Biomass Boiler Research Articles

Communal or individual – Exploring cost-efficient heating of new city-level housing in a systems perspective

As cities expand, new buildings are constructed and they require heating. With increasing integration of the heating and electricity sectors and forecasts of rapid growth in electricity demand, heating choices become critical for the sustainability transition. The main heating options are communal or individual, where the communal option is represented by district heating (DH) and the individual option mainly by heat pumps or biomass heating. Which option is best from the cost perspective depends on the building type and on the energy system development. Thus, this paper investigates cost-efficient heating of new city-level housing in a systems perspective under various scenarios.The investigation was carried out using an energy systems optimization model based on a case representing Swedish conditions. A dynamic approach was used to investigate cost-efficient development of the supply side and demand side simultaneously.The results indicate that the most cost-efficient heating systems are: DH for apartment buildings; and individual heating options for single-family housing with low heat demands. For large single-family housing with high heat demands, the cost-efficient solution depends on the heat demand profile. Higher heat use during winter favors DH and individual biomass boilers, but diminishes the economic feasibility of individual heat pumps.

Optimization of district heating system considering carbon taxes and subsidies based on energy policy stage goals

Climate change is one of the main issues that humanity will face in the upcoming decades. Low-carbon district heating is an important alternative for decarbonizing the heating sector against unsustainable higher carbon emission heating methods. Most available studies have concentrated on fixed or predetermined policies instead of attempting a numerical optimization of carbon taxes and subsidies in district heating. This study proposes the optimization of a district heating system in Northeast China considering carbon taxes and subsidies based on energy policy stage goals. Research shows that carbon taxes and subsidies have a certain impact on the change in district heating sources. With the increase in carbon taxes, heating from non-fossil energy sources is increasing, an area that can also be promoted with subsidies for non-fossil energy. Considering the total cost of heating enterprises, it is appropriate to set the carbon tax for district heating at $86. Similarly, considering government expenditure, it is suggested that construction subsidies be set at 10.5$/m2, 3.5$/m2, and36.5 $/m2 for air source heat pumps, biomass boilers, and ground source heat pumps. In addition, the obtained results can be used as guidelines for the heating industry to design more efficient district heating and focus research and development efforts on the most promising non-fossil energy heating technologies.

Heat Transfer Analysis Using Thermofluid Network Models for Industrial Biomass and Utility Scale Coal-Fired Boilers

Integrated whole-boiler process models are useful in the design of biomass and coal-fired boilers, and they can also be used to analyse different scenarios such as low load operation and alternate fuel firing. Whereas CFD models are typically applied to analyse the detail heat transfer phenomena in furnaces, analysis of the integrated whole-boiler performance requires one-dimensional thermofluid network models. These incorporate zero-dimensional furnace models combined with the solution of the fundamental mass, energy, and momentum balance equations for the different heat exchangers and fluid streams. This approach is not new, and there is a large amount of information available in textbooks and technical papers. However, the information is fragmented and incomplete and therefore difficult to follow and apply. The aim of this review paper is therefore to: (i) provide a review of recent literature to show how the different approaches to boiler modelling have been applied; (ii) to provide a review and clear description of the thermofluid network modelling methodology, including the simplifying assumptions and its implications; and (iii) to demonstrate the methodology by applying it to two case study boilers with different geometries, firing systems and fuels at various loads, and comparing the results to site measurements, which highlight important aspects of the methodology. The model results compare well with values obtained from site measurements and detail CFD models for full load and part load operation. The results show the importance of utilising the high particle load model for the effective emissivity and absorptivity of the flue gas and particle suspension rather than the standard model, especially in the case of a high ash fuel. It also shows that the projected method provides better results than the direct method for the furnace water wall heat transfer.

Research on the application of air source heat pump and biomass boiler combined heating systems in northern new rural communities.

In today’s society, the country is vigorously promoting clean energy heating to replace coal heating with high carbon emissions. In recent years, with the rapid development of new rural communities and abundant biomass resources in rural areas, biomass boiler heating can save energy and reduce energy consumption. However, the heating efficiency of a single biomass boiler is low. The air source heat pump and biomass boiler are combined to form a combined heating system, which has higher heating efficiency and better energy-saving effect compared with separate air source heat pump heating equipment and separate biomass boiler system. In addition, air source heat pumps and biomass boilers are both clean heating methods, which can better promote the clean heating of new rural communities in China.

Simulation and Experimental Study on the Low NOx Combustion of 35 Kw Biomass Boiler with Air Staging

In the present research, numerical simulations and combustion experiments were carried out using a 35 kW biomass low nitrogen combustion furnace. For this purpose, the boiler structure and fluid area in the furnace were modeled. Subsequently, the grid was divided and the parameters such as speed and pressure were set using Gambit. Then, the model was introduced into Fluent in order to simulate the combustion process and for flow field output and analysis. By analyzing the distribution and changes in temperature field, velocity field, and NOx concentration field under different air supply schemes, and performing low nitrogen combustion experiments, the influence of different air supply schemes on fuel combustion and NOx emission was determined. Through the mutual verification of simulation and experimental research, the optimal air distribution scheme was obtained. The results showed that: without the air staged combustion, combustible gas and air were not properly mixed. As a result, the loss of mechanical incomplete combustion occurred. Under air-staged combustion, the addition of the secondary air reduced the “chimney flow” phenomenon in the furnace to a certain extent. The combustible gas and air were mixed more adequately and the reaction rate and efficiency significantly increased. In addition, with the introduction of the secondary air, the air and the flue gas in the furnace were more efficiently mixed. Moreover, the temperature in the upper combustion area of the furnace decreased by 300–500 K, which slowed down the rate of nitrogen oxides production. This effect was intensified when the proportion of the secondary air increased. The status of the combustion process and changes in the concentration of NOx in the flue gas were compared and analyzed under various working conditions. Data indicated that the optimal air distribution scheme was that with 70% of the primary air and 30% of the secondary air. In this case, the NOx emissions were 27% lower than those without the air staged combustion.

Optimized Operation and Sizing of Solar District Heating Networks with Small Daily Storage

To continue improving the integration of solar thermal in district heating networks, optimization tools that can study both sizing and operation of heating plants are needed. In this article, the ISORC tool was used to study the sizing and coupled operation of smaller storage and solar fields with other heating sources such as biomass and gas boilers. For this, a k-medoids algorithm was applied to select consecutive characteristic days to size the system based on an optimal operation of consecutive days in the same season. The formulated problem was nonlinear, and the objective function to be minimized was the total cost. Two case studies with different day constructions and distributions were studied with various sensitivity analysis. The formulation and methodology allowed us to study different cases and situations easily and proved the importance of the selection and attribution of typical days. In all cases, the results showed that even with a daily approach, solar thermal covers approximately 20% of the demand, which demonstrates the relevance of considering and developing small daily storage with small solar fields.

Atikokan Digital Twin, Part B: Bayesian decision theory for process optimization in a biomass energy system

We describe the integration of Bayesian decision theory in a digital twin framework to provide a process optimization tool for a biomass boiler. Our application is the Atikokan Generating Station, a 200 MW, biomass-fired tower boiler operated by Ontario Power Generation in Ontario, Canada. For this analysis, we use all available prior information as well as data from the biomass plant and from science-based models. Our objective is to determine a single-valued operational setpoint for the boiler that satisfies a set of objectives/constraints while accounting for uncertainty in boiler operations and in boiler measurements. This setpoint is then continuously updated at the frequency required by plant operations to provide dynamic control. This process of decision-making under uncertainty is a form of artificial intelligence and provides a formal methodology for making optimized decisions in complex systems. Our methodology consists of defining the decision space where all possible solutions reside, identifying the probability of outcomes given that a specific decision was made, creating a decision/cost model that relates the quantities of interest (QOIs) in the physical system (e.g. gross power output) to the decision QOIs (e.g. dollars), identifying the utility (the value to the user) of each outcome, and maximizing the expected utility (i.e. the decision). Once the decision (operational setpoint) is computed, we can predict all of the QOIs (boiler efficiency, O2 concentration at the outlet, etc.) at the decision point from the science-based model using the parameter distributions computed as part of the Atikokan Digital Twin.

Thermoeconomic Optimization of a Polygeneration System Based on a Solar-Assisted Desiccant Cooling

This paper presents a thermoeconomic analysis of a polygeneration system based on solar-assisted desiccant cooling. The overall plant layout supplies electricity, space heating and cooling, domestic hot water, and freshwater for a residential building. The system combines photovoltaic/thermal collectors, photovoltaic panels, and a biomass boiler coupled with reverse osmosis and desiccant air conditioning. The plant was modeled in TRNSYS and simulated for 1 year. A parametric study defined the system’s setup. A thermoeconomic optimization determined the set of parameters that minimize the simple payback period. The optimal structure showed a total energy efficiency of 0.49 for the solar collectors and 0.16 for the solar panels. The coefficient of performance of the desiccant air conditioning was 0.37. Finally, a sensitivity analysis analyzed the influence of purchase electricity and natural gas costs and the electricity sell-back price on the system. The optimum simple payback was 20.68 years; however, the increase in the energy cost can reduce it by up to 85%.

Experimental study on inert products, moisture, and particle size effect on the minimum ignition energy of combustible dusts

Handling combustible dusts not only continues to pose a risk to industry but can also affect the safety of society. Explosion risk could be avoided or mitigated trying to guarantee inherent safety throughout the product life chain. One way to reduce the risks when dealing with combustible dust is to increase the Minimum Ignition Energy (MIE) in order to decrease combustible dust ignition sensitivity. To achieve this decrease, the inertization technique, also known as moderation, will be used. It consists of adding inert powders or humidity to the combustible dust. As sometimes end-users also must deal with the handling of flammable dusts, this study aims to find the most optimal inert for toner waste from printers and Holi powder (organic coloured dust from Indian parties), taking Lycopodium as a reference. Calcium carbonate, sodium bicarbonate and gypsum are proposed as inert materials. In addition, with the aim of giving a second use to biomass boiler waste or boiler slagging, this waste will be analyzed as inert, as well as how humidity affects the combustible dusts. Then, sodium bicarbonate will be tested at different granulometries to evaluate the effect of particle size on moderation process. The tests were carried out in the modified Hartmann apparatus or MIKE 3.0. Mechanisms such as decomposition of inert dust have been analyzed by thermogravimetric analysis (TGA)). The results show that gypsum and moisture are the best performing inert followed by calcium carbonate. Boiler slagging and solid bicarbonate contribute to a decrease in the MIE in some of the tests. The reasons for this deviation are discussed in the presented article. When sodium bicarbonate is analyzed at different particle sizes, it is found that the optimum particle size does not match the particle size of the combustible dust. According to the tests, there is an optimum point for which the inert powder provides better results.

Gaseous and particulate matter emissions from the combustion of biomass-based insulation materials at end-of-life in a small-scale biomass heating boiler

To alleviate the unbearable pressure on forests in Europe, the use of lower quality woody materials or wastes and agricultural fuels is emerging for the production of heat. The two major challenges of using these types of fuels are associated with the chemical composition variability and some fuel characteristics that could trigger potential issues throughout the burning process. This study aimed to investigate the environmental and technical performance of a small-scale multi-fuel biomass heating boiler (20 kW) fired with DINplus certified wood pellets and two granulated biomass-based insulation materials, namely hemp fibers and wood fibers under standard laboratory conditions. The boiler efficiency, particulate matter, and gaseous emissions were evaluated and compared to the legally permissible values specified in EN 303–5:2021. Hemp fiber pellets fulfilled the requirements for residential pellets, while wood fiber pellets showed lower durability and higher nitrogen and sulfur contents than the European standard limits. To respect the emissions regulation, blending wood fibers with certified wood is therefore necessary. Pellets type was noticed to significantly affect the gaseous and dust emissions but marginally the boiler efficiency. This latter was near 80 % for all fuels owing to high sensible and latent heat losses. Hemp fiber pellets showed high CO and dust emissions attributed to their high bulk density and high ash content, respectively, while the wood fiber pellets showed high NOx and SOx emissions accredited to their elemental composition. Gaseous and dust emissions were reduced through the blending of hemp and wood fibers with certified wood pellets. The particulate mass concentrations of the tested pellets fluctuated between 38 and 360 mg.Nm−3. Particulates were mainly composed of potassium, chlorine, sulfur, silicate, calcium, and zinc. From a number perspective, particles with diameters below 1 µm were dominant and their concentration varied between 104 and 106 particles.cm−3. Pelletized biomass-based insulation materials mixed with certified wood could be considered an attractive alternative fuel for residential biomass boilers.

ANALYSIS OF DIRECTIONS TO INCREASE THE ENERGY EFFICIENCY OF OFFICE BUILDINGS IN UKRAINE TO THE NZEB LEVEL

The article is an analysis of the feasibility of replacing the energy source with heating an office building in Kyiv to the level of a building using energy produced by renewable sources (biomass). The authors assessed the potential of biomass in Ukraine, the logistics routes to ensure uninterrupted supply and the cost of renewable resources. Estimation of necessary investments of transition from energy source to heating, running on natural gas, to energy source, running on biomass (sunflower husk), is given by changing the integral cost of heating costs for three options for thermal protection of the building: non-insulated (existing) building; building, the level of thermal protection of which meets the requirements of Ukraine; a building whose thermal protection level satisfies the requirements of Sweden. In particular, the authors determined that the integral cost of heating when using a boiler on pellets from sunflower husks without improving the thermal insulation of the enclosing structures of the building is significantly lower than when using natural gas as an energy carrier for the production of thermal energy, and the initial cost of an insulated building meets the requirements of Ukraine and the requirements of Sweden when using a natural gas boiler is significantly higher than an uninsulated building with a biomass boiler. The results obtained indicate that there are prospects for scaling buildings with almost zero energy consumption in Ukraine, given the development potential of biomass and the significantly lower unit cost of biomass energy compared to natural gas.

Experimental and CFD analysis of wire coil turbulators in biomass boilers

To achieve as complete fuel burnout with as little excess air as possible, small wood log boilers (< 50 kW) use stage combustion. The first stage is often a process similar to downdraft gasification that consequently produces a flue gas laden with particulates. To prevent the build-up of solids and promote heat transfer in pipes of the convective part of these boilers, wire coils are used. The paper presents their in-situ examination together with CFD analysis. The analysis is carried out in a 460 mm long pipe, with a diameter of 82.5 mm, equipped with different wire coils for flue gas temperatures in the range between 300?C and 150?C. The analyzed coils are with and without a conical spring at their free end. The addition of this conical top is economical and should influence the rotation of the core flow. Proper pipe surface cleaning limited the analyzed wire coil designs to the dimensionless pitch, p/d, in the range between 0.36-0.61, dimensionless wire diameter e/d = 0.04-0.1, and pitch to wire diameter ratios p/e = 3.75-14.3, and three different angles (60?, 90?, and 120?) of the conical top. The goals are to find the optimal flue gas velocity for the given operating conditions, pipe, and wire coil dimensions, and to investigate the addition of the conical top on heat transfer enhancement. Several evaluation criteria are used to achieve the goals.

Experimental studies of wood chips charactristics influence on boiler performance and pollutant emissions

Wood chips are often used as solid fuel in modern biomass boilers. Experiments were conducted on 22 boilers located in Serbia burning wood chips as fuel. The influence of wood chips characteristics is analyzed in relation to the flue gas losses and the thermal efficiency of the boiler. Measured useful heat output of the tested boilers was 460-2585 kW. Moisture content of the wood chips was 19.21-38.23% with a net calorific value of 10177-14139 kJ/kg and ash content of 0.84-3.59%. Thermal efficiency of the boilers was 88.78-94.06%, flue gas losses 5.84-11.13% and flue gas temperature 121.83-188.44?C. Experimental research and analysis of the results showed that an increase in moisture content of wood chips lead to a decrease of net calorific value i.e., decrease in flue gas temperature. Moisture content of wood chips has an influence on both useful heat output and boiler thermal efficiency. The experimental results showed that for a given boiler construction, this impact is not negative. Based on regression analysis, mathematical expressions were derived for the calculation of thermal efficiency and flue gas losses. Throughout the experiments, pollutant emissions were measured, NOx, CO, and particulate matter.

A New Approach to Water Treatment: Investigating the Performance of Compact Particulate Matter Collector for Use in Compact Flue Gas Condenser

Abstract The concept of the new water treatment system was developed. A primary area was defined in which such technology is intended to be used: water treatment in compact flue-gas condensation systems for a low-power wood-fuelled biomass boiler. A prototype operating based on invented technology was built. An experimental plan was developed, and an experimental stand was constructed to determine the prototype’s efficiency. Based on the study’s results, it was concluded that the prototype could operate effectively in the laboratory environment: achievable efficiency is equal on average between 57.84 % and 88.09 % depending on the operating mode. The result is assessed as positive. TRL 3 has been reached.

Start up Experience of a Biomass boiler

Start up Experience of a Biomass boiler

On the design of renewable-based utility plants using time series clustering

This work addresses the design of utility plants incorporating technologies to process biomass, manure, solar radiation, and wind to generate steam and electricity. To capture the hourly and interannual variability of solar and wind resources, an optimization framework is proposed. The framework involves clustering methods to capture the variability of solar and wind resources and a multiperiod design optimization problem minimizing operating and investment costs. Results show that the number of representative days impacts both the minimum cost and the plant topology. To study this impact, a methodology using multiple samples of representative days and two approaches to select design solutions are proposed and discussed through extensive computational results. Overall, two plant topologies were identified, one integrating syngas and the other a biomass boiler. The biomass-based plant showed 1% lower investment and 10% lower operating costs but requires additional make-up power from an external grid.

Integration of a heating and cooling system driven by solar thermal energy and biomass for a greenhouse in Mediterranean climates

World population growth, climate change, and water scarcity will increase food vulnerability, especially in developed countries. Therefore, increasing crop productivity is one of the main challenges to be addressed in the next years. In this sense, intensive horticulture will play a key role to supply the growing demand for food. In greenhouse farming in Mediterranean climates the passive control of the greenhouse ambient conditions is insufficient and, therefore, the use of active heating/cooling systems is required.The status of solar thermal, biomass, and absorption heat pump technologies makes the active management of greenhouse climate conditions technically feasible. At the same time, the utilization of solar thermal and biomass energies allows reducing, as much as possible, the consumption of natural resources and the generation of waste.In this study, we present a system based on solar thermal energy, biomass, and an air-cooled absorption chiller that are integrated to control the temperature of a greenhouse for tomato production in Mediterranean climates. The greenhouse thermal demand is firstly modelled with the TRNBuild tool and validated with real data obtained from a monitored greenhouse in southern Spain. The validated model is used to both study the system operation and determines the annual heating and cooling demands of a greenhouse with tomato crop (26.31 kW·h·m−2, and 61.97 kW·h·m−2, respectively), the energy performance of the system (solar fraction 54.92 %, and absorption chiller seasonal COP 0.624), and the annual biomass operational cost (2.70 €·m−2). This study also provides the specification of the main components (absorption chiller capacity, solar collector technology, absorbance area, biomass boiler thermal capacity, and water tank volume…) that can achieve these results. Moreover, the control for different typical days is shown.

Comparison of the Flue Gas Emission Values of a Traditional Designed Biomass Boiler with the Specified Emission Standards

Reducing emissions of various air pollutants is needed to achieve cleaner and healthier air quality in all EU countries. The National Air Pollution Reduction Programme sets out pollution reduction targets of 55% for particulate matter (PM), 73% for sulphur dioxide, 58% for non-methane volatile organic compounds and 66 % for nitrogen oxides, among other air pollutants, by 2030 compared to the 2005 reference year. The household sector is one of the areas most responsible for the emission of the main air pollutants linked to human activity. Within this, household solid biomass combustion is particularly important as a widely used heating method in Hungary. In this paper, we show how traditional boilers pollute the environment by measuring the results of a given boiler. Furthermore, the study describes how the specific boiler's air pollutant emissions and energy performance occurred. Finally, the research found that traditional boilers cannot meet strict emission standards, so their replacement and further development may be justified.

The Effect of Mixing Recirculated Flue Gas with Primary or Secondary Air during Biomass Combustion in Grate-Firing Boiler as the Primary Measure for NOx Reduction

Due to the pollutant regulations of the Directive (EU) 2015/2193, the need to reduce the emissions of pollutant compounds such as NOx is of a great importance for industrial boilers. This study was performed to determine the effect of primary measures in reducing said pollutants by mixing primary or secondary air with FGR and supplying the mixture for combustion. The studies were conducted on low-scale industrial biomass grate-firing furnace and boiler stand of 25 kW. Sunflower husk pellets, shredded pine bark and wood pellets were combusted during these experiments and emissions of NOx in their combustion products were analyzed. The most significant reduction of emissions was achieved by mixing primary air and FGR and supplying it to the primary combustion zone – under the grate. The emissions of NOx were reduced by 29% and 15% for shredded pine bark and sunflower husk pellets respectively. The emissions of shredded pine bark were reduced enough to meet the standards of the EU Directive, unlike those of sunflower husk pellets. The possible ways to reach greater reduction of NOx by using primary measures are implementing staged combustion, supplying pure FGR and/or mixing agriculture waste with fuels containing less N in its composition.

Analysis of the pollution emission system of large-scale combustion of biomass briquette fuel in China

In order to realize the sustainable development strategy and reduce the air pollution caused by biomass boiler emissions, the current study added a Selective Catalyst Reduction (SCR) external denitration system and a wet electrostatic precipitator to the original “three-stage” dust removal system for biomass briquetting fuel boiler emissions and completed the upgrading of the “five-stage” dust removal system. Taking the soot concentration, Sulfur dioxide (SO2) concentration, and Nitrogen oxides (NOX) concentration in the flue gas as the evaluation indicators, real-time online monitoring of the operating conditions of the system is carried out. The results show that the average concentration of smoke and dust in the flue gas discharged from the “five-stage” dust removal system is 3.47 mg/m3, with 2.49 mg/m3 for the average concentration of SO2, and 25.48 mg/m3 for the average concentration of NOX. The removal rates of soot, SO2, and NOX have increased by 5.8%, 4%, and 48.5%, respectively, which are much lower than the emission standards of biomass boiler flue gas pollutants. The innovation of this system is unprecedented for the large-scale combustion of biomass briquettes in China, which greatly reduces the emission of harmful gases. This upgrading will not only make a certain contribution to environmental protection but also provide a theoretical basis to the biomass briquette fuel industry.