The efficient utilization of waste heat from industrial processes can provide a significant source of energy savings for production plants, as well as be a driver of sustainable operations and the abatement of emissions. Industrial waste heat usually is contained in liquid or gaseous outlet streams. Although the possible ways to utilize waste heat are discussed in a wide variety of papers, these either provide only a general overview of utilization options and opportunities or focus on a narrow range of industrial processes. The aim of the present paper is to discuss the practical aspects of waste heat utilization in the European Union so that the reader can gain perspective on (i) the thermal classification of waste heat, (ii) liquid and gaseous waste streams and their typical temperatures for industrial use cases, (iii) the technical, economic, physical, and environmental aspects barring full utilization of the available waste heat, (iv) waste heat sources in various industries, and (v) standardized equipment and technologies applicable to industrial waste heat utilization, including their advantages, disadvantages, and weak points.

The efficient use of waste heat (WH) from gas streams is one of the key aspects in reducing the energy intensity, operating costs, and environmental impact of production processes and in the transition to sustainable energy. However, in many practical cases, the use of WH remained challenging due to the specific limiting conditions of the stream and critical issues such as fouling and the corresponding low heat transfer efficiencies. In particular, particle fouling hinders the operation of heat transfer equipment (HTE) and introduces several design considerations. To tackle this issue at the design stage, this study proposed a systematic framework intended for the design of fouling-resistant HTE. For a given usable stream, the major elements of the HTE design framework include (i) the Environmental assessment that enables the user to select the optimal way of WH utilization; (ii) a mobile testing device (MTD) for fouling parameters measurement, and (iii) an improved mathematical model for determining the critical fouling rate for the design of THE suited to particle-laden streams. The framework, especially the mobile testing device and the mathematical model, is tested under laboratory and/or industrial conditions, and illustrated with a case study of the WH stream with cement powder. Results show that the environmental assessment module can guide the selection of optimal usage with minimum environmental impact, and the mobile testing device and the mathematical model are able to determine the critical fouling velocity to support HTE design with higher resistance to fouling and higher operational reliability.