RU2338974C2 - Method of slurred materials drying in roll-tape dryer with cyclic mode of drying agent discharge - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: in method of slurred materials drying in roll-tape dryer, which includes extrusion of dried material, its successive transportation through drying chambers with counterflow-cross travel of drying agent, discharge of drying agent and its partial reuse, discharge of drying agent is carried out in cyclic mode, which includes saturation of drying agent and drain of drying agent, at that duration of discharge and shutdown is determined depending on preset moisture content of drying agent, and drying agent moisture content is monitored by its temperature, at that moisture content of drying agent varies within the limits of 0.033-0.051 kg/kg, and drying process changes over into automodel mode, when the system itself sets flow rate of drying agent depending on moisture content of drying agent and humidity of dried material.

EFFECT: reduction of power inputs and intensification of drying process.

3 cl, 4 dwg

Description

The invention relates to a process for drying pasty materials and can be used in chemical and related industries.

Known methods of drying pasty materials in drying plants containing a roller system, plate and scraper conveyors, steam heaters and recirculation fans, where the briquettes of the dried material are dried on a plate conveyor with continuous removal of the spent drying agent [1]. The disadvantage of these methods is significant energy consumption for the drying process of 37-45 GJ / t of dry product, low productivity of 30-50 kg of dry product / h, removal of the drying agent with low humidity 0,0175-0,023 kg / kg at a high temperature of 60-75 ° C

There are also known methods of drying on belt dryers, in which drying is carried out by air or its mixture with flue gases at a temperature of the mixture of 70-170 ° C. Air circulation is carried out by TsAGI axial fans. Air passes through the material from top to bottom and presses the material to be dried to the conveyor belt [2]. Their disadvantage is the unevenness of drying along the thickness of the layer. The best results for uniformity of drying are provided by methods where multi-tier belt dryers are used, in which the material is mixed when transferring from one belt to another. In these methods, the heat consumption is from 5000 to 7500 kJ / kg of moisture, and electricity is up to 10 kWh per 1 ton of evaporated moisture.

The purpose of the invention is the reduction of energy consumption and the intensification of the drying process of pasty materials in a roll-type dryer (SVL) with the successive movement of the dried material through the drying chambers with countercurrent cross-movement of the drying agent.

This goal is achieved by the fact that in the roll dryer the removal of the spent agent is organized in a cyclic mode. The cyclic mode of removal of the drying agent is carried out by turning the exhaust fan on and off; the fan is turned on when the specified maximum is reached, and the fan is turned off when the specified minimum humidity of the drying agent is reached in the chamber that is most intense in terms of moisture removal, i.e. the chamber in which the maximum amount of moisture is removed. The moisture content of the drying agent is controlled by its temperature. Using this mode of removal of the drying agent provides an increase in the average moisture content of the spent drying agent and allows you to increase the temperature of the dried material, which increases the rate of moisture removal from the material without additional energy costs.

The method is illustrated by the schemes:

Figure 1. Diagram of a roll dryer

The dryer contains a housing 1, a roller system 2, a knife mechanism 3, a plate conveyor 4, a system for removing the spent drying agent 5; To remove the drying agent from each chamber, the dryer is equipped with a slide system 6 and an exhaust fan 7, fresh inflow of the drying agent is provided through the intake windows 8. The dryer contains heaters 9 for heating the drying agent and recirculation fans 10 for supplying the drying agent to the layer of the dried material. Temperature control in the dryer chambers is carried out using thermocouples 11, a thermocouple 12 is installed at the outlet.

Figure 2. Kinetic curves of the drying process in a continuous mode (curve 1) and in a cyclic mode (curve 2).

Kinetic curves allow you to determine the most intense chamber for moisture removal. For the five-chamber dryer shown in FIG. 1, it was found that the maximum amount of moisture is removed in the second chamber.

Figure 3. Dependence of moisture content and temperature of the drying agent over time in the dryer chamber, which is the most stressed in the moisture capacity (second).

The saturation rate of the drying agent was determined by the change in the humidity of the drying agent in the second drying chamber when the exhaust fan stopped (curve 1) and when starting (curve 2). Depending on the rate of saturation, the frequency of the drying agent removal cycles was chosen.

Figure 4. Cyclogram of the temperature and moisture content of the drying agent during cyclic operation of the exhaust fan.

The drying method is as follows.

The initial paste-like material enters the roller system 2, where it is molded in the form of briquettes and with the help of a knife mechanism 3 is unloaded onto a moving plate conveyor 4. The briquettes are dried by their countercurrent-cross movement with a drying agent. The drying agent enters the dryer through the intake windows 8 and is transported by a recirculation fan to the air heater 9, where it is heated and, passing through a layer of material, partially returns to the air heater, mixing with fresh air, and partially through the gate system 6 and the exhaust agent removal system 5 is removed from the dryer by an exhaust fan 7 operating in a cyclic reset mode. The frequency of turning on the exhaust fan is set depending on the speed of saturation of the drying agent in the chamber (the second), which is the most intense in terms of moisture removal, the duration of removal of the drying agent is 4 minutes, and the stop is 7 minutes.

To ensure a cyclic mode of removal of the drying agent, the temperature in the chambers is controlled using installed thermocouples 11 in the chamber of the dryer. The moisture content of the drying agent varies in the range of 033-0.051 kg / kg and is controlled by its temperature using a thermocouple 12 installed in the duct.

The drying process goes into a self-similar mode, when the system itself sets the consumption of the drying agent, depending on the moisture content of the air and the humidity of the dried material, i.e. the operation time of the exhaust fan (independent variable) is determined depending on the moisture content of the drying agent (dynamic variable).

Using the cyclic regime of drying agent removal provides an increase in the average moisture content of the drying agent from 0.0195 to 0.0276 kg / kg and allows to increase the temperature of the dried material: at the beginning of the second chamber from 36 to 42 ° C, at the end from 50 to 67 ° C ( see figure 2) without additional energy consumption. Thus, the claimed technical result is achieved - reducing energy consumption and intensifying the drying process of pasty materials.

A cyclic mode of operation of the SVL was introduced at Pigment OJSC, Tambov, during the drying of azo pigments, which allowed reducing steam consumption by 1.5 times and increasing productivity by 40%.

The presented specific example of the drying method illustrates, but does not limit the invention.

Information sources

1. Chernobyl II etc. Drying plants of the chemical industry. Kiev, Technique, 1969, p. 124.

2. Lebedev P.D. Heat exchangers, drying and refrigeration units. Textbook for students of technical universities. Vol. 2, rev. M., Energy, 1972, p. 317.

Claims (3)

1. The method of drying pasty materials in a rolling mill dryer, comprising molding the material to be dried, moving it sequentially through the drying chambers with countercurrent cross-movement of the drying agent, withdrawing the drying agent and its partial reuse, characterized in that the drying agent is withdrawn in a cyclic mode, including saturation of the drying agent and the removal of the drying agent, and the duration of the drain and stop is determined depending on the desired moisture Zhaniya drying agent, and controlling the moisture content of the drying agent by its temperature. 2. The method according to claim 1, characterized in that the removal of the drying agent is carried out using an exhaust fan, and the frequency of turning on the fan is set depending on the saturation rate of the drying agent in the drying chamber, which is the most intense in terms of moisture content. 3. The method according to claims 1 and 2, characterized in that the moisture content of the drying agent varies in the range of 0.033-0.051 kg / kg and is controlled by its temperature using a thermocouple, and the drying process goes into self-similar mode when the system itself sets the flow rate of the drying agent depending on the moisture content of the drying agent and the moisture content of the dried material.

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