JP5834469B2 - Acid gas treatment method - Google Patents

Description

  The present invention relates to a method for treating acidic gases such as harmful hydrogen chloride and sulfur oxide 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 to 30 μm, which is an alkaline agent for treating acid gas, has higher reactivity than slaked lime, can stably treat acid gas, has little 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 great 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.

  Various control methods have been studied in order 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 the excessive addition of feedback control, and an effect of reducing the acid gas stabilization treatment and the excessive addition of the alkaline agent is obtained.

JP 2002-113327 A Japanese Patent Laid-Open No. 10-165552 JP 2006-75758 A

  However, in Patent Document 1, it is possible to cope suddenly with the entrance to some extent, but the measurement delay of the measuring device is not taken into account, and it is possible to deal with the acid gas processing failure due to the addition lag of the alkaline agent due to the measurement delay. Can not do it. Furthermore, in Patent Documents 2 and 3, the measurement environment of the flue before dust collection has a higher acid gas concentration and higher temperature than the measurement environment after dust collection, and it is necessary to take countermeasures against corrosion of the measurement equipment material. is there. Further, since a large amount of soot is present in the exhaust gas before dust removal, labor is required for dust removal countermeasures and maintenance such as replacement of dust filters. In addition, the measurement failure caused by the malfunction of these measuring instruments is a big problem in stably managing the acid gas concentration at the outlet because the measurement signal of the acid gas concentration directly affects the amount of the alkali agent added. .

  In consideration of the above-described present situation, the present invention provides a measurement environment in which acid gas can be stably measured, that is, a feedback form that controls the amount of alkali agent added based on an acid gas concentration measurement signal after the dust collection process. An object of the present invention is to provide a method for treating an acidic gas that reduces acid gas treatment failures due to measurement delays in control and excessive addition of an alkaline agent.

  (1) Addition of alkali agent based on measurement signal of acid gas concentration measuring equipment installed to measure acid gas concentration after adding alkali agent to combustion exhaust gas containing acid gas and collecting dust A method for treating an acid gas in which the amount is feedback-controlled, and a plurality of acid gas concentration measuring devices having different measurement delay times (for example, an HCl concentration measuring device (low speed) 14 and an HCl concentration measuring device (high speed) 15 described later) ) Measuring the concentration of the same kind of acid gas, and calculating the output value of the added amount of the alkaline agent by feedback calculation based on the measurement signals of the plurality of acid gas concentration measuring devices. Method.

  The acid gas concentration at the exit of the conventional bag filter is measured with a single measuring instrument based on the ion electrode method with a measurement delay time of 5 to 10 minutes, for example, and the amount of alkali agent added is controlled by feedback based on the measurement signal doing. This method causes excessive addition of alkaline agent due to measurement delay of the measuring instrument.

  On the other hand, according to the invention of (1), the alkali is based on the measurement signals of the measuring device having a long measurement delay time and the measuring device having a short measurement delay time, that is, a plurality of measuring devices having different measurement delay times of the acid gas concentration. The addition amount output value of the agent is calculated by feedback calculation. As a result, it is possible to combine measurement devices with a short measurement delay time instead of a single measurement device with a long measurement delay time, thus reducing the excessive addition of alkaline agent due to the measurement delay of the acid gas concentration measurement device in feedback control. be able to.

  In addition, according to the invention of (1), since a plurality of acid gas concentration measuring devices having different measurement delay times are provided, the acid gas at the bag filter outlet is measured by a measuring device having a long measurement delay time but high measurement reliability. In addition to being able to measure the concentration appropriately, it is possible to improve the measurement reliability as compared to feedback control with a measurement device having a short measurement delay time but low measurement reliability. Therefore, the alkali agent can be added appropriately, and the treatment efficiency of the acidic gas can be further improved.

  In addition, by combining a measuring instrument with a long measurement delay time with a measuring instrument with a short measurement delay time, the timing of adding an alkaline agent when the acid gas increases can be made faster than in the conventional control, and the acid delay due to the measurement delay of the acid gas measuring device can be reduced. Gas processing defects can be improved.

  (2) The step of calculating the addition amount output value by feedback calculation includes an upper limit value of a plurality of addition amount output values calculated based on the plurality of measurement signals (for example, a plurality of addition amount output values to be described later). (100% value) and an addition amount of a value smaller than the upper limit value (for example, a value obtained by applying a 50% output limit described later) with respect to at least one of the calculated upper limit values A method for treating an acidic gas according to (1), comprising a step of calculating an output value.

  According to the invention of (2), an addition amount output value having a value smaller than the upper limit value is calculated for at least one upper limit value among the calculated upper limit values of the plurality of addition amount output values.

  As a result, compared to operating both of the additive amount output values calculated based on the measurement signal of the measuring instrument having a long measurement delay time and a short measurement delay time at the upper limit value (100%), for example, the measurement delay time By restricting only the added amount output value calculated based on the measurement signal of a long measuring instrument (for example, 50% output limit), the excessive addition of alkaline agent is further prevented while stabilizing the treatment of acid gas. can do.

  Furthermore, by applying a limit (for example, a 50% output limit) to both the measurement device with a long measurement delay time and the additive amount output value calculated based on the measurement signal of the measurement device with a short measurement delay time, It is possible to further prevent the excessive addition of the alkaline agent while stabilizing the treatment of the acid gas.

  (3) The step of calculating the added amount output value by feedback calculation includes at least two acid gas concentration gradient ranges (for example, a 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) smaller than the control target value set when the slope range is small (for example, when the 6-second average of the slope of the latest HCl concentration described later is negative (when the acid gas concentration is lowered)) Acid gas treatment method.

  According to the invention of (3), when the slope of the acid gas concentration at the bag filter outlet is positive (when the acid gas concentration is increased), the acid gas concentration is lower than when the slope is negative (when the acid gas concentration is lowered). Since the control target value is reduced, the amount of alkali agent added when the acid gas concentration is increased can be increased more than when the acid gas concentration is decreased. Conversely, the amount of the alkali agent added when the acidic gas concentration is lowered can be made smaller than when the acidic gas concentration is increased. Therefore, the alkaline agent addition output by feedback calculation can be implemented ahead of schedule, and the influence of measurement delay can be further reduced.

  (4) The step of calculating the addition amount output value by a feedback calculation includes a lower limit value of the addition amount output value calculated based on the measurement signal (for example, LO [control in FIG. 21, FIG. 23, FIG. Output lower limit]) and an upper limit value (for example, LH [control output upper limit] in FIGS. 21, 23, and 31 described later), the acidic gas concentration (for example, FIGS. 21, 23, and 31 described later). Corresponding to the BF outlet HCl concentration) (for example, LM1 [output limit 1], LM2 [output limit 2] in FIGS. 21, 23, and 31 described later) 1). The acidic gas treatment method according to any one of (1) to (3), further including a step of setting one or more.

There is only one output upper limit in the normal feedback calculation, and when the acidic gas exceeds the control target value, the alkaline agent can be added up to the upper limit value regardless of the magnitude of the acidic 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) The method for treating acidic gas according to any one of (1) to (4), wherein the alkaline agent is fine powdered baking soda having an average particle diameter of 5 to 30 μm.

The alkaline agent used in the present invention is preferably finely powdered baking soda having an average particle size of 5 to 30 μm, which is particularly fast in reaction with acid gas. Since the reaction of fine baking soda is fast, the control responsiveness is good and the performance of the present invention can be exhibited effectively. However, the present invention is based on a control method and can be applied to slaked lime. The slaked lime can exhibit the performance of the present invention when it is a high specific surface area slaked lime having a high specific surface area with high reactivity with acid gas, for example, 30 m ² / g or more.

  (6) The processing method of acidic gas as described in (5) which uses together the other alkaline agent different from the said fine powder baking soda.

  There is no restriction | limiting in particular as an alkaline agent which exhibits the effect of this invention. Examples of the alkali agent other than fine powdered sodium bicarbonate include 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 with a high reactivity with an acid gas of less than 30 μm, particularly 5 to 20 μm is preferable. An agent having a particle size 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.

  (7) 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 (6).

  It is also economically effective to use an inexpensive alkaline agent different from the alkaline agent for carrying out the control according to the present invention. Examples of generally used inexpensive alkali agents include slaked lime, sodium hydroxide, magnesium hydroxide, magnesium oxide, sodium carbonate, sodium sesquicarbonate, natural soda, and crude baking soda.

  According to the present invention, in a measurement environment in which acid gas can be stably measured, that is, in a feedback format in which the amount of alkali agent added is controlled based on an acid gas concentration measurement signal after the dust collection process, the current feedback control Improvement of acid gas processing failure due to measurement delay and reduction of excessive addition of alkaline agent are possible, and stable addition of acidic gas becomes possible by the efficient addition of alkaline agent.

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 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 powder sodium bicarbonate addition amount in Example 1, 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 2. 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. 12 is a table of step control method control settings in Example 10. 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 table | surface of the control setting of the step control system in Example 11 and 12. 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 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 3. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount, inlet HCl concentration, and outlet HCl concentration in Example 13. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount, inlet HCl concentration, and outlet HCl concentration in Example 14. It is a table | surface of the control setting of the step control system in Example 15 and 16. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount, inlet HCl concentration, and outlet HCl concentration in Example 15. It is a graph which shows the behavior of the fine sodium bicarbonate addition amount, inlet HCl concentration, and outlet HCl concentration in Example 16.

  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 acidic gas treatment system 1 that adds fine powdered baking soda to HCl that is an 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, an HCl concentration measurement device (low speed) 14, and an HCl concentration measurement device (high speed) 15. The control device 11 performs feedback control (PID control method or step method) on the added amount output value of the fine baking soda based on the HCl concentration measurement signal transmitted from the HCl concentration measuring device (low speed) 14 and the HCl concentration measuring device (high speed) 15. ). 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 bag filter 13 removes dust after the reaction between HCl in the exhaust gas and fine baking soda. The HCl concentration measuring device (low speed) 14 and the HCl concentration measuring device (high speed) 15 are configured to accumulate 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 the HCl after the exhaust gas reaction, the HCl concentration (bag 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 (low speed) 14 is, for example, an ion electrode type HCl concentration measuring device, and the HCl concentration measuring device (high speed) 15 is, for example, a laser type HCl concentration measuring device. The HCl concentration measurement delay time of the HCl concentration measuring device (low speed) 14 is longer than that of the HCl concentration measuring device (high speed) 15.

  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. It is preferable to install (low speed) 14 and HCl concentration measuring device (high speed) 15. 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 performed by the control device 11 will be described in detail.

  Based on the HCl concentration measurement signal transmitted from each of the HCl concentration measuring device (low speed) 14 and the HCl concentration measuring device (high speed) 15, the control device 11 sets the upper limit value of each added amount output value of the fine powdered sodium bicarbonate added amount. calculate. In this case, output restriction (for example, 50% output restriction) may be performed for both or one of the calculated upper limit values.

  Thus, both of the plurality of added amount output values calculated based on the HCl concentration measurement signal transmitted from each of the HCl concentration measuring device (low speed) 14 and the HCl concentration measuring device (high speed) 15 are set to the upper limit value (100% ), For example, by limiting only the added amount output value calculated based on the measurement signal of the HCl concentration measuring device (low speed) 14 having a long measurement delay time (for example, 50% output limitation). Further, it is possible to further prevent the excessive addition of the alkaline agent while stabilizing the treatment of the acid gas.

  Furthermore, it is limited to both the added amount output value calculated based on the measurement signal of the HCl concentration measuring device (low speed) 14 having a long measurement delay time and the HCl concentration measuring device (high speed) 15 having a short measurement delay time (for example, (50% output limitation) can also prevent the excessive addition of the alkaline agent while stabilizing the treatment of the acid gas.

  Further, the control device 11 provides two ranges, a positive range and a negative range, for the gradient of HCl concentration (concentration change rate with time). 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.

  The setting for changing the control target value in accordance with the gradient of the HCl concentration may be performed for both the HCl concentration measuring device (low speed) 14 and the HCl concentration measuring device (high speed) 15, or one of them. You may do it only for.

  Further, 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 the 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.

  Here, a new control output upper limit value is set corresponding to the HCl concentration. However, the higher the HCl concentration, the higher the new control output upper limit value is set. However, in order to suppress the excessive addition of the alkaline agent, a value smaller than the upper limit value of the control output value set in the PID control method (for example, LH [control output upper limit] in FIGS. 21 and 23 described later) It is preferable to do.

  As an example of setting a new control output upper limit value, the higher the HCl concentration is, the higher the new control output upper limit value is, as in the control output addition amount corresponding to the BF outlet HCl concentration described in FIGS. It is preferable to set.

  The acidic gas concentration measuring device used in the present embodiment can be implemented if the delay time of the measuring device is different regardless of the measurement method. As for the HCl concentration, the ion electrode method with a long measurement delay time of 5 to 10 minutes is the mainstream. In addition, although the response in an ion electrode part is about 3 minutes, if the delay by gas sampling is included, it will be 5 to 7 minutes. Furthermore, if there is a possibility that bromine is mixed in the sampling gas as in an industrial waste incinerator, a bromine scrubber that removes bromine is installed to greatly affect the measured value of hydrogen chloride. The bromine scrubber passage time is about 3 minutes and the measurement delay time is about 8 to 10 minutes.

  In addition, the measurement delay time of hydrogen chloride by single absorption line absorption spectroscopy using a laser is as short as a few seconds (1-2 seconds). The present invention can be implemented by performing feedback control using two measuring devices having different measurement delay times, but it is optimal to combine these measuring devices with the current measuring device. Moreover, the infrared absorption method is the mainstream for sulfur oxide, and the delay time is about 3 minutes to 5 minutes. Sulfur oxide can also be implemented by combining measuring instruments having different measurement delay times as with hydrogen chloride.

  The main purpose of the present invention is to improve the measurement delay of acid gas. Therefore, the ion gas method hydrogen chloride measuring device with a large measurement delay is used to measure the acid gas after the bag filter and perform feedback control. It is particularly effective in facilities that have

  In industrial waste incinerators and combustion facilities of private factories, hydrogen chloride and sulfur oxides are often generated at high concentrations. At this time, both hydrogen chloride and sulfur oxide are to be treated, and the control output and sulfur oxide concentration obtained in the above control method based on the HCl concentration of the HCl concentration measuring device provided at the rear stage of the bag filter. By adding, for example, the control outputs obtained in the control method based on the above, 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 by the 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 many cases where the concentration 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 amount of addition (predetermined a certain addition amount) is added, so that the amount of addition can be reduced and the acid gas can be stably treated. High control is possible.

The fine powdered sodium bicarbonate used in the present embodiment is preferably fine powdered sodium bicarbonate having an average particle size that is particularly fast for reaction with an acidic gas and adjusted to 5 to 30 μm. This is because the control response is good because the reaction of the fine powdered baking soda is fast, and the performance of this embodiment can be exhibited effectively. However, this embodiment is based on a control method, and can be applied to slaked lime. The slaked lime is a slaked lime with a high specific surface area having a high specific surface area that is highly reactive with acid gas, for example, 30 m ² / g or more, and can exhibit the performance of this embodiment.

  In the present embodiment, fine powder baking soda is used as the alkaline agent, but there is no particular limitation on the alkaline agent that exhibits the effect of the present embodiment. Examples of the alkali agent other than fine powdered sodium bicarbonate include 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 with a high reactivity with an acid gas of less than 30 μm, particularly 5 to 20 μm is preferable. An agent having a particle size 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.

  It is also economically effective to use an inexpensive alkaline agent different from the fine powder baking soda that performs the control according to the present embodiment. Examples of generally used inexpensive alkali agents include slaked lime, sodium hydroxide, magnesium hydroxide, and magnesium oxide.

  The simulation reaction system will be described.

[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 chemical injection control at an incineration facility, the HCl concentration (after processing) signal of an ion electrode type HCl concentration measuring device (low speed) installed at the bag filter outlet and an HCl concentration measuring device (high speed) such as a laser system, for example. Based on the above, the amount of chemical addition (fine powdered sodium bicarbonate addition amount (Ag)) is determined by calculation of a control equation such as PID (the following formula (1)), and the determined addition amount of fine powdered sodium bicarbonate (acid gas treatment agent) is exhausted ( To the 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 × K1 ÷ 100 + Ag2 × K2 ÷ 100) + LO (1)
Ag: Fine powder baking soda addition amount [kg / h]
Ag1: Addition amount [kg / h] defined by the output of the HCl concentration measuring device (low speed)
Ag2: Addition amount [kg / h] defined by the output of the HCl concentration measuring instrument (high speed)
LO: Lower limit of addition amount [kg / h]
K1: Adjustment factor for HCl measuring device 1 (low speed) [%]
K2: Adjustment coefficient for HCl measuring device 2 (high speed) [%]

  In addition, the HCl removal rate of 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, the fine baking soda remaining by 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 (low speed) 14 and an HCl concentration measuring device (high speed) 15. By the way, in the ion electrode type HCl concentration measuring device (low speed) 14, the delay time by the facility (Ta), the measurement delay time by the exhaust gas sampling (TBα), and the measurement delay time by the ion electrode type measurement (Tbβ, response time) There is a control delay specific to feedback.

  Therefore, the delay time (T1) of the HCl concentration measurement device (low speed) 14 in this simulation is the sum of the delay time (Ta) due to the facility and the measurement delay time (Tb) of the HCl concentration measurement device (low speed) 14 (the following equation) (11)). The measurement delay time (Tb) of the HCl concentration measuring device (low speed) 14 is the measurement delay time (Tbα) for sampling the exhaust gas after HCl treatment from the flue and the measurement of the ion electrode type HCl concentration measuring device (Tbβ). A delay time (response time) was set, and the sum of these was set (formula (12) below). 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 Tbβ is set to (Formula (13) below). In this simulation, the ion electrode type with a long measurement delay time is 600 seconds in total, Ta = 30 seconds, Tbα = 390 seconds (sampling delay 210 seconds + bromine scrubber passage delay 180 seconds), and Tbβ = 180 seconds. (10 minutes: Ta = 0.5 minutes, Tb = 9.5 minutes).

  Further, the delay time (T2) of the HCl concentration measuring device (high speed) 15 in this simulation is the sum of the delay time (Ta) by the facility and the measurement delay time (Tc) of the HCl concentration measuring device (high speed) 15 (the following) Formula (15)). The behavior was confirmed by changing the measurement delay time (Tc) of the HCl concentration measurement device (high speed) 15 having a measurement delay time shorter than that of the ion electrode type.

  The amount of fine baking soda added obtained by this feedback is obtained based on the addition output (Ag 1) obtained from the HCl concentration measuring device (low speed) 14 and the addition output (Ag 2) obtained from the HCl concentration measuring device (high speed) 15. (The above formula (1)).

[HCl concentration measuring device (low-speed response, simulating ion electrode type)]
T1 = Ta + Tb (11)
T1: Delay time of simulation reaction system of HCl concentration measuring device (low speed) (sec)
Ta: Facility delay time (sec) [30 sec setting]
Tb: Measurement delay time (sec) of HCl concentration measuring device (low speed)
Tb = Tbα + Tbβ (12)
Tbα: Exhaust gas sampling time (sec) of HCl concentration measuring device (low speed)
[390sec setting]
90% response time (sec) of Tbβ: HCl concentration measuring instrument (low speed)
[180sec setting]
Tbβ = 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 output concentration (ppm) of the previous measurement device (before Ts (sec))

[HCl concentration measuring instrument (high-speed response)]
T2 = Ta + Tc (15)
T2: Simulation reaction system delay time (sec) of HCl concentration measuring instrument (high speed)
Ta: Facility delay time (sec) [30 sec setting]
Tc: Measurement delay time (sec) of HCl concentration measuring device (high speed)
For the measuring instrument with a short measurement delay time, only Tc was changed.

  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.

The results of studying various control methods in this simulation reaction system are shown below.
In addition, the average particle diameter of the fine powder baking soda used in the following Examples 1-12 is 5-30 micrometers. Moreover, the HCl concentration measuring instrument 14 used in Examples 1 to 12 is based on the ion electrode method.

[Comparative Example 1]
Using the inlet HCl concentration shown in FIG. 9, the PID control method “P (proportional) is based on the HCl concentration measured only by the HCl concentration measuring device (low speed) 14 (measuring device measurement delay time meter 9.5 minutes) in the simulation. (Gain) = 100%, I = 0.1 sec, D = 0.1 sec, additive amount output lower limit 200 kg / h, additive amount output upper limit 480 kg / h ”, control target value (SV) of outlet HCl concentration to 200 ppm Set and 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.

  According to Comparative Example 1, the maximum value of 1-hour average HCl, which is often used as an acid gas emission control value, was 234 ppm, and the instantaneous maximum was 416 ppm.

[Comparative Example 2]
Control was performed in the same manner as in Comparative Example 1 except that feedback control was performed based on the HCl concentration measured only with the HCl concentration measurement device (high speed) 15 (measurement device measurement delay time 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. 11 shows the behavior of the amount of fine powdered baking soda added and the bag filter outlet HCl concentration during this control.

  As in Comparative Example 2, when feedback control is performed using only the high-speed response HCl concentration measuring device (high speed) 15 with a small measurement delay, it is predicted that the change in the addition amount of the alkali agent and the change in the outlet HCl concentration will occur instantaneously. It was done. However, hunting occurred due to fluctuations in the addition of alkaline agent, and the maximum HCl value per hour average was 227 ppm, and the instantaneous maximum was 425 ppm.

[Examples 1 to 5]
Based on the HCl concentration measured by the HCl concentration measuring device (low speed) 14 (measuring device measurement delay time meter 9.5 minutes) in the simulation, the PID control method “P (proportional gain) = 100%, I = 0.1 seconds. , D = 0.1 second, additive amount output lower limit 200 kg / h, additive amount output upper limit 480 kg / h ", the control value (SV) of the HCl concentration at the outlet is set to 200 ppm and feedback control is performed, and the HCl concentration Based on the HCl concentration measured by the measuring device (high speed) 15, the control target value (SV) at the outlet was set to 200 ppm with the same setting, and the addition output subjected to feedback control was added to perform feedback control.

  The measuring device measurement delay time of the HCl concentration measuring device (high speed) 15 is 2 seconds for Example 1, 1 minute for Example 2, 3 minutes for Example 3, 5 minutes for Example 4, and 5 for Example 5. It was 7 minutes.

  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. Moreover, the behavior of the fine powder baking soda addition amount and bag filter exit HCl concentration at the time of this control is shown in FIGS.

  According to Examples 1-5, the addition output calculated based on the measurement signal of the at least 2 acid gas measuring apparatus from which measurement delay time differs is calculated, and acid gas stability is calculated by calculating the addition amount of the alkaline agent. Processing is possible.

  Example 1 is the result of feedback control combining a measurement instrument measurement delay time (9.5 minutes) and a measurement instrument measurement delay time of 2 seconds (instantaneous), but unlike Comparative Examples 1 and 2. It was possible to add an appropriate alkaline agent according to the target value of the HCl concentration at the outlet. Moreover, as a result of appropriate chemical injection control, the hourly average value of the outlet HCl concentration under this condition was 193 ppm and the instantaneous maximum was 272 ppm, and as a result, it was found that the control method was easy to manage with little fluctuation in the outlet HCl concentration.

  Moreover, the measurement device measurement delay time is improved as compared with Comparative Example 1 and Comparative Example 2 even at 7 minutes (Example 5), and the measurement delay time may be different. However, as a chemical injection management, the shorter it is, the more effective it is for the acid gas stabilization treatment, and it is preferable that it is 7 minutes or less, more preferably 3 minutes or less.

[Example 6]
In the simulation, 50% output restriction is applied to the addition output that is feedback-controlled based on the HCl concentration measured by the HCl concentration measuring device (low speed) 14 (measuring device measurement delay time 9.5 minutes), and the HCl concentration measuring device (high speed) ) The addition output subjected to feedback control based on the HCl concentration measured at 15 (measuring instrument measurement delay time 2 seconds) was added without limitation (100%), 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, FIG. 17 shows the behavior of the added amount of fine powdered sodium bicarbonate and the bag filter outlet HCl concentration during this control.

[Example 7]
In the simulation, 50% output restriction is applied to the addition output that is feedback-controlled based on the HCl concentration measured by the HCl concentration measuring device (low speed) 14 (measuring device measurement delay time 9.5 minutes), and the HCl concentration measuring device (high speed) ) 50% output limit was added to the addition output that was feedback-controlled based on the HCl concentration measured at 15 (measuring instrument measurement delay time 2 seconds), 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, FIG. 18 shows the behavior of the added amount of fine baking soda and the bag filter outlet HCl concentration during this control.

  Here, as in Examples 6 and 7, the acidity when at least one restriction is applied to the upper limit of the addition output calculated based on the measurement signals of at least two acid gas measuring devices having different measurement delay times. The gas treatment result will be described.

  Example 6 is an example in which a 50% limit is applied to the addition output calculated from the measurement signal of the HCl concentration measuring device (low speed) 14. Further, Example 7 is an example in which 50% limitation is applied to both the addition outputs of the HCl concentration measuring device (low speed) 14 and the HCl concentration measuring device (high speed) 15. In any of the examples, it was found that the treatment level of HCl was almost the same as that of Example 1, and the addition amount was 271 to 300 kg / h, and the addition amount of the alkaline agent could be reduced as compared with Example 1 (311 kg / h).

[Example 8]
In the simulation, when feedback control is performed based on the HCl concentration measured by the HCl concentration measuring device (low speed) 14 (measuring device measurement delay time 9.5 minutes), when the 6-second average of the latest HCl concentration slope is positive, When the control target value (SV) is 180 ppm (SV-20 ppm) and the 6-second average of the slope of the latest HCl concentration is negative, the control target value (SV) is controlled to 220 ppm (SV + 20 ppm), and the added output is controlled to the HCl concentration. When feedback control was performed based on the HCl concentration measured with the measuring device (high speed) 15 (measuring device measurement delay time 2 seconds), the addition output controlled at a control target value (SV) of 200 ppm was added 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. 19 shows the behavior of the added amount of fine powdered sodium bicarbonate and the bag filter outlet HCl concentration during this control.

[Example 9]
In the simulation, when feedback control is performed based on the HCl concentration measured by the HCl concentration measuring device (low speed) 14 (measuring device measurement delay time 9.5 minutes), when the 6-second average of the latest HCl concentration slope is positive, When the control target value (SV) is 180 ppm (SV-20 ppm) and the 6-second average of the slope of the latest HCl concentration is negative, the control target value (SV) is set to 220 ppm (SV + 20 ppm), and the added output is controlled to 50%. The output is limited and the control output (SV) is controlled to 200 ppm when feedback control is performed based on the HCl concentration measured by the HCl concentration measuring device (high speed) 15 (measuring device measurement delay time 2 seconds). The output was limited, added, and feedback controlled.

  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. 20 shows the behavior of the amount of fine powdered baking soda added and the bag filter outlet HCl concentration during this control.

  Here, as in Examples 8 and 9, when the calculation is based on the measurement signals of at least two acid gas measuring instruments having different measurement delay times, the control target value is decreased when the latest gradient of HCl concentration is positive. When the latest HCl concentration slope is negative, the acid gas treatment result when the control target value is increased and the addition output by feedback is advanced will be described.

  In the eighth embodiment, the control target value (SV) is changed when trial calculation is performed based on the measurement signal of the HCl concentration measuring device (low speed) 14, and the calculated addition output and the measurement of the HCl concentration measuring device (high speed) 15 are performed. This is an example in which the addition output calculated based on the signal with the control target value of 200 ppm is added and feedback control is performed. Further, in Example 9, feedback is obtained by adding a 50% limit to both addition outputs calculated based on measurement signals of the HCl concentration measuring device (low speed) 14 and the HCl concentration measuring device (high speed) 15 in Example 8. Control.

  In Example 8, the instantaneous maximum HCl was reduced from 272 ppm to 248 ppm, particularly with the addition amount almost the same as in Example 1, and it was found that peak control was enhanced by this control method. Moreover, in Example 9, compared with Example 1, the peak maximum is enhanced to 255 ppm and the peak correspondence is strengthened, and the addition amount is reduced from 315 kg / h in Example 8 to 279 kg / h, and a balanced control is performed. I understood that I could do it.

  Hereinafter, Examples 10 to 12 will be described. In Examples 10-12, control by a step control method is performed instead of the PID control method.

Here, an outline of the step control method will be described. 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. In the tenth embodiment (FIG. 21), when the HCl concentration is between the SV control target value [control output start concentration (above output lower limit)] and SM1, the control output is output stepwise between LO and LM1. A 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 SM2 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).

[Example 10]
When feedback control is performed based on the HCl concentration measured by the HCl concentration measuring device (low speed) 14 (measuring device measurement delay time 9.5 minutes) in the simulation, the control target value (in this method, the alkaline agent The concentration of the control output added above the output lower limit is defined as SV), and the addition output controlled to 200 ppm and the HCl concentration measured by the HCl concentration measuring instrument (high speed) 15 (measuring instrument measurement delay time 2 seconds) When feedback control was originally performed, similarly, the control target value was set to 200 ppm in the step system control, and the controlled addition output was added and feedback control was performed (see FIGS. 8 and 21).

  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. 22 shows the behavior of the amount of fine powder baking soda added and the bag filter outlet HCl concentration during this control.

[Example 11]
When feedback control is performed based on the HCl concentration measured with the HCl concentration measuring device (low speed) 14 (measuring device measurement delay time 9.5 minutes) in the simulation, the 6-second average of the latest HCl concentration gradient in the step-type control is performed. When the control target value (SV) is positive, the control target value (SV) is 180 ppm (SV-20 ppm), and when the 6-second average of the latest HCl concentration slope is negative, the control target value (SV) is controlled to 220 ppm (SV + 20 ppm). Similarly, when feedback control is performed based on the HCl concentration measured by the HCl concentration measuring device (high speed) 15 (measuring device measurement delay time 2 seconds), the control target value is set to 200 ppm and controlled in the step method control. The addition output was added and feedback control was performed (see FIGS. 8 and 23).

  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. 24 shows the behavior of the amount of fine powdered baking soda added and the bag filter outlet HCl concentration during this control.

[Example 12]
When feedback control is performed based on the HCl concentration measured with the HCl concentration measuring device (low speed) 14 (measuring device measurement delay time 9.5 minutes) in the simulation, the 6-second average of the latest HCl concentration gradient in the step-type control is performed. When the control target value (SV) is positive, the control target value (SV) is 180 ppm (SV-20 ppm), and when the 6-second average of the latest HCl concentration slope is negative, the control target value (SV) is controlled to 220 ppm (SV + 20 ppm). When the output is limited to 50% and feedback control is performed based on the HCl concentration measured by the HCl concentration measuring device (high speed) 15 (measuring device measurement delay time 2 seconds), the control target value is similarly used in the step method control. Was set to 200 ppm and added to the controlled addition output with a 50% output limit, and feedback control was performed (see FIG. 8 and FIG. 8). Reference 23).

  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. 25 shows the behavior of the amount of fine powdered sodium bicarbonate added and the bag filter outlet HCl concentration during this control.

  Examples 10 to 12 are examples in which feedback control is performed by a step method. The step method is a measure for preventing an addition loss by providing a plurality of output restrictions on the upper limit value of the addition output.

  As a result of control based on the step control method, Examples 10 to 12 were compared with Comparative Example 1 and Comparative Example 2 (average for one hour: 227 to 234 ppm, instantaneous maximum: 416 to 425 ppm). Stable acid gas treatment performance with a maximum of 253 to 274 ppm is shown. Moreover, compared with Example 1, Example 8, and Example 9 (1 hour average 193-205 ppm, instantaneous maximum 248-272 ppm) controlled based on PID, 1 hour average (206-218 ppm, 253-274 ppm) Then, although the management performance of acid gas was a little inferior, it turned out that the addition amount was reduced to 272-297 kg / h with respect to 279-315 kg / h.

  The present invention can be implemented both in the PID method and in the step method, but it is considered that the PID method is effective when obtaining a stable treatment of acid gas from this result, and the step method is effective when obtaining an additive amount reduction effect. It was.

  Hereinafter, in describing Comparative Example 3 and Examples 13 to 16, which are actual machine examination results, the configuration of the acid gas treatment system 2 used in Comparative Example 3 and Examples 13 to 16 will be described.

  FIG. 26 is a block diagram showing the configuration of the acidic gas treatment system 2 in which fine baking soda is added to HCl that 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, an HCl concentration measurement device (ion electrode method) 24, and an HCl concentration measurement device (laser method) 25. ing. 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 (ion electrode method) 24 and the HCl concentration measuring device (laser method) 25 (PID control method). Or a 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 11. Moreover, the fine powder baking soda addition apparatus 26 adds a fixed quantity of fine powder baking soda to HCl in exhaust gas irrespective of the addition amount output value of the fine powder sodium bicarbonate calculated by the control device 11.

  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 method) 24 and the HCl concentration measuring device (laser method) 25 are provided with fine powdered baking soda accumulated on the bag filter 23 (fine powdered sodium bicarbonate remaining after reaction with HCl in the exhaust gas is put on the bag filter 23. The HCl concentration (accumulated bag filter outlet HCl concentration described later) after the reaction between the exhaust gas reaction and HCl after the exhaust gas reaction is measured, and an HCl concentration measurement signal is transmitted to the control device 21.

  The acidic 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 sodium bicarbonate appropriate.

  The HCl concentration measurement delay time of the HCl concentration measuring device (ion electrode method) 24 is longer than that of the HCl concentration measuring device (laser method) 25.

  In addition, as shown in FIG. 26, an HCl concentration measuring instrument (ion ion) is used so as to measure the HCl concentration (bag filter outlet HCl concentration) after the fine baking soda accumulated on the bag filter 23 reacts with HCl after the exhaust gas reaction. It is preferable to install an electrode system) 24 and an HCl concentration measuring device (laser system) 25. This is because fine powdered sodium bicarbonate remaining due to the reaction with HCl in the exhaust gas is accumulated on the bag filter 23, and this accumulated fine powdered sodium bicarbonate reacts with HCl after the exhaust gas reaction, so that the HCl concentration can be measured more accurately. Because.

[Comparative Example 3]
In an industrial waste incinerator, a laser-type HCl concentration measuring device (KLA-1 manufactured by Kyoto Electronics Industry) was installed between the outlet of the temperature reducing tower and the bag filter, and the inlet HCl concentration was measured. In addition, feedback control was performed with an oxygen conversion value that manages the emission reference value based on a signal measured by an ion electrode type HCl concentration measuring device (HL-36N manufactured by Kyoto Electronics Industry) at the bag filter outlet. The feedback addition output (SV 180 ppm) based on the SO ₂ concentration signal at the outlet was added to the addition output based on the HCl concentration. However, SO ₂ was not generated in this facility.

  Moreover, the alkaline agent which processes acidic gas added 8 micrometer fine baking soda [Kurita Kogyo Hypercer B-200] by the said 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. 27 shows the bag filter inlet HCl concentration, the bag filter outlet HCl concentration, and the amount of fine powdered sodium bicarbonate added (total of two addition devices). Further, FIG. 28 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.

  As previously indicated, the addition of fine baking soda was performed roughly and was a wasteful control in which the HCl concentration at the outlet varied greatly.

[Example 13]
In the same facility, an HCl concentration signal (oxygen conversion value) measured by an ion electrode type HCl concentration measuring device (HL-36N manufactured by Kyoto Electronics Industry) at the bag filter outlet and an HCl concentration measuring device by the laser method at the bag filter exit ( Feedback control was performed using an HCl concentration signal (oxygen conversion value) measured with KLA-1 manufactured by Kyoto Electronics Industry. Similarly, the feedback addition output (SV 180 ppm) based on the SO ₂ concentration signal at the outlet was added to the addition output based on the HCl concentration, but SO ₂ was not generated in this facility.

  Similarly, one addition device is used for 180 kg / h quantitative addition, and one is based on the outlet HCl concentration signal, “lower limit 20 kg / h upper limit 300 kg / h, PID control setting P (proportional gain) = 100% , I = 0.1 seconds, D = 0.1 seconds ”, and a 67% limit is added to both of the additive power calculated from the measurement signals of both the ion electrode type and laser type measuring instruments, and this is added. Separately from the control, feedback control was performed by adding 300 kg / h of 213 ppm or more to the facility management concentration of 215 ppm having an average value for one hour.

  FIG. 27 shows the bag filter inlet HCl concentration, the bag filter outlet HCl concentration, and the amount of fine powdered sodium bicarbonate added (total of two addition devices). In addition, FIG. 29 shows the behavior of the added amount of fine baking soda and the HCl concentration at the bag filter inlet / outlet when this control is performed.

[Example 14]
As in Example 13, an HCl concentration signal (oxygen conversion value) measured by an ion electrode type HCl concentration measuring device at the bag filter outlet and an HCl concentration measuring device by a laser method at the bag filter outlet (KLA-manufactured by Kyoto Electronics Industry). Feedback control was performed using the HCl concentration signal (oxygen conversion value) measured in 1). Similarly, the feedback addition output (SV 180 ppm) based on the SO ₂ concentration signal at the outlet was added to the addition output based on the HCl concentration, but SO ₂ was not generated in this facility.

  In addition, the control of the adding apparatus that performed the control is “lower limit is 20 kg / h, upper limit is 300 kg / h, PID control setting P (proportional gain) = 100%, I = 0.1 second, D = 0.1 second”. In addition, both the addition output calculated from the measurement signals of both measuring devices were added with a limit of 33%, and separately from this control, feedback control was performed to add 300 kg / h for an hourly average value of 213 ppm or more.

  FIG. 27 shows the bag filter inlet HCl concentration, the bag filter outlet HCl concentration, and the amount of fine powdered sodium bicarbonate added (total of two addition devices). Further, FIG. 30 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.

  In both Example 13 and Example 14, the change in the HCl concentration at the outlet is less than that in Comparative Example 3, and control can be performed with little addition loss. Further, the amount of the alkali agent added varies depending on the inlet HCl concentration, and is generally evaluated by an equivalent amount indicating the amount added per inlet HCl concentration. This addition equivalent was found to be reduced compared to the comparative example, and efficient addition was achieved.

  Examples 15 and 16 will be described below. In the fifteenth and sixteenth embodiments, control by the step control method is performed instead of the PID control method. The outline of the step control method is the same as that described in the tenth embodiment.

[Example 15]
In the same facility, an HCl concentration signal (oxygen conversion value) measured by an ion electrode type HCl concentration measuring device (HL-36N manufactured by Kyoto Electronics Industry) at the bag filter outlet and an HCl concentration measuring device by the laser method at the bag filter exit ( Feedback control was performed using an HCl concentration signal (oxygen conversion value) measured with KLA-1 manufactured by Kyoto Electronics Industry. Similarly, the feedback addition output (SV 180 ppm) based on the SO ₂ concentration signal at the outlet was added to the addition output based on the HCl concentration, but SO ₂ was not generated in this facility.

  Similarly, one unit is 180 kg / h quantitative addition, and one unit is a step system, and adds 50% to both of the addition outputs calculated from the measurement signals of both measuring instruments. Separately, when the average value for 1 hour is 213 ppm or more, feedback control of adding 300 kg / h was performed (see FIGS. 27 and 31).

  FIG. 27 shows the bag filter inlet HCl concentration, the bag filter outlet HCl concentration, and the amount of fine powdered sodium bicarbonate added (total of two addition devices). Further, FIG. 32 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.

  The fifteenth embodiment is an embodiment based on a step method. Compared with Comparative Example 3, fluctuations in the HCl concentration at the outlet are reduced, and control with little addition loss can be performed. This addition equivalent is reduced compared with the comparative example, and efficient addition has been achieved.

[Example 16]
In the same facility, an HCl concentration signal (oxygen conversion value) measured by an ion electrode type HCl concentration measuring device (HL-36N manufactured by Kyoto Electronics Industry) at the bag filter outlet and an HCl concentration measuring device by the laser method at the bag filter exit ( Feedback control was performed using an HCl concentration signal (oxygen conversion value) measured with KLA-1 manufactured by Kyoto Electronics Industry. Similarly, the feedback addition output (SV 180 ppm) based on the SO ₂ concentration signal at the outlet was added to the addition output based on the HCl concentration, but SO ₂ was not generated in this facility.

  In addition, one addition device is a high-reaction slaked lime (Tamakaruku ECO manufactured by Okutama Kogyo Co., Ltd.) with a specific surface area of 30 m2 / g or more, and the other is a step method. In addition to the control, 50% was added to both of the addition outputs calculated from the signal, and the feedback control was performed separately from this control to add 300 kg / h when the average value for 1 hour is 213 ppm or more (see FIGS. 27 and 31). .

  FIG. 27 shows the bag filter inlet HCl concentration, the bag filter outlet HCl concentration, and the amount of fine powdered sodium bicarbonate added. Moreover, FIG. 33 shows the behavior of the added amount of fine baking soda and the HCl concentration at the bag filter inlet / outlet when this control is performed.

  Example 16 is an example in which slaked lime and fine powdered sodium bicarbonate, which are relatively industrially inexpensive, are used in combination. Also in this method, the stable treatment effect of acid gas was 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 sodium bicarbonate addition apparatus 13 Bag filter 14 HCl concentration measuring instrument (low speed)
15 HCl concentration measuring device (high speed)

Claims (7)

Add an alkali agent to combustion exhaust gas containing acid gas, and measure the acid gas concentration after collecting dust. A processing method,
A first delay time is provided to measure the acid gas concentration after collecting the dust, and the measurement delay time due to the sampling time of the sample exhaust gas and the response time of the acid gas concentration measuring device is the first delay time. An acid gas concentration measurement device, and a second delay time provided to measure the acid gas concentration after collecting the dust, wherein the measurement delay time is a second delay time longer than the first delay time. Measuring the acid gas concentration of the same species with the acid gas concentration measuring device of
Calculating a first addition amount output value of the alkaline agent by a feedback calculation based on a measurement signal of the first acid gas concentration measuring device;
Calculating a second addition amount output value of the alkaline agent by a feedback calculation based on a measurement signal of the second acid gas concentration measuring device;
Feedback control of a value obtained by adding the first addition amount output value and the second addition amount output value as the addition amount of the alkaline agent ,
At least the step of calculating the second addition amount output value by feedback calculation performs output limitation on the addition output calculated from the measurement signal transmitted from the second acid gas concentration measurement device, and is smaller than the addition output. method of processing an acid gas having a value as engineering to the second amount output value. Add an alkali agent to combustion exhaust gas containing acid gas, and measure the acid gas concentration after collecting dust. A processing method,
The first acid gas concentration measuring device whose measurement delay time is the first delay time due to the sampling time of the sample exhaust gas and the response time of the acid gas concentration measuring device, and the acid gas after collecting the dust A step of measuring an acidic gas concentration of the same species by a second acidic gas concentration measuring device provided to measure a concentration, wherein the measurement delay time is a second delay time longer than the first delay time; ,
Calculating an addition amount output value of the alkaline agent by feedback calculation based on measurement signals of the first acid gas concentration measuring device and the second acid gas concentration measuring device ,
The step of calculating the added amount output value by feedback calculation,
Setting a control target value of the acid gas concentration transmitted from the second acid gas concentration measuring device;
A step of calculating an addition amount output value of an alkaline agent based on at least the measurement signal and the control target value,
Step of setting the control target value, and when the time rate of change of the acid gas concentration to be transmitted from the second acid gas concentration measurement device is a positive, transmitted from the second acid gas concentration measuring instrument Is a step of setting different control target values for each of the cases where the time change rate of the acidic gas concentration is negative,
The control target value set when the time rate of change of the acid gas concentration transmitted from the second acid gas concentration measuring device is positive is the value of the acid gas concentration transmitted from the second acid gas concentration measuring device. Smaller than the control target value set when the rate of time change is negative,
Step of calculating the amount output value of the alkaline agent, the amount the output value of the measuring signal and the alkaline agent, calculated based on the control target value is transmitted from the second acid gas concentration measuring instrument, wherein The step of adding an addition amount output value of an alkaline agent controlled based on a predetermined control target value when feedback control is performed based on the measurement signal transmitted from the first acid gas concentration measuring device . Processing method. The step of calculating the added amount output value by feedback calculation,
Setting a control target value of the acid gas concentration transmitted from the second acid gas concentration measuring device;
A step of calculating an addition amount output value of an alkaline agent based on at least the measurement signal and the control target value,
Step of setting the control target value, and when the time rate of change of the acid gas concentration to be transmitted from the second acid gas concentration measurement device is a positive, transmitted from the second acid gas concentration measuring instrument Is a step of setting different control target values for each of the cases where the time change rate of the acidic gas concentration is negative,
The control target value set when the time rate of change of the acid gas concentration transmitted from the second acid gas concentration measuring device is positive is the value of the acid gas concentration transmitted from the second acid gas concentration measuring device. time rate of change is less than the control target value to be set if it is negative, the processing method of the acid gases according to claim 1. Add an alkali agent to combustion exhaust gas containing acid gas, and measure the acid gas concentration after collecting dust. A processing method,
A first delay time is provided to measure the acid gas concentration after collecting the dust, and the measurement delay time due to the sampling time of the sample exhaust gas and the response time of the acid gas concentration measuring device is the first delay time. An acid gas concentration measurement device, and a second delay time provided to measure the acid gas concentration after collecting the dust, wherein the measurement delay time is a second delay time longer than the first delay time. Measuring the acid gas concentration of the same species with the acid gas concentration measuring device of
Calculating a first addition amount output value of the alkaline agent by a feedback calculation based on a measurement signal of the first acid gas concentration measuring device;
Calculating a second addition amount output value of the alkaline agent by a feedback calculation based on a measurement signal of the second acid gas concentration measuring device;
Feedback control of a value obtained by adding the first addition amount output value and the second addition amount output value as the addition amount of the alkaline agent ,
The step of calculating the first addition amount output value by feedback calculation,
Performing a plurality of stages of output restriction according to a first measurement signal by the first acid gas concentration measuring instrument,
When the first measurement signal is less than or equal to a predetermined limit value, a first-stage output restriction is performed according to the first measurement signal, and a first-stage output restriction is performed according to the first measurement signal. In response to the output value as the first addition amount output value,
When the first measurement signal is greater than or equal to a predetermined limit value, a second stage output limit is performed according to the first measurement signal, and a value output according to the second stage output limit is set. Outputting as the first addition amount output value,
The step of calculating the second addition amount output value by feedback calculation,
Include performing output restriction of a plurality of steps in accordance with the second measurement signal by the second acid gas concentration measuring device,
When the second measurement signal is equal to or less than a predetermined limit value, first-stage output restriction is performed according to the second measurement signal, and first-stage output restriction is performed according to the second measurement signal. In response to the output value as the second addition amount output value,
When the addition output is equal to or greater than a predetermined limit value, a second-stage output restriction is performed according to the second measurement signal, and a second-stage output restriction according to the second measurement signal is performed. A method for treating acidic gas, comprising a step of outputting an output value as the second addition amount output value . The method for treating acidic gas according to any one of claims 1 to 4 , wherein the alkaline agent is fine powder sodium bicarbonate having an average particle size of 5 to 30 µm. The processing method of the acidic gas of Claim 5 which uses together the other alkaline agent different from the said fine powder baking soda. The other alkali agent, hydrated lime, sodium hydroxide, magnesium hydroxide, magnesium oxide, claim 6 is at least one alkali agent, sodium carbonate, sodium sesquicarbonate, selected from the group consisting of natural soda, and coarse sodium bicarbonate The processing method of the acidic gas as described in 2.

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