JP2018027870A - Sulfuric acid production system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method for sulfuric acid capable of preventing degradation of the conversion rate of sulfur dioxide in a waste gas into sulfur trioxide, and capable of suppressing deterioration of the production amount of sulfuric acid and the increase in used amount of a chemical agent for waste gas treatment.SOLUTION: There is provided a sulfuric acid production system 1 for producing sulfuric acid from sulfur dioxide included in a waste gas. The system comprises serial two-step conversion/absorption facilities 10, 20, and the conversion/absorption facilities 10, 20 have converters 11, 21 for converting sulfur dioxide in the waste gas to sulfur trioxide, and absorption towers 12, 22 bringing to absorption of sulfur trioxide generated by conversion in the converters 11, 21 into sulfuric acid. A bypass pipe 30 is provided and thereby, the waste gas passing through the converter 11 of the first conversion/absorption facility 10 located at a front step is bypassed to the converter 21 of the second conversion/absorption facility 20 to be introduced. Besides, a first blower 32 is provided between the first and second conversion/absorption facilities 10 and 20.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sulfuric acid production system, for example, a sulfuric acid production system used in a process for producing sulfuric acid from sulfur dioxide contained in waste gas discharged from a copper smelting process.

  As a method of obtaining crude copper using sulfide concentrate as a raw material, there is a smelting method using a smelting furnace such as a flash smelting furnace and a converter. In this smelting method, first, a sulfide concentrate is smelted in a smelting furnace to obtain a mat containing copper, a smelting furnace slag, and a smelting furnace waste gas containing sulfur dioxide. Next, in the converter, the mat obtained in the smelting furnace is blown and the impurity components contained in the mat are removed as converter slag, while the copper content is changed to crude copper. At this time, the sulfur content contained in the mat becomes sulfur dioxide and is discharged out of the system as a main component of the converter waste gas. Accordingly, most of the sulfur content in the sulfide concentrate becomes sulfur dioxide, which is distributed to the smelter waste gas and the converter waste gas and discharged out of the system.

  Here, since sulfur dioxide is a harmful substance, waste gas containing sulfur dioxide cannot be released to the atmosphere. Therefore, waste gas is introduced into the sulfuric acid production facility attached to the smelting facility, and sulfur dioxide in the waste gas is recovered as sulfuric acid, and the recovered waste gas is brought into contact with an alkaline solution to make it harmless and into the atmosphere. Released.

  Now, when manufacturing sulfuric acid from sulfur dioxide in waste gas discharged from a smelting method using a smelting furnace and a converter, for example, it is roughly classified that the received waste gas is clean. Gas purification process ”,“ Sulfuric acid production process ”that converts sulfur dioxide into sulfur trioxide to obtain sulfuric acid, and“ Tail gas treatment process ”that absorbs and removes trace amounts of sulfur oxide contained in the waste gas after that. (For example, refer to Patent Document 1).

  Specifically, FIG. 4 is a flow diagram showing a flow of producing sulfuric acid from waste gas containing sulfur dioxide discharged from the copper smelting process. FIG. 4 shows the configuration of a conventional sulfuric acid production system (sulfuric acid production system 5) in the sulfuric acid production process.

  In the gas purification step S101, the smelting waste gas passes through a humidification tower and a washing tower provided in the sulfuric acid production facility, thereby being cooled in contact with a large amount of water, and dust in the waste gas. Is trapped in water. The dust that could not be captured becomes mist and is removed by the mist cotrel. Next, in the drying tower, moisture is removed by contacting with concentrated sulfuric acid, and the purified gas (waste gas) is discharged.

  Subsequently, in the sulfuric acid production step S102, the waste gas obtained in the gas purification step S101 is sent to a converter to convert sulfur dioxide in the waste gas into sulfur trioxide. Then, the temperature of the gas is adjusted (cooled), sulfur trioxide is absorbed in 98% concentrated sulfuric acid in the absorption tower, and diluted with 95% sulfuric acid generated in water or a drying tower to obtain 98% concentrated sulfuric acid. In the waste gas from which sulfur trioxide has been absorbed and removed by sulfuric acid (this is referred to as “tail gas”), a trace amount of sulfur trioxide and unconverted sulfur dioxide exist.

  In the tail gas treatment step S103, the exhaust gas desulfurization equipment (detoxification tower) 80 is used to make the waste gas harmless by absorbing and fixing a trace amount of sulfur trioxide and unconverted sulfur dioxide in the tail gas with alkali. Released into the atmosphere.

  Here, in the sulfuric acid manufacturing step S102, for example, the processing is executed using the sulfuric acid manufacturing system 5. Specifically, the sulfuric acid production system 5 includes a converter 51 that converts sulfur dioxide in waste gas into sulfur trioxide, an absorption tower 52 that absorbs sulfur trioxide generated by conversion in the converter 51 into sulfuric acid, The conversion absorption equipment 50 which has is provided. Moreover, in the sulfuric acid production system 5, in order to collect as much sulfur dioxide as sulfuric acid as possible, the conversion absorption facility 50 is provided in two stages in series to convert to sulfur trioxide and to absorb sulfur trioxide into sulfuric acid. Is repeated. As shown in FIG. 4, in the sulfuric acid production system 5 provided with two stages of conversion absorption equipment in series, the “conversion absorption equipment 50” is the preceding conversion absorption equipment, and the “conversion absorption equipment 60” is the latter stage. It is a conversion absorption facility. Further, the converter constituting the conversion absorption facility 60 is referred to as “converter 61”, and the absorption tower is also referred to as “absorption tower 62”.

  Further, in the sulfuric acid production system 5, a bypass pipe 70 in which the waste gas that has passed through the converter 51 of the conversion absorption facility 50 located in the preceding stage is bypassed and introduced into the converter 61 of the conversion absorption facility 60 located in the subsequent stage. Is provided. Further, the bypass pipe 70 is provided with a shut-off valve 71 in the middle pipe.

  Now, the smelting process of crude copper may be paused. In that case, the reaction raw material in the sulfuric acid production step S102 for obtaining sulfuric acid by converting sulfur dioxide into sulfur trioxide is insufficient. The temperature of the converters 51 and 61 may decrease. When the converters 51 and 61 are at a low temperature, the reaction rate inside the converters 51 is reduced. Therefore, the use of the absorption towers 52 and 62 is partially omitted until the temperature is sufficiently increased, and the bypass pipe 70 is used. It was common to maintain sulfuric acid quality by changing to a non-stationary path (bypass). For example, as an example of the change, a technique disclosed in Patent Document 2 is known.

  Such an unsteady path using the bypass pipe 70 is normally closed by a shut-off valve 71 so that waste gas does not pass therethrough. At this time, the inside of the bypass pipe 70, which is an unsteady path, is stagnant and there is little supply of heat from the waste gas. As the shutoff valve 71 is repeatedly opened and closed, the powdered catalyst and a small amount of mist adhere to the valve body, and the valve body is corroded by the attached mist (sulfur trioxide and water). Go. As a result, a gap is formed between the contact surface of the valve body and the pipe.

  When the gap is formed, even if the shut-off valve 71 is closed, a part of the waste gas moves to the downstream side via the unsteady bypass pipe 70, and as a result, the carbon dioxide in the waste gas. This reduces the conversion of sulfur to sulfur trioxide, reduces the production of sulfuric acid, and increases the alkali consumption in the tail gas treatment process. Here, the conversion rate is a ratio when the number of moles of sulfur dioxide flowing into the converter is used as a denominator and the number of moles of sulfur dioxide remaining without changing to sulfur trioxide is used as a numerator. In this specification, since a plurality of converters are used, the total conversion rate is referred to as the conversion rate unless otherwise specified. The total conversion rate is obtained by subtracting the amount transferred between converters from the total value of each converter as the number of moles.

  In addition, due to such a situation, there is a possibility that the amount of ore processed in the smelting process, and consequently, the amount of crude copper produced may be reduced. Problems such as these can be solved by eliminating the formed gap by performing maintenance such as cleaning or replacement of the shut-off valve 71. However, in the maintenance work, the passage of waste gas to the work place is blocked. Or the equipment must be shut down for a long time of about one week.

JP 2001-130902 A JP 11-189404 A

  The present invention has been proposed in view of the conventional situation as described above, and in the production of sulfuric acid, it is possible to prevent a decrease in the conversion rate of sulfur dioxide in the waste gas to sulfur trioxide and to reduce the amount of sulfuric acid produced. Another object of the present invention is to provide a sulfuric acid production system capable of suppressing an increase in the amount of chemicals used for waste gas treatment.

  The inventors of the present invention have made extensive studies in order to solve the above-described problems. As a result, the bypass pipe used as the unsteady bypass circuit is provided with a blower at a position near to the pipe introduced to the converter of the second conversion absorption facility, and the blower is operated by the operation of the blower. By controlling so that the outlet side pressure of the first converter is larger than the inlet side pressure in the absorption tower of the first conversion absorption facility, the conversion rate can be reduced without maintenance for the clearance generated in the shutoff valve of the bypass pipe. The present inventors have found that it is possible to suppress a decrease, a decrease in the amount of sulfuric acid production associated therewith, and an increase in the amount of chemical used for waste gas treatment, and the present invention has been completed.

  (1) A first invention of the present invention is a sulfuric acid production system for producing sulfuric acid from sulfur dioxide contained in waste gas, comprising a conversion absorption facility in two stages in series, the conversion absorption facility upstream In order from the side, it has a converter that converts sulfur dioxide in the waste gas into sulfur trioxide, and an absorption tower that absorbs sulfur trioxide generated by conversion in the converter into sulfuric acid, and is located in the preceding stage. A detour pipe is provided for the waste gas that has passed through the converter of the first conversion absorption facility to be detoured and introduced into the converter of the second conversion absorption facility located in the subsequent stage, and A sulfuric acid production system in which a first blower is provided between the first conversion absorption facility and the second conversion absorption facility.

  (2) The second invention of the present invention is a sulfuric acid production system according to the first invention, wherein the bypass pipe is provided with a shutoff valve.

  (3) According to a third aspect of the present invention, in the first or second aspect, due to the operation of the first blower, the outlet-side pressure of the first blower is the first conversion absorption facility. It is a sulfuric acid production system which becomes larger than the inlet side pressure in the absorption tower, and the pressure inside the converter of the second conversion absorption equipment is equal to or higher than atmospheric pressure.

  (4) A fourth invention of the present invention is the invention according to any one of the first to third inventions, wherein the work generated by the first blower upstream of the converter of the first conversion absorption facility. A second blower capable of controlling the rotation speed of the blades according to the amount is provided, and the operation of the second blower causes the pressure inside the converter of the first conversion absorption facility to be equal to or higher than atmospheric pressure. This is a sulfuric acid production system.

  ADVANTAGE OF THE INVENTION According to this invention, while preventing the fall of the conversion rate of the sulfur dioxide in waste gas to sulfur trioxide, the fall of a sulfuric acid production amount and the increase in the chemical usage amount for waste gas processing can be suppressed.

It is a flowchart which shows the flow of manufacture of a sulfuric acid, and is a figure which shows the structure of the sulfuric acid manufacturing system used in a sulfuric acid manufacturing process. It is a graph which shows transition of the gas pressure (pressure P1, pressure P2) with respect to the elapsed time of operation in Example 1. In Example 1, it is a graph which shows transition of the conversion rate (%) from sulfur dioxide to sulfur trioxide, and the alkali usage in the flue gas desulfurization equipment performed in a post process. It is a flowchart which shows the flow of manufacture of a sulfuric acid, and is a figure which shows the structure of the conventional sulfuric acid manufacturing system used in a sulfuric acid manufacturing process.

  Hereinafter, a specific embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment, A various change is possible in the range which does not change the summary of this invention. In this specification, the notation “X to Y” (X and Y are arbitrary numerical values) means “X or more and Y or less”.

  FIG. 1 is a flowchart showing a flow of manufacturing sulfuric acid according to the present embodiment. FIG. 1 shows a process for producing sulfuric acid from waste gas discharged from the copper smelting process. The sulfuric acid production process includes a gas purification step S1 for purifying waste gas discharged from the copper smelting process, and a sulfuric acid production step for obtaining sulfuric acid by converting sulfur dioxide contained in the purified waste gas into sulfur trioxide. S2 and a tail gas treatment step S3 for absorbing and removing a trace amount of sulfur oxide contained in the waste gas thereafter. The tail gas treatment step S3 is performed using, for example, the flue gas desulfurization facility 45.

  Among them, the treatment in the sulfuric acid production step S <b> 2 is performed using the sulfuric acid production system 1. In FIG. 1, the structural block of the sulfuric acid manufacturing system 1 used by sulfuric acid manufacturing process S2 is shown collectively. In addition, in the sulfuric acid production system 1, the respective components are connected in series by piping, and the arrows in the figure indicate the flow of waste gas.

  As shown in FIG. 1, a sulfuric acid production system 1 includes, in order from the upstream side, a converter 11 that converts sulfur dioxide in waste gas into sulfur trioxide, and sulfur trioxide that is generated by conversion in the converter 11 as sulfuric acid. And a conversion absorption facility 10 having an absorption tower 12 to be absorbed by the reactor. The waste gas containing sulfur dioxide introduced into the converter 11 is a purified gas obtained through the gas purification step S1. The sulfuric acid production system 1 includes a main blower (second blower) 33 for sucking the waste gas obtained from the gas purification step S1 and feeding it to the converter 11 of the conversion absorption facility 10.

  Here, in the sulfuric acid production system 1, since it is necessary to collect sulfur dioxide as much sulfuric acid as possible, conversion to sulfur trioxide and absorption of sulfur trioxide into sulfuric acid are repeatedly performed. Therefore, the sulfuric acid production system 1 includes the conversion absorption equipment 10 in two stages in series. In addition, as shown in FIG. 1, in the sulfuric acid production system 1 provided with the conversion absorption equipment in two stages in series, the conversion absorption equipment 10 located in the preceding stage is referred to as the “first conversion absorption equipment 10” and is located in the subsequent stage. The conversion absorption facility is referred to as “second conversion absorption facility 20”. The converter constituting the second conversion absorption facility 20 is referred to as “converter 21”, and the absorption tower is referred to as “absorption tower 22”.

  In the sulfuric acid production system 1, the waste gas that has passed through the converter 11 of the first conversion absorption facility 10 located in the first stage bypasses the converter 21 of the second conversion absorption facility 20 located in the second stage. A bypass pipe 30 to be introduced is provided.

  Further, in the sulfuric acid production system 1, a first blower 32 is provided between the first conversion absorption facility 10 and the second conversion absorption facility 20.

[Conversion absorption equipment]
As described above, the conversion absorption facility 10 sequentially absorbs sulfur trioxide generated by conversion in the converter 11 that converts sulfur dioxide in waste gas into sulfur trioxide and the converter 11 in order from the upstream side. And an absorption tower 12 to be made. The conversion absorption equipment 10 is provided in two stages in series, and the devices constituting each equipment are the same in the first conversion absorption equipment 10 and the second conversion absorption equipment 20.

  In the conversion absorption facility 10, each component device is connected by piping. For example, waste gas discharged from the converter 11 moves to the absorption tower 12 through the piping connected to the absorption tower 12. .

(1) Converter The converter 11 is an apparatus for converting sulfur dioxide (SO ₂ ) in the purified gas (waste gas) obtained through the gas purification step S1 to sulfur trioxide (SO ₃ ). The converter 11 is configured by, for example, stacking a plurality of catalyst layers filled with an oxidation catalyst using vanadium pentoxide as an active material, and gas introduced from the upper part is supplied to the plurality of catalyst layers. By passing, the sulfur dioxide in the gas is oxidized and converted to sulfur trioxide. A gas containing sulfur trioxide is discharged from the outlet of the converter 11.

  A heat exchanger can be provided between the converter 11 and the absorption tower 12 described later. The iron exchanger adjusts the temperature of the waste gas containing sulfur trioxide discharged from the converter 11 to a predetermined temperature, and enables efficient absorption into sulfuric acid in the absorption tower 12 at the subsequent stage.

(2) Absorption tower The absorption tower 12 introduce | transduces the waste gas containing the sulfur trioxide produced | generated by conversion, and absorbs the sulfur trioxide in a sulfuric acid. Specifically, in the absorption tower 12, the waste gas and sulfuric acid are brought into contact with each other by spraying sulfuric acid on the introduced waste gas, and the sulfuric acid absorbs and recovers sulfur trioxide in the waste gas. Thus, the absorber 12, a high concentration of sulfuric acid is produced, on the one hand, the waste gas after SO ₃ was recovered is discharged from the discharge port.

  Here, as described above, the conversion absorption equipment 10 including at least the converter 11 and the absorption tower 12 is provided in two stages in series, and the conversion treatment for waste gas and the sulfuric acid after the conversion treatment are performed. The sulfur trioxide absorption treatment is repeatedly performed. Note that the number of installation stages is not limited to two, but may be three or more.

[Bypass piping]
The detour piping 30 is used for bypassing and introducing the waste gas that has passed through the converter 11 of the first conversion absorption facility 10 located in the preceding stage to the converter 21 of the second conversion absorption facility 20 positioned in the subsequent stage. It is piping. Specifically, the bypass pipe 30 branches from a pipe connecting the converter 11 and the absorption tower 12 in the first conversion absorption facility 10 and introduces waste gas into the converter 21 in the second conversion absorption facility 20. Connected to piping.

  Here, for example, in the process of smelting crude copper that discharges waste gas containing sulfur dioxide, the operation may be temporarily suspended due to regular maintenance or equipment repair. In such a case, in the sulfuric acid production system 1, the exhaust gas containing sulfur dioxide, which is a reaction raw material for producing sulfuric acid, is temporarily in a shortage, and as a result, the temperature of the converter 11 may be lowered. When the converter 11 becomes low temperature, the reaction rate in the converter 11 becomes low. Therefore, the use of the absorption tower 12 is partially omitted until the temperature is sufficiently increased. The quality of the sulfuric acid produced is maintained. At this time, the waste gas is transferred via the bypass pipe 30 as an unsteady bypass.

  The bypass pipe 30 is provided with a shut-off valve 31 for controlling the passage and non-passage of the waste gas in the pipe. Since the detour pipe 30 constitutes an unsteady detour as described above, the shut-off valve is normally closed, and waste gas does not pass through. The shut-off valve 31 may be a general valve that can control ON / OFF of the passage of waste gas. For example, a ball valve, a butterfly valve, or the like can be used.

[First blower]
The 1st air blower 32 is provided between the 1st conversion absorption equipment 10 and the 2nd conversion absorption equipment 20, and is comprised, for example from an axial blower. Hereinafter, the first blower 32 is also referred to as a “booster fan 32” as appropriate, and the same applies to FIG.

  Specifically, the booster fan 32 discharges the waste gas discharged from the absorption tower 12 in the first conversion absorption facility 10 and is in the middle of a pipe for introduction into the converter 21 in the second conversion absorption facility 20. Therefore, it is provided on the upstream side of the connection point between the pipe for introducing the waste gas to the converter 21 and the bypass pipe 30 connected to the pipe.

  Here, as described above, the bypass pipe 30 is in a state of being blocked by the shut-off valve in a steady state, but is in a stagnant state because it is opened only during an unsteady state, and from the waste gas. The amount of heat supplied is small, and as the shutoff valve is repeatedly opened and closed, powdered catalyst, a small amount of mist, and the like adhere to the valve body of the shutoff valve. Moreover, since the adhering mist contains sulfur trioxide and water, the adhering causes corrosion of the valve body. Then, due to adhesion of mist, a gap may be gradually formed between the contact surface of the valve element and the pipe, and the unsteady detour is routed through the formed gap even in the steady state. As a result, part of the waste gas passes through.

  The waste gas that has migrated via the detour is discharged through the converter 11 of the first conversion absorption facility 10 and contains sulfur trioxide converted from sulfur dioxide. When such waste gas containing sulfur trioxide passes through the detour and is not absorbed by the sulfuric acid in the absorption tower 12, and is introduced into the converter 21 of the second conversion absorption facility 20. The conversion rate of sulfur dioxide in the waste gas in the converter 21 to sulfur trioxide is reduced. As a result, the production amount of sulfuric acid is reduced, and the chemical use amount for the treatment of the waste gas discharged from the second conversion absorption equipment 20 is finally increased.

  In the sulfuric acid production system 1 according to the present embodiment, by providing the booster fan 32, even if a gap is formed in part in the shutoff valve of the bypass pipe 30, the bypass pipe 30 is routed through the bypass pipe 30. It is possible to prevent waste gas from passing through the detour.

  Specifically, in the sulfuric acid production system 1, by operating the booster fan 32 provided between the first conversion absorption facility 10 and the second conversion absorption facility 20, the booster fan 32 of the booster fan 32 is operated. The outlet side pressure becomes larger than the inlet side pressure in the absorption tower 12 of the first conversion absorption facility 10. More specifically, as shown in FIG. 1, in the two pressure gauges 41 and 42 provided before and after the shutoff valve of the bypass pipe 30 (upstream side and downstream side across the shutoff valve), the shutoff valve The pressure P1 indicated by the upstream pressure gauge 41 (inlet pressure in the absorption tower 12) and the pressure P2 indicated by the downstream pressure gauge 42 (pressure at the outlet side of the booster fan 32) satisfy “P2> P1”. Shows the relationship.

  Normally, the pressure P1 and the pressure P2 have a relationship of P1> P2, but the operation of the booster fan 32 can establish the relationship of “P2> P1”. Thereby, the waste gas containing sulfur trioxide generated through the converter 11 of the first conversion absorption facility 10 is converted into the second conversion absorption facility 20 via the detour via the detour piping 30. It is possible to prevent direct flow into the vessel 21. And while being able to prevent the fall of a conversion rate, the fall of sulfuric acid production amount and the increase in the chemical usage amount for waste gas processing can be suppressed.

  At this time, the booster fan 32 is operated so that the pressure inside the converter 21 of the second conversion absorption facility 20 becomes equal to or higher than the atmospheric pressure. As a result, even if the pressure is reduced due to gas dissolution (absorption) or the temperature is lowered, the converter 21 can be prevented from being crushed due to atmospheric pressure (outer shell protection). In the catalyst constituting the converter 21 of the second conversion absorption facility 20, it is possible to prevent moisture from the atmosphere from being mixed and damaged (catalyst protection).

  Further, the booster fan 32 is preferably constituted by a fan having a suction capacity smaller than that of the main blower (hereinafter also referred to as “second blower”). Thereby, even if the rotation speed of the booster fan 32 is increased, the suction side as well as the discharge side of the booster fan 32 can be maintained at a pressure higher than the atmospheric pressure.

[Second blower (main blower)]
As described above, the second blower 33 constitutes the main blower in the sulfuric acid production system 1, draws in the purified gas (waste gas) generated from the gas purification step S1, and removes the waste gas from the first blower 33. It is blown into the converter 11 of the conversion absorption facility 10 for introduction.

  Here, in the sulfuric acid production system 1, the power consumption increases as compared with the conventional case with the operation of the booster fan 32. From this, it is preferable that the second blower 33 is provided with, for example, an inverter and can appropriately control the rotational speed of the blades according to the work amount generated by the operation of the booster fan 32. Thus, by providing the second blower 33 that can control the rotation speed of the blades and operating the second blower 33, the amount of work increase accompanying the operation of the booster fan 32 is reduced, for example, the inverter output of the second blower 33 is reduced. The pressure inside the converter 11 of the first conversion absorption facility 10 becomes atmospheric pressure or higher.

  However, it is not possible to offset all the power consumption associated with the operation of the booster fan 32 by reducing the inverter output of the second blower 33 without reducing the amount of waste gas to be drawn. Therefore, as the booster fan 32, it is desirable to use a fan configured with a fan with as little power consumption as possible within a range in which the pressure relationship of “P2> P1” can be realized by its operation.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

[Example 1]
Using the sulfuric acid production system as shown in FIG. 1, sulfuric acid was produced and recovered from sulfur dioxide in the waste gas discharged from the crude copper smelting process.

  Specifically, the sulfuric acid production system 1 used in Example 1 is provided with two stages of conversion absorption equipment 10 including a converter 11 and an absorption tower 12 in series (first conversion absorption equipment 10 and second conversion absorption equipment 10 and second conversion absorption equipment 10 and second conversion absorption equipment 10. Conversion absorption equipment 20). Further, in the sulfuric acid production system 1, the waste gas discharged from the converter 11 of the first conversion absorption facility 10 bypasses and flows into the pipe introduced into the converter 21 of the second conversion absorption facility 20. A pipe 30 is provided. Further, in the sulfuric acid production system 1, a booster fan (first blower 32) is provided between the first conversion absorption facility 10 and the second conversion absorption facility 20.

  In the sulfuric acid production system 1, a shutoff valve is provided in the middle of the bypass pipe 30, pressure gauges 41 and 42 are installed before and after the shutoff valve (upstream and downstream), and the pressure gauge 41 upstream of the shutoff valve is provided. The pressure P1 indicated and the pressure P2 indicated by the downstream pressure gauge 42 were measured.

  FIG. 2 is a graph showing the transition of the gas pressure (pressure P1, pressure P2) with respect to the elapsed time of operation, and the booster fan 32 was operated from the time indicated by the arrow A in FIG. In addition, FIG. 3 shows the conversion rate (%) of sulfur dioxide to sulfur trioxide in the same time series as shown in FIG. 2, and the flue gas desulfurization equipment (waste gas treatment equipment) in the subsequent process (tail gas treatment process). It is a graph which shows transition of the alkali usage-amount. The amount of alkali used is indicated by the amount of caustic soda used (kg) per ton of sulfuric acid production. In addition, since the conversion rate and the amount of alkali used increase / decrease according to the amount of waste gas containing sulfur dioxide to be treated, the amount of waste gas was constant before and after the booster fan was operated. The amount of waste gas was measured near the outlet of the main blower (second blower).

  As shown in FIG. 2, by operating the booster fan 32, the pressure relationship between the upstream pressure P1 and the downstream pressure P2 was reversed, and the pressure relationship P2> P1 was realized. By this operation, as shown in FIG. 3, the conversion rate after the booster fan was operated was improved by about 0.04% on average, and the amount of alkali used in the exhaust gas desulfurization facility in the subsequent process was further reduced. From this result, it was found that the conversion rate can be effectively improved by providing and operating the booster fan 32.

[Reference example]
Taking the case of using a conventional sulfuric acid production system as shown in FIG. 4 as an example, a gap is formed in a part of the shutoff valve 71 of the bypass pipe 70, so that waste gas to be treated (one step at a predetermined rate). It is assumed that 1% of the mass ratio (including sulfur trioxide generated by the conversion of the eye) leaks from the gap and moves downstream through a detour path.

  In such a case, sulfur trioxide contained in the leaked waste gas is introduced into the second-stage converter 61 (converter of the conversion absorption facility 60), so that the second-stage conversion rate is 0. As a result, the total conversion rate is deteriorated by about 0.03% to 0.05%. In this way, when the overall conversion rate deteriorates, the amount of alkali used in the flue gas desulfurization facility in the subsequent process increases, and the amount of ore in the smelting operation may decrease as the gas throughput decreases. sell.

  According to the sulfuric acid production system according to the present invention, even when a gap is formed in the shutoff valve provided in the bypass pipe, unintended bypass of the waste gas due to poor closing can be surely prevented, and a reduction in conversion rate can be prevented. Can do. As a result, it is possible to suppress a decrease in the production amount of sulfuric acid and to suppress an increase in the amount of chemicals used for the treatment of tail gas, so that its industrial value is extremely large.

1 Sulfuric acid production system 10 Conversion absorption facility (first conversion absorption facility)
20 Conversion absorption facility (second conversion absorption facility)
11, 21 Converter 12, 22 Absorption tower 30 Detour piping 31 Shut-off valve 32 First blower (booster fan)
33 Second blower (main blower)
41, 42 Pressure gauge 45 Flue gas desulfurization equipment

Claims (4)

A sulfuric acid production system for producing sulfuric acid from sulfur dioxide contained in waste gas,
It is equipped with two stages of conversion absorption equipment in series,
The conversion absorption equipment is in order from the upstream side.
A converter for converting sulfur dioxide in the waste gas to sulfur trioxide;
An absorption tower that absorbs sulfur trioxide generated by conversion by the converter into sulfuric acid, and
There is provided a bypass pipe through which the waste gas that has passed through the converter of the first conversion absorption facility located in the first stage is detoured and introduced into the converter of the second conversion absorption facility located in the second stage,
Further, a sulfuric acid production system in which a first blower is provided between the first conversion absorption facility and the second conversion absorption facility. The sulfuric acid production system according to claim 1, wherein the bypass pipe is provided with a shutoff valve. By operating the first blower,
The outlet side pressure of the first blower is larger than the inlet side pressure in the absorption tower of the first conversion absorption facility, and the pressure inside the converter of the second conversion absorption facility is atmospheric pressure. The sulfuric acid production system according to claim 1 or 2 which becomes the above. A second blower capable of controlling the rotation speed of the blades according to the amount of work generated by the first blower is provided upstream of the converter of the first conversion absorption facility,
Due to the operation of the second blower,
The sulfuric acid production system according to any one of claims 1 to 3, wherein a pressure inside the converter of the first conversion absorption facility is equal to or higher than atmospheric pressure.

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