Grantee Research Project Results
Final Report: Improved Combustion and Emissions for MSW Burn-Management Unit Applicable to Remote Communities in Alaska
EPA Contract Number: EPD08044Title: Improved Combustion and Emissions for MSW Burn-Management Unit Applicable to Remote Communities in Alaska
Investigators: Marshall, Martin C.
Small Business: Tok Welding and Fabrication
EPA Contact: Richards, April
Phase: I
Project Period: March 1, 2008 through August 31, 2008
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2008) RFA Text | Recipients Lists
Research Category: SBIR - Agriculture and Rural Community Improvement , Small Business Innovation Research (SBIR)
Description:
The Phase I project objective was to investigate whether insulation of the conventional burn unit manufactured by Tok Welding and Fabrication could increase burn temperatures and thus improve combustion efficiency and emissions. A longitudinal comparative study was performed with two burn units operated simultaneously during a 6 week period in summer 2008.
Figure 1. Conventional non-insulated unit, “Burn Unit 1” on the left and insulated unit “Burn Unit 2” on the right.
Summary/Accomplishments (Outputs/Outcomes):
Phase I was a success in that it identified, for the first time, burn unit temperatures generated in situ with an Alaska Village waste stream, as well as the minimum level of peak temperature achievable. As expected based on the limited number of open burning studies conducted for “backyard burn barrels,” temperatures were highly variable between trials for the same unit. Temperature profiles also differed between the two units during the trials. Opacity of the two smoke streams was likewise variable between trials and differed markedly from each other during trials. Opacity was measured (Method 9) for one trial during an evaluation visit by the Environmental Protection Agency (EPA) Alaska Office Air Quality Scientist. Opacity was markedly better for the insulated unit for the bulk of the burn.
Maximum stack temperature achieved (1664°F) was significantly higher than expected, although it ranged over 750°F in the same unit between trials. Maximum temperatures were achieved more quickly and dropped more quickly than expected as well. Stack temperatures in the insulated unit took slightly longer to achieve maximum temperature and the insulated unit maintained a high temperature for a longer time than the non-insulated unit.
Another difference between pilot and field trials was waste type and water content. With one exception, pilot trials were conducted with cardboard only, presenting a significantly different BTU/lb and water content.
Results:
Temperature profiles, ambient weather, and waste loading for each trial were recorded. Table 1 provides descriptive statistics over the course of the project. The gross variability in the trials resulted in the decision to not perform further statistical analyses regarding the existence and value of significant differences in temperatures. Phase II of this project will provide more detailed information regarding emissions and will allow for a larger number of pilot runs with controlled, identical waste streams. Visual observations documented by photography indicated better opacity overall from the insulated unit. Some periods of time during some trials showed higher opacity for the insulated unit compared with the non-insulated unit. This result, however, may be due more to the variability in waste load between the units than the unit design. The duration of the project did not allow for evaluation of the impact of the expansion chamber or agitator baffles on the temperature profiles. Both features displayed marked impingement and settlement of particulate matter at project end.
Lighting one of the Burn Units
Discussion:
Interestingly, the insulated unit exhibited a lower maximum temperature for at least 4 out of 6 of the pilot trials (an equipment malfunction resulted in non-capture of the insulated unit temperature for one pilot trial). The insulated unit, however, had the higher peak during 4 of the 6 field trials where temperature data were collected. The duration of the project, number of parameters involved in ultimate temperatures, and field limitations did not allow for an evaluation as to the underlying causes or of the role of individual parameters. One thought, however, was that the insulated unit would perform better with a fuller waste load. Indeed, during the one trial where the burn units were loaded to the higher percent capacity, the greatest degree of peak temperature difference occurred between the two units of the trials where the insulated unit achieved the highest temperature.
Insufficient data are available with identical waste loading (capacity and type) to make a determination as to whether insulation provides a reliably higher peak temperature. With higher waste loading of mixed wastes, indications are that peak temperature is either similar or higher than a non-insulated unit. Higher waste loading would mean that villages would need to burn less often, offering advantages in burn time flexibility and smoke exposure duration. The cooler outside wall temperatures of the insulated units offer an additional advantage in safety from accidental burn injury.
The variability in hottest points of the unit during and between trials demonstrates that waste loading has an impact on ultimate combustion efficiency. A similar finding has been demonstrated with burn barrels. Waste loading parameters must be evaluated to optimize a design.
Total burn duration, at high, medium, and low temperatures, is longer with the insulation unit. Smoke opacity was evaluated overall to be significantly better with the insulation unit. It is not clear whether net positive, or significant, benefit was achieved with the passive agitator or expansion chamber features. Evaluation of these features clearly is needed as well in future trials.
Conclusions:
From Phase I, it is clear that insulation has a marked positive magnitude effect on the temperature profile. Due to insufficient data, Tok Welding and Fabrication could not determine with finality whether insulation has a marked effect on peak temperature; however, the two highest peak temperatures (based on 10 second interval logging) were achieved by the insulated unit. Also, indications were that higher waste loading may improve insulated unit performance more than non-insulated unit performance, resulting in a more consistent high-peak temperature range. An insulation design is thus a promising, low-cost, low-maintenance parameter to further develop so as to identify an optimum design for emissions. A cleaner burn is accomplished with hotter temperatures, longer time-in-transit, and higher turbulence, and the insulated unit appears to offer these at a low additional production cost.
Tok’s insulated design resulted in a peak temperature during a field trial with an unsorted weekly village waste stream of more than 1,664.06°F—which approaches that of incinerator technology. This temperature is significantly higher than previously thought attainable for simple burn unit design, and based on basic combustion principles, offers the potential for cleaner emissions than other burn options feasible for small and isolated rural Alaska villages.
Also identified in Phase I as a promising development opportunity are the “local behavior” operating parameters of waste load and type. Phase I demonstrated that these parameters have a marked effect on both temperature profile and peak temperature, and their determination and use of their optimum values (i.e., the optimum operation) can contribute significantly in achieving higher temperatures consistently and for longer duration periods.
To develop the technology for commercialization in a manner that provides the highest degree of environmental health benefits to the target audience, there is a need to continue the R & D so as to refine design based on parameter evaluations. Phase II will allow time for an adequate duration of testing, as well as direct testing of particulate emissions, thus enabling Tok to draw conclusions regarding the best design.
Table 1. Comparison Between Insulated and Non-insulated Burn Unit Temperature Profiles
Fuel Type: |
Cardboard (weighed identical) |
MSW (approx. similar load) |
||||||
Burnbox: |
#1 (Non-insulated) |
#2 (Insulated) |
#1 (Non-insulated) |
#2 (Insulated) |
||||
Number of datasets: |
5 |
4 |
8 |
8 |
||||
Mean |
S.D. |
Mean |
S.D. |
Mean |
S.D. |
Mean |
S.D. |
|
Peak Temperature (°F) |
1521.25 |
65.38 |
1457.62 |
90.46 |
1176.12 |
275.94 |
1151.37 |
318.87 |
Initial Phase Duration (min to peak temp) |
5.90 |
0.89 |
6.50 |
1.73 |
8.12 |
2.50 |
10.58 |
5.96 |
Mid-Range Duration, Heating (min between 390°F and 850°F) |
1.33 |
0.41 |
1.88 |
0.85 |
2.45 |
0.96 |
4.08 |
3.20 |
Mid-Range Duration, Cooldown (min between 850°F and 390°F) |
13.47 |
3.84 |
25.88 |
8.07 |
18.86 |
7.05 |
25.67 |
8.11 |
High Temp Range Duration (min over 850°F) |
7.00 |
0.71 |
8.00 |
1.83 |
10.64 |
8.46 |
14.00 |
17.92 |
The authors would like to thank the Native Village of Dot Lake for participating in this project. Without their time and assistance, this project would not have been possible.
Supplemental Keywords:
small business, SBIR, EPA, remote communities, Alaska Native, solid waste, waste management, communal burning, open burning, burnbox, burnbox emissions, technology for villages, technology for small communities, environmental health, health risk, disease transmission, fire danger, high temperature, air pollution, , Scientific Discipline, Waste, Environmental Engineering, Municipal, combustion contaminants, alternative burnbox technology, municipal waste combustor (MWC), emissions control,, Scientific Discipline, Waste, Municipal, Environmental Engineering, municipal waste, emissions control, municipal waste combustor (MWC), combustion contaminantsThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.