Recent progress on the utilization of waste heat for desalination: A review

Application of nanofluids for enhanced waste heat recovery: A review

Opportunities and strategies for multigrade waste heat utilization in various industries: A recent review

This paper presents a review of hydrogen production systems using geothermal energy, showing the importance and potential of this technology in addition to the main obstacles facing this domain. The effect of several parameters was taken into consideration, such as geothermal fluid temperature, water electrolysis temperature, working fluid, and type of power cycle. The different types of geothermal power plants were also compared, namely, flash, binary, flash-binary, recuperative, regenerative, and organic Rankine flash cycles. This study covers a wide range of investigations regarding hydrogen production rate, hydrogen production cost, energetic efficiency, exergetic efficiency, exergetic cost, and electricity generated. Hydrogen production rate is one of the most important mentioned parameters in which it was found to vary from 5.439 kg/h to 13958 kg/h. Multigeneration systems have shown great potential to enhance the overall system’s efficiency, leading to reduced production costs. The integration of another energy source was found to be interesting in geothermal-driven hydrogen production systems. This would promote the adoption of multigeneration system as well as increasing the geothermal fluid’s temperature before entering the power cycle.

A review of geothermal energy-driven hydrogen production systems

Cement is the world’s most widely used construction material. In 2019, global production amounted to 4086 MT, of which Colombia contributed 12.59 MT. The main component of cement is Clinker and it appears as an intermediate product in the manufacturing process that is produced in a kiln system at sintering temperatures. Such a process exhibits high environmental impacts due to both elevated emissions of Carbon Dioxide and fuel consumption and it is inherently prone to thermal inefficiencies, as heat losses to the surroundings, because of the large flow rates and high temperatures. In this work, the waste heat obtained from the cooling of a high-temperature gas effluent from the rotary kiln in a Colombian cement plant is analysed for its potential use either to dry wet raw material (limestone) or to generate electricity through an ORC. Material, energy and exergy balances for the steady-state were assisted with simulations in Aspen Plus V.10 software. Exergo-economics analysis followed the traditional approach using the net present value (NPV) of the investment as decision criteria. To achieve a holistic view of the waste heat recovery scenario a sensitivity analysis is carried out varying the outlet temperatures of the hot gases for various working fluids in the ORC. Results showed that the best alternative, NPV = 0.37 MUSD at market conditions of electricity and fuel sale price, delivers a maximum of 3.77 MW of electricity with a thermal efficiency of 15.96% and an exergy efficiency of 37.52% using Cyclo-Pentane as working fluid. None of the dryer units attained a positive NPV and were discarded. However, the highest moisture reduction in the solids stream was 5.67% at T = 120 ∘C. The option of placing a drying unit immediately after an ORC to completely cool down the gases was economically analysed for ORC cases with best NPV, T= 150 ∘C and T = 180 ∘C. But no substantial improvement was found over using the ORC alone. The possibility to improve the simple ORC performance is explored through the inclusion of an internal heat exchanger, such recuperated cycle outperforms its simpler configuration in terms of thermal and economic performance delivering 4.1 MW of net work with an NPV = 0.42 MUSD, a rate of return of 15.58% and a payback time of PB = 6.07 years. This is 8.75% more work with 13.51% better economic performance than the simple ORC.

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Evaluation of waste heat recovery technologies for the cement industry

In the framework of the ETEKINA project, waste energy streams have been analysed at an aluminium automotive parts production facility in Spain, at a steel foundry in Slovenia and at a ceramic tile production unit in Italy. The aim is to recover more than 40% of the waste heat contained in the exhaust streams and reuse it within the industrial plant rather than emitting it to the atmosphere. To select the applications where the profitability of heat recovery can be demonstrated, the flow rates and temperatures of the applicable exhaust streams have been measured and analysed to select the processes for waste heat recovery and it's re-used in the three industrial plants. The demonstration of the cost-effective waste heat recovery is to be made by using heat pipe heat exchangers (HPHEs) and the processes whereby the heat recovery installations will be erected have already been selected. HPHEs were selected as a heat recovery technology due to their advantages and key features over convectional heat exchangers considering space restrictions, pressure drop limitations, and other waste stream challenges. The challenges include high temperature of the waste and the heat sink streams, fluctuations in the waste stream flow rate and temperature, presence of corrosive moisture such as sulphuric acid in the waste stream, and the presence of particles in the waste stream which can cause fouling leading to failure of convectional technologies. Furthermore, HPHEs are maintenance-free and can have payback period of less than three years.

/pdf/etekina-analysis-of-the-potential-for-waste-heat-recovery-in-40e03gyagr.pdf

ETEKINA: Analysis of the potential for waste heat recovery in three sectors: aluminium low pressure die casting, steel sector and ceramic tiles manufacturing sector

Josu Zuazua

Papers

ETEKINA: Analysis of the potential for waste heat recovery in three sectors: aluminium low pressure die casting, steel sector and ceramic tiles manufacturing sector

Waste heat recovery solution based on a heat pipe heat exchanger for the aluminium die casting industry