KR102724284B1 - Exhaust gas treatment system and exhaust gas treatment method - Google Patents

Abstract

The present invention provides an exhaust gas treatment system capable of predicting in advance the time when the concentration of acid gas begins to increase due to fluctuations in the oxygen concentration linked to fluctuations in the concentration of acid gas in exhaust gas, and adding an appropriate amount of a treatment agent at an appropriate timing. The system comprises an exhaust gas analysis unit (131, 132) which is arranged on at least one of the upstream and downstream sides of an exhaust gas recovery unit (16) and analyzes at least the concentration of oxygen gas in exhaust gas, and a treatment agent addition management unit (13) which calculates the addition amount of a treatment agent necessary for the treatment of acid gas included in exhaust gas to be treated in an exhaust gas treatment unit (11) based on the fluctuation amount of the oxygen gas concentration analyzed by the exhaust gas analysis unit (132) and instructs the supply of the calculated addition amount of the treatment agent, and a treatment agent supply unit (14) which supplies the addition amount of the treatment agent instructed by the treatment agent addition management unit (13).

Description

Exhaust gas treatment system and exhaust gas treatment method

The present invention relates to an exhaust gas treatment system and an exhaust gas treatment method.

Conventionally, exhaust gas discharged from an incinerator is cooled in a temperature reducing tower, and then the exhaust gas is passed through a filtering dust collector to remove solids and acid gases from the exhaust gas, after which it is discharged into the atmosphere through a chimney.

However, acid gases cannot be completely removed simply by passing the exhaust gas through a filtering dust collector. Currently, many incineration plants in Japan employ a dry exhaust gas treatment method in which lime is continuously blown into the flue from the temperature-reducing tower to the filtering dust collector to neutralize and remove acid gases. For example, an exhaust gas treatment method and exhaust gas treatment device in which an agent is injected into a nonwoven fabric or other cloth of a filtering dust collector that purifies exhaust gas emitted from a gas generation source such as an incinerator to remove acid gases in the exhaust gas by neutralizing the agent are commonly used. However, the treatment of the exhaust gas is insufficient, and acid gases such as sulfur oxides are leaking. Therefore, the following methods have been proposed to remove acid gases in the exhaust gas.

Patent Document 1 discloses a method for treating exhaust gas from a waste incinerator, wherein, when a measured value of the concentration of acid gas in exhaust gas at the outlet side or the inlet side of a filtering type dust collector exceeds a predetermined value and the exceeding state continues for a predetermined period of time, a sodium-based agent in an amount set in response to the measured value is supplied to the inlet side of a filtering type dust collector. In addition, Patent Document 2 discloses an exhaust gas treatment device, which comprises an upstream-side acid gas concentration meter for measuring the concentration of acid gas in exhaust gas and a downstream-side acid gas concentration meter for measuring the concentration of acid gas in exhaust gas downstream of a dust collector, and supplies a powdered neutralizing agent to the exhaust gas between a reaction section and a dust collector to neutralize a residual portion of the acid gas. Patent Document 3 discloses a desulfurizing agent addition control method, which calculates a current control value based on a first difference, which is a difference between an N-hour moving average of the SOx concentration N hours ago and an N-hour moving average of the SOx concentration at the present time, and a control value used to calculate the amount of desulfurizing agent added N hours ago, and determines the amount of desulfurizing agent added based on the current control value.

However, since Patent Documents 1 to 3 all analyze sulfur oxides (SOx) in acid gas, and a considerable amount of time is required until the analysis results for sulfur oxides are available, even if the concentration of sulfur oxides in exhaust gas increases significantly, the amount of treatment agent required to treat the increased sulfur oxides cannot be added immediately due to the time lag until the analysis results are available, and as a result, sulfur oxides that have not been sufficiently treated may be emitted into the atmosphere. For this reason, it is necessary to add a treatment agent for treating sulfur oxides in an amount somewhat larger than the required amount, but adding a treatment agent in an amount larger than the required amount increases the amount of solids recovered, including fly ash and the like, because unreacted treatment agent is also included in solids separated and removed in the exhaust gas recovery section. This increased solids are not desirable because, when disposed of by landfill or the like, it is necessary to prepare additional space for the landfill.

Patent Document 1: Japanese Patent Publication No. 2019-070471 Patent Document 2: Japanese Patent Publication No. 2017-124348 Patent Document 3: Japanese Patent Publication No. 2017-176922

Accordingly, the present invention has been made in consideration of the above circumstances, and has as its object the provision of an exhaust gas treatment system and an exhaust gas treatment method capable of predicting in advance the time at which the concentration of acid gas begins to increase due to a change in the concentration of oxygen gas linked to the change in the concentration of acid gas in exhaust gas, and adding an appropriate amount of a treatment agent at an appropriate timing.

To solve the above problem, the gist of the present invention is as follows.

(1) An exhaust gas treatment system comprising an exhaust gas treatment unit for treating exhaust gas, an exhaust gas recovery unit for separating and removing solids from the exhaust gas treated in the exhaust gas treatment unit, a treatment agent storage unit for storing a treatment agent for treating the exhaust gas, an exhaust gas analysis unit arranged on at least one of the upstream and downstream sides of the exhaust gas recovery unit and for analyzing at least the concentration of oxygen gas in the exhaust gas, and a treatment agent addition management unit for calculating the amount of treatment agent required for treating acid gas included in the exhaust gas treated in the exhaust gas treatment unit based on the amount of change in the oxygen gas concentration analyzed by the exhaust gas analysis unit and instructing the supply of the calculated amount of treatment agent, and a treatment agent supply unit for supplying the treatment agent in the amount of addition instructed by the treatment agent addition management unit from the treatment agent storage unit to the exhaust gas treatment unit.

(2) An exhaust gas treatment system described in (1), wherein the exhaust gas analysis unit is positioned downstream of the exhaust gas recovery unit.

(3) An exhaust gas treatment system described in (1) or (2), wherein the treatment agent has the property of neutralizing acid gas in the exhaust gas.

(4) An exhaust gas treatment system described in any one of (1) to (3) wherein the acid gas is sulfur oxide gas.

(5) An exhaust gas treatment method, wherein the treatment agent addition management unit is provided on at least one of the upstream and downstream sides of an exhaust gas recovery unit that separates gases and solids contained in exhaust gas and recovers and removes the solids, and has an exhaust gas analysis unit that analyzes at least the concentration of oxygen gas in the exhaust gas, and calculates the amount of treatment agent required for treatment of acid gas contained in the exhaust gas to be treated in the exhaust gas treatment unit based on the amount of change in the concentration of oxygen gas analyzed by the exhaust gas analysis unit, instructs a treatment agent supply unit to supply the calculated amount of treatment agent added, and supplies the instructed amount of treatment agent added from a treatment agent storage unit to the exhaust gas treatment unit, thereby treating the acid gas contained in the exhaust gas.

By means of the exhaust gas treatment system and exhaust gas treatment method of the present invention, the concentration of sulfur oxides contained in exhaust gas emitted into the atmosphere can be stably suppressed to a low level without rapidly increasing, and also the amount of unreacted treatment agent in solid substances separated and removed in an exhaust gas recovery unit is reduced.

Figure 1 is a drawing showing the configuration of an exhaust gas treatment system that implements the exhaust gas treatment method of the present invention.
Figure 2 is a graph showing the trend of SO ₂ concentration, O ₂ concentration, and lime input amount when a treatment agent was added based on the analysis results of the concentration of SO ₂ contained in exhaust gas.
Figure 3 is a graph showing the trend of SO ₂ concentration, O ₂ concentration, and lime input amount when a treatment agent was added based on the analysis results of the concentration of O ₂ contained in exhaust gas.

Hereinafter, embodiments of the present invention will be described. The following description is an example of embodiments of the present invention and does not limit the scope of the patent claims.

(Exhaust gas treatment system)

An exhaust gas treatment system (1) according to the present embodiment comprises an exhaust gas treatment unit (11) for treating exhaust gas, an exhaust gas recovery unit (16) for separating and recovering solids from exhaust gas treated in the exhaust gas treatment unit (11), a treatment agent storage unit (12) for storing a treatment agent for treating exhaust gas, and an exhaust gas analysis unit (131, 132) arranged on at least one of the upstream and downstream sides of the exhaust gas recovery unit (16) for analyzing at least the concentration of oxygen gas (O ₂ ) in exhaust gas, and a treatment agent addition management unit (13) for calculating the amount of treatment agent required for treating acid gas included in exhaust gas treated in the exhaust gas treatment unit (11) based on the amount of change in the oxygen gas concentration analyzed in the exhaust gas analysis unit (131, 132) and instructing the supply of the calculated amount of treatment agent, and a treatment agent addition control unit (13) for controlling the addition of the treatment agent. An exhaust gas treatment system having a treatment agent supply unit (14) that supplies a treatment agent in an amount indicated by a management unit (13) from a treatment agent storage unit (12) to an exhaust gas treatment unit (11). In addition, an exhaust gas analysis unit (131, 132) that analyzes the concentration of oxygen gas in exhaust gas is arranged in the exhaust gas treatment system (1).

(Composition of exhaust gas treatment system)

Figure 1 is a drawing showing the configuration of an exhaust gas treatment system that implements the exhaust gas treatment method of the present invention. In addition, among the lines connecting each block in Figure 1, solid lines represent the flow of objects, and dashed lines represent the flow of information.

The exhaust gas treatment system (1) of the treatment agent according to the present embodiment is configured with an incinerator (F), an exhaust gas treatment unit (11), a treatment agent supply unit (1 4 ), a treatment agent storage unit (1 2 ), a treatment agent addition management unit (13) including an exhaust gas analysis unit (131, 132), and an exhaust gas recovery unit (16) as the center, and in addition, a flow meter (17) and a chimney (18) are installed. The configuration of the exhaust gas treatment system (1) will be described in detail below.

(incinerator)

Incinerator (F) refers to combustion facilities such as municipal waste incinerators, industrial waste incinerators, power boilers, carbonization furnaces, and private factories, for example. In general, exhaust gas emitted from municipal waste incinerators contains harmful acid gases such as hydrogen chloride (HCl), sulfur oxides (SOx), and nitrogen oxides (NOx), as well as solids (hereinafter referred to as “fly ash”), depending on the type of waste to be incinerated. Of these, sulfur oxides are the most abundant. Exhaust gas is not particularly limited in terms of its source or content, and refers to gases generated by the incineration of various types of waste. “Acid gas” refers to gases that are dissolved in a solution and exhibit acidity, and for example, refers to gases containing hydrogen chloride or sulfur oxides.

(Exhaust gas treatment unit)

The exhaust gas treatment unit (11) performs treatment by adding and adding a treatment agent to the exhaust gas. Since the exhaust gas is an acidic gas containing sulfur oxides, it is necessary to neutralize the acidic gas before discharging it into the atmosphere, thereby suppressing the emission of harmful gases into the environment. Therefore, in the exhaust gas treatment unit (11), a neutralizing agent is added as a treatment agent to the exhaust gas to neutralize it.

As a treatment agent (hereinafter sometimes referred to as a “neutralizing agent”), a neutralizing agent is used. This treatment agent can neutralize acid gases contained in exhaust gas by contacting it with the exhaust gas.

As the exhaust gas treatment unit (11), there is no particular limitation as long as it can cause a reaction by bringing exhaust gas into contact with a solid treatment agent, and for example, a part of a flue (gas path) etc. can be used as the exhaust gas treatment unit (11). Among these, a part of a transfer pipe etc. for transferring exhaust gas to an exhaust gas recovery unit (16) such as a bag filter on the downstream side may be used as the flue. In addition, the exhaust gas treatment unit (11) can also be composed of a closed container, various reaction containers, etc. additionally installed in the flue (gas path).

In addition, the acid gas contained in the exhaust gas does not need to be chemically neutralized in its entirety in the exhaust gas treatment unit (11), and may be neutralized in the downstream side (e.g., in the path from the exhaust gas treatment unit (11) to the exhaust gas recovery unit (16)) as the treatment agent is transported together with the exhaust gas. For example, when lime is used as the treatment agent, lime reacts slowly with acid gas, so neutralization can be performed as described above.

In addition, the treatment of exhaust gas can be carried out continuously. In addition, it can be carried out in a batch manner, for example, using a closed vessel or various reaction vessels for gas phase reaction. In either case, the amount of exhaust gas to be treated is not particularly limited, and can be appropriately designed by considering the amount of exhaust gas generated by incineration of waste, etc.

(processing agent storage)

The treatment agent storage unit (1 2 ) stores the treatment agent for treating exhaust gas. In the exhaust gas treatment system (1) of the present embodiment, the treatment agent stored in the treatment agent storage unit (1 2 ) is managed. The treatment agent storage unit (1 2 ) is not particularly limited as long as it can store the treatment agent, and for example, a storage tank or a silo can be used. The capacity and shape of the treatment agent storage unit (1 2 ) are not particularly limited, and can be appropriately designed in consideration of the installation space, the operation plan for exhaust gas treatment, the amount of exhaust gas treated, the frequency of exhaust gas treated, the frequency of ordering the treatment agent, etc.

(Treatment Agent Addition Management Department)

The treatment agent addition management unit (13) is provided with an exhaust gas analysis unit (131) and an exhaust gas analysis unit (132) which are arranged on either or both of the upstream and downstream sides of the exhaust gas treatment unit (11). The treatment agent addition management unit (13) analyzes exhaust gas by the exhaust gas analysis units (131, 132), calculates the addition amount of the treatment agent necessary for the treatment of the exhaust gas, and instructs the supply of the calculated addition amount of the treatment agent. In this way, the treatment agent addition management unit (13) changes the addition amount of the treatment agent in response to the change in the analysis value depending on the properties of the exhaust gas to be treated (e.g., the concentration and flow rate of acid gas), the size of the exhaust gas treatment unit (11), etc. In addition, the “upstream side” and the “downstream side” herein refer to the upstream and downstream in the flow of the exhaust gas.

In addition, an instruction regarding the amount of treatment agent to be added transmitted from the treatment agent addition management unit (13) is transmitted to a treatment agent supply unit (14), such as a fixed amount feeder installed upstream of the exhaust gas treatment unit (11), and the treatment agent supply unit (14) is operated based on the instruction to add a predetermined amount of treatment agent to the exhaust gas treatment unit (11).

It is preferable that the treatment agent addition management unit (13) be provided with an arithmetic circuit that calculates various values by using the stored values when each component, such as sulfur oxides, is reduced with respect to the number of times the exhaust gas is treated or the treatment time when a constant amount of treatment agent is added to a constant amount of exhaust gas (for example, constant flow rate, constant time, or one batch) when the exhaust gas is treated in the exhaust gas treatment unit (11). The control method for performing the arithmetic processing may include a method of analyzing acid gas in the exhaust gas and calculating the amount of treatment agent required to neutralize it (feedback control), or a method of calculating the amount of treatment agent required based on acid gas in the exhaust gas after the treatment (feedback control).

(Exhaust Gas Analysis Department)

The exhaust gas analysis unit (131, 132) analyzes the properties of exhaust gas before and after adding the treatment agent, respectively, and can analyze the concentration of hydrogen chloride (HCl), sulfur oxide (SOx), and nitrogen oxide (NOx) in the exhaust gas. In addition, the flow rate of exhaust gas can also be analyzed. The analysis values of the exhaust gas analysis unit (131, 132) are managed by the treatment agent addition management unit (13).

It is preferable that the exhaust gas analysis unit (131, 132) be installed downstream of the exhaust gas recovery unit (16). It may be installed upstream of the exhaust gas recovery unit (16), but since the upstream side of the exhaust gas recovery unit (16) contains a lot of fly ash, the exhaust gas from which this fly ash has been filtered and recovered is analyzed in the exhaust gas analysis unit (132), thereby improving the analysis precision of the exhaust gas. From this fact, the exhaust gas analysis unit (132) analyzes the oxygen gas concentration instead of the sulfur oxide concentration, and when the analysis results show that the oxygen gas concentration begins to decrease, a treatment agent is added in response to the oxygen gas concentration. The oxygen gas concentration analysis methods include the zirconia method, the magnetic method, the laser spectroscopy method, and the electrode method. Any of the methods can be used, but the zirconia method is preferably used.

In the zirconia method, porous platinum electrodes are attached to both sides of a zirconia element, heated, and when gases having different partial pressures of oxygen gas are brought into contact with each side, an oxygen concentration cell is generated. An electromotive force is generated between the two electrodes by the action of this cell, and the oxygen gas concentration can be analyzed. In addition, by comparing the analysis results obtained from the exhaust gas analysis unit (131) and the exhaust gas analysis unit (132) respectively arranged on the upstream and downstream sides of the exhaust gas treatment unit (11), the amount of treatment agent required for neutralizing the exhaust gas can be calculated more accurately.

In addition, in order to further increase the accuracy of calculating the amount of treatment agent used, the exhaust gas amount is analyzed by an exhaust gas flow meter (1 7 ). In addition, since the exhaust gas amount hardly changes before and after adding the treatment agent, the exhaust gas flow meter is arranged together with the exhaust gas analysis unit (132) in Fig. 1, but the position of the exhaust gas flow meter is not limited to this. By analyzing the exhaust gas amount, the absolute amount of acid gas contained in the exhaust gas can be calculated together with the analysis value of the acid gas concentration, so that the required mass of the treatment agent can be calculated with higher accuracy.

(Treatment agent supply section)

The treatment agent supply unit (14) supplies the treatment agent in the amount indicated by the treatment agent addition management unit (13) from the treatment agent supply unit (1 4 ) to the exhaust gas treatment unit (11).

The treatment agent supply unit (14) may be configured to supply a predetermined amount of treatment agent from the treatment agent storage unit (12) to the exhaust gas treatment unit (11), and is not particularly limited thereto, but may be configured as, for example, a quantitative feeder, a pump, or a powder feeder.

(processing agent)

The treatment agent has the property of neutralizing acid gases in exhaust gas. The treatment agent may be in liquid or powder (solid) form, but it is necessary to have a component that can be used to calculate the amount of addition by analyzing the exhaust gas.

As the treatment agent, there is no particular limitation, and for example, calcium hydroxide, calcium oxide, calcium carbonate, magnesium hydroxide, magnesium oxide, magnesium carbonate, calcium hydroxide-magnesium hydroxide, calcium oxide-magnesium oxide, calcium carbonate-magnesium carbonate, sodium hydroxide, sodium bicarbonate, sodium carbonate, etc. can be used. One type of the treatment agent may be used alone, or two or more types may be used in combination.

When using a powder-form treatment agent, the average particle diameter is preferably 1 µm or more, more preferably 2 µm or more, and even more preferably 5 µm or more. By setting the average particle diameter of the treatment agent to 1 µm or more, it is possible to prevent a pressure differential increase in the exhaust gas recovery section (16) on the downstream side, or to prevent an increase in the acid gas concentration in the exhaust gas due to a decrease in the recovery efficiency. In addition, the average particle diameter of the treatment agent is preferably 50 µm or less, more preferably 40 µm or less, and even more preferably 30 µm or less. By setting the average particle diameter of the treatment agent to 50 µm or less, it is possible to secure a treatment agent having a large specific surface area sufficient for the exhaust gas to come into contact with.

(Exhaust gas recovery unit)

The exhaust gas treatment system (1) installs an exhaust gas recovery unit (16), such as a bag filter, on the downstream side of the exhaust gas treatment unit (11). The exhaust gas recovery unit (16) removes fly ash, which is a solid substance contained in the exhaust gas. The fly ash removed here includes the unreacted treatment agent if some of the treatment agent added to the exhaust gas treatment unit (11) is not used in the neutralization reaction of the exhaust gas treatment and remains unreacted. In addition, sulfur oxides that have reacted with the treatment agent, unreacted hydrogen chloride (HCl), sulfur oxides (SOx), and nitrogen oxides (NOx) are also included. After a certain period of time, the fly ash collected in the exhaust gas recovery unit (16) is recovered and discharged to the outside.

(supply meter)

The treatment agent addition management unit (13) may be equipped with a supply amount measuring unit (not shown in the drawing) on the downstream side of the treatment agent supply unit (14) and on the upstream side of the exhaust gas treatment unit (11). The supply amount measuring unit measures the amount of treatment agent supplied from the treatment agent supply unit (14) to the exhaust gas treatment unit (11).

(Exhaust gas treatment method)

The exhaust gas treatment method according to the present embodiment comprises: a treatment agent addition management unit (13) having an exhaust gas analysis unit (131, 132) that is arranged at least on one of the upstream and downstream sides of an exhaust gas recovery unit (16) that separates gas and solids contained in exhaust gas and recovers and removes the solids; and, based on the amount of change in the oxygen gas concentration analyzed by the exhaust gas analysis unit (131, 132) of the treatment agent addition management unit (13), the amount of treatment agent required for the treatment of acid gas contained in the exhaust gas treated in the exhaust gas treatment unit (11) is calculated; supply of the calculated amount of treatment agent is instructed to the treatment agent supply unit (14); and the instructed amount of treatment agent is supplied from the treatment agent storage unit (12) to the exhaust gas treatment unit (11), thereby treating the acid gas contained in the exhaust gas.

(Operation of exhaust gas treatment system)

Here, the operation of the exhaust gas treatment method of the exhaust gas treatment system (1) is described.

When the exhaust gas is generated by incineration of waste in an incinerator (F), it is processed, for example, through the following path. The exhaust gas generated in the incinerator (F) is cooled by passing through a flue and a thermostatic tower (both not shown in the drawing), and fly ash is removed or recovered in an exhaust gas recovery unit (16). Thereafter, it is transferred to an exhaust gas analysis unit (132) of a treatment agent addition management unit (13) through the exhaust gas recovery unit (16). After the concentration of oxygen gas in the exhaust gas is analyzed in the exhaust gas analysis unit (132), an instruction is transmitted from the treatment agent addition management unit (13) to add an amount of treatment agent necessary for processing sulfur oxides contained in the exhaust gas in response to the amount of change in the oxygen gas concentration. In accordance with the instruction from the treatment agent addition management unit (13), sulfur oxides in the exhaust gas are neutralized in the exhaust gas treatment unit (11) with the treatment agent supplied from the treatment agent supply unit ( 14 ). After analyzing the oxygen gas concentration or sulfur oxide concentration, etc. in the exhaust gas analysis unit (132), and confirming that the sulfur oxide concentration of the exhaust gas is below the standard, it is discharged into the atmosphere through the chimney (18). In addition, the fly ash removed in the exhaust gas recovery unit (16) is further processed, such as fixing and removing heavy metals, etc., and landfilling.

(Behavior of oxygen gas concentration)

In this embodiment, the concentration of oxygen gas (O ₂ ) in the exhaust gas is analyzed in the exhaust gas analysis unit (132). In the past, treatment of acid gas in the exhaust gas using a treatment agent analyzed the concentration of acid gas, for example, sulfur oxide (SO _X ), in the exhaust gas, which is the target of neutralization. However, since it takes a considerable amount of time (e.g., 4 minutes or more) until the results come out from analyzing acid gas (e.g., sulfur oxides (SO _X )) in the exhaust gas analysis unit (132), even if an appropriate amount of treatment agent is added to the exhaust gas treatment unit to treat the exhaust gas based on the concentration of the acid gas as a result of the analysis, there is a possibility that the concentration of the acid gas contained in the exhaust gas to be treated may have changed at the time of adding the treatment agent, so it cannot be said that the amount of the added treatment agent is necessarily added without excess or deficiency, and since the concentration of the acid gas cannot be stably suppressed low, there have been cases where the acid gas temporarily fluctuates to a high concentration.

Accordingly, as a result of repeated examinations by the inventors of the present invention, they found that there is a correlation between the concentration of acid gas and the concentration of oxygen gas contained in exhaust gas, and that as the concentration of acid gas begins to increase, the concentration of oxygen gas begins to decrease. In addition, since the time from analysis of oxygen gas in exhaust gas to the time when the result is obtained is shorter than that of acid gas analysis (for example, approximately 2 minutes), it was predicted that when the concentration of oxygen gas in exhaust gas begins to decrease by analyzing the concentration of oxygen gas, the acid gas begins to increase, and as a result of immediately adding the necessary treatment agent to the exhaust gas treatment unit according to the rate of decrease in the concentration of oxygen gas, it was found that the concentration of acid gas can be stably suppressed to a low level without causing the concentration of acid gas to temporarily increase to a high level. From these facts, in the present invention, instead of using the analysis results of the concentration of sulfur oxides in exhaust gas, an appropriate amount of a treatment agent is added based on the analysis results of the concentration of oxygen gas in exhaust gas, and neutralization treatment of sulfur oxides in exhaust gas is performed at the point in time when the concentration of oxygen gas in exhaust gas begins to decrease, thereby stably suppressing the concentration of acid gas to a low level without the acid gas temporarily fluctuating in high concentration.

The correlation between oxygen gas concentration and sulfur oxide concentration varies depending on the characteristics of the exhaust gas treatment system device, the size of the device, the situation of the reaction in which exhaust gas is generated, etc. Therefore, by preparing a calibration curve that investigates the relationship between oxygen gas concentration and sulfur oxide concentration by each exhaust gas treatment system in advance and also considering the amount of exhaust gas, the amount of treatment agent required for treating acid gas contained in the exhaust gas can be determined.

(Analysis time of sulfur oxide concentration)

In addition, in the analysis of sulfur oxide concentration, the sulfur dioxide concentration was obtained by utilizing the light absorption in the infrared range of sulfur dioxide, which is the main component of sulfur oxide. Specifically, the infrared absorption amount of sulfur dioxide in the vicinity of 7.3 μm was analyzed, and the sulfur dioxide concentration contained in the exhaust gas was continuously analyzed. However, the current analysis of sulfur oxide requires several minutes, and at least 4 minutes in the current state, until the result is obtained, depending on the analysis principle. During that time, the exhaust gas flows from the incinerator (F) through the exhaust gas recovery section ( 16 ) to the chimney (18). Therefore, between the start of the analysis and the result being obtained, the exhaust gas without the treatment agent was flowing into the atmosphere.

(Analysis time of oxygen gas concentration)

Therefore, the exhaust gas treatment system (1) of the present embodiment does not analyze the concentration of sulfur oxides in the exhaust gas, but focuses on the oxygen gas in the exhaust gas and analyzes and measures the concentration of the oxygen gas. In the analysis and measurement method, an oxygen concentration meter using the zirconia method can be installed upstream or downstream of the exhaust gas analysis section (132) of the exhaust gas treatment system (1) for analysis. Usually, in the oxygen gas concentration analysis, the zirconia method can be used for analysis in just 2 minutes, so that analysis can be performed in a shorter period of time compared to the sulfur oxide concentration analysis. Accordingly, since the analysis time of the oxygen concentration meter can be performed in a short period of time after the exhaust gas reaches the exhaust gas analysis unit (132), even if it is downstream of the exhaust gas recovery unit (16), the oxygen gas concentration is analyzed to calculate the analysis value, and by giving instructions from the treatment agent addition management unit (13) to the treatment agent supply unit (1 4 ) in a short period of time, the treatment agent supply unit (1 4 ) supplies the treatment agent and performs the treatment in the exhaust gas treatment unit (11). As a result, the exhaust gas that is not neutralized by the treatment agent can be reduced, and the exhaust gas that is leaked into the atmosphere without being neutralized can be reduced.

(Utilizing changes in oxygen gas concentration)

As described above, by utilizing both the time required for analysis of the oxygen gas concentration and sulfur oxide concentration, which are analysis targets in the exhaust gas analysis unit (132), and the time difference appearing in the behavior of the change in the oxygen gas concentration and sulfur oxide concentration in the exhaust gas treatment system (1), the exhaust gas that is not neutralized by the treatment agent can be significantly reduced, thereby reducing the exhaust gas that leaks into the atmosphere without being neutralized. In this way, by minimizing the delay time that cannot respond to the neutralization treatment of sulfur oxides, it was possible to suppress the leakage of exhaust gas containing sulfur oxides from the chimney.

(Stepwise addition of treatment agent)

In addition, the mass of acid gas to be treated per hour was obtained from the exhaust gas amount and sulfur oxide concentration, and the amount of the treatment agent considering the neutralization reaction for a unit amount of sulfur oxide was added to obtain the required amount of the treatment agent. Then, the addition of the treatment agent to the exhaust gas was controlled by a feed forward control method or a feedback control method. Therefore, in the present embodiment, similar to the control method by analysis of sulfur oxide concentration up to now, the logic of controlling the addition amount of the treatment agent based on the numerical value of the change in the oxygen gas concentration analyzed by the exhaust gas analysis unit (132) is applied to the treatment agent addition management unit (13), thereby controlling the treatment of sulfur oxides.

However, the change in the oxygen gas concentration is more gradual than the sulfur oxide concentration. In addition, although the change in the oxygen gas concentration indicates the starting point of adding the treatment agent, the oxygen gas concentration and the sulfur oxide concentration do not completely correspond. Therefore, it is preferable not to completely correspond to the change in the oxygen gas concentration, but to vary the amount of the treatment agent added stepwise in response to the change in the oxygen gas concentration. For example, when the oxygen gas concentration decreases, rather than determining the amount of the treatment agent by the amount decreased, a large amount is added even when the treatment agent is added for the first time. The amount to be added stepwise is determined in relation to the oxygen gas concentration. Afterwards, when the tendency of the oxygen gas concentration to decrease decreases, the amount of the treatment agent added is greatly reduced to a small amount. By performing the stepwise treatment in this way, the neutralization treatment of sulfur oxides can be performed in response to the oxygen gas concentration in the exhaust gas treatment system (1).

(Exhaust gas analysis section on the upstream side)

In addition, the analysis value of the oxygen gas concentration is managed by the treatment agent addition management unit (13) as an analysis value obtained by the exhaust gas analysis unit (131) on the upstream side of the exhaust gas recovery unit (16), although the exhaust gas analysis unit (132) on the downstream side of the exhaust gas recovery unit (16) was used. The closer the treatment agent supply unit (1 4 ) and the location where the exhaust gas is analyzed in terms of distance and time, the more immediate the treatment agent addition to the exhaust gas is.

(Example)

Hereinafter, the present invention will be described in more detail based on examples. The present invention is not limited to these examples.

In order to neutralize sulfur oxides in exhaust gas and recover them in an exhaust gas recovery section, the amount of sulfur oxides is usually analyzed after the exhaust gas recovery section. In controlling sulfur oxides, the amount of treatment agent added is controlled by a feedback control method such as PID based on the sulfur analysis results. In most cases up to now, the sulfur oxide concentration has been analyzed downstream of the exhaust gas recovery section, and the treatment agent has been provided upstream of the exhaust gas recovery section based on the analysis results. In order to compare the influence of the analysis of oxygen gas concentration and sulfur oxide concentration on the downstream of the exhaust gas recovery section, the trend of sulfur oxide concentration and the consumption of slaked lime, which is a treatment agent, when each concentration analysis was performed were analyzed.

(Comparative Example 1)

As comparative example 1, in a factory equipped with the above-mentioned exhaust gas treatment system, exhaust gas treatment was performed by analyzing the sulfur oxide concentration using the same exhaust gas treatment method as before.

Here, regardless of the change in oxygen gas concentration, the change in sulfur oxide concentration was identified and the addition of the treatment agent was started. At this time, the trend of sulfur oxide concentration and treatment agent addition time is shown in Fig. 2. The analysis of sulfur oxide concentration is done by a sulfur oxide analyzer using an infrared method, and the response time from when the exhaust gas reaches the analyzer is several minutes, specifically, about 240 seconds until 90% response. On the other hand, the oxygen gas concentration can be analyzed in about 120 seconds until 90% response by the zirconia method.

In the exhaust gas treatment section of the exhaust gas treatment system shown in Fig. 1, exhaust gas was injected, and at the point where the concentration of sulfur dioxide ( _SO2 ), which is a sulfur oxide, began to increase as shown in Fig. ₂ , lime as a treatment agent was injected. However, at the position of the exhaust gas analysis section located downstream of the exhaust gas recovery section, the SO2 concentration began to increase rapidly. After about 1 to 2 minutes had passed, the _SO2 concentration reached a peak, after which the effect of the addition of the treatment agent began to appear and the _SO2 concentration decreased. From this fact, it can be seen that the addition of the treatment agent to the exhaust gas treatment section was not able to sufficiently treat the _SO2 concentration contained in the exhaust gas. When the exhaust gas mixed with the treatment agent reaches the exhaust gas analysis section, the exhaust gas containing a large amount of sulfur oxide that has not been treated with the treatment agent is emitted and leaked into the atmosphere through the chimney within 1 to 2 minutes.

(Example 1)

Next, the change in oxygen gas (O ₂ ) concentration was identified and the treatment agent was added. The trend of the O ₂ concentration and the amount of treatment agent at this time is shown in Figure 3.

In Example 1, after analyzing the concentration of SO ₂ and O ₂ contained in the exhaust gas in advance to create a calibration curve, a program was introduced to gradually vary the amount of treatment agent added as shown below, and a method of adopting a higher addition amount between the conventional control method and this program was used. Table 1 shows the relationship between the oxygen gas concentration (%) and the amount of lime added (kg/h).

As shown in Fig. 3, the treatment agent, slaked lime, was injected 1 minute after the exhaust gas was injected, when the oxygen concentration fell below 10%. However, in the exhaust gas analysis section located downstream of the exhaust gas recovery section, exhaust gas with a high sulfur oxide concentration was injected 2 minutes after the oxygen gas concentration decreased. Therefore, when the exhaust gas mixed with the treatment agent reaches the exhaust gas analysis section, the exhaust gas containing a lot of sulfur oxide that has not been neutralized is discharged to the outside. However, the addition of slaked lime is started about 1 minute before the sulfur oxide concentration increases. For this reason, the peak of the sulfur oxide concentration is much lower than in Comparative Example 1. In addition, by changing the addition amount of slaked lime in stages in response to the change in oxygen gas concentration, rather than continuously changing the addition amount of oxygen gas concentration, the consumption of slaked lime is somewhat large, but untreated sulfur oxides are not generated for sulfur oxides. This treatment shows that the emission and leakage to the outside of exhaust gas containing a lot of sulfur oxides to which the treatment agent has not been added is very small.

However, in Example 1, since the slaked lime is added earlier than in Comparative Example 1, it can be seen that the addition time is long and the amount of slaked lime added is large. From this, it can be seen that the neutralization treatment of sulfur oxides in the exhaust gas is sufficiently performed.

Also, as can be clearly seen from the lime shown in Figures 2 and 3, in an actual exhaust gas treatment system, a certain amount of treatment agent is always added regardless of the concentration of oxygen and sulfur oxides. Here, "addition of treatment agent" means from general addition to addition of a large amount of treatment agent.

1: Exhaust gas treatment system
11: Exhaust gas treatment unit
12: Treatment agent storage compartment
13: Treatment Agent Addition Management Department
131, 132: Exhaust Gas Analysis Section
14: Treatment agent supply section
16: Exhaust gas recovery unit
17: Exhaust gas flow meter
18 : Chimney
F: Incinerator

Claims (5)

An exhaust gas treatment unit for treating exhaust gas,
An exhaust gas recovery unit that separates and removes solids from the exhaust gas treated in the above exhaust gas treatment unit,
A treatment agent storage unit for storing a treatment agent for treating the above exhaust gas, and
An exhaust gas recovery unit is provided with an exhaust gas analysis unit that analyzes at least the concentration of oxygen gas in the exhaust gas, and, based on the amount of change in the concentration of oxygen gas analyzed by the exhaust gas analysis unit, calculates the amount of treatment agent required for treatment of acid gas included in the exhaust gas to be treated by the exhaust gas treatment unit, and a treatment agent addition management unit that instructs supply of the calculated amount of treatment agent;
A treatment agent supply unit that supplies the treatment agent in the amount indicated by the treatment agent addition management unit from the treatment agent storage unit to the exhaust gas treatment unit.
Equipped with exhaust gas treatment system.
In the first paragraph,
An exhaust gas treatment system in which the above exhaust gas analysis unit analyzes the oxygen gas concentration in the exhaust gas using an oxygen concentration meter using the zirconia method, the treatment agent addition management unit instructs the supply of the treatment agent when the oxygen gas concentration begins to decrease, and the exhaust gas treatment unit treats the exhaust gas containing the acid gas with the treatment agent .
In paragraph 1 or 2,
An exhaust gas treatment system in which the above treatment agent has the property of neutralizing acid gas in the exhaust gas.
In paragraph 1 or 2 ,
An exhaust gas treatment system wherein the above acidic gas contains sulfur oxide.
An exhaust gas treatment method, comprising: a treatment agent addition management unit disposed downstream of an exhaust gas recovery unit that separates gases and solids contained in exhaust gas and recovers and removes the solids, and having an exhaust gas analysis unit that at least analyzes the concentration of oxygen gas in the exhaust gas; calculating the addition amount of a treatment agent necessary for treating acid gas contained in the exhaust gas to be treated in the exhaust gas treatment unit based on the amount of change in the oxygen gas concentration analyzed by the exhaust gas analysis unit; instructing a treatment agent supply unit to supply the calculated addition amount of the treatment agent; and supplying the instructed addition amount of the treatment agent from a treatment agent storage unit to the exhaust gas treatment unit, thereby treating acid gas contained in the exhaust gas.

Images