Wood drying methods pdf

Suny esf wood products syracuse, ny moisture content. United states department of drying firewood in a temporary. Rapid drying methods are potentially low cost drying methods and the conveniences inherent in short drying periods provide additional attractions. Most food dehydrators have an electric element for heat and a fan and vents for air circulation. Sundrying because sundrying takes more time, pretreating the produce by. This abnormal wood is called reaction wood, and it can cause a number of unpredictable warping problems during drying. The amount of water contained in the wood, usually expressed as a percentage of the weight of the ovendry wood. Dehydration has been used widely for this purpose since ancient times. But, doing it yourself does require time, effort, knowhow, and the room for. Wisconsin oven offers costeffective conveyorized wood drying ovens that provide high performance and reliable operation for drying primer, sealer and finish coatings on wood and cement board trim and panels. Boiling drying time reduced an average of 50% over airdrying.

The following discussion will break this title down to what it really means and provide a context for the thesis. Wood is airdried or dried in a purpose built oven kiln. Degrade includes splits, checks, warp, discoloration, and any other change in wood that lowers the woods usefulness and therefore its value. In fact, kiln drying on some hardwood species can take up to and beyond a month, depending on the initial mc of the wood. Timber is a name given to wood that has been prepared for the purpose of building or carpentry robinson and davidson, 1999. Before adopting a dry ing procedure to control specific drying defects, the kiln operator should determine whether the procedure will induce other defects that may lower the value of the lumber. Seasoning is the process of removing the moisture content from wood to minimize structural. How to build and use a vacuum kiln for drying wood. Freshly cut wood retains a lot of water, which makes lighting and sustaining a fire very difficult. Over four hundred types of dryers have been reported in the. Processing methods for production of solid wood products from plantationgrown. An oven thermometer placed near the food gives an accurate reading of the drying temperature. Because certain wood species will rot before air drying can be completed in some climates, wood is artificially conditioned by one of three primary methods. The drying of foods is hugely important technique for the food industry and offers possibilities for ingredient development and novel products to consumers.

Vacuum drying is not a new technology, and its use for drying wood has been suggested since the early 1900s. When the air is more humid, wood absorbs water from the air. This fact sheet summarizes the basics of kiln drying wood, the most commonly used methods, drying schedules and some drying defects. Seasoning of timber and drying of wood types and methods. Fooddrying techniques by carol costenbader contents drying food. An explanation of the basics of kiln drying wood, a list of the most commonly used methods and drying schedules and defects. The object is to reduce the moisture content of your wood to the relative content of the climate where the wood will reside, while trying to keep the lumber from distorting, checking, honeycombing, etc. Section 4 chapter 1 fundamentals sahand university of. Different ways of seasoning wood home guides sf gate. This process is often used as a final production step before selling or packaging products.

Wood handbookchapter 12drying and control of moisture. These include two ovendry methods, a distillation, and what the standard calls other methods. The traditional method for drying wood, air seasoning is also the longest, taking six to nine months. Dry wood below 22% mc will not decay, mold, mildew, or stain. Than than htike3 abstract veneer drying is an important process in manufacturing of plywood and laminated veneer. Ovendrya term applied to wood dried to constant weight in an oven maintained at temperatures of from 214 to 221f.

Wood drying also seasoning lumber or wood seasoning reduces the moisture content of wood before its use. To air season wood, stack logs or planks outside on. Drying is a mass transfer process consisting of the removal of water or another solvent by evaporation from a solid, semisolid or liquid. Various drying methods such as freeze drying fd, sun drying sd, vacuum oven drying vod and conventional oven drying cod are common methods in. Many woodworkers prefer airdried stock to the kilndried variety because they say it works easier and offers truer color.

Seasoning of timber or drying of wood wood drying also seasoning lumber or wood seasoning reduces the moisture content of wood before its use. The first part of the water when the wood is at high moisture content is lost rapidly and even a few days of summer air drying can reduce kiln cycle time. Drying, therefore, eliminates, or reduces to a minimal level, a major source of frustration that a consumer has with wood shrinkage and swelling. Equilibrium moisture content wood is a hygroscopic substance. Several special drying methods, such as solar drying, are described, and proper techniques for storing dried lumber are discussed. Sun drying is not recommended in minnesota due to our high humidity and cool night temperatures. Correct drying, handling, and storage of wood will minimize moisture content changes that might occur after drying when the wood is in service and such changes are undesirable. Drying freshly cut wood is essential for good quality lumber and woodworking. Pdf on jul 22, 2014, patrick perre and others published 36 drying of wood. As a potentially cheap and safe drying process for largescale production of aerogels, this method has received considerable attention from industry. The appropriate drying technique depends on size and species. The title of this thesis is efficient kiln drying of quality softwood timber.

Ways of decreasing a sawmills energy expenses related to wood drying were also investigated in. Leave the oven door propped open 24 inches and place a fan near the outside of the oven door to improve air circulation. Drying is perhaps the oldest, most common and most diverse of chemical engineering unit operations. Wood that has been growing at a slant doesnt have uniform growth ring spacing and varies from the topside to the underside. Methods of wood drying by daniel yourdon over the past year i have been gathering information on various methods of wood drying. The secondary methods b through d are intended for special purposes or under circumstances where the primary procedure method a is not desired or justified. With condensers, the eciency can be further increased. An introduction to the drying food preservation method the. This article is an attempt to consolidate that information. Need further processing generally by air, freeze, or vacuumdrying methods to obtain a shelfstable product, or the dehydration process could be used as a pretreatment for canning, freezing, and minimal processing. Importance of thickness variation in kiln drying red oak lumber pdf. The wood drying ovens utilize a chain conveyor system and highvelocity convection air technology to efficiently dry the boards.

Pdf conventional kiln and vacuum drying are commonly used in industry to dry wood. This type of kiln could be used in drying firewood, but the cost is too high to. This report can also be viewed on the fwpa website. Woodworking when wood is used as a construction material, whether as a structural support in a building or in. After the drying process, both the green beans and the mushrooms must be heated in a 175f oven for 30 minutes to destroy insect eggs. Several special drying methods, such as solar drying, are. Drying times can vary significantly depending upon wood species, initial moisture level, lumber thickness, density, ambient conditions, and processing techniques. This dehydration process generally does not produce a product of low moisture content that can be considered shelf stable. By daniel yourdon over the past year i have been gathering information on various methods of wood drying. Degrade includes splits, checks, warp, discoloration, and any other change in wood that lowers the wood s usefulness and therefore its value.

Air and sheddrying lumber oregon wood innovation center. Any system that would accelerate drying to permit burning of dry wood the same year it is cut would be useful. Fundamental aspects of kiln drying lumber oklahoma state. In these procedures, moisture content values cannot be reported with an accuracy greater than integer percentage values that is, lower than in method a. To be considered dried, the final product must be solid, in the form of a continuous sheet e. An introduction to the drying food preservation method. Boiling drying time reduced an average of 50% over air drying.

Direct methods are mainly devoted to research purposes because it requires special equipment e. Sundrying because sundrying takes more time, pretreating the produce by blanching or another method is much more important. Various methods for measuring the moisture content of wood are described by the american society for testing and materials in publication astm d4442. The drying is carried out at ambient pressure preferably using reduced or elevated pressures. In this paper, we define vacuumdrying methods in four groups. Drying inhibits the growth of bacteria, yeasts, and mold through the removal of water. Often degrade losses exceed all other operating costs in. Produce the best quality product as compared to other methods of drying. In the solid wood products industry, we most often define moisture content on a dry basis. The boulton process usually is performed in the same cylinder used to treat the wood.

In this paper, we define vacuum drying methods in four groups. Drying is also a frequently used pretreatment in wood gasification, or for processing wood into briquettes, pellets, panels and similar products. Wood is always trying to come into equilibrium with the air surrounding it, so its moisture content can change somewhat after its been dried. The amount of moisture in wood is ordinarily expressed as a percentage of the weight of the wood when ovendry.

To air season wood, stack logs or planks outside on pallets in such a manner that air can. Dont confuse with simple freezing, a common first step in emergency response that allows time to. Dont confuse with simple freezing, a common first step in emergency response that allows time to arrange drying by any of the processes. Two solar kilns for drying lumber have been operated in alaska northern engineer 1982. Wood drying reduces the moisture content of wood before its use.

Chapter 8 drying defects forest products laboratory. Freeze drying or lyophilization is a drying method where the solvent is frozen prior to drying and is then sublimed, i. Various drying methods such as freeze drying fd, sun drying sd, vacuum oven drying vod and conventional oven drying cod are common methods in industry and have been applied for the pigment. If moisture content is controlled within reasonable limits by such methods, major problems from dimensional changes can usually be avoided.

Simulation of moisture transfer during wood vacuum drying. Often, wood must be in equilibrium with the air air drying timber stack outside, as for construction wood, or the air indoors, as wood drying also seasoning lumber or wood season for wooden furniture. A detailed reference of interest for engineers and energy specialists working in the process industry field, drying in the process industry investigates the current state of the art of todays industrial drying practices, examines the factors influencing. Seasoning is the process of removing the moisture content from wood to minimize structural problems when used in. Direct methods are considered to provide true measurements of moisture content, and are used to calibrate more practical and faster indirect methods. Pdf understanding effects of drying methods on wood mechanical. Resulting high calorific wood fuel helps clients reduce their reliance on fossil fuels. Technologies for vacuum drying of wood can be classified by the heating method used.

Quality control of moisture determination of moisture content. This manual also includes predrying treatments that, when part of an overall qualityoriented drying system, reduce defects and improve drying quality, especially of oak lumber. In softwoods, reaction wood forms on the underside of a branch or trunk, and is called compression wood. Butale published on 201905 download full article with reference data and citations. Vacuum drying of woodstate of the art springerlink. Drying woodchips increases the combustion value for use in biomass boilers and lowers storage costs. As the wood becomes drier, additional energy is needed to release moisture from the hydroscopic. A great deal of scientific knowledge is not necessary to dry wood.

However, some wood species will rot before the air drying is complete. Air drying your own stock can save you at least 50 percent over kilndried boards from your lumber retailer. It has the ability to take in or give off moisture in the form of vapour. Air drying, steam treatment and drying, microwave drying, ambient pressure drying, vacuum drying, and solar drying has all been historically utilized to obtain highquality wood product. Suggestions are provided for ways to economize on drying costs by reducing drying time and energy demands when.

Condition the produce see postdrying methods, page 9 and then store in a cool, dry place for up to six months. Air drying of lumber forest products laboratory forest service. Two of thesethe ovendrying and the electrical methodsare described in this chapter. In order to maximize woods value and strength, mills invest both time and money in the kiln drying processes to remove excess moisture from the lumber stack. Than than htike3 abstract veneer drying is an important process in manufacturing of plywood and laminated veneer lumber. Dec 14, 2018 the traditional method for drying wood, air seasoning is also the longest, taking six to nine months. Modeling drying time during veneer drying and comparison with. The drying food preservation method is easy to do, very safe, and can be used for most types of foods meats, fruits, and vegetables.

Processing methods for production of solid wood products. When the drying is done in a kiln, the product is known as kilndried timber or lumber, whereas air drying is the more traditional method. Airdrying your own stock can save you at least 50 percent over kilndried boards from your lumber retailer. Wood drying methods if the major objective of drying lumber is to make money, then the lumber must be dried with minimal development of degrade. Aug 15, 2016 understanding differences between vacuum freeze drying, conventional freezing, and other drying methods vacuumfreeze drying sometimes called freeze drying, though technically that is a different, less successful freezing process without use of a vacuum. Allowing lumber to passively sit at a given humidity level in order to obtain a desired emc airdrying may be the simplest and least expensive method of seasoning wood, but it is also the very slowest. Researchers have found that microwave finish drying speeds up the otherwise very low drying rate at the end of the classical drying methods. It is also called seasoning and reduces the moisture content so that the wood is stable enough to use.

Modeling drying time during veneer drying and comparison. Unfortunately, some of the methods proposed are not cheaper. Principles and practices of drying lumber wood, concrete. Food drying is a method of food preservation in which food is dried dehydrated or desiccated. High temperatures reduce the strength of wood in two ways. When wood is used as a construction material, whether as. Methods of accelerating the drying of wood have always been the subject of keen interest by the wood industries. Drying hardwood lumber focuses on common methods for drying lumber of different thickness, with minimal drying defects, for high quality applications. Understanding differences between vacuum freeze drying, conventional freezing, and other drying methods vacuumfreezedrying sometimes called freezedrying, though technically that is a different, less successful freezing process without use of a vacuum. Among the available methods, vacuum drying is an interesting alternative which yields dry wood rapidly under low temperature and pressure conditions 9.

In this study, an attempt was made to develop a better. For example, douglasfir on the west side can be air dried to 20% moisture content in two to three weeks in july and august compared to several months in the winter. Brown em 8612e reprinted october 2007 the process of drying wood is the same for air and kilndrying, but in kilndrying you have much greater control over air velocity, temperature, and humidity. General information on drying the environment and wet materials many criteria affect the choice of a drying method during recovery efforts. Modeling drying time during veneer drying and comparison with experimental study ms. Is there a topic for which you would like to see a tip. Processing methods for production of solid wood products from. Particular emphasis is placed on wood and log characteristics that affect veneer production. Two of the easiest and most common that can be used in any climate are oven drying and drying with an electric dehydrator appliance. A comprehensive approach to selecting and understanding drying equipment for chemical and mechanical engineers. National archives and records administration preservation programs the information provided below is intended for emergency recovery and response, not general treatment recommendations.

Wood drying 1 wood drying wood drying also seasoning lumber or wood seasoning refers to reducing the moisture content of wood prior to its use. In order to understand and to improve the veneer drying, a mathematical model was developed. In this process, the cylinder is charged with wood, and heated preservative is used to heat the wood charge for 1 to 24 hours. Finally, the preservative is returned to the work tank. Need further processing generally by air, freeze, or vacuum drying methods to obtain a shelfstable product, or the dehydration process could be used as a pretreatment for canning, freezing, and minimal processing. Another common drying method in aerogel production is known as ambientpressure drying apd. Dry wood has little or no likelihood of developing new cracks, checks, or splits. In dry air, the wood gives up water to the air until it is dried, as it equalizes with the air.