SU932162A1 - Method of automatic control of drying process of loose materials in straight flow dryer - Google Patents

Description

The invention relates to a drying technique and may find application in the manufacture of particle boards for the automation of drying processes of wood chips in dryers with direct-flow movement of the material and the drying agent.

A known method for automatically controlling the drying process of bulk materials in a direct-flow dryer by changing the ratio of fuel-material И‘К

The disadvantage of this method is that it requires a constant amount of supplied chips, fractional composition, wood species and does not allow to stabilize the final moisture content of the chips when the listed parameters fluctuate during the drying process.

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

This goal is achieved by the fact that they additionally determine the equilibrium moisture content of the material, measure the temperature difference between the drying agent and the material at the outlet ⁵ of the dryer, summarize the received signals and act on the change in the fuel-material ratio by the total signal.

¹⁰ The drawing shows a diagram that implements the proposed method.

The circuit contains a dryer 1, functional 2 connected to a scaling unit 3, the output of which is connected to a scaling unit 4, a summing unit 5, the inputs of which are connected to functional 2 and a 2D unit 4, and the output to a comparing unit 6, the input of which is connected to the master '7, and the output is to the ratio regulator 8, connected to the actuator I · 9 ·

Equilibrium humidity can be measured indirectly using one of the following relationships:

(1) (2) (3) (4) where the relative humidity of the drying agent at the outlet of the dryer;

drying agent temperature at the outlet of the dryer;

wet agent drying agent temperature;

temperature of the drying agent at the inlet of the dryer.

Changing the equilibrium humidity in the drawing is carried out according to the dependence of the expressions (1-4).

For this, the temperature of the drying agent (t ^ and tg) is measured at the inlet and outlet of the drying apparatus 1. The received signals are fed to functional 2, which converts them into a signal proportional to the equilibrium moisture content of the wood at the outlet of the drying apparatus.

The functional conversion of 2 signals and tg is carried out according to the formula obtained on the basis of mathematical analysis of the known diagrams of the equilibrium moisture content of wood, dried by heating with natural gas combustion products! 4 by the signal of the setter 7. The unbalance signal is supplied to the regulator 8, which controls the actuator 9.

Since the signal arriving at the control device is obtained by algebraically adding signals from three temperature sensors taking into account the sign and scale, the entire device (outlined in dashed lines) is a conventional adder with three inputs, which allows algebraic summation of the signals in the required proportions.

Using the proposed method in the production of particle boards allows you to stabilize the specified final moisture content of the chips, which leads to an improvement in the quality of the plates, reducing fuel consumption for drying, as well as a binder for the manufacture of plates. According to VNIIDMASH studies, as a result of stabilization of the final moisture content of the chips, the current costs in the production of chipboard are reduced by 0.8-1.0 rubles. per 1 ton of dried chips.

Implementation of the proposed method in a chipboard workshop with a capacity of 100 thousand m ^ plates per year with an average consumption of dried 'chips of 0.75 t / m * 3 will give an economic effect by reducing the cost of plates

W_ = 0.004 t <- 0.157 t ₂ + 17.3 (5) g

The specified linear relationship provides the determination of equilibrium humidity with an accuracy of ± 0.5% in the range of the final humidity 3 ^_ 8%, which is necessary in the production of chipboards.

For other bulk materials, formula (5) will have other coefficients, the values of which can be obtained from the analysis of the corresponding equilibrium moisture diagrams of these materials.

A signal proportional to the temperature difference (k & t) is obtained by directly measuring the temperature of the drying agent (tg.) And material (tg), followed by comparison and scaling.

The received signals 17 p and k ^ t are added in block 5 and compared in the block55

0.8 * 0.75-100000 = 60 thousand rubles / year

Claims (1)

3 Equilibrium humidity can be measured indirectly using one of the following dependencies: WP f, (t2, tj Wp f, (t2, t,); p). where Cpn is the relative humidity of the drying agent at the outlet of dryers; tn temperature of the drying agent at the Dryer outlet; tj. - the temperature of the drying agent to the wet thermometer; t is the temperature of the drying agent at the dryer inlet. The change in the equilibrium humidity in the drawing is carried out according to the dependence 2 of the expressions (). To do this, the temperature of the drying agent is measured at the input and output of the drying apparatus 1 (t and the received signals are fed to the functional 2, which converts them into a signal proportional to wood moisture at the outlet of the drying apparatus. Functional 2 transforms the signals t and t into (c by the formula obtained on the basis of the mathematical analysis of the known equilibrium moisture diagrams of wood dried by heating uktami natural gas combustion W 0,00 t, - 0,157 tj + 17.3 This linear relationship provides the definition of equilibrium moisture with an accuracy of iO, 5% in the target humidity range of 3-8, required for the production of chipboard. materials, formula (5) will have other coefficients, the values of which can be obtained from an analysis of the corresponding equilibrium moisture diagrams of these materials. A signal proportional to the temperature difference () is obtained by directly measuring the temperature of the agent with shki (t2) and the material (trf) and then comparing and scaling. . The received Vvp and kut signals are added in block 5 and compared in block 4 and 6 with the setpoint signal 7. The unbalance signal is fed to the controller 8, which controls the actuator 9. As a signal to the control device, it is obtained by algebraically adding signals From the three temperature sensors, taking into account the sign and scale, the entire device (outlined in the diagram by a dotted line) is a conventional adder with three inputs allowing the algebraic summation of signals to be made in the required proportions. The use of the proposed method in the production of chipboard stabilizes the desired final moisture of the chips, which leads to an improvement in the quality indicators of the plates, a reduction in the fuel consumption for drying, as well as a binder for the manufacture of the plates. As the VNIIDMASH research has shown, as a result of stabilization of the final chip moisture, the current costs in chipboard production are reduced by 0.8-1.0 rubles. per 1 ton of dried chips. The implementation of the proposed method in the chipboard workshop with a capacity of 100 thousand m of slabs per year with an average consumption of dried chips of 0.75 t / m3 will give an economic effect by reducing the cost of the plates 0.80.75-100000 60 thousand rubles / year Formula of the invention controlling the drying process of bulk materials in a continuous-flow dryer by changing the ratio of fuel material, characterized in that, to increase the control accuracy, the equilibrium moisture content of the material is additionally determined, the temperature difference of the drying agent is measured and the material at the outlet of the dryer, summarize the received signals and, according to the total signal, affect the change in the fuel-material ratio. Sources of information taken IN attention during the examination 1. USSR author's certificate № 356if31, cl. F 26 V 21/06, 1370.