JP2020179353A - Waste incineration system - Google Patents

Abstract

To provide a waste incineration system capable of controlling more easily discharge of dioxins in exhaust gas.SOLUTION: A waste incineration system includes dust collection means, treatment agent supply means provided on the upstream of the dust collection means, for supplying a treatment agent, hydrogen chloride concentration measurement means for measuring continuously a hydrogen chloride concentration in exhaust gas, and treatment agent supply control means for controlling supply of the treatment agent. In the waste incineration system, the treatment agent contains an adsorbent having a function for adsorbing dioxins in exhaust gas, and the treatment agent supply control means controls a supply period of the treatment agent based on a mean value of the hydrogen chloride concentration.SELECTED DRAWING: Figure 1

Description

The present invention relates to a waste incineration system.

Based on the Act on Special Measures concerning Countermeasures against Dioxins, from December 1, 2002, emission standards for the concentration of dioxins in exhaust gas were imposed on all waste incineration systems according to the scale of the facility. In order to suppress the generation of harmful substances such as dioxins, measures such as suppressing the synthesis of dioxins are taken by maintaining a high temperature combustion state in each waste incineration system and promptly reducing the temperature after incineration. There is. In the unlikely event that dioxin is resynthesized in the temperature reduction process, it should be combined with a neutralizing agent (alkaline agent such as slaked lime) to neutralize acid gas such as hydrogen chloride generated by combustion. An adsorbent (activated carbon or the like) having a function of adsorbing dioxin or the like is supplied as a treatment agent from the upstream side of the dust collecting means. As a result, in the dust collecting means, hydrogen chloride is neutralized by the neutralizing agent, and dioxins are adsorbed by the adsorbent. Ultimately, hydrogen chloride and dioxins are recovered as soot and dust, so that the discharge of hydrogen chloride and dioxins into the atmosphere is suppressed.

Normally, each waste incineration system has a standard value for carrying in incineration in advance, and within that range, the generation of harmful substances is controlled by constantly supplying a certain amount of treatment agent. However, if an unexpected incinerated product is mixed in unexpectedly, it is necessary to increase the supply amount of the treatment agent.

In order to adjust the supply amount of this treatment agent, it is necessary to constantly monitor harmful substances in the exhaust gas. For example, hydrogen chloride can be constantly monitored using a laser gas analyzer and can be detected with high accuracy. However, dioxins are trace substances and it is difficult to detect them directly at all times.
Non-Patent Document 1 describes an example of a method for constantly monitoring dioxins in exhaust gas. As shown in Non-Patent Document 1, there is a high correlation between the concentrations of carbon monoxide and hydrogen chloride, which are currently required to be constantly monitored in waste incineration systems, and the concentrations of dioxins. I can't. Therefore, among dioxin precursors such as benzene chloride and phenol chloride, those that can be measured at all times are measured using an analytical instrument, or dioxins are sampled for a long period of 2 weeks to 1 month and the sample is used. A method for quantitative analysis of dioxins has been developed and put into practical use.

Takafumi Horie, Monthly Resources and Environment Measures November 2003 issue "Constant monitoring of dioxins in exhaust gas-Recent measurement technology trends and their utilization" Vol. 39 No. 13 p. 120-126

However, the technique shown in Non-Patent Document 1 requires an expensive analytical instrument such as gas chromatography even if the precursor can be directly measured at all times. Further, even with the method of long-term sampling of dioxins in the exhaust gas, it takes about 3 weeks to determine the average concentration of dioxins, so it is not possible to monitor dioxins during that period.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a waste incineration system capable of more economically and easily controlling the emission of dioxins in exhaust gas.

As a result of diligent studies by the present inventors, it was found that the dioxin concentration does not correlate with the measured value of the hydrogen chloride concentration, but shows a high correlation with the average value of the hydrogen chloride concentration. Furthermore, it was found that there was a time lag between the two.
The waste incineration system according to the embodiment of the present invention provided based on such knowledge includes a dust collecting means, a treatment agent supply means for supplying a treatment agent provided on the upstream side of the dust collecting means, and exhaust gas. In a waste incineration system including a hydrogen chloride concentration measuring means for continuously measuring the hydrogen chloride concentration in the waste incineration system and a treating agent supply controlling means for controlling the supply of the treating agent, the treating agent adsorbs dioxins in the exhaust gas. The treatment agent supply control means, which includes an adsorbent having a function of causing the treatment agent to be added, is characterized in that the period during which the treatment agent is increased is controlled based on the average value of the hydrogen chloride concentration.

Further, the treatment agent supply control means is characterized in that the amount of the treatment agent is increased when the average value exceeds the upper limit of the average value of the hydrogen chloride concentration.

Further, the period for increasing the amount of the treatment agent is predetermined based on the average value and the dioxin concentration.

The period for which the treatment agent is increased is characterized in that it is predetermined based on the correlation between the average value and the dioxin concentration.

The correlation is characterized by being based on the correlation between the mean value and the concentration of at least one dioxin in the exhaust gas or in soot and dust.

The average value is the average value of the measurement data of the hydrogen chloride concentration for 30 minutes or more and 3 days or less.

According to the present invention, it is possible to control the emission of dioxins in the exhaust gas by a simpler method, and it is possible to provide a waste incineration system capable of reducing the amount of the discharged treatment agent.

It is a schematic diagram which shows the waste incineration system. It is a figure which shows the adsorbent supply control method. It is a figure which shows the influence on the hydrogen chloride concentration in exhaust gas by a high chlorine incineration product. It is a graph which shows the behavior of the average value (1 hour average value) of hydrogen chloride concentration by a high chlorine incineration product. It is a figure which shows the correlation of the dioxin concentration in the exhaust gas and the hydrogen chloride concentration (24-hour average value) in the exhaust gas. (A) shows the correlation between the dioxin concentration and the hydrogen chloride concentration 4 days ago, and (b) shows the correlation between the dioxin concentration and the hydrogen chloride concentration the day before. It is a figure which shows the correlation of the dioxin concentration in soot and dust, and the hydrogen chloride concentration (24-hour average value) in exhaust gas. (A) shows the correlation between the dioxin concentration and the hydrogen chloride concentration 4 days ago, and (b) shows the correlation between the dioxin concentration and the hydrogen chloride concentration the day before. It is a graph which shows the relationship of each correlation coefficient between the hydrogen chloride concentration (24-hour average value) in exhaust gas, and the concentration of dioxins in exhaust gas and soot and dust. It is a figure which shows the correlation of the dioxin concentration in exhaust gas and soot and dust. It is an image diagram which shows the relationship between the time lag of the average value of hydrogen chloride concentration and the concentration of dioxins (predicted value), and the period of increasing the amount of adsorbent. It is a figure which shows the neutralizing agent supply control method. It is a conceptual diagram of dioxin suppression.

An outline of a waste incineration system capable of controlling dioxins in exhaust gas according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view showing a system of a waste incineration system 10 according to an embodiment of the present invention. The dotted arrows (between 11-6 and 6-7 in FIG. 1) indicate the supply of the treatment agent and the discharge route of soot and dust by the exhaust gas treatment means. Further, a thick arrow (between 12 and 20-11 in FIG. 1) indicates a signal path for measuring and calculating the hydrogen chloride concentration data in the exhaust gas and controlling the processing agent supply device 11.

Normally, the incinerated material to be put into the receiving hopper 1 is checked in advance for high chlorine content, but even at the time of actual delivery, a sample is taken to check for high concentration chlorine content. Is required. If a high chlorine concentration is confirmed, measures will be taken not to accept the incinerated material. However, this does not apply if it is judged that the amount received is small and the total amount of incineration is not affected.

The incinerated material put into the receiving hopper 1 is sent to the primary combustion furnace 2. Then, the gas temperature in the primary combustion furnace 2 is maintained at 850 ° C. or higher, the instantaneous measurement value of carbon monoxide concentration (every 5 seconds) is measured, and the operation is controlled so that the concentration is 100 ppm or less. As a result, the decomposition of dioxin is promoted. The carbon monoxide concentration may be measured at any place after the primary combustion furnace 2, and may be measured together with the measurement of the hydrogen chloride gas concentration in the chimney 9 described later, for example.
The primary combustion furnace 2 to the secondary combustion furnace 3 are connected by a pipe, and the gas in the secondary combustion furnace is exhausted by the pipe while maintaining the outlet combustion gas temperature of the secondary combustion furnace 3 at 850 ° C. or higher. Sent to 4. In the waste heat boiler 4, heat is recovered from the exhaust gas and rapidly cooled to 190 ° C. or lower in the quenching tower (temperature reducing treatment) 5 to prevent the resynthesis of dioxins.

The gas discharged from the quenching tower 5 passes through the pipe in a state of containing dust and is sent to the upstream side of the dust collector 6. Since there is a possibility that harmful substances such as dioxins are resynthesized in the gas in addition to hydrogen chloride gas, a certain amount of the treatment agent is constantly added from the treatment agent supply device 11 attached to the dust collector 6. Be supplied.
As the treatment agent, an alkaline agent (for example, slaked lime, baking soda) as a neutralizing agent is used to neutralize the acid gas component such as hydrogen chloride gas, and is adsorbed to adsorb dioxin. Agents (eg, activated carbon, artificial zeolite) are used. In this specification, slaked lime and activated carbon are mainly taken up and described, but the present invention is not limited thereto.

As the treatment agent, a neutralizing agent and an adsorbent mixed in advance at a predetermined ratio can be used. In this case, it is possible to use only one treatment agent supply device, and the system can be simplified. Further, as another embodiment, the neutralizing agent and the adsorbent can be used without being mixed. In this case, two supply devices are required for each, but there is an advantage that each supply amount, supply period, start of increase, etc. can be managed independently. In particular, in the present invention, the hydrogen chloride gas concentration is reduced in a relatively short time by adding a neutralizing agent, whereas the dioxin concentration tends to increase with a time lag even after the hydrogen chloride gas is reduced. It is based on the knowledge, and it is very effective that both treatment agents can be independently controlled so as to increase the dose at an effective timing and / or period, respectively.

In the dust collector 6, the gas containing dust that has entered from the upstream side is dust-collected and filtered by the bag filter. The dust is filled and collected in a soot and dust collection container 7 provided on the downstream side, and is processed by an outsourcer. The gas sent to the dust collector 6 contains acid gases such as sulfur oxides, nitrogen oxides, and hydrogen chloride, which are neutralized by a neutralizing agent, and dioxin and the like are adsorbents. Is adsorbed by the gas, and is filled and collected in the dust collection container 7.

The gas processed by the dust collector 6 is sent to the chimney 9 through a pipe by the attraction blower 8 and discharged to the outside of the system. A hydrogen chloride gas measuring device 12 is installed in the middle stage of the chimney 9 to continuously measure the hydrogen chloride concentration.
The location of the hydrogen chloride gas measuring device 12 is not limited to the chimney 9, and there is no particular problem in predicting the amount of dioxins generated regardless of the location after the quenching tower (temperature reduction treatment) 5. .. However, it is preferable from the viewpoint of simplification of the system to use the data acquired by the hydrogen chloride gas measuring device installed for measuring the hydrogen chloride gas discharged to the outside of the system. Specifically, it is preferable to install the hydrogen chloride measuring device after the dust collector (not including the dust collector) capable of measuring the hydrogen chloride gas concentration after neutralization with the treatment agent.

The hydrogen chloride gas measuring device 12 not only has a response speed as fast as about 2 seconds at the shortest than the conventional suction type gas concentration monitor, but also does not require a sampling device and can be directly attached to the measurement point, so that it can be directly attached to the measurement point in real time. A laser gas analyzer capable of measuring the concentration is preferable.
In the hydrogen chloride gas measuring device 12, the hydrogen chloride concentration is always measured at predetermined intervals. The hydrogen chloride gas concentration is measured every 2 seconds as an instantaneous value, for example, but is not limited to this. However, if the measurement interval is too short, the load on data handling becomes large, so every second or more is preferable. Although the instantaneous value and the measured value are basically the same, the term instantaneous value is mainly used as a term corresponding to the average value.

The treatment agent supply control device 20 is a device provided with an internal calculation means that links the hydrogen chloride gas measuring device 12 and the treatment agent supply device 11.
The treatment agent supply control device 20 has a function of controlling the amount and supply period of the adsorbent supplied from the treatment agent supply device 11 to the dust collector 6 in order to suppress dioxins, and a treatment for suppressing hydrogen chloride gas and the like. It has a function of controlling the amount and supply period of the neutralizing agent supplied from the agent supply device 11 to the dust collector 6. The treatment agent supply device 11 may be provided individually according to each function, but when a mixture is used as the treatment agent, the treatment agent is mixed and supplied to either dioxins or hydrogen chloride gas. Control. Further, each amount of the adsorbent and the neutralizing agent may be specified by any unit or concept such as weight, mass, and supply rate.
Hereinafter, the two functions included in the processing agent supply control device 20 will be described in detail.

<Dioxin suppression function of the treatment agent supply control device 20>
First, an outline of the method for suppressing dioxins according to the embodiment of the present invention will be described.
According to the present invention, the hydrogen chloride concentration and the dioxin concentration are measured in advance, and by using the increase period obtained from the correlation between the two, the incineration process is actually performed as a business (hereinafter referred to as "actual operation"). Makes it possible to suppress the concentration of dioxins only by measuring the concentration of hydrogen chloride. Explaining with reference to the conceptual flow of FIG. 11, the hydrogen chloride concentration and the dioxin concentration are measured in advance before the actual operation. Of these, the hydrogen chloride concentration is averaged (calculated as an average value) to determine the change over time in the smoothed hydrogen chloride concentration. Then, the increase period obtained through the correlation processing between the smoothed hydrogen chloride concentration and the dioxin concentration is set as a specified value for actual operation. The details of the increase period will be described later. By using the specified value including the increase period during actual operation and controlling the amount of adsorbent by the treatment agent supply control device 20, it is possible to suppress the generation of dioxins only from the hydrogen chloride concentration measured during actual operation. It will be possible.

Subsequently, the specified values stored in advance in the treatment agent supply control device 20 during the actual operation will be described in detail.
In the treatment agent supply control device 20, the normal amount of the adsorbent, the period for averaging the predetermined hydrogen chloride concentration measurement value (hereinafter, may be referred to as “average period”), and the period for increasing the amount of the adsorbent (hereinafter, hereinafter). Information on the "increase period"), the preset average upper limit of the hydrogen chloride concentration, and the amount of the adsorbent to be increased are stored as specified values.

The normal amount of the adsorbent is the amount of the adsorbent that is constantly supplied to the dust collector 6. Since a certain amount of hydrogen chloride gas and dioxins may be generated in any waste incinerator, a certain amount of adsorbent is always supplied in advance to deal with an unexpected situation. If this amount is large, the risk of dioxins dissipating out of the system can be reduced, but on the other hand, the amount of soot and dust to be treated increases, which is not appropriate in terms of cost. Therefore, the optimum amount is set in advance. Since the normal amount of the adsorbent is a unique value depending on each incineration system, it is set according to the system.
In a waste incineration system in which a fixed amount of adsorbent is not constantly supplied, the normal amount of adsorbent may be unnecessary or set to zero.

The period for averaging the measured hydrogen chloride concentration is the averaging period for calculating the average instantaneous value of the measured hydrogen chloride concentration. The inventors have found that the correlation between the dioxins concentration and the instantaneous value of hydrogen chloride concentration is low, but shows a correlation with the average value. It is considered that this is because the measured value of hydrogen chloride concentration fluctuates rapidly in a short period of time and is not suitable for comparison with the measured value of dioxin concentration showing long-period fluctuation.
If the averaging period for obtaining the average value is short, the influence of the short cycle of the hydrogen chloride concentration is strongly exerted. Therefore, at least 30 minutes or more is preferable, and 1 hour or more is more preferable. Further, if it is too long, it is difficult to obtain a good correlation, so that at least 3 days or less, preferably 2 days or less is suitable. In particular, it is preferable to match the routine cycle of the actual incineration work, and for example, when the incineration work is performed in a 24-hour routine, the 24-hour average is optimal. For example, when the worker changes at 8 o'clock, the 24-hour average value from 8 o'clock on the previous day to 8 o'clock on the current day is used. Alternatively, the 24-hour average value from 0 to 24:00 on the previous day may be used regardless of the worker shift time.
It should be noted that the measurement interval of the hydrogen chloride concentration does not need to be several seconds only for the measure of suppressing dioxins, and for example, it can be set to about 10 minutes depending on the averaging period.

Next, the period for increasing the amount of the adsorbent will be described.
It was found that due to the diligent efforts of the present inventor, there is a time lag of several days in the correlation between both parameters (mean value of dioxin concentration and hydrogen chloride concentration), and the dioxin concentration increases after the average value of hydrogen chloride concentration increases. was gotten. The reason for this is not clear, but one factor is that it takes several days to resynthesize dioxins. In addition, as another factor, it cannot be denied that dioxins and the like adhering to pipes and dust collectors may have been peeled off after a few days. In any case, if this time lag is used, it is possible to effectively suppress dioxins based on the measured value (average value) of hydrogen chloride concentration. Therefore, at least a period exceeding this lime lag is set as a period for increasing the amount of the adsorbent, and the adsorbent is supplied from the treatment agent supply device 11 to the dust collector 6 over the period. Since this time lag may be a characteristic peculiar to each waste incineration system, it is obtained in advance in each waste incineration system.
Specifically, in order to obtain information on the period for increasing the amount of the adsorbent, it is collected by the concentration of dioxins contained in the gas discharged from the chimney 9 or the dust collection container 7 on the downstream side of the dust collector 6 together with the concentration of hydrogen chloride gas. At least one of the dioxins concentration contained in the dust is measured in advance (“pre-measurement” in FIG. 11). It is important to measure the hydrogen chloride concentration sufficiently ahead of the measurement date of the dioxin concentration. It is desirable to measure the hydrogen chloride concentration at least 5 days before, preferably 1 week or more before.
Next, the average value of the hydrogen chloride concentration for each set averaging period is calculated, and the change with time of the average value is obtained (“calculation of the average value of hydrogen chloride concentration” in the figure. Then, the average value as a time function The correlation with the measured value of dioxin concentration is calculated (“correlation processing” in the figure), and the time lag between the two is calculated. Finally, the calculated time lag is appropriately added to the period for which the safety rate is obtained, and the amount of the adsorbent is increased. The period.

Subsequently, the flow of control of the dioxin suppression function by the treatment agent supply control device 20 will be described. FIG. 2 is an example showing the flow of control, and will be described with reference to FIG.
The treatment agent supply control device 20 automatically performs the treatment agent when the average value of the hydrogen chloride gas concentration measured by the hydrogen chloride gas measuring device 12 rises and exceeds the preset average value upper limit of the hydrogen chloride concentration. The processing agent supply device 11 is controlled so that the amount of the adsorbent charged from the supply device 11 into the dust collector 6 is increased according to the preset amount of the adsorbent to be increased. As a method of increasing the amount of the adsorbent, there are a method of increasing the amount of the adsorbent at one time, a method of increasing the frequency of the addition, a method of combining them, and a method of changing various operating conditions.
The adsorbent maintains the increased amount until the preset amount increasing period of the adsorbent elapses (“adsorbent increasing treatment” in FIG. 2). Then, when it is confirmed that the average value of the measured hydrogen chloride concentrations is below the upper limit of the average value after the elapse of the increase period, the amount of the adsorbent is reduced (“adsorbent reduction treatment” in FIG. 2). For example, by setting the weight loss amount to the same amount as the weight increase amount, the normal amount of the adsorbent set in advance is returned, but by making the weight loss amount smaller than the weight increase amount, it is possible to gradually return to the normal amount.

If the average value of the hydrogen chloride gas concentration for a predetermined period exceeds the upper limit value again during the increase period of the adsorbent, the increase period of the treatment agent should be extended for a period equivalent to the increase period from that point. In that case, further increasing the amount, combining these, and the like are one effective embodiment from the viewpoint of safety.
The upper limit of these average values and the amount of the adsorbent to be increased can be any value, for example, 120 ppm. In addition, a more suitable value can be obtained by actually artificially adding an incinerated product having a high chlorine concentration and attempting an experiment in which the upper limit of the average value and the amount of the adsorbent added are changed in a plurality of patterns.
The treatment agent supply control device 20 may be a device integrated with the hydrogen chloride gas measuring device 12 or the treatment agent supply device 11.

<Hydrogen chloride concentration suppression function of the treatment agent supply control device 20>
The treatment agent supply control device 20 stores information on the normal amount of the neutralizing agent, the upper limit of the instantaneous value of the hydrogen chloride gas concentration provided in advance, and the amount of the neutralizing agent increased.
The normal amount of the neutralizing agent is the amount of the neutralizing agent that is constantly supplied to the dust collector 6.
The upper limit of the instantaneous value of the hydrogen chloride gas concentration set in advance is the hydrogen chloride gas concentration voluntarily set for each treatment facility.
The amount of the neutralizing agent increased is the amount of the neutralizing agent that is increased when the measured hydrogen chloride gas concentration exceeds the upper limit of the instantaneous value of the hydrogen chloride gas concentration.
Unlike the measures to suppress dioxin, hydrogen chloride gas reacts quickly with the neutralizing agent, so the amount of neutralizing agent should be increased as soon as it is confirmed that the measured value of hydrogen chloride gas concentration exceeds the upper limit of the instantaneous value of hydrogen chloride gas concentration. If this is done, hydrogen chloride gas can be quickly reduced.
In addition, the final stage of the neutralizing agent increasing state can be sufficiently effective in setting the measured value of the hydrogen chloride gas concentration as the time when the measured value falls below the upper limit of the instantaneous value. FIG. 10 shows an aspect of the neutralizing agent supply control method in a PAD diagram.

Further, the upper limit of the instantaneous value can be set to a value different from the upper limit of the average value of the hydrogen chloride concentration for the purpose of suppressing dioxins. In general, the upper limit of the instantaneous value is higher than the upper limit of the average value because the variation of the instantaneous value of the average value is smoothed.

Summarizing the above, in order to suppress hydrogen chloride gas, the start and end of increasing the amount of the neutralizing agent are determined based on the hydrogen chloride gas concentration measurement data (instantaneous value) that is affected by the short cycle. On the other hand, for measures to suppress dioxins, the start and end of increasing the amount of adsorbent are determined based on the data (mean value) from which the effects of short cycles are removed. In particular, the final stage is characterized in that it is determined based on the correlation between the average value of hydrogen chloride concentration and the concentration of dioxins.
When the purpose is to suppress both the hydrogen chloride gas concentration and the dioxins by using a treatment agent in which a neutralizing agent and an adsorbent are mixed, both control methods shown in FIGS. 2 and 10 are used. May be combined as appropriate.

Hereinafter, the waste incineration system according to the embodiment of the present invention, which enables control of the dioxin concentration so as not to exceed a specified value even when dioxins are resynthesized, will be further described with reference to Examples.

First, the restrictions on the acceptance of high chlorine concentration incineration products that cause the generation of dioxins, which are carried out in the waste incineration system used in this example, will be described. In the waste incineration system used in this example, the chlorine content before acceptance was measured as much as possible for all the incinerated products so as not to accept the incinerated products having a high chlorine content.

In this waste incineration system, the chlorine concentration was investigated twice, before and at the time of acceptance. Before acceptance, the chlorine concentration was measured by having the discharger provide information or provide a sample in advance. The measurement work differs depending on whether it is a liquid or a solid. The liquid matter is measured with a pH test paper, but when it is not possible to measure with the pH test paper due to the influence of oil or the like, the pH of the water remaining after burning the oil is measured. If the measurement paper shows a pH of 3 or less, it is judged that the chlorine concentration is too high for the waste to be treated by the waste incineration system, and it is not accepted in principle. In the case of solids, we requested that information be provided in advance to see if chlorine is contained based on information from the incineration plant. In principle, 1 wt% chlorine was unacceptable. However, this was excluded when it was judged that the amount received was small and the total amount of incineration was not affected.

In this embodiment, the waste incineration system shown in FIG. 1 was used. However, the amount of the treatment agent supplied in this example was kept constant, and the amount of the treatment agent was not increased or decreased during the experiment. Further, the incineration of the incinerated product is carried out so that the combustion gas temperature in the furnace is maintained at 850 ° C. or higher in the primary combustion furnace 2 in the incineration treatment step, and the inlet / outlet temperature up to the secondary combustion furnace 3 is also maintained at 850 ° C. or higher. At the same time, the residence time was secured for 2 seconds or more.
As a result of checking the combustion gas temperature of each combustion furnace, it is considered that dioxins are not generated up to the 3 outlets of the secondary combustion furnace, and as a result of further analysis of the superheat residue, it is found that all of them are below the detection limit and are detoxified. It could be confirmed. The lining and deposits in the secondary combustion furnace were also investigated, but dioxins and chlorine were below the detection limit.

From the survey results, it was estimated that dioxins are resynthesized near the temperature reduction treatment process from the waste heat boiler 4 to the quenching tower 5.

Regarding the hydrogen chloride gas derived from the high chlorine incineration material introduced into the waste incineration system, the gas discharged through the incentive blower 8 of the dust collector 6 was constantly monitored by the hydrogen chloride gas measuring device 12 in the middle stage of the chimney 9. Here, a laser gas analyzer (model name KLA) manufactured by Kyoto Electronics was used, and the measurement interval of the instantaneous value was set to 2 seconds.

As the treatment agent, highly reactive slaked lime (containing 15% activated carbon) of Chichibu Lime Industry Co., Ltd., an average particle size of 8 μm, a BET of 45 m2 / g, a pore volume of 0.2 cm2 / g, and CaO ≧ 72.5% were used. The treatment agent has the ability to suppress hydrogen chloride and dioxins.

The amount of the treatment agent supplied was 2.4 kg / h. Of these, the amount of slaked lime supplied was 2.0 kg / h and that of activated carbon was 0.4 kg / h. At this time, hydrogen chloride in the exhaust gas remained at about 100 ppm, and sulfur dioxide remained at about 15 ppm. Assuming that all the slaked lime added had reacted, the amount of hydrogen chloride caused by the added sludge was estimated to be 177 ppm.

In this embodiment, sludge, which is considered to contain about 4 to 5% of chlorine, is intentionally added as a high-chlorine incinerator twice, from 8:00 am to 11:00 am and from 01:00 pm to 4:00 pm. The hydrogen chloride concentration of the exhaust gas was increased, and it was verified whether the treatment agent supply control device 20 and the treatment agent supply device 11 operate properly when the voluntarily set upper limit of the instantaneous value of hydrogen chloride concentration of 200 ppm is exceeded.

The processing agent supply device 11 controls the supply amount by a gate valve and an electric rotary valve. In this embodiment, the basic operation was the intermittent operation of 4-second operation-60-second stop during normal operation, which had been verified in advance, but the treatment agent supply control device 20 exceeded the upper limit of the instantaneous value of hydrogen chloride concentration in the treatment agent supply control device 20. When is detected, the operating conditions are switched, and the setting is changed to intermittent operation for 16 seconds operation and 30 seconds stop.

FIG. 3 shows the change over time in the hydrogen chloride concentration. As shown in FIG. 3, the treatment agent supply control device 20 controls the treatment agent supply device 11 when the hydrogen chloride concentration in the exhaust gas starts to increase and exceeds 200 ppm 30 minutes after the start of sludge injection containing chlorine in the morning. The treatment agent was additionally supplied, and after a few seconds, it became 200 ppm or less. This operation occurred three times. In the afternoon, unlike in the morning, the hydrogen chloride concentration increased 19 times in total 19 times or more after 1 hour and 30 minutes after the start of sludge containing chlorine, but due to the effect of increasing the amount of treatment agent, all 45 Within seconds, the behavior of 200 ppm or less was repeated. Therefore, it was confirmed that the treatment agent supply control device 20 and the treatment agent supply device 11 can cope with the increase in the hydrogen chloride concentration.

When the instantaneous value data every 2 seconds in FIG. 3 is taken as the average value every hour as shown in FIG. 4, the effect of the treatment agent can be easily confirmed. Therefore, it is also possible to monitor and control the hydrogen chloride concentration in the exhaust gas by monitoring the 1-hour average value. However, since the instantaneous value is a smoothed value, the upper limit value is lower than the instantaneous value, and is preferably 120 ppm, for example.

Further, in this example, the concentration of dioxins in the exhaust gas and the concentration of dioxins in the soot and dust were measured 7 times in total. The measurement is performed by an external analysis organization, and the measurement of the concentration of dioxins in the exhaust gas is in accordance with JIS K0311 "Measurement method of the dioxins in the exhaust gas". It was carried out using the method specified by the Minister of the Environment based on the provisions of Item 1.

Next, the correlation coefficient R between the measured values of dioxins in the exhaust gas and soot and dust and the 24-hour average value of the hydrogen chloride concentration was determined. For the 24-hour average value of hydrogen chloride concentration, five kinds of average values from the average value of the previous day to the average value of 5 days ago were obtained, and the correlation coefficient R with the measured value of dioxins was obtained for each average value. .. The results are summarized in Table 1, and a graph showing the relationship between the measured values of dioxin in the exhaust gas and the correlation coefficient between the average values of hydrogen chloride concentrations on the previous day and 4 days ago is shown in Fig. 5 with the measured values of dioxin in soot and dust. FIG. 6 shows a graph showing the relationship of the correlation coefficient with the average value of hydrogen chloride concentration on the previous day and 4 days ago.

Using the data in Table 1, the horizontal axis is the date and the vertical axis is the correlation coefficient R. When the relationship between the dioxin concentration and the average value of hydrogen chloride concentration is graphed, the peak is high 4 days ago as shown in FIG. A correlation can be seen, but it was found that the correlation coefficient R was about 5 days before the measurement day. That is, it was confirmed that there was a time lag of 4 days in the correlation between the concentration of dioxins in the exhaust gas and the concentration of hydrogen chloride after averaging for 24 hours. Therefore, the period for increasing the amount of the treatment agent was set to at least 4 days or more, and 5 days or more in consideration of the safety factor. Since this time lag is a value that depends on each waste incineration system, it is necessary to obtain it in advance for each system.
Moreover, the correlation between the dioxin concentration and the hydrogen chloride concentration was similarly observed in both the dioxin concentration in the exhaust gas and the soot and dust. The correlation between the concentrations of dioxins in the exhaust gas and in the soot and dust was high as shown in FIG. 8 (correlation coefficient R = 0.8911).

From these results, in order to obtain information (information based on correlation) for taking measures to suppress dioxin concentration based on hydrogen chloride concentration, even the dioxin concentration measurement value in exhaust gas is the dioxin concentration measurement value in soot and dust. However, it was found that it can be used.

In the waste incineration system used in this experiment, during normal operation, a treatment agent of 2.4 kg / h (a mixture of a neutralizer containing 15% activated carbon in slaked lime and an adsorbent) was supplied to concentrate hydrogen chloride. Was constantly monitored, but based on the result of the time lag information based on the correlation performed in advance, the 24-hour average value of hydrogen chloride concentration from 0:00 to 24:00 on the previous day was set to the preset average upper limit (for example, 120 ppm). The dose of the treatment agent was maintained from the day when the excess was confirmed to 5 days after the correlation was expected to disappear in consideration of the time lag. If the measurement data of hydrogen chloride concentration every 2 seconds exceeds the upper limit of 200 ppm as an instantaneous value, the system automatically increases the amount of the treatment agent to cope with the increase in hydrogen chloride concentration. I was able to.

FIG. 9 shows an image of the time lag of the concentration of dioxins, which is predicted to increase after the average value of the hydrogen chloride concentration in the exhaust gas exceeds the upper limit of the average value. At the time when the instantaneous value of hydrogen chloride concentration exceeds the upper limit and the average value of hydrogen chloride concentration does not exceed the upper limit of the average value A, the amount of neutralizing agent that neutralizes acid gas components such as slaked lime is immediately increased. Will be done. Further, at the time point B when the average value of the hydrogen chloride concentration exceeds the upper limit of the average value, the amount of the adsorbent for adsorbing dioxins and the like is increased. Then, although it is an image, the supply is continued until the time point C (5 days later in this example) when the correlation between the dioxin concentration and the average value of the hydrogen chloride concentration disappears.

In Japan, due to the emission regulations for dioxins, incineration equipment equipped with advanced treatment technology and exhaust gas treatment equipment have been installed in existing furnaces that do not meet the standards, and the emission standard values have been achieved, but the investment amount is It is a heavy burden for waste disposal companies that have a waste incineration system. According to this waste incineration system, the introduction cost and maintenance cost can be kept low, and the amount of waste treatment agent can be reduced. Therefore, not only the dedicated waste incineration facility but also dioxins are expected to be generated. It can also be used as part of a production system.

1 ... Receiving hopper, 2 ... Primary combustion furnace, 3 ... Secondary combustion furnace, 4 ... Waste heat boiler, 5 ... Quench cooling tower (temperature reduction treatment), 6 ... Dust collector , 7 ... soot and dust collection container 8 ... attraction blower, 9 ... chimney, 10 ... entire waste incineration system, 11 ... treatment agent supply device, 12 ... hydrogen chloride gas measuring device, 20 ... Treatment agent supply control device

Claims (6)

A dust collecting means, a treatment agent supply means for supplying a treatment agent provided on the upstream side of the dust collecting means, a hydrogen chloride concentration measuring means for continuously measuring the hydrogen chloride concentration in exhaust gas, and the treatment agent. In a waste incineration system including a treatment agent supply control means for controlling supply.
The treatment agent includes an adsorbent having a function of adsorbing dioxins in the exhaust gas, and the treatment agent supply control means controls the period during which the treatment agent is increased based on the average value of the hydrogen chloride concentration. A waste incineration system featuring. The waste incineration system according to claim 1, wherein the treatment agent supply control means increases the amount of the treatment agent when the average value exceeds the upper limit of the average value of the hydrogen chloride concentration. The waste incineration system according to claim 1 and 2, wherein the period for increasing the amount of the treatment agent is predetermined based on the average value and the dioxin concentration. The waste incineration system according to claim 1 to 3, wherein the period for increasing the amount of the treatment agent is predetermined based on the correlation between the average value and the dioxin concentration. The waste incineration system according to claim 4, wherein the correlation is based on a correlation between the mean value and the concentration of at least one dioxin in exhaust gas or soot and dust. The waste incineration system according to claim 1 to 5, wherein the average value is an average value of measurement data of hydrogen chloride concentration of 30 minutes or more and 3 days or less.

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