JP2015232420A - Waste heat boiler for nonferrous metal smelting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste heat boiler for nonferrous metal smelting furnace capable of being used for a long period of time by restricting corrosion of water pipes.SOLUTION: This invention relates to a waste heat boiler comprising a barrel part 20 lined up by castable 21 and water pipes 10 arranged on its inner wall surface 21a in a zig-zag form so as to recover waste heat of discharged gas discharged out of a smelting furnace with sulfide ore being applied as raw material. The water pipes 10 are constituted by at least two adjoining straight pipes 11 and U-shaped bent pipes 12, 13 connecting these straight pipes arranged near at least the discharged gas inlet part of the barrel part 20, and their opposite sides against the inner wall surface 21a are constituted by flat surfaces having no clearance. The flat surfaces of the U-shaped bent pipes 12, 13 can be formed by building-up alloy or titanium oxide including nickel of 40 mass% or more and chromium of 10 mass% or more in iron.

Description

  The present invention relates to a waste heat boiler provided in a nonferrous metal smelting furnace using sulfide ore as a raw material.

  Non-ferrous metal smelting furnaces such as flash furnaces that melt non-ferrous metals as raw materials and separate them into mats and slags are equipped with waste heat boilers that recover the waste heat of high-temperature exhaust gas generated during melting. . This waste heat boiler generally has a structure in which a water pipe is disposed inside a caster-lined trunk. Waste heat recovery is performed by heat exchange between boiler water flowing inside the water pipe and high-temperature exhaust gas flowing outside the water pipe.

  When sulfide ore is used as the non-ferrous metal raw material, auxiliary raw materials such as smoke ash, entanglement regulator (also called flux) and auxiliary fuel are charged together with the sulfide ore into the smelting furnace, and the reaction gas Is blown into the smelting furnace and smelting is performed. Therefore, the exhaust gas sent to the waste heat boiler contains smoke ash, and part of the smoke ash in the exhaust gas sometimes adheres to the outer peripheral surface of the water pipe of the waste heat boiler.

  Thus, when smoke ash adheres to the outer peripheral surface of the water pipe, the heat exchange efficiency is lowered, and the water pipe may be corroded by a corrosive substance contained in the attached smoke ash. Therefore, for example, smoke ash adhering to the water pipe by blowing air is removed, and the removed smoke ash is discharged by a transport facility such as a chain conveyor provided below the body portion. Although such smoke ash removal means can remove most of the smoke ash adhering to the water pipe, significant corrosion still occurs in the bent pipe part of the water pipe, especially in the vicinity of the exhaust gas inlet part of the waste heat boiler. was there.

  Although it is not a waste heat boiler for non-ferrous metal smelting furnaces, Patent Document 1 discloses a plurality of superheater straight pipes extending in the vertical direction and U-shaped bends that connect adjacent superheater straight pipes among them. In a superheater for a black liquor recovery boiler consisting of a pipe and a superheater header, a technique has been proposed in which a downwardly protruding projection is provided by welding over the lower part of the lower U-shaped bent pipe. . It is described that the molten smoke ash is less likely to stagnate, and thus the degree of corrosion of the superheater straight pipe can be reduced.

Japanese Patent Laid-Open No. 5-196207

  In recent years, sulfide ores used as raw materials for non-ferrous metal smelting furnaces tend to contain higher concentrations of highly corrosive elements such as halogens. Strong elements were sometimes contained in smoke ash in large quantities. As a result, particularly severe corrosion occurred in the above-mentioned U-shaped bent pipe in which smoke ash is likely to remain, and the number of cases where replacement was required for every regular repair increased.

  Although it is considered that the effect of corrosion prevention is obtained to some extent by performing the weld buildup shown in Patent Document 1, the boundary portion between the weld buildup portion and the non-buildup portion and the gap existing between adjacent water pipes Then, it is difficult to remove the attached smoke ash, and corrosion is expected to proceed from that part. Moreover, since the smoke ash contained in the exhaust gas heat-recovered by the waste heat boiler for non-ferrous metal smelting furnace is not melted and is solid, even if the technique of Patent Document 1 is applied as it is, the effect is sufficiently exerted. I can't seem to.

  The present invention has been made in view of the above-described conventional problems, and in a non-ferrous metal smelting furnace, the concentration of highly corrosive elements such as halogen contained in the raw material is increased and discharged from the smelting furnace. Even when exhaust gas contains a lot of highly corrosive elements, waste heat for non-ferrous smelting furnaces can be used for a long period of time by suppressing the corrosion of the water pipe of the waste heat boiler that recovers waste heat of the exhaust gas The problem is to provide a boiler.

  In order to solve the above-mentioned problems, the waste heat boiler for a non-ferrous metal smelting furnace of the present invention comprises a body part and a water pipe provided in a meandering manner on the inner wall surface thereof, from a smelting furnace using sulfide ore as a raw material. A waste heat boiler for recovering waste heat of exhaust gas discharged, wherein the water pipe includes at least two adjacent straight pipes disposed in the vicinity of the exhaust gas inlet of the body part and a U-shaped bent pipe connecting them. In the present invention, the side opposite to the side facing the inner wall surface is formed of a flat surface without a gap.

  According to the present invention, in a non-ferrous metal smelting furnace, the concentration of highly corrosive elements such as halogen contained in the raw material is increased, and a large amount of the corrosive elements are contained in the exhaust gas discharged from the smelting furnace. Even if it is contained, it becomes possible to use for a long period of time by suppressing the corrosion of the water pipe of the waste heat boiler that recovers the waste heat of the exhaust gas.

It is a perspective view of the waste heat boiler for nonferrous metal smelting furnaces of one example of the present invention. It is a front view of the water pipe which the waste heat boiler for nonferrous metal smelting furnaces of one example of the present invention has. It is sectional drawing which showed the III-III arrow view of the water pipe | tube of FIG. 2 with a part of trunk | drum which was lined.

  Hereinafter, a specific example of a waste heat boiler for a non-ferrous metal smelting furnace of the present invention will be described by taking as an example the case of using a sulfide ore such as chalcopyrite as a raw material of a flash smelting furnace as a smelting furnace. In a dry smelting flash furnace using sulfide ore as a raw material, the sulfide ore is melted by its own oxidation reaction heat, and is divided into a mat having a copper grade of about 60 to 65% and a slag made of iron oxide or silicic acid. . The waste heat boiler is a facility that recovers the waste heat of the high-temperature exhaust gas discharged from the flash furnace during melting and generates steam, and the exhaust gas after the waste heat is recovered is used as sulfuric acid source gas to produce sulfuric acid. Sent to.

  The waste heat boiler is composed of, for example, a radiant section 1 and a convection section 2 as shown in FIG. 1, and the exhaust gas discharged from the flash furnace is the side surface of the body section of the radiant section 1 as indicated by white arrows. After being exhausted from the exhaust gas inlet portion 1a provided in the radiant portion 1 and recovered as waste heat inside the radiation portion 1 and the convection portion 2, the exhaust gas is discharged from the exhaust gas outlet portion 2a provided on the side surface of the body portion of the convection portion 2. The body parts of the radiation part 1 and the convection part 2 are each composed of a substantially rectangular parallelepiped upper part and a lower part of a tapered structure in which the distance between the opposing wall surfaces becomes narrower downward. After being collected below the taper structure, it is discharged from the body through a smoke ash discharge device such as a chain conveyor (not shown).

  A water pipe through which boiler water that performs heat exchange with exhaust gas flows is provided inside the body portion. The water pipe is arranged so that the waste heat of the exhaust gas can be efficiently recovered. Specifically, in the radiating section 1, the water pipe is stretched in a meandering manner over almost the entire inner wall surface of the trunk section. On the other hand, in the convection section 2, water pipes are provided on the inner wall surface of the trunk section and the space portion of the trunk section. These water pipes are integrated with a plurality of straight pipes arranged in parallel to each other on one plane and a U-shaped bent pipe connecting the ends of adjacent straight pipes among them. It may be installed in the form of a panel.

  In the waste heat boiler according to a specific example of the present invention, at least two straight pipes disposed in the vicinity of at least the exhaust gas inlet part 1a among the water pipes provided in a meandering manner on the inner wall surface of the body part. In the U-shaped bent pipe connecting them, the side opposite to the side facing the inner wall surface is formed of a flat surface with no gap. Specifically, for example, as shown in FIG. 2, the water pipe 10 provided on the upper wall surface of the exhaust gas inlet portion 1 a includes eight straight pipes 11 extending in the vertical direction, and the straight pipes 11. The upper U-shaped bent tube 12 that connects the upper ends of adjacent ones and the lower U-shaped bent tube 13 that connects the lower ends of adjacent ones are integrated in a panel shape. The “near” means 3 m from the end of the exhaust gas inlet 1a side of the inlet side wall where the exhaust gas inlet 1a is provided and the side wall provided to connect to the inlet side wall. The range up to.

  As shown in FIG. 3, the water pipe 10 integrated in a panel shape in this way is so that the surface of the panel is parallel to the inner wall surface 21 a on the inner wall surface 21 a of the castable 21 lining the main body body portion 20. Is provided. That is, the body portion 20, the castable 21, and the panel-shaped water pipe 10 are attached in this order from the outside of the waste heat boiler using fixing means such as anchor bolts. And this integrated water pipe 10 is comprised by the flat surface 10a with no gap on the opposite side to the side which opposes the inner wall surface 21a of the castable 21 over the whole. Here, “no gap” means that the flat surface 10a preferably has no gap, but when a plurality of straight pipes and bent pipes having a flat surface are assembled and integrated into a panel shape. In consideration of workability, processing accuracy, etc., it means that a gap of up to about 3 mm that hardly adversely affects the effect of the present invention is regarded as having no gap.

  With the above configuration, the water pipe 10 provided in a meandering manner on the inner wall surface 21a of the castable 21 lining the body portion 20 directly contacts the exhaust gas contained in the body portion 20 of the waste heat boiler. It becomes possible to do. In addition, since the portion of the water pipe 10 that is in direct contact with the exhaust gas is composed of the flat surface 10a having no gap over the entire water pipe 10 as described above, it is difficult for smoke ash to accumulate in the depression of the bent pipe. And prevent significant local corrosion. The gap between the inner wall surface 21a and the water pipe 10 may be filled with, for example, castable.

  By the way, in the conventional flash furnace waste heat boiler, the local thinning of the water pipe in the vicinity of the exhaust gas inlet portion 1a tends to become more and more intense in recent years, and a nickel-base alloy is welded on the bent pipe portion. Even if it corresponds, local thinning may occur. As a result of investigating the cause of such significant thinning in recent years, it has been found that corrosion and wear have a synergistic effect to cause significant thinning.

  Specifically, it has been found that the cause of significant corrosion in recent years is due to an increasing tendency of alkali elements such as Na and K in addition to halogen in the raw material of the smelting furnace. That is, if the raw materials used in the non-ferrous metal smelting furnace contain more highly corrosive elements such as halogens and alkalis, these corrosive elements become smoke ash and are contained in a large amount in the exhaust gas. Therefore, severe corrosion occurs from the smoke ash adhering to the water pipe.

  On the other hand, the cause of significant wear in recent years is that the amount of exhaust gas generated and the concentration of smoke ash contained in this increase with the recent increase in the amount of sulfide ore processing in smelting furnaces I understood. That is, due to the increase in the amount of exhaust gas, the flow rate of the exhaust gas becomes extremely fast in the vicinity of the exhaust gas inlet portion 1a where the exhaust gas temperature is the highest, and as a result, the bent portion of the bent pipe of the water pipe near the exhaust gas inlet portion 1a or the adjacent bent pipe In the gap portion of the exhaust gas, a drift such as vortex is likely to occur in the exhaust gas, and the vicinity of the exhaust gas inlet portion 1a is located on the inlet side of the body portion of the radiating portion 1 where the solid gas separation of the exhaust gas containing smoke ash is performed. Since the exhaust gas in the vicinity of the part 1a contains a large amount of smoke ash as it is, significant wear occurs.

  Even under such conditions in which significant corrosion and wear occur in recent years, the side opposite to the side facing the inner wall surface of the body portion 20 over the entire water pipe 10 is flat with no gap as described above. By comprising by the surface 10a, since smoke ash becomes difficult to adhere to a U-shaped bent pipe, it can prevent that corrosion advances from there. Furthermore, since it becomes possible to flow the exhaust gas smoothly along the flat surface 10a, the exhaust gas is less likely to cause a local drift such as a vortex in a hollow portion of a bent tube or a gap portion of an adjacent bent tube, Thus, significant wear due to local drift can be prevented.

  The flat surface 10a described above can be produced, for example, by the following method. That is, in the straight pipe portion, a so-called omega tube used in a boiler water pipe is used, and the flat surface side of the omega tube is set to be opposite to the side facing the inner wall surface of the body portion 20 described above. do it. The U-shaped bent pipe is welded to the outer peripheral surface of a general bent tube for a boiler water pipe having a circular cross section so that it is the same plane as the flat surface of the omega tube used for the straight pipe. Just add it. At that time, the surface of the flat surface is preferably equal to the grinder finish in the machine finish.

  The same material as the above-described general boiler water pipe piping may be used as the material to be flattened, or an alloy containing, for example, 40% or more nickel such as Inconel and 10% or more chromium may be used. By using such an alloy, extremely high corrosion resistance can be obtained. Alternatively, titanium oxide (titania) may be used instead of the build-up of this alloy. In this case, extremely high wear resistance can be obtained. In the case of titanium oxide, it can be built up by thermal spraying, for example.

  Alternatively, when the flat surface 10a is formed, first, the above-described nickel is overlaid by welding with an alloy containing 40% or more of nickel and 10% or more of chromium, and after being processed flat using, for example, a grinder, You may build up the above-mentioned titanium oxide by thermal spraying on the flat processed surface of this alloy. In this case, it is possible to easily form a flat surface on the bent pipe, and it is possible to combine both high corrosion resistance and high wear resistance on the flat surface.

DESCRIPTION OF SYMBOLS 1 Radiation part 1a Exhaust gas inlet part 2 Convection part 2a Exhaust gas outlet part 10 Water pipe 10a Flat surface 11 Straight pipe 12 Upper U-shaped curved pipe 13 Lower U-shaped curved pipe 20 Body part 21 Castable 21a Inner wall surface

Claims (3)

  A waste heat boiler for recovering waste heat of exhaust gas discharged from a smelting furnace using sulfide ore as a raw material, comprising a body part and a water pipe provided in a meandering manner on an inner wall surface thereof, wherein the water pipe is at least In at least two adjacent straight pipes arranged in the vicinity of the exhaust gas inlet of the body part and a U-shaped bent pipe connecting them, the side opposite to the side facing the inner wall surface is a flat surface without a gap. A waste heat boiler for non-ferrous metal smelting furnaces.   The flat surface of the U-shaped bent pipe is formed by building up on the side of the outer peripheral surface of the pipe opposite to the side facing the inner wall surface. 2. The method according to claim 1, wherein any one or more of the same material as the material of the pipe to be used, an alloy containing 40 mass% or more of nickel and 10 mass% or more of chromium, and titanium oxide is used. The waste heat boiler for a non-ferrous metal smelting furnace as described.   The flat surface of the U-shaped bent tube is formed by depositing on the opposite side of the outer peripheral surface of the tube to the side facing the inner wall surface, and the build-up is nickel on iron. The waste heat boiler for a non-ferrous metal smelting furnace according to claim 1, characterized in that after being built up with an alloy containing 40% by mass or more and 10% by mass or more of chromium, it is built up with titanium oxide thereon.

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