful products, the specific cumulative energy consumption of the chemical pulp is reduced to 12.3 MJ/kg, which is below that of the Kraft process. Cogeneration of steam and electricity decreases the specific energy consumption for pulp production significantly for both processes. Various cogeneration strategies will be presented for the two processes.

Henry's law constant for hydrogen in natural water and deuterium in heavy water

The results of measurements of the Henrys law constant near infinite dilution are reported for solutions of H2 in H2O and D2 in D2O at high temperatures (170∽300°C). The experimental procedure involved the use of a palladium/hydrogen (or deuterium) electrical resistance sensor. Values of KH∞ for H2–H2O solutions agree closely with published data. Values of KH∞ for D2–D2O solutions are lower than those for H2–H2O solutions. With increasing concentrations of H2 in H2O and D2 in D2O the Henrys law coefficients decrease. This is attributed to non-ideality in the gas phase.

Optimum arrangement and use of heat pumps in recovering waste heat

Abstract Relations are derived for the coefficient of performance of heat pump systems used to transfer heat from a low temperature heat source stream to a high temperature heat sink stream. The manner of use and operation of a number of heat pumps in such a system has been determined for the thermodynamic optimum for reversible and irreversible heat pumps.