Method and apparatus for heating a furnace

Abstract

The invention relates to a method for heating a furnace (100, 600) having a longitudinal direction (D) and a cross section (C) perpendicular to the longitudinal direction (D), the furnace (100, 600) being arranged with at least one heating zone (120, 130, 140) heated using combustion of a fuel with an oxidant, and the furnace (100, 600) further being arranged with a dark zone (110) downstream of said heating zone (120, 130, 140), no fuel being directly supplied to the dark zone (110). The invention is characterized in that the fuel and oxidant supplied to the heating zone (120, 130, 140) are substoichiometric, 10-40% of the total oxidant for achieving stoichiometric combustion or close to stoichiometric combustion being directly supplied to the dark zone (110), the flue gas temperature in and / or downstream of the dark zone (110) being measured, and the share of the total oxidant supplied to the dark zone (110) being controlled so as not to exceed a predetermined maximum measured temperature. The invention also relates to a method for retrofitting an existing furnace, and also to a furnace.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for heating a furnace. Furthermore, the present invention relates to a method for retrofitting an existing furnace to enable more flexible heating operation. The present invention also relates to such a furnace. BACKGROUND

[0002] Industrial heating furnaces for heating metal material, such as billets, are typically heated by a fuel which is combusted with an oxidant. Typically, the major part of this combustion takes place in a main heating zone. The combustion products can then flow counter-current to the heated metal material, downstream of the furnace, to an exit for flue gas at the metal material charging port. The downstream zone through which the combustion products flow is often referred to as the "dark zone".

[0003] Hence, the metal material being conveyed through the furnace is preheated in the dark zone in the upstream direction of the furnace on its way from the charging port to the main heating zone by hot combustion products.

[0004] For thick material, in order to heat the central part of the material as appropriately as possible as quickly as possible, it is often desirable to heat the material as early as possible in the furnace. For example, the center of a slab needs to be heated close to equilibrium before it can be removed from the furnace for rolling or forging.

[0005] This problem is often solved by adding extra burners in the dark zone in order to increase the heating power there. This increases the flue gas temperature which can cause problems for any upstream heat recovery or recuperation equipment used to extract heat energy from the flue gas.

[0006] In order not to overheat the flue gas, it has been proposed to use so-called oxy-fuel burners (i.e. burners operated using a high-oxygen oxidant) in the dark zone. However, this is typically a complex and expensive solution.

[0007] Hence, it would be desirable to be able to heat the metal material in the dark zone more efficiently without such a solution being overly complex or expensive.

[0008] Furthermore, it would be desirable for such a solution to provide more flexibility in terms of heating power in the furnace. The latter is especially true for existing heating furnaces, otherwise upgrading in order to provide more flexible heating power is very expensive. SUMMARY

[0009] The present invention solves the above-mentioned problems.

[0010] Therefore, the present invention relates to a method for heating a furnace having a longitudinal direction and a cross section perpendicular to the longitudinal direction, the furnace being arranged with at least one heating zone heated by combustion of fuel and oxidant, and the furnace further being arranged with a dark zone downstream of the heating zone, to which no fuel is directly supplied, the method being characterized in that the fuel and oxidant supplied to the heating zone are substoichiometric, 10% to 40% of the total oxidant for achieving stoichiometric combustion or near-stoichiometric combustion is directly supplied to the dark zone, the flue gas temperature in and / or downstream of the dark zone is measured, and the share of the total oxidant supplied to the dark zone is controlled so as not to exceed a predetermined maximum measurement temperature.

[0011] Furthermore, the present invention relates to a method for modifying an existing furnace for operation according to the technical solution of the invention, the existing furnace having a longitudinal direction and a cross-section perpendicular to the longitudinal direction, the existing furnace being arranged with at least one heating zone heated by combustion of fuel and oxidant, and the existing furnace further being arranged with a dark zone downstream of the heating zone, to which no fuel is directly supplied, the method being characterized in that the method includes providing a separate oxidant nozzle arranged to directly supply oxidant to the dark zone; connecting the separate oxidant nozzle to an oxidant source; modifying the furnace by directly supplying oxidant to the dark zone to supply the fuel and oxidant to the heating zone in a substoichiometric manner to provide 10% to 40% of the total oxidant for achieving stoichiometric or near-stoichiometric combustion; providing a flue gas temperature sensor arranged to measure the flue gas temperature in and / or downstream of the dark zone; and modifying the furnace to control the share of the total oxidant supplied to the dark zone so as not to exceed a predetermined maximum measurement temperature.

[0012] Furthermore, the present invention relates to a heating furnace having a longitudinal direction and a transverse plane perpendicular to the longitudinal direction, the furnace being arranged with at least one heating zone heated by the combustion of fuel and oxidant, and the furnace further being arranged with a dark zone downstream of the heating zone, to which no fuel is arranged to be directly supplied, the furnace being characterized in that the furnace is arranged to supply fuel and oxidant to the heating zone in a substoichiometric manner, the furnace is arranged to directly supply 10% to 40% of the total oxidant used to achieve stoichiometric or near-stoichiometric combustion to the dark zone, the furnace including a flue gas temperature sensor arranged to measure the flue gas temperature in and / or downstream of the dark zone, and the furnace being arranged to control the proportion of the total oxidant supplied to the dark zone so as not to exceed a predetermined maximum measurement temperature. Attached Figure Description

[0013] In the following, the invention will be described in detail with reference to exemplary embodiments and accompanying drawings, wherein:

[0014] Figure 1 This is a simplified side view of the furnace according to the present invention;

[0015] Figure 2 yes Figure 1 A simplified top view of the furnace shown;

[0016] Figure 3 This is a simplified detailed drawing of the oxidizer spray gun according to the present invention;

[0017] Figure 4 This illustrates the use of the present invention for... Figure 1 A flowchart illustrating the method for heating a furnace of the type shown; and

[0018] Figure 5 This illustrates the invention for modifying or altering an existing furnace to suit [the purpose of] [the specific application of the invention]. Figure 4 The flowchart shown is a flowchart of the operation method.

[0019] Figure 6 This is a simplified view of the side-fired furnace according to the present invention. Detailed Implementation

[0020] therefore, Figure 1 An industrial furnace 100 is shown, having a longitudinal direction D and a cross-section C perpendicular to the longitudinal direction D. The furnace 100 includes at least one, but possibly several, heating zones 120, 130, 140, through which metallic material 104 is preferably conveyed along the longitudinal direction D, whereby the material 104 is heated en route from inlet door 101 to outlet door 102. The furnace 100 also includes a dark zone 110 located near the inlet door 101, to which no fuel is directly supplied.

[0021] Furnace 100 may be a continuous reheating furnace, and material 104 may be a metallic material, such as steel. Preferably, the thickness of the metallic material 104 is at least 10 cm, such as at least 20 cm. Generally, material 104 is preferably heated to a temperature above about 1000°C.

[0022] Each region 110, 120, 130, 140 may typically include an upper region and a lower region, including the dark region 110. 121 indicates a baffle arranged to separate the dark region 110 from the heated region 120.

[0023] Furnace 100, and in particular one or more heating zones 120, 130, 140 that are not the dark zone 110, are heated by the combustion of fuel and oxidant, both of which are directly supplied to the heating zones 120, 130, 140 in question.

[0024] The fuel can be gaseous, liquid, or solid. The oxidant supplied to the heating zones 120, 130, and 140 in question is preferably an oxidant containing at least 85% oxygen, and more preferably industrial pure oxygen, but in some embodiments it can also be air or any other oxidant. For example, one or more of the burners 122, 123, 132, and 133 arranged in the heating zones 120 and 130 in question can be adapted for high-oxygen oxidant supplementation via a corresponding separate main oxidant nozzle 124 installed at a distance from the respective burner 122 in question (see...). Figure 2 The high-oxygen oxidant is supplied from the control device 160 of the furnace 100 via pipeline 1. The high-oxygen oxidant, which forms a jet 124a in the downstream direction of the longitudinal direction D, can be the only oxidant used in the non-dark zone heating zones 120, 130; however, it can also be used in addition to the oxidant supplied via the burner 122 itself. Generally, heating zones 120, 130, 140 can be used with any combination of oxy-fuel and air burners, even though the invention is particularly advantageous for the furnace 100 heated by at least one oxy-fuel burner.

[0025] Each of the burners 122 supplemented in this way using the corresponding main oxidizer spray gun 124 can be an existing burner 122 that has been modified by the spray gun 124, such as an air burner, in which some or all of the previously used oxidizer (such as air) is replaced by the high-oxygen oxidizer during the modification.

[0026] According to Figure 1 and Figure 2 In this arrangement, burners 122 and 132 burn substantially in the longitudinal direction D, meaning that oxidant and fuel are supplied to heating zones 120 and 130 substantially in the longitudinal direction D. The fuel, oxidant, and combustion products are substantially parallel to the metal material to be heated. Such a furnace is also called a front-combustion furnace or a rear-combustion furnace.

[0027] The invention can also be applied to so-called side-fired furnaces, wherein burners for heating the heating zone are arranged in the side wall of the furnace. The burners burn in a substantially horizontal direction perpendicular to the longitudinal direction D. According to the invention, the oxidizer lance is preferably arranged in the side wall of the dark zone of the furnace.

[0028] Figure 6 A side-combustion continuous reheating furnace 600 is shown, having a longitudinal direction D and a cross-section C perpendicular to the longitudinal direction D. Furnace 600 is similar to... Figure 1 and Figure 2The furnace 100 is shown. The furnace 600 includes several heating zones 620, 630, and 640 through which the metal material 104 is conveyed and heated. The furnace 600 also has a dark zone 610 arranged near the entrance door 601, through which no fuel is directly supplied.

[0029] Furnace 600, and in particular one or more heating zones 620, 630, 640 that are not the dark zone 610, are heated by the combustion of fuel and oxidant, both of which are directly supplied to the heating zones 620, 630, 640 in question.

[0030] The fuel can be a gaseous, liquid, or solid fuel. The oxidant supplied to the heating zones 620, 630, and 640 is preferably an oxidant containing at least 85% oxygen, and more preferably industrial pure oxygen, but in some embodiments it can also be air or any other oxidant.

[0031] In one embodiment, one or more of the burners 622, 623, 632, 633 arranged in heating zones 620, 630 are suitable for supplying high-oxygen oxidizer, which is supplied from a control device 660 via a corresponding separate main oxidizer nozzle 624 installed at a distance from the respective burner 622 in question. The injected high-oxygen oxidizer may be the only oxidizer used in the non-dark zone heating zones 620, 630; however, it may also be used in addition to the oxidizer supplied via the burner 622 itself. Generally, heating zones 620, 630, 640 can be used with any combination of oxygen-fueled and air-fired burners.

[0032] Each of the burners 622 supplemented in this way using the corresponding primary oxidizer spray gun 624 can itself be an existing burner 622 that has been modified by the spray gun 624, such as an air burner, during which some or all of the previously used oxidizer (such as air) is replaced by the high-oxygen oxidizer.

[0033] According to the preferred embodiment, the heating zones 620, 630, and 640 of the furnace 600 are heated by burners 622, 623, 632, and 633, wherein all burners 622, 623, 632, and 633 that heat the heating zones 620, 630, and 640 are located in the side wall of the furnace 600.

[0034] In another preferred embodiment, burners 622, 623, 632, 633 located in the sidewalls of heating zones 620, 630, 640 are supplemented with oxidizer spray guns arranged close to burners 622, 623, 632, 633 for supplying a portion of the oxidizer to heating zones 620, 630, 640.

[0035] Preferably, this applies to the front or rear combustion furnace 100 and the side combustion furnace 600.

[0036] The following advantageous implementation schemes are applicable to front combustion furnaces, rear combustion furnaces, and side combustion furnaces.

[0037] The temperature in the heating zones 120, 130, 140, 620, 630, and 640 of furnaces 100 and 600 can preferably be at least 1000°C. The flue gas flows counter-currently to the material 104 in the conveying direction of furnaces 100 and 600.

[0038] According to the invention, the fuel and oxidant supplied to the non-dark zone heating zones 120, 130, 140, 620, 630, and 640 are controlled to a substoichiometry, meaning that there is a fuel surplus relative to the available oxidant in the heating zones 120, 130, 140, 620, 630, and 640 as a whole. Specifically, the flue gas arriving at the downstream portion of the heating zones 120 and 620, which are located just upstream of the dark zones 110 and 610, contains an excess of combustible fuel, resulting in the flue gas flowing into the dark zones 110 and 610 carrying this fuel surplus.

[0039] Further according to the invention, 10% to 40%, preferably 25% to 40%, of the total oxidant used to achieve stoichiometric or near-stoichiometric combustion is then directly supplied to dark zones 110, 610, such as via spray guns 151, 152, 153, 154. It should be noted that these relative amounts relate to the oxygen content in the respective oxidant. Figure 1 and Figure 2 as well as Figure 6 In the exemplary embodiment shown, there are two pairs of dark zone 110, 610 oxidizer spray guns such as 151, 152, 153, 154, one pair on each lateral side of furnace 100, 600 and pointing towards dark zone 110, 610 to deliver oxidizer directly to dark zone 110, 610, such as horizontally from a position arranged in its sidewall.

[0040] In a preferred embodiment, the redistribution of the oxidant from heating zones 120, 130, 140, 620, 630, 640 to dark zones 110, 610 results in the gas volume flow rate (number of molecules) entering dark zones 110, 610 remaining the same or substantially the same, while the gas mass flow rate is reduced due to the redistributed oxidant.

[0041] In an alternative embodiment, the temperatures in the heating zones 120, 130, 140, 620, 630, and 640 are maintained by increasing the combustion power in the heating zones 120, 130, 140, 620, 630, and 640 compared to before the redistribution of the oxidant supply. For example, this could include increasing the amount of fuel supplied per unit time. It has been demonstrated that, at constant power, the net effect of redistributing the oxidant according to the invention is generally positive, even if the temperatures in the heating zones 120, 130, 140, 620, 630, and 640 remain unchanged as a result.

[0042] Regardless of the method, compared with conventional operation in dark zones 110 and 610 without active heating, the temperature of the flue gas leaving through flue 103 did not increase significantly, or at least did not increase by more than 10%.

[0043] The oxidant is supplied from the control device 160 via spray guns 151, 152, 153, and 154 via corresponding lines 161, 162, 163, and 164.

[0044] Furthermore, according to the invention, the flue gas temperature sensor 168b is arranged to measure the flue gas temperature in and / or downstream of dark zones 110, 610 (such as in flue 103). Furthermore, the proportion of total oxidant supplied to dark zones 110, 610 is controlled by control device 160 to ensure that it does not exceed a predetermined maximum measurement temperature. Preferably, the proportion of total oxidant supplied to dark zones 110, 610 via the spray guns 151, 152, 153, 154 is thus adjusted to achieve the predetermined measured flue gas temperature. Therefore, if the measured temperature of the flue gas is too high, less (or more, depending on the configuration) oxidant is supplied to dark zones 110, 610, and vice versa. The predetermined maximum temperature can be, for example, between 800°C and 1000°C. The predetermined temperature can be between 600°C and 900°C, and can be fixed or variable during operation.

[0045] At the same time, the total amount of oxidant supplied to the non-dark heating zones 120, 130, 140, 620, 630, 640 and to the dark zones 110, 610 can be adjusted to achieve the predetermined heating power of the furnaces 100 and 600 as a whole.

[0046] Therefore, in furnaces that operate with conventional air or oxygen fuel, a portion of the oxygen flow typically injected near the heating zones 120, 130, 140, 620, 630, 640 is redirected to lances 151, 152, 153, 154 located downstream of the heating zones 120, 130, 140, 620, 630, 640, in a portion of the dark zones 110, 610 where the temperature is higher than the auto-ignition temperature.

[0047] In this way, the conventional combustion heating zones 120, 130, 140, 620, 630, and 640 are changed to combustion under substoichiometric conditions, and the unburned fuel portion will move with the exhaust gas to the dark zones 110 and 610, where it will meet the redirected portion of the oxidant flow for complete combustion.

[0048] As a result, some of the heat typically generated in the conventional heating zones 120, 130, 140, 620, 630, and 640 is instead released in the dark zones 110 and 610, thereby increasing yield by heating the material 104 earlier during its transition through furnaces 100 and 600. Compared to the dark zone 110 and 610 booster burners that directly release both fuel and oxidizer into the dark zones 110 and 610, this invention is a less complex and more energy-efficient solution.

[0049] Furthermore, in the solution according to the invention, the control device 160 can be arranged to adjust downwards or preferably completely shut off the dark zones 110, 610, and the spray guns 151, 152, 153, 154, thus providing a larger possible power spectrum for the furnaces 100, 600. Specifically, at low production rates, the spray guns 151, 152, 153, 154 can be shut off during low-power operation to maximize energy efficiency in the furnaces 100, 600.

[0050] Therefore, the present invention provides, in some way, staged combustion of fuel supplied in heating zones 120, 130, 140, 620, 630, and 640, which further leads to NO x This reduces the amount of NO formed, and may also reduce the amount of NO formed in the upstream heating zones 120, 130, 140, 620, 630, and 640.

[0051] Another advantage is that firing at higher temperatures and under more prevalent substoichiometric conditions in material 104 also reduces the formation of oxides (scale) on the surface of material 104. In fact, the combustion gases flowing into dark zones 110 and 610 will have reducing properties.

[0052] In some implementations, the oxidant supplied to the heating zones 120, 130, 140, 620, 630, 640 and the dark zones 110, 610 is supplied from the same source 166 via line 167, such as under the control of control device 160.

[0053] In this and other embodiments, preferably, the oxidant supplied to the heating zones 120, 130, 140, 620, 630, 640 contains at least 85% oxygen, and is preferably industrially pure oxygen. Correspondingly, the oxidant supplied to the dark zones 110, 610 is also preferably composed of at least 85% oxygen, and is preferably industrially pure oxygen. Preferably, the oxidant directly supplied to the dark zones 110, 610 can be the same as at least one oxidant directly supplied to the heating zones 120, 130, 140, 620, 630, 640.

[0054] Because of the additional combustion that occurs in dark zones 110 and 610, little or no ballast gas (such as N2) is heated. Therefore, the process can become very energy-efficient compared to the conventional case where there is no combustion in dark zones 110 and 610 or additional fuel is added to dark zones 110 and 610 if a booster burner is used. Most or all of the added heat energy can be used to heat material 104 before the flue gas leaves through flue 103.

[0055] To further improve efficiency and reduce NO x The oxidant delivered via spray guns 151, 152, 153, and 154 can be supplied to dark zones 110 and 610 via at least one oxidant spray gun, preferably via all of the spray guns 151, 152, 153, and 154, at a spray speed of at least Mach 1, more preferably at least Mach 1.2, and even more preferably at least Mach 1.3. This will generate turbulent airflow in dark zones 110 and 610, resulting in a reduction of hot spots and a substantially uniform temperature distribution.

[0056] To further improve energy efficiency, by maximizing the amount of heat energy transferred to material 104 before the flue gas leaves via flue 103, the oxidant supplied in dark zones 110, 610 can be supplied to the upstream portion of dark zones 110, 610, which is 35% of the total longitudinal length D of dark zones 110, 610. In other words, the oxidant is delivered to its respective points, all of which are located at the farthest distance from the downstream heating zones 120, 620, which is no greater than 35% of the total longitudinal length D of dark zones 110, 610.

[0057] like Figure 2 and Figure 6As shown, the oxidant supplied to dark zones 110, 610 can be supplied via at least one spray gun 151, 152, 153, 154 substantially parallel to cross section C. Specifically, in this case, the oxidant supplied to dark zones 110, 610 can be supplied via at least two spray guns (such as 151, 154) on either side of furnace 110, such that two jets 155 of the oxidant intersect or cooperate to cause rotation of the atmosphere in dark zones 110, 610. Such rotation can be oriented in cross section C or in any other plane in dark zones 110, 610, and can be achieved, for example, by the spray guns 151, 152, 153, 154 substantially toward each other but with slight divergence, such that the jet 155 from one of them is slightly directed upwards, while the other is slightly directed downwards or forwards / backwards.

[0058] In this document, the term "intersection" of the two jets 155 of the oxidant means that at least a portion of the two intersecting bodies overlaps during operation of furnaces 100 and 600.

[0059] Spray guns 151, 152, 153, and 154 can all be arranged above the material 104 to be heated, in the upper region of dark zones 110 and 610, and can then be arranged to also provide their respective jets 155 above the material 104 to be heated. However, oxidant can also be provided to the lower region of dark zones 110 and 610 in a corresponding manner.

[0060] Often, material 104 is supported by a mechanism supported by support columns below it. In specific cases where a portion of the sprayed oxidant supplied to dark zones 110, 610 is supplied at a point below the material 104 to be heated, preferably, the oxidant is supplied at a distance between 20% and 50% of the longitudinal distance D between two such support columns downstream of the support columns, preferably about 30%-35%. This has proven to produce good results in terms of efficiency and temperature uniformity. Specifically, this is important by ensuring a uniform temperature distribution of material 104 entering heating zones 120, 130, 140, 620, 630, 640.

[0061] When dark zones 110 and 610 are defined by baffle 121, it is preferable that spray guns 151, 152, 153, and 154 provide oxidant to dark zones 110 and 610 at least slightly below the lowest level of the baffle 121.

[0062] Regarding the construction of the spray guns 151, 152, 153, and 154 themselves, preferably, each of the spray guns 200 is arranged in a corresponding pipe 210 through which cooling air 220, such as from a suitable source 221, is supplied, such that the cooling air 220 surrounds the respective spray gun 200's envelope surface 211. The sprayed oxidant is supplied in an airflow 212, concentric with the cylindrical cooling airflow 220. This in Figure 3 The image is shown in cross-section. Cooling air can be supplied in a volume that is insignificant relative to the amount of oxidant injected in dark zones 110 and 610, so that the cooling air has virtually no impact on combustion efficiency.

[0063] Figure 4 The method according to the invention is shown, using the aforementioned front or rear combustion furnace 100 or side combustion furnace 600, and controlled by the control device 160.

[0064] The method begins in the first step.

[0065] In subsequent steps, fuel and oxidizer are supplied to heating zones 120, 130, 140, 620, 630, and 640 in a substoichiometric manner, while 10% to 40% of the total oxidizer used to achieve stoichiometric or near-stoichiometric combustion is directly supplied to dark zones 110 and 610.

[0066] In subsequent steps, the flue gas temperature in and / or downstream of dark zones 110 and 610 is measured.

[0067] In subsequent steps, the proportion of total oxidant supplied to dark zone 110 is controlled so as not to exceed the predetermined maximum measurement temperature.

[0068] Then, the method repeats the second or third step, or terminates when it is necessary to stop the operation.

[0069] The operation of this method also allows for a wider power spectrum in the same furnaces 100 and 600. Therefore, when higher power is required, oxidant can be supplied to dark zones 110 and 610, while simultaneously increasing the supply of oxidant to heating zones 120, 130, 140, 620, 630, and 640 via the conventional flow. When lower power is required, the oxidant supply to dark zones 110 and 610 can be reduced or completely stopped. When using air and oxygen fuel burners to heat heating zones 120, 130, 140, 620, 630, and 640, the oxygen fuel oxidant supply to heating zones 120, 130, 140, 620, 630, and 640 can be reduced or even completely stopped, with high-oxygen oxidant supplied only via nozzles 151, 152, 153, and 154.

[0070] The temperature of the flue gas in or downstream of dark zones 110, 610 can be regulated by continuous adjustment or by adjusting the oxidant supplied via spray guns 151, 152, 153, 154 via on / off control. This control can be performed as a cascaded regulation, assuming reliable operation of upstream temperature regulation in heating zones 120, 130, 140, 620, 630, 640. Such flue gas temperature regulation can then be performed by control device 160 using sensor 168b and simple valves along lines 161, 162, 163, 164, independently of the temperature regulation of heating zones 120, 130, 140, 620, 630, 640.

[0071] Figure 5 The method according to the invention is also shown, but for modifying existing furnaces 100, 600 to operate according to the method described above. Generally, existing furnaces 100, 600 have the longitudinal direction L and the cross-section C perpendicular to the longitudinal direction L. Furthermore, existing furnaces 100, 600 typically have at least one heating zone 120, 130, 140, 620, 630, 640 of the type described above, which is heated using the combustion of fuel and oxidant. Existing furnaces 100, 600 are further arranged with dark zones 110, 610 of the type described above, downstream of the heating zones 120, 130, 140, 620, 630, 640, where no fuel is directly supplied. The furnace can be a front- or rear-combustion furnace 100 or a side-combustion furnace 600.

[0072] The method begins in the first step.

[0073] In subsequent steps, individual oxidizer spray guns 151, 152, 153, and 154 of the aforementioned type are provided, which are arranged to directly supply oxidizer to dark zones 110 and 610. These individual oxidizer spray guns 151, 152, 153, and 154 can be provided, for example, by drilling holes through the sidewalls of dark zones 110 and 610 and installing such spray guns 151, 152, 153, and 154 in the drilled holes.

[0074] In subsequent steps, individual oxidizer spray guns 151, 152, 153, 154 are connected to the oxidizer source 166, for example, via lines 161, 162, 163, 164.

[0075] In subsequent parallel steps, existing furnaces 100 and 600 are modified, for example by modifying or adding control device 160, to supply fuel and oxidizer in a substoichiometric manner to heating zones 120, 130, 140, 620, 630, and 640 by directly supplying oxidizer to dark zones 110 and 610 via installed spray guns 151, 152, 153, and 154, providing 10% to 40% of the total oxidizer for achieving or near-stoichiometric combustion. This has already been described in detail above.

[0076] In subsequent or parallel steps, a flue gas temperature sensor 168b is provided, which is arranged to measure the flue gas temperature in and / or downstream of dark zones 110, 610.

[0077] In subsequent or parallel steps, existing furnaces 100 and 600 are modified to control the proportion of total oxidant supplied to dark zones 110 and 610 via spray guns 151, 152, 153, and 154 so as not to exceed the predetermined maximum measurement temperature, preferably maintaining the predetermined temperature.

[0078] After this, the method ends, and existing furnaces 100 and 600 are prepared to operate according to the above method.

[0079] Preferably, the modification method does not involve modifying existing furnaces 100 and 600 to supply more fuel than before. In other words, the modification essentially only results in the supply of oxidant being transferred from heating zones 120, 130, 140, 620, 630, and 640 to previously unheated dark zones 110 and 610. Therefore, dark zones 110 and 610 effectively become actively heated zones.

[0080] Preferably, the temperature sensor 168b can be an existing thermal element that already exists in the existing furnaces 100 and 600 before the modification method begins. Furthermore, the control device 160 is preferably a control device already existing in the existing furnaces 100 and 600, modified only according to the above aspects, such as by performing a software update.

[0081] Preferably, the existing furnaces 100 and 600 are oxygen-fueled furnaces; in other words, furnaces 100 and 600 are heated using at least one high-oxygen oxidant as described above.

[0082] Preferred embodiments have been described above. However, it will be apparent to those skilled in the art that many modifications can be made to the disclosed embodiments without departing from the basic spirit of the invention.

[0083] For example, in addition to the one or more spray guns 151, 152, 153, 154, the oxidant can be supplied to the dark zone 110 in other ways. The oxidant spray guns can also be arranged in the ceiling and / or floor of the dark zone.

[0084] Preferably, in a side-burning furnace, oxidizer lances are supplied only in the sidewall of furnace 600, and all oxidizer supplied to dark zone 610 is supplied via oxidizer lances.

[0085] All combinations Figure 4 and Figure 5 The method described also applies to combining Figures 1 to 3 and Figure 6 The system described, and vice versa.

[0086] Therefore, the present invention is not limited to the described embodiments, but can be varied within the scope of the present invention.

Claims

1. A method for heating a side-combustion furnace (100, 600) having a longitudinal direction (D) and a cross section (C) perpendicular to said longitudinal direction (D), said furnace (100, 600) being arranged with at least one heating zone (120, 130, 140, 620, 630, 640) heated by combustion of fuel and oxidant, wherein burners for heating said heating zone are arranged in the sidewall of said furnace, wherein said burners burn in a substantially horizontal direction perpendicular to said longitudinal direction (D), and said furnace (100, 600) further being arranged with a dark zone (110, 610) downstream of said heating zone (120, 130, 140, 620, 630, 640), wherein no fuel is directly supplied to the dark zone (110, 610), wherein the supply The fuel and oxidant supplied to the heating zones (120, 130, 140, 620, 630, 640) are substoichiometric, with 10% to 40% of the total oxidant used to achieve stoichiometric combustion supplied directly to the dark zone (110, 610) via one or more nozzles (151, 152, 153, 154) located in the sidewalls of the furnace (100, 600). All oxidant supplied to the dark zone (110, 610) is supplied via one or more nozzles (151, 152, 153, 154) located in the sidewalls of the furnace (100, 600). The flue gas temperature in and / or downstream of the dark zone (110, 610) is measured, and the supply to the dark zone (110, 610) is controlled. The proportion of the total oxidant in 610) is such that it does not exceed a predetermined maximum measurement temperature, wherein the predetermined maximum measurement temperature is between 800°C and 1000°C, and wherein the farthest distance of all spray guns (151, 152, 153, 154) from the downstream heating zone (120, 620) is not greater than 35% of the total length of the longitudinal direction (D) of the dark zone (110, 610).

2. The method according to claim 1, characterized in that, All fuel and all oxidizer supplied to the heating zone are supplied via one or more burners and / or via one or more oxidizer lances located in one or more sidewalls of the furnace.

3. The method according to claim 2, characterized in that, A portion of the oxidant supplied to the heating zone is supplied via at least one oxidant spray gun.

4. The method according to any one of claims 1-3, characterized in that, The proportion of the total oxidant supplied to the dark zone (110, 610) is adjusted to achieve the predetermined measurement temperature.

5. The method according to any one of claims 1-3, characterized in that, The total amount of oxidant supplied to the heating zones (120, 130, 140, 620, 630, 640) and the dark zones (110, 610) is adjusted to achieve the predetermined heating power.

6. The method according to any one of claims 1-3, characterized in that, The oxidant supplied to the heated zones (120, 130, 140, 620, 630, 640) and the dark zones (110, 610) is supplied from the same source (166).

7. The method according to any one of claims 1-3, characterized in that, The oxidant supplied to the heated zones (120, 130, 140, 620, 630, 640) and / or the dark zones (110, 610) contains at least 85% oxygen.

8. The method according to any one of claims 1-3, characterized in that, The oxidant supplied to the heating zones (120, 130, 140, 620, 630, 640) and / or the dark zones (110, 610) contains industrially pure oxygen.

9. The method according to any one of claims 1-3, characterized in that, The oxidant is supplied to the dark zone (110, 610) via at least one spray gun (151, 152, 153, 154), the at least one spray gun operating at a spray rate of at least Mach 1.

10. The method according to any one of claims 1-3, characterized in that, The oxidant supplied to the dark areas (110, 610) is supplied through at least one spray gun (151, 152, 153, 154) substantially parallel to the cross section (C).

11. The method according to any one of claims 1-3, characterized in that, The oxidant supplied to the dark zone (110, 610) is supplied via at least two spray guns (151, 152, 153, 154) on either side of the furnace (100, 600) such that the two jets (155) of the oxidant intersect.

12. The method according to any one of claims 1-3, characterized in that, Each of the spray guns is arranged in a corresponding tube (210), through which cooling air is supplied around the corresponding spray gun envelope surface (211).

13. A heating furnace (100, 600) having a longitudinal direction (D) and a cross section (C) perpendicular to said longitudinal direction (D), said furnace (100, 600) being arranged with at least one heating zone (120, 130, 140, 620, 630, 640) heated by combustion of fuel and oxidant, wherein burners for heating said heating zone are arranged in the sidewall of said furnace, wherein said burners burn in a substantially horizontal direction perpendicular to said longitudinal direction (D), and said furnace (100, 600) further being arranged with a dark zone (110, 610) downstream of said heating zone (120, 130, 140, 620, 630, 640), wherein no fuel is arranged to be directly supplied to the dark zone (110, 610), wherein, The furnace (100, 600) is arranged to supply fuel and oxidizer to the heating zone in a substoichiometric manner. The furnace (100, 600) is also arranged to supply 10% to 40% of the total oxidizer used to achieve stoichiometric combustion directly to the dark zone (110, 610) via one or more nozzles (151, 152, 153, 154) located in the sidewall of the furnace (100, 600). All oxidizer supplied to the dark zone (110, 610) is supplied via one or more nozzles (151, 152, 153, 154) located in the sidewall of the furnace (100, 600). The furnace (100, 600) includes a flue gas temperature sensor (168b) arranged to measure the flue gas temperature in and / or downstream of the dark zone (110, 610). 600) is arranged to control the share of the total oxidant supplied to the dark zones (110, 610) so as not to exceed a predetermined maximum measurement temperature, wherein the predetermined maximum measurement temperature is between 800°C and 1000°C, wherein the farthest distance of all spray guns (151, 152, 153, 154) from the downstream heating zone (120, 620) is not greater than 35% of the total length of the dark zones (110, 610) in the longitudinal direction (D).

14. The heating furnace according to claim 13, characterized in that, All burners used to heat the heating zone are arranged in the side walls of the furnace.

Images