Wood Furnaces Research Articles

The modeling and simulation of a smoke-free firewood furnace designed for indirect heating adapted to mixing heating configuration

The use of wood furnaces for thermal energy applications in drying is common among coffee growers in Brazil. However, incomplete combustion of firewood and excessive use of damaged furnaces can lead to product contamination and negative environmental effects. To address this issue, a smoke-free wood furnace was designed, to heat the drying air utilizing a heat exchanger, and using a removable smoke-free combustion cell. The new furnace design was based on thermal energy ranging from 15 to 30 kW, drying airflow rates from 35 to 45 m³ min-1, and drying air temperatures from 50 to 80 °C. The design process considered the thermal energy required for heating air, furnace fuel consumption, combustion chamber volume, grate area, and heat exchanger dimensions. The performance of the adapted furnace data was monitored over time using a graphics statistical control (x-bar chart). Regression analysis of temperature and mass flow rate for the mixed heating configurations was carried out to develop quadratic models for the modified operation. The models were used to create a simulation model using ExtendTM simulation language to predict the performance of the furnace, in mixed heating at the desired drying air temperature. The simulation was carried out under two different conditions, normal and controlled operation of the furnace. Five scenarios of working hours without refueling (119 min) drying temperature were carried out. The simulation result indicates that the furnace operates at a maximum efficiency of approximately 40% irrespective of the desired drying temperature during normal operation. However, controlled operation with increased opening time of the mixing air inlet for admitting ambient air into the mixing chamber significantly improved the furnace's efficiency, with an optimum efficiency of 55% achieved at 90°C drying temperature. The simulation reflects that the furnace operates at a maximum efficiency of 68% at a temperature of 90°C, which can be attained at 66.31 minutes of operation in mixed heating of 30 minutes and indirect heating configuration of 89 min during working hours without refueling of 119 min.

Dynamic Real-Time Measurements and a Comparison of Gas and Wood Furnaces in a Dual-Fuel Heating System in Order to Evaluate the Occupants’ Safety and Indoor Air Quality

Due to rising energy costs, there is a trend to return to conventional heating systems powered by solid fuel. A rise in the combination of new and old energy sources is creating unintended dual-fuel heating systems. These systems combine an old solid-fuel furnace and a new gas furnace. Usually, the old furnace was meant to be replaced by the new one and their cooperation was never intended when installing the new heating system. The occupants decided to leave the old system in fear of a rise in prices of gas or electricity or temporary problems with their supply. The study focuses on such a system and its influence on indoor air quality and thermal comfort. A series of dynamic measurements with an IoT remote sensor array in a chosen household was conducted to evaluate the behaviour of the system as well as effects on the indoor environment. Sensors measured the CO2 concentration and thermal profile in a household when using a dual-fuel heating system consisting of an old wood furnace from the 1980s and a recently installed new gas furnace. The results showed that none of the heat sources posed a threat to the occupants. Contaminants were safely removed by the exhaust systems of the furnaces. The thermal comfort, however, was influenced more by the wood furnace where fluctuations in the temperature were noticed, especially during the night. The gas furnace maintained a stable temperature that was more suitable for the occupants.

Investigation of real-life operating patterns of wood-burning appliances using stack temperature data

ABSTRACTA study was undertaken to identify patterns of consumer use of outdoor wood boilers or outdoor wood furnaces (technically referred to as outdoor wood-fired hydronic heaters (OWHHs)) and indoor wood stoves (IWSs) to inform the development of performance testing protocols that reflect real-life operating conditions. These devices are manually fed, and their usage protocols are a function of a number of variables, including user habits, household characteristics, and environmental factors. In this study, researchers logged the stack wall temperatures of 4 OWHH and 20 IWS units in the states of New York and Washington over two heating seasons. Stack wall temperature is an indicator of changes in combustion modes. Two algorithms were developed to identify usage modes and cold and warm start refueling events from the stack wall temperature time series. A linear correlation analysis was conducted to evaluate the effect of heat demand on usage patterns. The results and methods presented here will inform the cataloging of typical operational patterns of OWHHs and IWSs as a step in the development of performance testing procedures that represent actual in-home usage patterns.Implications: Current US regulatory programs for residential wood heating use a certification program to assess emissions and efficiency performance. Testing under this program uses a test that burns 100% of a single, standardized wood fuel charge to assess performance at different steady-state load conditions. This study assessed in-field operational patterns to determine if the current certification approach accurately characterized typical homeowner use patterns. The data from this study can be used to inform revisions to testing methods to increase certification test comparability between lab and field performance.

Traditional brick productions in Madagascar: From raw material processing to firing technology

Bricks are the most common building materials of Madagascar due to the large availability of clayey raw material, the simple technology of production and the ease of use. The brick production is mainly organised in local workshops close to supplying site of clayey deposit where sediments are extracted, moulded in bricks, dried and then fired in open-air furnaces. Fuel varies from peat soils to wood depending on the local availability. Correspondingly, firing time varies from few days in wood furnaces to some weeks in peat fired furnaces. Samples of bricks and raw materials as well as peat fuel, from four workshops located in central and southwestern Madagascar were collected and analysed to infer the technological skills of the Malagasy traditional brick manufacture. Central Highlands Madagascar workshops use clayey lateritic soils formed from in situ weathering of basement rocks. The main plastic component of these deposits is kaolinite. Also the clayey sediments from southwestern Madagascar have kaolinite along with low-ordered clay minerals and carbonates such as calcite and minor Sr-rich dolomite.As far as fired bricks are concerned, experimental data evidenced quite low firing temperatures (below 600°C) in the two different furnaces, regardless the type of fuel. As far as peat fuel is concerned, its low calorific value along with a large amount of furnace energy dispersion does not allow to achieve the temperatures required to produce good quality bricks, notwithstanding long firing time (some weeks). On the other hand, firewood powdered furnaces, although providing much higher energy and a consequent much shorter firing process (few days), also suffer of diffuse heat dispersions which concur to the bad quality of the final product.The specific energy input calculated for type 1 furnace (peat fuel) ranges between 0.09MJ/kg and 0.18MJ/kg of clayey material thus confirming a rather inadequate firing process for the production of good quality bricks, and a rough estimate indicates that volume ratios between peat and clayey material as low as 1:1 should be used in order to reach “modern” specific energy inputs.

Outdoor wood furnaces create significant indoor particulate pollution in neighboring homes

Context: The use of outdoor wood furnaces (OWFs) is common in many parts of the United States. Little published information exists on the concentrations of outdoor and indoor fine particulates found near OWFs.Objective: To compare PM2.5 (cts) and PM0.5 (cts) particle concentrations inside four Connecticut homes located 30.5–259 m from OWFs, and inside six Connecticut control homes located more than 2 km from the nearest OWF.Materials and methods: PM2.5 (cts) and PM0.5 (cts) measurements were made with a Dylos light-scattering particulate counter.Results: Mean PM2.5 (cts) concentrations were 4.21 times as great in the four OWF exposed homes than the six control homes (0.302 × 106 counts/m3 versus 0.0718 counts × 106/m3 p < 0.001). The mean PM2.5 (cts) concentrations inside the four OWF exposed homes roughly corresponds to a mass PM2.5 of 37 µg/m3, which is above the US EPA 24-h PM2.5 limit of 35 µg/m3. Mean PM0.5 (cts) concentrations were 3.44 times as great in the four OWF exposed homes than in the six control homes (0.657 versus 0.191 × 106/m3 p < 0.001). Mean PM2.5 (cts) and PM0.5 (cts) concentrations were significantly higher in the house 259 m from an OWF as compared with the mean of the six control homes.Conclusion: Existing regulations, such as the present Connecticut law requiring a 61 meter distance between an OWF and neighboring homes, are not adequate to protect the health of neighboring residents.

Feinstaubemissionen aus kleinen Holzfeuerungen

On the combustion test stand of TFZ fine particle emissions from modern residential wood furnaces were determined. Particular focus was set on the main options for primary reduction measures. Apart from the fuel quality (mainly moisture) several operational infl uences were identifi ed as major reasons for increased pollutant emissions. In general, however, it was shown, that a furnace which is operated as intended using a suitable fuel can cause quite low particle emissions.

Particulate matter and gaseous contaminants in indoor environments in an isolated northern community

Objectives. Globally, 86% of exposure to particulate matter (PM) occurs indoors. Wood furnaces and smoke curing are known sources of PM in isolated communities in northern Canada.Study Design. Three homes with wood furnaces, three with oil furnaces, and nine tipis (smoke curing huts) in Deline, Northwest Territories were sampled for carbon monoxide, carbon dioxide, total hydrocarbons, formaldehyde, and for PM of less than 10 microns in diameter (PM10).Results. All gaseous contaminants were below relevant air quality standards. In contrast, all but one environment had PM10 concentrations above standards. The presence of smokers correlated with higher PM10 levels within fuel categories. PM10 did not differ significantly between heating types (means, 0.12–0.53 mg/m3). Exposures to PM10 in tipis averaged 2.3 mg/m3.Conclusion. Residents were exposed to substantial concentrations of PM10 from cigarette smoking, wood stoves, and smoke curing. Concentrations were within the range where respiratory symptoms have been observed. Measures to reduce exposure should consider prevention of adverse health effects and preservation of traditional activities.

Bildung und Eigenschaften von Aerosolen aus Holzfeuerungen

Aerosols from wood combustion originate from two sources: From unburnt carbon and soot as a result of incomplete combustion and from mineral matter which is released as fly ash. Earlier investigations on aerosols from wood combustion were focussing on unburnt pollutants emitted from wood stoves and open fireplaces. Present investigations from well designed and operated automatic wood furnaces show, that a carbon content in the fly ash below 1 to 10 wt% can be achieved. Therefore, unburnt carbon is not the prime source of aerosol emissions in well operated automatic furnaces. The particles generally show a unimodal size distribution with a maximum in the range between 0.05 μm and 0.2 μm. More than 80 mass% of the particles are found in the submicron range. One exception is the combustion of bark where a bimodal size distribution with a second maximum at approximately 5 μm is found. Cyclones are not able to reduce the submicron particles significantly. The emissions of submicron particles from wood furnaces are much higher compared to gas or light fuel oil combustors. Since automatic wood furnaces use a renewable energy source and hence contribute to the aim of global sustainability, measures of reducing the aerosol emissions should be considered in the future. The present paper gives an introduction to the main aerosol formation pathes and presents recent results from different investigations.