JP2018069131A - Chemical cleaning method and particle collecting apparatus - Google Patents

Abstract

[PROBLEMS] To collect fine particles of sludge represented by powder scale, which hinders the re-operation of a boiler, by a method with a small load and a small amount of waste, so that the boiler after cleaning can be kept clean. A cleaning method and a particle collecting device are provided.
A cleaning agent is injected into an object to be cleaned 1 and a metal oxide fixed to the object to be cleaned is dissolved or peeled off, and the cleaning includes the peeled metal oxide particles, the dissolved metal ions and the cleaning agent. The entire amount of the circulating fluid is passed through a particle collecting device 3 including a cleaning circulating fluid flow path in which a single metal filament or a collection of metal filaments is installed and a superconducting magnet that magnetizes the metal filament. Then, after the particles are magnetically adsorbed on the magnetized metal filaments and removed, the chemical cleaning method is recycled to the object to be cleaned.
[Selection] Figure 1

Description

  The present invention relates to a chemical cleaning method for circulating a cleaning chemical to an object to be cleaned and a particle collecting device used in the chemical cleaning method, and in particular, a solid content generated by operation of a thermal power plant or a chemical plant is dissolved by the cleaning chemical. Alternatively, the present invention relates to a chemical cleaning method and a particle collecting apparatus that exfoliate and collect and remove the separated particles.

  In particular, a chemical cleaning method in which a cleaning chemical is circulated is generally employed as a method for removing scale from various chemical plants such as a once-through boiler for power generation where scales adhere to the inner wall and cannot be operated continuously. In the chemical cleaning method, a cleaning chemical is brought into contact with a boiler, which is an object to be cleaned, to dissolve or remove constituents of the scale. The peeled scale (also referred to as “sludge”) circulates with the cleaning agent. The particle size of the solid contained in the sludge depends greatly on the constituent components of the scale, and thus greatly depends on the water treatment of the boiler.

  Water treatment of once-through boilers is carried out to prevent failures such as corrosion, scale formation and adhesion, and carryover to the turbine in the boiler / turbine system. Volatile material treatment (AVT) and oxygen treatment ( Neutral water treatment: NWT and composite water treatment: CWT).

  Volatile substance treatment (AVT) is a method that adjusts the water quality with ammonia as a pH adjuster and hydrazine as an oxygen remover to keep the dissolved oxygen concentration low and prevent corrosion. A scale mainly composed of magnetite is generated. The The scale mainly composed of magnetite grows in a wavy shape on the inner wall surface of the boiler, and the pressure difference of the boiler is likely to increase. Therefore, the interval between chemical cleanings is as short as 3 to 5 years. The average particle diameter of the particles contained in the sludge generated when chemically cleaning the scale mainly composed of magnetite is about 20 μm to 40 μm. If this sludge remains in the boiler, the water quality at the cleanup at the time of startup deteriorates and the amount of water used for purification increases, leading to an increase in cost.

  Oxygen treatment is a method for suppressing subsequent corrosion of steel and elution of corrosion products into water by adhering poorly soluble oxides on the surface of steel and keeping them appropriately in high-concentration water. It is. Neutral water treatment is a method in which dissolved oxygen is allowed to coexist in neutral water, and composite water treatment is a method in which dissolved oxygen is allowed to coexist with ammonia under a weakly alkaline condition of pH 8.0 to 9.3. Oxygen treatment can suppress boiler differential pressure and scale growth, which are problems of volatile substance treatment. The scale generated by the oxygen treatment has a two-layer structure of an outer layer mainly composed of hematite called powder scale and an inner layer mainly composed of magnetite close to the scale of volatile treatment. Since the growth of the scale is slow and it does not grow in a wavy manner, it is said that the interval of chemical cleaning can be extended to about 10 years. However, this powder scale is refined by chemical cleaning and constitutes a hardly soluble sludge as fine particles having a particle diameter of about 1 μm to 20 μm.

  This powder scale and its sludge remain in the cleaning liquid because they have a low solubility in a general chemical cleaning liquid composition (citric acid + glycolic acid + reducing agent) and temperature (80 ° C. to 90 ° C.). This remains in the boiler after cleaning, adheres to the inner surface of the furnace wall tube after startup, and causes a rise in the furnace wall tube metal temperature and steam side erosion. (Non-Patent Document 1)

  Because of the above concerns, there is a high need for removing sludge as much as possible during chemical cleaning, and various techniques have been proposed.

  For example, as a chemical cleaning method for a volatile substance treatment (AVT) boiler, when a cleaning acid solution is circulated through a portion to be cleaned, a method of removing it using a sludge trapping means having a magnet in the middle of the circulation path (patent) Reference 1) and a method for removing undissolved substances by providing a centrifuge in a pipe system through which a chemical solution circulates have been proposed (Patent Document 2).

  According to the method of Patent Document 1, ferromagnetic sludge such as magnetite can be removed, but paramagnetic sludge such as hematite cannot be removed. In the method of Patent Document 2, since the sludge is separated using a centrifuge, its classification ability is small, the limit is about 30 μm, and fine hematite sludge (1 μm to 20 μm) can hardly be removed.

Further, a chemical cleaning method using a filter for collecting sludge has been proposed (Patent Document 3). Patent Document 3 discloses the use of a pleated membrane filter or a hollow fiber filter having a filtration capacity of 2.5 μm or less in order to collect sludge having a particle size of around 10 μm. According to the example of Patent Document 3, the circulation flow rate of the cleaning liquid is 400 m ³ / h and the filtration area is 150 m ^2. For example, when a standard 3S pleated filter (75 cm) is used, 107 pipes are required. Since the filter after destruction is discarded, a large amount of waste is generated, which is not practical.

  Furthermore, as a chemical cleaning method for an oxygen treatment boiler, a method is proposed in which the removal of coarse solids by a centrifugal separator and the removal of fine solids by a filter or membrane filtration are combined (Patent Document 4).

In Patent Document 4, the amount of solids generated by chemical cleaning of an oxygen treatment boiler is at least twice the amount of solids generated by chemical cleaning of a volatile treatment boiler, and the number of coarse solids having a particle size exceeding 20 μm is 21. % And 29%, and the solids concentration in the cleaning solution is 600 mg / l and 1200 mg / l. For example, when the solid matter concentration in the cleaning liquid is 600 mg / L, if 21% is removed as coarse particles by the centrifuge, the fine particles to be collected by the filter or membrane filtration are 474 mg / L. When the total amount of the cleaning liquid is 400 m ³ , the total amount of fine particles of 189.6 kg is collected. Although a specific example of the filter is not described in Patent Document 4, for example, when a standard 3S pleated filter (75 cm) is used, the collection ability is about 400 g / m ^{2 at the} maximum from the filtration specific resistance and pore diameter of hematite Since a filtration area of 300 m ² is required, the required number of 3S pleated filters is 200, and a large amount of waste is generated, which is not practical.

  In Patent Document 4, only a part (50 to 75%) of the liquid after centrifugation is collected by a filter or membrane filtration, and the residual liquid is supplied to the boiler. The fine particles in the residual liquid are 474 mg / L. In this case, a maximum of 118.5 mg / L to 237 mg / L of fine particles are returned again into the boiler by circulation of the cleaning liquid. Fine particles with a particle size of 20 μm or less are hardly soluble in the cleaning liquid, and therefore highly likely to stay in the low flow rate portion of the boiler. According to Non-Patent Document 1, the cause of the furnace wall tube metal temperature rise as a powder scale It becomes.

Japanese Patent Publication No. 51-40532 JP 59-157696 A JP-A-9-118993 Japanese Patent No. 5569217

“Thermal treatment of thermal power plants: introduction of oxygen treatment results and powder scale adhesion measures” Mitsubishi Heavy Industries Technical Review Vol.49 No.1 (2012)

  The present invention solves the above-mentioned problems of the prior art, collects sludge fine particles typified by powder scale, which hinders boiler re-operation, by a method with a small load and a small amount of waste. It is an object of the present invention to provide a chemical cleaning method and a particle collecting device that can keep a boiler clean.

According to the present invention, the following chemical cleaning method and particle collecting apparatus are provided.
[1] A chemical cleaning method for circulating a cleaning chemical to an object to be cleaned,
Inject the cleaning chemical into the object to be cleaned, dissolve or peel off the metal oxide fixed to the object to be cleaned,
A cleaning circulation liquid flow path in which a single metal filament or an assembly of a plurality of metal filaments is installed and the metal in which the total amount of the cleaning circulation liquid containing the separated metal oxide particles, dissolved metal ions, and the cleaning agent is installed The liquid is passed through a particle collecting device including a superconducting magnet that magnetizes the filament, and the particles are magnetically adsorbed and removed by the magnetized metal filament, and then recycled to the object to be cleaned.
The chemical cleaning method characterized by the above-mentioned.
[2] Before passing the entire amount of the cleaning circulating liquid through the particle collecting device, the entire amount of the cleaning circulating liquid is centrifuged to remove the metal oxide coarse particles, and the metal oxide fine particles, The chemical cleaning method according to [1], wherein the entire amount of the circulating cleaning liquid containing metal ions and the cleaning chemical is passed through the fine particle collecting apparatus.
[3] The particles collected by the particle collecting apparatus are magnetic particles selected from ferromagnetism, paramagnetism, or a combination thereof, according to [1] or [2] Chemical cleaning method.
[4] The chemical cleaning method according to [3], wherein the ferromagnetic fine particles include magnetite.
[5] The chemical cleaning method according to [3], wherein the paramagnetic fine particles include hematite.
[6] The chemical cleaning method according to any one of [1] to [5], wherein the object to be cleaned is a boiler applying oxygen treatment to water supply treatment.
[7] Any one of [2] to [6], wherein the coarse particles are particles having a particle size larger than 20 μm and not larger than 40 μm, and the fine particles are particles having a particle size not larger than 20 μm. The chemical cleaning method described in 1.
[8] A particle collecting device used in a chemical cleaning method for circulating a cleaning chemical to an object to be cleaned,
A particle collecting apparatus comprising: a cleaning circulating fluid channel loaded with a single metal filament or an assembly of a plurality of metal filaments; and a superconducting magnet that magnetizes the metal filament.

According to the chemical cleaning method of the present invention, it is the main component of the scale in the boiler that performs volatile substance treatment (AVT), is contained in a part of the powder scale in the boiler that performs oxygen treatment, and is the main component of the inner layer scale. Not only a certain magnetite (Fe ₃ O ₄ ), but also a paramagnetic hematite (Fe ₂ O ₃ ), which is a main component of powder scale in an oxygen-treated boiler and an outer layer scale, can be efficiently used. It can be separated and removed, and the magnetite and hematite can be prevented from being recycled to the boiler.

  The conventional chemical cleaning method using an electromagnetic filter (electromagnet) or a normal magnet cannot apply a magnetic force enough to adsorb and remove the paramagnetic material, and it is difficult to recover the powder scale. In the present invention, there is provided a particle collecting apparatus comprising a cleaning circulating fluid channel loaded with a single metal filament or an assembly of a plurality of metal filaments and a superconducting magnet that magnetizes the metal filament. It is possible to increase the magnetic force of the metal filaments to such an extent that the paramagnetic material can be adsorbed.

  Unlike the filter, the metal wire is not clogged, so that the operation period can be extended and the amount of waste can be greatly reduced. In the conventional particle collection method using a hollow fiber filter or membrane filtration, for example, the fine particle sludge of an oxygen treatment boiler chemical cleaning requires a pore size of at least 1 to 5 μm, and the initial pressure loss is high due to the pores. Since the filtration area per volume cannot be made large, the scale of the apparatus becomes considerably large, or the filter needs to be replaced during cleaning. Since the particle collecting apparatus of the present invention is magnetically adsorbed, it can collect particles regardless of the particle diameter, and the initial pressure loss is small.

  In addition, the ferromagnetic material magnetically attracted to the metal filament is also magnetized, and the magnetic force of the metal filament is further strengthened. It is possible to prevent the magnetic fine particles from being peeled off by passing the cleaning circulating liquid.

  In membrane filtration using a conventional pleated filter or the like, when sludge is collected up to the maximum collection amount of the filter, when the liquid flow is stopped, the sludge is detached and stays at the bottom of the apparatus, making it difficult to collect. For this reason, it is necessary to replace the filter after draining the liquid containing sludge out of the system by backwashing the filter, or draining the liquid from the bottom after stopping liquid feeding and emptying the liquid in the filter can body, Waste liquid increased and operation took time. In the particle collecting apparatus of the present invention, it is only necessary to replace the metal filaments on which the sludge is magnetically adsorbed, so that the replacement operation is extremely simple and backwashing can be eliminated.

It is a flowchart of one embodiment which enforces the chemical cleaning method of this invention. It is explanatory drawing of another embodiment which enforces the chemical cleaning method of this invention. It is a perspective view which shows an example of the particle | grain collection apparatus used with the chemical cleaning method of this invention. FIG. 4 is a cross-sectional view of FIG. 3. It is a graph which shows the mass magnetization measurement result of CWT sludge and hematite.

1: Oxygen treatment once-through boiler 2: Line 3: Particle collection device 4: Centrifugal line 5: Centrifuge 6: Fine particle line 7: Coarse particle line 8: Coarse particle separation tank 9: Return line 10: Pump 11: Circulation Line 31: Washing circulating fluid channel 32: Metal wire 33: Superconducting magnet 35: Vacuum vessel 36: Refrigerator 37: Conductor

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited thereto.

  FIG. 1 is a flowchart showing an example in which the chemical cleaning method of the present invention is applied to an oxygen treatment once-through boiler. The once-through boiler 1 is supplied with a cleaning circulation liquid containing a chemical cleaning chemical from a circulation line 11. The scale formed on the inner wall of the once-through boiler 1 is dissolved or peeled off by the cleaning circulating liquid flowing into the once-through boiler 1 to form sludge. Sludge containing metal ions and metal oxide particles derived from the scale is accompanied by the cleaning circulating liquid, and the entire amount is sent from the once-through boiler 1 to the particle collecting device 3 via the line 2. Sludge containing metal ions and oxide metal particles is magnetically adsorbed and removed by the magnetized metal filaments 32 loaded in the cleaning circulating liquid flow path 31 in the particle collecting device 3. The cleaning circulating liquid after the sludge removal that has passed through the particle collecting device 3 flows into the once-through boiler 1 again through the circulation line 11.

  FIG. 2 is a flowchart of an example in which the centrifugal separator 5 is provided in the front stage of the particle collecting device 3 in the embodiment of FIG. 1 of the chemical cleaning method of the present invention. The once-through boiler 1 is supplied with a cleaning circulation liquid containing a chemical cleaning chemical from a circulation line 11. The scale formed on the inner wall of the once-through boiler 1 is dissolved or peeled off by the cleaning circulating liquid flowing into the once-through boiler 1 to form sludge. Sludge containing metal ions and metal oxide particles derived from the scale is accompanied by the washing circulating liquid, and the whole amount is sent to the centrifuge 5 through the centrifuge line 4. In the centrifugal separator 5, the coarse particles are classified into coarse particles having a particle diameter exceeding 20 μm and fine particles having a particle diameter of 20 μm or less. The coarse particles are concentrated at the bottom of the centrifugal separator 5, and the coarse particle separation tank is provided via the coarse particle line 7. 8 and settled and collected. The supernatant liquid of the coarse particle separation tank 8 flows again into the once-through boiler 1 through the return line 9 and through the circulation line 11 by the circulation pump 10. The entire amount of the washing circulating liquid containing fine particles from which coarse particles have been removed by centrifugation is sent from the upper part of the centrifugal separator 5 to the particle collecting device 3 through the fine particle line 6. Sludge containing metal ions and oxide metal particles is magnetically adsorbed and removed by the magnetized metal filaments 32 loaded in the cleaning circulating liquid flow path 31 in the particle collecting device 3. The cleaning circulating liquid after the sludge removal that has passed through the particle collecting device 3 flows into the once-through boiler 1 again through the circulation line 11. When the centrifugal separator 5 and the coarse particle separation tank 8 are installed, the amount of collection in the metal wire is less than that in the case where the entire amount of sludge is collected only by the metal wire in the particle collecting device 3, and the metal wire It is possible to reduce the frequency of replacement of the articles.

The particle collection device 3 will be described with reference to FIGS. 3 and 4. In the illustrated embodiment, the particle collecting device 3 is provided with a cleaning circulating fluid passage 31 that penetrates the center of a cylindrical vacuum vessel 35. A metal filament 32 is loaded inside the cleaning circulating fluid channel 31. A superconducting magnet (solenoid coil) 33 is provided in the vacuum container 35 around the cleaning circulating fluid channel 31. The superconducting magnet 33 is cooled by being supplied with cold heat in the vicinity of 4K from a refrigerator 36 installed outside the vacuum vessel 35. The superconducting magnet 33 is connected to a conducting wire 37 for applying a charge from an external power source. The vacuum vessel 35 is provided with a magnetic shield that shields the magnetic force from the superconducting magnet 33. The particle collection device 3 uses a non-refrigerant superconducting magnet using, for example, an Nb ₃ Sn inner layer coil and an NbTi outer layer coil to detachably install or connect a pipe to the central through opening, What formed the flow path 31 may be used.

  The metal filaments loaded in the cleaning circulating fluid channel 31 are a single metal filament or an assembly of a plurality of metal filaments. The larger the surface area of the metal filaments, the more preferable for adsorbing the particles. The metal filament may be linear, curved, or pleated, and is preferably a metal bundle-like assembly, and may be subjected to shape crimping or surface unevenness processing. The wire diameter of the metal wire is 1 mm or less, preferably 0.5 mm or less, more preferably 0.3 mm or less, and still more preferably 0.1 mm or less. The smaller the wire diameter, the larger the magnetic flux gradient and the more easily magnetized to a magnetic force sufficient to attract the paramagnetic material. As the material of the metal wire, it can be used without particular limitation as long as it has corrosion resistance against cleaning chemicals and is a magnetizable metal, but is preferably a ferromagnetic material, for example, stainless steel such as SUS430 is preferable. Can be listed. By using a ferromagnetic metal filament, the magnetization of the metal filament itself is sustained after being magnetized by the superconducting magnet.

  As the applied magnetic field (magnetic flux density) by the superconducting magnet is larger, the ferromagnetic material and the paramagnetic material can be collected. The strength of the magnetic field is preferably 2T (Tesla) to 15T, and more preferably 6T to 10T.

  In the present invention, replacement of the metal filament loaded in the particle collecting device 3 is extremely simple. It is not necessary to drain the circulating cleaning fluid, and it is not necessary to desorb the collected sludge, and the metal filaments can be recovered. Next, since it can be restored as a particle collecting device simply by loading a similar new metal filament, there is no waste liquid to be discharged out of the system.

  In the chemical cleaning method and the particle collecting apparatus of the present invention, the cleaning chemical is not particularly limited. Organic mixed acids (citric acid + glycolic acid) and acidic or alkaline chemicals used in ordinary chemical cleaning methods can be used without limitation. Moreover, it is applicable not only to a chemical cleaning process but also to any one or more of the subsequent water washing process, rinsing process, neutralization process, rust prevention process, and final water washing process.

The application temperature range of the chemical cleaning method and the particle collecting apparatus of the present invention is not particularly limited as long as the cleaning circulating liquid can be circulated, and is typically 0 ° C to 150 ° C.
In the illustrated embodiment, the boiler is an oxygen treatment once-through boiler, but the cleaning object is not limited to this, and a chemical cleaning method is generally applied including a volatile substance treatment boiler. Applicable to all objects to be cleaned.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to these.

[Reference example]
Table 1 shows the results of measurement of mass magnetization using a physical property measurement device (PPMS, Nippon Quantum Design Co., Ltd.) after peeling off the actual scale of the boiler evaporator tube subjected to CWT treatment.

  As a pre-treatment of CWT actual scale, after physically removing the CWT scale with a wire brush and removing the wire mixed by sieving, it is put into a mixed solution of organic mixed acid (citric acid + glycolic acid) 8% + reducing agent And stirred at 90 ° C. for 30 minutes. The mass magnetization of the sample was measured.

  A feature of the ferromagnetic material is that when the external magnetic field is raised, the mass magnetization, which is a measured value, shows a rapid rise in the initial stage as shown in FIG. 5, and the magnetization eventually reaches saturation. On the other hand, a paramagnetic material such as hematite is characterized in that even when an external magnetic field is applied, the gradient of the mass magnetization rise is small and the magnetization is not saturated. The actual scale of CWT was found to have a ferromagnetic property because the mass magnetization was observed to show a sudden rise in the initial stage for both the inner layer scale and the outer layer scale (powder scale). From Table 1, the mass magnetization of powder scale at 10,000 Oe (approximately 1T) is small compared to magnetite, but very large compared to hematite. By increasing the magnetic field by the method of the present invention, not only magnetite but also hematite is obtained. Can be easily recovered.

[Example 1]
Using the particle collecting apparatus shown in FIGS. 3 and 4, 1 g of a SUS430 wire assembly having a wire diameter of 0.1 mm is loaded as the metal filament 32 into the cleaning circulating fluid flow path 2 and a charge is applied to the superconducting magnet 33. Then, after magnetizing the metal filament 32 to the applied magnetic field shown in Table 1, a commercially available magnetite reagent (average particle diameter in the liquid 1 μm) 2 ppm (mg / kg) was passed through at a flow rate of 0.5 m / s. The magnetite collection rate was determined. The collected amount was calculated by subtracting the initial weight from the weight of the metal filaments after collection, and the liquid passing amount was calculated as the recovered liquid amount.

[Example 2]
Collection of hematite in the same manner as in Example 1 except that a commercially available hematite reagent (average particle diameter in liquid 2 μm) 10 ppm (mg / kg) was passed through the particle collector at a flow rate of 0.5 m / s. The rate was determined. The results are shown in Table 3.

[Example 3]
The commercially available magnetite reagent used in Example 1 (average particle diameter in liquid 1 μm) and the commercially available hematite reagent used in Example 2 (average particle diameter in liquid 2 μm) were 2 ppm (mg / kg) and 1 ppm (mg / kg), respectively. kg), the total collection rate of magnetite and hematite was determined in the same manner as in Examples 1 and 2 except that the liquid mixed at a flow rate shown in Table 3 was passed. The results are shown in Table 4.

  In the chemical cleaning method and the particle collecting apparatus of the present invention, hematite that could not be collected by the conventional technique can be easily collected with a small environmental load. In the prior art, membrane filtration is required to collect hematite, which is physical collection by a filter, and the initial differential pressure is high, and a large amount of filter becomes waste. In the present invention, since the superconducting magnet gives the metal filament a high magnetic field and is collected by the magnetic force, the initial differential pressure is almost zero, and the particles sufficiently larger than the weight of the metal filament are dropped off. It can be recovered without any waste liquid. Further, depending on the type of boiler that is the object to be cleaned, a centrifugal separator, a coarse particle separation tank, and piping associated therewith are unnecessary, and the environmental load, temporary equipment, and piping scale can be reduced. In addition, the powder scale-derived sludge generated by chemical cleaning of oxygen-treated boilers is composed mainly of hematite, but is a composite crystal with magnetite and has the properties of a ferromagnetic material. Therefore, the chemical cleaning of the present invention is more effective than the case of hematite alone. The removal effect by the method and the particle collector is great.

Claims (8)

A chemical cleaning method for circulating a cleaning agent to an object to be cleaned,
Inject the cleaning chemical into the object to be cleaned, dissolve or peel off the metal oxide fixed to the object to be cleaned,
A cleaning circulation liquid flow path in which a single metal filament or an assembly of a plurality of metal filaments is installed and the metal in which the total amount of the cleaning circulation liquid containing the separated metal oxide particles, dissolved metal ions, and the cleaning agent is installed The liquid is passed through a particle collecting device including a superconducting magnet that magnetizes the filament, and the particles are magnetically adsorbed and removed by the magnetized metal filament, and then recycled to the object to be cleaned.
The chemical cleaning method characterized by the above-mentioned. Before passing the entire amount of the circulating cleaning fluid through the particle collecting device, the entire amount of the circulating circulating fluid is centrifuged to remove the metal oxide coarse particles, and the metal oxide fine particles, metal ions and 2. The chemical cleaning method according to claim 1, wherein the entire amount of the circulating cleaning fluid containing the cleaning chemical is passed through the particulate collection device. The chemical cleaning method according to claim 1 or 2, wherein the particles collected by the particle collecting device are magnetic particles selected from ferromagnetic, paramagnetic, or a combination thereof. The chemical cleaning method according to claim 3, wherein the ferromagnetic fine particles include magnetite. The chemical cleaning method according to claim 3, wherein the paramagnetic fine particles include hematite. The chemical cleaning method according to claim 1, wherein the object to be cleaned is a boiler that applies oxygen treatment to water supply treatment. The chemical cleaning according to any one of claims 2 to 6, wherein the coarse particles are particles having a particle size of more than 20 µm and not more than 40 µm, and the fine particles are particles having a particle size of 20 µm or less. Method. A particle collecting device used in a chemical cleaning method for circulating a cleaning agent to an object to be cleaned,
A particle collecting apparatus comprising: a cleaning circulating fluid channel loaded with a single metal filament or an assembly of a plurality of metal filaments; and a superconducting magnet that magnetizes the metal filament.