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ENERGIX-Stort program energi

Enabling optimum Grate fired woody biomass and waste to energy plant operation through Computational Fluid Dynamics

Alternative title: Optimale ristfyrte biomasse- og avfallsforbrenningsanlegg via Computational Fluid Dynamics

Awarded: NOK 19.2 mill.

Biomass to energy (BtE) and waste to energy (WtE) plants in Norway need to comply with stricter emission limits and/or adjust to tighter profit margins, and EU have implemented a further reduction of emission limits from medium (scale) combustion plants. Tighter profit margins mean that poorer/cheaper fuel qualities become interesting, as well as operational optimization with respect to efficiency and capacity maximization. NOx, particulate and CO emissions are special concerns, as well as the operational challenges following particle deposition on heat transfer surfaces. The majority of the operational BtE and WtE plants in Norway are grate fired plants, and even though different grate technologies have been developed, they suffer from both variations in fuel quality and changing operating conditions, resulting in non-optimum operating conditions. The most cost-effective measure to abate the resulting operational challenges, including increased emission levels, are with primary measures. Computational Fluid Dynamics (CFD) is the ultimate design tool for BtE and WtE plant combustion and heat transfer sections, however, cost-effective sub-models need to be developed, implemented and used in an optimum way. Moreover, the CFD simulations need to be carried out for transient conditions, to study the effect of changing operating conditions, and minimize the impact of these through improved plant operation and operational guidelines. The proposed project therefore focuses on enabling optimum grate fired BtE and WtE plant operation through CFD aided design and operational guidelines. Improved models and modelling approaches, in combination with targeted experiments/measurement campaigns, are keys for future's increased sustainable BtE and WtE plants. This will have a significant impact on two of the most important renewable value chains in Norway today, the BtE and WtE value chains. In 2017 the work was mainly focused on model development, establishment of the CFD toolbox, and preparations for experimental validation of models and CFD simulations. In 2018 the work on model development and establishment of the CFD toolbox continued, including lab-scale and full-scale validation activity, in a biomass combustion plant. In the last half of 2018 special focus was on finalising the bed model for the handling of the fuel conversion on the grate and as well base case (transient and stationary). The bed model is part of the base case, and a number of experiments have been carried out in a laboratory reactor for base case validation. For validation and for input to simulations on full scale plants it has in 2018 been carried out an experimental campaign on a grate fired Statkraft bioenergy plant, and in 2019 follows a MSW combustion plant experimental campaign. NOx reduction is an important topic in GrateCFD, and several studies connected to NOx have been carried out, where one of the goals has been to arrive at a reduced kinetics mechanism that includes NOx, which can be used in CFD simulations. The mechanism is ready and was published in 2019. Simulations of full scale plants are important in GrateCFD, and three plants have been chosen and plant data and drawings have been collected to set up the simulation cases geometrically, including air addition system below the grate and the grate itself, where after the different developed models will be used in simulations the last two years of the project. Initial simulations have been carried out in 2019, as a basis for choice of further detailed simulations. In June 2019 a measurement campaign was carried out at the Vattenfall WtE plant in Uppsala. Further in 2019 focus has been on validation and completion of models and simulation tools, which in 2020 will be used for simulation of plants. Simulations using the developed CFD toolbox were in focus in 2020, representative of up to large-scale WtE grate combustion units. In parallel a simulation approach based on using stochastic reactors for both the bed and the freeboard was used. These two approaches both forms potential powerful packages for simulations of grate combustion plants. The ultimate goal is to study concept improvements using these simulation tools. The project period was extended with half a year, until June 2021. In this finalisation phase focus has been on simulations, and finalising deliverables. The PhD candidate defended his thesis in June.

Biomass to energy (BtE) and waste to energy (WtE) plants in Norway need to comply with stricter emission limits and/or adjust to tighter profit margins, and EU have implemented a further reduction of emission limits from medium (scale) combustion plants. Tighter profit margins mean that poorer/cheaper fuel qualities become interesting, as well as operational optimization with respect to efficiency and capacity maximization. NOx, particulate and CO emissions are special concerns, as well as the operational challenges following particle deposition on heat transfer surfaces. The majority of the operational BtE and WtE plants in Norway are grate fired plants, and even though different grate technologies have been developed, they suffer from both variations in fuel quality and changing operating conditions, resulting in non-optimum operating conditions. The most cost-effective measure to abate the resulting operational challenges, including increased emission levels, are with primary measures. Computational Fluid Dynamics (CFD) is the ultimate design tool for BtE and WtE plant combustion and heat transfer sections, however, cost-effective sub-models need to be developed, implemented and used in an optimum way. Moreover, the CFD simulations need to be carried out for transient conditions, to study the effect of changing operating conditions, and minimize the impact of these through improved plant operation and operational guidelines. The proposed project therefore focuses on enabling optimum grate fired BtE and WtE plant operation through CFD aided design and operational guidelines. Improved models and modelling approaches, in combination with targeted experiments/measurement campaigns, are keys for future's increased sustainable BtE and WtE plants. This will have a significant impact on two of the most important renewable value chains in Norway today, the BtE and WtE value chains.

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ENERGIX-Stort program energi