(709h) A Capital and Energy Efficient Alternative Emissions Control Technology for Controlling Emissions Using Bead Activated Carbon

The Fluidized Bed Concentrator (FBC) with Bead Activated Carbon (BAC), shown in Figure 1, is a lifetime capital and energy efficient emissions control technology. It adsorbs emissions using bead activated carbon in a fluidized bed concentrator. This technology has already been commercialized in many applications today including automotive and electronics manufacturing. Captis Aire provides this patent pending Fluidized Bed Concentrator (FBC) emissions control technology[i] for controlling emissions[ii] from wood drying via license from technology owner. Wood drying applications include oriented strand board (OSB), wood pellets, plywood, etc.

Problem: The industry standard emissions control device, the Regenerative Thermal Oxidizer (RTO) with a Wet Electrostatic Precipitator (WESP), controls emissions by oxidizing (burning) emissions to form carbon dioxide (CO2).

Potential Solution: By contrast, the FBC uses Bead Activated Carbon (BAC) in a fluidized bed to efficiently control emissions via adsorption from the air.

Potential Benefits: The FBC utilizes less energy, creates less greenhouse gas CO₂ and NOx emissions, reduces operating costs, and optionally recovers valuable organic byproducts versus the industry standard, the RTO,in dilute airstreams.

DESCRIPTION OF TECHNOLOGY: Figure 2 shows the 4 primary parts of the FBC

Adsorber: The adsorber is filled with very adsorbent activated carbon beads in a series of perforated plate adsorption trays. Contaminated exhaust air from the dryers enters from the bottom, passing upward through the adsorption trays, fluidizing the activated carbon adsorbent. When the process air interacts with the BAC it adsorbs (captures) the emissions.

Desorber: In the desorber, the carbon adsorbent with adsorbed emissions is heated causing it to release the emissions into a low volume inert carrier nitrogen gas stream.

Condenser or Efficient Oxidation: The concentrated gas stream exiting the desorber contains the released emissions, including terpenes. Emissions are concentrated, such that the vapors can be cooled via a tube and shell condenser converting the vapors to liquid. The liquid terpenes can then be recovered and sold. As an alternative, users can efficiently oxidize the emissions in the concentrated gas stream.

Side Stream Reactivator (SSR): The SSR continuously reactivates a small portion of the carbon by heating it to 1450⁰F with water. This enhances its ability to continuously adsorb emissions long term.

ENGINEERING ESTIMATE CALCULATIONS OF THE VALUE OF THE FBC TECHNOLOGY:

Figure 3 shows the potential value of the FBC technology has been quantified using industry accepted referenced methodologies. Simplified engineering estimation calculations are described herein

1. Reduced Energy Usage (Natural Gas) due to elimination of energy used to heat the air going through the RTO: Multiple credible references[iii] describe the calculations necessary to estimate energy used in the RTO to heat the air[iv]. Calculators are also provided by the EPA[v], Cycle Therm[vi], and Captis Aire[vii]. All these sources rely on a single primary factor to calculate energy required to heat the air. This factor is the specific heat of air which is the number of British Thermal Units (BTUs) required to heat one pound of air by one °F. This factor along with the system specific factors including the standard cubic feet per minute (sCFM) of air, the temperature increase, the density of air, and conversion factors provide the number of BTUs. These factors are used together with the energy efficiency and the heat generated by the oxidation of the emissions to calculate the BTUs of energy required to heat the air going through the RTO. Users can then multiply BTUs times the forecasted long-term cost of natural gas to estimate the long-term cost of natural gas required over the 20+ year life of the RTO.
2. Reduced Greenhouse Gases (GHG) generated from burning natural gas[viii]: Based on the amount of carbon in natural gas and its stoichiometric conversion to carbon dioxide (CO₂), we can calculate tons of CO₂ eliminated via the elimination of the oxidation of natural gas to heat the air in the RTO.
3. Value of Carbon Offsets: This is still under investigation, but in conversations with American Carbon Registry[ix] and ClimeCo[x], it may be possible to sell carbon offsets for a site converting to the FBC technology. Potential values for these offsets varies widely. [xi] However American Carbon Registry estimated the value of carbon offsets for an FBC project at $5/ton.[xii] Given this estimate, a site reducing GHG by 12,000 tons/year may be able to sell these offsets for $60,000 per year.
4. Reduced Electricity Usage: The horsepower required to run the fans to move the process air through the media is reduced for the FBC due to the fact that it is fluidized (moving) rather than packed (non-moving). Horsepower can first be converted to kW·h, then the site-specific electricity costs and operating hours per year can be used in combination to estimate electricity savings.
5. Revenue from Sales of Terpenes: The Pine Chemicals Association has documented the gallons of terpenes per oven dry ton of wood in a variety of tree species. Typically, there is ~1 gallon of turpentine (terpenes)[xiii] per oven dry ton of wood product produced from green pine wood. If 75% of this is evaporated and captured from the drying process, the value of the terpenes per year can be calculated by multiplying this yield by a typical price per gallon[xiv] for terpenes.

PROCESS INTENSIFICATION CHARACTERISTICS: Comparison of the FBC vs the RTO

Table 1 shows the FBC process intensification characteristics. The amount of energy used is reduced due to two factors: 1) the dramatic operating temperature reduction and, 2) the media configuration advantage. First, the operating temperature is the temperature at which the air exits the process, as opposed to >1400°F to oxidize (burn) the emissions. This eliminates the need for natural gas in the recovery system. Second, the media configuration is advantageous in that the media through which the process air has to be forced is fluidized. This reduces the amount of fan horsepower required and thus the amount of electricity required to run the system.

PROJECT APPROACH:

Two pilot trials at a commercial oriented strand board manufacturer were run. In 2017, a 200 Cubic Feet per Minute (CFM) small-scale pilot adsorber was run to demonstrate its ability to adsorb emissions from wood drying under commercial manufacturing conditions. In 2018, this pilot unit ran safely for 6 months with over 1700 hours on-line. System included adsorber, desorber, and condenser. The SSR performance was simulated by semi-continuous additions of virgin carbon during air emissions compliance testing. The differential pressure across the adsorber was 2.5-4.5 inches of water. No natural gas was utilized to oxidize (burn) the emissions. Ability to meet air emissions control compliance, per the PCWP MACT requirements, was determined by two independent certified air emissions[xv] stack testing companies[xvi] during two separate testing events.

RESULTS:

• The FBC pilot met the PCWP MACT requirement of >90% Reduction Efficiency[xvii] in both tests. In the second test, the system met the compliance requirements three times in a row, over each of the three one-hour testing intervals.
• No natural gas was used.
• FBC operated safely and reliably for 6 months.
• Terpenes, composed primarily of Alpha and Beta Pinenes, were collected.
• State and Federal environmental personnel reviewed these results and were supportive of permitting for a full commercial FBC system.

ACKNOWLEDGEMENTS: The author recognizes inputs from a broad spectrum of personnel at the commercial OSB manufacturer and at Environmental C&C including Harold Cowles, John Berger, and Jim Starek.

[i] “METHODS AND SYSTEMS FOR RECOVERING TERPENE COMPOSITIONS FROM WOOD DRYING EXHAUST”. World Intellectual Property Organization (WIPO) website. https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2019148208 (Accessed Feb 3, 2021).

[ii] “WO2019148207 - METHODS AND SYSTEMS FOR CONTROLLING EMISSIONS FROM WOOD DRYING PROCESSES”. WIPO website. https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2019148207 (Accessed Feb 3, 2021).

[iii] ICAC Guidance Method for Estimation of Gas Consumption in a RTO. Institute of Clean Air Companies website. https://cdn.ymaws.com/www.icac.com/resource/resmgr/RTO-F1.pdf (Accessed Jan 20, 2021).

[iv] “As a norm, the industry standard calculation for obtaining BTU output”. Ruppair website. https://www.ruppair.com/documents/white-papers/Actual%20Air%20Density%20BTU%20Calculation.pdf (Accessed December 28, 2020).

[v] “Air Pollution Control Cost Estimation Spreadsheet”. Environmental Protection Agency (EPA) website. https://www.epa.gov/sites/production/files/2018-01/oxidizers_calc_sheet_finalversion_1-16-2018.xlsm (Accessed Feb 3, 2021).

[vi] “Operating Cost Calculator”. Cycle Therm website. http://www.cycletherm.com/resources/operating-cost-calculator.aspx (Accessed Feb 3, 2021).

[vii] “Calculate Engineering Estimate of Natural Gas Usage and Greenhouse Gas Generation”. Captis Aire website. https://www.captisaire.com/Value-Calculator/ (Accessed Feb 3, 2021).

[viii] “Greenhouse Gases Equivalencies Calculator - Calculations and References”. EPA website. https://www.epa.gov/energy/greenhouse-gases-equivalencies-calculator-calculations-and-references (Accessed December 28, 2020).

[ix] “Harnessing the Power of the Markets to Improve the Environment”. American Carbon Registry website. https://americancarbonregistry.org/ (Accessed February 3, 2021).

[x] “Scalable greenhouse gas projects to earn real financial returns for your business.” ClimeCo website. https://climeco.com/ (Accessed February 3, 2021).

[xi] “Allowance Price Explorer”. International Carbon Action Partnership website. https://icapcarbonaction.com/en/ets-prices (Accessed Jan 20, 2021).

[xii] Eric Ripley (Director Industrial Programs, American Carbon Registry), in a phone conversation with Kim Tutin November 17, 2020.

[xiii] “Sulfate Turpentine Recovery”. Pulp Chemicals Association. Pages 9-12, 127. https://www.pinechemicals.org/store/viewproduct.aspx?id=1579188 (Accessed Jan 2, 2021).

[xiv] “Price Chart for Gum Turpentine”. PineChem website. http://www.pinechem.net/images/gall/ChartGNE.GIF Accessed Jan 3, 2021).

[xv] “AIR Advanced Industrial Resources”. AIR website. https://airtest1.com/ (Accessed April 16, 2020).

[xvi] “Testing and Modeling”. John Zink Hamworthy Combustion website. https://www.johnzinkhamworthy.com/testing-modeling/ (Accessed Feb 3, 2021).

[xvii] “Electronic Code of Federal Regulations (eCFR)”. eCFR website. See https://www.ecfr.gov/cgi-bin/text-idx?node=sp40.13.63.dddd#ap40.14.63_12292.1 (Accessed April 16, 2020).