Diesel Emissions Reduction Using a Catalyst and Water Scrubber for Underground Mine Applications

BS 6680 requires the efficiency of coalmine diesel engine exhaust pollution-reduction devices to be determined. The efficiency of an Englehard PTX catalyst and water scubber for both particulate and gaseous emissions reduction was determined using a 533 cc single-cylinder Petter AVI direct injection diesel engine. The separate and combined influence of the two exhaust devices was determined. The water scrubber acted as aflame trap as well as an exhaust particulate trap. The catalyst gave a substantial reduction in CO and UHC gaseous emissions and particulate SOF emissions for exhaust temperatures above 250°C. However, the high MW particulate SOF, including the PAH, had a 70 per cent reduction for catalyst temperatures as low as 200°C. The water scrubber was the dominant particulate removal device, although the catalyst removal efficiency was significant for temperatures above 250° C. The scrubber also had a significant influence on the reduction in NOx emissions, with a 30 per cent removal at high exhaust temperatures.

Flameproof Diesel Engines in Underground Coalmines in Britain—design Features and Operational Experience

The use of flameproofed diesel engines in underground mines of the British coalmining industry has a history approaching fifty years. During that time, the design of the flameproof package has seen considerable changes, due both to normal evolutionary processes and to changes to statutory requirements, the most recent of which is the introduction of BS 6680 (1). This paper briefly reviews the design changes that have occurred and describes the design features of typical current units. Today's units are inevitably more complex than those which were first introduced, owing to more stringent safety requirements; this has an impact on reliability and maintenance which is discussed, along with general operational experience. The implications of the introduction of BS 6680 on future designs are also discussed, together with recent and current research and development aimed at reducing the size and cost of the flameproof unit.

A Model for Combustion Losses in a Pulverized Fuel Fired Power Plant Boiler

A model for the estimation of combustion losses in a pulverized fuel power plant boiler is presented. The model is based on the formulation of a probability density function which relates the probability of a fuel particle remaining unburnt to the combustion and resident times. An empirical model is also presented which relates the unburnt carbon loss to average particle size and excess air. The two models are shown to be in close agreement with each other. The models are validated from the experiments on a power plant boiler. The dependence of boiler efficiency on particle size and excess air is also examined and an empirical correlation between optimum excess air and particle size is derived. The mechanism of two-way coupling between boiler and turbine side parameters is also illustrated. It has been shown that the optimum excess air levels for maxima in plant heat rate and boiler efficiency are not the same, since the two-way coupling influences both the turbine heat rate and boiler efficiency. The effect of two-way coupling has been found to be more predominant for particle sizes of the order of 200 μm.

Submarine Power Systems Using the V4-275R Stirling Engine

The Stirling power module V4-275R, integrated with a liquid oxygen system, is currently built for submarines for the Royal Swedish Navy and for the offshore company Comex in France. Since mid 1985 the Stirling engine system for the Swedish Navy has been successfully tested in a full-scale submarine test section. The next step in this programme will be an integration of the Stirling system into an operational Swedish submarine. A contract has been signed having Kockums as the main contractor. The French programme means a 500 ton manned diver lock-out submarine, the SAGA I, which is under final construction at Comex in Marseille. The energy system for the SAGA submarine consists of two V4–275R Stirling engines of maximum 100 kW power each. The oxygen storage, manufactured by AGA Cryo in Gothenburg, consists of two liquid oxygen tanks providing a total capacity of 10000 kWh, allowing the submarine to perform missions of up to 14 days submerged.

On the Optimum Utilization of Water Hammer

The computerized method of characteristics was used to analyse, for a single pipeline discharging into the atmosphere, the effects of valve-closure schedule and pipe length on optimum water-hammer strength. It was found that the criteria of optimum water-hammer utilization are a non-linear inherent valve schedule in which the bulk of the pressure surge occurs near the beginning or towards the end of valve closure, together with as small a value of dimensionless valve-closure time and as high a value of wide-open valve area as is consistent with cavitation-free operation. Also, a comparison of the results with hydraulic ram test data suggests that optimum drive pipe length may be based solely on optimum water-hammer strength, in the light of the relative effects of pipe friction and dimensionless valve-closure time. In general, optimum pipe length is not highly sensitive to inherent valve-closure schedule, water-hammer strength, pipe size or reservoir head.

Estimating the Performance of Gas Turbine Heat-Recovery Boilers Off-Design

In installations where a gas turbine is coupled to a steam prime mover through an exhaust heat steam generator, the need may arise to estimate the behaviour of the latter away from its specified design conditions. For example, the performance of the steam generator when the gas turbine is operating away from its design conditions may be of fundamental importance in relation to the economics of a proposed coupled installation. In particular, it determines inter alia the extent to which supplementary firing may be required. A question closely related to that of the off-design performance of a given exhaust heat steam generator is that of evaluating the comparative merits as regards thermal performance of designs differing in the layout and configuration of the heat-transfer surfaces when tendered for the same specified duty. (The need for such assessments frequently arises in the examination of competitive tenders.) The paper discusses briefly procedures allowing the influences of the interrelated heat balances of the heat-transfer surfaces, of the heat-transfer surface geometry and of the steam and gas physical properties to be analysed separately and integrated into a computational procedure permitting their combined effect on performance to be determined with sufficient accuracy.

Optimizing the Co-Generation Coefficient in District Heating and the Co-Generation of Heat and Electricity

The co-generation coefficient a plays an important part in district heating. In order to save more primary energy and obtain comprehensive benefits, α3 must be optimized in design.

Perception of Plant Design

The case is argued that true mechanical engineering designers in the process industries are often underutilized due to certain constraints placed upon their work. Creative thought is suppressed if designers are employed in the wrong environment. There are some activities, often referred to as design, that in fact have no design characteristics and are essentially solely analytical excercises. However, opportunities do exist for designers to practice their talents to the full, so enabling them to make a greater contribution to their company's business than has hitherto been possible. Some examples are presented where designers may be gainfully employed, and a reappraisal of the role of engineering designers is called for.