Exploration of membrane-based dehumidification system to improve the energy efficiency of kiln drying processes: Part I Factors that affect moisture removal efficiency


  • Nasim Alikhani University of Maine
  • Ling Li University of Maine
  • Jinwu Wang USDA Forest Service, Forest Products Laboratory
  • Darien Dewar Valparaiso University
  • Mehdi Tajvidi University of Maine


Energy efficiency, Kiln drying processes, Moisture selective membrane, Thermal energy recovery system, Waste thermal energy


Green wood drying through a steam kiln-drying technology is an energy-demanding process. This process consumes a large amount of energy to evaporate water from wood and discharge it to the atmosphere through venting. The thermal energy loss from the venting of dry kilns takes up to 20% of total energy consumed by the whole wood-drying operation because a considerably large amount of thermal energy is stored in the exhaust air. Harvesting and reusing such waster thermal energy wood improve the energy efficiency of kiln-drying process. Advanced moisture-selective membranes have been used to dehydrate humid air or gas steam because of the advantages of low energy requirements, simplicity of operation, and high specificity. However, the application of the membrane in wood-drying processes has not been addressed. Therefore, this study aimed to investigate the feasibility of using a moisture-selective membrane system to dehydrate the warm moist exhaust air to achieve an energy-saving purpose. The membrane material was polydimethylsiloxane (PDMS) with high water vapor permeability. A small membrane-based dehumidification system was constructed to evaluate the effects of four factors (temperature, airflow rate, initial RH, and vacuum pressure) on the efficiency of moisture vapor removal. Statistical analysis in terms of response surface methodology was carried out. The major findings include 1) an increase in the temperature and vacuum pressure caused a significant increase in the efficiency of moisture vapor removal, 2) the initial RH had little influence on the efficiency of moisture vapor removal, 3) increasing the airflow rate had a negative impact on the efficiency of moisture vapor removal, and 4) the regression model can be used to predict the efficiency of moisture vapor removal. This PDMS membrane would be a possible solution for a pre-drying process at relatively low operation temperatures (<45oC), that is dehumidification process.



Author Biographies

Nasim Alikhani, University of Maine

Graduate Research Assistant

School of Forest Resources

Ling Li, University of Maine

Assistant professor of sustainable bioenergy systems

School of Forest Resources

Jinwu Wang, USDA Forest Service, Forest Products Laboratory

Research Forest Products Technologist

Darien Dewar, Valparaiso University

Undergraduate Research Assistant

College of Engineering

Mehdi Tajvidi, University of Maine

Associate Professor of Renewable Nanomaterials

School of Forest Resources


Baker RW (2012) Membrane technology and applications. Germany: John Wiley & Sons.

Bergmair D, Metz SJ, de Lange HC, van Steenhoven AA (2012) Modeling of a water vapor selective membrane unit to increase the energy efficiency of humidity harvesting. Journal of Physics: Conference Serie 395(1):012161.

Bezerra MA, Santelli RE, Oliveira EP, Villar LS, Escaleira LA (2008) Response surface methodology (RSM) as a tool for optimization in analytical chemistry. Talanta 76(5): 965-977.

Blume I, Schwering P, Mulder M, Smolders C (1991) Vapour sorption and permeation properties of poly (dimethylsiloxane) films. J Membr Sci 61:85-97.

Chadderton D (1997) Air conditioning: A practical introduction. United Kingdom: E & FN Spon.

Donnelly P (1984) Design and analysis of experiments, in Amer Soc Quality Control-ASQC, ASQC membership manager 611. E. Wisconsin, Montgomery, DC.

Elustondo DM, Oliveira L, Lister P (2009) Temperature drop sensor for monitoring kiln drying of lumber. Holzforschung 63(3):334-339.

Field HL, Long JM (2018) Heating, ventilation, and air conditioning. Pages 333-358 in Introduction to agricultural engineering technology. Germany: Springer International Publishing.

Garrahan P (2008) Drying spruce-pine-fir lumber. By FPInnovations for natural resources Canada. Special publication-SP-527E. 167 pp.

Jia L, Xu X, Zhang H, Xu J (1996) Sulfonation of polyetherether ketone and its effects on permeation behavior to nitrogen and water vapor. J Appl Polym Sci 60(8): 1231-1237.

Jia L, Xu X, Zhang H, Xu J (1997) Permeation of nitrogen and water vapor through sulfonated polyetherethersulfone membrane. J Polym Sci B Polym Phys 35(13):2133-2140.

Kneifel K, Nowak S, Albrecht W, Hilke R, Just R, Peinemann K-V (2006) Hollow fiber membrane contactor for air humidity control: Modules and membranes. J Membr Sci 276(1-2):241-251.

Liang CZ, Chung T-S (2018) Robust thin film composite PDMS/PAN hollow fiber membranes for water vapor removal from humid air and gases. Separ Purif Tech 202: 345-356.

Metz S, Van De Ven W, Mulder M, Wessling M (2005) Mixed gas water vapor/N2 transport in poly (ethylene oxide) poly (butylene terephthalate) block copolymers. J Membr Sci 266(1-2):51-61.

Montoya, JP (2010) Using hollow fiber membranes to separate gases from liquid and gaseous streams. Pages 1-7 in Membrane gas exchange.

Mulder M (1996) Preparation of synthetic membranes. Pages 71-156 in Basic principles of membrane technology. Netherlands: Springer Netherlands. https://doi.org/ 10.1007/978-94-009-1766-8_3.

Park CD, Hyung CH, Kim KH, Choi WK, Park YS, Lee HK (2013) Study on the removal of water vapor using PEI/ PEBAX composite hollow fiber membrane. Membr J 23(2):119-128 [in Korean].

Phillip WA, Rzayev J, Hillmyer MA, Cussler E (2006) Gas and water liquid transport through nanoporous block copolymer membranes. J Membr Sci 286(1-2):144-152

IBM SPSS Statistics for Windows, version 26.0 I Spss. 2019. New York, NY: IBM Corp.

Saldaña-Robles A, Guerra-Sanchez R, Maldonado-Rubio MI, Peralta-Hernandez JM (2014) Optimization of the operating parameters using RSM for the Fenton oxidation process and adsorption on vegetal carbon of MO solutions. J Ind Eng Chem 20(3):848-857.

Sijbesma H, Nymeijer K, van Marwijk R, Heijboer R, Potreck J, Wessling M (2008) Flue gas dehydration using polymer membranes. J Membr Sci 313(1-2):263-276.

Simpson WT (1991) Dry kiln operator’s manual. United States: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory.

Vildozo D, Ferronato C, Sleiman M, Chovelon J-M (2010) Photocatalytic treatment of indoor air: Optimization of 2- propanol removal using a response surface methodology (RSM). Appl Catal B 94(3-4):303-310.

Wai Lin S, Valera Lamas S (2011) Air dehydration by permeation through dimethylpolysiloxane/polysulfone membrane. J Mex Chem Soc 55(1):42-50.

Wang KL, McCray SH, Newbold DD, Cussler E (1992) Hollow fiber air drying. J Membr Sci 72(3):231-244.

Yang B, Yuan W, Gao F, Guo B (2015) A review of membrane-based air dehumidification. Indoor Built En- viron 24(1):11-26.

Zhao B, Peng N, Liang C, Yong W, Chung T-S (2015) Hollow fiber membrane dehumidification device for air conditioning system. Membranes 5(4):722-738.





Research Contributions