SU1139947A1 - Device for drying moulded plates of lead storage batteries - Google Patents

Abstract

THE METHOD OF DRYING OTFORMING BATH BATTERY PLATES OF LEAD ACCUMULATORS by blowing them out by sequential movement through three zones with individual parameters of the heat-transfer agent. moreover, when drying negative plates in the first zone, airflow is carried out for 2-2.5 minutes with a heat carrier with a temperature of 210-220 ° C, a speed of 7-8 m / s, and a moisture content of 25-40 g / kg of dry matter, that, in order to increase the productivity, quality and efficiency of the process of simultaneous drying of negative and positive plates, in the second 3orte negative plates are blown for 1.0-1.5 minutes with a heat carrier with a temperature of 195-205 ° C, speed 8.5- 9 m / s and moisture content of 65-70 g / kg of dry matter, in the third zone they are blown into tons For 1.5–2.0 minutes with a coolant with a temperature of 170–190 ° C at a speed of 7–8 m / s and a moisture content of 80–85 g / kg of dry matter, and I spent coolant from the third zone of the negative plates blowing direction (L l in the first zone of the positive plates.

Description

The invention relates to the drying of molded plates of lead-acid batteries.

Methods are known for convective drying of formed plates of lead-acid batteries by their successive movement through zones, having various parameters of the coolant. Drying of negative and positive plates is carried out at different heat and humidity conditions in separate drying units.

Drying of the positive drying plates is performed in three-zone convective drying units with a heat carrier with the following parameters: in the first zone the temperature of the coolant is 160-180 ° C, speed 4-6 m / s, relative humidity Ф; 20%; in the second zone the temperature of the coolant is 130-150 ° C, the speed is 4-6 m / s, relative humidity (% and in the third zone the temperature of the coolant is 80-100 ° C, speed 3-4 m / s, relative humidity. The total drying time of the plates is 15-25 minutes.

This method does not provide an intensive process of heat transfer and is characterized by insufficient quality drying.

The closest to the invention is a method according to which the drying of negative plates is also carried out in three zone convective installations, with airflow in the first zone being carried out for 2-2.5 minutes with coolant with a temperature of 210-220 ° C, speed of 7-8 m / s and a moisture content of 25–40 g / kg of dry matter, in the second zone - for 2–3 min by a coolant with a temperature of 180–1990 ° C and a speed of 7–8 m / s and a moisture content of 40–60 g / kg of dry matter, and in the third zone - for 3-3.5 min. coolant with a temperature of 120-130 ° C, speed of 5-6 m / s and moisture content Niemi 60-80 g / kg dry substance 2.

Heat losses with the spent heat carrier are one of the factors determining the economical operation of the drying unit; therefore, the well-known modes of operation provide for a decrease in the temperature of the coolant in the last zones of the drying units. The above, as a prototype, the mode of drying negative plates also provides for a gradual decrease in the temperature of the heat transfer medium in the second and third zones so that the temperature of the heat transfer medium removed from the installation is in the order of 75–85 ° C (120–130 ° C — average temperature). heat carrier in the third zone).

If for a number of materials such a decrease in temperature does not affect the quality or has a positive effect, then for negative plates a decrease in the coolant temperature in the latter zones leads to a deterioration in the quality of the plates.

The quality requirements of the dried negative plates limit the upper

the oxidation limit is in percent; however, under factory conditions, oxidation often increases to 15%.

Rechargeable batteries, which include negative plates with high oxidation, have a reduced capacity and a short discharge time.

Studies have shown that a decrease in the oxidation of the active mass of negative plates can be achieved by increasing the average temperature level of the process to 180–200 ° C. At the same time, the drying of the plates is also significantly intensified, and the possibilities of increasing the productivity of the plant open up.

However, it is not possible to increase the temperature of the heat transfer medium in the second and third zones in drying plants that work by a known method, since this increases the temperature of the spent heat transfer fluid, which leads to a decrease in the economics of the plant operation.

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The purpose of the invention is to increase the productivity and efficiency of the process of simultaneous drying of negative and positive plates.

This goal is achieved by the fact that according to the method of drying the molded plates of lead batteries, they are blown by sequentially moving through three zones with individual parameters of the heat carrier, and when drying the negative plates in the first zone

0 lead for 2-2.5 minutes with a coolant with a temperature of 210-220 ° C, a speed of 7–8 m / s and a moisture content m 25–40 g / kg of dry matter, in the second zone the negative plates are blown for 1.0 - 1.5 min coolant with a temperature of 195-

5,205 ° С, speed 8.5-9 m / s and moisture content 65-70 g / kg of dry matter, in the third zone they are blown for 1.5-2.0 minutes with coolant with a temperature of 170-190 ° С, speed 7-8 m / s and a moisture content of 80- 85 g / kg of dry matter, and spent

0, the coolant from the third zone of the negative plate blowout is directed to the first zone of the positive plate blower.

With such drying parameters, the whole process takes place in the second period, moisture evaporation during the whole dewatering process takes place inside the material, which ensures the movement of moisture to the surface only in the form of steam, excluding conditions that promote oxidation of the active mass of the plates.

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The drying conditions and regularities of the process for the first zone, known from the prototype, remain valid for the proposed method. An increase in the temperature of the coolant in the first zone will lead to the melting of the lattice and the shedding of the active mass. The expected increase in the temperature of the coolant in the second and third stages of drying contributes to the deepening of the evaporation zone and reduction of oxidation. active mass.

So, in comparison with the prototype, an increase in the temperature of the heat carrier only in the second zone from 180 to 200 ° C (all other parameters in the zones remain unchanged) reduces the oxidation of the plates from 4.6 to 4.1%. The proposed increase in the temperature of the coolant in the second zone to 200 ° C and in the third zone to 180 ° C reduces the oxidation of the active mass of the plates to 3.0%. At the same time, the duration of dehydration is reduced by 20-30%, ways to increase plant productivity will open. With a further increase in the temperature of the coolant in the second and third zones, the lattice softens and, as a result, the plates warp. However, the expediency of using high-temperature heat transfer media in these zones to improve product quality and intensify the drying process conflicts with the economics of the plant, since the release of the exhaust heat carrier with an average temperature of 170-190 ° C will lead to a sharp increase in heat loss and deterioration of the economics of the drying process .

In the general case, it would make sense to recycle the spent high-temperature coolant to the first zone, add it to the hot coolant, but studies have shown that the specific material of the negative plates does not allow the relative humidity of the coolant to increase at the beginning of the drying process above 5% (absolute moisture content is not more than 40 g / kg of dry matter). Exceeding these values (to which recirculation of the spent moist heat carrier would lead) causes a sharp increase in the oxidation of the active mass of the plates, i.e., their quality deterioration. Thus, an increase in the moisture content of the coolant at the beginning of the drying process from 30 to 70 g / kg of dry matter increases the oxidation of the plates from 4.6 to 6.4%. With a simultaneous increase in the moisture content of the heat carrier in the second and third zones, respectively, up to and 90 and 110 g / kg of dry matter, the oxidation of the plates increases to 7.3%.

Thus, if there are tunneling installations for positive plates located in which the increase in the moisture content of the heat carrier during the whole drying process does not affect the quality of the products, it is expedient to direct the high-temperature heat carrier after drying the negative plates to drying the positive plates. In this case, all indicators of the process of dewatering negative plates are improved, and the efficiency of operation of both plants is increased.

Bringing the velocity of the coolant in the second zone of the negative plate drying to 8-9 m / s contributes to

that the drying process is fully carried out in the second period.

A further increase in speed is inexpedient, since the electric power consumption of the fan motors increases substantially. A decrease in all the specified parameters will lead to a prolongation of the drying time and an increase in the oxidation of the plates.

The drawing shows schematically parallel-arranged drying units for positive and negative plates, operating according to the proposed method.

The device consists of drying units 1 and 2, respectively, for negative and positive plates, circulation fans 3 and 4 (respectively, for installations 1 and 2), one for each zone, air-heating units 5 and 6, respectively, one for each zone and a suction valve torus 7, which is at the same time a circulation fan of the third zone of installation 1, ducts 8 for supplying hot and cold coolant, pipes 9 for suction of exhaust coolant from the zone, duct 10 serving as for supplying high-temperature exhaust heat medium in the drying unit the positive plates, the mixing chamber 11 and the recycle path 12 Fitting 2.

The operation of the plants is as follows.

In the first zone of the drying unit 1, the hot coolant is supplied through the air duct 8. It passes through wet plates suspended from chains. The spent heat carrier of the first zone is diluted with cold air (arrow A) sucked through the loading end of the device. This mixture, through the two lower pipes 9, which are located symmetrically in the side walls of the drying chamber, is taken by the circulation fan 3 and fed to the installation 5 of the first zone, where it is again heated to the temperature of the first zone. The external air inflow through the loading end of the drying unit is regulated by the suction fan 7 of the third zone and is provided in the amount necessary for the removal of all the moisture evaporated from the drying unit 1.

Part of the spent coolant of the first zone in an amount equal to the suction through the boot end, flows through the overflow (arrow B) into the second zone, where

0 is also mixed with the exhaust coolant and with the help of the circulation fan 3 of the second zone enters the heater unit 5. The hot coolant with the parameters determined for the second zone of the installation enters the second zone of the drying chamber through the duct 8. In the second zone, the plates are dried to a second critical humidity. Part of the spent coolant (on

arrow B) flows to the third zone, where it mixes with the exhaust coolant of this zone and outside air drawn in through leakages at the discharge end of the installation. The work of the third zone is similar to the two previous ones, they. At the end of the third zone, the moisture of the plates is zero Part of the spent heat transfer fluid of the third zone in an amount necessary for the removal of all moisture evaporated in the installation is not emitted into the atmosphere, and with the help of the fan 7 through the duct 10 is fed into the mixing chamber 11, where it is mixed with the outer air and a recirculation coolant flowing through the channel 12 of the first installation zone for positive molded plates. From the mixing chamber, the coolant is circulated by a circulation fan 4 to the first installation zone for the positive plates. If necessary, due to the capacity of the installation 2, the coolant may be additionally heated in the installation 6 of the first zone, or the hot coolant is added to the mixing chamber 11. The operation of the installation 2 is carried out similarly to the operation of installation 1 in the known modes 1.

Example. At the experimental setup, the negative formed plates of lead accumulators were dried. To obtain comparative data, the plates were dried in seven modes.

The test results are shown in the table.

The following designations are given in the table: t - heat carrier temperature, ° С; v - speed, m / s; d - moisture content, g / kg of dry matter.

As can be seen from the table, the use of high-temperature heat transfer medium in the second and mainly in the third zone of the installation (examples 3 and 4) reduces the duration of the substrate from 7–9 to 4.5–6 min and improves the quality of the material (oxidation of the plates, determining the capacity of the battery batteries, decreasing on average from 3.9 to 2.9%).

The decrease in the temperature of the coolant in the proposed method leads to an increase in the drying time of the plates and an increase in oxidation. An increase in the temperature of the heat carrier in the first zone to 235 ° C (Example 5) causes softening and melting

lattice and shedding of the active mass of the plate, the oxidation of the plates is not reduced. With constant parameters of the coolant in the first zone, an increase in temperature in the second and third zones (Example 6) somewhat reduces the drying time without altering the oxidation of the plates, but in a number of experiments a softening of the lattice was observed. With an increase in the moisture content of the coolant in the second and third zones, respectively, to 90 and 110 g / kg of dry matter (example 7), the duration of the process increases to 6.2 minutes and the oxidation of the plates increases to 4.1%, i.e., the quality of the plates and performance decrease drying installation.

Calculations carried out to determine heat loss with the spent heat carrier were made for a drying unit with a capacity of 7,000 pieces. negative plates per hour. The amount of spent coolant required to remove all moisture evaporated from the plant in the zones is 4900 kg / h. Heat losses with spent coolant are 83200 and 107000 kcal / h for examples 1 and 2, respectively.

When machines for drying positive and negative plates using the proposed method work together, the spent coolant after drying the negative plates is directed to a drying unit for positive plates, which leads to savings in the above amounts of heat or (if the unit is equipped with electric heaters) elect Roenergy in the amount of 97-125 kW.

The amount of heat sent to the positive plate installation is about 38-40% of the total heat entering its first zone.

Thus, the use of coolant with a temperature of 170–205 ° C in the last zones of the plant for drying negative plates makes it possible to intensify the processes in these zones and by 30–40% increase the plant capacity, improve the quality of dried negative plates, reduce the amount of inhibitor used to reduce oxidation and also by 10-20% to reduce the heat consumption for drying the formed plates, calculated on both drying units.

Claims (1)

METHOD OF DRYING FORMED PLATES OF LEAD ACCUMULATORS by blowing them in succession through three zones with individual coolant parameters, moreover, when negative plates are dried in the first zone, they are blown for 2–2.5 minutes with a coolant with a temperature of 210–220 ° С, a speed of 7– 8 m / s and a moisture content of 25-40 g / kg dry matter, characterized in that, in order to increase the productivity, quality and economy of the process of simultaneous drying of negative and positive plates, in the second zoya negative the plates are blown for 1.0–1.5 min with a coolant with a temperature of 195–205 ° С, a speed of 8.5–9 m / s and a moisture content of 65–70 g / kg of dry matter, in the third zone they are blown for 1, 5–2.0 min with a coolant with a temperature of 170–190 ° С, a speed of 7–8 m / s and a moisture content of 80–85 g / kg of dry matter, aq the spent coolant from the third zone of airflow of negative plates is sent to the first zone of airflow of positive plates . SU „„ 1139947