EP0916065B1 - Device for dewatering and drying suspensions - Google Patents

Abstract

Sludge dewatering and drying assembly comprises: (1) a helical centrifuge in which the sludge is mechanically dewatered to form a sticky mass with a high residual water content, (2) a drying assembly into which the particles are ejected and exposed to vigorous agitation in hot gases resulting in the formation of smaller particles which form a dry particulate bulk solid. The dispersed particles are pre-dried by hot gases before they come into contact with the walls which are kept free of encrustation by baffles and blades generating turbulent gas flow.

Description

The invention relates to a device for dewatering and drying Suspensions according to the preamble of claim 1. Such Drainage and drying device is known from DE-A4332799.

In the known dewatering and drying device with high Speed at the centrifuge ejection, preferably one Solid bowl screw centrifuge, radially hosed moist solid particles in the Size 0.3 - 3mm by suitable means, for example deflection surfaces or by suitable gas flow in the axial direction of the centrifuge and deflected by the Gas flow on a spiral trajectory in the drying room. Here the sprayed solid particles from the drying gas with high Rinsed relative speed and dried. The drying room is a concentric annulus. It is made from the outer dryer housing, the internal rotating drum shell of the centrifuge or an inner that Drum surrounding housing and the two housing end walls are formed. The outer walls of the concentric drying room are fixed and must compared to the rotating parts of the internal centrifuge at least on one Point to be sealed.

The direction of rotation between the centrifuge rotor and the surrounding one Dryer housing must have a high relative speed, a gas differential pressure between inside and outside, as well as displacement movements from thermal expansion and Bridge and endure vibrations. The escape of gases from the Dryer interior to the outside or the entry of false air from the outside in should be prevented or minimized by the seal.

It has now been shown that in particular by thermal expansion Heating processes during the start phase, in the event of vibrations, or at Changes in temperature of the dryer housing the sealing gap between stationary housing parts and rotating centrifuge parts in an impermissible manner changed. This can cause temporary contact with the sealing surfaces and Damage or destruction of the seal.

To avoid this, the gap must be chosen so large that despite Thermal expansions and displacements of the dryer housing do not start non-contact seals comes.

Another disadvantage is that the gap is also caused by vibrations of the Drainage centrifuge inside the dryer changes as the spinning and the non-rotating part of the seal on different seal supports are attached.

Too large a sealing gap is particularly important when the centrifuge dryer is in operation Inert gas atmosphere of great disadvantage, since the false air entry causes the Oxygen content of the inert dryer gas is increased significantly.

In contrast, the object of the invention is in a drainage and Drying device of the type mentioned at the outset, malfunctions, caused by leaks between the dryer housing and the centrifuge avoid constructive measures.

This object is achieved by the characterizing features of Claim 1 solved.

Advantageous embodiments of the invention are specified in the subclaims.

The invention provides for the radial end walls by means of a rotary seal of the dryer housing opposite the rotating surface of the centrifuge seal, whereby the sealing gap can be kept very tight without there is a risk that mechanical contact of the rotating with not rotating active surfaces of the rotary seal comes and damage and Destruction. Another advantage of the rotary seal is that uncontrollable large displacement and expansion movements of the dryer housing during the auto heating and cooling phase of the centrifuge dryer or stronger Vibrations during operation the sealing function despite the narrow gap Do not affect the rotary seal. An escape of internal gases or solids or entry of false air into the inert drying gas is prevented by the narrow Sealing gap almost completely prevented.

Further details and advantages of the invention are provided in the Embodiments explained in more detail with reference to drawings.

Show it:

Fig. 1

a dewatering and drying device (hereinafter referred to as "Centrifugal dryer") with perforated gas guide plates in longitudinal section;

Fig. 2

a centrifuge dryer with baffles in the dryer room in the Longitudinal section;

Fig 3

the dispersion zone of a centrifugal dryer with rotating Cleaning blades for the deflecting surfaces of the dispersed particles;

Fig. 4

the dispersion zone of a centrifugal dryer with rotating Turbulence blades to keep the dryer walls clear;

Fig. 5

a combination of cleaning and turbulence blades for Prevention of incrustations in the dryer interior and Cables;

Fig. 6

a combination of turbulence and transport blades for Keep the dryer interior clear;

Fig. 7

rotating turbulence disks in the dryer room for generation of turbulence vortex rolls for redispersion;

Fig. 8

Deflection surfaces for better dispersion and wider Distribution of the pre-dewatered moist solid particles;

Fig. 9

a centrifuge dryer with housing seal in longitudinal section;

Fig. 10

a non-contact labyrinth seal for one Centrifuge dryer;

Fig. 11

a non-contact thread conveyor seal for one Centrifuge dryer;

Fig. 12

a non-contact thread conveyor seal with a tip thread, and

Fig. 13

a non-contact seal with flat grooves.

The dewatering and drying device shown in Fig. 1 ("Centrifuge dryer") has a solid bowl screw centrifuge in the example shown 1 known type. Instead of the shown Solid bowl screw centrifuges can also be used for dewatering Suspensions, e.g. Slurries, suitable centrifuges, for example Sieve-jack screw centrifuges or 3-phase centrifuges are used in which a phase is to be dried.

The "dewatering centrifuge" or "centrifuge" for short designated solid bowl screw centrifuge 1 has a rotating Drum 2, which is rotatably mounted on roller bearings 3 at its axial ends is. The drum 2 tapers conically at one or both ends and is on Its tapered end is provided with discharge openings 4 which define the discharge zone 5 forms for the pre-dewatered solid 6. The through a tube 7 inside suspension fed to the centrifuge 1, e.g. liquid sludge 8, is in the Centrifuge 1 due to the centrifugal force into a solid 6 and a clarified Liquid 9 separated from the other end of the drum shell 2 from the Centrifuge 1 is hosed into a separate housing 10, the centrate chute.

The dryer surrounding the centrifuge 1 is replaced by an external one Dryer housing 11 and an interior surrounding the rotating drum 2 Housing 12 or by the drum 2 itself, as well as by the two End walls 13 and 14 formed. The drying gas 15 is by a Hot gas shaft 16 introduced tangentially into the dryer room 17, flows around the solid 6 dispersed in the form of particles, that of the impact cone 18 is deflected in the axial direction and transports the drying Solid particles in spiral tracks through the concentric annular space 19 to Output channel 20 of the dryer housing 11. From here flows with the dried solid particles loaded drying gas 21 by a not shown pneumatic delivery line to a solids separator and is there again separated into gas and solid aggregate.

Around the entering hot drying gas 15 in the concentric annular space 19 to distribute evenly and with those deflected by the impact cone 18 and Mixing decelerated solid particles intimately is one example cone-shaped perforated plate 22 installed, which is the hot gas 15th is flowed through. The perforated plate 22 can consist of a conical surface or from several sections with different cone angles, hole shapes, Slits, free opening cross sections or partial solid sheet sections be composed to achieve the effects mentioned. Between the Perforated plate 22, the baffle cone 18 and or the dryer housing 11 can also full or partial annular gaps 23 can be formed in order to prevent undesirable accumulations of solids to prevent. The flow plate 22 through which flow can flow can be a bowl-shaped, cylindrical or flat deviating from the cone Have shape or be composed of different shapes.

In Fig. 2 is a combined centrifuge dryer with built-in guide elements 25, 26 shown in the concentric annular space of the dryer. The centrifuge dryer is constructed from similar components and functions as in Fig. 1. Instead of the perforated plate 22, however, 19 are spiral in the dryer room Baffles 25, 26 installed, which concentrically concentrate the gas flow Force dryer room 19 and short-circuit flows between hot gas inlet 16 and prevent gas outlet 20. The baffle 26 may preferably have a smaller slope of its spiral shape than that in the axial direction arranged behind the baffle 26 baffles 25. With a suitable training of the guide plate 26 (which is arranged in the inlet area of the hot gas 15) it is possible to change the number of guide plates 25, which are shown in the illustration Fig. 2 extend over almost the entire length of the dryer housing 11 reduce or to completely dispense with the guide plates 25. That, for example tangentially entering hot gas 15 (also referred to as "drying gas") is in the discharge zone 5 of the dispersed, moist solid 6th first guided almost completely in the circumferential direction by a guide plate 26, where it is permeated with solid particles. The solids-laden Drying gas 15 is through the spiral baffles 25 in spiral paths is led to the dryer outlet 20. Through the baffles 25 and 26 dead zones not flowed through in the dryer room 19 avoided and everywhere one predetermined minimum transport speed of the drying gas 15 and an equal residence time of the dispersed solid particles forced.

Fig. 3 shows an enlarged view of the discharge zone 5 of a combined centrifuge dryer with two or more rotating cleaning blades 28, which clean the deflecting surface 29 of the impact cone 18 with each rotor revolution. The Pre-dewatered solid 6 is from the screw conveyor to the centrifuge 1 Sprayed edge 30 transported and there at high speed out of the rotor 2 thrown out. The solid particles bounce on the surface 29 of the Impact cone 18, are broken up into smaller particles and braked there. The decelerated particles fly at a greatly reduced speed and in Deflected in the axial direction as a conical solid spray into the Dryer room 19 and there are intensively flushed with hot gas and dried. The cleaning blades 28 are viewed in the direction of rotation behind the solids outlet openings 31 attached to the rotor and are exiting Solid 6 not sprayed. Should serve when very moist or sticky solid particles 6 on the deflection surface 29 some particles not are reflected and stick to the surface 29, they are from the subsequent rotating cleaning blades 28 torn off and in the Tumbled dryer room 19. The high peripheral speed of approx. 60m / s rotating blades 28 also exert a pressure on the surrounding hot gas 15a sucking and promoting effect, with the further consequence that the surrounding hot gas 15a the solid dust located in the dryer room 19 partially promotes in the drop zone 5. The sucked in by the plates 28, dusty hot gas 15a is together with the scraped solid particles depending on the design of the guide surfaces of the cleaning blades radially or flung out conically in the dryer room 19. To intensify the Gas production can have suction and baffle plates 32 attached to the blades become.

In Fig. 4 is the discharge zone 5 of a centrifugal dryer with a steeper angle of the impact cone 18, perforated gas guide plates 22 and rotating Blow blades 33 shown. In contrast to the cleaning blades 28 in FIG. 3, the cleaning action of the blowing blades 33 is not based on a scraping action Effect, but on the blowing effect of the intense gas flow 34 that flows out of the rotating nozzle 33 and onto the surface 29 to be cleaned of the impact cone 18 occurs at a flat angle. Gas production through the Bladder blade 33 is particularly increased by taking suitable measures, such as For example, large intake cross sections at the blade inlet 35, guide elements in the blade and directed blowing at the blade outlet. By the suction effect of the dusty hot gas 15a at the blade entry side 35 and by the outflowing hot gas 36 from the perforated gas guide surfaces 22 becomes the gas flow in the dryer room 19 with the dispersed solid particles 6 kept away from the walls of the dryer housing 11 and more shifted inwards. The from the spray edge 30 of the centrifuge drum 2 Solid 6 that flies out reaches the surface before it strikes 29 of the impact cone 18 in the area of influence of the hot gas 15a, which is dusty and is promoted by the bladder 33. This will the solid particles dried on their surface and with dry Solid dust coated (coating), so that it before contact with the Surface 29 lose their tendency to stick. To further reduce the tendency to stick, the deflection surface can also be coated with a suitable material be such as PTFE, enamel, ceramic, or other anti-adhesive acting materials. The surface 29 can also consist of a perforated surface exist and be ventilated.

5 is a combination of a rotating cleaning paddle 28 and one Bladder blade 33, cooperating with a perforated gas guide plate 22, shown. The surface 29 of the impact cone 18 is cleaned by a rotating scraper 38 in conjunction with the blowing effect of the sucked in hot gas. The emerging bubble jet 34 is not only on the Surface of the impact cone, but also blows tangentially onto the perforated gas guide plate 22. The suction side wall 39 for the hot gas can be set at a slight angle to the circumferential direction or with openings be provided in order to be able to suck in more gas from the bladder blade 33. The Discharge openings 4 of the centrifuge 1 have a conveying effect at their edges on the gas inside the interior 37 of the centrifuge 1. As a result of this Conveying effect from the interior 37 of the centrifuge 1 moist gas sucked out and drawn in hot, dry gas. This will moist solid 6 with the centrifuge 1 even before it is ejected long pre-dried.

6 shows a combination of a turbulence vane 40 for keeping the Dryer room 19 and a cleaning scoop 28 for cleaning the surface 29 of the impact cone 18 is shown. The turbulence vane 40 has one high peripheral speed and generates a strong swirl 41 of Drying gas in the dryer room 19. This does not flow through Dead zones avoided and the incoming drying gas 15 with the dispersed Particles mixed intensely. The cleaning scoop 28 can, as shown, scrape off part or all of the surface 29 of the impact cone or blow off. The blades 28 and or 40 can be rigid or oscillating on the rotor 2 be movably attached.

In Fig. 7, rotating turbulence disks for generation are in the dryer room 19 of tubular vortex rollers 43 installed. The dryer housing 11 is without one fixed inner housing 12 formed, which in some embodiments the drum 2 envelops the centrifuge dryer. The concentric Dryer chamber 19 is therefore outside of a non-rotating cylinder wall and limited on the inside by the rapidly rotating centrifuge drum 2. The rotating one Surface of the drum 2 in connection with the rapidly rotating disks 42 induce in the dryer room 19 a series of turbulent vortex rollers rotating in themselves 43. These turbulence vortex rollers 43 are rotating Surfaces of the drum 2 and the disks 42 driven generate in overall cross-section a high degree of turbulence and even the Flow through the dryer chamber 19 in the circumferential direction. The high degree of turbulence the vortex rollers prevents deposits on the boundary walls of the Dryer housing 11, forcing an intimate mixing of drying gas and the dispersed solid particles and produces a high drying rate for the moist solid particles, combined with an extreme high water evaporation rate based on the dryer volume. The entering Hot gas 15 is rotating through the passage gaps 44 outside Discs 42 and through the toroidal turbulence vortex rollers in his axial movement smoothed over the entire circumference. Instead of rotating disks 42 can also be on the centrifuge drum 2 Elements for generating turbulence rollers are used in the dryer, for example a radial blade ring, axial or radial feed wheels, Club arms or other suitable internals known per se.

8, one or more are on the outside of the rotating centrifuge drum 2 Blade rings 46 attached to generate a high degree of turbulence in the Dryer room 19 and for uniform axial conveyance and control of the Residence time of the drying gas laden with solids. In addition to these functions the blade rings 46 also cause agglomerates in the Dryer room 19. The surface 29 of the impact cone 18 consists of several geometrically composed smooth surfaces. At the impact zone 48 of the pre-dewatered dispersed solid 6, the surface consists of a flat Cone, to which a rounded surface contour 49 adjoins further outside. Due to the flat impact angle of the dispersed moist solid particles 6 on the smooth baffle cone 18 is divided into several smaller ones Particles 47 which favors reflection and further transport. The most The desired greater deflection in the axial direction of flight is carried out further outside sliding on the rounded surface contour 49 of the impact cone 18. By the additional sliding of the divided particles becomes their shot speed in the dryer room 19 additionally reduced and thus the risk of Caking on the walls of the dryer housing 11 is reduced.

The centrifuge dryer shown in Fig. 9 in turn consists of a Centrifuge, in the example shown from a solid bowl centrifuge 1 which is surrounded by an outer housing 11 of an atomizing dryer. Around the centrifuge drum 2, an inner housing 12 is arranged.

The outer dryer housing 11 and the inner housing 12 form the concentric Dryer room 19 through which the drying gas 15 is passed. The Drying gas 15 is fed through the tangential hot gas shaft 16, detects in the region of the discharge zone 5 in the form of a dispersed Particle veil thrown off, dewatered solid, transports the Solid particles with increasing drying in spiral paths the dryer room 19 and reaches the outlet channel as a gas 21 laden with solids 20. The water separated in the centrifuge 1 is in the centrate chute 10 derived.

The outer dryer housing 11 is on the two end walls 13 and 14 sealed against the rapidly rotating centrifuge drum 2. The gap 190 of the rotary seals 160 is formed by the centrifuge drum 2 and the sealing ring 170, which, like the drum pedestals 210 on the base frame 220 is rigidly attached. By fastening the two, the sealing gap 190 forming active surfaces 2 and 170 on the same support 220 is the sealing gap 190 guided precisely and stably. The centrifuge drum 2 also remains Flow through the dryer room 19 with hot gas 15 through the given Suspension cold and does not expand, whereas hot gas 15 flowed through dryer housing 11 strong in the axial and radial directions expands.

The displacement movements of the two housing end walls 13 and 14 are through a gas-tight flexible compensator 180 or an elastic membrane or a sliding link ring 300 opposite the rigidly attached Sealing ring 170 compensated so that the sealing gap 190 is not changed.

Fig. 10 shows in detail a non-contact labyrinth seal for one Centrifuge dryer, with the sealing ring 170 rigidly attached to the frame 220 the axially and radially shifting dryer end wall 14 gas-tight connects a compensator 180. The flexible compensator 180 is e.g. by Tension straps 230 or other fasteners with both the sealing ring 170 and connected to the end wall 14 in a gastight manner.

The sealing gap 190 between the tips 240 of the labyrinth seal and the rotating surface of the centrifuge drum 2 can be very narrow (0.3 - 0.5mm) be held, since the displacement movement of the end wall 14 is not on the Labyrinth seal is transferred.

All non-rotating parts are hatched right, all rotating parts are hatched left.

11 shows a non-contact rotary seal 160 in the form of a thread seal for a centrifuge dryer, e.g. in the dryer room to the right of the End wall 14 has a negative pressure.

The sliding and sliding movements of the front wall 13 and 14 of the dryer during the heating up or cooling down phase of the dryer housing 11 compensated for a sheet metal ring 260, which is sealed by heat-resistant O-rings 270 is and both on the housing end wall 13 and 14 as well as rigid attached sealing ring 170 can slide. The narrow sealing gap 190 as the threaded conveyor seal trained rotary seal 160 caused by the threads 280 in the surface of the centrifuge drum 2 a the negative pressure in Dryer counteracting conveying effect and a gas back pressure that the Prevention of false air in the dryer room 19 prevented. The threads 280 can also be used with a fluid barrier medium such as Water or sealing gas can be filled, which through the threads 280th is passed through.

12 shows a non-contact rotary seal 160 with a pointed thread 310, the rotates with a narrow gap 190 within a soft cylindrical surface 320. The Conveying effect of the thread seal balances the prevailing negative pressure in the Dryer off. The moving dryer housing 11 is by the Setting slide ring 300 balanced in the gap. The sliding block 300 itself is due to heat-resistant O-rings both on the dryer end wall 14 and on rigidly attached sealing ring 170 slidably sealed.

Fig. 13 shows a non-contact rotary seal 160 with flat grooves, which in a soft cylinder liner 320 made of plain bearing materials with a very narrow gap 190 rotates. The displacement movement of the end wall 13 or 14 of the dryer housing 11 is by a resilient in the radial and axial directions Sliding ring 340 balanced.

Claims (11)

1. Device for dewatering and drying suspensions, for example industrial or clarifier sludge, fermenting liquor with a centrifuge, for example a full jacket spiral centrifuge with the suspension is in the form of a liquid mass in the admission zone, and in the ejection zone the pre-dewatered suspension is ejected in the form of a solid with a dry matter content in the region of 15 % weight to 35 % weight as dispersed particles, and with a drying device for convection drying of the ejected solid matter particles, comprising a fixed drier housing (11) surrounding at least partially, the rotating drum (2) of the centrifuge (1) and a hot gas generator, from which the hot gas (15) passes through the fixed drier housing (11) to subject the dispersed solid matter particles to short-term drying of a few seconds' duration in its path to the exit of the drier housing (11), whereby the fixed drier housing (11) is limited on its radial inside by the rotating jacket surface of the centrifuge (1) and on the radial outside by a cylinder wall and on its end sides by radial end walls (13, 14), characterised by the fact that the rotating jacket surface of he centrifuge (1) is sealed off by means of a twin or multi-stage sealing system of rotary seals (160) and flexible or displacing sealing elements (180, 260, 300, 340) against the fixed end walls (13, 14) of the drier housing (11), that on both axial ends of the drier housing (11) a seal (170) is provided in each case in an axial gap with the adjacent end wall (13, 14) of the drier housing (11), the seal (170) is fixed to the same mount (22) as the drum bearing blocks of the centrifuge drum (2) and, with a gap (190), grips the rotating jacket surface of the centrifuge (1), whereby the sealing gap (190) is sealed by a rotary seal (160), and the axial gap between each seal (170) and the adjacent end wall (13 or 14) of the drier housing (11) is sealed offby the flexible or displacing sealing elements.
2. Device as per claim 1, characterised by the fact that the sealing gap (190) is sealed off without contact by means of a labyrinth seal or thread feed seal.
3. Device as per claim 1, characterised by the fact that the rotary seal (160) is constructed such that it forms a dynamic gas counter-pressure with a pressure head between the inside and outside of the drier housing (11).
4. Device as per claim 1, characterised by the fact that in one part of the sealing gap (190) of the rotary seal (160), a liquid barrier medium is provided.
5. Device as per claim 2, characterised by the fact that the web (240) ofthe labyrinth seal is made of a soft material or is constructed as a sealing brush, with a very narrow sealing gap (190).
6. Device as per claim 2 or 5, characterised by the fact that the sealing gap (190) can be changed by contact pressure on the labyrinth seal.
7. Device as per claim 1, characterised by the fact that a low oxygen barrier gas is introduced into the sealing gap (190).
8. Device as per claim 1, characterised by the fact that the a contacting sliding ring seal is used as a rotary seal (160).
9. Device as per one of claims 1 to 8, characterised by the fact that the drier housing (11) can be displaced by means of a flexible diaphragm (180) with the seal (170) and is joined so that it is gas-tight.
10. Device as per one of claims 1 to 8, characterised by the fact that the drier housing (11) can be displaced by means of a link slide ring (300) with a seal (170) and is connected so that it is leaktight.
11. Device as per claim 10, characterised by the fact that the link slide ring (300) is sealed so that it can displace, by means of heat-resistant O-ring seals (270) against the drier housing (11) and the seal (170).

Images