Decarbonisation of the steel tube industry: Integration of a novel SHIP system to the powder-based coating process using a newly developed multiple air impingement jets tube heater

Abstract

A new Solar Heating for Industrial Processes (SHIP) system was investigated and designed to reduce greenhouse gas (GHG) emissions in the powder-based coating process for manufacturing of steel tubes. The new system includes a solar thermal rotary Fresnel collector (RFC), a phase change material (PCM) thermal energy storage system (TESS) and a novel tube heater, that utilises the heat generated by the thermal collector and stored in the PCM TESS to heat up the tubes to a temperature up to 240 oC before they are coated. The novelty of this system is rooted in the development of a novel tube heater which employs multiple air impingement jets as the main mechanism of transferring heat to the tubes without interrupting their movement. It was designed using computer-aided design (CAD) tools and modelled numerically using a computational fluid dynamics (CFD) solver. The design was optimised numerically through a parametric analysis to maximise the heat transfer to a static tube by evaluating critical parameters including the length and diameter of the tube heater, diameter of the impingement jets and distance between them. The optimised design was evaluated for its thermal performance on a moving tube using two CFD models: FLUENT Dynamic Mesh model and FLUENT – Transient Thermal model. The numerical results of the parametric analysis and the two dynamic models were experimentally validated using a test rig that evaluates the real-life thermal performance of the tube heater. The numerical and experimental findings were used in the development of a transient simulation model for the integrated SHIP system. The results of simulations have shown that a SHIP system with RFC, PCM TESS and jet impingement tube heater can lead to 9.1% and 12.2% reduction in fossil fuel use during the powder-based coating process, in low and high irradiance regions in Europe, respectively. As a result, the assessment of the environmental and economic benefits of the new SHIP system, comparing the fossil fuel energy consumption before and after implementation of the newly developed SHIP system, demonstrated significant reduction of CO2 emissions and savings, reaching 11.6 tonnes CO2 and €6,281 annually with a cumulative of 116.3 tonnes CO2 and €100,674 in 10 years, respectively. The investigations documented in this thesis highlight the capabilities of the novel SHIP and tube heater system that surpass those of conventional SHIP technologies. Recommendations for future work included investigation of the effect different jet shapes and inlet diameters, as well as more detailed environmental and economic assessments.