Bjørn Qvale

Ignition Delay in the Dual Fuel Engine

Tests have been conducted on a special compression ignition research engine to investigate the effects of gaseous fuels on the ignition delay in dual fuel engines. Diesel oil, n-heptane, or cetane were used as pilot fuels, and hydrogen, carbon monoxide, or methane were inducted in the intake manifold. Induction of nitrogen was used as a reference to eliminate the influence of changes in oxygen concentration and specific heats. Helium was inducted in additional tests. From the results of a number of parameter variations, the cylinder charge temperature (determined by intake temperature and compression ratio), the pilot fuel amount, and the flow of combustible gas were found to have the most significant influence on the ignition delay.

Simplification of process integration studies in intermediate size industries

Abstract It can be argued that the largest potential for energy savings based on process integration is in the intermediate size industry. But this is also the industrial scale in which it is most difficult to make the introduction of energy saving measures economically interesting. The reasons are that the required engineering effort is too great and therefore too expensive, and that the resulting systems designs often become inordinately complex and therefore not attractive in operation. The present study describes steps that aim at reducing the magnitude of the theoretical work and engineering effort associated with a given process integration study in an intermediate size industry. This is based on the observation that the systems that eventually result from a process integration project and that are economically and operationally most interesting are also quite simple. Four steps that may be used separately or in series ahead of or simultaneously with the conventional process integration procedures (for example, the pinch point method) are described and are applied to an industrial case study. It might be feared that the use of preselections and groupings would limit the “freedom of movement” and therefore lead to non-optimal economic solutions, which may be right. But the objective of the optimisation is not to reach the best economic solution, but to relatively quickly develop the design of a simple and operationally friendly network without losing too much energy saving potential.

The consequences of unpredictable development of economic conditions on heat exchanger network configurations and economic results

Abstract The work reported in the present paper was carried out in connection with a comprehensive process integration study of a fertiliser plant in Lithuania. However, the investigation reported presently only concerns a constructed example with seven process streams, four hot streams and three cold streams. The primary objective of the present work was to gain an understanding of the influence of dramatic economic changes on heat exchanger network (HEN) configurations, their profitability and how an existing HEN could restrict future possibilities of heat recovery. HENs were designed to maximise the net present value (NPV) of investment and savings during a desired depreciation period for the conditions before the economic changes (State 1), after the economic changes (State 2), and for a retrofit of the “State 1” HEN under “State 2” conditions. The study required six different strategies to be considered, and the economic results, expressed as NPV of investment and savings, are presented and discussed.