Waste heat recovery through traditional or Organic Rankine cycle from rice husk incineraTion: a modelling approacH for Increasing The energy efficiency Acronym: WORTH IT

Project leaders

Michela Costa, Chang-tang Chang

Agreement

TAIWAN - NSTC - National Science and Technology Council

Call

CNR-MoST (ex NSC) 2016-2017

Department

Engineering, ICT and technologies for energy and transportation

Thematic area

Engineering, ICT and technologies for energy and transportation

Status of the project

New

Research proposal

The research project focuses on the exploitation of biomass or waste material in co-generation waste-to-energy plants. It is a synergic numerical and experimental approach devoted to the optimal design for the highest efficiency and the lowest environmental impact. Various configurations will be considered, with a different share of the electrical and thermal energy user's needs. The main characteristics of the analysed systems are the employment of renewable energy sources and the presence of a Rankine cycle or an Organic Rankine Cycle (ORC). The ORC solution will be analysed in the case the generated heat serves to local scopes and the temperature level of exhaust gases is low.
Technology for thermo-chemical conversion of biomass is one of the key elements to make the vision of an energy system without fossil fuels a reality. Use of biomass offers a combination of flexibility, efficiency and environmental acceptability that is essential to meet future energy requirements and earth protection needs. Biomass availability and sustainable utilization may be surely arguments of discussion, that would entail local characteristics of territory and habits, economy aspects and constraints, but surely exploitation for energy purposes is an interesting option in those countries, as Taiwan, where food crops, principally rice, offer a great availability of residuals of high organic content.
Interest in biomass incineration is due to the envisaged inhomogeneous know-how in the field: large-scale applications are indeed a reality, but the technical and economic competitiveness of existing units has surely to be improved to be comparable with the latest generation of fossil-fuelled power plants. Over the small and micro scale the scenario is much more fragmentary, especially if combined heat and power (CHP) applications are considered. Only a few technologies for CHP generation have many operational hours in the book and are marketed as commercial plants, others are new and on a conceptual level at universities or in companies. Waste heat recovery is hardly pursued especially where thermal energy is used locally and the residual heat is at low temperature. Moreover, a strict control of the temperature and residence time of gases within the combustion chamber is a topic of great importance to avoid formation of undesired by-products. Between harmful pollutants, nitrogen oxides, particulate matter or dioxins/furans (depending on the initial biomass composition and operating conditions), may play a determining role for the technology environmental impact and acceptance by local population. Cost factors could also be determining to some extent. The WORTH IT project can give a contribution in this perspective, that is especially valuable in the light of the worldwide need of increasing the share of renewable energy. Demonstrating operational feasibility, enhancing fuel flexibility and increasing energy efficiency are indeed internationally recognized as key elements for the development and diffusion of CHP systems fuelled with biomass.
The here proposed synergic experimental and numerical approach will involve the Istituto Motori of the National Research Council (CNR-IM) of Italy and the I-Lan University of Taiwan (I-Lan-U) with their specific and well assessed expertise in the field. I-Lan-U will dedicate efforts to collect experimental data on an existing plant, define alternative plant configurations and characterise the composition of the raw material. CNR-IM will exploit its know-how in the computational analysis of reacting systems to assess proper models of the plants. The contribution of personnel of the University of Naples Parthenope, as associated to the CNR-IM, will be fundamental for the dimensioning and regulation as the user's heat and/or electricity demands are changed.
The project is fully aimed at reducing greenhouse gases (GHGs) emissions related to energy supply, since the energetic and environmental performances are improved to their maximum possible extent. The project scope is perfectly in line with the series of compulsory indications and regulations recently established over the whole earth planet to counteract the extremely harmful effect of climate change on human living and wellness. Interventions of organisations and governing boards have in fact been initiated at global and local scale after the United Nations Framework Convention on Climate Change (UNFCCC), informally known as the Earth Summit of 1992. The implementation by the European Commission of the taken commitments is today known as the "Strategy on climate change for 2020 and beyond, a commitment to achieve by 2020 the so-called 20-20-20 European objectives", namely a 20% reduction of GHGs emissions, an increase of share of renewable energy to 20 % and an increase of energy efficiency of 20%.
The WHORT IT project will surely contribute to transfer into reality the main arguments of this strategy, and in particular of the Renewable Energy Directive (RED) 2009/28/EC on the promotion of the use of renewable energy sources, as well as the Energy Efficiency Directive (EED) 2012/27/EU, according to which Member States are required to use energy more efficiently at all stages of the energy chain from its production to its final consumption.
The market for waste-to-energy systems technologies is large and growing. Biomass use is particularly suitable for decentralised power supply in rural areas or mountain zones or in the presence of large amount of waste material deriving from food processing or food crops, as rice husk in Taiwan. Biomass is to be possibly considered to also compensate irregularity of wind power plants energy supply. Moreover, it is to be thought that ash resulting from incineration can be used in cement kilns but also by exploiting more innovative utilisation concepts like the manufacture of lightweight wall board and bricks with special properties.

Research goals

Objective of the WHORTH IT project is the assessment of a comprehensive numerical model able to simulate the energy conversion process occurring in a waste-to-energy real scale system. The model will allow considering biomass of given composition, including rice husk, and the analysis of various plant configurations, namely of different heat recovery strategies, even for local processing scopes as rice drying. The ORC solution will be investigated in the case the available thermal energy is at low temperature. Economic analysis of the plant feasibility and long term profitability will also be included.
The numerical model of the whole plant will be developed at CNR-IM and will also comprise a detailed sub-model of the combustion chamber. The biomass properties will be given by the National I-Lan University in Taiwan. The various mechanisms of heat and mass transfer between the solid bed, the supplied air and the combustion products will be accounted for. The gas phase will be treated as turbulent reacting flow. Monitoring of CO, CO2, temperature and flow field will be realized. Models of formation of nitrogen oxides and carbonaceous particulate will be introduced. Validation will be done by comparing the obtained results with available reference data from a small scale combustion system available in Taiwan.
The numerical tool resulting from the project activities will highlight possible sources of combustion inefficiencies or formed pollutants increasing.

Last update: 30/04/2025