MX2008008458A

MX2008008458A - Quench system for metallurgical gases

Info

Publication number: MX2008008458A
Application number: MXMX/A/2008/008458A
Authority: MX
Inventors: Daum Karlheinz; Schalk Wolfran; Kerstiens Bernd; Serdarusic Gertrud
Original assignee: Outokumpu Technology Oy
Priority date: 2006-01-02
Filing date: 2008-06-27
Publication date: 2008-09-26

Abstract

A quench system for cooling and/or cleaning metallurgical gases which are guided cocurrently with an acid-containing liquid, in particular sulfuric acid, includes a gas inlet (51) through which the gases are supplied from the top, an annular channel (55) extending about the inner circumference of an upper Venturi portion (52), over whose inner overflow wall (57) the acid-containing liquid flows over into the upper Venturi portion (52), and lateral nozzles (58) provided below the annular channel (55), through which additional acid-containing liquid is introduced. To obtain a clear separation between wall portions of the Venturi portion exposed to dry/hot or wet/cold conditions, the inside diameter (D1 ) of the upper Venturi portion (52) is greater than the inside diameter (D2) of the gas inlet (51), in accordance with the present invention.

Description

QUICK COOLING SYSTEM FOR METAL GASES Field of the Invention The present invention relates to a quench system for cooling and possibly cleaning metallurgical gases in particular, which are conducted in parallel flow with an acid-containing liquid, in particular sulfuric acid, comprising a gas inlet by wherein the gases are introduced from the top, an annular channel extends around the inner circumference of a portion of the upper Venturi, on the inner overflow wall of which the liquid containing the acid flows over the Venturi portion, and comprises nozzles laterals provided below the annular channel, through which liquid containing acid is additionally introduced.

BACKGROUND OF THE INVENTION Abrupt cooling systems are used, for example, for cooling and partly also for the cleaning of gases containing SO2, which are formed in metallurgical processes during the melting of metals. When gases containing S02 are subsequently used for the manufacture of sulfuric acid, they must be freed of impurities and solids before entering the contact area of the sulfuric acid plant. After a majority separation of the powder content, for example in dust separators, electrostatic precipitators and the like, the gases are flushed in a rapid cooling system, for example in radial flow washers. In the rapid cooling system the gases are cooled to a degree such that they are appropriate for the equipment that follows the line, and are partly cleaned. The remaining impurities are partially absorbed in sulfuric acid and separated from the gas stream. In a conventional rapid cooling system 1, such as that shown in Figure 1, the cap 2 of the tower includes nozzles 3 through which, for example, 25% sulfuric acid is introduced. The hot gas containing S02 and to be cleaned is introduced through a gas inlet 4 and conducted in countercurrent to the sulfuric acid. In order to resist the waste acid, the fast cooling tower has an acid resistant coating. The material of this coating is selected according to the respective exposure, and there are materials that are particularly suitable for exposure to dry / hot or wet / cold conditions. What is always critical here is the transition between the wall portions exposed only to dry and hot gas or only to humid and relatively cold sulfuric acid. In the embodiment shown in Figure 1 in the area marked X at the gas inlet 4 it repeatedly includes portions which are all the time exposed to hot gas only and are then exposed to dry / hot conditions or which at times are humid with acid sulfuric and subsequently exposed to humid / cold conditions. This alternating exposure leads to accelerated wear of the coating, so that it has to be replaced. In alternative modes of the quench tower, the gas containing S02 is conducted in parallel with the sulfuric acid used for cooling and cleaning. In the mode of a Venturi type quench tower 10 as shown in Figure 2, the sulfuric acid is injected through the side nozzles 11 into the gas that is fed from the top. Above the nozzles 11 an annular tube 12 is provided, through which additional acid is sprayed against the wall of the Venturi portion, for the purpose of moistening it. This should ensure a clear separation between the hot / dry and wet / cold regions. However, the corrosion problems lead to an irregular wetting of the wall of the Venturi portion and hence the undefined regions with wall portions are exposed to both dry / hot and wet / cold conditions. In the Venturi type 20 quick cooling tower 20 as shown in Figure 3, the humidification of the wall portions above the side nozzles 21 is effected by means of a circumferential annular conduit 22, through which sulfuric acid is supplied. The sulfuric acid flows from the annular conduit 22 through a spill wall 23 into the Venturi portion of the quench tower 20 and wet the walls. Due to deposits in the annular conduit 22 and due to turbulences that are generated by the gas stream containing solids here too an irregular overflow can occur, which can lead to coating zones which are alternatively exposed to dry / hot and humid conditions / cold.

OBJECTIVES AND SUMMARY OF THE INVENTION The objective of the present invention is to achieve a clear separation between dry / hot and humid / cool zones in the Venturi portion and thus improve the durability of the rapid cooling systems. This object is substantially solved by means of the present invention in that the inner diameter of the upper Venturi portion before the throat of the Venturi is greater than the inner diameter of the gas inlet. With this it is achieved that the gas flowing from the top through the gas inlet inlet does not damage the overflow of the acid-containing liquid, in particular sulfuric acid, from the annular channel, so that the peripheral wall of the Venturi portion can be wetted evenly with sulfuric acid. This ensures a clear separation between regions of the wall cladding in the vicinity of the inlet of gases that are exposed only to hot and dry conditions and the advancing regions of the annular channel that are only exposed to humid and cold conditions. By means of a corresponding selection of the materials for the coating of the rapid cooling system its life can be considerably increased, so that the service intervals can be lengthened. The Venturi-type abrupt cooling towers that are known and shown in Figures 2 and 3, however, have in common that the gas inlet and the Venturi sector that is before the Venturi throat have the same diameter. Also the quench tower 1 which works countercurrent, of the embodiment as shown in Fig. 1, also has a constant inside diameter. According to a preferred aspect of the invention, the inner diameter of the upper Venturi portion is greater than the inner diameter of the gas inlet by 5-15%, preferably 7-10%. This ensures that the sulfuric acid from the annular channel can flow over the overflow wall without being disturbed and can evenly wet the wall of the Venturi portion. With a diameter of the gas inlet of for example 2,800 mm, it was shown that an increase in the internal diameter of the Venturi portion of 100-500 mm is desirable. According to a particularly preferred embodiment of the present invention, the annular channel widens towards the upper part. This enables a high flow velocity at the bottom of the annular channel, which prevents the solids contained in the sulfuric acid from being deposited in the conduit. On the other hand, the increase of the annular channel in the upper portion ensures a low rate of overflow of the sulfuric acid, so that a uniform liquid film is formed on the wall of the Venturi portion. According to one aspect of this invention, the annular channel widens conically towards the upper part, where the widening of the annular channel is preferably achieved by an inclination of the outer surface of the overflow wall that faces the annular channel in A side. The outer wall of the quench tower can then be provided with uniform insulation. In this way it has been found convenient to increase the width of the annular channel from its lower portion to its upper portion by 100-200%, preferably by approximately 150%. To improve uniform wetting of the peripheral wall of the Venturi portion, the upper edge of the overflow wall is preferably inclined at 20 ° to 70 °, preferably at 30 ° to 60 °, and normally about 45 ° in the direction of flow of the liquid that contains the acid. According to one aspect of the invention, the annular channel is fed with sulfuric acid through several, in particular six inlet openings. To achieve a uniform flow, the inlet openings are preferably evenly distributed around the circumference of the Venturi portion and tangentially open in the annular channel. In adaptation to the exposure that occurs, the walls of the Venturi portion in the vicinity of the gas inlet, the Venturi lid, and the annular channel are coated according to the invention with different brick qualities. It turns out to be very convenient to coat the region of the gas inlet with temperature-resistant bricks, in particular bricks of silicon carbide bonded with nitride, which has good properties of resistance to exposure to hot and dry conditions. On the other hand, the annular channel area is preferably coated with carbon / graphite brick, which can easily withstand exposure to humid and cold conditions. The graphite brick has a good resistance against acids and thermal shock, so that this relatively more expensive material is preferably used in the vicinity of the venturi lid and / or the transition area of the gas inlet to the Venturi cap as well as possibly also on top of the spill wall. Because the cements and mortars used for the construction of facing brick walls can also withstand exposure to dry / hot or wet / cold conditions well, according to one of the embodiments of the present invention, the bricks for the The lining of the walls of the gas inlet, the Venturi lid and the annular channel are assembled using different qualities of cements and mortars, adapted to the respective exposure profiles. The invention will be explained in detail in the following and with reference to one embodiment and the drawings. All the features described and / or illustrated per se or in any combination form the objective of the invention, independently of their inclusion in the claims or in their way of relating them.

Brief Description of the Drawings Figure 1 shows a schematic representation of a conventional fast cooling tower, which operates in countercurrent. Figure 2 shows a schematic representation of a conventional fast cooling tower, Venturi type, operating in parallel current. Figure 3 shows a schematic representation of another conventional cooling tower, of Venturi type, operating in parallel current. Figure 4 shows a schematic representation of a rapid cooling system according to the present invention. Figure 5 shows a partial section amplified through the rapid cooling system as shown in Figure 4, in the vicinity of the annular channel. Figure 6 shows a section along line VI-VI of Figure 4, and Figure 7 schematically shows the re-equipment of a conventional chill tower with the present invention.

Detailed Description of the Preferred Modes of the Invention Figures 4 through 6 show schematically a Venturi type quench system in accordance with the present invention. At its upper end, the Venturi 50 comprises a gas inlet 51, a portion 52 of the upper Venturi 52 adjoining and the throat 53 of the Venturi that follows it. In the illustrated embodiment, the internal diameter DI of the portion 52 of the Venturi is greater than the inner diameter D2 of the gas inlet 51 by approximately 7.5%. The dimensioning of the widening depends on the total size of the plant. The transition between the different diameters is referred to as the cap or roof 54 of the Venturi. An annular channel 55 in the form of a groove extending on the periphery of the portion 52 of the venturi is provided below the cover 54 of the Venturi. The annular channel 55 is defined by the outer wall 56 of the Venturi 50 and by an overflow wall 57. Below the annular channel 55 are provided at the end of the upper Venturi portion 52 several, for example eight side nozzles 58 and uniformly distributed over the perimeter of the Venturi 50, for the injection of sulfuric acid. The nozzles 58 are preferably 60 ° nozzles, which inject and atomize the sulfuric acid with a pressure loss of approximately 1 to 2 bar. As can be seen especially in Figure 6, several, in particular six inlet openings 59, for the supply of sulfuric acid, are evenly distributed around the circumference of the Venturi 50 open tangentially within the annular channel 55. As can be seen in FIG. To better appreciate in Figure 5, the lower portion of the annular channel 55, within which the intake openings 59 are opened, has a relatively small width of, for example, 80 mm, which is approximately equivalent to the cross-sectional area of opening of the inlet openings 59. Towards the upper part, the annular channel 55 widens uniformly due to the inclination of the external surface 60 of the overflow wall 57, until it presents at its upper end a width of, example, 200 mm, which corresponds to a widening of the annular channel 55 of 150%. The upper edge 61 of the overflow wall 57, which leads to the portion 52 of the upper Venturi, is sloped down approximately in the Venturi 50 is constructed of several layers of coating that are adapted to the respective exposure to gas or acid introduced sulfuric, which are shown in Figure 5. In the vicinity of the entrance 51 of gases, is provided from the outside in first a simple insulating brick or foam glass 62, then an insulating and refractory brick (lightweight refractory brick) ) 63 and finally a brick 64 of silicon carbide bonded by nitride and resistant to temperature. In the vicinity of the roof 54 of the Venturi 54, and in particular in the transition region between the inlet 51 of the gases and the cover 54 of the Venturi 54, a graphite brick 65 is provided, for example as a shaped graphite roof brick, in place of the silicon carbide brick. In Figure 5 the graphite brick 65 is simply provided in the transition region between the inlet 51 of the gases and the cover 54 of the Venturi 54, but may also extend over that part of the cover 54 of the Venturi above. of the annular channel 55. In the vicinity of the annular channel 55 and of the portion 52 of the upper Venturi, there is first provided a layer of normal bricks 66 resistant to acid on the outside, which is delimited by a layer of bricks 67 of carbon. The overflow wall 57 also consists of coal bricks 67, for example in the shape of a wedge-shaped coal brick. If necessary, the upper part of the overflow wall 57, which comes into contact with the gas stream, can also be made with graphite brick. According to the exhibition, the coatings can be glued with different types of cement or mortar. The Venturi 50 of the rapid cooling system of the present invention is substantially designed as described above. Your mode of operation will be explained below. To the Venturi 50, a hot gas containing S02, which comes from a metallurgical plant, is introduced from the upper part and through the inlet 51 of gases. The cooling and cleaning of the gas stream are effected by means of sulfuric acid, which is mainly injected through the side nozzles 58 and cools the gas stream, so that it can be conducted to the other equipment and subsequently to a contact sulfuric acid formation plant. At the same time the impurities are absorbed and the dust particles are trapped.

The surrounding annular channel 55 which is located above the side nozzles 58 is also supplied with sulfuric acid, sulfuric acid which flows over the overflow wall 57 and wets the wall of the upper Venturi portion 52. Due to the enlarged cross-section of the annular channel 55, the sulfuric acid found in the lower portion of the annular channel 55 flows with a relatively high flow velocity, so that the solids which are contained in the sulfuric acid are kept in suspension and they can not settle. Due to the enlarged cross-section of the annular channel 55, the flow velocity is reduced towards the upper part and in the upper region only about 30-40% of the feed rate through the intake openings 59, so that the sulfuric acid can flow slowly over the overflow wall 57 and evenly wet the upper part 52 of the Venturi. This ensures that a uniform liquid film is formed on the top 52 of the Venturi, so that the coating 67 in this area is exposed only to wet and cold conditions. In the vicinity of the gas inlet 51, however, only the hot and dry gases come into contact with the sheath 64. The increased diameter DI of the upper Venturi portion 52 ensures that the gas stream does not damage or break the film. of liquid that is on the wall of portion 52 of the upper Venturi. In this way, a clear separation is achieved between wall regions that are exposed exclusively to hot and dry conditions and exclusively to humid and cold conditions. This extends the life of the coating and hence the service intervals. Figure 7 shows how a conventional fast cooling tower 1, which for example had been operated up to now according to the modality as shown in Figure 1, can be re-equipped with the invention. The Venturi 50 according to the present invention is provided upstream of the gas inlet 3 as shown in Figure 1 and is mounted laterally on the inlet opening of the quench tower 1. The gas that is conducted in flow Parallel with sulfuric acid flows through the Venturi 50 and then enters the existing, cool cooling tower 1, to which the gas leaves through the upper outlet opening, so that for example it is driven to an operation of gas cleaning that continues. The sulfuric acid is removed from the well 6 of the quench tower 1 and is discharged through the conduit 7. The nozzles 3, which in the previous quench tower 1 were provided in the roof 2 of the quench tower , they are for example only operated for 50%. In addition, emergency water nozzles are provided in the cover of the cooling tower for additional cooling of the gas stream, in case said gas stream is still too hot to be supplied to the following plastic elements. . Since the existing quench tower is re-equipped with the Ventura of the invention, an appropriate liner can also be used for a corresponding exposure in problematic zone X at the transition from the gas inlet into the quench tower , coating which is not damaged by alternating exposure.

Example: In a fast cooling tower according to the invention, the lower diameter DI of the upper Venturi portion 52 of about 3000 mm and is larger than the inner diameter D2 in the vicinity of the gas inlet 51 by about 200. By the introduction of gases 51 approximately 200,000 Nm3 / hr of gas containing S02 are introduced at a temperature of approximately 350 ° C. For the cooling and cleaning of the gas a total of approximately 450 m3 / hr of sulfuric acid is supplied with a maximum of 25% at a temperature of 60 - 70 ° C, and for example, 370-390 m3 / hr are supplied through the nozzles 58 and correspondingly 60-80 m / hr through the annular channel. In the nozzles 58 the sulfuric acid is atomized with a pressure loss of 1-2 bar. The sulfuric acid is introduced into the annular channel 55 with a flow velocity of about 1-2 m / sec so that the solids contained in the sulfuric acid (not more than 10 gr / 1) are kept in suspension in the lower part of the annular channel 55 and can not sediment. In the lower portion, the width of the annular channel is approximately 80 mm and increases upwards to approximately 200 mm. With that the flow velocity of the sulfuric acid in the upper part of the annular channel is reduced when it is poured into the portion 52 of the Venturi greater than about 40% of the feed rate. This provides uniform wetting of the portion 52 of the upper Ventura 52.

List of components 1 Rapid cooling tower 2 Cover 3 Nozzle 4 Gas inlet 5 Acid resistant coating 6 Well 7 Conduit 10 Cooling tower 11 Nozzle 12 Annular tube 20 Rapid cooling tower 21 Nozzle 22 Annular channel 23 Overflow wall 50 Venturi 51 Gas inlet 52 Upper portion of the Venturi 53 Venturi Gorge 54 Venturi Roof or Cover 55 Annular channel 56 External wall 57 Overflow wall 58 Nozzle 59 Opening for entry 60 External wall 61 Top edge 62 Foam glass 63 Insulating refractory brick 64 Silicon carbide brick 65 Graphite brick Acid resistant brick Carbon brick Internal diameter of the upper portion 52 of the Venturi Internal diameter of the gas inlet 51

Claims

Claims 1. A rapid cooling system for the cooling and / or cleaning of particular metallurgical gases, which are guided in parallel flow with an acid-containing liquid, in particular sulfuric acid, which comprises: through which the gases are supplied from the top, an annular channel that extends around the inner circumference of a portion of the upper Venturi, on whose internal overflow wall the liquid containing acid is poured into the Venturi portion. upper, and side nozzles provided below the annular channel, and through which additional acid-containing liquid is introduced, characterized in that the inside diameter of the upper portion of the venturi is greater than the inside diameter of the gas inlet.
2. The rapid cooling system according to claim 1, characterized in that the inner diameter of the upper portion of the venturi is greater than the inner diameter of the gas inlet by 5 to 15%, preferably 7 to 10%.
3. The rapid cooling system according to claim 2, characterized in that the internal diameter of the upper portion of the venturi is 100 to 500 mm, preferably approximately 200 to 400 mm greater than the internal diameter of the gas inlet.
4. The rapid cooling system according to one of the preceding claims, characterized in that the annular channel widens upwards.
5. The rapid cooling system according to claim 4, characterized in that the widening of the annular channel is achieved by the inclination of the external surface of the overflow wall that faces the annular channel.
The rapid cooling system according to claim 4 or 5, characterized in that the width of the annular channel increases from its lower end towards its upper end by 100 to 200%, preferably approximately 150% > .
The rapid cooling system according to one of the preceding claims, characterized in that the upper edge of the overflow wall is preferably inclined between 20 to 70 °, preferably between 30 to 60 ° and normally around 45 ° in the direction of the liquid flow that contains acid.
8. The rapid cooling system according to one of the preceding claims, characterized in that it has a plurality of inlet openings for the acid-containing liquid that drain tangentially into the annular channel. The rapid cooling system according to claim 8, characterized in that the inlet openings are uniformly distributed around the circumference of the Venturi portion. The rapid cooling system according to one of the preceding claims, characterized in that the walls of the venturi are coated in the vicinity of the gas inlet, the venturi cover and the annular channel with bricks of different qualities. The rapid cooling system according to one of the preceding claims, characterized in that the region of the gas inlet is coated with temperature resistant bricks, especially silicon carbide bricks. The rapid cooling system according to one of the preceding claims, characterized in that the area of the annular channel is coated with carbon / graphite bricks. The rapid cooling system according to one of the preceding claims, characterized in that the area of the venturi lid and / or the transition area of the gas inlet towards the venturi lid is coated with graphite bricks. The rapid cooling system according to one of the preceding claims, characterized in that the bricks for coating the walls of the gas inlet, the venturi lid and the annular channel are placed with cement or mortar of different properties .