Understanding and controlling the moisture and ash content of biomass is important for optimizing its efficiency as a fuel.
Biomass is one of the leading forms of alternative energy sources. It is renewable energy derived from living organic material, or material that was recently alive. Wood pellets, corn husks, refuse, black liquor (a waste product of the paper making industry), and alcohol fuels are common examples of materials classified as biomass. These sources are more sustainable than fossil fuels and, like fossil fuels, are typically incinerated for energy production. However, incomplete combustion generates black carbon, which is a pollutant.
Ovens and Furnaces have traditionally been used to measure moisture and ash content in biomass materials
Moisture analysis of biomass materials has traditionally been performed using a conventional oven, while ash content determination has traditionally been performed using a furnace. These methods are relatively easy to follow but can suffer from low repeatability if not performed in a consistent manner. They also have long test times, which can hinder the manufacturer’s ability to address problems that may arise during processing and can severely limit the material’s ability to act as a suitable energy alternative.
Computrac offers a fast, accurate and repeatable alternative to ovens and furnaces
The Computrac® MAX® 5000XL moisture and ash analyzer offers quick, accurate moisture and ash analysis. It is able to provide real-time results for moisture, solids and ash with a single sample, has a maximum temperature of 600°C and a maximum sample size of 100 grams, giving it the versatility to test a wide range of materials. The MAX 5000XL also correlates well to standard reference methods but is able to provide results much more quickly, allowing manufacturers the opportunity to adjust processes to maximize quality and output.
Comparative moisture and ash analysis was performed to evaluate the Computrac MAX 5000XL as an alternative to the oven and furnace reference methods
Samples were stored as received in plastic storage bags. Each sample was ground into small particle sizes using a coffee grinder for testing. The material was not sifted for use and there was a range of particle sizes. The material had a similar consistency to that of coffee beans that had been processed in the same manner.
Reference Moisture Testing was conducted using aluminum pans and a Blue M V01218A vacuum oven
All pans were washed and preconditioned prior to testing. Each sample pan was weighed prior to testing and approximately 3g of sample was added to the sample pan. It was then placed on the center rack of the oven. The sample was tested at 105°C under 30” of Hg for 16 hours. At the end of testing the vacuum pressure was released and the sample pans were transferred to a desiccator and cooled to room temperature. The dried pan and sample were weighed and the change in weight was calculated.
Reference ash testing was conducted using ceramic crucibles and a Fischer Scientific 650-58 muffle furnace
All crucibles were washed and preconditioned prior to testing. Each crucible was weighed first, then approximately 3g of sample were added to each crucible. After the sample was added the crucibles were placed inside the furnace while the furnace was at room temperature. The furnace was then set to 600°C. Once the chamber reached 600°C the sample was exposed for 3 hours. At the end of the test the furnace temperature was reduced to 250°C and once it stabilized at this temperature the crucibles were moved to the desiccator to cool. Once the crucibles were at room temperature they were weighed and the ash content was calculated.
Moisture and ash testing was conducted on the MAX® 5000XL using the linked testing option
This allowed for a moisture test to be conducted, then an ash test to be conducted using the same sample and without any user adjustments, input or interface. Testing conditions were established prior to testing and in-situ monitoring was conducted. Waffle pans were preconditioned prior to testing to remove any film that was used to prevent adherence during stacking. The sample was evenly distributed on the sample pan for each test.
The testing conditions in table 1, below, represent the conditions for this specific analysis. For different materials these conditions would be different in order to optimize results.
Table 1: Computrac MAX 5000XL Testing Parameters
Testing Conditions |
Moisture Test |
Ash Test |
| Idle Temperature | 50°C | 120°C |
| Test Temperature | 125°C | 600°C |
| Ending Criteria | 0.5000%/minute | 0.0500%/minute |
| Sample Size | 7g ± 1g | 7g ± 1g |
| Idle Temperature | Standard | Standard |
| Idle Temperature | 5 seconds | 5 seconds |
Table 2, below, shows the mean results of testing 4 different biomass materials for their moisture content. There is strong correlation and repeatability between the oven reference method and the Computrac® MAX® 5000XL, but the MAX 5000XL required far less time to perform the test.
Table 2: Moisture results for biomass materials
Material |
MAX® 5000XL |
|
Oven Method |
| Wood Pellet | 3 minutes 5.9757 0.2283 |
Test Time % Moisture S.D. |
16 hours 5.4472 0.0331 |
| Pecan Shell | 5 minutes 12.5823 0.2893 |
Test Time % Moisture S.D. |
16 hours 12.6090 — |
| Wood Chip | 4 minutes 5.4632 0.2243 |
Test Time % Moisture S.D. |
16 hours 5.435 — |
| Wood Pellet with pecan Bagger | 4 minutes 6.1425 0.0922 |
Test Time % Moisture S.D. |
16 hours 6.247 — |
Table 3 shows the ash results for the same materials. Strong correlation and repeatability as well as a significant difference in test times can be seen on the table below. It should be noted that the test times reported in table 3 under the heading “Furnace Method” are only the time that the material is at the prescribed test temperature. They do not account for the time it takes for the furnace to reach the test temperature or the time it takes for the crucibles to cool to room temperature. The test times shown under the heading “MAX® 5000XL” are average test times for each material taken from start to finish.
Table 3: Ash results for biomass materials
Material |
MAX® 5000XL |
|
Furnace Method |
| Wood Pellet | 25 minutes 1.3293 0.1021 |
Test Time % Ash S.D. |
1 hour 1.397 0.1305 |
| Pecan Shell | 35 minutes 2.1294 0.2437 |
Test Time % Ash S.D. |
2 hours 2.2734 0.0944 |
| Wood Chip | 40 minutes 0.5575 0.0463 |
Test Time % Ash S.D. |
2 hours 0.5373 0.0582 |
| Wood Pellet with pecan Bagger | 30 minutes 3.7175 0.3465 |
Test Time % Ash S.D. |
2 hours 4.5263 1.283 |
Graphs 1 and 2 show real time test results for moisture and ash analysis using the Computrac® MAX® 5000XL. Adjustments can be made to the test criteria based on the characteristics of the graph. For instance, the test graph for ash shows very little change in the ash content of the material after 2400 seconds. From this the ending criteria can be changed to optimize the test times if it is desired.
Graph 1: Test graph for moisture analysis of wood pellets
Graph 2: Test graph for ash analysis of wood pellets
The Computrac® MAX® 5000XL is a viable option for use in moisture and ash investigation of biomass materials
The user interface was able to decrease sample handling procedures and any user error in weight calculations. The MAX® 5000XL outperformed the oven and furnace reference testing methods in test times while providing accurate and repeatable results. The in-situ measurement capabilities allowed for immediate test analysis and optimization of testing conditions.
If you have any questions or would like to learn more about the Computrac MAX 5000XL, contact us online, visit our page about moisture, solids and ash testing for biomass materials, or give us a call at (800) 528-7411.