1

SUMMARY REPORT FOR PO1-PSA305-BNL

Project Period of Performance: April 25, 2013 – September 30, 2013

BNL Project 89064

Work on this project ended on Sept. 30, 2013. The purpose of this summary report is to review 

the results of work which was done during the course of this project. The primary activity has 

involved laboratory testing of retrofit catalysts applied to hydronic heaters. Other, supporting, 

activities included consultation on up to 5 test reports and technical issues related to testing. 

The overall goal of the catalyst work has been to evaluate the potential for retrofit catalyst

systems to reduce particulate emissions from outdoor wood hydronic heaters. Two specific 

heaters were tested during the course of this work. The first (“Two-Stage”) is a modern hydronic 

heater which includes two stage, downdraft combustion and an induced draft fan. The second 

(“Atmospheric”) is a conventional, updraft, single stage unit without an induced draft fan. The 

Atmospheric unit is typical of many older units which are operating in the field. This unit is not 

on the current EPA list of units which qualify under Phase II of the voluntary program. This unit 

also was not qualified under earlier parts of the voluntary program. The Two-Stage unit has 

lower emissions and is on the list of qualified units. 

This work follows preliminary studies which were done using only the Two-Stage unit. A 

presentation on the results with that unit and one commercially available catalyst were presented 

to EPA on February 28, 2013. At that time the impact of the catalyst was not seen as very 

significant but two simple, potentially beneficial areas of improvement were identified. The first 

was an attempt to control the excess air level and force a catalyst light off event which would 

reduce emissions. The second point related to the operation of the electric heater just under the 

stack catalyst. In the first round of testing, the catalyst heater was not powered continuously and 

this was in accordance with the manufacturer’s instructions. During cold starts of the boiler this 

would make the catalyst ineffective. During this test period the catalyst heater was powered at 

all times to evaluate the best achievable performance. The reason why the catalyst was not 

heated at all times normally is because cold start emissions were less of a concern to the 

manufacturer because the manufacturer saw them as a rare event in the operating cycle of this 

type of hydronic heater. However, EPA and numerous states are concerned about cold starts and 

re-starts that have generated numerous complains. In this study there was a specific focus on 

cold start performance. 

Two specific commercial retrofit catalyst products were evaluated during this work, simply 

identified here as Catalyst 1 and Catalyst 2. The catalyst composition is proprietary. Catalyst 2 

included a provision for the injection of fresh air just below the catalyst with a natural draft 

arrangement. This air is intended to enhance burn-up of carbon and hydrocarbons on the 

catalyst. 
2

SUMMARY OF RESULTS OF CATALYST TESTS

Testing to force catalyst lightoff with oxygen control (PO Task 1, Subtask 1)

This testing was done using the Two Stage hydronic heater and Catalyst 1. These tests 

were done but not found to be an effective method of controlling light off. In subsequent 

tests, with continuous heating of the catalyst, the need for this was seen as minimal.

Testing Catalyst 1 with constant heating to force a light off (PO Task 1, Subtask 2 

and 3)

This testing was done using the Two Stage hydronic heater and Catalyst 1. As in prior 

tests measurements were made over specific parts of the firing cycle including cold start, 

post-reload, hot reload, slumber, and recovery from slumber. Results of tests done are 

summarized in Figures 1, 2, and 3. 

Figure 1. Results of tests with Catalyst 1 with the Two Stage hydronic heater. Particulate 

Emission Index

0

2

4

6

8

10

12

Start Post-reload 1 Reload Post-reload 2

g/kg fuel

Test Period

Emission Index

W Cat

W/O Cat
3

Figure 2. Results of tests with Catalyst 1 with the Two Stage hydronic heater. Particulate 

Emission Factor (lb./million Btu of energy output).

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Start Post-reload 1 Reload Post-reload 2

lb/MMBtu

Test Period

Emission Factor

W Cat

W/O Cat
4

Figure 3. Results of tests with Catalyst 1 with the Two Stage hydronic heater. Particulate 

Emission Rate.

The results of these tests did not indicate a consistent potential for emission reduction as 

significant as was anticipated. Following the completion of these tests and a review with 

EC/R and EPA staff a decision was made not to pursue additional tests with this boiler 

and different operating protocols which might have indicated pathways to better 

performance. Rather, a decision was made to change focus to the Atmospheric hydronic 

heater which was considered to be the higher priority retrofit opportunity and greater 

concern for neighbors. 

Testing Catalyst 2 with the Atmospheric Hydronic Heater (PO Task 1, Subtask 4 

and 5)

Detailed baseline testing and testing with Catalyst 2 was done with this unit over different 

parts of the normal operating cycle, including cold start, as planned. Figures 4, 5, and 6 

provide a summary of the impact of the catalyst on particulate emissions during different 

parts of the firing cycle. In contrast to Figures 1-3 these charts show the results for each 

of the two sampling systems (Box 1 and Box 2) separately. For Figures 1-3 these were 

averaged.

0

50

100

150

200

250

300

350

g/hr

Test Period

Emission Rate

W Cat

W/O Cat
5

Figure 4. Results of tests with Catalyst 2 with the Atmospheric hydronic heater. 

Particulate Emission Index

0

5

10

15

20

25

30

35

40

45

50

g/kg fuel

Test Period

Emission Index

Box 1 (with catalyst)

Box 2 (with catalyst)

Box 1 (without catalyst)

Box 2 (without catalyst)
6

Figure 5. Results of tests with Catalyst 2 with the Atmospheric hydronic heater. 

Particulate Emission Factor (lb/million Btu of energy output).
7

Figure 6. Results of tests with Catalyst 2 with the Atmospheric hydronic heater. 

Particulate Emission Rate.

The results of the catalyst with this hydronic heater show improvements under some 

conditions especially if best burn practices are used by the operator, e.g., small partial 

loads spread over longer time. Most notable is post-reload – however, caution should be 

used in drawing conclusions from this specific result. In the baseline testing the postreload particulate emissions were very high and this was likely simply a result of the 

combustion conditions in the fire box at that time. A factor here could be the higher stack 

temperature with the catalyst which can increase draft and make more oxygen available 

for combustion during this time. Atmospheric draft units are very sensitive to draft 

conditions and low exhaust oxygen conditions were observed at some periods during this 

test work. The different results in the post-reload results may be an artifact of the test 

simply because the two tests are not temporally aligned precisely and/or the process of 

the burning of the wood charge simply occurred differently. 

Results of all measurements made with Atmospheric hydronic heater have been 

assembled in a presentation which is included as an appendix to this report. It is planned 

to review these with EC/R and EPA staff prior to development of final conclusions on the 

effectiveness of the catalysts and future steps. 
8

CONSULTATION ON TEST REPORTS AND TECHNICAL ISSUES

Specific work done under this task included:

 Review of the test report for the Wood Boiler LLC Model E4 hydronic heater. A 

technical note was submitted to EPA for this review.

 Review of the test report for the Woodpecker 45 kW hydronic heater made by 

Webiomass. A brief email note was submitted to EPA for this unit. Very few concerns 

were identified.

 Review of the test report for the Steeltech Model G100 hydronic heater. A technical note 

was submitted to EPA for this review.

 Review and comments on a request for an extension of the approval of the Central Boiler

Maxim 250 hydronic heater.

 Participation in discussion with the test labs and EPA on a technical question related to 

the time interval for measurement and averaging to determine hydronic heater efficiency 

using the stack loss method where the hydronic heater is cycling. A presentation was 

made on this issue and presented during a webinar with the commercial test labs.
9

Appendix I – Presentation on the Results of Tests with Catalyst 2 with Atmospheric 

Hydronic Heater. Prepared for review with EC/R and EPA staff.
Preliminary Highlights

Test of Central Boiler 5036 with 

Clear Skies Exhaust Catalyst

T. Butcher
Events

With Clear Skies Cat

Sept. 29th, 2013

Time (min) Event

0

Gas analyzers started sampling (CO, O2

stack and DT, HC)

1.00 – 3.69 150 lb fuel test charge added

4.70 – 10.23

Start-up PM sampling phase #1

Wohler PM analyzer sampling (30 

minutes)

12.66 – 15.93

Start-up PM sampling phase #2

Wohler PM analyzer still sampling

18.11 – 21.05

Start-up PM sampling phase #3

Wohler PM analyzer still sampling

63.64 – 93.58

Slumber PM sampling period

Wohler PM analyzer sampling

103.89 – 127.37

Relight from slumber PM sampling 

period

212.40 – 214.49 100 lb fuel test charge #2 added

215.59 – 245.60

Reload PM sampling period

Wohler PM analyzer sampling

262.37 – 292.34

Post-reload PM sampling period

Wohler PM analyzer sampling
0

300

600

900

1200

1500

0 100 200 300 400

Temperature (F)

Time (min)

Flue Gas Temp

Fuel charge added

Start up sampling

Slumber sampling

Relight from slumber sampling

Reload sampling

Steady state sampling

With Clear Skies Cat

Sept. 29th, 2013 Flue gas temperature and events

Post-reload sampling
Catalyst light-off

With Clear Skies Cat

Sept. 29th, 2013

0

300

600

900

1200

1500

1800

0 100 200 300 400

Temperature (F)

Time (min)

Flue Gas Temp

Post Cat Temp

Fuel charge added

Start up sampling

Slumber sampling

Relight from slumber sampling

Reload sampling

Steady state sampling Post-reload sampling
Catalyst pressure drop

With Clear Skies Cat

Sept. 29th, 2013

0

2

4

6

8

10

12

14

0

300

600

900

1200

1500

1800

0 100 200 300 400

Catalyst pressure drop (Pa)

Temperature (F)

Time (min)

Flue Gas Temp

Post Cat Temp

Fuel charge added

Start up sampling

Slumber sampling

Relight from slumber sampling

Reload sampling

Steady state sampling

Cat Delta P

Post-reload sampling
Flue gas oxygen

With Clear Skies Cat

Sept. 29th, 2013

0

5

10

15

20

25

30

0

300

600

900

1200

1500

1800

0 100 200 300 400

O2 (%)

Temperature (F)

Time (min)

Flue Gas Temp

Post Cat Temp

Fuel charge added

Start up sampling

Slumber sampling

Relight from slumber sampling

Reload sampling

Steady state sampling

Flue Gas Oxygen (O2)

Post-reload sampling
Dilution Tunnel CO

With Clear Skies Cat

Sept. 29th, 2013

0

1000

2000

3000

4000

5000

6000

0

300

600

900

1200

1500

1800

0 100 200 300 400

CO (ppm)

Temperature (F)

Time (min)

Flue Gas Temp

Post Cat Temp

Fuel charge added

Start up sampling

Slumber sampling

Relight from slumber sampling

Reload sampling

Steady state sampling

Dilution tunnel CO

Post-reload sampling
Flue HC

With Clear Skies Cat

Sept. 29th, 2013

0

2000

4000

6000

8000

10000

12000

14000

16000

0

300

600

900

1200

1500

1800

0 100 200 300 400

Hydrocarbons (ppm)

Temperature (F)

Time (min)

Flue Gas Temp

Post Cat Temp

Fuel charge added

Start up sampling

Slumber sampling

Relight from slumber sampling

Reload sampling

Steady state sampling

Flue Hydrocarbons (ppm)

Post-reload sampling
Events

Baseline Test

Sept. 20th, 2013

Time (min) Event

0

Gas analyzers started sampling (CO, O2stack and 

DT, HC)

6.12 – 8.39 150 lb fuel test charge added

8.47 – 15.94

Start-up PM sampling phase #1

Wohler PM analyzer sampling (30 minutes)

17.95 – 20.21

Start-up PM sampling phase #2

Wohler PM analyzer still sampling

26.59 – 30.02

Start-up PM sampling phase #3

Wohler PM analyzer still sampling

96.44 – 115.55 Slumber PM sampling period

117.57 – 147.59 Relight from slumber PM sampling period

160.08 – 160.84 100 lb fuel test charge #2 added

193.96 – 196.05

Post-reload PM sampling period

Wohler PM analyzer sampling
Flue gas temperature and events

Baseline Test

Sept. 20th, 2013

0

300

600

900

1200

1500

0 100 200 300 400

Temperature (F)

Time (min)

Flue gas temp

Fuel charge added

Start up sampling

Slumber sampling

Relight from slumber sampling

Steady state sampling Post-reload sampling
Flue gas oxygen

Baseline Test

Sept. 20th, 2013

0

5

10

15

20

25

0

300

600

900

1200

1500

0 100 200 300 400

Temperature (F)

Oxygen (%)

Time (min)

Flue gas temp

Fuel charge added

Start up sampling

Slumber sampling

Relight from slumber sampling

Steady state sampling

Flue gas oxygen (O2)

Post-reload sampling
Dilution Tunnel CO

Baseline Test

Sept. 20th, 2013

0

1000

2000

3000

4000

5000

6000

0

300

600

900

1200

1500

0 100 200 300 400

CO (ppm)

Temperature (F)

Time (min)

Flue gas temp

Fuel charge added

Start up sampling

Slumber sampling

Relight from slumber sampling

Steady state sampling

Dilution tunnel CO

Post-reload sampling
Flue HC

Baseline Test

Sept. 20th, 2013

0

2000

4000

6000

8000

10000

12000

0

300

600

900

1200

1500

0 100 200 300 400

Flue Hydrocarbons (ppm)

Temperature (F)

Time (min)

Flue gas temp

Fuel charge added

Start up sampling

Slumber sampling

Relight from slumber sampling

Steady state sampling

Flue HC

Post-reload sampling
CATALYST VS. NO CATALYST 

EMISSION PERFORMANCE
Flue gas temperature and events

9/20 Events

9/29 Events

Post-reload sampling
Flue gas oxygen

9/20 Events

9/29 Events

Post-reload sampling
Dilution Tunnel CO

9/20 Events

9/29 Events

Post-reload sampling
Mass burned

9/20 Events

9/29 Events

Post-reload sampling
0

1

2

3

4

5

6

7

8

9

10

Start Up #1 Start Up #2 Start Up #3 Total Start

Up

Steady

State

Slumber Recover

from

Slumber

Reload #2

lb/MMBtu

Test Period

Emission Factor

Box 1 (with catalyst)

Box 2 (with catalyst)

Box 1 (without catalyst)

Box 2 (without catalyst)

PostReload 
0

500

1000

1500

2000

2500

Start Up #1 Start Up #2 Start Up #3 Total Start

Up

Steady

State

Slumber Recover

from

Slumber

Reload #2

g/hr

Test Period

Emission Rate

Box 1 (with catalyst)

Box 2 (with catalyst)

Box 1 (without catalyst)

Box 2 (without catalyst)

PostReload 
0

5

10

15

20

25

30

35

40

45

50

Start Up #1 Start Up #2 Start Up #3 Total Start

Up

Steady

State

Slumber Recover

from

Slumber

Reload #2

g/kg fuel

Test Period

Emission Index

Box 1 (with catalyst)

Box 2 (with catalyst)

Box 1 (without catalyst)

Box 2 (without catalyst)

PostReload 
September 29th, 2013 September 20th, 2013

Box 1 (with catalyst) Box 2 (with catalyst) Box 1 (without catalyst) Box 2 (without catalyst)

State

Emission 

Factor 

lb/MMBtu

Emission 

Rate g/hr

Emission 

Index 

g/kg fuel

Emission 

Factor 

lb/MMBtu

Emission 

Rate g/hr

Emission 

Index 

g/kg fuel

Emission 

Factor 

lb/MMBtu

Emission 

Rate g/hr

Emission 

Index 

g/kg fuel

Emission 

Factor 

lb/MMBtu

Emission 

Rate g/hr

Emission 

Index 

g/kg fuel

Start Up 

#1 5.242 680.144 26.257 5.634 731.055 28.222 4.481 429.959 22.69 4.855 465.819 24.582

Start Up 

#2 4.982 793.731 24.957 5.717 912.141 28.639 9.134 2239.899 46.253 8.287 2027.035 41.961

Start Up 

#3 3.978 632.677 19.924 4.848 771.07 24.283 7.397 1879.076 37.458 6.365 1654.429 32.232

Total 

Start Up 4.752 697.2 23.805 5.423 797.058 27.164 7.6 1174.524 38.486 6.448 1070.449 32.649

PostReload 0.192 23.429 0.963 0.18 21.98 0.903 3.698 734.551 18.726 3.008 597.521 15.233

Slumber 0.753 6.85 3.772 0.852 7.751 4.268 4.482 19.32 22.696 4.681 20.175 23.701

Recover 

from 

Slumber

0.964 76.815 4.828 0.721 76.885 3.61 1.19 45.973 6.028 1.137 43.906 5.757

Reload 

#2 0.205 32.901 1.029 0.119 31.9 0.998 - - - - - -
Initial hot coal bed & 150 lb fuel charge
Visual start up emissions 

 (2 mins & 8 mins after addition of wood)
Second coal bed before 100 lb fuel 

charge
Visual emissions after reload