Mapping of combined heat and power systems in cane sugar industry

Abstract

Cogenerating systems based on steam turbines (1–20 MW t) are indispensable when the source of energy is a solid fuel such as bagasse as in a sugar industry. These systems provide a wide range of heat to power ratios from 0 to as high as 100. The energy productivity of sugar plants differ vastly because of variations in equipment efficiency, system configuration and operating steam conditions. In this paper a mapping of the entire operating range of steam based combined heat and power plants spanning pure back pressure to pure condensing environments, based on standard steam conditions in installations and efficiencies which are currently being achieved experimentally, is presented. This will enable the rational choice of combinations, which will yield the best economic advantage. As the operating steam pressure is increased (and consequently the matching superheated temperatures) the in-house steam requirement reduces drastically and simultaneously the exportable power increases. Improvements in the systems by the use of advanced designs of steam turbines and introduction of information technologies and associated supervision control and data acquisition, energy management system, multi-media interaction, etc., is also briefly highlighted. The maximum exportable electrical power from a sugar mill after meeting the internal requirement is around 146 kW h/t of cane. The maximum exportable of steam (no power export) is around 0.65 t/t of cane.