The impacts of different profiles of the grate inlet conditions on freeboard CFD in a waste wood-fired grate boiler

Zadravec, Tomas; Yin, Chungen; Kokalj, Filip; Samec, Niko; Rajh, Boštjan

doi:10.1016/j.apenergy.2020.115055

Cited by 22 publications

(4 citation statements)

References 26 publications

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“…As it has been forecasted by the International Energy Agency, by 2050, combustion of biomass may reach as high as 50% of the global heating demand [3]. The use of biomass for energy purposes involves both large-scale heat and power generation [4][5][6] and small-scale units [7][8][9]. Particularly, low-grade fuels are now considered an alternative to fossil fuels as a relatively cheap energy source [10,11].…”

Section: Introductionmentioning

confidence: 99%

Biomass Combustion in the Helically Coiled Domestic Boiler Combined with the Equilibrium/Chemical Kinetics CFD Approach

2023

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In the face of threats related to energy supply and climate change, the use of biomass is gaining importance, particularly in distributed energy systems. Combustion of biomass, including residue biomass, is considered one of the routes to increase the share of renewables in energy generation. The modeling of gaseous phase reactions remains crucial in predicting the combustion behavior of biomass and pollutant emissions. However, their simulation becomes a challenging task due to the computational cost. This paper presents a numerical analysis of the combustion process of a gas mixture released during biomass decomposition in a domestic 25 kW coil-type boiler. Three types of biogenic fuels were taken into consideration. The work aimed at examining the available tools for modeling gas burning, thus the geometry of the system was limited only to the 2D case. The thermodynamic equilibrium composition of pyrolysis gas was determined and implemented in Ansys to simulate the process. The computational results showed the potential of detailed, but reduced, combustion mechanisms of CH4/CO/H2 mixtures in predicting the main process features. The mechanism involving 85 reactions appeared to be more reliable compared to that comprising 77 reactions, particularly for volatiles with higher H2 content, whilst offering an acceptable calculation time. The burning characteristics obtained for volatiles with less CH4 and more H2 are in good agreement with the real operation conditions reported for the boiler.

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Section: Introductionmentioning

confidence: 99%

Biomass Combustion in the Helically Coiled Domestic Boiler Combined with the Equilibrium/Chemical Kinetics CFD Approach

2023

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“…Reviewing the related published literatures, most researchers conduct studies on waste incinerator by using numerical simulation method [36,37]; few literatures on the experimental research of waste incinerator are found. As yet, there is almost no literatures about the studies on the experimental research on corn stalk incinerators, especially the arches' structure and air distribution in the wind boxes of the small-scale horizontal reciprocating grate incinerators fueled with corn stalk.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on arches structural optimization of corn stalk incinerator based on a novel momentum design method

Liu

Zhu

2021

Biomass Conv. Bioref.

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In view of the lack of theoretical basis for the current design of incinerator arches, a new momentum design method for designing small-scale incinerator arches for the disposal of corn stalk is proposed in this paper. At the same time, eight different operating conditions are determined by the orthogonal experimental design method. In this study, the momentum design method is used to carry out theoretical research on the arches structural parameters and aerodynamic characteristics of a small-scale incinerator combustion chamber in eight different conditions, which is verified by cold state experiments. As a result, a novel L-shaped flame configuration of arches for the small-scale corn stalk incinerator is developed. Cold state experimental results show that stable combustion condition can be obtained by using L-shaped flame technology and the optimum ratio of air supply, along the length of grate, below the front arch and the rear arch is found to be 3:7, which are consistent with the theoretical calculation results of the momentum design method. At the same time, it is found that the maximum turbulence intensity along the length of grate can be up to 10%, and the burning exuberant zone is approximately 0.40 ~ 0.75 of the whole relative length of the grate. The optimum dimensionless structural parameters of furnace arches are H/L = 0.333 and h/L = 0.12 with the front arch angle of 45° and horizontal rear arch, where H is the height of the front arch, h is the height of the rear arch, and L is the length of the grate of the incinerator. H/L and h/L are dimensionless criterion numbers, which could be applied in designing waste incinerator with different treatment capacity. Lastly, hot state experiment verifies the effectiveness of the arch structure of the L-flame horizontal reciprocating grate incinerator. KeywordsMomentum design method • Disposal of corn stalk • Small-scale horizontal reciprocating grate incinerator • Cold and hot state experiment • L-shaped flame arches structure * Guangyu Zhu

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“…The second model approach is based on empirical correlations. Temperatures and species can be estimated using experimental databases or conversion rates. − Both of these model groups are computationally cheap and can be combined with freeboard models but are not suitable for sensitivity analysis of fuel bed characteristics . This sensitivity can only be provided by detailed models, in which usually the fuel bed and the freeboard are treated separately to limit computational costs.…”

Section: Introductionmentioning

confidence: 99%

Stochastic Reactor-Based Fuel Bed Model for Grate Furnaces

Netzer

Seidel

et al. 2020

Energy Fuels

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Biomass devolatilization and incineration in grate-fired plants are characterized by heterogeneous fuel mixtures, often incompletely mixed, dynamical processes in the fuel bed and on the particle scale, as well as heterogeneous and homogeneous chemistry. This makes modeling using detailed kinetics favorable but computationally expensive. Therefore, a computationally efficient model based on zero-dimensional stochastic reactors and reduced chemistry schemes, consisting of 83 gas-phase species and 18 species for surface reactions, is developed. Each reactor is enabled to account for the three phases: the solid phase, pore gas surrounding the solid, and the bulk gas. The stochastic reactors are connected to build a reactor network that represents the fuel bed in grate-fired furnaces. The use of stochastic reactors allows us to account for incompletely mixed fuel feeds, distributions of local temperature and local equivalence ratio within each reactor and the fuel bed. This allows us to predict the released gases and emission precursors more accurately than if a homogeneous reactor network approach was employed. The model approach is demonstrated by predicting pyrolysis conditions and two fuel beds of grate-fired plants from the literature. The developed approach can predict global operating parameters, such as the fuel bed length, species release to the freeboard, and species distributions within the fuel bed to a high degree of accuracy when compared to experiments.

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The impacts of different profiles of the grate inlet conditions on freeboard CFD in a waste wood-fired grate boiler

Cited by 22 publications

References 26 publications

Biomass Combustion in the Helically Coiled Domestic Boiler Combined with the Equilibrium/Chemical Kinetics CFD Approach

Biomass Combustion in the Helically Coiled Domestic Boiler Combined with the Equilibrium/Chemical Kinetics CFD Approach

Experimental investigation on arches structural optimization of corn stalk incinerator based on a novel momentum design method

Stochastic Reactor-Based Fuel Bed Model for Grate Furnaces

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