JP2015214454A - Method and apparatus for operation of sulfuric acid plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for operation of a sulfuric acid plant which allow diversification of the form of heat recovery.SOLUTION: An operation apparatus for a sulfuric acid plant includes a plurality of stages of conversion catalyst layers to which a SO-containing gas is supplied in order, first heat recovery means of recovering heat from a front-stage gas discharged from a front-stage conversion catalyst layer, among the conversion catalyst layers, second heat recovery means of recovering heat from a latter-stage gas discharged from a latter-stage conversion catalyst layer, among the conversion catalyst layers, and control means of controlling the heat recovery ratio of the first and second heat recovery means.

Description

  The present invention relates to a method for operating a sulfuric acid factory and an apparatus for operating a sulfuric acid factory.

Copper ore produced in copper mines is mainly sulfide ore. Roughly categorizing sulfide ores, relatively high copper grade secondary copper sulfides mainly composed of minerals such as chalcocite (Cu ₂ S) and copper indigo (CuS), and the first generation mainly composed of chalcopyrite (CuFeS ₂ ) Divided into sulfide ores. In recent years, copper ores collected at copper mines are mainly the latter. As a result, impurities such as iron and sulfur increase, and the quality of crude ore copper tends to decrease. This causes factors such as a decrease in copper quality and an increase in iron content of copper concentrates produced for copper smelting in the mine.

  In a dry copper smelter that processes copper concentrate, copper is generally recovered as product electrolytic copper, iron as slag, and sulfur as sulfuric acid. The increase in iron in copper concentrates is a factor that further deteriorates the supply and demand of slag, which is chronically pressing on business profits, and the increase in sulfur has led to an increase in overall desulfurization costs, including electricity costs at sulfuric acid plants. Invite. In other words, a drop in the copper grade of copper concentrate is one of the major concerns of the copper smelting industry, but in recent years when fuel and electricity prices are rising and staying high, these energy consumptions can be reduced. Realizing efficient factory operation is an important issue.

Sulfuric acid production process, the sulfite (SO ₂₎ gas generated in non-ferrous smelting furnaces such as copper, zinc even plant as a raw material, the SO ₂ gas burned elemental sulfur is generated at the factory as a raw material Even so, it is important to increase the concentration of SO ₂ in the raw material gas in order to operate at a low cost. This is because the electric power of the blower for the gas pumping can be reduced by suppressing the volume of the raw material gas handled in the manufacturing facility.

However, the SO ₂ concentration in the gas used as the raw material for the sulfuric acid production process is adjusted by diluting the high concentration exhaust gas at the outlet of the non-ferrous metal smelting furnace or roasting furnace with air to an appropriate concentration. It is common. It can be said that the SO ₂ concentration after dilution is determined by the rate at which SO ₂ can be oxidized to SO ₃ before the absorption operation into sulfuric acid, that is, the maximum capacity of the conversion equipment.

This conversion of SO ₂ to SO ₃ is an oxidation reaction. Therefore, the reaction proceeds stepwise in the converter by appropriately controlling the temperature while performing heat exchange and heat removal. The conversion rate of a sulfuric acid factory of a double contact system that performs SO ₃ absorption operation in two stages is generally 99.6 to 99.9%.

The main factors affecting the conversion rate are the temperature and the oxygen concentration in the raw material gas. Of these, it is important that the temperature is not higher than necessary in consideration of the equilibrium conversion rate and reaction rate, and the oxygen concentration is equal to or greater than the oxidation reaction equivalent to the SO ₂ contained in the raw material gas. Of course, it goes without saying that the higher the concentration, the more efficient it is to obtain a high conversion rate.

  As described above, it is necessary to dilute to a predetermined concentration with air, not only to ensure a predetermined amount of oxygen, but also to reduce the heat generation per gas volume, thereby increasing the temperature in the converter more than necessary. It is also a reason for suppressing the above. On the other hand, as described above, introducing a large amount of dilution air causes an increase in power due to an increase in the amount of raw material gas, and also increases the gas flow capacity of the factory, that is, the pressure loss of the equipment and the capacity of the blower. When the upper limit is reached, it is the factory's sulfuric acid production capacity.

Therefore, reducing the amount of air used for dilution and operating at a high SO ₂ concentration can reduce construction costs from the standpoint of energy saving, the sulfuric acid production capacity of the factory, and the construction of a new factory. It is also important from the point of view. In other words, the operating SO ₂ concentration is also an index of the efficiency of the sulfuric acid factory, and there is a great merit in increasing it, and various methods have been taken in recent years.

In the sulfuric acid production process, in order to increase the operating SO ₂ gas concentration, as described above, it is generally necessary to appropriately remove excess heat at an appropriate location in the process, and further, the removed heat It is desirable to use it effectively.

The heat generation in the sulfuric acid production process is mainly: (1) heat generation during sulfur combustion process, (2) heat generation during SO ₂ oxidation (conversion) process, and (3) heat generation during H ₂ SO ₄ generation process. These can be divided into the following three, and these can be represented by the thermochemical reaction formula as follows.
S + O ₂ = SO ₂ +297 kJ / mol (1)
_{SO 2 + 0.5O 2 = SO 3} + 99kJ / mol (2)
H ₂ O + SO ₃ = H ₂ SO ₄ + 133 kJ / mol (3)

  In general, most of the heat generated by sulfur combustion in the formula (1) is recovered by the waste heat boiler before entering the sulfuric acid production process. Even if it is not sulfur combustion, speaking of the copper smelting industry, oxidation of sulfur contained in copper concentrate processed in flash furnaces, oxidation of sulfur contained in copper mats processed in converters, etc. Corresponds.

  Heat generation due to oxidation of sulfur dioxide in equation (2) occurs in the converter in the sulfuric acid production process and is controlled by a plurality of heat exchangers arranged before and after the converter. Heat exchange is performed between the raw material gas having a low temperature, the absorption tower outlet gas, and the like, and the converter catalyst layer outlet gas, etc., which has become high temperature due to the reaction heat, and the temperature at each place is appropriately controlled. Finally, most of the heat is removed by the acid cooler of the absorption tower.

  The heat generation in the formula (3) occurs when sulfuric acid is newly generated in the absorption tower. In general, most of this is also removed by an acid cooler.

However, for the reasons described above, in recent years, in order to increase the energy efficiency of sulfuric acid factories, the technology for increasing the operating SO ₂ concentration and actively recovering the exothermic component of equations (2) and (3). Development is thriving.

In the exothermic component of formula (2), the amount of processing gas per unit time decreases by increasing the SO ₂ concentration, but the temperature rise per unit gas volume increases. Furthermore, the gas sensible heat brought into the absorption tower is reduced, so that the temperatures of the converter and the heat exchanger are likely to rise. For this reason, there are many technologies that add air heat exchangers, waste heat boilers, economizers, etc. at appropriate locations, and appropriately recover and reuse excess heat as high-temperature air or steam to reduce energy consumption. Seen.

For example, in Patent Document 1, a part of gas sensible heat is heated from an outlet gas of the converter, which has become high in the reaction of the formula (2), by an air heat exchanger (SO ₃ cooler) arranged in parallel with the heat exchanger. Collected as air. The recovered high-temperature air is used as dilution air for a copper concentrate dryer combustion furnace, and the amount of fossil fuel such as heavy oil used is suppressed.

Further, in recent years, the exothermic component of the formula (3) indicates that the generated heat is continuously 1 MPaG while controlling the concentrated sulfuric acid for absorbing SO ₃ at 99.0 to 99.3 mass% and 210 to 230 ° C. A method of recovering as steam of a degree has also been developed. This method is realized by suppressing the corrosion rate caused by hot concentrated sulfuric acid using a special high corrosion resistance material, and it can be seen that it is introduced into a newly constructed factory. In the conventional technology, the absorption tower circulates concentrated sulfuric acid at 70 to 100 ° C. However, in this method, it acts as a heat recovery tower and an absorption tower, and can be effectively used in the form of an increase in the temperature of the cooling water. The missing heat can be recovered as about 1 MPaG of steam.

JP 2007-269550 A

In these heat recovery systems, the amount of heat recovery increases or decreases in conjunction with the factory operating level (processed SO ₂ amount), but the form recovered by the heat recovery equipment is either steam or hot water, or Even if it is high-temperature air, if it exceeds the required amount at the point of use, a part is released, or conversely if there is a shortage, fuel is used for compensation. This is basically the same whether there is a single heat recovery facility or a plurality of heat recovery facilities.

  Moreover, since the heat recovery system described above is also recovered with 1 MPaG vapor, its usage is limited. If it is a factory to be newly constructed, a turbine or a dryer that uses the heat source may be installed. Alternatively, the steam can be sold to other factories in the complex. However, when the system is introduced into an existing factory in a lump, the amount of investment may increase if there are few effective use facilities or if it is necessary to newly install an effective use facility.

  In recent years, the price of electricity and fossil fuels has risen, and the importance of heat recovery and its effective use is increasing. It is important to select the most efficient and cost-effective method in terms of recovery and use, not just the amount of heat recovery.

  An object of this invention is to provide the operating apparatus of a sulfuric acid factory which can diversify the form of heat recovery, and the operating method of a sulfuric acid factory in view of said subject.

The operation apparatus of the sulfuric acid factory according to the present invention includes a plurality of conversion catalyst layers to which SO ₂ -containing gas is sequentially supplied, and a front stage gas discharged from a previous conversion catalyst layer among the plurality of conversion catalyst layers. A first heat recovery means for recovering heat; a second heat recovery means for recovering heat from a downstream gas exhausted from a downstream conversion catalyst layer of the plurality of conversion catalyst layers; and the first heat recovery means. And a control means for controlling a heat recovery ratio of the second heat recovery means.

The control means may control the heat recovery ratio according to the temperature of the gas after heat recovery by the first heat recovery means. The control means may control the heat recovery ratio so that the amount of heat recovered by the first heat recovery device is 10% to 20% of the total amount of heat recovered from the SO ₂ -containing gas. . More preferably, the heat recovery ratio may be controlled so as to be 12% to 15% of the total heat quantity. A pre-converter including a conversion catalyst layer, and a converter that is supplied with a gas that has undergone conversion by the pre-converter and includes a conversion catalyst layer, and the pre-stage gas is a gas that has undergone conversion by the pre-converter, and The latter stage gas may be a gas that has been converted by the converter.

  The converter may include a plurality of stages of the conversion catalyst layer, and the post-stage gas may be gas discharged from the second and subsequent catalyst layers of the converter. The control means may control the heat recovery ratio based on the temperature of the gas supplied to the second and subsequent catalyst layers of the converter. There may be provided a flow rate adjusting means for controlling the gas flow rate passing through the pre-converter to 70% or less of the total gas flow rate. The control means controls the heat recovery ratio so that the temperature of the gas supplied to the converter becomes equal to or higher than a lower limit value of a temperature that reaches equilibrium after passing through the catalyst layer at the front stage of the converter. May be. The first heat recovery means may be at least one of a waste heat boiler and a steam superheater, and the second heat recovery means may be an air heat exchanger.

The method for operating a sulfuric acid factory according to the present invention includes a first heat recovery step of recovering heat from a preceding gas that has passed through a preceding conversion catalyst layer among a plurality of conversion catalyst layers to which SO ₂ -containing gas is sequentially supplied. The second heat recovery step of recovering heat from the latter stage gas passing through the latter conversion catalyst layer among the plurality of stages of the conversion catalyst layers, and the heat recovery ratio of the first heat recovery step and the second heat recovery step And a control step for controlling.
In the sulfuric acid factory, the SO ₂ load (processing capacity) may be 90% or more. Although this method is effective in any scale of sulfuric acid factory, the sulfuric acid production capacity of the sulfuric acid factory is high at 1000 t / day to 3000 t / day.

  According to the present invention, the form of heat recovery can be diversified.

It is a figure which shows an example of the sulfuric acid factory which concerns on embodiment. It is a flowchart showing an example of the operating method of a sulfuric acid factory. And equilibrium conversion curve at SO ₂ concentrations and the O ₂ concentration is a diagram illustrating the conversion operations line thereto.

(Embodiment)
The present embodiment discloses an operation apparatus and an operation method for appropriately adjusting the ratio of heat recovery in a sulfuric acid factory having two or more types of heat recovery facilities having different heat recovery modes. According to the operation apparatus and operation method of this sulfuric acid factory, the form of heat recovery can be diversified. As a result, according to the operating rate of the recovered heat usage destination and the unit price of fossil fuels such as electricity, heavy oil, and light oil, the amount of heat recovered in an optimal heat recovery form with appropriate economic benefits, Driving is possible.

FIG. 1 is a diagram illustrating an example of a sulfuric acid factory 100 according to the present embodiment. As an example, the SO ₂ load of the SO ₂ -containing gas supplied to the sulfuric acid factory 100 is about 205 Nm ³ / (t · day) to 229 Nm ³ / (t · day). The sulfuric acid production capacity is about 1000 t / day to 3000 t / day. The sulfuric acid factory 100 includes a converter 1, a pre-converter 2, and the like. The converter 1 is a device for converting SO ₂ into SO ₃ . Inside the converter 1, a layer containing a conversion catalyst used for a reaction (conversion reaction) in which SO ₂ is converted to SO ₃ (hereinafter referred to as a conversion catalyst layer) is disposed. In the example of FIG. 1, first to fourth four conversion catalyst layers are arranged. The SO ₂ supplied to the converter 1 passes through the first layer, the second layer, the third layer, and the fourth layer in contact with each other in this order. SO ₂ in contact with the conversion catalyst layer is oxidized to SO ₃ by the catalytic action of the conversion catalyst layer. This reaction corresponds to the reaction of the above formula (2). Due to the heat continuously generated in the converter 1, the temperature of the outlet gas of the conversion catalyst layer rises. The pre-converter 2 is a device for converting a part of the SO ₂ gas before being supplied to the converter 1 into SO ₃ . In the example of FIG. 1, two conversion catalyst layers, an upper layer and a lower layer, are arranged. Also in the pre-converter 2, the SO _{2 that} has come into contact with the conversion catalyst layer is oxidized to SO ₃ by the catalytic action of the conversion catalyst layer.

Further, the sulfuric acid factory according to the present embodiment includes heat recovery means such as the waste heat boiler 3, the SO ₃ cooler 4, and the absorption towers 12 and 14. The waste heat boiler 3 is a device that recovers heat as steam from the gas discharged from the pre-converter 2. The SO ₃ cooler 4 is a device that recovers heat as high-temperature air from a gas discharged from any catalyst layer of the converter 1 (hereinafter referred to as an outlet gas of the conversion catalyst layer). The absorption towers 12 and 14 are devices that generate the reaction of the above formula (3), and also function as a device that recovers heat from the outlet gas of any conversion catalyst layer of the converter 1. In the present embodiment, the waste heat boiler 3 functions as the first heat recovery means, and the SO ₃ cooler 4 functions as the second heat recovery means.

In addition, the sulfuric acid factory 100 performs heat exchange on heat exchangers 6 to 9 that exchange heat with respect to the SO ₂ gas before being supplied to the converter 1, and the outlet gas of any conversion catalyst layer of the converter 1. Heat exchangers 10 and 11 that perform heat exchange are provided. Moreover, the sulfuric acid factory which concerns on this embodiment is provided with the control valves 17-24 which adjust flow volume. In addition, the sulfuric acid factory according to the present embodiment detects the temperature of the gas after the heat recovery by the waste heat boiler 3 and the temperature of the inlet gas of the conversion catalyst layer in the second and subsequent stages of the converter 1. The temperature sensor 32 is provided. Further, the sulfuric acid factory according to the present embodiment includes a controller 40 that controls the opening degree of the control valves 17 to 24. In the present embodiment, the control valves 17 to 24 and the controller 40 function as control means for controlling the heat recovery ratio of the first heat recovery means and the second heat recovery means.

Hereinafter, an outline of the operation of the sulfuric acid factory 100 will be described. In the following description, the raw material gas is SO ₂ gas before being supplied to the converter 1, and the outlet gas of the conversion catalyst layer is exhausted from any of the conversion catalyst layers of the converter 1. It is the gas that is.

The SO ₂ -containing gas sent to the sulfuric acid factory is pumped by the main blower 16 and supplied to the converter 1 as a raw material gas through the control valve 19 and the like. If the temperature of the raw material gas supplied to the converter 1 is too low, the oxidation reaction (conversion) of SO ₂ does not occur, so the raw material gas must be preheated. Therefore, the heat of the outlet gas of the conversion catalyst layer of the converter 1 may be used for heating the raw material gas in the heat exchangers 6 to 9. Alternatively, by bypassing these heat exchangers using the control valve 20 and mixing a part of the catalyst layer outlet gas and the raw material gas of the first layer, the outlet gas of the first layer is set to an appropriate temperature. Also good.

  In the converter 1, a heat exchanger is arranged for each layer in order to obtain an inlet temperature suitable for the reaction. Generally, the reaction of the above formula (2) proceeds as the catalyst layer passes, and the temperature of the raw material gas increases. For example, the temperature of the outlet gas of the first layer is 550 ° C to 620 ° C. The outlet gas of the first layer exchanges heat with the source gas at 250 ° C. to 350 ° C. in the heat exchanger 9, is cooled to 390 to 460 ° C., and flows into the second layer. The outlet gas of the second layer is adjusted to 180 to 230 ° C. by passing through the heat exchanger 10 or the heat exchanger 11 and sent to the absorption tower 12. The low-temperature return gas discharged from the absorption tower 12 exchanges heat with the outlet gas of the second layer in the heat exchangers 10 and 11 via the gas cleaning tower 13, and after reaching 430 to 460 ° C., the third layer Flow into.

  The outlet gas of the third layer exchanges heat with the source gas at 250 ° C. to 300 ° C. in the heat exchanger 8 to become 410 to 440 ° C. and flows into the fourth layer. The outlet gas of the fourth layer passes through the heat exchanger 7 and the heat exchanger 6, heats the raw material gas fed from the main blower 16 to 250 ° C. to 350 ° C., and then is sent to the absorption tower 14. The gas discharged from the absorption tower 14 is discharged as exhaust gas via the cleaning tower 15.

  As described above, the inlet temperature of each conversion catalyst layer of the converter 1, that is, the reaction start temperature, is maintained at an appropriate temperature of 390 to 460 ° C. Heat is exchanged reciprocally by heat exchange between the low-temperature gas (raw material gas and absorption tower exhaust gas) and the high-temperature gas after reaction (catalyst layer outlet gas), but if necessary, the control valves 17 and 20 are provided. It may be fine-tuned by using.

For example, when the temperature of the source gas supplied from the main blower 16 is too high, the control valve 17 is opened, and the source gas before heating is mixed and adjusted to the optimum temperature. Alternatively, the raw material gas before heating is mixed and cooled by adjusting the control valve 20 to the outlet gas heated by the SO ₂ oxidation reaction proceeding more than expected in the first layer.

As described above, the temperature in the converter 1 is properly maintained by the heat exchanger, but the heat continuously generated by the conversion of SO ₂ is largely excessive with respect to the amount required for the heating of the gas. It is. This excess heat is accumulated in the absorption tower 12 or the absorption tower 14 as gas sensible heat, cooled by an attached acid cooler, and most of it is discarded. In general, the amount of heat is large, but there is no effective use due to the large volume handled at low temperatures. Therefore, the effective use of this heat has a great impact on energy efficiency.

On the other hand, in the present embodiment, the waste heat boiler 3 is disposed at the outlet of the pre-converter 2. An SO ₃ cooler 4 equipped with an air fan 5 is arranged at the outlet of the second layer of the converter 1. The waste heat boiler 3 and the SO ₃ cooler 4 recover heat as steam and hot air. These heat recoveries are the conditions required by the high SO ₂ concentration operation of the sulfuric acid factory, that is, improving the temperature rise of the gas and recovering excess heat from the high temperature gas in a good quality form. It is the form of heat used for For example, steam obtained from the waste heat boiler 3 is often used in a steam turbine for power generation, and high-temperature air obtained from the SO ₃ cooler 4 is used as a heat source for drying equipment and heating equipment. Often used

In this embodiment, the control valves 18 and 19 are valves that change the amount of gas supplied to the pre-converter 2 and the amount of gas supplied to the converter 1, and basically the operation load (processing SO ₂ amount). The supply gas ratio is changed accordingly. The control valve 21 is a valve that adjusts the amount of heat removed from the hot gas at the outlet of the pre-converter 2. That is, when the opening degree of the control valve 21 is increased, the amount of bypassing the waste heat boiler 3 is increased, so that the amount of heat recovered in the waste heat boiler 3 is decreased.

The control valves 22 to 24 are valves arranged at the reaction gas (hot gas) side outlets of the SO ₃ cooler 4, the heat exchanger 10, and the heat exchanger 11, respectively, and the outlet of the second layer of the converter 1. Adjust the gas distribution rate. That is, when the opening degree of the control valve 22 is increased, the amount of heat recovered by the SO ₃ cooler 4 is increased. The control valves 22 to 24 are not all necessary when there is a sufficient difference in pressure loss between the SO ₃ cooler 4, the heat exchanger 10, and the heat exchanger 11 attached to each of the control valves 22 to 24. If a valve is provided in a circuit with the smallest pressure loss (gas flows easily), the flow rate ratio of each facility can be changed by opening and closing the valve.

In the present embodiment, the heat recovery amount in the waste heat boiler 3 and the SO ₃ cooler 4 is adjusted. The total amount of heat that can be recovered by the waste heat boiler 3 and the SO ₃ cooler 4 is basically determined by the operation load (SO ₂ amount). This limited heat recovery amount is adjusted more appropriately using the control valves 17 to 24.

By the way, in a copper smelter using a converter that performs batch copper making, the SO ₂ load of the sulfuric acid factory fluctuates due to the wrought copper cycle of the converter (the SO ₂ concentration of the exhaust gas derived from the converter fluctuates depending on the wrought copper cycle. To do). In this case, the amount of steam generated in the boiler for the exhaust gas of the converter and the amount of steam generated in the waste heat boiler 3 of the sulfuric acid factory 100 basically have overlapping peaks, and thus exceed the output of the steam turbine power generation facility, It may release unusable vapors.

If the steam cannot be discharged, the amount of steam generated in the waste heat boiler 3 can be suppressed by increasing the amount of recovered heat (high-temperature hot air amount or temperature) in the SO ₃ cooler 4. In general, power generation by a steam turbine is not advantageous from the viewpoint of energy conversion efficiency compared to drying and heating applications. Therefore, depending on the price of fossil fuel consumed in drying and heating equipment, it is more economically advantageous to reduce the use of fossil fuels such as heavy oil in the drying equipment, regardless of whether power generation equipment output is limited. Sometimes it becomes. In any case, adjusting the heat recovery ratio of the heat recovery facilities with different heat recovery modes can be optimized according to the facility capacity and energy price of the use destination.

Then, the specific example of the operating method of the sulfuric acid factory which concerns on this embodiment is described. FIG. 2 is a flowchart showing an example of the operation method. The heat recovery ratio according to the present embodiment is a ratio between the heat recovery amount in the waste heat boiler 3 and the heat recovery amount in the SO ₃ cooler 4. As illustrated in FIG. 2, the controller 40 controls the opening degree of the control valves 17 to 20 to convert the raw material gas supplied from the main blower 16 into the heat exchangers 6 to 9, the pre-converter 2, and the converter. Distribution is supplied to the outlets of the first layer (step S1). Of these, the former two paths are temperature-adjusted and supplied to the pre-converter 2.

Next, the controller 40 adjusts the amount of gas supplied to the waste heat boiler 3 of the raw material gas that has passed the pre-converter 2 and has reached a high temperature by using the control valve 21 (step S2). Thereby, the heat recovery amount in the waste heat boiler 3 is adjusted. The controller 40 controls the opening degree of the control valve 21 according to the inlet temperature of the first layer of the converter 1 (the detected temperature of the temperature sensor 31). The inlet temperature of the first layer is usually set at 380 to 450 ° C., and is changed according to the heat recovery ratio between the waste heat boiler 3 and the SO ₃ cooler 4.

Next, the controller 40 adjusts the amount of gas supplied to the SO ₃ cooler 4 by adjusting the opening degree of the control valves 22 to 24 (step S3). That is, in order to increase the heat recovery amount, the opening degree of the control valve 22 is increased and the opening degrees of the control valves 23 and 24 are decreased. In this case, the controller 40 may control the opening degree of the control valves 22 to 24 according to the temperature detected by the temperature sensor 32. However, if the pressure loss of the SO ₃ cooler 4 and the heat exchangers 10 and 11 installed in parallel to the SO ₃ cooler 4 can be optimally designed, one or two control valves 22 to 24 can be connected to the SO ₃ cooler 4. The supply gas amount can also be adjusted.

For example, in the present embodiment, when the same SO ₂ load is applied, the opening degree of the control valve 21 is increased, and when the heat recovery amount in the waste heat boiler 3 is reduced, the opening degree of the control valve 22 is increased. If necessary, the opening degree of the control valves 23 and 24 is decreased, and the amount of heat recovered in the SO ₃ cooler 4 is increased. In addition, although the temperature of each catalyst layer of the converter 1 is changed by adjusting the heat recovery ratio, the amount of catalyst loaded in the catalyst layers after the first layer is necessary and sufficient to reach the equilibrium conversion rate under each temperature condition. An appropriate amount may be charged so that the conversion rate is not affected.

  The controller 40 preferably controls the heat recovery ratio so that the amount of heat recovered by the waste heat boiler 3 is 10% to 20% of the total amount of heat recovered from the raw material gas supplied from the main blower 16. . More preferably, it is controlled to 12% to 15% of the total heat amount. This is because, as described above, too much steam recovered by the boiler is disadvantageous in terms of cost, and if it is too little, the amount of heat to be discarded increases.

It is preferable that the controller 40 controls the main blower 16 and the control valves 17 to 20 so that the amount of gas passing through the pre-converter 2 is 70% or less of the total amount of gas. This is because when the SO ₂ load is low, the gas passing through the pre-converter 2 is reduced, the gas flow path is shortened, the power consumption of the main blower 16 can be suppressed, and an advantageous operation in terms of energy saving is achieved. Because it can.

  It is preferable that the controller 40 controls the heat recovery ratio so that the temperature of the raw material gas supplied to the converter 1 is equal to or higher than the lower limit value of the temperature that reaches the equilibrium after passing through the first layer. This is because the conversion rate in the converter 1 can be improved.

In the present embodiment, the waste heat boiler is used as the first heat recovery means, but other heat recovery means may be used, and at least one of the waste heat boiler and the steam superheater may be used. In the present embodiment, the SO ₃ cooler is used as the second heat recovery means, but other heat recovery means such as other air heat exchangers may be used.

In the present embodiment, heat is recovered from the SO ₂ -containing gas passing through the pre-converter 2 using the first heat recovery means, and heat is recovered from the SO ₂ -containing gas passing through the converter 1 using the second heat recovery means. However, it is not limited to this. The pre-converter 2 and the converter 1 including the pre-converter 2 and the converter 1 recover heat from the pre-stage gas discharged from the pre-stage conversion catalyst layer among the multi-stage conversion catalyst layers using the first heat recovery means, and the multi-stage conversion catalyst layers Among them, heat may be recovered from the latter stage gas discharged from the latter stage conversion catalyst layer using the second heat recovery means.

  In the present embodiment, the temperature sensor 31 detects the temperature of the mixed gas that has passed through the control valves 19 and 21, but the temperature of the gas that has passed through the waste heat boiler 3 may be detected. In the present embodiment, the temperature sensor 32 detects the temperature of the inlet gas supplied to the second layer of the converter 1, but detects the temperature of the inlet gas of the conversion catalyst layer after the second layer. do it.

  Hereinafter, the example which processed the sulfuric acid factory according to the adjustment method concerning the above-mentioned embodiment is described.

In Example 1, operation adjustment was performed so that the average amount of processing gas (outlet gas amount of the main blower 16) was 3200 Nm ³ / min, SO ₂ concentration was 13.5 mol%, and O ₂ concentration was 13.9 mol% on a daily average. And the opening degree of the control valve 21 was adjusted so that the inlet temperature of the first layer of the converter 1 was 415 ° C. Moreover, the opening degree of the control valve 21 was adjusted so that the inlet temperature of the 1st layer might be 425 degreeC on the same conditions. Tables 1 and 2 show the control valve opening, the heat recovery amount, the converter temperature, and the conversion rate in each case.

In the case of Table 1, the average opening degree of the control valve 21 was 18%, and the steam recovery amount in the waste heat boiler 3 was 16.9 t / h on average (693 MJ / min in terms of heat amount). At this time, the opening degree of the control valve 22 was set to 75%, and the SO ₃ cooler 4 recovered high-temperature air at 355 ° C. at 320 Nm ³ / min (calorie conversion 155 MJ / min).

In the case of Table 2, the average opening degree of the control valve 21 was 27%, and the steam recovery amount in the waste heat boiler 3 was 15.5 t / h (recovered heat amount conversion 636 MJ / min) on average. At this time, the opening degree of the control valve 22 was set to 75%, and the SO ₃ cooler 4 recovered high-temperature air at 355 ° C. at 320 Nm ³ / min (calorie conversion 155 MJ / min).

Comparing these two cases, with almost the same SO ₂ load, by adjusting the opening degree of the control valves 21 to 24, the total recovered heat amounts of the two heat recovery facilities are almost the same as 848 MJ / min and 841 MJ / min, respectively. was gotten. When the same recovered heat amount cannot be achieved, the necessary heat removal amount in the series of sulfuric acid production facilities in FIG. 1 is not satisfied, and an inappropriate temperature rise is caused at a specific site. For example, there is an increase in heat loss to cooling water due to an increase in circulating acid temperature, an increase in corrosion of a circulation pump, etc., and a decrease in conversion rate due to an inappropriate temperature increase in the converter catalyst layer. In Example 1, such a problem did not occur, and the same conversion rate of 99.7% was obtained.

As Example 2, the daily average is 3200 Nm ³ / min, the SO ₂ concentration is 13.5 mol%, and the O ₂ concentration is 13.9 mol% in the same manner as in Example 1 in terms of the total processing gas amount (main blower 16 outlet gas amount). Operation adjustment was performed so that the opening of the control valve 21 was adjusted so that the inlet temperature of the first layer of the converter 1 was 440 ° C. Table 3 shows the control valve opening, heat recovery amount, converter temperature, and conversion rate in that case.

In this case, the average opening degree of the control valve 21 was 34%, and the steam recovery amount in the waste heat boiler 3 was 13.9 t / h on average (heat conversion 570 MJ / min). The degree of opening of the control valve 22 was 100%, and the SO ₃ cooler 4 recovered high temperature air at 388 ° C. at 477 Nm ³ / min (calorific value conversion 252 MJ / min). Even in this case, the total heat recovery amount was 494 MJ / min, which was the same as in Example 1.

The difference between Example 1 and Example 2 is the conversion rate. In Example 2, the conversion rate decreased to 99.65%. This can be explained by FIG. FIG. 3 is a comparison of the equilibrium conversion curve at the SO ₂ concentration and the O ₂ concentration with the conversion operation line (straight line) corresponding thereto in the example.

  In general, in the pre-converter 2 and the first layer (referred to as the foremost stage) of the converter 1 having a high reaction rate, the optimum catalyst amount is set according to the design gas amount, gas composition, reaction start temperature, and the like. This is to suppress a temperature rise that exceeds the operating temperature of the catalyst. On the other hand, the second and subsequent catalyst layers (referred to as the latter stage) whose reaction rate is reduced and does not exceed the catalyst use temperature must be filled with a sufficient amount of catalyst in order to proceed to the equilibrium conversion rate. is there.

  In case 2 of Example 1 in FIG. 3, the reaction of the first layer is started from 425 ° C., and reaches almost the equilibrium temperature of 576 ° C., and the conversion rate so far becomes 78%. On the other hand, in case 1 of Example 1, the reaction of the first layer started from 415 ° C., but it did not reach the equilibrium temperature, but remained at 562 ° C. at the catalyst layer outlet, resulting in a conversion rate of 78%. It has become. In the second layer, although there is a difference in the reaction start temperature, both cases reach almost equilibrium within an appropriate range. Although there is a slight difference in the conversion rate, it has reached about 92%, and since the difference can be absorbed by the third layer and the fourth layer after passing through the absorption tower 12, there is almost a difference in the final conversion rate. Absent.

  On the other hand, in Example 2, the first layer starts the reaction at 440 ° C. In this case as well, the reaction reaches 585 ° C. and near equilibrium, but the conversion rate to the outlet of the first layer is 76%, which is 2% lower than in Example 1. This also affects the second and subsequent layers, resulting in a decrease in the final conversion rate.

  The temperature shown in this embodiment is not uniform because it is affected by gas conditions, catalyst amount, and catalyst activity. For example, in Case 1 of Example 1, the reaction did not reach equilibrium at the first layer inlet temperature of 415 ° C. because the reaction rate at the beginning of the reaction was low because the temperature was low, and generally the reaction at 1 to 2 ° C. It is often improved simply by increasing the starting temperature. However, when the reaction start temperature is higher than necessary as in Example 2, this leads to a decrease in the conversion rate.

From the results of Example 1 and Example 2, according to the operation method according to the above embodiment, by adjusting the heat recovery ratio of the two heat recovery facilities by adjusting the valve opening, without changing the total heat recovery amount, More economical factory operation. For example, the steam recovered by the waste heat boiler 3 is used for steam turbine power generation, and the high-temperature air recovered by the SO ₃ cooler 4 is used as a heat source for a copper concentrate dryer or a silicate mill to reduce heavy oil. In comparison between case 1 and case 2 of Example 1, case 1 is advantageous by about 3 million yen per month (estimated as unit price of electric power 8.2 yen / kWh, heavy oil 60 thousand yen / kL).

  In Example 2, the economy is further improved, but in this case, since the conversion rate is lowered, it can be selected if it is advantageous compared with the subsequent exhaust gas treatment cost. In any case, the adjustment of the heat recovery ratio can be arbitrarily adjusted between the case 1 of the first embodiment and the second embodiment in accordance with the economic environment such as factory conditions and fuel costs.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 1 Converter 2 Pre-converter 3 Waste heat boiler 4 SO ₃ Cooler 6-11 Heat exchanger 12, 14 Absorption tower 16 Main blower 17-24 Control valve 31, 32 Temperature sensor 40 Controller 100 Sulfuric acid factory

Claims (13)

A plurality of conversion catalyst layers sequentially supplied with SO ₂ -containing gas;
Of the plurality of conversion catalyst layers, a first heat recovery means for recovering heat from the preceding gas discharged from the preceding conversion catalyst layer;
A second heat recovery means for recovering heat from the latter stage gas discharged from the latter stage conversion catalyst layer among the plurality of stage conversion catalyst layers;
And a control means for controlling a heat recovery ratio of the first heat recovery means and the second heat recovery means.   2. The sulfuric acid plant operating apparatus according to claim 1, wherein the control unit controls the heat recovery ratio in accordance with a temperature of a gas after heat recovery by the first heat recovery unit. The control means controls the heat recovery ratio so that the amount of heat recovered by the first heat recovery device becomes 10% to 20% of the total amount of heat recovered from the SO ₂ -containing gas. The operation apparatus of a sulfuric acid factory according to claim 1 or 2, characterized by the above. The control means controls the heat recovery ratio so that the amount of heat recovered by the first heat recovery device becomes 12% to 15% of the total amount of heat recovered from the SO ₂ -containing gas. The operation apparatus of a sulfuric acid factory according to claim 1 or 2, characterized by the above. A pre-converter comprising a conversion catalyst layer;
A gas that has been converted by the pre-converter and is provided with a conversion catalyst layer; and
The pre-stage gas is a gas that has undergone conversion by the pre-converter,
The said latter stage gas is the gas which passed through the conversion by the said converter, The operating apparatus of the sulfuric acid factory as described in any one of Claims 1-4 characterized by the above-mentioned. The converter includes a plurality of stages of the conversion catalyst layer,
6. The sulfuric acid plant operation apparatus according to claim 5, wherein the latter stage gas is a gas discharged from the second and subsequent catalyst layers of the converter.   The said control means controls the said heat recovery ratio based on the temperature of the gas supplied to the catalyst layer after the 2nd step | paragraph of the said converter, The operating apparatus of the sulfuric acid factory of Claim 6 characterized by the above-mentioned.   The sulfuric acid factory operation device according to any one of claims 5 to 7, further comprising a flow rate adjusting unit that controls a gas flow rate passing through the pre-converter to 70% or less with respect to a total gas flow rate.   The control means controls the heat recovery ratio so that the temperature of the gas supplied to the converter becomes equal to or higher than the lower limit value of the temperature that reaches equilibrium after passing through the catalyst layer at the foremost stage of the converter. The sulfuric acid factory operation device according to any one of claims 5 to 8, wherein The first heat recovery means is at least one of a waste heat boiler and a steam superheater,
The sulfuric acid factory operating device according to any one of claims 1 to 9, wherein the second heat recovery means is an air heat exchanger. A first heat recovery step of recovering heat from the preceding stage gas that has passed through the previous stage conversion catalyst layer among the plurality of stage conversion catalyst layers to which the SO ₂ -containing gas is sequentially supplied;
A second heat recovery step of recovering heat from the latter stage gas through the latter stage conversion catalyst layer among the plurality of stage conversion catalyst layers;
And a control step for controlling a heat recovery ratio of the first heat recovery step and the second heat recovery step. In the sulfuric acid plant, according to claim 11 a method of operating sulfuric acid plant as claimed, characterized in that 90 to 100% of SO ₂ load.   The method for operating a sulfuric acid factory according to claim 11 or 12, wherein the sulfuric acid production capacity of the sulfuric acid factory is 1000 t / day to 3000 t / day.

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