RU1768899C - Drying process control method - Google Patents

Description

The invention relates to a drying technique and can be used to dry objects sensitive to humidity of a heat carrier, for example, microorganisms.

Known methods for automatically controlling the drying of wet materials when changing various technological parameters of the process, for example, when changing the temperature of the product and coolant, their humidity and costs. Thus, for example, to obtain a product of a certain final humidity, the temperature of the coolant at the outlet of the apparatus is maintained linearly depending on its inlet temperature.

However, this method cannot be applied during drying with recirculation of the coolant, when stabilization of its moisture is necessary when obtaining a product of a certain final moisture content. it does not maintain the temperature of the drying agent in this relationship.

There is also known a method for automatically controlling the drying process when the feed of the starting material and the heat carrier changes by the signal of the final moisture of the material and by the signal additionally introduced into the selectivity block by the air temperature at the outlet of the dryer. This control method allows approaching the desired moisture content of the finished product.

Of the known methods, the closest in technical essence to the invention is a method for automatically controlling the drying process of materials in suspension (3). According to this method, the drying process is controlled by stabilizing the temperature regime by affecting the flow rate of the material by the flow rate of the heat carrier and its humidity at the inlet and outlet from the drying volume.

However, this method does not provide stable drying of the object to a predetermined humidity due to the inconsistency of humidity

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a working agent in the drying chamber required for drying certain products, e.g. bacterial fertilizers, microorganisms.

The aim of the invention is to increase the stability of drying the product to a predetermined humidity with recirculation of the coolant.

This goal is achieved by the fact that in a method of regulating the drying process, including stabilizing the temperature of the coolant supplied to the drying and measuring the humidity and flow rate of the primary coolant, measure the humidity and flow rate of the recirculated coolant and the mixture of primary and recirculated coolant, and measure the flow rate of the primary coolant :

/ V (di - dCM) 1 do -f di -2 dcM

change the flow rate of the recirculated coolant, subject to the dependence:

 Vi (di -de) do - dcM

where Vi, V2, V-flow rate of the primary, recycled coolant and mixtures thereof;

d0, di, dew - humidity of the primary, recycled coolants and their mixtures.

In FIG. Figure 1 is a flow diagram of a method for controlling the drying of wet materials.

The apparatus for carrying out the invention comprises lines 1, 2 for supplying primary and recirculated heat carrier to the dryer 3, respectively, and a line 4 for exhausting waste heat carrier with a fan 5, lines 6, 7 for supplying the initial and output of the finished product, respectively.

The automatic control system includes a temperature control loop of the coolant in the dryer and flow control loops of the primary and recycled coolants.

The temperature of the mixture of primary and recirculated coolants at the inlet to the dryer 3 is measured by a sensor 8 and stabilized at a predetermined level by a temperature controller 9.

The flow control circuits of the primary, recirculated coolants and their mixtures contain flow meters 10, 11, 12, humidity sensors 13, 14, 15 of the primary, recirculated coolants and their mixtures, respectively, control unit 16, actuators 17 and 18.

A method for controlling the drying process is carried out as follows.

The primary coolant through line 1 is fed to dryer 3, where the product is dehydrated. In circuit 2, part of the waste coolant is returned to the inlet of dryer 3 by fan 5, and part is discharged along circuit 4, Wet material is fed into dryer 3 via line 6, and the heat-treated product is discharged through line 7.

According to the temperature value measured by the sensor 8, the temperature controller 9 maintains the temperature of the mixture of primary and recycled heat carriers at a predetermined level, which ensures drying of a certain product.

The constant velocity of the coolants in the drying chamber 3 is obtained by controlling the flow rate of the primary and recycled coolants. For this, flow meters 10, 11, 12 and humidity sensors 13, 14, 15 measure the flow rates and humidity of the primary, recirculated heat transfer fluids and their mixture. The signals received by the sensors are fed to a control unit 16, which analyzes the equations for the flow rates of the primary and recycled fluids. The latter are for the primary coolant:

V (di-dcM) do + di -2 dcM

and for recirculated fluid:

V Vi (di -dCM) do - dcM

where Vi, Va is the flow rate of the primary and recycled coolants;

do, di, dcM - moisture content of the primary, recycled coolants and their mixtures;

V Vi + V2 - flow rate through the drying chamber.

If the values of the values measured by these sensors do not satisfy these equations, a control signal is generated by the control unit 16.

depending on the size of the mismatch and fed to the actuators 17 and 18, regulating the flow of primary and recycled coolants. As a result, their flow rate changes until the equations that determine the primary and recirculated heat carrier flows depending on the set flow rate of the heat carrier in the dryer 3 and its moisture content are satisfied.

This method of controlling the drying process is expediently applied with a high initial moisture content of the coolant in the dryer. In this case, as a moisture sensor,

serve as wire resistances. By changing the resistance of the latter, one can judge the moisture of the coolant, which makes it possible to simplify the measurement of moisture content and control the flow rate of the coolant.

When using this method, a certain water content of the heat carrier is created in the working area. The latter circumstance makes it possible, if the coolant is constant, to carry out the dehydration process under stationary conditions, ensuring the maximum possible preservation of the native properties of the material, which are predominantly affected by the concentration of moisture. Using a part of the spent heat carrier to create a certain humidity in the drying volume with this method requires less heat: energy to heat it to a certain temperature, determined by the conditions of the drying process of a particular product. The automatic maintenance of the temperature and moisture content of the coolant at a given level at a constant speed in the working volume of the drying apparatus makes it possible to increase the stability of a given humidity of the finished product, which is especially necessary.

Claims (1)

long-term storage of many products, such as bacterial fertilizers. SUMMARY OF THE INVENTION A method for controlling a drying process, including stabilizing the temperature of a heat transfer fluid for drying and measuring the humidity and flow rate of a primary heat transfer fluid, characterized in that, in order to increase the stability of the drying of the product to a predetermined humidity with recirculation of the heat transfer fluid, humidity and flow rate are measured respectively - curable heat carrier and mixtures of primary and recirculated coolant, change the flow rate of the primary coolant, subject to the dependence v V (ch-dcM) 1do + di -2 dcM change the flow rate of the recirculated coolant, subject to the dependence v Vi (di-dcM) 2cio-dcM where Vi, Va and V are the flow rate of the primary and recycled coolants and their mixtures; d0, di and bcm - the humidity of the primary and recycled coolants and their mixtures.