AU6565400A - Method for operating a melt-down gasifier - Google Patents

Description

Method of operating a fusion gasifier The invention relates to a method of operating a fusion gasifier in which iron-containing charge 5 materials, such as partly and/or fully reduced iron sponge, are fully reduced, if required, and are fused, with the addition of solid carbon carriers and the supply of an oxygen-containing gas - via a multiplicity of oxygen nozzles distributed around the circumference 10 of the fusion gasifier - in a fixed bed formed from the solid carbon carriers, to form liquid pig iron or a primary steel product with the simultaneous formation of a CO- and H 2 -containing reduction gas, the oxygen containing gas being passed via gas lines to the oxygen 15 nozzles, from where the oxygen-containing gas is blown into the fixed bed. The invention also relates to a fusion gasifier for carrying out the method according to the invention. In fusion gasifiers of the type mentioned 20 above, the supplying of the oxygen-containing gas takes place via a supply line to a bustle pipe surrounding the fusion gasifier. From this bustle pipe, the oxygen-containing gas is distributed via supply lines to the oxygen nozzles fitted on the circumference of 25 the fusion gasifier and is blown into the fusion gasifier or the fixed bed formed in it from the solid carbon carriers. During the operation of the fusion gasifier, permeability fluctuations of the fixed bed occur, 30 hindering or preventing gas, and consequently energy input, from taking place uniformly around the circumference. This causes the gas flow to be divided unevenly among the individual oxygen nozzles, with corresponding disadvantageous effects on the fusion 35 gasifying process. Since, in a fusion gasifier of solid carbon carriers a reduction gas, and consequently also the energy required for the melting of the iron sponge, is obtained by gasifying by means of oxygen-containing 40 gas, the supplying of the oxygen-containing gas also - 3 the gas lines in order to set a prescribed volume or mass flow of the oxygen-containing gas in the number of gas lines, or the oxygen nozzles corresponding to them. By means of the method according to the 5 invention it is possible for the first time to regulate individually each individual flow of the oxygen containing gas to the oxygen nozzles and to have a selective influence on the gas distribution in the fusion gasifier. 10 Until now, the pressure prevailing in the supply line upstream of the bustle pipe, of approximately 8 bar, has been throttled by means of a flow regulating member to a bustle pipe pressure of approximately 5 bar, which is the pressure that then 15 also prevails in the gas lines to the oxygen nozzles and at the oxygen nozzles themselves. The operating pressure of the fusion gasifier is approximately 4 bar, so that the pressure drop at the nozzle is only approximately 1 bar. 20 With the method according to the invention, it is now no longer necessary to reduce the pressure upstream of the bustle pipe, so that the high supply pressure of 8 bar now also prevails in the bustle pipe, and is then only throttled to 5 bar directly upstream 25 of each oxygen nozzle. The pressure drop at the nozzles is still approximately 1 bar. These statements initially apply only in the case of a uniformly gas-permeable fixed bed. As long as no permeability fluctuations of the fixed bed occur, 30 the supply of oxygen-containing gas is evenly distributed over the circumference of the fusion gasifier. If the gas-permeability problems described occur, it is possible with the method according to the 35 invention to counteract them by reducing the pressure depending on the particular desired flow rate - in the respective gas line to a greater or lesser degree, for example from 8 to 5 or to only 6 bar. While a variation of the pressure has in previous methods always applied to all the oxygen nozzles and permeability fluctuations of the fixed bed in the circumferential direction of the fusion gasifier caused the overall oxygen - and consequently the energy input 5 to the individual oxygen nozzles - to be divided unevenly, the solution according to the invention for the first time allows the oxygen input to be influenced locally and ensure that it is evenly divided by the individual flow regulation. 10 According to an advantageous embodiment of the method according to the invention, the regulation of the supply of oxygen-containing gas to each of the oxygen nozzles thus takes place in dependence on the pressure conditions prevailing in the fusion gasifier, 15 these pressure conditions - with respect to the oxygen nozzles - being determined by the respective permeability of the fixed bed, or fluctuations thereof. This regulation preferably takes place by the supply of the oxygen-containing gas to the oxygen nozzles 20 affected by the respective fluctuations being reset to a prescribed volume or mass flow. Regulating intervention expediently takes place only for the nozzles affected by the respective permeability fluctuations. 25 In particular, the procedure followed here is that a characteristic variable representative of the gas flow, in particular the volume flow and if required the pressure, is measured in a number of the gas lines. If there is a deviation from a prescribed setpoint 30 value, as described above, the pressure in the respective gas line is correspondingly regulated and consequently the desired gas flow is reset. The method according to the invention is also suitable for ensuring when there are tapping problems 35 proper tapping of liquid pig iron and liquid slag. For this purpose, when tapping is performed on the fusion gasifier, the supply of oxygen-containing gas to the oxygen nozzles located in the region of the tapping opening or above the tapping opening is - 5 throttled in order to ensure an adequate tapping length. As an alternative to this, or depending on the respective problem during tapping, the supply of 5 oxygen-containing gas to the oxygen nozzles located in the region of the tapping opening or above the tapping opening is increased in order to reduce an excessive tapping length. The method according to the invention is also 10 suitable for minimizing the loss of bed during tapping after stopping charging when the fusion gasifier is shut down. For this purpose, the supply of oxygen containing gas to oxygen nozzles far away from the tapping opening is initially throttled or stopped. 15 When supplying oxygen in the way according to the prior art, oxygen nozzles keep being blocked and damaged by penetrating liquid pig iron or liquid slag during scheduled shutdowns of the fusion gasifier. The method according to the invention also 20 reliably avoids such problems, in that the supply of oxygen-containing gas to individual oxygen nozzles is throttled in stages and/or continuously when the fusion gasifier is shut down. The permeability fluctuations of the fixed bed, occurring more frequently when the 25 fusion gasifier is shut down than otherwise, are reliably counteracted by the method according to the invention being further applied. The invention also relates to a fusion gasifier with charging devices for solid carbon carriers, such 30 as lump coal, and iron-containing charge materials, such as partly and/or fully reduced iron sponge, with a fusion gasifying zone, which contains a fixed bed formed by the solid carbon carriers and the iron containing charge materials, with a lower portion for 35 receiving liquid pig iron or primary steel product and liquid slag, with a run-off for liquid slag and liquid pig iron, with a multiplicity of oxygen nozzles, which are arranged in the shell of the fusion gasifier, with a bustle pipe, which annularly surrounds the shell of -6 the fusion gasifier and from which oxygen-containing gas can be supplied to the oxygen nozzles via gas lines, and with a supply line for oxygen-containing gas, which opens out into the bustle pipe. 5 Such a fusion gasifier is characterized according to the invention in that a regulating device for regulating the volume flow of the oxygen-containing gas is arranged in a number of gas lines. This arrangement of the regulating devices 10 according to the invention is outstandingly suitable for achieving the object set according to the invention, but further advantages are also obtained. According to the prior art, the oxygen supply is regulated by means of a single regulating valve in 15 the supply line to the bustle pipe. To cope with the large amounts of gas and high gas pressures, this valve must be correspondingly designed and is obtainable only as a specially made part. Furthermore, the noise produced when reducing the pressure from 8 to 5 bar is 20 so bad that it may be harmful to the health of, plant personnel. It has been found that, when smaller regulating devices, obtainable as mass-produced parts, are used, costs that are comparable overall are incurred - in 25 spite of the large number of these devices (about 20 to 30) - and in particular the noise nuisance is reduced significantly. It is particularly advantageous if, as according to a preferred embodiment, a regulating 30 device for regulating the volume flow of the oxygen containing gas is arranged in each of the gas lines. To make it possible that individual nozzles can be switched over from oxygen to nitrogen during operation, a nitrogen supply line expediently opens out 35 into the gas line upstream or downstream of the regulating device in a number of gas lines. Consequently, individual nozzles can be activated or deactivated sequentially and with different amounts of oxygen or nitrogen when the fusion gasifier is shut down or started up. As a result, a plant can be started up with a high system pressure, low amounts of oxygen and nevertheless oxygen outlet velocities that are adequate right from the outset. 5 It is also of advantage if the regulating device is arranged directly upstream of the oxygen nozzle in the direction of gas flow in a number of gas lines. This has the result - in the event of the 10 liquid phase penetrating into the nozzle channel - of providing a correction of the oxygen flow that is particularly rapid and restricted to the nozzle concerned and a particularly rapid gas pressure build up. This pressure build-up forces the liquid phase 15 back and consequently prevents or minimizes the damage. According to a preferred embodiment of the fusion gasifier according to the invention, measuring devices for sensing the pressure and/or the volume flow of the oxygen-containing gas and for supplying 20 corresponding actual signals to a controlling device are arranged in a number of gas lines, it being possible for setpoint values for the pressure and/or volume flow in the gas lines to be fed to the controlling device and for the regulating devices to be 25 controlled by the controlling device, separately from one another in each case, in dependence on a setpoint/actual-value comparison. The fusion gasifier according to the invention is explained in more detail below on the basis of the 30 embodiment represented in Figure 1 of the drawing. Figure 1 shows a vertical section through a fusion gasifier 1, which is charged from above with solid carbon carriers 4 and iron-containing charging materials 5 by means of charging devices 2, 3. The 35 carbon carriers 4 are preferably formed by lump coal and/or coke and/or coke briquettes, the iron-containing charging materials are preferably formed by partly and/or fully reduced iron sponge in the form of lumps or fine particles.

- 8 Arranged over the fusion gasifier 1 there is usually a reduction unit, for example a direct reduction shaft, in which iron-oxide-containing material is reduced by means of the reduction gas 5 generated in the fusion gasifier 1 to form the partly and/or fully reduced iron sponge. This iron sponge is transported out of the reduction shaft and fed to the fusion gasifier 1. In the fusion gasifying zone 6 of the fusion 10 gasifier 1 there forms a fixed bed 7, formed by the solid carbon carriers 4. An oxygen-containing gas, preferably industrial oxygen, as obtained for example from an air-separation plant, is blown into this fixed bed 7 via oxygen nozzles 8. In this case, the iron 15 containing charge materials 5 are melted to form liquid pig iron 9 and liquid slag 10, while at the same time forming a reduction gas. The reduction gas formed is drawn off from the fusion gasifier via a reduction-gas discharge line 11. 20 Liquid pig iron 9 and liquid slag accumulate in a lower portion 12 of the fusion gasifier 1 and are tapped via a run-off 13. Oxygen-containing gas is supplied initially via a supply line 14 to a bustle pipe 15 annularly 25 surrounding the fusion gasifier 1. From the bustle pipe 15, the oxygen nozzles 8 are fed via gas lines 16. The oxygen nozzles 8 are in this case arranged in the outer region of the shell 17 of the fusion gasifier 1 and are connected to the interior of the 30 fusion gasifier 1 via a drilled channel. Altogether approximately 20 to 30 oxygen nozzles 8 are arranged in the circumference of the fusion gasifier 1, respectively spaced apart more or less evenly from one another and arranged essentially 35 at the same height, so that the oxygen-containing gas is blown obliquely downwards into the lower region of the fixed bed 7. Provided in each of the gas lines 16 is a measuring device 18 for measuring the pressure and/or - 9 volume flow of the oxygen-containing gas. Corresponding measuring signals are supplied to a controlling device 19, which can be fed at least a setpoint value 20 for the volume flow. 5 In a fusion gasifier with a production of, for example, 100 t of pig iron/h, a consumption of 100 t of coal/h, 26 oxygen nozzles and an admission pressure prevailing at the oxygen nozzles of 5 bar, the setpoint volume-flow value through each of the gas lines 16 is, 10 for example, approximately 1600 Nm 3 /h. Respectively arranged upstream of the measuring device 18 in each of the gas lines 16 is a regulating device 21, for example a valve or an adjustable flap. If the measured volume flow deviates from the 15 prescribed setpoint value, the desired volume flow is reset by the controlling device 19 by means of the regulating device 21. The supply of oxygen-containing gas is regulated in a way according to the prior art by means 20 of the valve 22 represented by dashed lines in the drawing. For switching over from blowing in oxygen to blowing in nitrogen, a nitrogen supply line 23 is arranged directly downstream of the regulating device 25 21 in one of the gas lines 16. The invention is not restricted to the exemplary embodiment represented in Figure 1, but instead also comprises all means known to a person skilled in the art that can be used for carrying out 30 the invention. For example, nitrogen supply lines 23 may open out into some or all of the gas lines 16 upstream or downstream of the regulating device 21. Where they have not already been described 35 above, further effects and advantages of the method according to the invention, as well as the fusion gasifier according to the invention, are also presented below.

- 10 Correction of permeability deviations: The local adaptation of the amount of oxygen is used for changing the amount of gas generated in this 5 area when gasifying the carbon carriers. The resultant changing of the gas velocities in the feedstock can correct and eliminate permeability problems such as gas channels, fluidized zones, etc. In addition, an individual adaptation of the 10 depth of penetration takes place in parallel with this. With the system pressure remaining the same, the depth of penetration of the oxygen jet into the bed, and consequently the energy density and gas distribution in an area directly around the nozzle, can consequently be 15 locally adapted in a way corresponding to the permeability problems that have occurred. * Energy input 20 - Local adaptation of the energy input Inhomogeneous charging, such as for example adaptation of the discharge output of the iron-sponge screws to the shaft conditions, failure of an iron 25 sponge screw, segregation effects, etc., cause an energy requirement in the fusion gasifier that differs locally. With the individual regulation of the amount of oxygen to the nozzles, the energy requirement and energy input can be made to match each other locally. 30 - Correction of different nozzle geometries It may be advisable to set local deviations of the energy input on a long-term basis in various areas 35 of the fusion gasifier. To maintain the optimum oxygen outlet velocity, in this case nozzles with an adapted oxygen channel diameter are used. For example, nozzles with a smaller channel are often installed in the tapping area, in order to permit the build-up of a - 11 stable, large tapping length by the lower energy input. In the event of operational problems, it may be necessary to adapt the reduced energy input. With the individual regulation of the amount of oxygen, this can 5 be carried out reversibly at any time without nozzle changes and the associated downtime. * Formation of deposits above the ring of nozzles 10 In the area of the melt phases above the ring of nozzles, the gasifier cooling system causes the formation of deposits. On the one hand, these deposits are desired to protect the masonry and cooling system, on the other hand process-related problems can occur if 15 they are formed excessively. By locally adapting the energy input (amount, depth of penetration), the position of the temperature profile can be selectively influenced. Problematical deposits on the one hand can be melted away, protective layers on the other hand can 20 be selectively built up. * Metallurgical load on the furnace The period of a campaign is determined essentially by 25 the durability of the masonry in the furnace. Long service lives can be achieved only by "self lining". Advanced wear and loss of the self lining are demonstrated by thermocouples and in the tapping area by regression of the tapping length. In a way similar 30 to controlling deposits above the nozzles, protective layers can be built up or preserved in critical areas by local adaptation of the energy input. On the other hand, inactive areas of the furnace may be re-activated by a locally increased energy input. For example, when 35 the furnace is cold, the front region directly above the run-off that is particularly important for the removal of the liquid phase can be used to a greater extent.

- 12 * Tapping problems - Build-up/reduction of the tapping length 5 In the tapping area, the liquid flow causes increased wearing of the masonry, generally compensated by pressing in tap-hole composition. If shortening of the tapping length nevertheless occurs, the metallurgical load on the furnace can be locally 10 reduced by reducing the energy input via the front nozzles, helping to build up an adequate tapping length. Excessive tapping lengths, which hinder the outlet of the liquid phase, can be reduced by increasing the energy input in the tapping area. 15 - Reduction of the gas pressure in the tapping area Excessive gas outlet in the tapping area disturbs the uniform, controlled and steady outlet of 20 liquid and causes critical refractory damage. In extreme cases, operation of the plant can no longer be maintained. Gas compounds build up with preference in the area of the "Brustformen" (oxygen nozzles above the run-off) to the run-off. By selectively cutting back 25 the amount of oxygen to the nozzles concerned, the gas pressure at the run-off can be reduced. * Nozzle damage 30 A frequent reason for nozzle damage is the penetration of the liquid phase into the oxygen channel. As a result, the liquid pressure upstream of the nozzles must be able to force back the emerging oxygen jet, at least for a short time. 35 - 13 - Maintaining the inlet pulse when there are permeability problems Permeability problems of the bed or high liquid 5 pressure upstream of nozzles cause the amount of oxygen of the nozzles concerned and consequently the inlet pulse to be reduced. These nozzles become more susceptible to the inlet of liquid phases into the oxygen channel. With the individual regulation, the 10 amount of oxygen per nozzle is corrected independently of the state upstream of the nozzles; as a result, the inlet pulse remains largely unchanged. - Controlling the amount of oxygen when the oxygen 15 channel widens If, after penetrating into the nozzle, the liquid phase is forced back again by the oxygen jet, the oxygen channel usually has larger dimensions than 20 desired. As a result, when regulated altogether, the amount of oxygen via the damaged nozzle increases. When regulated individually, the amount can be adapted to the requirements of the process, independently of the form taken by the damage. 25 e Drainage of the liquid phase If the bed has an inadequate voids fraction, undesired accumulation of the liquid phase may occur in the area 30 above the oxygen nozzles. This liquid phase can be drained more easily into the furnace beneath the nozzles by cutting back the amount of oxygen locally, for a limited time, possibly on a cyclical basis, and consequently cutting back the amount of gas acting 35 against the flowing away of the liquid phase. If the drainage beneath the nozzles is inadequately ensured locally, reduction of the amount of oxygen can reduce the loading of this area with the liquid phase and consequently prevent nozzle damage and - 14 operational problems. e Bed hangers 5 In gas/feedstock countercurrent reactors, material flow problems ("hangers") are known when critical parameters (gas velocity, particle spectrum, etc.) are exceeded. It is conceivable for hangers of this type to occur in the bed above the nozzles, leading to considerable 10 inhomogeneities in the gas permeation, uneven sinking of the bed and consequently an unstable process. Cutting back the amount of oxygen locally, for a limited time, possibly on a cyclical basis, can reduce the amount of gas generated to the extent that the 15 occurrence of hangers is eliminated at an early stage and major process-related problems can be avoided. * Water/steam injection 20 One possible way of setting the temperature profile upstream of the nozzles is water/steam injection. According to process conditions, the amount of water/steam can be divided among individual nozzles evenly or individually. With the individual regulation 25 of the amount of oxygen, the energy input can correspondingly be matched to the water/steam injection rate.

Claims (6)

1. Method of operating a fusion gasifier in which iron-containing charge materials, such as partly and/or 5 fully reduced iron sponge, are fully reduced, if required, and are fused, with the addition of solid carbon carriers and the supply of an oxygen-containing gas - via a multiplicity of oxygen nozzles distributed around the circumference of the fusion gasifier - in a 10 fixed bed formed from the solid carbon carriers, to form liquid pig iron or a primary steel product with the simultaneous formation of a CO- and H 2 -containing reduction gas, the oxygen-containing gas being passed via gas lines to the oxygen nozzles, from where the 15 oxygen-containing gas is blown into the fixed bed, characterized in that the supply of the oxygen containing gas to the oxygen nozzles is regulated individually in a number of the gas lines in order to set a prescribed volume or mass flow of the oxygen 20 containing gas in the number of gas lines, or the oxygen nozzles corresponding to them.

2. Method according to Claim 1, characterized in that, when there are local permeability fluctuations of the fixed bed within the fusion gasifier and resultant 25 pressure and flow fluctuations in individual gas lines, the supply of the oxygen-containing gas to the oxygen nozzles affected by the respective fluctuations is reset to a prescribed volume or mass flow.

3. Method according to either of Claims 1 and 2, 30 characterized in that a characteristic variable representative of the gas flow, in particular the volume flow and if required the pressure, is measured in a number of the gas lines and, if. there is a deviation from a prescribed setpoint value, the 35 pressure of the oxygen-containing gas in the respective gas line is increased or reduced.

4. Method according to one of Claims 1 to 3, characterized in that, when tapping is performed on the fusion gasifier, the supply of oxygen-containing gas to - 17 9. Fusion gasifier (1) according to one of Claims 7 or 8, characterized in that a nitrogen supply line (23) opens out into the gas line (16) upstream or downstream of the regulating device (21) in a number of 5 gas lines (16).

10. Fusion gasifier (1) according to one of Claims 7 to 9, characterized in that the regulating device (21) is arranged directly upstream of the oxygen nozzle (8) in the direction of gas flow in a number of gas 10 lines (16).

11. Fusion gasifier (1) according to Claims 7 to 10, characterized in that measuring devices (18) for sensing the pressure and/or the volume flow of the oxygen-containing gas and for supplying corresponding 15 actual signals to a controlling device (19) are arranged in a number of gas lines (16), it being possible for setpoint values (20) for pressure and/or volume flow in the gas lines (16) to be fed from outside to the controlling device (19) and for the 20 regulating devices (21) to be controlled by the controlling device (19), separately from one another in each case, in dependence on a setpoint/actual-value comparison.