DE2362725A1 - PROCESS AND DEVICE FOR CONTINUOUS DRYING OF DAMP GRILLED MATERIAL - Google Patents

Description

KNAPSACK AKTIENGESELLSCHAFT

K 1092

Method and device for the continuous drying of moist, granular material

The present invention relates to a method for the continuous drying of moist granular material, in particular wet coke, the granular material being passed through a rotating drum in cocurrent with flame gases and wherein the dust is separated from the exhaust gases leaving the rotating drum, and a device to carry out the procedure according to the invention .

It is known to dry granular material by making it weak with respect to the horizontal inclined drum rotating in direct current with 1 to 15 revolutions per minute about its longitudinal axis passing through a heating medium serving as a desiccant. The moist material becomes more constant over time Amount given with the help of a metering device, while the dried material is in a dropout housing got. The dust-laden exhaust gas is blown by a fan at the head of the dropout housing sucked off and after 'dedusting with the help of a cyclone separator. discharged into the open.

To enlarge the surface of the product in contact with the desiccant contains the rotating drum internals, the particularly effective internals in their Construction are relatively complicated - (see. "Ullmann & Encyklopadie der technischen Chemie", III. Edition, Volume 1, Munich-Berlin 1951, pages 594 to '596). - 2 -

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The disadvantage of the known device is that the dedusting of the exhaust gas from the drying drum takes place with a cyclone separator. Even if a cyclone separator is insensitive to the exhaust gas temperatures, the separation, in particular the fine dust fraction, only takes place in it to a degree which no longer meets today's requirements with regard to environmental protection. A satisfactory dust separation also of the single components is achieved with an electrostatic precipitator. On the one hand, however, an electrostatic precipitator only works optimally just above the dew point, while on the other hand, to avoid caking in the dust outlets of the electrostatic precipitator, which is caused by the condensation of vapors, the exhaust gases to be introduced into the electrostatic precipitator must have a temperature sufficiently above their dew point. Taking into account the heat losses in the gas supply lines to the electrostatic precipitator and in itself an exhaust gas temperature at the outlet end of the drying drum of about 120 ⁰ C is necessary in the dust removal -of water vapor-containing exhaust gases. At higher temperatures, there is namely no stable electric field between the spray and collecting electrodes with a uniform electrode emission sufficient for dust separation. If flashovers take place, for example when coke is dried, dust can ignite and fire in the electrostatic precipitator, which among other things burns out the wires of the spray system and makes them unusable.

If the flame gases serving as desiccants are allowed to enter the rotating drum at such a temperature that the exhaust gas leaving the rotating drum is not hotter than 120 ° C, it is necessary to have complicated internals in the rotating drum to achieve a dry product with about 1 weight of water to use, to increase the number of revolutions of the rotary drum and to let the goods stay in the rotary drum for quite a long time. -3-

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These measures result in a generally undesirable increase in the fines content in the dried material. Furthermore the increase in the number of revolutions of the rotary drum also increases the wear and tear on the fixtures, It must be taken into account that the production and assembly of complex internals is expensive. About that In addition, complex fixtures are usually also recognized because of the poor accessibility Wear damage can hardly be repaired.

It is therefore an object of the present invention to provide a To create a method and a device for the continuous drying of moist granular material, wherein the disadvantages mentioned do not occur, but rather the rotating drum with a low number of revolutions is operated and is equipped with simple, easily accessible fixtures for repair purposes, wherein continues to remain in the rotary drum for only a short time and the. Exhaust gases are still below optimal Conditions can be cleaned with an electrostatic precipitator. This is achieved according to the invention by that the flame gases enter the rotary drum at such a temperature that the temperature difference between the exhaust gases and the dried granular material at the exit of the rotary drum is at least 80 C; that the dusty exhaust gases after their exit from the rotary drum a trickle layer of the same flow through moist granular material; that the layer thickness and the cross section of the trickle layer as well as -das The grain spectrum of the moist, granular material brought into the trickle layer can be selected in such a way that in the rotating drum a vacuum of 5 to 20 mm WS, preferably 10 mm WS, is maintained and that the Exhaust gases leaving the trickle layer can be cleaned with the help of an electrostatic precipitator.

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The method according to the invention can optionally also be characterized in that

a) the temperature difference between the exhaust gases and the dried granular material at the outlet of the rotary drum is 150 to 20O ⁰ C, preferably 180 ⁰ C,. .

b) the coarser part of the moist, granular Good is used in the trickle layer, while its finer-grained portion in the Rotating drum is introduced,

c) the trickle layer is continuously renewed,

d) the temperature of the exhaust gases after flowing through the trickle layer as a measure of the speed serves to renew the trickle layer,

e) a vertical trickle layer is used.

An apparatus for carrying out the method will first be explained with reference to the accompanying drawings. Show it

Figure 1 is a side view of the entire device; FIG. 2 the failure housing in the view according to FIG

1;

FIG. 3 shows the dropout housing perpendicular to the view of FIG. I;

FIG. 4 shows a star installation for a rotary drum;

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FIG. 5 shows a cross installation for a rotary drum.

A rotary drum x 1 has a combustion chamber at one end thereof 2 with supply line 3 for fuel gas and fans (4, 5) for primary and secondary air. In this A material feed pipe 8 also opens at the end, which is fed via a transport device provided with a metering element 24 7 with an acentric filling nozzle 14 having wet material bunker 6, which is called " Pants bunker is formed, is connected. With its opposite end, the rotary drum 1 opens into one Dropout housing 10 a.

In the dropout housing 10 there are horizontally one above the other arranged rods 11, between which heaped moist granular material forms a trickle layer. Included If the moist, granular material passes through an inlet pipe 18, which is provided with a shut-off valve 23 via a Slide 9 is connected to the Naögutbunker 6, into the space between the rods 11. The trickle layer supports down on a discharge element 12. If the discharge element 12 is a discharge table, it will be moved with the help of a rod 19, which penetrates the wall of the dropout housing 10 and which with a Reciprocation: exporting aggregate is connected At its lower end, the dropout housing 10 has a gate valve 21 and a pendulum flap 22 provided drop tube 25. At the top of the dropout housing 10 there is an exhaust pipe 13 in which the sensor of a temperature measuring device (TI 1) is arranged is. The sensor of another temperature measuring device (TI 2) is located in the failure housing 10 and ends above of the discharge element 12 in the granular material.

A fan 16 and an electrostatic precipitator 17 are arranged behind the discharge housing 10 in terms of gas flow, whereby in the connection line between the outlet

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case case 10 and. a throttle valve 15 for the fan 16 is located.

The internals according to Figures 4 and 5 each consist of lifting strips 26 which are attached to the inner wall of the rotary drum

I are attached. In the rotary drum 1 according to Figure 4 is central a six-jet star-shaped body 27 is arranged, while in the rotary drum.1 according to Figure 5 a number of cruciform, at their ends angled bodies 28 is arranged on the same tendons.

In detail, a device for performing the inventive Process, which consists of a rotating drum provided with internals, a wet material bunker and a connecting line with a metering device for moist, granular material as well as from a gas flow connected upstream of the rotary drum Combustion chamber and a downstream gas flow Dust removal device with fan, be characterized in that the discharge end of the Rotary drum 1 ends in a dropout housing 10, in which there are bars arranged horizontally one above the other

II a trickle layer supported on a discharge element 12 from moist granular material located; that the accumulation, training facility. consists of an electrostatic precipitator 17 and that the failure housing 10 has an exhaust pipe 13 located downstream of the trickle layer in terms of gas flow, in which a temperature measuring device TI 1 is arranged and which is connected to the dust removal device.

Furthermore, this device can also be characterized in that

f) one at the top of the dropout housing 10 above the . The feed nozzle 18 located in the trickle layer with the wet material bunker 6 via a gate valve 23 provided slide 9 is connected;

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g) the discharge element 12 from the one in the exhaust pipe 13 of the dropout housing 10 arranged temperature measuring device TI 1 is controlled ;.

h) in the dropout housing 10 above the discharge element 12 a temperature measuring device TI 2 is arranged;

i) the discharge element 12 is a discharge table which is movable on rollers 20; .

j) the discharge table via a rod 19 with a back and forth Floating aggregate is connected;

k) the rod 19 penetrates the dropout housing 10;

1) the discharge element 12 is a cellular wheel;

m) the discharge element 12 is a vibrating chute.

With the help of the method according to the invention, it is possible, through appropriate continuous renewal of the trickle layer of moist, granular material, to lower the temperature of the exhaust gas to such an extent that the exhaust gas can be cleaned with the aid of an electrostatic precipitator under optimal conditions, that is to say that exhaust gas temperatures at the outlet of the failure housing of, for example 120 ⁰ C can be reached.

The rotary drum can be used to achieve the greatest possible temperature difference between the desiccant and the goods to be dried are exposed to particularly hot flame gases, which means that there is a small temperature difference Complicated built-in components required in the rotary drum can be dispensed with. In this case it is it is also possible to use the rotary drum with a small

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operating speed and the residence time of the goods by installing, for example, conveyor blades in the rotary drum, reducing the undesired size reduction of the granular material used is prevented by increasing the fines content.

Equipping a rotary drum with simple fixtures, for example with a star body (see FIG. 4), brings with the advantage that, in addition to the lower manufacturing costs of this body, compared to complicated internals, such as cross bodies (see FIG. 5), the trickle resistance is lower in the case of simple fixtures and therefore less Throughput through the rotary drum per unit of time is greater. In addition, if the flow resistance is lower, the Less wear on the fixtures. Since, to the same extent as a high flow resistance, great wear and tear due to the internals, also the abrasion of the granular material and thus the unwanted dust accumulation is increased the. Reduction of the trickle resistance also in this respect -really important.

Some of the dust and grains blown through the trickle layer fall in the area below the exhaust pipe 13 from the gas stream and are continuously dumped together with the granular material from the trickle layer Discharge organ 12 discharged. To ensure that the hot exhaust gases leaving the rotary drum 1 actually pass the trickle layer to cool them down, it is necessary that the material layer AB in the dropout housing 10 is always greater than the layer thickness of the trickle layer AC (see Figure 2).

The rotating drum 1 and the trickle layer piled up between the rods 11 are expediently made of a common one Naßgutbunker 6 acted upon. It is advantageous

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liable to design the wet goods bunker 6 as a trouser bunker and to equip it with a filling nozzle 14 (see FIG. 1), which- is arranged eccentrically or to the side of the bunker. This ensures that when the wet material bunker 6 • the moist grainy. Good is partially classified, with coarser on the side opposite the filling nozzle 14 Good accrues, while the good that collects below the filler neck 14 is finer grained. So that above The coarser material accumulating in the chute 9 is fed to the trickle layer, while the finer material is fed into the rotating drum via the transport device 7 and the material feed pipe 8 1 is initiated.

The method according to the invention is now based on the example the drying of wet coke explained.

Example 1 (according to the state of the art)

A wet coke with 16 % by weight of water and this grain analysis was used:

3 % 0 to 1 mm

4.% 1 to 6 mm ■ 12% 6 to 10 mm 81 % 10 to 20 mm

A rotary drum 12 m long and 2.8 m in diameter was used used, which rotated at 3 revolutions per minute. The fixtures consisted of lifting strips and a centrally arranged one six-pointed star-shaped body according to the figure

Carbide furnace gas (mainly carbon monoxide) was used for heating with a heat content of about 2500 WE / m ^; each t wet

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80 m ^ of this was spent on coke. The heat demand per t Wet coke to be dried was therefore 200,000 WE.

The throughput of wet coke through the rotary drum was 18 t / h; the dried'Koks had a residual moisture content of 0.8 wt right%.

The temperature of the rotary drum leaving coke was 110 ⁰ C, the temperature of the exhaust gas at the outlet of the rotary drum 180 ⁰ C. _

The dried coke had this Korhan analysis:

11 % 0 to 1 mm

6% 1 to 6 mm

11 % 6 to 10 mm

72 % 10 to 20 mm

The abrasion was accordingly 10 %. Example 2 (according to the invention)

A wet coke with 16% water and this was used Grain analysis:

3 % 0 to 1 mm

4 % 1 to 6 mm 12 % 6 to 10 mm 81% 10 to 20 mm

A rotating drum 12 m long and 2.8 m in diameter was used, which rotated at 1.7 revolutions per minute. The internals consisted of lifting strips and a centrally arranged six-ray star-shaped body as shown in the figure

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The trickle layer through which the exhaust gases from the rotating drum were passed had an area of 6 square meters and a thickness of 40 cm on.

Carbide furnace gas with a heat content of around 2500 WE per m was used for heating; per t of wet coke were 60 nc expended. The heat requirement per t of wet coke to be dried was therefore 150,000 WE.

The other data are summarized in the following table:

1 Throughput
/ -t / h_7 Turn
drum Trickle
stitches total Water content
the dried one
th coke l ~% _7 18th 6th 24 Temperatures of the coke
after drying / ~ ° C_7 0.5 2.5 1.0 Gas temperature before Rie
selschicht ^ "c_7 120 100 Gas temperature according to Rie
selschicht l ~ c_7 300 Average grain diameter
ser l_ ~ mm_J 120 Grain content <10 mm 14th 17th 11 1 -

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The dried coke had this grain analysis

5 % 0 to 1 mm

5% 1 to 6 mm

13% 6 to 10mm

77% 10 to 20mm

The abrasion was therefore 3 %.

Using the method according to the invention could the heat requirement per t of coke to be dried can be reduced by a quarter from 200,000 residential units to 150,000 residential units.

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Claims (15)

Patent claims: 1) Process for the continuous drying of wet granular material, in particular of Naßkoks, wherein the granular material is passed in co-current with the flame gases through a rotary drum, and wherein the dust is separated abge _T from the rotary drum verlässenden exhaust gases, characterized in that the flame gases with such a temperature into the rotary drum happen that the temperature difference between the exhaust gases and the dried granular material at the outlet of the rotary drum is at least 80 ⁰ C; that the dusty exhaust gases, after exiting the rotary drum, flow through a trickle layer of similar moist, granular material; that the layer thickness and the cross section of the trickle layer as well as the grain spectrum of the moist, granular material introduced into the trickle layer are chosen so that a vacuum of 5 to 20 mm water column, preferably 10 mm water column, is maintained in the rotating drum and that the trickle layer is maintained leaving exhaust gases can be cleaned with the help of an electrostatic precipitator. 2) Method according to claim 1, characterized in that the temperature difference between the exhaust gases and the dried, granular material at the exit of the rotary drum is 150 to 200 ⁰ C, preferably 180 ⁰ C. 3) Method according to claim 1 or 2, characterized in that the relatively coarse fraction of the wet granular material is used in the Rieselschicht, while its fine-grained fraction is introduced into the rotary drum. - 14 - 509826/0813 4) Method according to one of claims 1 to 3, characterized in that the trickle layer is continuously renewed. 5) Method according to one of claims 1 to 4, characterized in that the temperature of the exhaust gases after flowing through the trickle layer serves as a measure of the speed of renewal of the trickle layer. 6) Method according to one of claims 1 to 5, characterized in.-That a perpendicular Rieselschicht is used. 7) Device for carrying out the method according to one of claims 1 to 6, consisting of a rotating drum provided with internals, a wet material bunker and a connecting line with a metering device for moist granular material as well as a combustion chamber upstream of the rotating drum in terms of gas flow and a dedusting device with fan downstream in terms of gas flow , characterized in that the discharge-side end of the rotary drum (1) ends in a dropout housing (10) in which there is a trickle layer of moist, granular material supported on a discharge element (12) between bars (11) arranged horizontally one above the other; that the dedusting device consists of an electrostatic precipitator (17) and that the discharge housing (10) has an exhaust pipe (13) located behind the trickle layer in terms of gas flow, in which a temperature measuring device (TI 1) is arranged and which is connected to the dedusting device. 509826/0813 8) Device according to claim 7 , characterized in that a feed nozzle (18) located at the upper end of the dropout housing (10) above the trickle layer is connected to the wet material bunker (6) via a slide (9) provided with a gate valve (23) . 9) Device according to claim 7 or 8, characterized in that the discharge element (12) is controlled by the temperature measuring device (TI 1) arranged in the exhaust pipe (13) of the failure housing (10). 10) Device according to one of claims 7 to 9, characterized in that a temperature (TI 2 is arranged) in the failure case (10) above the discharge member (12). 11) Device according to one of claims 7 to 10, characterized in that the discharge element (12) is a discharge table, 'which is movable on rollers (20). . ■ 12) Device according to claim 11, characterized in that the discharge table is connected via a rod (19) to an aggregate which executes back and forth movements. 13) Device according to claim 12, characterized in that the rod (19) penetrates the failure housing (10). 14) Device according to one of claims 7 to 10, characterized in that the discharge element (12) is a cell • wheel is. - 16 50982 67 0813 15) Device according to one of claims 7 to 10, characterized in that the discharge element (12) is a vibrating channel. 509826/08 13