WO2013008918A1

WO2013008918A1 - Method for treating acidic gas

Info

Publication number: WO2013008918A1
Application number: PCT/JP2012/067954
Authority: WO
Inventors: 益子　光博
Original assignee: 栗田工業株式会社
Priority date: 2011-07-14
Filing date: 2012-07-13
Publication date: 2013-01-17
Also published as: KR101528743B1; CN103648616B; TW201524584A; JP5720455B2; TW201306918A; MY163303A; JP2013022471A; KR20140036313A; TWI565514B; TWI608861B; CN103648616A

Abstract

The purpose of the present invention is to provide a method for treating an acidic gas according to a novel control scheme for performing a stable acidic gas treatment that rarely causes the acidic gas concentration at the outlet to peak and for reducing the excessive addition of alkali agents in a feedback format that does not require the introduction of a new, expensive acidic-gas measurement device. This method for treating an acidic gas involves adding an alkali agent to a combustion exhaust gas containing an acidic gas and feedback-controlling the amount of the alkali agent to be added on the basis of a measurement signal from an acidic gas concentration measurement device which measures the acidic gas concentration after dust collection, the method involving at least: a step of calculating a basal addition amount found by multiplying the average addition amount suitable for the average time (for example, 1 hour, as described later) by a factor of 1 or less (for example, 80%, as described later); and a step of calculating, through feedback computation, an output value for the amount of the alkali agent to be added on the basis of the calculated basal addition amount.

Description

Acid gas treatment method

The present invention relates to a method for treating acidic gases such as harmful hydrogen chloride and sulfur oxides generated in combustion facilities such as municipal waste waste incinerators, industrial waste incinerators, power generation boilers, carbonization furnaces, and private factories. Specifically, the present invention relates to a method for efficiently controlling the addition amount of an alkaline agent for treating acid gas.

Exhaust gas containing harmful hydrogen chloride and sulfur oxide is treated with an alkaline agent such as slaked lime or baking soda, and then removed by a dust collector such as a bag filter (BF) and then discharged from the chimney. On the other hand, the fly ash collected by the dust collector contains harmful heavy metals such as Pb and Cd, and is disposed of in landfill after stabilizing these harmful heavy metals.

Sodium bicarbonate finely processed to 5-30μm, which is an alkaline agent for treating acid gas, is more reactive than slaked lime, can process acid gas stably, has less unreacted content, and can reduce the amount of landfill disposal. This is an effective means for reducing the load. In addition, heavy metals are generally treated by insolubilization with a chelate such as diethyldithiocarbamate, and the effect of fixing heavy metals is high in the short term. The problem of re-elution of heavy metals such as lead due to decomposition remains. On the other hand, heavy metal fixation with phosphoric acid compounds such as phosphoric acid is a highly valuable treatment method from the viewpoint of environmental protection, because it changes to the form of hydroxyapatite, which is an inorganic mineral, and has excellent long-term stability at the final disposal site. . Further, the method of treating fly ash treated with fine powdered sodium bicarbonate with a heavy metal fixing agent such as phosphoric acid is an effective means having many environmental load reducing effects.

By the way, controlling the addition amount of alkaline agents such as slaked lime and baking soda that treat acidic gases such as hydrogen chloride and sulfur oxides not only reduces the cost of treating acidic gases, but also reduces the unreacted content of alkaline agents. The effect of reducing fly ash landfill disposal can be expected.

The amount of alkali agent added to treat acidic gases such as hydrogen chloride and sulfur oxide is generally based on the HCl concentration measured by an ion electrode type hydrogen chloride measuring device installed after the bag filter. Feedback control is performed by the PID control device. However, in a combustion facility such as an incineration facility, a device for measuring the concentration of acidic gas at the entrance is usually not installed, and PID control parameters are set and the control output is adjusted without knowing the state of fluctuation at the entrance. However, the PID control device has five setting items of P, I, D, additive amount (output) lower limit, and additive amount (output) upper limit, and the set value of each item is combined to determine the control output value. It takes a lot of time to study the addition control. For this reason, in general, the setting by the PID control apparatus has many facilities that perform control in which the amount of addition is greatly increased when the control target value (SV) is exceeded.

However, the control output of a normal PID control device can only set a single upper limit. For example, when the control target value (SV) of the HCl concentration is set to 40 ppm, the single upper limit of the control output at a concentration of 40 ppm or more. As a result, the alkali agent is added to the limit, causing excessive addition of the alkali agent. The feedback control is affected by measurement delay of the acid gas measuring device. The HCl concentration at the bag filter outlet is usually measured by an ion electrode method (for example, HL-36 manufactured by Kyoto Electronics Industry), and the sulfur oxide concentration is measured by an infrared absorption method (for example, NSA-3080 manufactured by Shimadzu Corporation). Including the sampling time of the exhaust gas and the response time of the measuring instrument, there is a huge measurement delay of 5 to 10 minutes. This measurement delay causes an addition lag of the alkaline agent, which leads to poor processing of the acid gas and causes excessive addition of the alkaline agent.

種々 Various control methods are being studied to solve this problem. Patent Document 1 proposes “P + PID control” in which P is further added to a normal PID control expression. This proposal is intended to cope with the sudden generation of acidic gas, which is difficult with normal PID control. In

Patent Documents

2 and 3, feedforward control for determining the addition amount of the alkaline agent based on the acidic gas concentration at the inlet, and the addition amount of the alkaline agent based on the acidic gas concentration after the alkaline agent has been processed. A control method that combines feedback control that compensates for this problem has been proposed. This control method is expected to have an effect of suppressing excessive addition of feedback control, and an effect of reducing acid gas stabilization and excessive addition of alkaline agent is obtained.

JP 2002-113327 A JP-A-10-165552 JP 2006-75758 A

However, in Patent Document 1, it is possible to cope suddenly with the entrance to some extent. However, since the upper limit value and the lower limit value of the control output are set to a single setting, hunting by a medicine is performed in a facility where the fluctuation of the acidic gas concentration at the entrance is severe. Therefore, it is difficult to perform stable treatment with a small peak of outlet acid gas concentration. In addition, the measurement delay of the measuring device is not taken into account, and it is not possible to cope with the processing failure of the acid gas due to the addition lag of the alkaline agent due to the measurement delay. Furthermore, in

Patent Documents

2 and 3, in the combustion facilities such as incineration facilities, most of the facilities measure only the acid gas concentration at the outlet, and in order to implement this control method, the acid gas at the inlet is occupied. It is necessary to introduce a new and expensive acid gas measuring device for measuring the concentration.

In consideration of the above-described conventional technology, the present invention provides a stable acidic gas treatment with little generation of acidic gas concentration at the outlet and an excess of alkaline agent in a feedback type that does not require the introduction of a new expensive acidic gas measuring device. An object of the present invention is to provide an acid gas treatment method by a new control method for reducing the addition.

(1) Addition of alkaline agent to combustion exhaust gas containing acidic gas and feedback control of addition amount of alkaline agent based on measurement signal of acidic gas concentration measuring instrument that measures acidic gas concentration after collecting dust A method for treating an acidic gas, which is a factor of 1 or less in average addition amount according to at least an average time (for example, 5 minutes, 15 minutes, 30 minutes, 1 hour, 3 hours, 6 hours, etc. described later) The basic addition amount multiplied by 95%, 90%, 80%, 70%, 50%, etc., which will be described later), and the addition output value of the alkaline agent based on the calculated basic addition amount is feedback-calculated. The process of calculating by this, The processing method of the acidic gas which has.

現状 PID control, which is mainly used at present, can set only a single upper limit and lower limit for the additive output. Therefore, for example, when the control target value (SV) of the outlet HCl concentration is set to 40 ppm, when the actual outlet HCl concentration is 40 ppm or less, it is added at the lower limit of the control output in order to reduce the addition of the alkaline agent, and the control target value (SV) ) At 40 ppm or more, the concentration of HCl at the outlet fluctuates greatly due to inappropriate addition (excessive addition, insufficient addition) of the alkaline agent that repeats addition at the upper limit of the control output to increase the addition of the alkaline agent. Causes excessive addition.

On the other hand, as in the invention of (1), the basic addition amount is calculated by multiplying the average addition amount corresponding to at least the average time by a factor of 1 or less, and the addition of the alkaline agent is performed based on the calculated basic addition amount. When the amount output value is calculated by a feedback calculation, it is possible to prevent an inappropriate addition of an alkaline agent and to perform a stable treatment with a small fluctuation in the outlet HCl concentration to be treated, and as a result of the proper addition according to the invention of (1), The amount of alkali agent added can also be reduced.

The invention of (1) pays attention to the past average addition amount as a factor related to the HCl concentration at the inlet, which could not be considered in the conventional feedback control, and the basic addition amount obtained by multiplying the past average addition amount by a factor of 1 or less. It is characterized by being used as a control factor. As a result, the basic addition amount obtained by multiplying the past average addition amount that is reasonable as the basis of the addition amount by a factor of 1 or less without adding an alkali agent that greatly fluctuates the lower limit and upper limit repeatedly as in the past. The amount of alkali agent added to the base is calculated by feedback control such as PID. Therefore, the variation in the addition of the alkali agent is reduced, the hunting caused by the poor addition of the alkali agent itself (excessive addition, insufficient addition) is suppressed, and the addition amount can be reduced by appropriate addition, and the acidity with little fluctuation Gas stable treatment becomes possible.

(2) In the step of calculating the addition amount output value by a feedback calculation, the calculated basic addition amount is set as a lower limit value of the alkali agent addition amount output value (for example, LO: addition amount lower limit described later) (1) The processing method of the acidic gas as described in).

According to the invention of (2), since the basic addition amount is set as the lower limit value of the addition amount output value, the excess or deficiency of the addition amount is adjusted by the conventional feedback calculation based on the basic addition amount. The addition of the agent is optimized and the acid gas can be treated efficiently.

Further, the average time of the average addition amount is not particularly limited, but it is effective to use an average value such as a moving average of the addition amount, and the average time is preferably 5 minutes or more and preferably 15 to 24 hours. . Moreover, the coefficient prescribed | regulated with a basic addition amount has good 1 times or less. When a coefficient of 1 or more is used, the acid gas can be stably treated, but it is excessively added to prevent a decrease in the addition amount accompanying a decrease in the inlet acid gas concentration. The basic addition amount may be 1 or less of the average addition amount (coefficient 100% or less), but particularly 0.5 to 0.95 times (50 to 95%), particularly 0.7 to 0.9 times. (70 to 90%) is preferred.

(3) The step of calculating the added amount output value by feedback calculation is performed in the range of at least two acid gas concentration gradients (for example, the 6-second average of the latest HCl concentration gradient described later is a positive range and a negative range). A control target value of acid gas concentration (for example, 180 ppm, 220 ppm, etc. in Example 8 described later) for each of the at least two slope ranges, and at least the measurement signal and the A step of calculating an addition amount output value of an alkaline agent based on a control target value for each inclination range, and the step of setting the control target value has a large inclination range of the acidic gas concentration The control target value to be set (for example, when the 6-second average of the slope of the latest HCl concentration described later is positive (when the acid gas concentration is increased)) is the acid gas concentration (1) or (2), which is smaller than the control target value set when the slope range is small (for example, when the 6-second average of the latest HCl concentration slope to be described later is negative (when the acid gas concentration is lowered)) The processing method of the acidic gas of description.

According to the invention of (3), when the inclination range of the acid gas concentration at the bag filter outlet is large (when the acid gas concentration is increased), the acidic gas is smaller than when the inclination range is small (when the acid gas concentration is decreasing). Since the control target value of the concentration is reduced, the alkaline agent addition amount output value when the acid gas concentration is increased can be made larger than when the acid gas concentration is decreased. Therefore, the timing of adding the alkaline agent when the acid gas concentration is increased can be made faster than the current control, and the acid gas processing failure due to the measurement delay of the acid gas measuring device can be improved.
Conversely, since the amount of alkali agent added when the acid gas concentration decreases can be reduced compared to when the acid gas concentration increases, the amount of alkali agent added can be quickly reduced when the acid gas concentration decreases. Excessive addition due to measurement delay can be reduced.

(4) The step of calculating the added amount output value by feedback calculation includes the lower limit value of the added amount output value calculated based on the measurement signal (for example, LO in FIGS. 12, 15, and 41 described later) Between the upper limit value (for example, LH [control output upper limit] in FIGS. 12, 15, and 41 described later), the acid gas concentration (for example, the BF outlet HCl concentration in FIGS. 12, 15, and 41 described later). ) And setting one or more new upper limit values (for example, LM1 [output limit 1] and LM2 [output limit 2] in FIG. 12, FIG. 15, and FIG. 41, which will be described later)). The processing method of the acidic gas in any one of (1) to (3) which has further.

There is only one output upper limit in normal feedback calculation. When the acid gas concentration exceeds the control target value, the alkaline agent can be added up to the upper limit value regardless of the magnitude of the acid gas concentration at the inlet, causing excessive addition.
On the other hand, according to the invention of (4), the restriction of the control output according to the current acid gas concentration is added between the lower limit value and the upper limit value of the addition amount output value, thereby increasing the acid gas concentration. Accordingly, it is possible to appropriately add an alkali agent, and it is possible to reduce the amount of addition.

(5) In the step of calculating the basic addition amount, the basic addition amount is 0.5 to 0.95 times the average addition amount when the moving average time is 5 minutes or more (1) to (4) The processing method of the acidic gas in any one of.

As described above, the average time of the average addition amount is not particularly limited, but it is effective to use an average value such as a moving average of the addition amount, and the average time is 5 minutes or more and is used in about 15 to 24 hours. Is preferred. Moreover, the coefficient prescribed | regulated with a basic addition amount has good 1 times or less. When a coefficient of 1 or more is used, the acid gas can be stably treated, but it is excessively added to prevent a decrease in the addition amount accompanying a decrease in the inlet acid gas concentration. The basic addition amount may be 1 or less of the average addition amount (coefficient 100% or less), but particularly 0.5 to 0.95 times (50 to 95%), particularly 0.7 to 0.9 times. (70 to 90%) is preferred.
Therefore, according to the invention of (5), the acid gas can be stabilized and the excessive addition of the alkaline agent can be prevented.

(6) The step of calculating the added amount output value by feedback calculation is performed by using both the control output calculated from the hydrogen chloride concentration and the control output calculated from the sulfur oxide concentration in addition to the feedback calculation. The processing method of the acidic gas in any one of (1) to (5) which further has the process of calculating the addition amount output value of an agent.

In combustion facilities of industrial waste incinerators and private factories, hydrogen chloride and sulfur oxides are often generated at high concentrations. In this case, both hydrogen chloride and sulfur oxide are treated, and the control output and sulfur oxide concentration obtained based on the hydrogen chloride concentration of the hydrogen chloride concentration measuring device provided at the back of the bag filter are also included. For example, both the hydrogen chloride and sulfur oxide acidic gases can be treated stably by adding the control outputs obtained in the above.
Therefore, according to the invention of (6), both acidic gases of hydrogen chloride and sulfur oxide can be treated stably.

(7) The step of calculating the added amount output value by a feedback calculation includes:
In addition to the feedback calculation, the acidic gas according to any one of (1) to (6), further including a step of calculating an output value of the addition amount of the alkaline agent based on an average value of the hydrogen chloride concentration and / or the sulfur oxide concentration Processing method.

By the way, there are facilities that manage the discharge concentration of acid gas by the average value of each acid gas concentration (hydrogen chloride concentration, sulfur oxide concentration) for one hour. In general, control is performed by providing a control target value (SV). However, the control target value is merely a target, and there are many cases where the density exceeds the target value as a result of the control. In particular, since the reduction of the addition amount and the acid gas stabilization treatment are contradictory ideas, the risk that the one-hour average value exceeds the control value is increased only by obtaining the reduction of the addition amount. In this case, when the acid gas concentration reaches or exceeds the average control value for one hour, a large amount of alkaline agent (a certain amount added) is added to reduce the addition amount and stabilize the acid gas. It is possible to perform control with a high degree of security that can achieve both processing.
Therefore, according to the invention of (7), since the addition amount output value of the alkaline agent is calculated based on the average value of the hydrogen chloride concentration and / or the sulfur oxide concentration, both the reduction of the addition amount and the stable treatment of the acidic gas can be achieved. Highly reliable control is possible.

(8) The method for treating acidic gas according to any one of (1) to (7), wherein the alkaline agent is fine powder sodium bicarbonate having an average particle size of 5 to 30 μm.

The alkali agent used in the present invention is not particularly limited. In particular, fine powder baking soda adjusted to an average particle size of 5 to 30 μm, which has a fast reaction with acid gas, has good control responsiveness and can effectively exhibit the performance of the control method of the present invention. Slaked lime is also applicable. In this case, JIS special slaked lime is applicable, but the use of high specific surface area slaked lime with a high specific surface area of, for example, 30 m ² / g or more, which is highly reactive with acid gas, demonstrates the performance of the present invention. it can.

(9) The acid gas treatment method according to (8), wherein another alkaline agent different from the fine powdered baking soda is used in combination.

There is no particular limitation on the alkali agent that exhibits the effect of the present invention. Examples of the alkaline agent other than fine powdered sodium bicarbonate include slaked lime, sodium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium sesquicarbonate, natural soda, sodium hydroxide, potassium hydroxide, magnesium oxide, magnesium hydroxide and the like. When the alkaline agent is a powder, a fine powder having a particle size of less than 30 μm, particularly 5 to 20 μm, which is highly reactive with acidic gas, is preferred. An agent whose particle size is adjusted in advance may be applied, or a pulverization facility may be provided on site, and an alkaline agent having a coarse particle size may be added while being crushed on site. Further, the present invention can also be carried out with a slurry or an aqueous solution in which each alkaline agent is dissolved in water.

(10) The other alkaline agent is at least one alkaline agent selected from the group consisting of slaked lime, sodium hydroxide, magnesium hydroxide, magnesium oxide, sodium carbonate, sodium sesquicarbonate, natural soda, and crude sodium bicarbonate. (9) The processing method of the acidic gas as described in.

It is also economically effective to use an inexpensive alkaline agent different from the alkaline agent that performs the control according to the present invention. Although there is no restriction | limiting in the alkaline agent used together, As a cheap alkaline agent generally used, slaked lime, sodium hydroxide, magnesium hydroxide, magnesium oxide, sodium carbonate, sodium sesquicarbonate, natural soda, crude sodium bicarbonate can be illustrated. .

According to the present invention, in a feedback system that does not require the introduction of a new expensive acid gas measuring device, a stable acid gas treatment with less peak acid gas concentration at the outlet is performed and an excessive addition of an alkaline agent is reduced. It becomes possible to provide the acid gas processing method by a new control system.

It is a block diagram showing the structure of the acidic gas processing system 1 which adds fine powder baking soda to HCl which is waste gas in incineration facilities. It is a basic block diagram of a simulation reaction system. It is a graph which shows the relationship between fine powder baking soda addition equivalent and HCl removal rate in exhaust gas reaction. It is a graph which shows the relationship between fine powder baking soda addition equivalent and HCl removal rate in reaction on a bag filter. It is a graph which shows the behavior of inlet HCl concentration. It is a graph which shows the behavior of the fine powder baking soda addition amount of an actual machine examination result, and an exit HCl density | concentration. It is a graph which shows the behavior of the fine powder baking soda addition amount and exit HCl concentration of a simulation examination result. It is a table | surface which shows the comparative example of a simulation examination result, and the alkaline agent addition amount etc. for every Example. It is a graph which shows the behavior of inlet HCl concentration. It is a graph which shows the behavior of the addition amount of fine powder sodium bicarbonate and the outlet HCl concentration in Comparative Example 1. It is a graph which shows the behavior of the fine powder sodium bicarbonate addition amount in Example 1, and an exit HCl concentration. It is a table | surface of the control setting of the step control system in the comparative example 2, Examples 2 and 20. It is a graph which shows the behavior of the addition amount of fine powder sodium bicarbonate and the outlet HCl concentration in Comparative Example 2. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount and exit HCl concentration in Example 2. It is a table | surface of the control setting of the step control system in the comparative example 3, Example 3, 9, 10, 11, 17, 18, 21, and 22. FIG. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount, the inlet HCl concentration, and the outlet HCl concentration in Comparative Example 3. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount in Example 3, and outlet HCl concentration. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount in Example 4, and exit HCl concentration. It is a graph which shows the behavior of fine powder baking soda addition amount and exit HCl concentration in Example 5. It is a graph which shows the behavior of the fine powder sodium bicarbonate addition amount in Example 6, and exit HCl concentration. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount in Example 7, and the exit HCl concentration. It is a graph which shows the behavior of the fine powder sodium bicarbonate addition amount in Example 8, and an exit HCl density | concentration. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount in Example 9, and an exit HCl concentration. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount and exit HCl concentration in Example 10. It is a graph which shows the behavior of the fine powder baking soda addition amount in Example 11, and an exit HCl density | concentration. It is a graph which shows the behavior of the fine powder sodium bicarbonate addition amount in Example 12, and an exit HCl density | concentration. It is a graph which shows the behavior of fine powder baking soda addition amount and exit HCl concentration in Example 13. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount and exit HCl concentration in Example 14. It is a graph which shows the behavior of the addition amount of fine powder sodium bicarbonate and the outlet HCl concentration in Example 15. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount and exit HCl concentration in Example 16. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount in Example 17, and the exit HCl concentration. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount and exit HCl concentration in Example 18. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount, the inlet HCl concentration, and the outlet HCl concentration in Comparative Example 4. It is a graph which shows the behavior of the fine powder sodium bicarbonate addition amount in Example 19, and an exit HCl density | concentration. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount, inlet HCl concentration, and outlet HCl concentration in Example 20. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount, inlet HCl concentration, and outlet HCl concentration in Example 21. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount, the inlet HCl concentration, and the outlet HCl concentration in Example 22. It is a block diagram showing the structure of the acidic gas processing system 2 which adds fine powder baking soda to HCl which is waste gas in incineration facilities. It is a table | surface which shows the alkaline agent addition amount etc. for every comparative example of an actual machine examination result, and an Example. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount, the inlet HCl concentration, and the outlet HCl concentration in Comparative Example 5. It is a table | surface of the control setting of the step control system in the comparative example 6 and Examples 23 and 24. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount, the inlet HCl concentration, and the outlet HCl concentration in Comparative Example 6. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount, inlet HCl concentration, and outlet HCl concentration in Example 23. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount, inlet HCl concentration, and outlet HCl concentration in Example 24.

Hereinafter, the present invention will be described more specifically with reference to embodiments, but the present invention is not limited thereto.

FIG. 1 is a block diagram showing the configuration of an acid gas treatment system 1 in which fine powdered baking soda is added to HCl that is exhaust gas in an incineration facility.

The acid gas processing system 1 includes a control device 11, a fine powder baking soda addition device 12, a bag filter 13, and an HCl concentration measuring device 14. The control device 11 feedback-controls the added amount output value of the fine baking soda based on the HCl concentration measurement signal transmitted from the HCl concentration measuring device 14 and the basic addition amount calculated from the past average addition amount (PID control method or Step method). The fine powdered sodium bicarbonate adding device 12 adds the fine powdered sodium bicarbonate to the HCl in the exhaust gas based on the added amount output value of the fine powdered sodium bicarbonate calculated by the control device 11.
The basic addition amount is calculated by multiplying the past average addition amount according to the average time (for example, moving average time) by a factor of 1 or less.

The bag filter 13 removes dust after the reaction between HCl and fine baking soda in the exhaust gas. The HCl concentration measuring device 14 is configured so that fine powdered baking soda accumulated on the bag filter 13 (fine powdered baking soda remaining by reaction with HCl in the exhaust gas is accumulated on the bag filter 13) and HCl after the exhaust gas reaction have reacted. HCl concentration (bug filter outlet HCl concentration described later) is measured, and an HCl concentration measurement signal is transmitted to the control device 11.

The acidic gas treatment system 1 repeats such a cycle and performs feedback control, so that the control device 11 performs control to make the control output value of the added amount of fine powder sodium bicarbonate appropriate.
The HCl concentration measuring device 14 is, for example, an ion electrode type HCl concentration measuring device.

Further, as shown in FIG. 1, an HCl concentration measuring device is used to measure the HCl concentration (bag filter outlet HCl concentration described later) after the fine powdered baking soda accumulated on the bag filter 13 reacts with HCl after the exhaust gas reaction. 14 is preferably installed. This is because fine powdered sodium bicarbonate remaining due to the reaction with HCl in the exhaust gas is accumulated on the bag filter 13, and this accumulated fine powdered sodium bicarbonate reacts with HCl after the exhaust gas reaction, so the HCl concentration can be measured more accurately. Because.

Further, the control device 11 performs feedback control with the calculated basic addition amount as the lower limit value of the addition amount output value of the fine powdered sodium bicarbonate (for example, LO: addition amount lower limit described later).
Accordingly, since the excess or deficiency of the addition amount is adjusted by the conventional feedback calculation based on this basic addition amount, the addition of the alkaline agent is optimized and the acidic gas can be processed efficiently.

Furthermore, the control device 11 provides two ranges where the slope of HCl concentration (concentration change rate with time) is positive and negative. Then, a control target value of HCl concentration is set for each of these two ranges.

Here, the control target value of the HCl concentration may be set so that the control target value provided for the positive range of the HCl concentration is smaller than the control target value for the negative range. By doing in this way, the amount of fine sodium bicarbonate added when the HCl concentration is increased can be increased more than when the HCl concentration is decreased. Conversely, the amount of fine powdered sodium bicarbonate added when the HCl concentration is lowered can be made smaller than that when the HCl concentration is raised. Therefore, the addition output of the fine baking soda by the feedback calculation can be implemented ahead of schedule, and the influence of the measurement delay can be further reduced.

Furthermore, the control device 11 may perform feedback control by a step method. Here, the step method is a control method in which a control output corresponding to the HCl concentration is set stepwise. Specifically, in addition to the upper limit value of the control output value set in the PID control method, a new upper limit value of the control output value is set corresponding to the HCl concentration.

Here, there is only one output upper limit in normal PID control, and when the acid gas exceeds the control target value, the alkaline agent can be added up to the upper limit value regardless of the magnitude of the acid gas concentration, causing excessive addition. Therefore, by adopting a step control method, a new control output upper limit value corresponding to the current HCl concentration is added between the lower limit value and the upper limit value of the addition amount output value, thereby increasing the HCl concentration. Accordingly, it is possible to appropriately add fine powdered baking soda, and it is possible to suppress excessive addition of the added amount.

Further, new control output upper limit values (for example, LM1 [output limit 1] and LM2 [output limit 2] in FIGS. 12, 15, and 41 described later) are set corresponding to the HCl concentration. Is higher, the new control output upper limit value is also set higher. However, in order to suppress the excessive addition of the alkaline agent, the upper limit value of the control output value set in the PID control method (for example, LH [control output upper limit] in FIGS. 12, 15, and 41 described later). A small value is preferable.

The acid gas measuring device used in this embodiment can be implemented regardless of the measurement method. The hydrogen chloride concentration can be measured by an ion electrode method, single absorption line absorption spectroscopy using a laser, or the like, and sulfur oxide can be measured by an infrared absorption method, an ultraviolet fluorescence method, or the like. In the present embodiment, the effect of the present invention can be obtained regardless of the measurement delay speed because an improvement effect can be obtained by utilizing a reasonable basic addition amount that has not been taken into account in the conventional feedback control.

Industrial combustion incinerators and combustion facilities in private factories often generate hydrogen chloride and sulfur oxides at high concentrations. At this time, both hydrogen chloride and sulfur oxide are treated, and the control output and sulfur oxidation determined in the above control method based on the hydrogen chloride concentration of the hydrogen chloride concentration measuring device provided at the back of the bag filter. By adding, for example, the control outputs obtained in the control method based on the substance concentration, both acidic gases of hydrogen chloride and sulfur oxide can be treated stably.

In addition, there are facilities that manage the discharge concentration of acid gas with the average value of each acid gas concentration (hydrogen chloride, sulfur oxide concentration) for one hour. In general, control is performed by providing a control target value (SV). However, the control target value is merely a target, and there are many cases where the density exceeds the target value as a result of the control. In particular, since the reduction of the addition amount and the acid gas stabilization treatment are contradictory ideas, the risk that the one-hour average value exceeds the control value is increased only by obtaining the reduction of the addition amount. In this case, when the concentration reaches or exceeds the average control value for 1 hour, the addition of a large amount of alkaline agent (predetermined constant addition amount) ensures both reduction of the addition amount and stable treatment of acid gas. High degree of control is possible.

The alkali agent used in the present embodiment is not particularly limited. In particular, fine powder baking soda having an average particle diameter of 5 to 30 μm, which reacts quickly with acid gas, has good control responsiveness and can effectively demonstrate the performance of this control method. In addition, slaked lime can be JIS special slaked lime, but the use of high specific surface area slaked lime having a high specific surface area of, for example, 30 m ² / g or more, which is highly reactive with acidic gas, improves the performance of the present invention. Can demonstrate. Examples of the alkali agent other than the above include sodium carbonate, potassium hydrogen carbonate, potassium carbonate, sodium sesquicarbonate, natural soda, sodium hydroxide, potassium hydroxide, magnesium oxide, magnesium hydroxide and the like.

Further, when the alkaline agent is powder, fine powder having a particle size of less than 30 μm, particularly 5 to 20 μm, which is highly reactive with acidic gas, is preferred. An agent whose particle size is adjusted in advance may be applied, or a pulverization facility may be provided on site, and an alkaline agent having a coarse particle size may be added while being crushed on site. Further, the present invention can also be carried out with a slurry or an aqueous solution in which each alkaline agent is dissolved in water.

Furthermore, it is economically effective to use an inexpensive alkaline agent different from the alkaline agent that performs the control according to the present embodiment. Although there is no restriction | limiting in the alkaline agent used together, As a cheap alkaline agent generally used, slaked lime, sodium hydroxide, magnesium hydroxide, magnesium oxide, sodium carbonate, sodium sesquicarbonate, natural soda, crude sodium bicarbonate can be illustrated. .

Explanation of simulation reaction system.

[Simulation reaction system]: Combined reaction between exhaust gas and bag filter The simulation reaction system is a reaction in which the reaction between fine baking soda and hydrogen chloride (HCL) occurs instantaneously in the exhaust gas, and unreacted fine powder accumulated on the bag filter. It consisted of two reaction of baking soda and HCL (refer FIG. 2). Moreover, the residence time of the collected matter in the bag filter is usually about 2 hours. Therefore, in this simulation, the fine powdered baking soda on the bag filter is assumed to disappear in a specified time (set in about 2 hours).

The basic configuration of the simulation reaction system will be described with reference to FIG.
First, in the chemical injection control in an incineration facility, the amount of added chemical (fine powdered baking soda) is calculated by the calculation of a control expression such as PID based on the HCl concentration (after treatment) signal of the ion electrode type HCl concentration measuring device installed at the bag filter outlet. (Addition amount (Ag)) is determined (the following formula (1)), and the determined addition amount of fine baking soda (acid gas treating agent) is added to the exhaust gas (inlet HCl concentration (Hi)). Fine powder baking soda added to the flue reacts with acidic gas such as HCl in the exhaust gas, and the HCl in the exhaust gas is removed.

Ag = Ag1 + LO (1)
Ag: Fine powder baking soda addition amount [kg / h]
Ag1: Addition amount [kg / h] defined from the output of the HCl concentration measuring instrument (in the case of the step method, see FIGS. 12, 15, and 41)
LO: Lower limit of addition amount [kg / h]
In normal times (when the basic addition amount according to the present invention is not applied), a preset LO is used.
When applying the basic addition amount according to the present invention, the output is calculated using LO as a basic addition amount obtained by multiplying the moving average addition amount for a specified time by a predetermined coefficient.

In addition, the HCl removal rate at the inlet HCl concentration with fine powdered sodium bicarbonate is based on the application knowledge of our fine powdered sodium bicarbonate, the relationship between the exhaust gas reaction fine powder sodium bicarbonate addition equivalent (Jg) and the exhaust gas reaction HCl removal rate (αg) (Figure 3) and on the bag filter It was estimated from the relationship (FIG. 4) between the reaction fine powder baking soda addition equivalent (Js) and the reaction HCl removal rate (αs) on the bag filter. The reaction between HCl and fine baking soda was instantaneous. First, the HCl concentration (Hg) after the reaction in the exhaust gas is derived from the fine powdered sodium bicarbonate addition equivalent (Jg) of the exhaust gas reaction and the exhaust gas reaction HCl removal rate (αg) (the following formula (2)). In addition, the fine powder baking soda addition equivalent (Jg) of exhaust gas reaction is computed by following formula (3).

Hg = Hi × (1−αg ÷ 100) (2)
Hi: Inlet HCl concentration (ppm)
Hg: HCl concentration after exhaust gas reaction (ppm)
αg: HCl removal rate in exhaust gas reaction (%)
[Set from the relationship between the exhaust gas reaction fine powder baking soda addition equivalent and HCl removal rate (Fig. 3)]

Jg = Ag ÷ {Hi ÷ 0.614 ÷ 1000 ÷ M1 × M2 × F ÷ 1000} (3)
Jg: Exhaust gas reaction fine powder baking soda addition equivalent Ag: Fine powder sodium bicarbonate addition amount (kg / h)
Hi: Inlet HCl concentration (ppm)
M1: HCl molecular weight [set at 36.5]
M2: Sodium bicarbonate molecular weight [set at 84]
F: amount of exhaust gas ^(Nm 3 / h) [set by 55,000Nm ³ / h]

Moreover, fine powder baking soda remaining from the exhaust gas reaction accumulates on the bag filter as needed. Fine powder baking soda accumulated on BF reacts with HCl after the exhaust gas reaction, and the HCl concentration (Ho) at the bag filter outlet is determined. At this time, the amount of fine powdered sodium bicarbonate accumulated on BF (As) was obtained by subtracting the amount of fine powdered sodium bicarbonate reacted with HCl on BF from the fine powdered sodium bicarbonate accumulated in the exhaust gas reaction. In addition, the amount of fine powdered baking soda added on the bag filter (As) and the equivalent concentration of fine powdered sodium bicarbonate on the bag filter (Js) calculated from the amount of HCl (Hg) after the exhaust gas reaction (Equation (5) below) The HCl removal rate (αs) was determined, and the HCl concentration (Ho) at the bag filter outlet was determined (the following formula (4)).

Ho = Hg × (1−αs ÷ 100) (4)
Hg: HCl concentration after exhaust gas reaction (ppm)
Ho: HCl concentration at the outlet of the bag filter (ppm)
αs: HCl removal rate of the reaction on the bag filter (%)
[Set from the relationship between the equivalent weight of fine powdered sodium bicarbonate on the bag filter and the HCl removal rate (Fig. 4)]

Js = As ÷ {Hg ÷ 0.614 ÷ 1000 ÷ M1 × M2 × F ÷ 1000} (5)
Js: Equivalent amount of fine baking soda on bag filter As: Amount of fine baking soda on bag filter (kg / h)
Hg: HCl concentration after exhaust gas reaction (ppm)
M1: HCl molecular weight [set at 36.5]
M2: Sodium bicarbonate molecular weight [set at 84]
F: amount of exhaust gas ^(Nm 3 / h) [set by 55,000Nm ³ / h]

As = Z _n ÷ Ts × 3600 (6)
Z _n : Accumulated amount of baking soda on bag filter (kg)
Ts: Unit simulation time (= data sampling time) (sec)
[0.5 sec setting]

Z _n = Z _{n ′} × (1-2.3 ÷ T4 × Ts) (7)
Z _{n ′} : Amount of unreacted fine baking soda (kg)
T4: Accumulated fine powder baking soda on bag filter 90% extinction time constant (sec)
[7,200sec setting]
Ts: Unit simulation time (= data sampling time) (sec)
[0.5 sec setting]

Z _{n ′} = (Ag ÷ 3600 × Ts−Rg) + (Z _n−1 −Rs) (8)
Ag: Fine powder baking soda addition amount (kg / h)
Ts: Unit simulation time (= data sampling time) (sec)
[0.5 sec setting]
Rg: sodium bicarbonate reaction amount in exhaust gas reaction (kg / h)
Z _n-1 : Accumulated amount of fine baking soda on the bag filter before Ts (Sec) (kg)
Rs: Amount of sodium bicarbonate reaction in bag filter reaction (kg / h)

Rg = (Hi ÷ 0.614 ÷ 1000 ÷ M1 × M2 × F ÷ 1000) ÷ 3600 × Ts × αg ÷ 100 (9)
Hi: Inlet HCl concentration (ppm)
M1: HCl molecular weight [set at 36.5]
M2: Sodium bicarbonate molecular weight [set at 84]
F: amount of exhaust gas ^(Nm 3 / h) [set by 55,000Nm ³ / h]
αg: HCl removal rate in exhaust gas reaction (%)

Rs = (Hg ÷ 0.614 ÷ 1000 ÷ M1 × M2 × F ÷ 1000) ÷ 3600 × Ts × αs ÷ 100 (10)
Hg: HCl concentration after exhaust gas reaction (ppm)
M1: HCl molecular weight [set at 36.5]
M2: Sodium bicarbonate molecular weight [set at 84]
F: amount of exhaust gas ^(Nm 3 / h) [set by 55,000Nm ³ / h]
αs: HCl removal rate of the reaction on the bag filter (%)

The HCl concentration at the bag filter outlet after this reaction is measured by an ion electrode type HCl concentration measuring device 14. By the way, the ion electrode type HCl concentration measuring device 14 has a delay time (T1) due to facilities, a measurement delay time (T2α) due to exhaust gas sampling, and a measurement delay time (T2β, response time) due to ion electrode measurement, A control delay peculiar to feedback occurs.

Therefore, the delay time (T) of the HCl concentration measuring device 14 in this simulation is the sum of the delay time (T1) due to the facility and the measurement delay time (T2) of the HCl concentration measuring device 14 (the following equation (11)). Note that the measurement delay time (T2) of the HCl concentration measuring device 14 includes the measurement delay time (T2α) for sampling the exhaust gas after HCl treatment from the flue and the measurement delay time (response) of the ion electrode HCl concentration measuring device (T2β). Time) was set and the sum of these was set (the following formula (12)). The 90% response time (measurement delay) of the commonly used ion electrode type is affected by the diffusion of HCl gas into the absorbing solution, so T2β is set to (formula (13) below). In this simulation, the ion electrode type with long measurement delay time is 600 seconds in total, T1 = 30 seconds, T2α = 390 seconds (sampling delay 210 seconds + bromine scrubber passage delay 180 seconds), T2β = 180 seconds. (10 minutes: T1 = 0.5 minutes, T2 = 9.5 minutes).

In addition, when using the HCl concentration measuring instrument with a shorter measurement delay time than the ion electrode type, the behavior was confirmed by changing the measurement delay time.

[HCl concentration measuring device (low-speed response, simulating ion electrode type)]
T = T1 + T2 (11)
T: Delay time of simulation reaction system of HCl concentration measuring instrument (sec)
T1: Facility delay time (sec) [30 sec setting]
T2: Measurement delay time of the HCl concentration measuring instrument (sec)
T2 = T2α + T2β (12)
T2α: Exhaust gas sampling time of the HCl concentration measuring instrument (sec)
[390sec setting]
T2β: 90% response time of HCl concentration measuring instrument (sec) [180 sec setting]
T2β = 2.3 × τ (13)
Y _n = Y _n−1 + (X _n −Y _n−1 ) ÷ τ × Ts (14)
τ: Time constant (sec)
Ts: Unit simulation time (= data sampling time) (sec)
[0.5 sec setting]
Xn: Current measuring device input HCl concentration (ppm)
Yn: Current measuring device output HCl concentration (ppm)
Y _n-1 : HCl concentration (ppm) output from the previous measurement device (before Ts (sec))

Also, the addition amount of the alkaline agent for treating the acid gas is defined based on the addition output obtained by feedback calculated based on the concentration measured by the HCl measuring instrument (the above formula (1)). The basic addition amount according to the present invention was calculated using the moving average addition amount × the coefficient (1 times or less) as the lower limit of the feedback control.

Moreover, using the inlet HCl concentration which fluctuates as shown in FIG. 5, the exhaust gas reaction and the reaction on the BF are determined from the addition behavior of PID in the actual machine, the state of HCl generation (FIG. 6), and the result of this simulation reaction system (FIG. 7). The reaction efficiency with HCl was set. The results of this study are shown in FIGS. In this facility, the exhaust gas HCl removal efficiency was 80% and the BF reaction removal efficiency was 65%, which matched the behavior of the actual machine and the simulation (FIGS. 6 and 7). Therefore, the following simulation was performed under these conditions. In this simulation, in order to clarify the control responsiveness by the control method, the simulation was performed using the inlet HCl concentration (Hi) in the time zone with relatively large fluctuation.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to this.
In the examination in the following examples, a simulation reaction system is produced from the examination result of the actual machine, and the control result by each control method is examined. Since there were conditions (3 hours and 6 hours) with a long average time of the average addition amount in the basic addition amount, the inlet HCl concentration was repeatedly used, and the evaluation was made based on the results when 6 to 9 hours had elapsed.

[Comparative Example 1]
Using the inlet HCl concentration shown in FIG. 9, the PID control method “P (proportional gain) = 100% based on the HCl concentration measured by the HCl measuring device (measuring device measurement delay time meter 9.5 minutes) in the simulation. At I = 0.1 second, D = 0.1 second, additive amount output lower limit 200 kg / h, additive amount output upper limit 480 kg / h ”, the control target value (SV) of the outlet HCl concentration was set to 200 ppm to perform feedback control.
FIG. 8 shows the amount of fine powdered sodium bicarbonate added and the HCl concentration at the bag filter outlet after treatment with fine powdered sodium bicarbonate (average, 1 hour average maximum, instantaneous maximum, 1 hour average minimum, instantaneous minimum). Further, FIG. 10 shows the behavior of the added amount of fine baking soda and the bag filter outlet HCl concentration during this control.

The maximum one-hour average value of the outlet HCl concentration often used as the acid gas emission control value was 212 ppm, and the instantaneous maximum was 384 ppm.

[Example 1]
A 30-minute moving average addition amount (kg / h) was multiplied by a coefficient of 80% to obtain a basic addition amount, which was used as the lower limit of the addition amount output.
FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. Further, FIG. 11 shows the behavior of the amount of fine powdered baking soda added and the bag filter outlet HCl concentration during this control.

According to Example 1, the maximum value of HCl of 1 hour average value is 189 ppm, and the instantaneous maximum is 309 ppm. Compared with Comparative Example 1, the acid gas treatment performance is improved and the addition amount is also reduced from 330 kg / h to 315 kg / h. It was done.

Here, the outline of the step control method will be described. In Comparative Examples 2, 3, and 6, and Examples 2, 3, 9 to 11, 17, 18, and 20 to 24, control by the step control method is performed instead of the PID control method.

Unlike the PID control method, the step method is a control method that regulates the output in stages according to the HCl concentration at the outlet. Explaining in Comparative Example 2 and Examples 2 and 20 (FIG. 12), when the HCl concentration is between SV control target value [control output start concentration (above output lower limit)] and SM1, control output is output stepwise between LO and LM1. To do. The control output set by LM2 is output when the HCl concentration is between SM1 and SM2, and LH (control output upper limit) is output when the concentration is higher than SM2. Note that there is no output limitation in the normal PID control expression, and only LO and LH settings are set. The correction of the table for determining the HCl concentration and control output used in the control calculation based on the HCl gradient is performed by SVA1 and SVA2. When the HCl gradient is positive, SVA1 is subtracted from the HCl concentration used in the calculation, and when the HCl gradient is negative. SVA2 was added to the HCl concentration used in the calculation. As a result, the control output calculated when the same HCl concentration is input is the control output value when the HCl slope value is large (the acid gas concentration tends to increase), and the control output value when the HCl slope value is small. Compared to a larger format.
In addition, fine powder baking soda addition amount (Ag) is calculated | required by said Formula (1).

[Comparative Example 2]
In the simulation, the control target value (in this method, the control output of the alkaline agent is added to the output lower limit or more based on the HCl concentration measured by the HCl measuring device (measuring device measurement delay time 9.5 minutes) in the simulation. The concentration was defined as SV) was set to 200 ppm, and feedback control was performed (see FIG. 12).
FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. Further, FIG. 13 shows the behavior of the added amount of fine powdered sodium bicarbonate and the bag filter outlet HCl concentration during this control.

The maximum value of 1 hour average value of the outlet HCl concentration by the step method was 212 ppm, and the instantaneous maximum was 383 ppm.

[Example 2]
A 30-minute moving average addition amount (kg / h) is multiplied by an 80% coefficient to obtain the basic addition amount, which is used as the lower limit of the addition amount output. did.
FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. Further, FIG. 14 shows the behavior of the amount of fine baking soda added and the bag filter outlet HCl concentration during this control.

According to Example 2, even in the step method, the maximum value of the one-hour average value of the outlet HCl concentration was 195 ppm, and the instantaneous maximum was 320 ppm, so that the acid gas treatment performance was improved and the addition amount was 295 kg / h as compared with Comparative Example 2. To 289 kg / h.

[Comparative Example 3]
When the 6-second average of the latest HCl concentration slope is positive in the step-type control based on the HCl concentration measured by the HCl measuring device (measuring device measurement delay time 9.5 minutes) in the simulation, the control target value (SV ) Was set to 180 ppm (SV-20 ppm), and when the 6-second average of the latest gradient of HCl concentration was negative, feedback control was performed with the control target value (SV) set to 220 ppm (SV + 20 ppm) (see FIG. 15).
FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. In addition, FIG. 16 shows the behavior of the added amount of fine baking soda and the bag filter outlet HCl concentration during this control.

In addition to this step method, the maximum value of the one-hour average value of the outlet HCl concentration by this feedback control in which the control target value was changed by the gradient of HCl concentration (hereinafter referred to as SV change) was 216 ppm, and the instantaneous maximum was 381 ppm. .

[Example 3]
The feedback control is performed under the same setting conditions of the feedback type shown in Comparative Example 3 except that the 30-minute moving average addition amount (kg / h) is multiplied by a coefficient of 80% to obtain the basic addition amount and used as the lower limit of the addition amount output. did.
FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. In addition, FIG. 17 shows the behavior of the added amount of fine powdered sodium bicarbonate and the bag filter outlet HCl concentration during this control.

According to Example 3, even in the feedback system, the maximum value of the one-hour average value of the outlet HCl concentration was 198 ppm, and the instantaneous maximum was 283 ppm, so that the acid gas treatment performance was improved as compared with Comparative Example 3, and the addition amount was also 301 kg / Reduced from h to 289 kg / h.

[Examples 4 to 8]
Moving average addition amount (kg / h) with varying average time [Example 4: 5 minutes, Example 5: 15 minutes, Example 6: 1 hour, Example 7: 3 hours, Example 8: 6 hours] Was multiplied by a coefficient of 80% to obtain a basic addition amount, which was used as the lower limit of the addition amount output.
FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. In addition, the behavior of the amount of fine powdered sodium bicarbonate added and the bag filter outlet HCl concentration during this control is shown in FIGS.

According to Examples 4 to 8, the basic addition amount obtained by multiplying the average addition amount by a factor of 1 or less is used as a factor for feedback control, and the acid gas can be stably treated by calculating the addition amount of the alkaline agent. It becomes.

The effects of Examples 4 to 8 are obtained by using the factor of the average addition amount for feedback, and there is no particular limitation on the average time. In the addition amount average time of 5 minutes (Example 4), with the same addition amount, the average value of the outlet HCl concentration for one hour at the maximum is 186 ppm, the instantaneous maximum is 369 ppm, and the acid gas stabilization treatment effect is obtained. Further, even in the average addition amount time of 6 hours (Example 8), the maximum one-hour average value of the outlet HCl concentration was 194 ppm and the instantaneous maximum value was 308 ppm, and a stable treatment effect was obtained and the addition amount was reduced to 311 kg / h. The average amount of addition is preferably 5 minutes or more, particularly preferably 15 minutes to 6 hours.

[Examples 9 to 11]
Moving average addition amount (kg / h) with varying average time [Example 9: 15 minutes, Example 10: 1 hour, Example 11: 3 hours] multiplied by a factor of 80% to give a basic addition amount Except for use as the lower limit of the amount output, calculation was performed under the same setting conditions shown in Comparative Example 3, and feedback control was performed.
FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. In addition, the behavior of the amount of fine powdered sodium bicarbonate added and the bag filter outlet HCl concentration during this control is shown in FIGS.

According to Examples 9 to 11 when the addition amount average time in the feedback control by the step + SV change method is changed from 15 minutes to 3 hours, the acid gas stabilization treatment effect and the addition amount reduction effect are obtained regardless of the addition amount average time. can get. This method is a control method that is particularly excellent in the effect of reducing the addition amount of 288 to 292 kg / h.

[Examples 12 to 16]
The coefficient by which the moving average addition amount (kg / h) for 1 hour is multiplied is changed [Example 12: 95%, Example 13: 90%, Example 14: 80%, Example 15: 70%, Example 16:50 %] The basic addition amount was used, and the feedback control was performed under the same setting conditions as shown in Comparative Example 1 except that it was used as the addition output lower limit.
FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. In addition, the behavior of the added amount of fine sodium bicarbonate and the bag filter outlet HCl concentration during this control is shown in FIGS.

The effects of Examples 12 to 16 are obtained by utilizing the factor of the average addition amount for feedback, and the coefficient by which the average addition amount is multiplied when calculating the basic addition amount is not particularly limited as long as it is 1 or less. . When this coefficient is multiplied by a factor of 1 (100%) or more, even if the inlet HCl concentration is reduced, the average addition amount used for the basic addition amount does not decrease, causing excessive addition.
When the coefficient for calculating the basic addition amount is 95% (Example 12) to 70% (Example 15), the maximum one-hour average value and the instantaneous maximum value of the outlet HCl concentration are lower than those of Comparative Example 1. In addition, the effect of stabilizing the acid gas was obtained and the effect of reducing the addition amount was obtained. Further, when the coefficient is 50% (Example 16), although the amount added is slightly increased, the effect of stabilizing the acidic gas is obtained. The coefficient by which the average addition amount is multiplied when calculating the basic addition amount may be one or less. Preferably it is 50 to 95%, particularly 70 to 90%.

[Examples 17 and 18]
The coefficient multiplied by the 1-hour moving average addition amount (kg / h) was changed [Example 17: 90%, Example 18: 70%], and the basic addition amount was used. Calculation and feedback control were performed under the same setting conditions shown.
FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. In addition, the behavior of the added amount of fine baking soda and the bag filter outlet HCl concentration during this control is shown in FIGS.

According to Examples 17 and 18 in which the coefficient to be multiplied when calculating the basic addition amount in the feedback control by the step + SV change method is changed by 70 to 90%, the acid gas is used regardless of the coefficient for calculating the basic addition amount. A stable treatment effect and an additive amount reduction effect are obtained. In addition, this method is a control method that is particularly excellent in the effect of reducing the addition amount of 289 to 297 kg / h.

[Comparative Example 4]
Based on the HCl concentration measured by the HCl measuring device (measurement device measurement delay time meter 2 seconds) in the simulation, the PID control method “P (proportional gain) = 100%, I = 0.1 seconds, D = 0.1 seconds. , “Addition amount output lower limit 200 kg / h, addition amount output upper limit 480 kg / h”, the control target value (SV) of the outlet HCl concentration was set to 200 ppm to perform feedback control.
FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. Further, FIG. 33 shows the behavior of the amount of fine powdered baking soda added and the bag filter outlet HCl concentration during this control.

Investigated the influence of measurement equipment measurement delay time. When feedback control was performed using a high-speed response HCl measuring instrument with little measurement delay, it was predicted that changes in the amount of alkali agent added and changes in the outlet HCl concentration occurred instantaneously and improved. However, poor addition due to variation in addition of alkaline agent is predicted to occur, and the maximum one-hour average value of the outlet HCl concentration often used as the acid gas emission control value was 209 ppm, and the instantaneous maximum was 385 ppm.

[Example 19]
Feedback control was performed under the same conditions as in Example 1 except that the PID control calculation was performed based on the HCl concentration measured by the HCl measuring device (measurement device measurement delay time meter 2 seconds) in the simulation.
FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. In addition, FIG. 34 shows the behavior of the amount of fine powdered sodium bicarbonate added and the bag filter outlet HCl concentration during this control.

[Example 20]
Feedback control was performed under the same conditions as in Example 2 except that the calculation by the step method was performed based on the HCl concentration measured by the HCl measuring instrument (measurement instrument measurement delay time meter 2 seconds) in the simulation.
FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. In addition, FIG. 35 shows the behavior of the amount of fine powdered baking soda added and the bag filter outlet HCl concentration during this control.

[Example 21]
Feedback control was performed under the same conditions as in Example 3 except that the calculation by the step + SV change method was performed based on the HCl concentration measured by the HCl measuring device (measurement device measurement delay time meter 2 seconds) in the simulation.
FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. Further, FIG. 36 shows the behavior of the amount of fine powdered sodium bicarbonate added and the bag filter outlet HCl concentration during this control.

According to Example 21, the effect is exhibited regardless of the length of the measurement delay time of the measuring device. In addition, any feedback format can be used as a control format. In Examples 19 to 21, the measurement delay time was assumed to be 2 seconds, but the addition failure of the alkaline agent due to the feedback was suppressed, and in all cases, the effect of stabilizing the acidic gas and the effect of reducing the addition amount were obtained.

[Example 22]
In the simulation, when the one-hour average value of the outlet HCl concentration exceeded 190 ppm, the same conditions as in Example 10 (delay time 9.5 minutes, step + SV change) except that 480 kg / h alkaline agent was added. Feedback control. FIG. 8 shows the added amount of fine powdered sodium bicarbonate and the HCl concentration at the bag filter outlet after the treatment with fine powdered sodium bicarbonate. In addition, FIG. 37 shows the behavior of the amount of fine powdered sodium bicarbonate added and the bag filter outlet HCl concentration during this control.

There are facilities that manage the acid gas discharge concentration by using an hourly average value of each acid gas concentration (hydrogen chloride, sulfur oxide concentration). In control, control is generally performed by setting a control target value (SV). However, the control target value is only a target, and there are cases where the concentration exceeds the target value as a result of control.
This example is an example in which the one-hour average control (addition of 480 kg / h for 190 ppm or more) was performed in Example 10 where the one-hour average value of the outlet HCl concentration exceeded 200 ppm. When the 1 hour average value at the outlet is close to the concentration to be managed, by controlling the addition of a large amount of alkali agent, further stabilization treatment effect of acid gas and efficient use of the alkali agent become possible. .

Hereinafter, in describing Comparative Examples 5 and 6 and Examples 23 and 24, which are actual machine examination results, the configuration of the acid gas treatment system 2 used in Comparative Examples 5 and 6 and Examples 23 and 24 will be described.

FIG. 38 is a block diagram showing the configuration of the acid gas treatment system 2 in which fine baking soda is added to HCl, which is exhaust gas in an incineration facility.

The acid gas treatment system 2 includes a control device 21, a fine powder baking soda addition device 22, a fine powder sodium bicarbonate addition device 26, a bag filter 23, and an HCl concentration measurement device (ion electrode system) 24. The control device 21 feedback-controls the added amount output value of the fine baking soda based on the HCl concentration measurement signal transmitted from the HCl concentration measuring device (ion electrode system) 24 and the basic addition amount calculated from the past average addition amount. It is calculated by (PID control method or step method). The fine powdered sodium bicarbonate adding device 22 adds fine powdered sodium bicarbonate to HCl in the exhaust gas based on the added amount output value of the fine powdered sodium bicarbonate calculated by the control device 21. Further, the fine powder baking soda addition device 26 adds a certain amount of fine powder baking soda to the HCl in the exhaust gas irrespective of the addition amount output value of the fine powder sodium bicarbonate calculated by the control device 21.
The basic addition amount is calculated by multiplying the past average addition amount according to the average time (for example, moving average time) by a factor of 1 or less.

The bag filter 23 removes dust after the reaction between HCl in the exhaust gas and fine baking soda. The HCl concentration measuring device (ion electrode system) 24 is composed of fine powder baking soda accumulated on the bag filter 23 (fine powder sodium bicarbonate remaining by reaction with HCl in the exhaust gas is accumulated on the bag filter 23) and HCl after the exhaust gas reaction. HCl concentration (bag filter outlet HCl concentration described later) is measured, and an HCl concentration measurement signal is transmitted to the control device 21.
The inlet HCl concentration of the bag filter is measured by an HCl concentration measuring device (laser method) (not shown).

The acid gas treatment system 2 repeats such a cycle and performs feedback control, so that the control device 21 performs control to make the control output value of the added amount of fine powder baking soda appropriate.

[Comparative Example 5]
In an industrial waste incinerator, a laser type HCl measuring device (KLA-1 manufactured by Kyoto Electronics Industry) was installed between the exit of the temperature reducing tower and the bag filter, and the inlet HCl concentration was measured. Further, feedback control was carried out with an oxygen conversion value for managing the emission reference value based on a signal measured by an ion electrode type HCl measuring device (HL-36N manufactured by Kyoto Electronics Industry) at the bag filter outlet. The feedback addition output (SV 180 ppm) based on the SOx concentration signal at the outlet was added to the addition output based on the HCl concentration, but this was omitted from this report because SOx was not generated at this facility.
As an alkaline agent for treating acid gas, 8 μm fine powdered sodium bicarbonate (Hypercer B-200 manufactured by Kurita Kogyo Co., Ltd.) was added by the above feedback control. Two alkali agent addition devices are used due to the problem of the maximum addition amount, one is 180 kg / h quantitative addition, and one is based on the outlet HCl concentration signal, “lower limit is 20 kg / h, upper limit is 300 kg / h, Feedback control was performed with PID control setting P (proportional gain) = 100%, I = 0.1 seconds, D = 0.1 seconds.
FIG. 39 shows the bag filter inlet HCl concentration, the bag filter outlet HCl concentration, and the addition amount of fine baking soda (total of two addition devices). Further, FIG. 40 shows the behavior of the addition amount of fine baking soda and the HCl concentration at the bag filter inlet / outlet when this control is performed.

[Comparative Example 6]
At the same facility, feedback control was performed with an HCl concentration signal (oxygen conversion value) measured with an ion electrode type HCl measuring device (HL-36N manufactured by Kyoto Electronics Industry) at the bag filter outlet. Similarly, the feedback addition output (SV 180 ppm) based on the SOx concentration signal at the outlet was added to the addition output based on the HCl concentration.
Similarly, one addition device was used for 180 kg / h quantitative addition, and one was a “step + SV change method (see FIG. 41 for details)”.
FIG. 39 shows the bag filter inlet HCl concentration, the bag filter outlet HCl concentration, and the addition amount of fine baking soda (total of two addition devices). Further, FIG. 42 shows the behavior of the addition amount of fine baking soda and the HCl concentration at the bag filter inlet / outlet when this control is performed.

[Example 23]
In the same facility, the basic addition amount [30 minutes moving average addition amount, coefficient 70%] is utilized in the feedback control of “step + SV change method”, and the outlet HCl concentration one-hour average value is 213 ppm or more [this facility HCl control value Feedback control was performed with the same settings as in Comparative Example 6 except that 300 kg / h was added at 215 ppm or less]. Similarly, the feedback addition output (SV 180 ppm) based on the SOx concentration signal at the outlet was added to the addition output based on the HCl concentration.
Similarly, one addition device was used for 180 kg / h quantitative addition, and one was a “step + SV change method (see FIG. 41 for details)”.
FIG. 39 shows the bag filter inlet HCl concentration, the bag filter outlet HCl concentration, and the addition amount of fine baking soda (total of two addition devices). In addition, FIG. 43 shows the behavior of the addition amount of fine baking soda and the HCl concentration at the bag filter inlet / outlet when this control is performed.

This example is a result of application by an actual machine of the present invention. Compared with Comparative Examples 5 and 6, the fluctuation of the inlet HCl concentration was reduced. According to this example, the addition equivalent indicating the addition amount of the alkaline agent relative to the inlet HCl concentration by the efficient addition of the alkaline agent according to the present invention can be reduced as compared with Comparative Examples 5 and 6, and efficient control is possible. Met.

[Example 24]
In the same facility, in the feedback control of “step + SV change method”, the same setting as in Example 23, except that a highly reactive slaked lime (Tamacalc ECO manufactured by Okutama Kogyo Co., Ltd.) with a specific surface area of 30 m ² / g or more is used together. The feedback control was implemented. Similarly, the feedback addition output (SV 180 ppm) based on the SOx concentration signal at the outlet was added to the addition output based on the HCl concentration.
In addition, one addition device was a high-reaction slaked lime 170 kg / h quantitative addition, and the other was “step + SV change method (see FIG. 41 for details)”.
FIG. 39 shows the bag filter inlet HCl concentration, the bag filter outlet HCl concentration, and the addition amount of fine baking soda (total of two addition devices). Further, FIG. 44 shows the behavior of the addition amount of fine baking soda and the HCl concentration at the bag filter inlet / outlet when this control is performed.

This example is a case where a relatively industrially inexpensive slaked lime and fine powdered sodium bicarbonate are used in combination. Also in this method, the stable treatment effect of acid gas can be obtained stably. This is an industrially effective technique because it uses inexpensive slaked lime and reduces acid gas processing costs.

DESCRIPTION OF SYMBOLS 1 Acid gas processing system 11 Control apparatus 12 Fine powder baking soda addition apparatus 13 Bag filter 14 HCl concentration measuring instrument

Claims

Add an alkali agent to combustion exhaust gas containing acid gas, and measure the acid gas concentration after collecting dust. A processing method,
A step of calculating a basic addition amount by multiplying an average addition amount according to at least the average time by a factor of 1 or less;
And a step of calculating an addition amount output value of the alkaline agent by feedback calculation based on the calculated basic addition amount.
In the step of calculating the added amount output value by feedback calculation,
The acid gas treatment method according to claim 1, wherein the calculated basic addition amount is set as a lower limit value of the addition amount output value of the alkaline agent.
The step of calculating the added amount output value by feedback calculation,
Setting a range of slopes of at least two acid gas concentrations;
Setting a control target value of the acid gas concentration for each of the at least two slope ranges;
A step of calculating an addition amount output value of the alkaline agent based on at least the measurement signal and a control target value for each range of the slope, and
In the step of setting the control target value, a control target value set when the slope range of the acid gas concentration is large is smaller than a control target value set when the slope range of the acid gas concentration is small. 3. The method for treating acidic gas according to 1 or 2.
The step of calculating the added amount output value by feedback calculation,
Setting one or more new upper limit values of the addition amount output value corresponding to the acidic gas concentration between the lower limit value and the upper limit value of the addition amount output value calculated based on the measurement signal; Furthermore, the processing method of the acidic gas in any one of Claim 1 to 3 which has.
In the step of calculating the basic addition amount, the basic addition amount is 0.5 to 0.95 times the average addition amount when the average time is 5 minutes or more. Acid gas treatment method.
The step of calculating the added amount output value by feedback calculation,
In addition to the feedback calculation, the method further includes a step of calculating an addition amount output value of the alkali agent by using both outputs of the control output calculated from the hydrogen chloride concentration and the control output calculated from the sulfur oxide concentration. 6. The method for treating an acidic gas according to any one of 5 above.
The step of calculating the added amount output value by feedback calculation,
The acidic gas treatment according to any one of claims 1 to 6, further comprising a step of calculating an addition amount output value of an alkaline agent based on an average value of hydrogen chloride concentration and / or sulfur oxide concentration in addition to the feedback calculation. Method.
The method for treating acidic gas according to any one of claims 1 to 7, wherein the alkaline agent is fine powder sodium bicarbonate having an average particle size of 5 to 30 µm.
The method for treating acidic gas according to claim 8, wherein another alkali agent different from the fine powder baking soda is used in combination.
The other alkaline agent is at least one alkaline agent selected from the group consisting of slaked lime, sodium hydroxide, magnesium hydroxide, magnesium oxide, sodium carbonate, sodium sesquicarbonate, natural soda, and crude sodium bicarbonate. The processing method of the acidic gas as described in 2.