JP7264372B2 - Waste incineration system - Google Patents

Description

The present invention relates to waste incineration systems.

Based on the Law Concerning Special Measures against Dioxins, from December 1, 2002, all waste incineration systems were required to comply with emission standards for dioxin concentration in the exhaust gas according to the scale of the facility. In order to suppress the generation of harmful substances such as dioxins, each waste incineration system maintains a high-temperature combustion state, and after incineration, measures are taken to suppress the synthesis of dioxins by rapidly reducing the temperature. there is In the unlikely event that dioxins are resynthesized during the temperature reduction process, they should be combined with a neutralizing agent (alkali agent such as slaked lime) to neutralize acid gases such as hydrogen chloride generated by combustion. An adsorbent (activated carbon or the like) having a function of adsorbing dioxins or the like is supplied as a processing agent from the upstream side of the dust collecting means. As a result, the hydrogen chloride is neutralized by the neutralizing agent and the dioxins are adsorbed by the adsorbent in the dust collecting means. Ultimately, the hydrogen chloride and dioxins are recovered as soot and dust, thereby reducing the release of hydrogen chloride and dioxins into the atmosphere.

Normally, each waste incineration system has a standard value for the amount of waste to be incinerated in advance, and within that range, a constant amount of processing agent is constantly supplied to control the generation of hazardous substances. However, if unexpected incinerators are mixed in, it is necessary to increase the amount of treatment agent supplied.

In order to adjust the supply amount of this processing agent, it is necessary to constantly monitor harmful substances in the exhaust gas. For example, hydrogen chloride can be constantly monitored and accurately detected using a laser gas analyzer. However, dioxins are trace substances and are difficult to always detect directly.
Non-Patent Document 1 describes an example of a constant monitoring method for dioxins in exhaust gas. As shown in Non-Patent Document 1, there is no high correlation between the concentration of carbon monoxide and hydrogen chloride, which are currently required to be constantly monitored in waste incineration systems, and the concentration of dioxins. can't Therefore, among dioxin precursors such as benzene chloride and phenol chloride, those that can be measured at any time should be measured using an analytical instrument, or dioxins should be sampled for a long period of two weeks to one month and the sample A method for quantitatively analyzing the

Yuji Horie, November 2003 issue of Monthly Resource and Environmental Measures "Constant Monitoring of Dioxins in Exhaust Gas - Recent Trends in Measurement Techniques and Their Applications" Vol. 39 No. 13 p. 120-126

However, the technique disclosed in Non-Patent Document 1 requires an expensive analytical instrument such as a gas chromatograph, even if it is possible to directly measure the precursor at all times. Also, even with the method of long-term sampling of dioxins in the exhaust gas, it takes about three weeks to determine the average concentration of dioxins, so dioxins cannot be monitored during that period.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a waste incineration system capable of controlling the emission of dioxins in exhaust gas more economically and simply.

As a result of diligent studies by the present inventors, it was found that the dioxin concentration did not show a correlation with the measured value of the hydrogen chloride concentration, but showed a high correlation with the average value of the hydrogen chloride concentration. Furthermore, it was found that there is a certain period of time lag between the two.
A waste incineration system according to an embodiment of the present invention, which is provided based on such findings, includes dust collection means, treatment agent supply means provided upstream of the dust collection means for supplying a treatment agent, exhaust gas In a waste incineration system comprising hydrogen chloride concentration measuring means for continuously measuring the concentration of hydrogen chloride in waste gas and treatment agent supply control means for controlling the supply of the treatment agent, the treatment agent adsorbs dioxins in the exhaust gas. The processing agent supply control means is characterized by controlling the period during which the amount of the processing agent is increased based on the average value of the hydrogen chloride concentration.

Further, the processing agent supply control means is characterized by increasing the amount of the processing agent when the average value exceeds the upper limit of the average value of the hydrogen chloride concentration.

Also, the period during which the processing agent is increased is predetermined based on the average value and the dioxin concentration.

The period during which the amount of the treating agent is increased 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 average value and at least one dioxin concentration in the exhaust gas or dust.

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

According to the present invention, it is possible to control the discharge 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 discharged treatment agent.

1 is a schematic representation of a waste incineration system; FIG. It is a figure which shows the adsorbent supply control method. It is a figure which shows the influence on the hydrogen-chloride density|concentration in exhaust gas by a high-chlorine incinerator. It is a graph which shows the behavior of the hydrogen chloride concentration average value (1 hour average value) by high chlorine incinerator. FIG. 3 is a diagram showing the correlation between the concentration of dioxins in exhaust gas and the concentration of hydrogen chloride in exhaust gas (average value for 24 hours). (a) shows the correlation between the dioxin concentration and the hydrogen chloride concentration four days before, and (b) shows the correlation between the dioxin concentration and the hydrogen chloride concentration on the previous day. FIG. 4 is a diagram showing the correlation between the concentration of dioxins in soot and dust and the concentration of hydrogen chloride in exhaust gas (24-hour average value). (a) shows the correlation between the dioxin concentration and the hydrogen chloride concentration four days before, and (b) shows the correlation between the dioxin concentration and the hydrogen chloride concentration on the previous day. 4 is a graph showing the relationship between correlation coefficients between the concentration of hydrogen chloride in exhaust gas (24-hour average value) and the concentrations of dioxins in exhaust gas and dust. FIG. 3 is a diagram showing the correlation between dioxin concentrations in exhaust gas and dust. FIG. 5 is an image diagram showing the relationship between the time lag between the average hydrogen chloride concentration and the dioxin concentration (predicted value) and the adsorbent amount increasing period. It is a figure which shows the neutralizer supply control method. It is a dioxin suppression conceptual diagram.

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

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

Regarding the incinerated materials put into the receiving hopper 1, it is usually checked in advance whether there is a high chlorine content, but when actually carrying in, a sample is taken to check whether there is a high concentration of chlorine. 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 the received amount is small and it is judged that the impact on the overall incineration amount is small.

Incinerated materials put into the receiving hopper 1 are sent to the primary combustion furnace 2 . Then, the gas temperature in the primary combustion furnace 2 is maintained at 850° C. or higher, and the carbon monoxide concentration instantaneous measurement value (every 5 seconds) is measured, and the operation is managed so that the concentration is 100 ppm or less. This promotes the decomposition of dioxins. The measurement of the carbon monoxide concentration may be performed at any place after the primary combustion furnace 2, for example, in a chimney 9, which will be described later, together with the measurement of the hydrogen chloride gas concentration.
The primary combustion furnace 2 to the secondary combustion furnace 3 are connected by piping, and while maintaining the temperature of the combustion gas at the outlet of the secondary combustion furnace 3 at 850 ° C. or higher, the gas in the secondary combustion furnace is discharged to the waste heat boiler by the piping. sent to 4. In the waste heat boiler 4, heat is recovered from the exhaust gas, and it is rapidly cooled to 190° C. or less in the rapid cooling tower (lowering temperature treatment) 5 to prevent resynthesis of dioxins.

The gas discharged from the quenching tower 5 passes through a pipe while containing dust, and is sent to the upstream side of the dust collector 6 . In addition to hydrogen chloride gas, there is a possibility that harmful substances such as dioxins are resynthesized in the gas. supplied.
As a treatment agent, an alkaline agent (e.g., slaked lime, baking soda) is used as a neutralizing agent to neutralize acid gas components such as hydrogen chloride gas, and an adsorption agent is used to adsorb dioxins. agents (eg activated carbon, artificial zeolites) are used. In addition, although slaked lime and activated carbon are mainly mentioned in this specification, they are not limited to these.

As the treating agent, a mixture of a neutralizing agent and an adsorbent in a predetermined ratio can be used. In this case, it is possible to use only one processing agent supply device, and the system can be simplified. Alternatively, the neutralizing agent and the adsorbent may be used without being mixed. In this case, two supply devices are required for each, but there is an advantage that the amount of each supply, the period of supply, the start of increase, etc. can be managed independently. In particular, the present invention is based on a new finding that the concentration of hydrogen chloride gas is reduced in a relatively short period of time by adding a neutralizing agent, whereas the concentration of dioxins tends to increase with a time lag even after the concentration of hydrogen chloride gas is reduced. It is very effective to be able to independently control the amount of both treatment agents to be increased at effective timings and/or periods.

In the dust collector 6, dust-containing gas entering from the upstream side is collected and filtered by a bag filter. The dust is collected in a dust collecting container 7 provided on the downstream side, and treated by an outsourcing contractor. The gas fed into the dust collector 6 contains acidic gases such as sulfur oxides, nitrogen oxides and hydrogen chloride, which are neutralized by a neutralizing agent. is adsorbed by the dust collecting container 7 and collected.

After being processed by the dust collector 6, the gas is sent to a chimney 9 through a pipe by an induced draft fan 8 and discharged outside the system. A hydrogen chloride gas measuring device 12 is installed in the middle of the chimney 9 to continuously measure the concentration of hydrogen chloride.
The installation location of the hydrogen chloride gas measurement device 12 is not limited to the chimney 9, and there is no particular problem in predicting the amount of dioxins generated even if it is installed in any location after the quenching tower (lower temperature treatment) 5. . However, from the standpoint of simplification of the system, it is preferable to use data acquired by a hydrogen chloride gas measuring device installed to measure the hydrogen chloride gas discharged outside the system. Specifically, it is preferable to install a hydrogen chloride measuring device after a dust collector capable of measuring the hydrogen chloride gas concentration after neutralization by the treating agent (not including the dust collector).

The hydrogen chloride gas measuring device 12 not only has a faster response speed of about 2 seconds at the shortest than the conventional suction type gas concentration monitor, but also can be directly attached to the measurement point without the need for a sampling device, so real-time measurement can be performed. A laser type gas analyzer capable of concentration measurement is preferred.
The hydrogen chloride gas measuring device 12 constantly measures the hydrogen chloride concentration at predetermined intervals. The hydrogen chloride gas concentration is measured, for example, as an instantaneous value every two seconds, but it is not limited to this. However, if the measurement interval is too short, the data handling load will increase, so it is preferable that the measurement interval is one second or longer. Although the instantaneous value and the measured value are basically the same, the term "instantaneous value" is mainly used to correspond to the average value.

The processing agent supply control device 20 is a device provided with a calculation means inside thereof for interlocking the hydrogen chloride gas measurement device 12 and the processing agent supply device 11 .
The processing agent supply control device 20 has a function of controlling the amount and supply period of the adsorbent supplied from the processing agent supply device 11 to the dust collector 6 in order to suppress dioxins, and a function of controlling the processing agent in order to suppress hydrogen chloride gas and the like. It has a function of controlling the amount of neutralizer supplied from the agent supply device 11 to the dust collector 6 and the period of supply. The processing agent supply device 11 may be provided individually according to each function, but when a mixture is used as the processing agent, the processing agent is mixed with either dioxins or hydrogen chloride gas and supplied. Control. Moreover, each amount of the adsorbent and the neutralizing agent may be defined in terms of any unit such as weight, mass, supply rate, or the like.
Two functions of the processing agent supply control device 20 will be described in detail below.

<Dioxin Suppression Function of Processing Agent Supply Control Device 20>
First, an outline of a method for suppressing dioxins according to an embodiment of the present invention will be described.
The present invention measures the concentration of hydrogen chloride and the concentration of dioxins in advance, and uses the increase period obtained from the correlation between the two, so that when incineration is actually performed as a business (hereinafter referred to as "actual operation") is capable of suppressing dioxin concentration only by measuring hydrogen chloride concentration. To explain 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 (average value calculation), and the smoothed change over time of the hydrogen chloride concentration is obtained. Then, the increase period obtained through correlation processing between the smoothed hydrogen chloride concentration and the dioxin concentration is set as a prescribed value for actual operation. Details of the increase period will be described later. During actual operation, the amount of adsorbent is controlled by the processing agent supply control device 20 using a specified value including the amount increase period, so that the generation of dioxins can be suppressed only from the hydrogen chloride concentration measured during actual operation. It becomes possible.

Next, the prescribed values that are stored in advance in the processing agent supply control device 20 during actual operation will be described in detail.
The processing agent supply control device 20 stores a normal amount of adsorbent, a predetermined period for averaging measured values of hydrogen chloride concentration (hereinafter sometimes referred to as "averaging period"), and a period for increasing the amount of adsorbent (hereinafter referred to as "averaging period"). It is sometimes referred to as "increase period".), the upper limit of the average hydrogen chloride concentration set in advance, and the amount of adsorbent to be increased are stored as specified values.

The normal amount of adsorbent is the amount of adsorbent that is constantly supplied to the dust collector 6 . In any waste incineration plant, a certain amount of hydrogen chloride gas and dioxins may be generated. If this amount is large, the risk of dioxins escaping 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 suitable in terms of cost. Therefore, the optimum amount is set in advance. Since the normal amount of adsorbent is a unique value that depends on each incineration system, it is set according to the system.
In a waste incineration system that does not always supply a constant amount of adsorbent, the normal amount of adsorbent may be set to unnecessary or zero.

The period for averaging the hydrogen chloride concentration measurement values is the averaging period for calculating the average value of the measured instantaneous hydrogen chloride concentration values. The inventors found that the correlation between the dioxin concentration and the instantaneous hydrogen chloride concentration is low, but the correlation with the average value is shown. This is probably because the measured hydrogen chloride concentration fluctuates sharply in a short period of time, so it is not suitable for direct comparison with the measured dioxin concentrations, which show long-term fluctuations.
The averaging period for obtaining the average value is preferably at least 30 minutes or more, more preferably 1 hour or more, because if the period is short, the effect of the hydrogen chloride concentration in a short period will be strong. Also, if it is too long, it becomes difficult to obtain a good correlation, so at least 3 days or less, preferably 2 days or less is suitable. In particular, it is preferable to match the cycle of the actual incineration work. For example, when the incineration work is performed in a 24-hour routine, the 24-hour average is optimal. For example, when a worker shifts at 8:00, a 24-hour average value from 8:00 of the previous day to 8:00 of the current day is used. Alternatively, a 24-hour average value from 0:00 to 24:00 of the previous day may be used regardless of the shift time of the worker.
It should be noted that if it is only for dioxins suppression measures, it is not necessary to set the hydrogen chloride concentration measurement interval to several seconds, and for example, it is possible to set it to about 10 minutes depending on the averaging period.

Next, the adsorbent increase period will be described.
As a result of the diligent efforts of the present inventors, it was found that there is a time lag of several days in the correlation between the two parameters (average value of dioxin concentration and hydrogen chloride concentration), and that the concentration of dioxins rises after the average value of hydrogen chloride concentration increases. was gotten. Although the reason for this is not clear, one factor is that it takes several days to resynthesize dioxin. As another factor, it cannot be denied that dioxins and the like adhering to pipes and dust collectors are peeled off after several days. In any case, if this time lag is used, it becomes possible to effectively suppress dioxins based on the hydrogen chloride concentration measured value (average value). Therefore, a period exceeding at least this lime lag is set as an amount increase period of the adsorbent, and the adsorbent is supplied from the processing agent supply device 11 to the dust collector 6 over the period. In addition, since this time lag may be a characteristic unique to each waste incineration system, it is determined in advance for each waste incineration system.
Specifically, in order to obtain information on the amount of adsorbent increasing period, together with the concentration of hydrogen chloride gas, the concentration of dioxins contained in the gas discharged from the chimney 9 or the concentration of soot and dust collected by the dust collection container 7 downstream of the dust collector 6 At least one concentration of dioxins contained in rubbish dust is measured in advance (“preliminary measurement” in FIG. 11). It is important to measure the hydrogen chloride concentration well in advance of the dioxin concentration measurement date. It is desirable to measure the hydrogen chloride concentration at least five days before, preferably one week or more before.
Next, calculate the average value of the hydrogen chloride concentration for each set averaging period, and obtain the change over time of the average value (“Calculate the average hydrogen chloride concentration value” in the same figure. Subsequently, the average value as a function of time and Calculate the correlation with the dioxin concentration measurement value ("correlation processing" in the figure) and determine the time lag between the two.Finally, add an appropriate safety margin period to the calculated time lag to increase the amount of adsorbent. period.

Next, the control flow of the dioxin suppression function by the processing 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.
When the average value of the hydrogen chloride gas concentration measured by the hydrogen chloride gas measuring device 12 rises and exceeds the preset upper limit of the average hydrogen chloride concentration, the processing agent supply control device 20 automatically supplies the processing agent. The processing agent supply device 11 is controlled so that the amount of adsorbent fed from the supply device 11 to the dust collector 6 is increased according to a preset amount of the adsorbent to be increased. As a method for increasing the amount of adsorbent, there are various methods of changing operating conditions, such as a method of increasing the amount of one-time charging, a method of increasing the frequency of charging, or a combination of these methods.
The adsorbent maintains the increased state until a preset adsorbent increase period elapses (“adsorbent increase process” in FIG. 2). After the increase period, if it is confirmed that the average value of the measured hydrogen chloride concentration is below the upper limit of the average value, the amount of adsorbent is reduced ("adsorbent amount reduction process" in FIG. 2). For example, by making the amount of decrease equal to the amount of increase, it returns to the preset normal amount of adsorbent, but it is also possible to gradually return to the normal amount by making the amount of decrease smaller than the amount of increase.

If the average value of the hydrogen chloride gas concentration for a predetermined period exceeds the upper limit value again during the period of increasing the amount of the adsorbent, the period of increasing the amount of the treating agent is further extended from that time point for a period equivalent to the period of increasing the amount of the adsorbent. , further increasing the dosage in such cases, combining these, etc. are one embodiment effective from the safety side.
The upper limit of these average values and the amount of adsorbent to be increased can be any value, for example, 120 ppm. In addition, more suitable values can be obtained by actually artificially throwing incinerators with a high chlorine concentration and trying experiments in which the upper limit of the average value and the amount of adsorbent charged are changed in multiple patterns.
The processing agent supply control device 20 may be integrated with the hydrogen chloride gas measurement device 12 or the processing agent supply device 11 .

<Hydrogen chloride concentration suppression function of processing agent supply control device 20>
The processing agent supply controller 20 stores information on the normal amount of neutralizing agent, the preset upper limit of instantaneous hydrogen chloride gas concentration, and the increased amount of neutralizing agent.
The normal amount of neutralizing agent is the amount of neutralizing agent that is constantly supplied to the dust collector 6 .
The preset instantaneous upper limit of hydrogen chloride gas concentration is the hydrogen chloride gas concentration voluntarily set for each treatment facility.
The neutralizing agent increase amount is the amount of the neutralizing agent that is increased when the measured hydrogen chloride gas concentration exceeds the hydrogen chloride gas concentration instantaneous upper limit.
Unlike dioxin suppression measures, hydrogen chloride gas reacts quickly with the neutralizer, so as soon as it is confirmed that the measured hydrogen chloride gas concentration exceeds the instantaneous hydrogen chloride gas concentration upper limit, the amount of neutralizer is increased. If so, the hydrogen chloride gas can be rapidly reduced.
Further, it is sufficiently effective to set the end of the neutralizing agent amount increase state to the time when the measured value of the hydrogen chloride gas concentration falls below the upper limit of the instantaneous value. FIG. 10 shows a PAD diagram of one aspect of the method of controlling the supply of the neutralizing agent.

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

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), which has short-term effects. On the other hand, for dioxin control measures, the start and end times of increasing the amount of adsorbent are determined based on the data (average value) from which short-period effects have been removed. In particular, the final stage is characterized by being determined based on the correlation between the average hydrogen chloride concentration and the dioxin concentration.
If the purpose is to suppress both the concentration of hydrogen chloride gas and dioxins by using a treatment agent in which a neutralizing agent and an adsorbent are mixed, both control methods shown in FIGS. should be combined appropriately.

Hereinafter, a waste incineration system according to an embodiment of the present invention, which can control the concentration of dioxins so that it does not exceed a specified value even when dioxins are resynthesized, will be further described based on examples.

First, the restriction on acceptance of high-chlorine-concentration incinerators, which causes the generation of dioxins, performed in the waste incineration system used in this embodiment will be described. In the waste incineration system used in this example, the chlorine content was measured as much as possible before acceptance for all items to be incinerated so as not to accept incinerated materials with a high chlorine content.

In this waste incineration system, the chlorine concentration was investigated twice before and after acceptance. Before acceptance, the chlorine concentration was measured by obtaining information from the waste discharger or obtaining a sample in advance. The measurement work differs depending on the liquid and solid substances. Liquid substances are measured with pH test paper, but when the pH test paper cannot be measured due to the influence of oil, etc., the oil is burned and the pH of the remaining water is measured. If the measurement paper showed a pH of 3 or less, it was determined that the chlorine concentration was too high for the waste to be processed by the waste incineration system, and was basically unacceptable. In the case of solids, we asked in advance to provide information on whether chlorine is contained based on information from the incinerator generating business. In the case of 1 wt% chlorine, it was determined as unacceptable in principle. However, cases where the received amount was small and it was judged that the impact on the overall amount of incineration processing was small was excluded.

In this example, the waste incineration system described in FIG. 1 was used. However, the amount of processing agent supplied in this example was constant, and the amount of processing agent was not increased or decreased during the experiment. In addition, the incineration of the incinerated material is carried out by maintaining the combustion gas temperature in the primary combustion furnace 2 of the incineration process at 850° C. or higher, and maintaining the inlet/outlet temperature to the secondary combustion furnace 3 at 850° C. or higher. At the same time, a residence time of 2 seconds or more was ensured.
As a result of checking the combustion gas temperature of each combustion furnace, it is thought that no dioxins are generated up to the exit of the secondary combustion furnace 3. Furthermore, as a result of analyzing the overheating residue, it was found that all were below the detection limit and were rendered harmless. 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 investigation results, it was presumed that dioxins are resynthesized in the vicinity of the temperature reduction treatment process from the waste heat boiler 4 to the quenching tower 5.

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

As a treating agent, high-reactivity slaked lime (15% activated carbon) manufactured by Chichibu Lime Industry Co., Ltd., average particle diameter 8 μm, BET 45 m 2 /g, pore volume 0.2 cm 2 /g, CaO≧72.5% was used. The treating agent has the ability to suppress hydrogen chloride and dioxins.

The amount of treatment agent supplied was 2.4 kg/h. Among them, the supplied amount of slaked lime was 2.0 kg/h and the amount 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 at about 15 ppm. Assuming that all the charged slaked lime had reacted, the amount of hydrogen chloride resulting from the charged sludge was estimated to be 177 ppm.

In this embodiment, as the high-chlorine incinerator, sludge that is considered to contain about 4 to 5% chlorine is injected twice from 8:00 to 11:00 in the morning and from 01:00 to 4:00 in the afternoon. By increasing the concentration of hydrogen chloride in the exhaust gas, it was verified whether the processing agent supply control device 20 and the processing agent supply device 11 would operate properly when the voluntarily set hydrogen chloride concentration instantaneous upper limit of 200 ppm was exceeded.

The processing agent supply device 11 controls the amount of supply by means of a gate valve and an electric rotary valve. In this embodiment, intermittent operation of 4 seconds operation and 60 seconds stop during normal operation, which has been verified in advance, is basically used. is detected, the operating conditions are switched, and the setting is changed to intermittent operation of 16 seconds operation-30 seconds stop.

FIG. 3 shows the change in hydrogen chloride concentration over time. As shown in FIG. 3, after 30 minutes from the start of charging sludge containing chlorine in the morning, when the concentration of hydrogen chloride in the exhaust gas begins to rise and exceeds 200 ppm, the processing agent supply control device 20 controls the processing agent supply device 11. The treating agent was supplied in an increased amount, and after a few seconds the concentration became 200 ppm or less. This action occurred three times. In the afternoon, unlike the morning, the hydrogen chloride concentration increased after 1 hour and 30 minutes from the start of the introduction of sludge containing chlorine, and more than 200 ppm was detected 19 times in total. The behavior of becoming 200 ppm or less within seconds was repeated. Therefore, it was confirmed that the processing agent supply control device 20 and the processing agent supply device 11 can cope with the increase in hydrogen chloride concentration.

If the instantaneous value data for every two seconds in FIG. 3 is replaced with the average value for every hour as shown in FIG. 4, the effect of the treatment agent can be easily confirmed. Therefore, it is possible to monitor and control the hydrogen chloride concentration in the exhaust gas by monitoring the hourly average value. However, since it is a value obtained by smoothing the instantaneous value, it is desirable that the upper limit is lower than the instantaneous value, for example 120 ppm.

Further, in this example, the dioxin concentration in exhaust gas and the dioxin concentration in dust were measured seven times in total. The dioxins concentration in the exhaust gas is measured by an external analysis organization according to JISK0311 "Method for measuring dioxins in the exhaust gas", and the dioxin concentration in the soot and dust is measured according to Article 2-2 of the Ordinance for Enforcement of Special Measures against Dioxins. It was carried out using the method specified by the Minister of the Environment based on the provisions of paragraph 1.

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

Using the data in Table 1, plotting the relationship between the dioxin concentration and the average hydrogen chloride concentration by plotting the horizontal axis as the date and the vertical axis as the correlation coefficient R, as shown in FIG. Although there is a correlation, it was found that five days before the measurement, the correlation coefficient R was about the same as the day before the measurement. That is, it was confirmed that there is a four-day time lag in the correlation between the concentration of dioxins in 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, and considering the safety factor, it was set to 5 days or more. Since this time lag is a value that depends on each waste incineration system, it must be obtained in advance for each system.
In addition, the correlation between the dioxin concentration and the hydrogen chloride concentration was similarly recognized for both the dioxin concentration in exhaust gas and dust. The correlation between the concentrations of dioxins in both exhaust gas 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 control dioxin concentration based on hydrogen chloride concentration, it is necessary to measure dioxin concentration in exhaust gas and dust. However, the knowledge that it can be used was obtained.

In the waste incineration system used in this experiment, during normal operation, 2.4 kg/h of processing agent (a mixture of neutralizing agent and adsorbent containing slaked lime with 15% activated carbon) was supplied to reduce the concentration of hydrogen chloride. was constantly monitored, but based on the results of the time lag information based on the previously described correlation, the 24-hour average hydrogen chloride concentration from 0:00 to 24:00 on the previous day exceeded the preset average upper limit (for example, 120 ppm) From the day when the excess was confirmed, the amount of the treating agent was increased until 5 days later when the correlation was expected to disappear in consideration of the time lag. In addition, when the hydrogen chloride concentration measured data every 2 seconds as an instantaneous value exceeds the upper limit of 200 ppm of the instantaneous value, a separate system that automatically increases the amount of processing agent can be used to cope with the increase in hydrogen chloride concentration. I was able to

Fig. 9 shows an image of the time lag of the dioxin concentration that is expected to increase after the average hydrogen chloride concentration in the exhaust gas exceeds the upper limit of the average value. At time A when the instantaneous hydrogen chloride concentration exceeds the upper limit and the average hydrogen chloride concentration has not yet exceeded the upper limit of the average value, the amount of neutralizing agent that neutralizes acidic gas components such as slaked lime immediately increases. be done. At time B when the average hydrogen chloride concentration exceeds the upper limit of the average value, the amount of adsorbent for adsorbing dioxins and the like is increased. Then, the supply is continued until the time point C (after 5 days in this embodiment) when the correlation between the dioxin concentration and the average hydrogen chloride concentration disappears.

In Japan, in line with dioxin emission regulations, existing furnaces that do not meet the standards are equipped with incineration equipment equipped with advanced treatment technology and exhaust gas treatment equipment, and the emission standard values are achieved. It is a heavy burden for waste disposal operators who have a waste incineration system. According to this waste incineration system, the installation and maintenance costs can be kept low, and the amount of treatment agent discharged can be reduced. It can also be used as part of a production system.

DESCRIPTION OF SYMBOLS 1... Receiving hopper, 2... Primary combustion furnace, 3... Secondary combustion furnace, 4... Waste heat boiler, 5... Quenching tower (lowering temperature treatment), 6... Dust collector , 7... Soot and dust collection container 8... Induced draft fan, 9... Chimney, 10... Entire waste incineration system, 11... Treatment agent supply device, 12... Hydrogen chloride gas measuring device, 20 ... processing agent supply control device

Claims (4)

a dust collecting means; and a processing agent supply means provided upstream of the dust collecting means for supplying a processing agent;
Hydrogen chloride concentration measuring means for continuously measuring the hydrogen chloride concentration in the exhaust gas;
a processing agent supply control means for controlling supply of the processing agent;
In a waste incineration system comprising
The treatment agent contains an adsorbent having a function of adsorbing dioxins in the exhaust gas ,
When the average value of the hydrogen chloride concentration exceeds the upper limit of the average value of the hydrogen chloride concentration, the processing agent supply control means exhibits a correlation between the change in the average value over time and the change in the dioxin concentration over time determined in advance. A waste incineration system characterized by increasing the amount of the processing agent for a period exceeding the time lag period . 2. The waste incinerator according to claim 1, wherein the period for increasing the amount of the treating agent is longer than the period during which the average value of the hydrogen chloride concentration exceeds a preset upper limit of the average value of the hydrogen chloride concentration. system. 3. The waste incineration system according to claim 1 , wherein said correlation is a correlation between said average value and at least one dioxin concentration in exhaust gas or dust. 3. The waste incineration system according to claim 1 , wherein the average value is an average value of hydrogen chloride concentration measurement data for 30 minutes to 3 days .

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