Feasibility analysis of different energy optimisation techniques for a steel plant to improve its energy efficiency in a steam distribution system

An efficient steam distribution system is essential if steam of the right quality and pressure is to be supplied, in the right quantity, to the steam using equipment in any industry. This paper describes a feasibility study of the implementation of different energy optimisation opportunities in a steam distribution system of a steel plant to evaluate their energy saving potentials and economic benefits. The main producers of superheated steam (11 barg and 300-320 °C) in the investigated steam distribution system are service boilers (medium pressure water tube boilers), superheater at Basic Oxygen Steel (BOS) plant, backpressure steam turbine, pressure reducing stations and high lift pumps at blast furnaces where steam is transported to the whole plant through a large, complex system of pipes, several take-off lines that operate at different temperature and pressures and is approximately 20 km in length. Mass and energy balance of whole steam distribution network is carried out and feasibility of recommended energy-saving opportunities i.e. isolation of redundant steam lines, re-routing steam flows, improved insulation of steam lines and installation of non-return valves are carried out on the basis of Annualised Life Cycle Cost (ALCC) analysis and payback. The results of energetic analysis of different energy saving recommendations will results in 112TJ (tera joule) of annual energy savings which equals to 56kt (kiloton) of steam and will also results in the efficient operation by isolating cold steam lines, reduce pressure and temperature loss in the steam main through improved insulation and reduced maintenance cost within end users by using better quality steam. Based on the economic analysis, it is also concluded that proposed energy saving recommendations will create annual savings worth of £0.5 million with a payback of less than 1.5 years.