Investigation of a low-grade industrial waste heat recovery system

Nowadays, while the energy prices are continuously growing, the dispositions which try to increase the energy efficiency are getting more and more important in all industrial areas. This is especially true for the energy-intensive industrial processes. Because of this, the producing companies pay more attention every year on suggesting and supporting projects, which aim to decrease the energy consumption of their own factory. One way of increasing the energy efficiency is to use the waste energy of the installations to redeem other energy sources. In our research, we analyse the usefulness of a waste heat recovery system based on gas-nitriding furnaces. These furnaces are operating on an industrial company´s site in Gyõr, Hungary. During the investigation, our aim is to determine the economically and technologically optimal way to use this industrial waste heat. In our dissertation, we examine the different uses of the heat from the flue gas, starting with decreasing heat demand of the heating and domestic hot water (DHW) system, then decreasing the cooling of the building with an absorption chiller and finally decreasing the electric energy usage of the factory with an ORC (Organic Rankine Cycle). The data and the parameters, which are necessary to the calculations, are based on measurements on the site (temperature of the stack gas, flow volume, content, etc.) and on data, which were given by the operator and producer of the furnaces (schedule of the furnaces, technical parameters of it, etc.). The purpose of the investigation is to find, among the given constraints, the optimal way of utilizing the waste heat and to study the effects of this on the total energy-intake of the factory.