SU1132125A1 - Method of drying highly wet materials - Google Patents

Abstract

THE METHOD OF DRYING HIGHLY WONDER MATERIALS by moving them and blowing a gaseous coolant stream in two stages, between which partial exhaust coolant is taken, characterized in that, in order to improve the quality of the process at the presence of sheet hydrophobized materials and preserve their water-repellent properties, at the beginning. lead with a coolant with a temperature that is 180-210 ° C higher than the degradation temperature of the water-repellent agent, and a partial removal of the spent coolant is carried out in thinning 60-70% of the total amount, the heat medium in the second stage the temperature is reduced with a rate 4-5 ° C for percent moisture and a removable end hydrophobizator it when the temperature of the onset of degradation (A, followed by removing the remaining heat medium.

Description

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The invention relates to the field of drying, with the circulation of the coolant over the surface, mainly high-moisture thermally insulating water-repellent materials, and can be used in the production of building, heat and sound insulating materials with water-repellent (hydrophobic) properties.

The known method of drying gypsum products by their stepwise heating in the flow of coolant and isothermal exposure, while in the first stage, the product is heated when they are shifted in a direct flow with coolant to 40-50 ° C and humidity 23-27 / 0, in the second stage heating lead in countercurrent with a coolant up to 75-80 ° C and a humidity of 15-17%, and isothermal exposure is carried out after both stages of heating until the products have a moisture content of 10-12% while being blown off with a coolant flow stream, after which the products are cooled in countercurrent, cooling agent ntom 1.

The disadvantage of this method is its unsuitability for drying high-moisture sheet hydrophobized materials.

The known method of drying sheet high-moisture materials, mainly basalt heat insulating cardboard, by blowing the surface of the material with a normally directed coolant gas, while the combustion gas using temperatures above the heat resistance of the material is 700-720 ° C as the gaseous heat transfer fluid heat carrier temperature equal to 2.5 ° С per percent of moisture removed 2.

The disadvantages of this method are localized overheating of the material and insufficient rate of temperature decrease, which, when drying hydrophobized materials, leads to material loss of water-repellent properties.

Closest to the proposed method is a day of high-moisture materials by moving them and blowing a gaseous coolant stream in two stages, between which the spent heat carrier 3 is partially withdrawn.

The disadvantage of this method is the unsatisfactory quality of the drying process.

The purpose of the invention is to improve the quality of the process when drying sheet water-repellent materials and preserving their water-repellent properties.

This goal is achieved by the fact that according to the method of drying high-moisture materials by moving them and blowing a gaseous coolant stream in two stages, between which we partially exhaust spent coolant, in the first stage they blow the coolant at a temperature of 180-210 ° С above the temperature of destruction of the water-repellent agent, and the partial removal of the spent coolant is carried out within 60–70% of its total amount, and at the second stage the coolant temperature is reduced at a rate of 4–5 C for percent moisture and a removable end hydrophobizator it when the temperature of the onset of degradation, followed by removing the remaining heat medium.

FIG. Figure 1 shows a graph of the change in the temperature of the coolant, the change in moisture in the material, and the temperature of the material over time; in fig. 2 is an installation diagram for implementing the drying method; in fig. 3 is a graph of temperature change of the coolant and moisture in the material over time and along the length of the installation; in fig. 4 shows the curve of change in material temperature versus time and length of installation.

The plant for high-moisture materials contains a machine 1 for cutting and laying plates, roller conveyors 2 dried, a machine 3 laying dried material, burners 4 for preparing a heat transfer fluid located on the side. surfaces along the entire length of the dried air duct 5 for the selection of coolant.

Installation for drying high-moisture

materials works as follows. The molded high moisture material enters the machine 1 for cutting and laying plates and onto roller conveyors 2 dryers, on which the material is heated, dehydrated, and fed to the machine 3, pallets. The speed of transporting the material along the length of the working channel of the dryer was selected so that the total duration of the drying process was 80 minutes. Level

0 temperatures (420 ° C) are achieved by regulating the amount of fuel supplied (natural gas) to the burners 4, located on the first third of the length of the drying unit, and by adjusting the amount of withdrawal of heat in the duct 5. The temperature is controlled by stationary chromel-copel thermocouples, installed above and below the transported material in each section of the drying unit. The rate of decrease in the temperature of the coolant body is ensured by a uniform decrease in the gas flow rate in the burners over the length of the dryer until the temperature is established to be equal to the temperature of destruction used by the water repellent agent. The remaining amount of spent coolant through the removal is removed 5 at the end of the drying process, while the removal of moisture during the dewatering of highly moist materials is uneven and the intensity of its removal is divided into two periods (the period of drying and drying).

FIG. 1 curve 1 depicts a graph of the change in the temperature of the coolant during the drying process with time; curve 2 - loss of moisture from time; curve 3 - change in temperature of the material with time.

The temperature of the material during the drying process increases (heating of the material during the drying process increases (heating of the material) to point A. The section AB on curve 3 is a typical area for drying high-moisture materials and indicates that at point B (the end of the drying period) was removed 58-60 % of the total moisture of the material (point K on curve 2). Considering that at point B removes more than half of all the moisture of the material, in order to reduce fuel consumption at this point (point B), it is necessary to establish the extraction of the spent heat carrier saturated with evaporated moisture. tbor heat medium to point B lowers fuel efficiency, and the selection of point B (the temperature at uchastke.podema) leads to excessive fuel consumption for overheating excess amount of water vapor in the coolant.

Intensive removal of moisture from the material is possible only if it is ensured that the moisture evaporated from the material is completely absorbed by the coolant and is timely removed from the working channel. Taking into account the characteristic features of the drying of highly moist hydrophobic materials, the selection of heat-transfer agent (saturated with water vapor) is carried out in two places, with 60-VL / o of the total amount taken at the end of the first period of the process (first selection at point B).

At the same time, the coolant, which is 180-210 ° C above the temperature of destruction of the water-repellent agent, does not have enough time to over-accumulate and retains the ability to absorb water vapor (Tables 1 and 2).

The remaining amount of coolant is removed at the end of the drying period (second selection at point C).

During the heat treatment of hydrophobized materials, it is necessary to take into account the temperature of destruction (loss of water-repellent properties) of the water-repellent agent, which for various types of water-repellent agent is usually above 200 ° C.

Example 1. The experiments were carried out by a known 2 method. The highly moist, hydrophobic material was heated by a coolant exceeding 700 ° C the temperature of the material's heat resistance (t 1450 ° C), and the cooling was conducted at a rate of decrease of the coolant temperature equal to 2.5 ° C per percent of moisture removed (Table 1 experiment 1). The duration of the process of the piece was 50 minutes, which allowed to develop

unit with the required performance. The study of the material for water absorption (determination of water-repellent properties showed that the water-repellent agent was completely destroyed and the material does not have water-repellent (hydrophobic) properties. Therefore, this method cannot be used for drying hydrophobized materials.

Example 2: FIG. 1 shows the curves

0 characterizing the method of drying high-moisture plates based on basalt fibers (PMTB-2 and PMTB-3). The duration of the process is 80 minutes, the duration of the drying period is 26-27 minutes (point B on curve 3).

Taking into account the above, the installation of the first selection of the heat transfer medium in the drying unit is carried out as follows: design point B on curve 1 (Fig. 3) of changing the material temperature to the L axis (unit length) and determine the location of the installation of the first selection 5 (Fig. 2), and the second selection of 6 similar design point C.

Example 3. FIG. Figure 4 shows the curve of the change in material temperature from the time and length of the unit in the process of drying high-moisture perlite plates according to the proposed method. In absolute terms, the drying time of perlite-based plates is 1.5 times longer than that of basalt-based fibers. Therefore, when the length of the unit is 30 m

The material does not dry for 80 minutes, but 120 minutes, and the drying period is 40 minutes. The nature of the curve of the temperature change of the material (points A, B, C) is similar to curve 1 (Fig. 3) for high-moisture basalt-based plates.

fibers. The places of coolant selection are defined similarly (as in the first example).

Example 4. The data (see experiment 2) on the drying of water-repellent plates showed that

0 with a uniform heating of the material with a heat carrier with a temperature (210 ° C) not exceeding the temperature of the beginning of the degradation of the water-repellent agent, the duration of the process of drying the plates was 130 minutes. The material for water absorption is fully consistent

 established requirements. However, the long heat treatment time does not allow the development of an aggregate of the required capacity.

Example 5. Sheet high-moisture hydrophobic heater material with heat carrier exceeding the degradation temperature of water-repellent agent by 170 ° C (t 380 ° C) and further heating was carried out with heat carrier, the rate of temperature decrease of which is 4-5 ° C

5 percent of moisture removed, up to the temperature of the onset of degradation of the water repellent. The dried material was tested for water absorption (for 24 hours, the material placed in

water, can absorb no more than 30% moisture). The data given in table. 1 (experiment 16 and 17) show that samples that are dried by the proposed method have a water absorption of not more than 30%, but the drying time is high

Example 6. A series of experiments as in example 3, but the temperature exceeding the temperature of destruction of the water-repellent agent was 180210 ° С (Table 1, experiments 6-15). The minimum excess temperature is 180 ° C, and at a lower one (experiments 16-18), an increase in the duration of the drying process is observed, which reduces the productivity of the drying line and the whole production line. The water absorption of the material does not exceed the permissible value (30%). An increase in the duration of the process is also observed with an increase in the rate of decrease in temperature (experiments 9-13) relative to the result of experiment 14.

The proposed temperature level of the heat carrier in the drying period, which is 180 ± 210 ° C above the degradation temperature of the water-repellent agent, at a rate of decreasing the temperature 4- (for the percentage of moisture removed during the drying period is the most rational.

Example 7. In selection 1, which is carried out at the end of the first period of the dewatering process, 55% of the total amount of spent heat transfer fluid and water vapor is removed. The duration of the process was 72 minutes, and the temperature was 195 ° C (experiment 1). The high temperature of the effluent coolant indicates a lack of efficiency in the use of heat, so it is necessary to remove the coolant at such a temperature as to maximize its heat transfer and to ensure the necessary intensity (duration) of the process.

Example 8. Experience as in Example 5, but removing 60% of the total amount of coolant. The remaining data, as in experiment 2 (table. 2).

Example 9. Similar to previous experiments, but in the first selection 70% of the total amount of heat-transfer agent is removed (experiment 3).

Example 10. In selection 1, 75% of the total amount of spent heat transfer fluid and water vapor is removed (run 4). The process duration is 82 min, the temperature of the waste heat carrier is 150 ° C. In this embodiment, the temperature is low (fairly good use of heat), but the process duration has increased significantly, and during conveyor production, we obtain a proportional decrease in line capacity.

Examples 7-10 indicate that the most rational selection parameters are 60-70%, which allow for rational use of heat and provide a given unit capacity (process intensity).

An investigation of the process of drying sheet highly moist hydrophobized materials showed that the maximum temperature exceeding the degradation temperature of the water repellent agent is 210 ° C, and at a higher temperature, deterioration of the hydrophobic properties of the material is observed (Table 1, experiments 3-5), water absorption above 30%. At the same time, the rate of decrease in temperature should be in the range of 4-5 ° C for the percentage of moisture removed (experiments 7-8). A lower rate (experiment 6) results in water absorption above 30%, which is not acceptable, and a higher rate (experiment 9) results in an increase in the duration of the drying process.

Thus, if at the end of period 5 of the extract, 60-70% of the total amount of spent coolant and water vapor are taken, and the rest at the end of the drying period, the proposed drying method solves the problem of obtaining quality products with the required water-repellent properties dried

Table 1

table 2

Claims (1)

METHOD OF DRYING HIGH-WATER MATERIALS by moving them and blowing them with a gaseous heat carrier stream in two stages, between which a partial selection of the spent heat carrier is carried out, characterized in that, in order to improve the quality of the process when drying sheet water-repellent materials and preserve their water-repellent properties, at the first stage blowing is carried out with a coolant with a temperature 180 to 210 ° C higher than the temperature of the destruction of the water repellent, and a partial selection of the spent coolant is carried out within 60–70% of its total amount, moreover, in the second stage, the coolant temperature is reduced at a rate of 4-5 ° C by the percentage of moisture removed and it ends when the hydrophobicizer reaches the temperature at which the destruction begins, followed by removal of the remaining coolant.