High-Quality, 400kW Biomass Material Drying with CW RF Power
In 2019 Crescend Technologies was commissioned to design, develop and deploy at a customer site, a 400kW Biomass Material Drying System to be used for large scale biomass drying. The foundation of this system includes eight (8) Crescend PTL-50 Solid State Microwave Generators covering the 902-928 MHz band.
Each of the Crescend PTL-50 (figures 1 and 2) has 80dB of system gain, twenty-two 2.5kW CW RF power modules (SSPA-Blades) combined with a 22-1 radial combiner with 7-16 DIN inputs and WR975 waveguide output, 55% AC-to-RF efficiency at full power output, gain and phase control, water cooling with primary and secondary manifolds and tubing, 480 VAC distribution panel and a system control distributed high-speed multi-processor architecture.
A total of eight of these generators were successfully commissioned to produce 400kW Biomass Material Drying system using CW RF power into a given applicator to dry high-quality biomass material.
The project from concept to design and manufacture, at Crescend’s facility, was achieved in less than 9 months.
Figure 1: Internal view of Crescend PTL-50, 50kW Generator/Amplifier
Figure 2: Internal View 50kW Generator with Liquid Cooled SSPA-Blades (Crescend PTL-50)
Scope of Work: Designing a 400kW Biomass Material Drying System Solution
Scope of work included design, construction, test, delivery and commission of eight (8) 50 kW solid-state RF generators to a customer site to be used for drying hemp as shown below in figures 3 and 4. The Crescend PTL-50 kW generators were combined to create a 400kW Biomass Material Drying System.
Figure 3: Eight (8) 50 kW generators (Crescend PTL-50) combined two each with a “magic tee” installed at customer site in 2019
Figure 4: Eight (8) 50 kW generators (Crescend PTL-50) combined two each with a “magic tee” installed at customer site in 2019
Field Deployment: 400kW Biomass Material Drying System Solution
The large-scale drying plant is located in a remote location in Arizona where thousands of acres of hemp are cultivated for CBD oil production.
The plant is equipped with a 400 cubic foot mixer/dryer with a processing capacity of about 24 tons per day of fresh hemp. The plant is pre-configured for installation of two additional dryers in the future.
After drying, the hemp is pelletized and packed in bulk bags, which are then transported to an extraction facility. See figure 5.
The mixer dryer is installed on a steel mezzanine for easy access and to allow bottom discharge of dried product to a conveyor system as shown in figure 6.
Figure 5: Biomass drying using large scale solid state microwave generators
Figure 6: Industrial Microwave Biomass Drying
A top view of the mixer/dryer, showing the loading port, exhaust duct, and waveguide which delivers microwave power from the generators shown in figure 7. This system is powered by eight Crescend Technologies 50 kW solid state microwave generators. Two 50 kW generators were combined with a “magic tee” to produce 100 kW. These units have extremely high reliability and minimal maintenance, which is especially important at this remote site. See figure 8.
Figure 7: Customer drying tank/applicator with four 100 kW inputs
Figure 8: The combination of eight (8) Crescend PTL-50 high power solid state RF generators installed
Dates of Performance: Designing & Field Commissioning a 400kW Biomass Material Drying System
Start of project March 31, 2019. Dates of performance October 14, 2019 for the prototype demonstrator through January 15 2020 for commissioning on customer site.
Performance Records: 400kW Biomass Material Drying
Per the customer specification, the project was gauged on reducing high quality biomass hemp with a starting moisture level of hemp at 50% to be dried to 10% over set period of time with a 400 kW of power at 902-928 MHz to a given applicator.
The moisture content of the hemp can vary considerably depending on the variety, location, climate, and even the time of day it is harvested. A reasonable average value for estimating is 75%. The density of the hemp determines how much material can be loaded into a given sized mixer/dryer. It is affected by the nature of the hemp (flower/bud/leaf proportion) and how it is cut and chopped. The weight of the hemp itself causes compression which increases loaded density with larger mixer/dryers.
Example Process Rates and Times:
For a given amount of hemp, the drying time will depend on the amount of microwave power available and the moisture content of the hemp. A 2 hour cycle time is generally a good balance between drying speed, moderate drying temperature, and equipment cost. The tables below illustrate performance of various size mixer/dryers configured with sufficient microwave power for 2 and 3 hour drying cycle times. These examples assume flowers and leaves chopped to 10 mm. See figures 9 and 10.
Process Rates and Equipment Size - 2 Hour Cycle Time
Figure 9: Drying from 75% TO 10% Mixer Capacity (cubic feet) 25, 50, 100, 200, 400
Process Rates and Equipment Size - 3 Hour Cycle Time
Figure 10: Drying from 75% TO 10% Mixer Capacity (cubic feet) 25, 50, 100, 200, 400
Drying Profiles: 400kW Biomass Material Drying
Because microwave energy selectively targets water molecules, the temperature of the hemp during drying remains at about 120⁰ F throughout the drying cycle. This is well below the vaporization temperature of essential oils and terpenes, so virtually no loss will occur.
The mixing action of the dryer provides extremely uniform heating without hot spots, so there is no burning or overheating. The hemp retains its natural green color.
The graph below in figure 10 shows the drying cycle of a 200 cubic foot mixer/dryer equipped with 400 kilowatts of microwave power. The specification of moisture content (MC) of 10% was achieved.
Figure 11: Drying cycle of a 200 cubic foot mixer/dryer equipped with 400 kW of microwave power.
Decarboxylation:
Significant conversion of CBD-A to CBD occurs during the microwave drying process. The reason this occurs is not well understood, but it is clearly established by laboratory tests. An additional heating step may be added at the end of the drying cycle to ensure 95%+ decarboxylation. This is a software-controlled option.
Additional Experience:
Crescend has been in business since 1979 and has over 40 years of experience in design, development and manufacture of high-power RF amplifiers. Our core business has been public safety and military applications. Safety, quality and reliability is paramount to Crescend. All products are brought to market with this foundation of rugged, mission critical quality.
Additional previous experience demonstrated in our standard high power, RF amplifiers such as our UHF 250W amplifier, VHF 350W amplifier as well as our PTL 2.5 kW solid state microwave generator.
Datasheet Documents:
Crescend has been in business since 1979 and has over 40 years of experience in design, development and manufacture of high-power RF amplifiers. Our core business has been public safety and military applications. Safety, quality and reliability is paramount to Crescend. All products are brought to market with this foundation of rugged, mission critical quality.
Additional previous experience demonstrated in our standard high power, RF amplifiers such as our UHF 250W amplifier, VHF 350W amplifier as well as our PTL 2.5 kW solid state microwave generator.
Crescend PTL-12.5 Data Sheet
Crescend PTL-50 Data Sheet
Crescend P25 Series 900 MHz Data Sheet
Crescend P25 UHF Data Sheet
Our low band UHF 250 W amplifier
Crescend P35 Series VHF Data Sheet
Our VHF 350 Watts Output Power amplifier
To learn more about how Crescend Technologies can revolutionize your Biomass Drying , contact us for a personalized consultation. Let us help you harness the power of microwave technology to drive efficiency, sustainability, and profitability in your operations.
Follow us on LinkedIn.
