Time (mins) 0 20 40 60 80 100 120 140 160 180Concentration(mg/MJ)

0.1 1 10 100 1000

Time (mins) 0 60 120 180Concentration(mg/MJ)

0.1 1 10 100 1000 CO NOx SO2 PM 2. 5 

# Gaseous **and Particle Emission**  **Rates from a High Efficiency Wo**  **od Boiler Using T** 

**wo T ypes**  **of Fuel: W ood Chips and W**  **ood Pellets** J. Laing, S. Raja, T. M. Holsen, P. K. Hopke 

## Intr **oduction** There has been mounting concern over the health risks posed by pollutants emitted from biomass combustion, particularly fine PM. However , newer designs of fully automated, high ef ficiency wood boiler systems have been presented as a solution due to their low emissions. Continuous measurements of carbon monoxide, nitrogen oxides, sulfur dioxide, and PM 2.5 from a Hamont CA Tfire (Hamont Consulting and Engineering, Austria) gasification wood boiler (Figure 1) running at steady state were determined using two types of fuels, wood pellets and wood chips. The combustion of both fuel types resulted in low emissions of carbon monoxide and high combustion ef ficiencies. Higher fuel nitrogen and sulfur content resulted in higher emissions of nitrogen oxides and sulfur dioxide, respectively . It was also seen that higher ash content lead to higher PM 2.5 emissions. 

## Results

**Summary of Findings**  Selected two and a half hours of continuous gaseous and particle emission measurements using wood pellets and wood chips are displayed in Figures 3 and 4, respectively

. The temporal variations in emissions are seen collectively among all gaseous species, indicating that they are a function of small dif ferences in boiler output. Emissions factors of gaseous emissions and combustion ef ficiencies from the combustion of wood pellets and wood chips are provided in Table 2. Carbon Monoxide emissions for both fuel sources were low and comparable with previous studies of pellet burner/boiler emissions. Combustion ef ficiencies (CO 2 /(CO 2 + CO)*100) demonstrate highly ef ficient combustion in both boilers. From the limited samples examine here, the higher fuel nitrogen and sulfur content (T

able 1) resulted in higher NO x and SO 2 emissions (T able 2), verifying the fact that the gaseous emissions are formed through the oxidation of their fuel bound constituents. Higher ash content resulted in higher PM2.5 emissions. Wi th nearly complete combustion achieved, the particulate matter is predominately derived from inor ganic ash

- forming components in the fuel vaporizing and subsequently nucleating in the flue gas.

**Acknowledgements** This study was funded by the New Yo rk State Energy Research and Development Authority (NYSERDA) which is supported by the U

. S

. Environmental Protection Agency

. This work has not been subjected to the Agency’ s required peer and policy review and therefore does not necessarily reflect the views of the agency and no official endorsem ent should be inferred

. Som e of equip men t used in this study was provided by the New Yo rk State Foundation for Science, Te chnology and Innovation (NYST AR)

. We thank Sean McMahon and Ya ng Qi for their help in the field work

. We also thank the volunteers for their participation in this study

. 

## Experimental **Methods** CO, NO x , SO 2 , and PM 2.5 emission rates from the gasification wood boiler running at steady state were determined using two types of fuels, wood pellets and wood chips. The boiler has a thermal capacity of 150kW and was run at 76% and 60% capacity for wood pellets and wood chips, respectively

. A dilution stack sampling system (Figure 2) conforming to EP A’ s conditional test method (CTM) 039 was used to provide sample gas to ambient gas monitors and a TEOM with FDMS (Models 42i, 43i, 48i, and 8500b , Thermo Scientific, Franklin, MA). A switch valve prior to the gas monitors provided background ambient concentrations ten minutes out of every hour . Direct measurements of carbon dioxide were made using an in

- stack Bacharach PCA ® 2 . **Figur e 2.**  Dilution Sampling System. **Ta ble**  **1**
**.** Characteristics of the Fuel

. 

## Fuel **Analysis** The wood pellets used were manufactured by New England Wo od Pellet, LLC and the wood chips were waste wood scraps with a considerable amount of fines

. Samples were collected for every testing period from the boiler feed bin

. Gross heating value, ash content, moisture content, sulfur content, and nitrogen content were determined (T able 1 )

.



### Wo **od Pellets**  **Wo od** 

**Chips** heat content (MJ/lbs) 8.49 6.72 moisture (%) 4.80 26.6 ash (d.w . %) 0.60 1.79 carbon (d.w . %) 51.5 45.0 nitrogen (d.w . %) 0.13 0.37 sulfur (d.w

. ppm) 70.1 175 **Figur e 1.**  Hamont CA Tfire Wo od Boiler

. **Ta ble 2.**  Gaseous and particle emission factors and combustion ef ficiency for wood pellets and wood chips. **Emission Factors (mg/MJ) combustion**  **Fuel Sour ce**  **CO NO**  **x SO**  **2 PM**  **2.5 CO**  **2 (%)**  **efficiency** Wo od Pellets 11 5 18.4 0.26 25.1 7.86 99.89 Wo od Chips 125 127 1.42 41.3 10.1 99.94 **Figur e 3.**  Gaseous and particle emission concentrations during steady state operation for wood pellets. **Figur e 4.**  Gaseous and particle emission concentrations during steady state operation for wood chips.

**Acknowledgements** This study was funded by the New Yo rk State Energy Research and Development Authority (NYSERDA) which is supported by the U

. S

. Environmental Protection Agency

. This work has not been subjected to the Agency’ s required peer and policy review and therefore does not necessarily reflect the views of the agency and no official endorsem ent should be inferred

.