ES2226539B1 - DRYING EQUIPMENT AND PROCEDURE. - Google Patents

Abstract

Equipment and drying procedure. The equipment comprises a drying chamber (7), where the material is arranged, a conduit (8) that forms a closed circuit with said chamber, said chamber having an inlet and an outlet communicated by said conduit, a condenser (2), downstream of said chamber in said duct, a heater (3) upstream of said chamber in said duct and a fan (5). The method comprises: a) arranging a material in a drying chamber; b) introducing and recirculating an air flow in said chamber and a recirculation duct that forms a closed circuit with said chamber; c) heating the chamber air with a heater; d) cooling the moist air that leaves the chamber with a condenser; e) recirculating the condenser outlet air to the heater; and f) repeat steps b) -e) until the material dries.

Description

Equipment and drying procedure.

Field of the Invention

The present invention relates to equipment for carry out the drying of materials. In particular, the invention refers to equipment for drying porous materials, such such as skins, leather, various fabrics or any other material to dry off.

The present invention also relates to a Condensation drying procedure that allows working at high temperatures and relative humidity.

Background of the invention

The drying systems or equipment used currently to carry out drying of porous materials, especially wood, leather, skins, various fabrics or others materials that contain a high percentage of moisture use drying chambers or tunnels without air recirculation that, generally, they work with very low relative humidity.

However, as far as the operation of the equipment or system refers to the antecedent that can be considered closest to the present application would be a drying chamber Equipped with a heat pump. Next, it is described of schematically the operation of a heat pump to facilitate comparison with the equipment of the present invention.

A heat pump consists of a closed circuit through which a freon type gas circulates which is liquefied by compression. The heat given in the change of state can be used as a source Heater The heat pump also comprises an area of water vapor condensation that is obtained by cooling that occurs when the liquid freon expands into phase gas.

For the proper functioning of a pump heat is necessary to consume energy, usually electrical, which allows to operate the compressor and start and maintain the cycle. This consumption of electricity is expensive, in relation to Other forms of energy.

In addition, equipment based on a heat pump It has the disadvantage that if there are leaks, Freon gas will releases the atmosphere, the circuit is empty and the equipment stops function.

Therefore, a drying equipment that uses a heat pump has environmental problems, in case of leakage, inconvenience of equipment operation, in case of leakage the equipment stops working, and economic inconvenience since electrical power is required to run the compressor. Consequently, drying equipment equipped with a heat pump must carry out strict maintenance of the equipment in order to avoid possible gas leaks with the economic increase that this represents. In addition, generally, the vapors that are released during the drying operation, in some cases, contain acidic products that favor corrosion of the
team.

In a drying equipment equipped with a pump heat, the working temperature of the equipment is limited, since if it is too high, the freon gas does not condense. In addition, you cannot work at high relative humidity because in that case, the condensation water freezes at the points of heat exchange cooling.

This limitation is one of the main drawbacks of a drying system equipped with a pump hot.

Still another drawback to highlight is the fact that the mass of liquefied gas, for example freon, and the mass of gas condensate must be the same because it is a closed circuit. This limits the amounts of energy that cannot be variable. in hot and cold light bulbs.

Description of the invention

The objective of the present invention is provide equipment and a drying procedure that allows work at high temperatures and relative humidity.

The present inventors have identified that the replacement of a heat pump with two heat exchangers heat, one condenser and another heater that serve to cool and respectively heat the recirculated air, located in a duct that forms a closed circuit with a drying chamber allows drying at relative temperatures and humidity high.

In accordance with a first aspect of the present invention, a drying equipment is provided which is characterized by the fact that it comprises a drying chamber or tunnel (7), where the material to be dried is arranged, a recirculation duct (8) forming a closed circuit with the chamber or drying tunnel, presenting said camera at least one entry and at least one output both communicated by said recirculation duct (8), an exchanger-condenser (2) downstream of the drying chamber and an exchanger-heater (3) upstream of the drying chamber, both in said conduit of recirculation (8).

A second aspect of the present invention is provide a procedure for drying by condensation.

According to the second aspect of the invention, the drying process is characterized by the fact that the following stages are carried out:

a) arrange a material to dry inside a drying chamber or tunnel (7);

b) introduce and recirculate an air flow a through said chamber or drying tunnel and through a conduit of recirculation (8) that forms a closed circuit with said camera;

c) heat the chamber or tunnel air drying (7) using an exchanger-heater (3) upstream of the chamber or drying tunnel (7);

d) cool the moist air that comes out of the chamber or drying tunnel using a exchanger-condenser (2) downstream of the drying chamber or tunnel (7);

e) recirculate the outlet air of the exchanger-condenser (2) until heat exchanger (3) through the duct (8) comprising a fan (5); Y

f) repeat steps b), c), d) and e) until obtain the desired degree of final moisture in the material to dry off.

In particular, in step a), the material a dry is, in turn, inside drums or other devices equivalent.

Advantageously, following step f), it is carries out a final stage of conditioning the material to dry which comprises reducing the air inlet temperature to the chamber until the entered air temperature is reached initially in the camera.

Advantageously, the amounts of heat available in hot spotlights (heat exchanger) and cold (exchanger-condenser) of the exchangers can be considered independent of the team, what which confers greater process versatility.

Also advantageously, the heat exchanger that heats the circuit water through a heating medium can use various fuels or hot liquids, saving energy costs since one more energy can be selected
profitable.

Also advantageously, the drying air that circulates through the drying chamber and recirculation duct is the same, which makes it independent of weather conditions outside In addition, due to this and compared to the dried Conventional, no water vapor, hot air is released environment, nor volatile organic compounds (VOC's).

Advantageously, the equipment of the present invention can be automated using a controller with a set point that measures the temperature of the air at the outlet of the exchanger-condenser and acting on a cooling water flow inlet control valve in The exchanger-condenser. It can also automate the control of the outlet air temperature of the heat exchanger using a controller with a set point that measures said temperature at the exit of the heat exchanger and acting on a Inlet control valve for hot water flow or over a fuel flow inlet control valve in the heat exchanger.

Figures

Figure 1 is a schematic representation of the equipment used to carry out the drying process by condensation of the present invention.

Figure 2 is a psychometric diagram that shows the hygroscopic curves of water vapor in air in air temperature function. In ordinates the absolute humidity Ha, expressed in kg of water vapor / kg of air dry, and in abscissa the temperature of dry air, expressed in ºC.

The following describes in more detail the Figure 1.

Figure 1 shows a device (1) that comprises two heat exchangers (2) and (3), one condenser (2) and another heater (3). He heat exchanger (3) uses means of heating (4) to heat the water that circulates inside. In the drying chamber (7) the material to be dried is arranged in some supports (6), said chamber comprising at least one input and at least one exit, both communicated through a conduit of recirculation (8) that forms a closed circuit with the chamber of dried

Both heat exchangers meet separated by a fan (5) that drives the air and does Recirculate within the team.

The exchanger-condenser (2) it is located downstream of the drying chamber and the heat exchanger (3) is located waters above the drying chamber, both inside the duct recirculation (8).

The air flowing through the duct recirculation (8) enters the drying chamber (7) after passing by the heat exchanger (3), drying the material located in the supports (6) and leaving the chamber of drying (7) to enter the recirculation duct (8) and pass by the exchanger-condenser (2).

The exchanger-condenser (2) comprises a water inlet (9) at a temperature Te_ {9-water} and a water outlet (10) at a Ts_ {10-water} temperature, the gradient being positive temperatures

The heat exchanger (3) comprises a water inlet (11) at a temperature Te_ {11-water} and a water outlet (12) at a Ts_ {12-water} temperature, the gradient being negative temperatures

The following will describe in more detail the drying equipment and procedure in accordance with this invention.

Detailed description of the invention

Once the material has been arranged to dry in perforated supports or drums (6) inside the chamber or drying tunnel (7), power is supplied to a boiler (4) to heat the water that circulates inside the heat exchanger (3) which in turn heats the air entering the drying chamber (7). This is intended heat the drying chamber (7), the material to be dried and evaporate the water contained in said material.

The air leaving the drying chamber (7) it presents a high percentage of relative humidity and when it passes through the exchanger-condenser (2), fed with mains water, it cools and part of the water vapor in air condenses. The condensed liquid water is collected in the exchanger-condenser (2).

Advantageously, both condensed liquid water as the outlet water of exchanger-condenser (2) can, if interested, reused in a process annexed to that of the invention.

Thus, for example, in the case of skin drying, said water can be reused in the tanning process annexed to equipment of the invention, where the use of hot water is necessary to carry out the tanning of the skins.

We can also cite, as an example, the case of drying of fabrics, clothes, etc. where said hot water can be used in the washing process annexed to the equipment of the invention, process that must heat the water to carry out a wash effective.

Advantageously, the reuse of both water hot coming from the exit of steam exchanger (2) as of the steam condensed water represent an important energy saving post that, on the one hand, hot water is reused in another process annexed to that of the invention and, on the other, the problems are avoided derivatives of the formation of ice in the condenser.

At this stage of the procedure, the energy absorbed by water in the exchanger-condenser (\ DeltaT_ {water}> 0) is equal to the energy yielded by humid air. Energy ceded by air is the sum of the temperature difference between the moist air before exchanger-condenser and moist air after of the exchanger-condenser (\ DeltaT_ {air} <0) plus the latent heat of condensation. Advantageously, the reuse of energy absorbed by water in a process Annex to the equipment of the invention allows global savings important energy in the system.

The absolute humidity of the humid air before exchanger-condenser is greater than humidity absolute humid air after exchanger-condenser. In fact the moist air after the exchanger-condenser is saturated, that is to say it has a relative humidity of 100%.

This saturated water vapor air leaving the exchanger-condenser is recirculated by the recirculation duct (8) towards the heat exchanger (3) with the help of a fan (5) and when it passes through the heat exchanger (3), heated, of so that the relative humidity before heat exchanger (3) which is 100% is higher than relative humidity after heat exchanger (3) (see figure 2: "Psychometric diagram"), keeping the air the same humidity absolute before and after passing through the heat exchanger (3).

At this stage of the procedure, the energy ceded by water in the heat exchanger (ΔT_ {water} <0) is equal to the energy absorbed by the moist air (ΔT_ {air}> 0) before and after heat exchanger. In this stage of procedure does not occur state change.

Finally, note that the absolute humidity of the moist air entering the drying chamber is less than the absolute humidity of the humid air leaving the drying chamber, the difference being the evaporated moisture of the material by air to dry.

For greater understanding of how much has been exposed Some examples are accompanied in which, schematically and only to non-limiting title, realizations of the invention.

Examples Example 1 Condensation drying procedure of a tanned leather vegetable for use as a sole

In accordance with the process of the invention drying of 20 tanned crayons to the vegetable was carried out to sole (4.0 mm), previously drained, of total weight 95Kg, with a initial humidity of 45.6% calculated on real weight.

The drying procedure was performed in a waterproof chamber in three stages, which are detailed at continuation:

Stage I

Heating

The heat exchanger is launched for an hour at 55 ° C while the exchanger-condenser remained stationary. He objective was to heat the chamber, the skins and saturate the air of the chamber up to 85-90% relative humidity.

Stage II

Drying

The heat exchanger is maintained at 50 ° C and 70% relative humidity (RH) for 8h so that hot air enters the chamber while humid air Exchanger-condenser output, leaving saturated at 40 ° C (100100% RH). At this stage 18 were collected liters of condensation water.

Stage III

Final conditioning

To finish drying and condition the skins the heater was placed at 30 ° C (60% RH), which is the temperature at which air enters the chamber. At the exit of exchanger-condenser the saturated air is it was at 20 ° C (100 100% RH). This stage three lasted 14 hours and 15 liters of condensation water were collected.

Results obtained

Homogeneous drying of the croupiers was obtained, resulting in a final weight of 65 Kg with 15% calculated moisture About real weight.

After a visual study of the croupiers, Note that they do not break flower, they do not have a raised color and they are not curled up In conclusion, with the drying process by condensation of the present invention optimal drying was achieved from leather to sole.

Example 2 Condensation drying procedure of a tanned leather chrome for use as footwear

Following the procedure of the invention, carried out the drying of 10 chrome tanned sheets for footwear (1.4-1.6 mm), previously drained and passed through the vacuum for 2 minutes at 50 ° C, of total weight 22 kg, with a initial humidity of 50%, calculated on real weight.

The drying procedure was performed in a waterproof chamber in three stages, which are detailed at continuation:

Stage I

 Heating

The heat exchanger is launched for an hour at 55 ° C while the Refrigeration remained stopped. The goal was to heat the chamber, skins and saturate the chamber air to a humidity 90% relative.

Stage II

 Drying

The heat exchanger is kept at 40 ° C (65% RH) for 5h for hot air to enter in the chamber while humid air at the exit of the exchanger-condenser, left saturated at 30 ° C (approx 100% RH). At this stage 8.5 liters of water were collected of condensation

Stage III

Final conditioning

To finish drying and condition the skins, the heat exchanger was placed at 25 ° C (65% RH), which is the temperature at which the air enters the camera. At the exit of the exchanger-condenser, the saturated air was at 20 ° C (100100% RH). In this case stage three lasted 45 minutes and in total 0.5 were collected liters of condensation water.

Results obtained

Homogeneous drying of the leaves was obtained, resulting in a final weight of 13 Kg with 16% calculated humidity About real weight.

After a visual study of the skins comparing them with those obtained by conventional drying (vacuum + drying tunnel) it is observed that they have a smooth flower, with a good touch and somewhat softer than dried conventionally. Surface performance better than normal. In conclusion, with the process of the invention a optimal drying

Although it has been described and represented specific embodiments of the present invention, it is clear that the person skilled in the art may introduce variants and modifications, or replace the details with others technically equivalent, without departing from the scope of protection defined by the attached claims.

Thus, for example, it is also within the scope of protection of the present invention the replacement of the drying chamber as shown in figure 1 by a drying tunnel or other design that includes the elements defined in the appended claims.

Claims (14)

1. Drying equipment characterized by the fact that it comprises a drying chamber or tunnel (7), where the material to be dried is arranged, a recirculation duct (8) that forms a closed circuit with the drying chamber, presenting said drying chamber at least one inlet and at least one outlet both communicated by said recirculation duct (8), at least one exchanger-condenser (2) downstream of the drying chamber in said recirculation duct (8) , at least one heat exchanger (3) upstream of the drying chamber in said recirculation conduit (8), and a fan (5) between said exchangers in said recirculation conduit. 2. Drying equipment according to claim 1, characterized in that said exchangers are independent of each other. 3. Drying equipment according to claim 1, characterized in that said heat exchanger uses external heating means. 4. Drying equipment according to claim 3, characterized in that said heating means are selected from hot liquids or solid, liquid or gaseous fuels. 5. Drying equipment according to any of the preceding claims, characterized in that said exchangers comprise means for controlling the temperature of the recirculation air. 6. Drying process characterized by the fact that condensation drying is carried out comprising the following steps: a) arrange a material to dry inside a drying chamber or tunnel (7); b) introduce and recirculate an air flow a through said chamber or drying tunnel and through a conduit of recirculation (8) that forms a closed circuit with said camera; c) heat the chamber or tunnel air drying (7) using an exchanger-heater (3) upstream of the chamber or drying tunnel (7); d) cool the moist air that comes out of the chamber or drying tunnel using a exchanger-condenser (2) downstream of the drying chamber or tunnel (7); e) recirculate the outlet air of the exchanger-condenser (2) until heat exchanger (3) through the duct (8) comprising a fan (5); Y f) repeat steps b), c), d) and e) until obtain the desired degree of final moisture in the material to dry off. 7. Drying method according to claim 6, characterized in that the material to be dried is, in turn, inside a drum or equivalent device. 8. Drying process according to claim 6, characterized in that, following stage f), a final stage of conditioning the material to be dried is carried out, which comprises reducing the temperature of the air entering the chamber until the temperature of the air initially introduced into the chamber is reached. 9. Drying method according to claim 6, characterized in that the material to be dried is a porous material. 10. Drying method according to claim 9, characterized in that the material to be dried is wood. 11. Drying method according to claim 6, characterized in that the material to be dried is a fabric. 12. Drying method according to claim 11, characterized in that the material to be dried is selected from the group comprising skin, leather, sheets and clothing in general. 13. Drying process according to any of claims 6 to 12, characterized in that the evaporation of water vapor from the material to be dried takes place from within the material itself. 14. Drying method according to claim 6, characterized in that steps c) and d) are carried out automatically by means of a flow controller.