Location: Quality & Safety Assessment ResearchTitle: Portable six-port reflectometer for determining moisture content of biomass material Author
|Julrat, Sakol - OAK RIDGE INSTITUTE FOR SCIENCE AND EDUCATION (ORISE)|
Submitted to: IEEE Sensors Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2017
Publication Date: 7/13/2017
Citation: Julrat, S., Trabelsi, S. 2017. Portable six-port reflectometer for determining moisture content of biomass material. IEEE Sensors Journal. 17(15):4814-4819.
Interpretive Summary: Biomass materials are a class of plant products that can be utilized as an alternative source of energy. Often they are combustible materials that are byproducts of other agricultural production operations. Sawdust from the milling of timber into lumber and associated products is one example. Sawdust can be pelletized for economy in transporting it to points of consumption. The moisture content of such products is important in the binding of the materials during pelleting and when preparing the pellets for combustion. It is also is important when materials need to be stored without deterioration in quality. Therefore, techniques for reliably and rapidly measuring moisture content are needed for use in the industry. Microwave sensing techniques are useful in sensing the moisture content in such materials, because the dielectric properties of the materials are highly correlated with moisture content. This paper describes experimental work in developing new low-cost microwave sensing devices and techniques that may be useful in monitoring moisture content of such biomaterials. Open-ended waveguide sensors can be used for measurement of the dielectric properties of materials placed on these sensors or passing over them. Microwave network analyzers that have been used for these measurements are very expensive and lack portability, so a low-cost portable moisture sensor for moisture determination in biomass materials was developed. The sensor, operating at 5.13 GHz, is based on a six-port reflectometer (SPR) with an open-ended half mode substrate-integrated waveguide (HMSIW). The dielectric properties of biomass material (sawdust) was determined by using two different calibration techniques. The measured dielectric constant and dielectric loss factor were used for the development of a density-independent algorithm for determining the moisture content of sawdust at different bulk densities. Predicted results for moisture contents ranging from 6% to 36% for sawdust at room temperature agreed well with moisture contents determined by the standard oven-drying method, with a standard error of performance of 0.967, where 1.0 is perfect agreement. The proposed measurement technique is suitable for rapid and nondestructive determination of moisture content in biomass materials. The development of this type of moisture sensor would benefit those in the biomass industry and consumers as well eventually.
Technical Abstract: A portable six-port reflectometer (SPR) for determining moisture content of biomass material is proposed for the first time in this paper. The proposed system consists of a 5.13 GHz reflectometer used with an open-ended half-mode substrateintegrated waveguide (HMSIW) sensor. The complex permittivity of biomass (sawdust) was measured, and a dielectricproperties-based algorithm for moisture determination was developed. The reflectometer performance was verified by comparing the measured complex permittivity to results obtained with a commercial automatic network analyzer. Finally, the predicted moisture content was compared with the standard oven drying method.