CN111328349B

CN111328349B - Injection of process fluids into a shaft furnace with injector condition testing

Info

Publication number: CN111328349B
Application number: CN201880049781.XA
Authority: CN
Inventors: 弗兰克·莱克尔
Original assignee: LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Current assignee: LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date: 2017-06-22
Filing date: 2018-06-21
Publication date: 2022-06-10
Anticipated expiration: 2038-06-21
Also published as: WO2018234481A1; EP3642370A1; RU2020101703A3; EP3642370B1; CN111328349A; RU2020101703A

Abstract

Injecting a process fluid into a shaft furnace through n injectors, wherein the status of the n injectors is tested by: supplying a test fluid to each injector at a predetermined pressure, measuring a flow rate of the respective test fluid through the injector and comparing the measured test fluid flow rate to a predetermined safe flow rate range; or supplying a test fluid to each injector at a predetermined flow rate, measuring the pressure drop across the injector or nozzle portion thereof and comparing the measured pressure drop to a predetermined safety pressure drop range.

Description

Injection of process fluids into a shaft furnace with injector condition testing

The invention relates to the operation of a shaft furnace.

The term "shaft furnace" refers to a vertical shaft furnace or a cylindrical furnace in which combustion occurs. Examples of shaft furnaces are cupola furnaces and blast furnaces. Examples of such processes using shaft furnaces include, but are not limited to, burning solid waste, reducing iron ore to produce pig iron, melting metals and mineral wool, and the like.

It is known in the art to inject a fluid such as an oxygen-rich gas into a shaft furnace.

In order to ensure a relatively high degree of penetration of the fluid into the shaft furnace, it is more particularly known to inject the fluid into the shaft furnace at sonic or supersonic velocities.

Injection is achieved by a set of lances, also known as injectors or tuyeres, which are distributed around the furnace.

These injectors have to operate under particularly harsh conditions and are easily damaged. In particular, the high temperatures inside the shaft furnace may cause the injector to suffer thermal damage such as cracking, partial melting or softening and deformation, and deposits may form on and/or around the injector that may partially or even completely block the injection opening of the injector or change the direction in which fluid is injected into the shaft furnace.

It will be appreciated that any damage to the injector that affects the injection of fluid into the shaft furnace can have a significant adverse effect on the furnace and the process being carried out in the furnace. For example, a change in the orientation of the injection direction of the fluid may result in damage to the refractory walls of the furnace and reduce the efficiency of the process carried out in the furnace and/or the quality of the product obtained. Any damage to the injector nozzle, in particular to sonic or supersonic nozzles, may reduce the injection velocity of the fluid and thus the penetration depth of the fluid in the shaft furnace. Damage to the injector may also lead to potentially catastrophic flashback when the fluid injected by the injector includes fuel.

It is therefore necessary to replace any injector that apparently has suffered damage.

Since many shaft furnaces operate continuously for long periods of time, it is often not possible to check the condition of the injectors from the inside of the furnace.

It is common practice, by precautionary measures, to replace all injectors of a shaft furnace after a predetermined operating period (so-called maximum life).

The maximum lifetime is selected based on testing and/or previous experience with the same type of injector so as to be short enough that most injectors are replaced before the injector has suffered any damage that causes significant deterioration in the furnace structure or the process being performed in the furnace. Thus, many injectors will be replaced even though they have not been damaged.

The shaft furnace may have a large number of injectors. Depending on the size and type of furnace and the process carried out in the furnace, it is not uncommon for up to 14 or 16, or even up to 24 or 26, or even more injectors to be used to inject the same fluid into the shaft furnace.

Therefore, replacing the injector costs the furnace operator a significant amount of cost, both with respect to the material to be replaced and the labor required.

It is therefore desirable to be able to use injectors for longer periods of operation without increasing the risk of safety, damage to the furnace structure or deterioration of the process carried out in the furnace.

US-A-3346249 discloses A method for supplying blast air and gaseous fuel to A blast furnace viA A large number (30 to 40 mentioned) of continuously operating tuyeres and corresponding continuously operating fuel injection pipes, respectively, wherein A fuel controller stops the flow of fuel to the fuel injection pipes when A blockage or partial blockage of the fuel injection pipes or the corresponding tuyeres is detected. A differential pressure gauge is positioned across an orifice in a gas supply line connecting a single fuel injection tube to the gaseous fuel ring manifold. When an obstruction in a single fuel injection pipe causes fuel maldistribution with other single fuel injection pipes, the differential pressure gauge detects a change in pressure across the orifice of the supply line to the single fuel injection pipe and generates an alarm signal. Each tuyere is further equipped with a heat induction device and a pitot tube. When the thermal induction means detect an increase in temperature indicative of the combustion of the fuel inside the single tuyere, and when the pitot tube detects that the tuyere is blocked or partially blocked, an alarm signal is generated and the flow of fuel to the respective injection pipe is stopped.

The method according to US-A-3346249 is only suitable for detecting blockages or blockages of injection pipes and tuyeres that operate continuously and at A substantially constant flow rate. It is not suitable for detecting clogging or clogging of the injector during pulsed or alternating injection of fluid. In addition, since the detection is performed while all the fuel injection tubes are fluidly connected to the annular air duct, and while all the tuyeres are fluidly connected to the annular air duct, the pressure at which the gas is supplied to the single tuyere and injection tube and the flow rate at which the gas is supplied to the single tuyere and injection tube are determined not only by the air pressure and flow rate in the annular air duct and the annular air duct, respectively, but also by the conditions of the other tuyeres and injection tubes connected to the annular air duct and the annular air duct, respectively. Due to this interference between the different tuyeres and the injection pipe, some instances of blockage or partial blockage may not be detected. The present invention proposes a method for injecting a process fluid into a vertical shaft furnace in which a combustion process is carried out, wherein the injector for injecting said process fluid into the shaft furnace is subjected to a status check without interrupting the operation of the shaft furnace. The invention further proposes such a method which is suitable for injecting a process fluid into a shaft furnace discontinuously, in particular pulsed or alternately. The present invention therefore relates to a method of injecting a process fluid into a vertical shaft furnace in which a combustion process is carried out.

The shaft furnace has n injectors, n being at least equal to 3, distributed around the circumference of the shaft furnace. The shaft furnace also has a fluid distributor which is in fluid connection with the source of the process fluid to be injected on the one hand and with the n injectors on the other hand.

The shaft furnace is further part of an apparatus comprising a control unit programmed to: (a) controlling the total amount of process fluid injected into the shaft furnace through the n injectors by means of a first valve unit between the source of process fluid and the fluid distributor; and (b) controlling the flow of process fluid from the fluid distributor to each of the n injectors by n individual valve units between the fluid distributor and the n injectors.

According to the invention, the control unit is also programmed to start and perform a status test for each of the n injectors individually, without interrupting the operation of the shaft furnace.

During a condition test of one of the n injectors, a test fluid is supplied to said injector at a predetermined pressure or at a predetermined flow rate, whereupon said test fluid is also injected into the shaft furnace through said injector.

When the test fluid is supplied to the injector at a predetermined pressure, the flow rate of the fluid through the injector is measured. A pressure drop or back pressure is measured across the injector or across at least one nozzle portion of the injector when the test fluid is supplied to the injector at a predetermined flow rate.

When a test fluid is supplied to the injector at a predetermined pressure and the flow rate of the fluid through the injector is thus measured, the control unit verifies whether the measured flow rate falls within a predetermined flow rate range for the predetermined pressure (meaning a "safe" flow rate range for said pressure). When the test fluid is supplied to the injector at a predetermined flow rate and the pressure drop is taken into account, the control unit verifies whether the measured pressure drop falls within a predetermined pressure drop range for the predetermined flow rate (meaning a "safe" pressure drop range for said flow rate).

When the measured flow rate does not fall within the predetermined safety flow rate range or when the measured pressure drop does not fall within the predetermined safety pressure drop range, the control unit issues an output signal indicating that the injector (i.e. the injector that has been tested for condition) has to be replaced.

In fact, when the measured flow rate does not fall within the predetermined safety flow rate range or when the measured pressure drop does not fall within the predetermined safety pressure drop range, this clearly indicates that the injector has been damaged, so that the flow performance of the injector has been affected to such an extent that the injector has to be replaced.

The present invention thus provides a furnace with a reasonable indication of the status of the n injectors during the combustion process.

The method according to the invention may comprise the step of determining a pressure, referred to as "predetermined pressure", and a flow rate, referred to as "predetermined flow rate", at which the test fluid is (to be) supplied to the injector under test during the condition test.

The predetermined pressure and the predetermined flow rate typically correspond to the fluid pressure and the fluid flow rate at which the injector is designed or commercially used.

A method according to the present invention may include the step of determining a flow rate range, which refers to a "predetermined safe flow rate range" for an injector at a predetermined pressure of the test fluid, and a pressure drop range, which refers to a "predetermined safe pressure drop range" across the injector at a predetermined flow rate of the test fluid through the injector. The "predetermined safe flow rate range" and the "predetermined safe pressure drop range" may be provided by the manufacturer or supplier of the injector, or may be based on earlier experience with the same type of injector.

The predetermined safe flow rate range for the predetermined pressure and the predetermined safe pressure drop range for the predetermined flow rate typically correspond to the range of flow rates observed when the test fluid is supplied to a new, unused injector of the same type at the predetermined pressure and the range of pressure drops observed when the test fluid is supplied to such a new, unused injector at the predetermined flow rate, respectively.

Advantageously, the control unit is programmed to repeat the status check for each of the n injectors at predetermined intervals, thus informing the furnace of the evolution of the status of the n injectors during the combustion process.

Alternatively or in combination therewith, the method may enable initiation of a status check for each of the n injectors by the control unit by instructing the control unit to act (e.g., by a touch screen or remote control of the control unit). The furnace operator particularly wishes to initiate a status check of the injectors after or before an event related to the shaft furnace, for example after an injector has been replaced or before a process change is made in the shaft furnace.

As a result of the status check or checks performed by the control unit, the furnace operator no longer has to rely solely on the experimentally determined maximum lifetime of the injector, and may decide to continue to use an injector that exceeds said maximum lifetime, as long as the status check has indicated that the injector continues to operate within a safe range.

The output signal generated by the control unit may be or may comprise a visual output signal on a screen of the control unit, optionally accompanied by a sound signal. The output signal may also be or include a signal that is transmitted to a remote device, typically a handheld or mobile device.

The process fluid may in particular be an oxidizing gas in the shaft furnace which is consumed by the combustion process. The oxidizing gas preferably has an oxygen content of more than 21% vol and up to 100% vol, preferably at least 90% vol, more preferably at least 95% vol.

The oxidizing gas source may be a means for flooding air with oxygen, typically when the oxygen content in the oxidizing gas is relatively low (e.g., greater than 21% vol and no greater than 90% vol). The source of the oxidizing gas may also be an air separation unit, a liquefied oxygen storage tank, or a conduit for transporting liquefied oxygen, for example when the oxygen content of the oxidizing gas is between 90% vol and 100% vol, preferably at least 95% vol.

The process fluid may also be or comprise fuel which is injected into the shaft furnace.

The process fluid can also be used for other purposes in the shaft furnace. For example, where the shaft furnace is used to reduce iron ore, the process fluid may be a reductant that is injected into the shaft furnace to facilitate the reduction of the iron ore.

The shaft furnace typically has a substantially circular circumference, but may also have a different shape, for example a rectangular circumference.

The n injectors are preferably substantially equally or evenly distributed around the circumference of the shaft furnace, although other configurations are possible depending on the furnace structure and process requirements.

The number n of said injectors is generally greater than 3. A number of as many as 14 or 16 injectors may be employed. However, the number n of injectors may also be significantly larger, for example up to 24 or even up to 36 or more.

The fluid distributor is advantageously a fluid distribution ring surrounding the shaft furnace.

According to a first embodiment of the method according to the invention, a process fluid is used as the test fluid. In that case, to ensure that the test fluid is effectively supplied to the injector to be tested for conditions at a predetermined pressure or at a predetermined flow rate, the control unit closes n-1 individual valves between the fluid distributor and n-1 other injectors. As a result, during the supply of the test fluid to the injector to be tested for condition, all of the process fluid supplied to the fluid distributor flows only to the injector to be tested for condition, and flows at a predetermined pressure or at a predetermined flow rate. During this time, no process fluid flows from the fluid distributor to the n-1 other injectors so that the n-1 other injectors do not interfere with the ongoing condition testing. To ensure that the test fluid is effectively supplied to the injector to be tested for conditions at a predetermined pressure or at a predetermined flow rate, the control unit may also adjust the first valve unit between the source of process fluid to the fluid distributor to adjust the flow rate and/or pressure of the process fluid (used as test fluid) flowing into the fluid distributor. The control unit may be programmed to control the flow of process fluid from the fluid distributor to each of the n injectors such that the injectors continuously inject process fluid into the furnace between condition tests. Alternatively, the control unit may be programmed to control the flow of process fluid from the fluid distributor to each of the n injectors so that the injectors inject process fluid into the furnace in a pulsed or alternating manner between status tests.

An advantage of this embodiment is that no additional equipment is required for the condition test. A disadvantage of this embodiment is that the flow of process fluid to n-1 other injectors is temporarily interrupted. This is not a problem if the interruption that must be repeated for the status test for each injector is short enough and if the process being performed in the furnace is less susceptible to such interruption.

In other cases, the following embodiments in which a fluid other than the process fluid is used as the test fluid may be more useful, although this requires some additional equipment. According to said another embodiment, during the supply of the test fluid to the injector to be tested, the control unit performs the following operations:

(a) closing a single valve connecting an injector to be tested for conditions to a fluid distributor so that no process fluid flows from the fluid distributor to the injector, an

(b) Opening a test fluid valve between a test fluid source and the injector such that test fluid is supplied to the injector at a predetermined pressure or at a predetermined flow rate.

Thus, during the condition test, the process fluid can continue to flow to the n-1 other injectors under the control of the control unit, and the disturbance of the process in the shaft furnace is minimal.

In that case, the control unit may be programmed to control the flow of process fluid from the fluid distributor to each of the n injectors so that the process fluid is continuously injected into the furnace when said injector is not subjected to the condition test according to the invention. Alternatively, the control unit may be programmed to control the flow of process fluid from the fluid distributor to each of the n injectors such that the injectors inject process fluid into the furnace in a pulsed or alternating manner when not being subjected to a condition test.

Although in this case the test fluid may have the same or similar composition as the process fluid, it is preferred to select a test fluid that does not react with other chemical components present in the shaft furnace in order to further limit the influence of the condition test on the process in the shaft furnace.

The test fluid may be, for example, air, N₂、CO₂Or recirculating flue gas.

According to a convenient embodiment, the test fluid distributor is a test fluid distribution ring surrounding the shaft furnace, thereby facilitating the supply of test fluid to the n individual injectors during their respective condition tests.

When it is considered that some insubstantial damage to the injectors is permissible and that these injectors do not need to be replaced, the predetermined safe flow rate range or the predetermined safe pressure drop range may be selected to encompass the flow characteristics of the injectors with such insubstantial damage. In that case, it may still be useful for the furnace to be able to distinguish between a substantially intact injector and an injector that is only substantially damaged. Thus, a distinction may be made between a standard range corresponding to substantially intact injectors and a warning range corresponding to injectors that are only substantially non-defective.

In that case, when the test fluid is supplied to the injector at a predetermined pressure, the predetermined safe flow rate range consists of a predetermined standard flow rate range and predetermined warning flow rate ranges on both sides of the standard flow rate range. The control unit verifies whether the measured flow rate falls outside the standard flow rate range but within the warning flow rate range. When the measured flow rate does fall within the warning flow rate range, the control unit issues an output signal indicating that the injector that has been tested for status is no longer operating under its standard operating conditions.

Similarly, when the test fluid is supplied to the injector at a predetermined flow rate, the predetermined safe pressure drop range consists of a predetermined standard pressure drop range and predetermined warning pressure drop ranges on either side of the standard pressure drop range. The control unit verifies whether the measured pressure drop falls outside the standard pressure drop range but within the warning pressure drop range. When the measured pressure drop falls within the warning pressure drop range, the control unit issues an output signal indicating that the injector that has been tested for condition is no longer operating under its standard operating conditions.

The predetermined standard flow rate range for the predetermined pressure and the predetermined standard pressure drop range for the predetermined flow rate typically correspond to the range of flow rates observed when the test fluid is supplied to a new, unused injector of the same type at the predetermined pressure and the range of pressure drops observed when the test fluid is supplied to such a new, unused injector at the predetermined flow rate, respectively. However, the predetermined standard flow rate range is narrower than the predetermined safety flow rate range, and the predetermined standard pressure drop range is narrower than the predetermined safety pressure drop range.

The method according to the invention may comprise the step of determining a flow rate range, referred to as "predetermined standard flow rate range", and a pressure drop range, referred to as "predetermined standard pressure drop range". The "predetermined standard flow rate range" and the "predetermined standard pressure drop range" may be provided by the manufacturer or supplier of the injector, or may be based on earlier experience with the same type of injector.

For additional security, the method according to the invention may also be combined with the aforementioned maximum lifetime method. However, since information about the actual state of the injector is available by the method of the invention, a longer maximum lifetime or maximum run time can be safely selected.

In that case, the control unit preferably also keeps track of the run time of each of the n injectors. When the actual run time of one of the n injectors reaches a predetermined maximum run time, the control unit generates an output signal indicating that the injector has reached its maximum run time, whereupon the injector will typically be replaced by a furnace operator.

According to one embodiment, the control unit is programmed to start and perform the status test for each of the n injectors in turn, without interruption between two consecutive status tests of different injectors. Alternatively, the control unit may be programmed to initiate and perform a status test for each of the n injectors with an interval of no status test between two consecutive status tests of different injectors. The latter embodiment may be useful when extending the condition check for a longer period of time may have a negative impact on the process performed in the shaft furnace.

The shaft furnace may be a waste combustion furnace. However, the invention is particularly useful when the furnace is a furnace for converting charge material in addition to fuel combusted with oxidant. The invention is therefore particularly useful when the shaft furnace is a glass furnace, a mineral wool furnace or a metal furnace.

The shaft furnace may be a cupola furnace. The shaft furnace may also be an iron making blast furnace.

The invention and its advantages are illustrated in the following examples with reference to fig. 1 to 3, in which:

FIG. 1 is a schematic representation of a first embodiment of an apparatus for melting cast iron and suitable for use in the method of the invention, a cross-sectional representation of a cupola furnace including the apparatus,

FIG. 2 is a schematic representation of a second embodiment of such a device, an

FIG. 3 is a partially schematic representation of a screenshot of a user interface suitable for use in the context of the present invention.

The shaft furnace 10 of fig. 1 and 2 has a substantially circular cross-section. At the top end 11 of the shaft furnace 10 a charge 20 of metal to be melted (cast iron) and coke is introduced. Flux materials are also typically introduced in this manner. The charge material 20 is typically introduced so as to form a continuous horizontal layer (e.g., a layer of metal) within the shaft furnace 10, followed by a layer of coke, followed by a layer of flux, followed by a layer of metal, etc. The coke is combusted with the combustion oxidant in a combustion zone 12 located further down in the shaft furnace 10. In addition, combustion oxidant is injected into the shaft furnace 10 through oxidant injectors or tuyeres 30 positioned about the combustion zone 12.

The heat of combustion melts the metal in the charge immediately above the combustion zone 12 and the molten metal drips through the combustion zone 12 into the bottom region 13 of the furnace. The combustion gases generated in the combustion zone 12 move further upwards through the stratified charge, thereby preheating the charge until the combustion gases are removed from the shaft furnace via the flue gas outlet 16. Molten metal is removed from the bottom region 13 of the shaft furnace 10 via a tapping spout 14. Slag formed during the melting process is removed from the shaft furnace 10 via a tapping spout 15 located at a height above the height of the tapping spout 14.

The control unit 40 controls the operation of the shaft furnace 10.

In the illustrated embodiment, six (6) oxidant tuyeres 30 are equally distributed around the combustion zone 12 of the shaft furnace 10. Each oxidizer tuyere 30 is individually connected to an oxidizer distributor in the form of an oxidizer ring 31 surrounding the shaft furnace 10. The oxidant ring 31 is supplied with combustion oxidant from an oxidant source such as an air separation unit or oxygen reservoir (not shown). A valve 32 is used to control the flow of oxidant from the oxidant source to the oxidant distributor 31. Valves 33 are used to control the flow of oxidant from the oxidant distributor 31 to the individual oxidant tuyeres 30, one valve 33 for each oxidant tuyere 30. The function of the individual valves 32, 33 is controlled by or via the control unit 40.

In the embodiment illustrated in fig. 1 and 2, the oxidant tuyere 30 is a tuyere for injecting oxygen having a purity of between 90% vol and 100% vol, preferably at least 95% vol. In order to be able to inject oxygen into the shaft furnace 10 at sonic or supersonic velocity, each tuyere 30 is equipped with a laval nozzle 34.

According to a preferred embodiment, when all the oxidant tuyeres 30 inject said oxidant into the furnace 10 at sonic or supersonic speed, the central control unit 40 preferably causes the valve 33 to open and close so as to achieve a pulsed injection of said oxidant, as described for example in DE-a-10249235, when the total rate of oxidant injection into the furnace 10 is lower than the rate of oxidant injection into the furnace 10, wherein the tuyeres 30 alternate between active phases during which the tuyeres 30 inject the oxidant at sonic or supersonic speed, and passive phases during which said tuyeres 30 do not inject the oxidant into the furnace 30, or at subsonic speed and at a rate that is a fraction of the rate of oxidant injection during the active phases of said tuyeres 30.

It should be understood that the illustrated embodiment is but one of many possible embodiments. For example, the charge 20 may be introduced into the shaft furnace 10 via a shaft door in the enclosure 17 of the furnace 10 at the top end 11, rather than through the roof of the furnace 10. The combustion gases may be discharged from the furnace 10 via gas outlets in the ceiling of the furnace 10, rather than via the flue gas outlet 16 in the enclosure 17.

The number of oxidant tuyeres 30 may be greater or less than in the illustrated embodiment. Additional fuel, such as coal, fuel oil, or gaseous fuel, may also be introduced into combustion zone 12. The additional fuel can be introduced into the furnace 10 via the fuel tuyeres, via the burners, or, particularly in the case of solid particulate additional fuel, directly through the oxidant tuyeres 30, which can be separate from the oxidant tuyeres, or can form a tuyere aggregate with the oxidant tuyeres 30 (or some of the oxidant tuyeres). The furnace 10 may also include multiple sets of tuyeres for combusting the oxidant. For example, a set of air tuyeres for injecting air (which may or may not be enriched with oxygen) may be connected to the wind ring around the shaft furnace, and a set of oxygen tuyeres may be connected to a separate oxygen ring around the shaft furnace.

In the embodiment shown in fig. 1, when the control unit 40 initiates a condition test of one of the oxidant injectors or tuyeres 30, the valve 33 corresponding to the oxidant tuyere 30 to be tested is opened or kept open and the valves 33 corresponding to the other tuyeres 30 are closed so as to bring said other oxidant tuyeres 30 in fluid disconnection from the oxidant ring 31. In this way, the pressure or flow rate at which oxidant from oxidant ring 31 is supplied to oxidant tuyere 30 under test can be adjusted to correspond to a predetermined test level without interference from other tuyeres 30.

According to the present invention, when oxidant from oxidant ring 31 is supplied to injector 30 under test at the predetermined pressure during a condition test, sensor 35 determines the flow rate of the oxidant through injector 30 under condition test. Similarly, when oxidant from oxidant ring 31 is supplied to the injector 30 under test at a predetermined flow rate during a condition test, sensor 35 determines the pressure drop or back pressure on the injector 30 or on at least the laval nozzle portion 34 of the injector 30.

The flow rate and pressure determined by the sensor 35 are transmitted to the control unit 40, where the determined values are compared with predetermined safety parameter ranges for the flow rate and pressure of the tuyere 30 to be tested under the condition of the state test. When the determined value is outside of the predetermined safety parameter range, an alarm signal is sent to the furnace crew, for example via a user interface such as a monitor screen and/or a mobile device such as a smart phone, so that the furnace crew can take the necessary action to replace the failed tuyere 30.

In addition to comparing the determined value to a predetermined safety parameter range, the determined value may also be compared to a predetermined warning parameter range that is within the safety parameter range but outside the standard range of the parameter. When the determined value is within the predetermined safety parameter range, but also within the predetermined warning range of said parameter, the fireman receives the warning signal, thus allowing the fireman to prepare or plan in advance the replacement of the respective tuyere 30 and, if necessary, to order a new replacement tuyere. However, in the case of an alarm signal, immediate action is typically required, which is not the case for an alarm signal as described in this paragraph.

After the status test of the tuyeres 30 is completed, the control unit 40 may resume the injection of oxidant through the six tuyeres 30 to the normal iron melting operation in the shaft furnace 10 and initiate the status test of one of the other tuyeres 30 at a later time (typically a pre-programmed time). Alternatively, the control unit 40 may initiate the status test of each oxidant tuyere 30 successively (i.e. one after the other) and only after the status of all six tuyeres 30 has been tested, the injection of oxidant through the six tuyeres 30 is resumed to normal iron melting operation in the shaft furnace 10.

In an alternative embodiment shown in fig. 2, a test fluid distributor or ring 50 also surrounds the enclosure 17 of the furnace 10 in the vicinity of the oxidant tuyeres 30. A single connector 51 is provided between the test fluid ring 50 and each of the oxidant tuyeres 30, each connector 51 being equipped with an on-off valve 52 for fluidly connecting or disconnecting the respective oxidant tuyere 30 to the test fluid ring 50. During normal operation of the shaft furnace 10, all on-off valves 52 are closed, so that none of the oxidant tuyeres 30 are in fluid connection with the test fluid ring 50. When the control unit 40 initiates a status test of one of the oxidant injectors or tuyeres 30, the valve 33 corresponding to the oxidant tuyere 30 to be tested is completely closed and the valves 51 corresponding to said oxidant tuyere 30 are opened while the remaining valves 51 corresponding to the other oxidant tuyeres 30 remain closed. During the condition test, the test fluid from the test fluid ring 50 is supplied to the oxidant tuyere 30 under test at a predetermined pressure only or at a predetermined pressure, and the flow rate of the test fluid through the tuyere 30 and the pressure drop or back pressure over the tuyere 30 or at least over the nozzle 34 of the tuyere 30 are determined corresponding to the sensor 35 of the tuyere 30 under test. In this way, it is possible to carry out a condition test of the tuyeres 30 while continuing to inject sufficient oxidant for iron melting from the oxidant ring 31 into the shaft furnace 10 through the other oxidant tuyeres 30. At the end of the condition test of the tuyere 30, the on-off valve 52 corresponding to said tuyere 30 is closed, and the control unit 40 can reconnect said tuyere 30 to the oxidizer ring 31 at a suitable moment (for example immediately, or in the case of pulsed injection of oxidizer as described above, at the start of the next active phase thereof) by opening the valve 32 corresponding to said tuyere.

Fig. 3 illustrates one of the ways in which the present invention can inform the furnace operator of the status of different injectors, such as the oxidant injector or tuyere 30 of the embodiment illustrated in fig. 1 and 2.

Fig. 3 shows a touch screen with a schematic representation of a cross section of the shaft furnace 10 at the level of the oxidant tuyeres 30. Oxidant ring 31 and valve 32 are shown equally. Information indicative of the state or operating condition of the different elements shown in the figure may be obtained by "clicking" on the relevant element.

Three examples of such a fireworker feedback are shown in fig. 3.

The predetermined maximum operating time has been stored in the control unit 40. For each oxidant injector 30, the installation date of the injector 30 has been stored in the control unit 40, and the control unit 40 calculates the expected date of replacement of the tuyere 30 based on the longest operation time from the installation date.

When a condition test has been performed on a given oxidant tuyere, the value determined by the sensor 35 is supplied to the control unit 40, where it is compared with a predetermined safety range and within a predetermined warning range within said safety range for the given parameters and tuyere.

When the determined parameter is within the safety range and outside the warning range, which is the case for tuyere nr.3, the screen displays that the tuyere is safe and indicates the expected replacement date of the tuyere based on the maximum operation time.

When the determined parameter is within the warning range (as is the case for tuyere nr.5), the screen indicates that the tuyere is safe but its function is affected, while again indicating the expected replacement date of the tuyere based on the maximum running time.

Finally, when the determined parameter is outside the safe range (as is the case with tuyere nr.4), the screen indicates that the tuyere is damaged and needs to be replaced as soon as possible.

A color code such as green-orange-red may also be advantageously used to indicate that the status of the individual tuyere 30 is safe, safety-affected and damaged, respectively.

Claims

1. A method for injecting a process fluid into a vertical shaft furnace (10) for performing a combustion process, wherein,

the shaft furnace (10) having n injectors (30) which are distributed substantially uniformly around the circumference of the shaft furnace (10), n ≧ 3, and a fluid distributor (31) which is in fluid connection with a source of the process fluid to be injected on the one hand and with the n injectors (30) on the other hand,

the shaft furnace (10) is part of an apparatus comprising a control unit (40) programmed to: (a) controlling the total amount of process fluid injected into the shaft furnace (10) through n injectors (30) by a first valve unit (32) between the source of process fluid to the fluid distributor (31); and (b) controlling the flow of process fluid from the fluid distributor (31) to each of the n injectors (30) by n individual valve units (33) between the fluid distributor (31) and the n injectors (30),

The method is characterized in that:

-the control unit (40) is also programmed to individually start and perform a condition test for each of the n injectors (30) while the combustion process is being carried out in the shaft furnace (10), during which:

-supplying a test fluid at a predetermined pressure or at a predetermined flow rate to an injector (30) testing the condition,

measuring a flow rate of fluid through the injector (30) when the test fluid is supplied to the injector (30) at a predetermined pressure, and measuring a pressure drop over the injector (30) or over at least one nozzle portion of the injector (30) when the test fluid is supplied to the injector (30) at a predetermined flow rate;

when the test fluid is supplied to the injector (30) at a predetermined pressure and the flow rate of the fluid passing through the injector (30) is measured, the control unit (40) verifies whether the measured flow rate falls within a predetermined safe flow rate range for the predetermined pressure, and when the test fluid is supplied to the injector at the predetermined flow rate and the pressure drop is measured, the control unit (40) verifies whether the measured pressure drop falls within a predetermined safe pressure drop range for the predetermined flow rate,

-when the measured flow rate does not fall within the predetermined safe flow rate range or when the measured pressure drop does not fall within the predetermined safe pressure drop range, the control unit (40) issues an output signal indicating that the injector (30) that has been tested for status must be replaced,

the predetermined safe flow rate range is the range of flow rates observed when the test fluid is supplied to a new, unused injector of the same type at a predetermined pressure, and the predetermined safe pressure drop range is the range of pressure drops observed when the test fluid is supplied to such a new, unused injector at a predetermined flow rate.

2. The method of claim 1, wherein the control unit (40) is programmed to repeat the status check for each of the n injectors (30) at predetermined intervals.

3. The method according to claim 1 or 2, wherein the fluid distributor (31) is a fluid distribution ring surrounding the shaft furnace (10).

4. Method according to claim 1 or 2, wherein the process fluid is used as a test fluid, and wherein, during the supply of the test fluid to the injector (30) to be tested for condition, the control unit (40) closes n-1 individual valve units (33) between the fluid distributor (31) and n-1 other injectors (30), so that all process fluid supplied to the fluid distributor (31) flows at a predetermined pressure or at a predetermined flow rate to the injector (30) to be tested for condition, and no process fluid flows from the fluid distributor (31) to n-1 other injectors (30).

5. The method according to claim 4, wherein the control unit (40) is programmed to control the flow of the process fluid from the fluid distributor (31) to each of the n injectors (30) such that said injectors (30) inject the process fluid into the shaft furnace (10) continuously or in a pulsed manner when the control unit (40) is not performing a condition test.

6. Method according to claim 1, wherein a fluid other than the process fluid is used as test fluid, and wherein, during the supply of test fluid to the injector (30) under test, the control unit (40) performs the following operations: (a) closing a single valve unit (33) connecting an injector (30) to be tested for a condition to the fluid distributor (31) such that no process fluid flows from the fluid distributor (31) to said injector (30), and (b) opening a test fluid valve (52) between a test fluid source (50) and said injector (30) such that the test fluid is supplied to said injector (30) at a predetermined pressure or at a predetermined flow rate.

7. The method according to claim 6, wherein the test fluid does not react with other chemical constituents present in the shaft furnace (10).

8. The method according to claim 6 or 7, wherein the fluid distributor (31) is a test fluid distribution ring surrounding the shaft furnace (10).

9. The method according to claim 6 or 7, wherein the control unit (40) is programmed to control the flow of process fluid from the fluid distributor (31) to n injectors (30) such that said injectors (30) inject process fluid into the shaft furnace (10) continuously or in a pulsed manner when the injectors (30) are not being subjected to a condition test.

10. The method of claim 1 or 2,

wherein the test fluid is supplied to the injector (30) at a predetermined pressure, and the predetermined safe flow rate range consists of a predetermined standard flow rate range and a predetermined warning flow rate range on both sides of the standard flow rate range, and wherein the control unit (40) verifies whether the measured flow rate falls outside the standard flow rate range but within the warning flow rate range, or

Wherein the test fluid is supplied to the injector (30) at a predetermined flow rate, and the predetermined safety pressure drop range consists of a predetermined standard pressure drop range and predetermined warning pressure drop ranges on both sides of the standard pressure drop range, and wherein the control unit (40) verifies whether the measured pressure drop falls outside the standard pressure drop range but within the warning pressure drop range,

And wherein:

-when the measured flow rate falls within the warning flow rate range or when the measured pressure drop falls within the warning pressure drop range, the control unit (40) issues an output signal indicating that the injector (30) that has been tested for status is no longer operating in its standard operating condition.

11. Method according to claim 1 or 2, wherein the control unit (40) further tracks the running time of the n injectors (30), and wherein the control unit (40) generates an output signal indicating that one of the n injectors (30) has reached its maximum running time when the running time of said injector reaches a predetermined maximum running time.

12. Method according to claim 1 or 2, wherein the control unit (40) starts and performs the status test for each of the n injectors (30) in turn, without interruption between two consecutive status tests of different injectors (30).

13. Method according to claim 1 or 2, wherein the control unit (40) initiates and performs a status test for each of the n injectors (30), with an interval without a status test between two consecutive status tests of different injectors (30).

14. The method according to claim 1 or 2, wherein the shaft furnace (10) is a cupola furnace.

15. A process according to claim 1 or 2, wherein the process fluid is a combustion oxidant having an oxygen content above 21% vol and at most 100% vol.