JP2005118733A - Preventive method of eluting heavy metals in ash and heavy metals elution preventive system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heavy metals-elution preventive method and a heay metals-elution preventive system in ashes where the proper required amount of a chemical can be determined also to the ashes, which have a wide dispersion of the amounts of the heavy metals by performing a quick and accurate measurement thereof. <P>SOLUTION: The heavy metals-elution preventive method in the ashes that on a transfer line where the ashes 3 are transferred to the heavy metals-elution preventive device 5, the heavy metals contained in the ashes 3 are directly measured by a fluorescent X-rays analyzer 4, the measurement results are sent to a controller 8, and the controller 8 instructs the required amount of the chemical for preventing the elution of the heavy metals to the device 5 based on the sent measurement results, and the instructed chemical is injected, is provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for preventing elution of heavy metals in ash and a system for preventing elution of heavy metals.

  Dust (such as ash) such as various fuels, waste, sludge and other incineration ash, incineration fly ash, and molten fly ash are harmful heavy metals (lead, cadmium, copper, chromium, mercury, selenium). Etc.), it is landfilled at the final disposal site. However, if it is landfilled as it is, it may elute in contact with rainwater or groundwater and contaminate nearby soil and groundwater. They lead to pollution of rivers and oceans and become global pollution. Therefore, ash is landfilled after heavy metals are prevented from leaching.

  As a method for preventing the elution of heavy metals, a method of kneading a chelating agent having a dithiocarbamic acid group, an L-glutamic acid group, or the like is commonly used and widely used. In this method, a batch test is performed in advance on the above six kinds of heavy metals to obtain an addition amount that can be reduced below the elution reference value, and by adding a safety factor to this amount, the addition amount of the chelating agent is determined and determined. After adding the added amount of chelating agent, the mainstream is to regularly monitor the dissolution by conducting a dissolution test stipulated by law.

  However, in the above method of kneading the chelating agent, it usually takes about 2 to 7 days until the result of the dissolution test is revealed. Moreover, the heavy metals contained in the dust vary greatly depending on the type and properties of the generation source, and the elution of heavy metals cannot be reliably prevented from the dust containing suddenly high heavy metals. Of course, it is conceivable to increase the safety factor in preparation for such a situation, but in this case, there is a problem that the processing cost is high because the chelating agent is not inexpensive.

Therefore, in order to reduce the amount of chelating agent used, a method has been developed in which a chelating agent is added to a solution obtained by dissolving and extracting heavy metals in ash, and the appropriate amount of chelating agent is determined by measuring the absorbance of the solution. (Patent Document 1). Furthermore, after removing the incineration fly ash from the incinerator, mixing it with an alkaline solution and heating it, measure the lead concentration in this aqueous solution, and correlate the pre-calculated lead concentration with the required amount of heavy metals elution inhibitor From the relationship, a technique for determining the necessary amount of chelating agent has been developed (Patent Document 2).
Japanese Patent Application Laid-Open No. 10-337550. Japanese Patent Application Laid-Open No. 2002-207032.

  However, since all of the above conventional techniques require a pretreatment such as dissolution in water, etc., it takes a lot of time to obtain measurement results, so ash containing heavy metals that vary widely and change from moment to moment. In response to the change in composition, it has not yet been possible to quickly and accurately determine the required amount of drug to be added and to immediately indicate the required amount of drug to be added.

  The problem to be solved by the present invention is to solve the above-mentioned problems of the prior art by performing a quick and accurate measurement, so that an appropriate amount of drug can be obtained even for ash with a large amount of heavy metals. It is the point which provides the heavy metal elution prevention method and heavy metal elution prevention system in ash which can determine these.

  The above object can be achieved by the invention described in the claims. That is, the characteristic configuration of the method for preventing elution of heavy metals in ash according to the present invention is that the heavy metals contained in the ash are analyzed by fluorescent X-ray analysis on the conveying line for conveying the ash to the heavy metals elution preventing device. Measure directly with the device and send the measurement result to the control device. Based on the transmitted measurement result, the control device instructs the elution prevention device for heavy metals to the heavy metal elution prevention device. Then, the instructed medicine is to be introduced.

  According to this configuration, the ash is directly measured by the fluorescent X-ray analyzer in the middle of the conveyance line, so that it is not necessary to pre-process the ash that is the object of measurement as in the prior art, and usually several seconds to several tens Rapid measurement of about 2 seconds is possible, and accurate measurement is possible by using a fluorescent X-ray analyzer with high measurement sensitivity. Corresponding to the change in the composition, it is possible to promptly and accurately indicate the appropriate amount of the drug on line, and the amount of the drug used can be made appropriate to reduce the processing cost. In addition, the present invention does not require pretreatment by dissolving in water to measure heavy metals in ash, so there is also an advantage that there is no need for waste liquid treatment equipment or waste liquid treatment man-hours after pretreatment. Have.

  As a result, it is possible to provide a method for preventing elution of heavy metals in ash, which can determine the appropriate amount of chemicals, even for ash with large variations in the amount of heavy metals, by performing quick and accurate measurement. did it.

  It is preferable that the measurement of the heavy metal contained in the ash on the transport line by the fluorescent X-ray analyzer is performed while the relative speed of the fluorescent X-ray analyzer and the ash is stopped for a predetermined time.

  According to this configuration, the content of heavy metals in ash at a predetermined location can be measured more accurately and stably.

  The surface of the ash is smoothed by using a smoothing means that contacts the surface of the ash for the measurement on the transport line of heavy metals contained in the ash by the fluorescent X-ray analyzer. It is preferable to carry out.

  According to this configuration, the distance between the X-ray irradiation port and the ash to be measured can be maintained substantially constant, the measurement accuracy can be improved, and a more stable measurement result can be obtained.

  In addition, the characteristic configuration of the heavy metal elution prevention system according to the present invention includes a transport device that transports ash to the heavy metal elution prevention device, and measures heavy metals contained in the ash on the transport line of the transport device. X-ray fluorescence analyzer capable of transmitting a measurement result measured by the X-ray fluorescence analyzer, and a controller for instructing a necessary amount of a drug for preventing elution of the heavy metals based on the transmission result And a heavy metal elution preventing device for receiving the medicine in response to the instruction from the control device.

  This configuration provides a system for preventing heavy metals from eluting in ash, which can determine the appropriate amount of chemicals, even for ash with large variations in the amount of heavy metals, by making quick and accurate measurements. can do.

  When the X-ray fluorescence analyzer measures heavy metals contained in the ash on the transport line, it preferably has a mechanism for stopping the relative speed between the X-ray fluorescence analyzer and the ash for a predetermined time.

  According to this configuration, a more accurate and stable measurement result can be obtained with respect to the heavy metal content in the ash at a predetermined location.

  When the fluorescent X-ray analyzer measures heavy metals contained in the ash on the transport line, the smoothing means for smoothing the surface of the ash so that the smooth surface of the ash can be measured It is preferable to have.

  According to this configuration, the distance between the smoothed ash surface and the X-ray irradiation port can be maintained substantially constant, the measurement accuracy can be improved, and a more stable measurement decision can be obtained.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a flowchart showing processing steps in the heavy metal elution prevention system according to this embodiment. General waste, industrial waste, etc. are incinerated by the incinerator or melting furnace 1, and ash generated by the processing is collected by the bag filter 2. The generated ash (soot) 3 contains various heavy metals, and it is necessary to perform a heavy metal elution prevention process before being sent to the final landfill site. Therefore, heavy metals elution prevention agent 6 such as a chelating agent and an appropriate amount of water 7 are added to ash 3 to prevent elution of heavy metals by a conveyor device such as a belt conveyor 9 so that heavy metal elution prevention treatment is performed. Although it is transferred to the apparatus 5, the lead content of the heavy metals in the ash 3 is directly measured by the fluorescent X-ray analyzer 4 on the conveyance line in the middle. This is because priority is given to measuring the lead content based on the fact that, among heavy metals contained in the ash 3, elution and detection of the emission standard value or more are mostly lead. Of course, depending on the type of incinerated materials, other heavy metals may rarely exceed the emission standard value, so in consideration of such cases, it is possible to measure at least cadmium, copper, chromium, mercury, and selenium simultaneously. preferable.

  The measurement by the fluorescent X-ray analyzer 4 is characterized in that the measurement can be performed more quickly than the conventional method, the measurement sensitivity is high, and an accurate and rapid measurement result can be obtained. Moreover, when measuring heavy metals other than lead at the same time, the speed and accuracy are almost the same. Usually, it can be measured in several seconds to several tens of seconds.

  In order to put an appropriate amount of chelating agent in the heavy metal elution preventing device 5 based on the measurement result by the fluorescent X-ray analyzer 4, the measured value (count number) by the fluorescent X-ray analyzer 4 and each in ash A measurement curve is prepared by measuring the relationship with the content of heavy metals in advance, and the correlation between the heavy metals and the chelating agent is determined in advance, and the data is input to the control device 8 for control. An appropriate amount of chelating agent is instructed from the device 8 to the heavy metal elution preventing device 5. That is, by measuring the heavy metal content in the ash, the amount of chelating agent used in the heavy metal elution preventing device 5 and the amount of water to be added are controlled. The control device 8 to which the measurement result obtained by the fluorescent X-ray analysis device 4 is transmitted instructs the heavy metal elution prevention device 5 so that an appropriate amount of the chelating agent and water corresponding to the measurement result is input in a timely manner. To do.

  Thus, the present heavy metal elution prevention system can prevent the addition of an excessive amount of chelating agent and an inappropriate amount of water, and can always carry out an appropriate heavy metal elution prevention treatment, and wasteful of expensive chelating agents. The use can be avoided, and the processing cost can be surely reduced.

  And the ash processed by the heavy metal elution prevention apparatus 5 is conveyed to a final disposal site, and is disposed by landfill.

  Next, a method for measuring heavy metals from the ash 3 by the fluorescent X-ray analyzer 4 will be described in more detail with reference to FIGS.

  As shown in FIG. 2, the ash 3 discharged from the bag filter 2 is placed on the belt conveyor 9 and conveyed toward the heavy metal elution prevention device 5. An X-ray fluorescence analyzer 4 is disposed in the middle of the transport line, and an X-ray irradiation port 4a surrounded by an X-ray protective cover 4b is disposed opposite to and close to the ash 3. When irradiating X-rays from the X-ray irradiation port 4a, the ash 3 on the belt conveyor 9 and the X-ray irradiation port 4a of the fluorescent X-ray analyzer 4 are usually connected to detect a predetermined concentration of heavy metals. It is preferable to stop the relative speed for about ten seconds. Meanwhile, the transfer line may be stopped, or the X-ray irradiation port 4a of the fluorescent X-ray analyzer 4 may be moved in synchronization with the traveling speed of the transfer line.

  When measuring by irradiating X-rays from the X-ray irradiation port 4a, measurement is preferably performed with the surface of the ash 3 being smoothed in order to increase measurement accuracy and obtain a stable measurement result. In order to smooth the surface of the ash 3 facing the X-ray irradiation port 4a, a ship-shaped smoothing jig 10 as shown in FIGS. 3A and 3B can be used. That is, a smoothing jig 10 which is a kind of smoothing means is placed on the ash 3 transferred on the belt conveyor 9 to smooth the surface of the ash 3 being conveyed, and X-ray After making the irradiation distance substantially constant, X-ray irradiation is performed for measurement. If the smoothing jig 10 is placed on the ash 3, even if the height of the ash 3 on the belt conveyor 9 changes, the smoothing jig 10 will change. It is preferable that the ash 3 is always moved up and down so as to be smooth.

  The place where X-ray irradiation is performed is a measurement location 10b formed between the two legs 10a of the smoothing jig 10, and the X-ray irradiation port 4a is lowered to the measurement location 10b so that the surface of the ash 3 is exposed. Close. Since the measurement location 10b is flattened by the action of the bottom 10c of the smoothing jig 10 formed flat, highly accurate measurement can be stably performed. It is preferable that the measurement is performed not only at one point but also at several points by moving the measurement place. The movement of the measurement place is performed so as not to stop the relative speed between the smoothing jig 10 and the traveling speed of the transport line. The measurement place may be moved, the smoothing jig 10 may be moved on the belt conveyor 9 in the lateral direction, or the movements of both may be combined. Of course, the movement of the smoothing jig 10 may be performed mechanically or automatically using a traction jig or the like, or may be performed manually.

  The smoothing jig 10 may be made of various materials such as metal, ceramic, and resin, and is not particularly limited. However, the smoothing jig 10 is not easily damaged by contact with the ash 3. What is necessary is that it has a certain weight and can smooth the surface of the ash 3 traveling on the transport line. It is preferable that the bottom of the smoothing jig 10 has a high smoothness so that the attached ash can be easily removed. The shape of the smoothing jig 10 can also level the surface of the ash 3 so that the X-ray irradiation port 4a of the fluorescent X-ray analyzer 4 is close to the flat surface of the ash 3. The shape shown in FIG. 3 is not limited as long as X-rays can be irradiated.

  In the present embodiment, since measurement is performed using such a smoothing jig 10, heavy metals in ash can be quickly obtained on-time without requiring special pretreatment for the ash 3. Will be able to measure.

  When the X-ray irradiation port 4a of the X-ray fluorescence analyzer is arranged and measured as shown in FIG. 3 (b), the X-ray irradiation port 4a is close to and arranged so as to contact the ash 3 conveyed on the conveyor. The irradiation condition of the line can be accurately measured with a weaker tube voltage / tube current than a conventional method such as a tube voltage of 40 kV or less and a tube current of 1 mA or less. Therefore, there is very little leakage X-rays even near the X-ray irradiation port 4a, and usually a protective cover is not required around the X-ray irradiation port 4a, but a protective cover made of a transparent acrylic resin or the like that can visually recognize the internal situation. 4b may be provided.

  Depending on the incineration plant, the amount of water contained in ash, the presence of heavy metals (for example, lead oxide or lead chloride in the case of lead), the presence or amount of other heavy metals, lead, etc. The content rate and the required amount of the chelating agent may change, and a correlation between them may be obtained in advance, and the amount of the chelating agent input may be corrected from time to time based on these relationships.

  When the ash 3 contains a large amount of moisture, the measured value with the fluorescent X-ray analyzer 4 tends to be somewhat low, which may affect the measurement result. Therefore, the variation of the measurement result due to the influence of the amount of moisture contained in advance is obtained, and the data is input to the control device 8 and the moisture in the ash transported on the transport line is separately measured. The measurement result may be corrected based on the result. In particular, if the ash 3 has a large amount of deliquescent components such as calcium chloride, it becomes easier to absorb moisture, and correction is desirable when the time until treatment is long.

  FIG. 4 shows the results of measuring a sample having a lead concentration of 0.1 to 10% by weight in the molten fly ash using a portable fluorescent X-ray analyzer with a measurement time of about 10 seconds. As a portable fluorescent X-ray analyzer, OURSTEX 110 (trade name) manufactured by Hours Tech Inc. was used, and measurement was performed under measurement conditions of a tube voltage of 35 kV and a tube current of 0.1 mA.

FIG. 4 shows that the lead concentration in ash can be accurately measured according to the conditions used in this example.
[Another embodiment]
(1) In the above embodiment, an example in which molten fly ash having a relatively high lead content was used as the lead-containing material was shown, but the lead-containing material is not limited to this, and other various wastes Incineration ash may be used.

The flowchart showing the process process in the heavy metal elution prevention system which concerns on this invention Conceptual diagram for explaining a method of measuring heavy metals in ash using a fluorescent X-ray analyzer The figure explaining the use condition of a smoothing means (a) Bottom view (b) Front view The figure which shows the relation between the lead concentration in ash and the measurement result with the fluorescent X ray analyzer

Explanation of symbols

3 Ash 4 Fluorescence X-ray analyzer 5 Heavy metal elution prevention device 8 Control device 9 Transport device 10 Smoothing means

Claims (6)

The heavy metal contained in the ash is directly measured by the fluorescent X-ray analyzer on the transport line that transports the ash to the heavy metal elution prevention device, the measurement result is transmitted to the control device, and the transmitted measurement is performed. Based on the result, the control device instructs the heavy metal elution prevention device to indicate the necessary amount of the chemical for preventing the elution of heavy metals, and then injects the designated chemical into the heavy metals elution prevention method . The heavy metals according to claim 1, wherein the measurement of the heavy metals contained in the ash on the transport line by the fluorescent X-ray analyzer is performed by stopping the relative speed between the fluorescent X-ray analyzer and the ash for a predetermined time. Elution prevention method. The surface of the ash is smoothed by using a smoothing means that contacts the surface of the ash for the measurement on the transport line of heavy metals contained in the ash by the fluorescent X-ray analyzer. The method for preventing elution of heavy metals according to claim 1 or 2. A transport device for transporting ash to a heavy metal elution prevention device, a fluorescent X-ray analyzer capable of measuring heavy metals contained in the ash on a transport line of the transport device, and a fluorescent X-ray analyzer The measurement result measured is transmitted, and a control device for instructing a necessary amount of the medicine for preventing the elution of the heavy metals based on the transmission result, and receiving the instruction from the control device, the medicine is input. A heavy metal elution prevention system comprising a heavy metal elution prevention device. The heavy metal according to claim 4, further comprising a mechanism for stopping a relative speed between the fluorescent X-ray analyzer and the ash for a predetermined time when the fluorescent X-ray analyzer measures heavy metals contained in the ash on a transport line. Elution prevention system. When the fluorescent X-ray analyzer measures heavy metals contained in the ash on the transport line, the smoothing means for smoothing the surface of the ash so that the smooth surface of the ash can be measured The heavy metal elution prevention system of Claim 4 or 5 which has these.

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