RU2705335C1 - Plant for drying paste-like materials in a swirled suspended layer of polydisperse inertial bodies - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the field of the chemical industry and serves to dry high-moisture pasty materials. Plant for drying pasty materials in a swirled suspended layer of polydisperse inert bodies comprises a biconical chamber, a separation chamber, spinneret of wet material, layer of polydisperse inert bodies, drum with tangential inputs of heat carrier and central cone. Outlet branch pipe is equipped with centrifugal classifier with electric drive and movable adjusting ring.

EFFECT: intensification of drying process, increased capacity of the device and improved quality of the ready product.

1 cl, 5 dwg

Description

The invention relates to drying equipment, and more particularly to dryers with an active hydrodynamic regime intended for drying pasty materials, and may find application in the manufacture of food products, medical preparations and dyes.

An analogue is a dryer (see USSR AS No. 1170250 in class F26B 17/10) for suspensions and pasty materials on inert bodies, containing a cylindrical-conical chamber of the suspended layer with a drum in the lower part, nozzles for the tangential entry of the coolant, and a cone with nozzles for supplying wet material. The disadvantages of this dryer are: a) the occurrence of local breakthroughs (channels) due to the inhomogeneity of the swirling air flow supplied into the swirling layer of material. In devices of this type with a maximum wearable amount of inert bodies, there is a violation of the uniformity of the hydrodynamics of the layer, which leads to the formation of channels and breakthroughs of the coolant and the release of inert bodies into the outlet pipe; b) the appearance of stagnant zones in which aggregation of wet material is observed with the number of inert bodies close to the maximum possible.

The prototype is a dryer for pasty materials on inert bodies (SU 1666898 A1), containing a cylindrical-conical chamber of the suspended layer, a drum for tangential inlet of the coolant with a cone, a diffuser and a ring coaxial with the chamber, and a side spinneret device.

The dryer operates as follows. The coolant supplied through the tangential inlets of the drum is divided by a conical insert and a cylindrical insert into two flows - wall and central, the inserts have rectangular windows that allow you to set the ratio of the coolant flows. The parietal and central flows of the coolant act on inert bodies and bring it into suspension. In this case, a dense ring-like swirling stream of inert bodies is formed, into which pasty material is introduced through the side spunbond device, dried, and discharged in the form of an air suspension with spent heat carrier. The parietal flow has a greater velocity than the central flow, which contributes to the abrasion of the dried layer of material. The organization of the optimal hydrodynamic regime is carried out by regulating the ratio of coolant flows.

The disadvantages of this dryer include the following:

Insignificant height of the working layer of inert bodies; insufficient kinetic energy of interacting inert bodies to remove dried films of materials exhibiting a noticeable adhesion to the surface of inert bodies upon drying; with a further increase in the productivity of the dryer due to an increase in the total flow rate of the heat carrier and wearable inert bodies, there is a significant increase in the amount of still wet material carried in the form of scaly particles carried away with the used heat carrier, as well as a noticeable amount of inert bodies, which affects the quality of the product (the presence of inert bodies in the finished product ) and leads to a large heterogeneity in the final moisture content of the product.

The aim of the invention is the intensification of the drying process of paste materials.

The goal is achieved in that the installation for drying pasty materials in a swirling suspended layer of polydisperse inert bodies, containing a biconical chamber, a separation chamber, a spinneret feeder of wet material, a layer of polydisperse inert bodies, a drum with tangential coolant inlets and a central cone, characterized in that for the purpose intensification of the drying process and improve the quality of the finished product, the outlet pipe is equipped with a centrifugal classifier with an electric drive and a movable adjusting ring.

When analyzing well-known technical solutions, no solutions were found having features similar to the distinguishing features of the claimed invention. Based on the analysis, we can conclude that the claimed technical solution has significant differences.

In FIG. 1 schematically shows the proposed installation for drying; in FIG. 2 is a section AA in FIG. one; in FIG. 3 is an enlarged view of FIG. one; in FIG. 4 is a section BB in FIG. 3; in FIG. 5 - dispersed composition of the target product: A - in the absence of rotation of a centrifugal classifier; B - during the rotation of the centrifugal classifier at a speed of 1000 rpm.

The drying apparatus comprises a biconical chamber 1, a separation chamber 2, a spinneret feeder of wet material 3. a layer of polydisperse inert bodies 4. a drum 5 with tangential coolant inlets and a central cone 6, a movable adjusting ring 7, a centrifugal classifier 8; the outlet pipe of the waste coolant 10 and the electric drive of the centrifugal classifier 11.

The dryer operates as follows.

Polydisperse inert bodies (round-shaped granules close to spherical, with a density of 1050 ... 2400 kg / m ³ , diameter (3.0 ... 5.1) * 10 ^-3 m (granular polyethylene, polypropylene, polyethylene terephthalate, fluoroplastic) are loaded into the biconical chamber 1 )). The coolant supplied through the tangential inlets of the drum 5 acts on the layer of inert bodies and brings it into suspension. In this case, a dense ring-shaped swirling polydisperse layer of 4 inert bodies is formed. The height of the layer of inert bodies with this organization of the coolant supply is characteristic for devices with a conical shape of the working chamber and polydisperse inert bodies. In the upper part of the dryer, there are predominantly smaller inert bodies. In the lower part of the dryer, mainly large inert bodies are located. The polydispersity of inert bodies allows you to create a stable high swirl layer throughout the conical part of the dryer. Then, a moist material is introduced into the inert body layer through the feeder 3, which is distributed over the surface of the inert bodies and subjected to a convective drying process.

During the continuous process of moisture removal, the dried material exfoliates from the surface of inert bodies, is further abraded in the layer of inert bodies, and is removed from the installation in the form of an air suspension together with the spent heat carrier.

Unlike the prototype, the outlet pipe is equipped with a centrifugal classifier with an electric drive and a movable adjusting ring. The centrifugal classifier has radial plates mounted on the axis (almost a complete analog of the impeller of centrifugal pumps), and an adjustable electric drive with a speed of 500 ... 3000 per minute. Thus, it is possible to use an adjustable swirl of the spent heat carrier inside the drying plant in order to use the principle of centrifugal classification of the dried product to be removed in the waste heat carrier.

When the centrifugal classifier is rotated, the waste heat carrier effluent with the dusty dried material passing through the nozzle 9 is subjected to intense twisting of the classifier blades, which leads to ejection through the windows in the outlet nozzle due to centrifugal force (shown in Fig. 4 by thin arrows) and return to the layer large or heavy (not sufficiently dried) particles of material. Subsequently, these material particles are dried or crushed in a swirling layer of inert bodies. There is also a return to the layer of that part of inert bodies that randomly hit the outlet pipe.

At the same time, on the surface of the classifier blades, large particles of material are subjected to three types of exposure:

a) intense shock;

b) deforming, provided sufficient ductility of the dried product with the formation of new heat and mass transfer surfaces;

c) abrasive;

Inert bodies that get into the waste coolant are also subjected to intensive impact cleaning in the classifier and return to the swirling layer of inert bodies.

In the installation, depending on the properties of the dried material, three types of regulation of the fractional composition of the target product are provided:

a) the movable ring 9 is installed with the possibility of vertical movement along the outlet pipe 10 to control the opening height of the windows, which allows you to adjust the width of the dispersion range of the product returned to the dryer;

b) the vertical movement of the centrifugal classifier allows you to adjust the height of the centrifugal separation zone (shown by a curly bracket in Fig. 3)

c) the adjustable rotation of the centrifugal classifier allows you to choose the necessary mode of operation depending on the density of the target product, the type of particles of the dried material (scaly, fibrous), etc.

A flexible regulatory system allows you to solve many problems affecting the quality of the product.

For example, excessive grinding of the target product is undesirable. In this case, the rotor of the centrifugal classifier is lowered to the upper cut of the windows in the nozzle in order to avoid excessive abrasion of the dried material. If you need to get more finely dispersed phase in the dried product, you can increase the height of the centrifugal separation zone (Fig. 3).

Thus, additional controlled separation of the spent heat carrier can significantly increase the flow rate of the coolant and the number of inert bodies carried in the layer with a corresponding increase in the productivity of the dryer without compromising the quality of the obtained dry material.

Compared with the prototype, with the same dimensions of the dryer, the working zone of the dryer is used more fully, the number of wearable inert bodies increases, the shock-abrasive effect on inert bodies is more actively used, which generally leads to an increase in the productivity of the drying unit.

In addition, the homogeneity of the dispersed composition of the dried material is improved, the resulting product does not contain impurities (inert bodies) due to the processing of the coolant leaving the dryer.

An experimental check was carried out (by analogy with the prototype) when drying lysine. Compared with the prototype with equal overall dimensions, the performance of the proposed dryer is more by 35 ... 38% (depending on the initial moisture content of the product) due to:

- a significant increase (up to 30 ... 35%) of the number of wearable inert bodies in the working area of the installation and the associated increase in the effective area of heat and mass transfer of the apparatus;

- increase in coolant flow without the danger of mass removal of inert bodies from the apparatus when using the cyclone effect of processing the spent coolant;

- use of the cyclone effect on the waste heat carrier in order to return large or high-moisture particles back to the layer for additional processing (grinding and drying).

As shown in FIG. 5, the inclusion in the operation of the installation for drying a centrifugal classifier allows you to actively influence the dispersed composition of the target product. So, in the absence of rotation of the centrifugal classifier, the total size of the dried material is 328 microns (A), and when the centrifugal classifier (B) is working, 247 microns (B). In the dried product, the fraction of the finely dispersed phase increased and the final moisture content in the drying process decreased (mode A - 6.34%, mode B - 4.15%).

Using the proposed dryer provides in comparison with existing designs the following advantages:

- more complete use of the working volume of the drying chamber with a significant increase in the effective area of heat and mass transfer (up to 40%);

- a more active hydrodynamic regime without the risk of removal of inert bodies from the apparatus;

- increase the productivity of the device by 35 ... 40%;

- it becomes possible to process the waste heat carrier with the target product to control such indicators as the dispersed composition and reduce the heterogeneity in the moisture content of the finished product;

- an increase in the degree of working out of the coolant due to the increased height of the swirling layer of inert bodies;

- effective protection of the finished product from contamination with inert bodies.

Claims (1)

Installation for drying pasty materials in a swirling suspended layer of polydisperse inert bodies, containing a biconical chamber, a separation chamber, a spinneret feeder of wet material, a layer of polydisperse inert bodies, a drum with tangential coolant inlets and a central cone, characterized in that in order to intensify the drying process and increase quality indicators of the finished product, the outlet pipe is equipped with a centrifugal classifier with an electric drive and a movable adjusting ring.

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