SU1455189A1 - Method of determining end time o dryng wood in piles - Google Patents

Abstract

Invention m. B. used in the woodworking industry in the chamber drying of lumber. The purpose of the invention is to improve the accuracy of determining the end of drying. The current value of the shrinkage is measured, the value of the equilibrium shrinkage corresponding to the equilibrium moisture content of the wood at the time of drying is determined. Get the graphic dependence of the shrinkage of wood from its humidity. Additionally, the value of the base humidity is determined. The linear portion of the graphic dependence of the shrinkage of wood on its moisture content to intersect with an axis corresponding to the wood moisture is extrapolated. Using the value of the basis moisture, find the final shrinkage of the grout from the equation (W6-W) / (), where UH is the final shrinkage of the grill, m; Yp — equilibrium shrinkage of the stab, m; We - basic humidity, wt.%; Wp - equilibrium moisture content, wt.%; W - required final moisture content, wt.%. When the wood reaches a moisture content of K, the drying process ends. 2 Il. 1C С /)

Description

one

The invention relates to a drying technique and can be used in the sawmill and woodworking industry and other sectors of the national economy for the chamber drying of lumber on piles.

The purpose of the invention is to increase the accuracy of the determination.

The goal is achieved by the fact that in the method of determining the moment of termination of the wood drying process in piles, including measuring the current value of shrinkage, determining the values of the equilibrium shrinkage corresponding to the equilibrium moisture of the wood, and the final shrinkage corresponding to the final moisture of the wood by the end of drying, as well as obtaining a graphic dependence of the shrinkage of wood on its moisture content, additionally determine the value of the basis moisture by extrapolating the linear portion of the graphic depends The shrinkage of wood from its moisture content to the intersection with the axis corresponds to 15

moisture content of the wood and, using the value of the basis moisture, find the final shrinkage of the shtab of the following equation

ten

15

u wg-wn

(I

where Y is the final shrinkage of the stub, m;

YP - equilibrium shrinkage piles, m; We - basic humidity, wt.%; WP- equilibrium humidity, May. %; WK - required final moisture

wt.%

FIG. Figure 1 shows the characteristic dependence of wood shrinkage on its moisture; in fig. 2 is a graphical solution to equation (1).

The method for determining the end of the drying process in piles is carried out as follows.

The wood is dried in a batch or continuous chamber. On merit

SP

00 with

The first stage of drying (for intermittent chambers after switching to the last phase of the drying mode, and for continuously operating chambers when moving the stack to the dry end of the chamber), it is necessary to determine the end of the drying process in order to avoid unnecessary energy costs. At the same time, the parameters of the drying mode (temperature by dry and wet thermometers) are kept constant (i.e., Wp const). The curve of change of head, its shrinkage in time is described by an exponential dependence. At the final stage of drying, information on the change in the shrinkage value is obtained from shrinkage sensors at equal intervals of time — Im Dt. Then you can write the following system of equations to determine the current shrinkage values

U1 Ur-U-, Uz Ur „-аТ,

-Y-e -Y-e (2)

 Solving the system of equations (2), an expression is obtained to determine the value of the equilibrium shrinkage of Ur, corresponding to the equilibrium moisture at the final stage

: drying

V.

 P 1 g I l / G /

(3)

, + Uz-2U2 When drying a stack of woods, a non-linear relationship is obtained between the current shrinkage of the wood and UV. from the average (by: samples) moisture at these shrinkage values of W, W2 and Ws, which is shown in FIG. one.

I The non-linear dependence (be) section characterizes the removal of free moisture and a small amount of adsorption moisture. In section (ab), adsorption moisture is removed, which is characterized by the linear range of the indicated dependence. Extrapolating the plot (ab) to the intersection with an axis corresponding to the moisture content of the wood determines the value of the basis moisture. Studies show that the value of the base moisture is almost independent of the thickness of the lumber and its

five

the value for softwood averages 25% by weight.

Using the obtained value of the base moisture in equation (1), which describes the linear portion of the dependence of wood shrinkage on its moisture, the value of Y is determined, upon reaching which the drying process should be terminated.

In cases where a slight variation in the moisture content of the dried material is allowed, points with the coordinates of Ur, O, Wg can be used as reference points (Fig. 2). The value of Wg is taken equal to 25 wt.%. In the event that more precise control is required for the condition of the wood, the value of the basis moisture should be determined as specified for the particular controlled batch of lumber.

Claims (1)

Invention Formula 0 The method of determining the moment of the end of the process of the wood substance in the beads, including the measurement of the current value of the shrinkage, the determination of the values of the equilibrium 5 shrinkage, corresponding to the equilibrium moisture content of the wood and final shrinkage, corresponding to the final moisture content of the wood at the time of the end of drying, as well as obtaining a graphic dependence of the shrinkage of wood from its moisture content, characterized by 30 that, in order to improve the accuracy of the determination, the value of the basis moisture is additionally determined by extrapolating the linear portion of the graphical dependence of the shrinkage of wood from its moisture content to the intersection with the axis corresponding to the moisture content of 35 wood and using the value of the base moisture to find the final shrinkage of the stack from the following equations wg -wp Rde Y - final shrinkage piles, m; Ur equilibrium shrinkage piles, m; Wf - basic humidity, wt.%; VJ / P - equilibrium moisture content, wt.%; j7 required final moisture content, wt.%. 40 U /, 1l I C l /% pass FIG. /