RU2250427C2 - Device for spraying drying - Google Patents

Abstract

FIELD: chemical industry.

SUBSTANCE: drying of sprayed agent is carried out in the atmosphere of the vapor of evaporating liquid inside the heated pipes of small diameter, and dispersed particles of the agent are caused to flow forwardly through pipes.

EFFECT: improved design.

3 cl, 2 dwg

Description

The invention relates to the field of chemical technology and can be used for high-speed concentration or spray drying of solutions and suspensions to obtain a conditioned process steam or with the possibility of low-temperature drying of thermolabile substances under high vacuum conditions.

Spray drying installations are known in which liquid products are dispersed by mechanical or pneumatic nozzles or spray disks inside the drying chamber, and the resulting fine particles are dried by feeding air preheated to high temperature into the chamber, followed by separation of the dried product from moist hot air in the drying chamber chamber and dust collecting devices. The disadvantage of this type of installation is the high consumption of heated air for drying and, as a result, the significant size of the air heater, drying chamber and dust collecting devices, the danger of explosion when drying combustible materials, as well as the significant overrun and difficulties in recovering the heat spent on the process ("Food Drying Units" Products: Handbook. "Grishin MA and other Moscow," Agropromizdat, 1989).

The aim of the invention is to significantly reduce the overall dimensions of most apparatus, providing the possibility of safe drying of combustible and easily oxidizable materials, reducing heat consumption for drying and ensuring the possibility of almost complete recovery, as well as creating the possibility of conducting the process of low-temperature spray drying of heat-sensitive materials under high vacuum conditions.

This goal is achieved by the fact that the drying of the particles of the sprayed product is carried out in an atmosphere of vapor of an evaporating liquid inside highly heated pipes of small diameter, and the movement of the dispersed particles of the product through the pipes is carried out at a high translational speed.

The particles of the atomized product are dried in an atmosphere containing only vapors of liquids capable of evaporation from the product and not containing significant quantities of extraneous gases and substances (oxygen, nitrogen, carbon dioxide, etc.). Moreover, these vapors inside the pipes can appear (form) both due to the evaporation of the liquid (s) from the sprayed product, and due to the introduction of one or more liquids contained in the product into the pipes of the finished steam.

In a preferred embodiment of the apparatus, the pipes are heated by an open flame of the burners in a horizontally located combustion chamber with a gradually increasing step between the burners.

The dispersion of the liquid product is preferably carried out by introducing high pressure steam into the spray head located at the beginning of each pipe. The introduction of high-pressure steam for spraying the product and the formation of the initial translational movement of the vapor is a desirable condition in relation to drying the product with a low content of removed liquid, or prone to sticking.

The diameter of the drying tubes as the dispersed product moves from the spray heads to the dust collecting device preferably increases smoothly or stepwise.

Using the claimed invention will allow to obtain the following technical result.

The installation makes it possible to obtain, along with concentrated or dried product, also conditioned process steam with a high heat content, which can be used for almost complete recovery of the heat spent on drying the product.

Drying in an atmosphere of a vaporizing liquid allows you to dry flammable and easily oxidizable materials without the risk of explosion and without the cost of a neutral drying agent (nitrogen or carbon dioxide) for the drying process.

Due to the finely dispersed state of the dried substance, its temperature during the process of moisture removal remains close to the temperature of the evaporating liquid, despite the much higher temperature of the heating pipes and the surrounding particles of superheated steam. The absence of dilution of the steam released during the drying process with air or neutral gas allows one to drastically reduce the overall dimensions of the apparatus required to separate the dried product from the steam and makes it possible to carry out the drying process under conditions of high vacuum, which in turn allows for high-speed concentration or spraying drying materials that are particularly sensitive to high temperatures, without loss of quality.

The invention is illustrated by drawings, where figure 1 shows the principle of operation of the spray head; figure 2 shows the installation diagram as a whole.

The construction of the installation consists of a bundle of drying pipes 5, placed inside a multi-section combustion chamber 7, in which the natural gas supplied through the burners 8 is combusted. For exhaust gases, a smoke exhauster 9 and a common chimney 10 are provided, in which additional heat recovery of the flue gases is preferably performed .

At one end of the drying tube bundle there is a block 11 of spray heads, each of which enters into a separate tube, the other end of the tube bundle enters a cyclone type dust collector 12 with product collector 13. A centrifugal scrubber 14 is provided for additional purification of steam from the fine particles of the product.

The installation is carried out as follows.

The liquid product 1 to be dried passes under pressure into the middle part of the channel 2 of the spray head 3, through which saturated high-pressure steam 4 flows at a transonic speed, mixes with it, accelerates and disperses, then the resulting vapor-liquid mixture leaves the spray head at high speed pipe 5, after which its speed decreases, but still remains high.

The sticking of finely dispersed liquid particles to the inner walls of the heated pipe is prevented by both the high translational velocity of the liquid particles and the vapor surrounding them, and the steam cushion that occurs near the particles due to the release of steam from them in the predominant direction to the strongly heated wall when the particles approach the latter.

In order to prevent product particles from sticking to the pipe directly in the area of the spray head, a part of the supplied steam 4 is introduced through an annular gap 6 between the pipe 5 and the spray head 3.

Further translational movement of the product particles along the pipe 5 is carried out both due to the steam stream introduced into the spray head, and due to the steam stream generated from the liquid component of the particles under the action of heat transferred to the particles from the pipe walls by thermal convection and thermal radiation. To reduce the flow rate of the vapor-liquid mixture constantly increasing under the action of the generated secondary steam, a constant or stepwise increase in the pipe diameter is provided as the flow moves from the spray head 3 to the cyclone dust collector 12.

To reduce the influx of heat through the walls of the pipes as the particles are dried, it is planned to reduce the degree of heating of the pipes by reducing the number of burners 8 in the last sections of the multi-section combustion chamber 7.

The effluent from the pipes enters a cyclone dust collector 12, in which it is separated into a dried product 15 and low-pressure steam 16. The steam, if necessary, undergoes additional wet cleaning in a centrifugal scrubber 14 and is used in the technological process to recover the spent heat, and the separated product is additionally Dried and used as intended.

If it is necessary to conduct the drying process in a low temperature mode, the centrifugal scrubber 14 is replaced by a condenser with a vacuum pump, as a result of which the entire process described above is carried out under conditions of strong vacuum.

Claims (4)

1. Installation of spray drying containing spraying and dust collecting devices, characterized in that the drying of the particles of the sprayed product is carried out in an atmosphere of vapor of evaporating liquid inside the heated pipes, and the movement of the particles of the product through the pipes is carried out at a translational speed. 2. Installation according to claim 1, characterized in that the spraying of the liquid product is carried out by introducing high pressure steam into the spray head located at the beginning of each pipe. 3. Installation according to claim 1, characterized in that the heating of the pipes is carried out in the combustion chamber by the flame of the burners installed with a gradually increasing step between them. 4. Installation according to claim 1, characterized in that the diameter of the drying tubes increases as the product moving along them is dried.

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