AT524558A4 - Processing of starting materials containing iron oxide and phosphate - Google Patents

Abstract

In a device (1) for processing starting materials containing iron oxide and phosphate, in particular waste materials such as sewage sludge, dry sewage sludge, sewage sludge ash, animal meal and/or bone meal and phosphate-containing metallurgical slag and dust and rolling mill scale, comprising a refractory material (46 ) lined combustion chamber (2), a feed device (3) connected to the combustion chamber (2) for the educts, a slag sump (4) at a lower end (2a) of the combustion chamber (2) and an extraction device (5) for extracting product gases from the combustion chamber (2), wherein the feed device (3) has a vortex chamber (7) arranged along a vertical axis (6) with at least one gas inlet (15 ) comprises, wherein in the vortex chamber (7) along the vertical axis (6) a lance (26) for ejecting an oxygen-containing gas is arranged, interspersed in a region axially above the at least one gas inlet (15), a screw conveyor (18) for the starting materials, the vortex chamber (7) arranged in a screen tube (17) provided with holes (16).

Description

Expulsion of an oxygen-containing gas is arranged.

Devices of this type are known, for example, from EP 1 735 475 B1, are operated as burners and are generally used for oxidizing and calcining, sintering or melting

of dust.

The prices for rock phosphate have recently experienced a constant increase due to the scarcity of suitable sources of raw materials. In addition, the exploited phosphate ores increasingly contain significant amounts of uranium, cadmium, selenium and other accompanying substances that are harmful to health. Such accompanying elements can only be removed with great effort, so that the use of phosphates from such

contaminated ores is becoming increasingly uneconomical.

On the other hand, there are some relative in waste materials

high levels of phosphorus compounds. This hits

in principle the devices mentioned at the outset.

One problem here, however, is that some of the starting materials mentioned are present as relatively large grains or as aggregates that stick together and cannot be comminuted reliably enough in an industrial process. For this reason, their processing by incineration in devices of the type mentioned at the outset is often incomplete, since if the grain sizes are too large, the residence time in the flight phase is not sufficient to achieve incineration through the entire grain. Thus, in the products of the reaction in the known burners, unburned residues accumulate to a large extent, which are distributed and caked in the combustion products and are consequently no longer accessible for further processing. If the educts could be completely converted into a phosphate slag melt, processes would also be available to convert the phosphates into elemental and high-purity phosphorus. High-purity phosphorus starting materials, which can be produced from elemental phosphorus (Pa, white phosphorus), are required in particular for food production and for the pharmaceutical industry. However, production is increasing

difficult and is no longer, at least in Europe

be used.

The present invention is therefore based on the object of further developing a burner of the type mentioned at the outset in such a way that only educt particles whose particle size is sufficiently small to ensure reliable processing get into the combustion chamber. Furthermore, the educts should be distributed or suspended as finely divided and evenly as possible in the gas stream flowing from the feed device into the combustion chamber in order to ensure a long residence time and as complete a conversion as possible of the educts in terms of the combustion of organic accompanying substances and complete oxidation of phosphorus and metals

guarantee.

To solve this problem, a device of the type mentioned at the outset is characterized according to the invention in that in a region axially above the at least one gas inlet, a screw conveyor for the educts arranged in a screen tube provided with holes passes through the vortex chamber. Because a screw conveyor is provided for introducing the educts, educts with different grain sizes can be introduced with a continuous mass flow. In order to prevent too large educt particles from getting into the vortex chamber, the screw conveyor does not end with a discharge end in the vortex chamber, as would be the case for a screw conveyor

intersperses or traverses them completely and

can take place.

Good processing of the starting materials mentioned succeeds when the holes in the screen tube have a diameter of 1.5 mm to 0.5 mm, preferably 1.25 mm to 0.75 mm and particularly preferably 1.0 mm, as is the case here corresponds to a preferred embodiment of the present invention. In this way, educt particles with appropriate diameters are reliably introduced into the vortex chamber and it is avoided that the organic portion of educt particles that are too large does not burn completely in the combustion chamber

can.

In order to be able to utilize educt particles that originally could not pass through one of the holes in the screen tube into the vortex chamber, the present invention is preferably further developed such that a collecting container for educt particles is arranged at a discharge end of the screw conveyor and means for returning educt particles from the collecting container to one upstream of the auger and with the auger

associated crushing device are provided. This

Crushing device is reduced.

In order to achieve an optimized equalization and suspension of the educt particles in the vortex chamber and consequently in the combustion chamber according to the initially stated object of the present invention, the at least one gas inlet is aligned tangentially in order to generate a circulating flow. The circulating flow is generated by a fluidizing gas blown through the at least one gas inlet into the feed device, N2, CO2, superheated steam, H2, CHa, air or mixtures thereof preferably being used as fluidizing gas. The fluidizing gas can be selected depending on the thermochemical requirements of the reactants, whereby it must be ensured that the fluidizing gas under the respective conditions does not lead to premature combustion of the reactants in the feed device, to flashback of the flame from the combustion chamber into the feed device or

leads to an explosion of the educt particles.

In this context, the invention is preferably further developed such that the at least one gas inlet consists of two plates penetrating the housing of the vortex chamber parallel to the vertical axis and inclined towards one another, the plates being displaceable independently of one another into the interior of the vortex chamber. This preferred configuration allows, by suitably shifting the two plates of a gas inlet, both the gap width between the two

Plates as well as the direction of the exit of the gas from the

be provided.

At least one of the plates can preferably be pivoted about an axis arranged in the plane of the plate. Both plates are preferably pivotable about an axis arranged in the plane of the plate. This allows a more flexible adjustment of the gap width and the exit angle from the gas inlet

escaping gas stream.

According to a preferred, alternative embodiment of the present invention, it can also be provided with regard to the design of the at least one gas inlet that the at least one gas inlet is formed by a first tube running parallel to the vertical axis, closed on both sides and slotted on its lateral surface parallel to the vertical axis, which first tube passes through the housing of the vortex chamber, wherein the first tube is preferably rotatably mounted on the housing. Such a gas inlet thus forms a column-like opening in the housing of the vortex chamber and has a slot running parallel to the vertical axis, from which the gas can exit. In this way, the gas emerging from the gas inlet is pushed into the turbulence chamber over an axial length of the turbulence chamber and therefore causes turbulence and turbulence over the entire length of the slotted lateral surface

Equalization of the educt particles in the vortex chamber and

7127

combustion chamber.

In this connection it is preferred that in the first tube a second tube slotted parallel to the vertical axis is arranged coaxially with the first tube, the second tube being rotatable with respect to the first tube. By turning the second tube in the first tube, the effective width of the slot in the lateral surface for the passage of the fluidizing gas can be adjusted through the second tube. Overall, a turbulence and equalization of the educt particles in the eddy chamber that is adapted to the respective conditions of the educts is thus achieved, so that a reliable conversion of the educts in the combustion chamber

can be ensured.

A preferably oxygen-containing gas, for example pure oxygen, is blown into the device according to the invention at high speed via the lance mentioned at the outset in order to atomize the educts and introduce them in highly dispersed form into the combustion chamber for ignition and combustion. In connection with the present invention, this gas flow is to be regarded as a secondary gas flow. Optionally, however, reactive gases such as chlorine gas, ammonia, carbon monoxide, carbon dioxide, hydrogen and/or methane or inert gases such as nitrogen and/or noble gases can also be injected via the lance. Furthermore, the addition of

Water vapor to adjust the flame temperature possible.

Due to the high gas velocity of the gas escaping from the

Lance exits, the educt particles due to local

and dense flame in the combustion chamber.

The measure just described can also

formation of a cyclone-like turbulence are caused,

Embodiment of the present invention corresponds.

In order to further improve the setting of the flow conditions, the lance can preferably be positioned in the direction of the vertical axis

be moveable.

In order to keep the flame temperature in the combustion chamber in a desired range between about 1500° C. and about 1700° C., depending on the quality of the educts, the device according to the invention can preferably be further developed in such a way that the feed device at its end facing the combustion chamber is connected from an annular nozzle to Discharge of water is surrounded, preferably a pyrometer is directed into the combustion chamber to control the discharge of water through the annular nozzle based on measurement data from the pyrometer. The release of water in this area reduces the flame temperature and at the same time improves the heat transfer of the heat from the flame to the educts and can therefore have a positive effect on the processing of the educts. The water is released through the annular nozzle preferably depending on measurement data from a pyrometer, which is preferably directed through the inner lance tube in order to measure the flame temperature. The water requirement depends on

the educt properties.

As already mentioned, the phosphate slag melt formed by the combustion of the educt particles dispersed in the turbulence chamber of the feed device collects at the bottom of the combustion chamber in a slag sump designed as a melting vessel and can be drawn off there. As a result, the phosphate slag melt, for example

only be rapidly cooled to produce an amorphous,

cementitious binder for hydraulic cements. Alternatively, the phosphate slag melt can be treated with other methods for obtaining elemental phosphorus

be further processed.

In order to be able to tap the phosphate slag melt without a great deal of equipment, it is provided according to a preferred embodiment of the present invention that the slag sump has a tapping opening penetrating the refractory material and the housing of the combustion chamber, with a heating device for heating the refractory material in the area of the tapping opening the tap opening is arranged. If the heating device in the area of the tap opening is not put into operation, the phosphate slag melt in the tap opening freezes over with a corresponding length of the tap opening and in this way closes the opening. When the heater is operated, the temperature in the tap hole is appropriately increased so that the molten phosphate slag in the tap hole becomes liquid and the molten phosphate slag can thus flow through the tap hole. This type of closure of the slag sump is sufficient without temperature-sensitive internals and can therefore have a long service life

device according to the invention can be operated reliably.

A preferred embodiment of the heating device provides that the heating device is powered by an induction device and a susceptor that can be inductively coupled to the induction device, preferably in the form of a graphite hollow cylinder.

is formed.

In order to optimize the heat transfer in the area of the heating device, it can preferably be provided that the refractory material in the area of the tapping opening contains corundum. Corundum-containing refractory materials have increased heat transfer compared to conventional refractory materials and therefore conduct the heat of the

Heating device more quickly to the tap opening.

According to a preferred embodiment of the present invention, the extraction device is designed as a riser pipe connected to the combustion chamber with a feed device for a lime carrier, preferably for powdered calcium carbonate. The riser pipe thus protrudes from the combustion chamber next to the feed device and the hot exhaust gases from the processing of the educts either rise in the riser pipe without action or an induced draft is generated on the cold side of the riser pipe. When processing the starting materials containing iron oxide and phosphate, in addition to the desired molten phosphate slag, P20s is unavoidable, which rises in gaseous form in the riser pipe and would pose a major problem when disposing of the waste gas. For this reason, a feed device for a lime carrier, preferably for powdered calcium carbonate, is provided in the riser pipe. The P,Os is converted to thermally stable calcium phosphates by the lime added at this point. A possible reaction equation for this process

can be specified as follows:

CaCO3 —> CaO + CO2 CaO + P2Os —> Cas(PO4)2

This calcination process is endothermic and therefore cools the

process gas off. The Cazs(PO4)z thus formed is thermally stable

and can therefore be returned to the starting materials. For this purpose, the device according to the invention is preferably further developed such that a separating device for separating solid particles from the product gas stream, preferably in the form of a cyclone separator, is connected to the extraction device. Furthermore, it is preferably provided that the return means for solid particles occurring in the separating device are in the screw conveyor or in one of the screw conveyors upstream

Mixer for the starting materials are provided.

The lime carrier, preferably the powdered calcium carbonate, can preferably already be mixed with the educt before the educts are fed into the feed device in order to

Eliminate PoOs from the gas phase.

The invention is explained in more detail below with reference to an embodiment shown in the drawing. In this, FIG. 1 shows a schematic representation of the; device according to the invention, Figure 2 shows a schematic sectional view of the feed device of the device according to the invention with partial sectional views of different areas of the vortex chamber, Figure 3 shows a sectional view of a gas inlet according to the present invention, Figure 4 shows an alternative embodiment of the gas inlets according to the invention and their arrangement on the feed device according to the present invention, 5a to 5c depictions of the functioning of the casein inlets of FIG. 4; and FIG

Tap hole area.

In FIG. 1, the device according to the invention for processing starting materials containing iron oxide and phosphate, in particular waste materials such as sewage sludge, dry sewage sludge, sewage sludge ash, animal meal and/or bone meal, is designated by reference number 1 . The device 1 comprises a combustion chamber 2 lined with a refractory material, a feed device 3 for the educts connected to the combustion chamber 2, a slag sump 4 at a lower end 2a of the combustion chamber 2 and an extraction device 5 for extracting product gases from the combustion chamber 2. The feed device 3 further comprises a vortex chamber 7 arranged along a vertical axis 6 and arranged in a housing 8 . The educts are fed in at a feed end 9 of the feed device 3 . Thorough turbulence and dispersion of the educt particles takes place in the turbulence chamber 7 and are subsequently ignited in the combustion chamber 2 and burned there. Here, a molten phosphate slag 4 is formed, which collects at the bottom of the combustion chamber 2 at the lower end 2a and can be tapped off from there. Process exhaust gas enters the extraction device 5 designed as a riser pipe 5a and rises there in order to be separated from solid particles in a separating device 10 . The separating device 10 preferably has a cyclone separator 11, from which calcium phosphates, such as Ca3(PO4)2, can be returned to the feed end 9 of the feed device 3 via a star feeder 12 and return means 13 (not shown). The calcium phosphates mentioned come from a calcination process in which P2O0s is supplied in the process gas stream via a schematically illustrated supply device 14 CaCO3s. The CaCO3 dissociates in the hot process gas to CaO and CO2 and the CaO

forms together with the P20s Caz3(PO4)2. To the cyclone separator

11 connects a heat exchanger 51 and a dust filter 53 equipped with a suction fan 52 to cool the approximately 700°C hot process gas, which essentially consists of CO and Hz, so that the fine dust fraction can be more or less completely eliminated from the process gas. The process gas from the suction fan 52 can then be supplied to gas utilization in a manner known per se. The fine dust from the dust filter 53 can be returned to the educts

or supplied to non-ferrous metallurgy.

In FIG. 2 and FIG. 3, the same elements are provided with the same reference numbers. In FIG. 2, the feed device 3 is shown in more detail and it can be seen that in an area axially above a gas inlet 15 a screw conveyor 18 for the educts 19 arranged in a screen tube 17 provided with holes 16 traverses the vortex chamber 7 . This means that the screw conveyor 18 does not end in the turbulence chamber 7, but that it completely penetrates the turbulence chamber 7 and the educts 19 are released into the turbulence chamber 7 exclusively through the holes 16 in the screen tube 17. Immediately after passing through the holes 16, the educt particles are caught by the gas flow from the gas inlet 15 and swirled accordingly. The gas inlet 15 is fed by a ring line 20 and several gas inlets 15 can be arranged around the circumference of the vortex chamber 7 . Oversize from the screw conveyor 18, which could not pass through the holes 16, is discharged via a rotary valve 21 of a collecting container 22 and, after appropriate crushing, back into the screw conveyor

18 introduced.

The gas inlet 15 is from a parallel to the vertical axis 6

running, closed on both sides and at its

Lateral surface 23 slotted parallel to the vertical axis of the first tube 24 is formed. The gas stream exits slot 25 to swirl the educt particles 19 and if, as shown in partial section A on the right-hand side of the representation of swirl chamber 7, the gas exits tangentially, a rotating gas and

Educt particle flow in the vortex chamber 7 from.

A lance 26 for ejecting an oxygen-containing gas is arranged in the vortex chamber 7 along the vertical axis 6 . The lance 26 is designed as a double tube. The lance 26 can be displaced in the direction of the vertical axis 6 , as indicated by the double arrow 27 . The lance 26 has an outer lance tube 28 and an inner lance tube 29 so that an annular gap 30 is formed through which a primary oxygen gas stream is introduced into the vortex chamber 7 . The primary gas flow exits at the lower end 30a through a plurality of holes 31 and leads to further turbulence of the process gas flow, as shown in the partial section B on the left-hand side of the representation of the turbulence chamber 7 . At the lower end of the feed device 3, this converges to form a nozzle 32 in order to eject the gas flow together with the educt particles into the combustion chamber 2 and to ignite the educt particles there. The task device 3 is at its end 3a facing the combustion chamber 2 by an annular nozzle 33 for the delivery of

surrounded by water.

A gas inlet 15 is shown in section in FIG. In the first tube 24 is a second tube 34 with a slot 35 coaxial and rotatable to

first tube 24 arranged. By twisting the second tube

34 in the first tube 24 in the direction of the double arrow 38, the size of the slot 25 effective for the gas passage can be adjusted and by rotating the first tube 2 in the direction of the double arrow 39, the angle at which the gas enters the vortex chamber 7 can be adjusted. Stops 36 and 37 limit the twisting of the second tube 34 relative to the first tube 24. By twisting the second tube 34 in the first tube 24 in the direction of the double arrow 38, a nozzle effect can be achieved through which the gas outlet

speed can be influenced.

In FIG. 4, the gas inlets 15 are each formed by two plates 40 which pass through the housing 8 of the vortex chamber 7 parallel to the vertical axis 6 and are inclined towards one another. As a result, a gap 41 is formed in each case, through which the gas escapes into the interior of the vortex chamber 7 . The gas inlets 15 are in turn supplied with gas by a ring line 20 and can, as required, through valves 42 of the

Ring line to be disconnected.

By moving the plates 40 into the interior of the vortex chamber 7 in the direction of the double arrows 43, the width a of the gap 42 can be adjusted in each case, as is shown in FIG

can be seen.

If the plates 41, which are made of steel strip, for example, are not shifted to the same extent, but, for example, as shown in FIG also a gap of width a, however, the exit direction of the gas flow, which passes through the gas inlet 15, is to the right

directed. In this way, the twist of the

injected gas streams can be adjusted as required. Finally, in FIG. 5c it can be seen that the plates 40a and 40b can be pivoted about a pivot joint 45 about an axis 44 arranged in the plane of the plate. This allows a further influencing of the exit of the gas flow from the gas inlet

15

The slag sump 4 can be tapped off via a tapping opening 47 penetrating the refractory material 46 and the housing 54 of the combustion chamber 2 . A heating device 48 for heating the refractory material 46 in the area of the tap opening 47 is arranged in the area of the tap opening 47 . The heating device 48 is formed here by an induction device 49 and a susceptor 50 arranged next to the induction device 49, the susceptor 50 being designed in the form of a graphite hollow cylinder. This is in the area of tapping hole 47

Refractory material 46 containing corundum.

Claims (17)

Patent Claims: 1. Device (1) for processing starting materials containing iron oxide and phosphate, in particular waste materials such as sewage sludge, dry sewage sludge, sewage sludge ash, animal meal and/or bone meal as well as phosphate-containing metallurgical slag and dust and rolling mill scale, comprising a refractory material (46 ) lined combustion chamber (2), a feed device (3) connected to the combustion chamber (2) for the educts, a slag sump (4) at a lower end (2a) of the combustion chamber (2) and an extraction device (5) for extracting product gases from the combustion chamber (2), wherein the feed device (3) has a vortex chamber (7) arranged along a vertical axis (6) with at least one gas inlet (15 ) comprises, wherein in the vortex chamber (7) along the vertical axis (6) a lance (26) for ejecting an oxygen-containing gas is arranged, characterized in that net that in an area axially above the at least one gas inlet (15) a screw conveyor (18) arranged in a screen tube (17) provided with holes (16) passes through the vortex chamber (7) for the reactants. 2. Device according to claim 1, characterized in that the holes (16) in the screen tube (17) have a diameter of 1.5 mm to 0.5 mm, preferably from 1.25 mm to 0.75 mm and in particular preferably of 1.0 mm. 3. Device according to claim 1 or 2, characterized in that at a discharge end of the screw conveyor (18) a collecting container (22) for educt particles is arranged and preferably return means for educt particles from the Collection container (22) in one of the screw conveyor (18) upstream and connected to the screw conveyor (18). Crushing device are provided. 4. Device according to claim 1, 2 or 3, characterized in that the at least one gas inlet (15) of two plates (40, 40a, 40b), the plates (40, 40a, 40b) being fed independently into the interior of the vortex chamber (7) are movable. 5. Device according to claim 4, characterized in that at least one of the plates (40, 40a, 40b), preferably both plates (40, 40a, 40b) is arranged around a plate plane Axis (44) is pivotable. 6. The device according to claim 1, 2 or 3, characterized in that the at least one gas inlet (15) is connected to a first tube running parallel to the vertical axis (6), closed on both sides and slotted on its lateral surface (23) parallel to the vertical axis (6). (24) is formed, which first tube (24) passes through the housing (8) of the vortex chamber (7), the first tube (24) preferably being rotatable on Housing (8) is mounted. 7. The device according to claim 6, characterized in that in the first tube (24) a slotted second (34) tube parallel to the vertical axis (6) is arranged coaxially with the first tube (24), the second (34) tube being rotatable to the first tube is . 8. Device according to one of claims 1 to 7, characterized in that the lance (26) is designed as a double tube, forming an annular gap (30) between an inner lance tube (29) and an outer lance tube (28), the outer tube (28) rests against the inner tube (29) at its end remote from the conveyor screw (18) and has a plurality of holes (31) for the passage a gas, preferably oxygen. 9. The device according to claim 8, characterized in that the holes (31) to a radial direction of the vortex chamber (7) are aligned inclined. 10. Device according to one of claims 1 to 9, characterized in that the lance (26) in the direction of Vertical axis (6) is displaceable. 11. Device according to one of Claims 1 to 10, characterized in that the feed device (3) is surrounded at its end (3a) facing the combustion chamber (2) by an annular nozzle (33) for dispensing water, with a pyrometer preferably being installed in the combustion chamber (7) is directed to the discharge of water through the annular nozzle (33) based on measurement data of the to control the pyrometer. 12. Device according to one of claims 1 to 11, characterized in that the slag sump (4) has a refractory material (46) and the housing (54) of the combustion chamber (2) penetrating tapping opening (47), wherein in the region of the tapping opening ( 47) a heating device (48) for heating the refractory material (46) in the area of Tapping opening (47) is arranged. 13. Device according to claim 12, characterized in that the heating device (48) is controlled by an induction device (49) and a susceptor (50) which can be inductively coupled to the induction device (49), preferably in the form of a graphite Hollow cylinder is formed. 14. Device according to one of claims 1 to 13, characterized in that the refractory material (46) in the region of Tapping opening (47) contains corundum. 15. Device according to one of claims 1 to 14, characterized in that the extraction device (5) as the combustion chamber (2) subsequent riser (5a) with a feed device (14) for a lime carrier, preferably for dusty calcium carbonate is formed. 16. Device according to one of claims 1 to 15, characterized in that a separating device (10) for separating solid particles from the product gas stream, preferably in the form of a cyclone separator (11) to which trigger device (5) connects. 17. The apparatus according to claim 16, characterized in that return means (13) for in the separating device (10) accumulating solid particles in the screw conveyor (18) or in one of the screw conveyor (18) upstream mixer for Educts are provided. Vienna, June 2, 2021 Applicant by Haffner und Keschmann Patenanwälte GmbH