AU2015100093A4 - Apparatus for sintering ore - Google Patents

Abstract

Abstract A device for sintering metalliferous substances on a sintering machine, wherein a feedback device and a waste gas line are connected by lines to a collecting line and a removal line, and wherein switchover devices are present in the collecting line and in the removal line suitable for directing sintering waste gas conveyed in the collecting line or in the removal line respectively either into the feedback device or into the waste gas line. > - ---- ell, > -------------------------

Description

1 Apparatus for sintering ore Field of technology Aspects of the present disclosure relate to a method and a system for sintering metalliferous substances, such as iron ores or manganese ores for example, especially oxidic or carbonatic ores, on a sintering machine with sintering gas feedback. Background The sintering of metalliferous substances, such as iron ores or manganese ores for example, especially oxidic or carbonatic ores, is done by means of sintering machines. After the sinter mixture, which consists of metalliferous material, returned material, solid fuel, supplements etc., is fed onto the sintering belt of the sintering machine, the sinter mixture is ignited on its surface in an ignition furnace. Subsequently gases containing oxygen are conveyed through the sinter mixture as a process gas, through which the sinter front of the surface of the sinter mixture moves in the direction of the sintering belt surface. The gases used as process gas are for example fresh air, exhaust air from a sinter cooler, air used for pre-drying the sinter mixture or a mixture of a number of these gases, or a mixture of one or more of these gases with technical oxygen. In such cases the sintering belt is moved from the charge point in the direction of the discharge point. During transport on the sintering belt the entire sinter mixture is sintered-through and leaves the sintering belt at the discharge point as hot finished sinter. The hot finished sinter is cooled in a subsequent sinter cooler. Sintering machines can be embodied for example as 2 traveling grate sintering machines, in which the process gas is sucked through the sinter mixture by a vacuum being applied by means of fans to the suction boxes lying under the sintering belt. In normal operation there is a change in temperature and oxygen content of the sintering waste gas occurring along the sintering belt. The temperature of the sintering waste gas increases along the sintering belt. The oxygen content of the sintering waste gas initially decreases along the sintering belt, in order to increase again after reaching a minimum. Usually the temperature of the sintering waste gas amounts in the front first section of the sintering belt to below 100'C and increases by the rear section to over 300'C. By means of suction boxes positioned under the sintering belt the process gas is sucked through the sinter mixture and the sintering waste gas generated during this passage is collected and taken away. Since the sintering process requires large quantities of process gas, large quantities of sintering waste gas are produced. The sintering waste gas contains components such as vaporized water from the sinter mixture, CO 2 and CO from the partially incomplete combustion of the fuel and calcination processes, also from the combustion of sulfur contained in the fuel or ore, sulfur oxides SOx, as well as nitrogen oxides NOx, dioxines, furanes and dust. Before the sintering waste gas can be released into the environment as waste gas of the sintering machine, the removal of pollutants is necessary in order to minimize the environmental damage. A reduction of the quantity of waste gas to be taken away from a sintering machine or the pollutant load contained in the waste gas facilitates waste gas cleaning.

3 Reducing the quantity of waste gas and the pollutant load contained in the waste gas by feeding back a part of the sintering waste gas to the sinter mixture as process gas is already known. Through this process on the one hand the quantity of process gas introduced into the sintering machine from outside is reduced and on the other hand the oxygen contained in said gas is better utilized. In W02007/082694 for example, sintering waste gases from a start area and an end area of the sintering belt are cleaned in a collecting line and fed back to a central area of the sintering belt, after which sintering waste gas from the central area is removed from the process via a discharge line. The corresponding suction boxes open out into the collecting line or the discharge line respectively. A discharge of sintering waste gas from the start area or end area or a feedback of sintering waste gas from the central area is not completely possible. Accordingly the system is defined for the recirculation of sintering waste gas from the central area. Changed process conditions, such as other raw materials through example or changed legislative regulations can however lead to a recirculation of sintering waste gas from the central area being desired in order to keep the SOx content in the discharged waste gas as low as possible. Summary Aspects of the present disclosure provide an apparatus which, in relation to the origin of the sintering waste gas to be fed back, makes possible a more flexible operation than in the prior art.

4 This is achieved by a device for sintering metalliferous substances, such as iron ores or manganese ores for example, especially oxidic or carbonatic ores, at a sintering machine - with a charging device for feeding a sinter mixture containing a solid fuel onto a sintering belt, - with suction boxes for conveying process gas containing oxygen through the sinter mixture in three consecutive sections of the sintering belt, of which the first section adjoins the feeding device and the third section is delimited by the ejection end of the sintering belt, - with a collecting line for combining and forwarding the sintering waste gas arising in the suction boxes of the third section and in the suction boxes of the first section, - with a removal line for combining and forwarding the sintering waste gas arising in the suction boxes of the second section, - with a feedback device for transport and for distribution of sintering waste gas as at least part of process gas to the sinter mixture on the sintering belt, preferably to the sinter mixture in the second section of the sintering belt, - with a waste gas line for taking away sintering waste gas from the sintering machine, - where the feedback device and the waste gas line, are connected by lines to the collecting line and the removal line, and - where switching facilities suitable for directing sintering waste gas conveyed in the collecting line or in the removal line respectively are present either in the feedback device or in the waste gas line.

5 The process gas containing oxygen is conveyed through the sinter mixture by a vacuum being applied by means of fans to the suction boxes lying under the sintering belt. Through this the process gas is sucked through the sinter mixture into the suction boxes. The sections are divided up so that the quantity of waste gas of the sintering machine is minimized and fed-back sintering waste gas, in normal operation, if necessary after addition of exhaust air from a sinter cooler and/or fresh air and/or air used for pre-drying the sinter mixture and/or technical oxygen to the mixture gas, has a specific temperature and a specific oxygen content. The minimum temperature amounts to 90'C, preferably 100'C, and usually the highest temperature amounts to up to the 150 0 C, preferably up to 130 0 C. The lower limit for the oxygen content is 13 Vol%, preferably 17 Vol%, but oxygen contents of up to 20 Vol% or higher are possible. With this temperature it is guaranteed that the danger of corrosion in the sections through which the gas flows is kept low. With this oxygen quantity it is guaranteed that a good sintering quality is achieved. An oxygen quantity that is as high as possible is preferred. Depending on the process parameters such as sintering belt speed, composition of the sinter mixture, oxygen content of the process gas, layer thickness of the sinter mixture on the sintering belt, permeability of the sinter mixture, vacuum applied to the suction boxes, amount of process gas conveyed through the mixture, the proportion of each section of the overall length of the sintering belt varies in a certain range. The first section of the sintering belt usually occupies 20-60% of the length of the sintering belt, preferably 30-50%.

6 The second section of the sintering belt adjoining the first section usually occupies 30-60% of the length of the sintering belt, preferably 40-50%. The third section of the sintering belt adjoining the second section usually occupies 5-20% of the length of the sintering belt, preferably 10-15%. With an appropriate division the sintering waste gases and thus the process gas for the second section possess the desired respective temperatures and oxygen contents in normal operation. In the collecting line the sintering waste gases arising in the suction boxes of the third section and the suction boxes of the first section are combined and conveyed onwards away from the sintering belt. In the removal line the sintering waste gas arising in the suction boxes of the second section is combined and conveyed onwards away from the sintering belt. In the waste gas line sintering waste gas is taken away from the sintering machine. The feedback device serves to transport and to distribute sintering waste gas, as at least part of the process gas, to the sinter mixture on the sintering belt. It can be fed back and distributed to one or more sections of the sintering belt. Preferably it is embodied so that sintering waste gas is transported and distributed as at least part of the process gas to the sinter mixture on the sintering belt, at least to the sinter mixture in the second section of the sintering belt.

7 Advantageously the entire sintering waste gas is not fed back but only a part of it. Preferably up to 50% of the sintering waste gas is fed back. If necessary oxygen is added to the fed-back sintering waste gas, for example by cooling air from a sinter cooler connected downstream from the sintering system being added. In accordance with aspects of the present disclosure, the feedback device and the waste gas line are connected to the collecting line and the removal line such that sintering waste gas from collecting line and removal line can be introduced into the feedback device and into the waste gas line. In order to make a controlled switch between an introduction of sintering waste gas into the feedback device and an introduction into the waste gas line, switchover devices are present in the collecting line and in the removal line. These switchover devices are suitable for directing sintering waste gas either into the feedback device or into the waste gas line. By setting the switchover devices accordingly it can be selected whether sintering waste gas is to be removed from the sintering machine either from the second section and fed back onto the sintering belt from the first and third section or whether there is to be feedback from the second section onto the sintering belt and removal from the first and the third section. This enables there to be a flexible reaction to changed raw material conditions and waste gas requirements. The switchover devices are flaps or valves for example. In accordance with preferred forms of embodiment gas cleaning systems are provided at least in the collecting line and in 8 the removal line; for example dust removal systems or systems for removing NOx and SOx. The dust removal systems separate dust carried along from the mixed gas or the waste gas. The separated dust, where process technology allows, can be used again in the production of the sinter mixture. Brief description of the drawing Embodiments of the invention will be explained below with reference to a schematic example figure. Figure 1: schematic flow diagram of a device for sintering. Detailed Description Figure 1 shows a schematic flow diagram of a device for sintering metalliferous substances, such as for example iron ores or manganese walls, especially oxidic or carbonatic ores, on a sintering machine 1 - with a charging device 2 for feeding a sinter mixture 3 containing a solid fuel onto a sintering belt 4, - with suction boxes 5 for conveying process gas containing oxygen through the sinter mixture in three consecutive sections of the sintering belt, of which the first section adjoins the charging device and the third section is delimited by the ejection end 6 of the sintering belt 4, - with a collecting line 7 for combining and onward conveyance of the sintering waste gas arising in the suction boxes 5 of the third section and in the suction boxes 5 of the first section, 9 - with a removal line 8 for combining and onward conveyance of the sintering waste gas arising in the suction boxes 5 of the second section, - with a feedback device 9 for transport and for distribution of sintering waste gas as at least part of the process gas to the sinter mixture on the sintering belt, and - with a waste gas line 10 for removing sintering waste gas from the sintering machine. The feedback device 9 and the waste gas line 10 are connected by lines to the collecting line 7 and the removal line 8. Switchover devices 11, 12 are present in the collecting line 7 and in the removal line 8. These are suitable for directing sintering waste gas conveyed in the collecting line 7 or in the removal line 8 respectively either into the feedback device 9 or into the waste gas line 10. The switchover devices 11, 12 are shown as three-way valves. In one presentation of the area surrounded by a dashed line the switchover device 11 is set so that sintering waste gas from the collecting line 7 is fed back onto the sintering belt and sintering waste gas from the removal line 8 is directed into the waste gas line 10. In the other presentation of the area surrounded by a dashed line the switchover device 11 is set so that sintering waste gas from the removal line 8 is fed back onto the sintering belt and sintering waste gas from the collecting line 7 is directed into the waste line 10. Dust removal systems 13, 14 are present in the collecting line 7 and in the removal line 8. The feeding of oxygen to the fed-back sintering waste gas, for example by feeding cooling air of a sinter cooler not shown in the diagram, is not shown additionally for reasons of clarity.

10 Although the invention has been illustrated and described in greater detail by the preferred embodiments, the invention is not restricted by the disclosed examples and other variations can be derived therefrom by the person skilled in the art, without departing from the scope of protection of the invention.

11 List of reference numbers 1 Sintering machine 2 Charging device 3 Sinter mixture 4 Sintering belt 5 Suction boxes 6 Ejection end 7 Collecting line 8 Removal line 9 Feedback device 10 Waste gas line 11 Switchover device 12 Switchover device 13 Dust removal device 14 Dust removal device 12 List of cited documents Patent literature W02007/082694

Claims (3)

1. 2. The device of claim 1, wherein the metalliferous substances comprise iron ores or manganese ores. 14
2. 3. The device of claim 2, wherein the iron or manganese ores are oxidic or carbonatic ores.
3. 4. The device of claim 1, wherein the feedback device is configured to transport and distribute the sintering waste gas to the sinter mixture in the second section of the sintering belt. Siemens VAI Metals Technologies GmbH Patent Attorneys for the Applicant SPRUSON & FERGUSON