RU2263259C2 - Drier-mixer - Google Patents

Abstract

FIELD: drying of suspensions.

SUBSTANCE: drier-mixer is used for drying suspension of ultra-dispersed fraction of ammonium perchlorate having sizes of particles less than 2 mcm when preparing mixed solid rocket fuel as well as for drying other suspensions out which suspensions have disperse matter and disperse phase. Drier-mixer has to be rotating drum provided with warming-up jacket in form of a cylindrical case provided with four separated spaces. Each edge side is protected with wall being perpendicular to axis. Separated part is closed by segment walls disposed symmetrically at angle. Tube with jacket is inserted into one hollow pivot. The tube ends with closed end of elastic pipe having slits along the length. Knee-shaped nozzle composed of concentric pipes passes the second pivot. Internal pipe of the nozzle is connected with cone-shaped perforated tip. Nozzle is made for rotation for 180°.

EFFECT: improved efficiency of drying and mixing; stopped clod forming; reduced losses.

2 dwg

Description

The invention relates to a technique for drying a suspension of an ultrafine fraction of ammonium perchlorate with a particle size of less than 2 microns in the manufacture of mixed solid rocket fuel. The apparatus can be used for drying other suspensions containing a dispersion medium and a dispersed phase.

The manufacture of the above fraction is carried out by grinding ammonium perchlorate in a liquid medium, followed by its removal by drying. Ammonium perchlorate is a highly soluble substance in water and readily absorbs moisture from ambient air. For this reason, it is not possible to obtain an ultrafine fraction of ammonium perchlorate by dry grinding, since there is a strong aggregation of particles. Ultrafine grinding is achieved only in a liquid medium in the presence of a surfactant. As the liquid phase, substances that do not dissolve ammonium perchlorate are used.

Spray dryers are widely used for drying suspensions (see MV Lykov's book "Drying in the Chemical Industry", Moscow, Chemistry, 1970).

However, their use for drying a suspension of an ultrafine fraction of ammonium perchlorate is difficult due to:

- clogging of spray nozzles or discs with easy aggregating powder;

- the danger of getting sensitive to mechanical stress ultrafine fraction of ammonium perchlorate in the seal of a rapidly rotating disk;

- the difficulty of condensation emerging from the dryer vapor of a volatile liquid medium from a mixture of it with air;

- complications of dust cleaning devices associated with the entrainment of particles with a coolant;

- the impossibility of combining drying and mixing in one apparatus.

The indicated disadvantages are deprived of the apparatus for drying and mixing materials according to UK patent No. 1168691, class F ₄ G; B1 _c , F ₄ V (F26 _c ) declared 02.07.68, adopted by the authors for the prototype. The apparatus of the aforementioned patent has a rotating horizontal cylindrical drum with a heating jacket, inside of which longitudinal movable scrapers are located to loosen the material and prevent it from sticking to the wall. Material is loaded from one end of the drum and unloaded from the other.

In this apparatus, effective mixing is not achieved, since counter flows of particles in the axial direction are not created, there is no device for spraying the suspension, which helps to improve mass transfer and eliminate clumping. Moving scrapers do not fully ensure the destruction of small lumps. The presence of rubbing pairs inside the drum creates a certain danger when processing the ultrafine fraction of ammonium perchlorate, which is sensitive to mechanical influences. Good mixing of this fraction is extremely necessary in order to obtain reproducible ballistic and physico-mechanical characteristics of mixed solid rocket fuel.

The technical task of this invention is to improve the drying and mixing efficiency in the manufacture of an ultrafine fraction of ammonium perchlorate, eliminating its clumping, increasing the safety of the drying process, and reducing the loss of liquid medium.

The technical result is achieved due to the fact that at the heated hollow horizontal drum, which is a cylinder with four cut off volumes, the ends are closed by walls perpendicular to the axis of the drum, and the cut off part is closed by segmented walls symmetrically angled, a pipe with a jacket is inserted into one of the hollow trunnions ending with an elastic hollow tube with slotted slots along the length for feeding the suspension into the apparatus, a knee-shaped nozzle from concentrically arranged passes through another hollow pin dix pipes, the inner pipe ends perforated tip nozzle is turning, is rotated in the direction of rotation by an angle equal to the angle collapse powder while rotating the drum, and during drying it is vertically set up a conical tip.

The aforementioned design of the end walls of the drum provides cross-movement of the ultrafine fraction of ammonium perchlorate and its good mixing.

An elastic nozzle in the suspension feed line promotes fine atomization of the suspension and reduces the tendency to clumping. The elasticity of the nozzle eliminates clogging of the slots due to deformation of their edges with increasing pressure of the suspension in the nozzle. Before the suspension is started, elastic bodies are loaded into the apparatus in the form of cylinders. They are intended for the destruction of possibly forming lumps during the drying process. At the beginning of the drying process, they exclude direct contact of the suspension on the walls of the apparatus, preventing sticking and crusting.

The conical shape of the nozzle tip eliminates the possibility of pinching of the elastic bodies between the wall and the nozzle with a rotating drum.

When the drum rotates, the ultrafine fraction of ammonium perchlorate is carried away in the direction of rotation due to friction forces and at a certain angle of rotation, a collapse occurs.

To ensure complete discharge of the product, the nozzle is turned in the direction of rotation by an amount equal to the angle of collapse. The lowest concentration of the ultrafine fraction of ammonium perchlorate in the mixture in the apparatus will be in the upper zone. Therefore, to reduce product entrainment during the drying process, the nozzle is lifted vertically upward so that its tip is in the upper zone of the apparatus.

The dryer-mixer (see Fig. 1) consists of a horizontal hollow drum 1 with a heating jacket 2. In the end walls there are hollow trunnions 3, 4 based on bearings 5 mounted in the drum drive and nozzle support. The rotation of the drum is carried out through the gear 6. The coupling 7 serves to supply hot water to the jacket and drain it. A fixed tube 8 is inserted into the trunnion 3 for feeding the suspension, ending with an elastic nozzle 15 with slots 16 located along the length of the drum (see Fig. 2). Through the pin 4, a rotary knee-shaped nozzle 10 of two concentric pipes, supported by a bearing 11, is passed. The nozzle is rotated by a pneumatic cylinder using a lever 12. The end face of the nozzle 10 with a conical tip 9 is located near the drum wall, thereby minimizing the gap between the wall and the tip tip when rotation of the apparatus. The drum is partially filled with elastic bodies 14, for example of polyurethane, which does not interact with the components of the suspension.

The device operates as follows. Elastic bodies are loaded into the drum, after which they include the rotation of the drum and the supply of water to the shirt. Then the nozzle is raised to the upper position and the flow of the suspension is started by the pump, which is sprayed through the nozzles. The inclined end walls of the drum, spraying the suspension through nozzles, the presence of elastic bodies intensify the drying and mixing process, and prevent crust and lump formation. In the case of clogging the nozzle slots with dried powder, their flow area decreases, which causes an increase in pressure in the nozzle and deformation of the edges of the slots, as a result of which self-cleaning occurs. Vapors of the liquid medium are removed through the holes of the nozzle tip from the upper, least dusty zone of the drum, which reduces the entrainment of particles of the ultrafine fraction of ammonium perchlorate with vapors. After filling the drum with a dry ultrafine fraction of ammonium perchlorate by 0.3-0.4 of the drum volume, the nozzle is lowered to the lower position. To unload the powder, compressed dried air is supplied into the annulus of the nozzle, which, when entering the apparatus through a layer of powder, loosens it with the formation of aerosol. The aerosol mixture through the nozzle openings enters the central tube of the nozzle and is discharged from the apparatus to the precipitator, where the ultrafine fraction of ammonium perchlorate is separated from the air. Powder unloading is carried out with continuous rotation of the drum, due to which, as well as a small gap between the tip tip and the drum wall, the unloadable residue is minimized.

The application of the invention allows to achieve the following advantages:

- speed up the drying and mixing processes;

- eliminate crust and lump formation:

- provide security;

- eliminate the clogging of the spray nozzle;

- to ensure the completeness of unloading of the dried ultrafine fraction of ammonium perchlorate;

- high technology in the manufacture of dryer-mixer.

Testing the model version of the dryer-mixer showed its reliability and confirmed the above advantages.

Claims (1)

A dryer-mixer in the form of a rotating horizontal drum with a heating jacket, characterized in that the drum is a cylinder with four cut-off volumes, each end surface is closed by a wall perpendicular to the axis of the drum, and the cut-off part is closed by segmented walls symmetrically positioned at an angle, into one of the hollow trunnions a pipe with a jacket is inserted, ending with a closed end with an elastic tube with slots along the length for feeding the suspension, a knee-shaped nozzle of concentrates passes through another trunnion tubes, the inner pipe is connected to a conical perforated tip, the nozzle is made rotatable, which is set to the side of rotation at an angle equal to the angle of powder collapse during rotation of the drum, and in the process of drying they are positioned vertically with the conical tip up.

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