JP3044381B2 - Article cleaning method and apparatus - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for cleaning articles characterized by using a liquid combustible as a cleaning agent, and an apparatus used for the method.

[Prior art and its problems] Conventionally, halogenated hydrocarbons such as trichlene (trichloroethylene), perchrene (tetrachloroethylene), carbon tetrachloride, and chlorofluorocarbon (chlorofluorocarbon) have been widely used as washing liquids for articles. Since these halogenated hydrocarbons have detergency and are nonflammable, there is an advantage that there is no danger of fire and that they can be used safely.

However, trichlene, perclene, carbon tetrachloride, etc. are highly toxic to the body and pose a problem in terms of safety, and are subject to the Ministry of International Trade and Industry's Chemical Substances Control Law, )) Has been designated as a specific chemical substance since last year. On the other hand, CFCs have recently been restricted in use because they destroy the ozone layer in the stratosphere and adversely affect the environment. Instead, they have no toxicity to the body and are safe against fire. No cleaning agent has been proposed yet.

On the other hand, liquid hydrocarbons, such as isoparaffinic hydrocarbons and naphthenic hydrocarbons, are inexpensive, have relatively good detergency, are highly safe for living organisms, and have no concerns about ozone layer destruction. Is a preferred cleaning agent as a substitute for CFCs. However, it has the disadvantage of being inherently flammable. The same applies to oxygen-containing compounds such as alcohols in addition to these liquid hydrocarbons.

To avoid such fire danger, it is conceivable to set the oxygen concentration in the cleaning area such as the cleaning room to a value lower than the lower explosive limit of the cleaning agent. It is customary to introduce a nonflammable gas. However, reducing the oxygen concentration in the scrubbing zone usually requires a significant amount of non-combustible gas. In addition, it is actually not easy to obtain a large amount of nonflammable gas such as nitrogen gas, and even a simple nitrogen gas generator is not always inexpensive and can be obtained in large quantities.

On the other hand, combustion waste gas emitted from combustion engines such as incinerators and boilers for various combustibles is extremely clean without heavy metals and other foreign substances because it is subject to strict pollution regulations in recent years. In addition, so-called low oxygen operation is performed for the purpose of energy saving. That is, combustion is often performed without introducing excess air. This means that the residual oxygen concentration in the waste gas during combustion is extremely low.

[Problems to be Solved by the Invention] In view of the circumstances described above, the present inventors have considered flammable solvents such as hydrocarbons and oxygen-containing compounds which have been neglected because of the flammability and the danger of fire. In addition, the present inventors have made intensive studies for the purpose of effectively utilizing the combustion waste gas, and having a danger of fire, so that the human body can be safely washed, thereby completing the present invention.

[Means for Solving the Problems] That is, the present invention reduces the oxygen concentration in the cleaning zone atmosphere by introducing a combustion waste gas or an inert gas obtained by burning a combustible substance into the cleaning system. The present invention relates to a method for cleaning an article, characterized in that a liquid combustible material is used as a cleaning agent for cleaning while maintaining a value lower than a lower explosive limit (also referred to as a limit oxygen concentration).

Further, according to the present invention, an oxygen detector for detecting the oxygen concentration in the atmosphere in the cleaning area is installed, and the oxygen concentration in the atmosphere in the cleaning area is maintained at a value lower than the lower explosion limit of combustibles contained in the cleaning agent. The present invention relates to an article cleaning apparatus having a cleaning area for cleaning an article with a cleaning agent containing a combustible material. In addition, an introduction path of combustion waste gas from a combustion furnace that burns hydrocarbons and / or oxygen-containing compounds can be connected to the cleaning zone.

Hereinafter, the cleaning method and the apparatus according to the present invention will be described in detail with reference to the schematic process drawings.

<Object to be Washed> The article to be washed by the present invention is not particularly limited, but is preferably a metal or plastics mechanical part or product. Further, the shape, dimensions, and the like are not particularly limited.

<Cleaning Agent> An example of the steps of the cleaning method of the present invention is briefly shown in FIG.

The combustibles contained in the cleaning agent 1 used in the method of the present invention are compounds that burn by binding to oxygen in the air, that is, those whose lower explosion limit is lower than the oxygen concentration in the air. Liquid combustibles such as liquid hydrocarbons or liquid oxygenates such as alcohols, which are considered to be dangerous.

As the liquid hydrocarbon, liquid naphthenic hydrocarbons and isoparaffinic hydrocarbons can be used from the viewpoints of detergency, odor and safety to the body,
Those having a boiling point in the range of 70 to 280 ° C are preferred. kerosene,
Light oil, petroleum fraction hydrocarbons such as naphtha or aromatic hydrocarbons such as benzene, toluene and xylene are preferably avoided from the viewpoints of odors derived from aromatic compounds contained therein and safety to the human body. .
Of course, those containing these aromatic compounds may be used as long as they can be used in a method that covers these disadvantages. Liquid naphthenic hydrocarbons include trade name: Naphthesol L,
M and H (manufactured by Nippon Petrochemical Co., Ltd.) or terpenes such as limonene can be used. As the liquid isoparaffin-based hydrocarbon, commercially available products such as Nisseki Isosol 200, 300, and 400 (manufactured by Nippon Petrochemical Co., Ltd.) can be used.

Examples of the oxygen-containing compound include monohydric, dihydric or polyhydric alcohols, ethers, ketones, and esters, and alcohols are preferable because they are easy to handle. Suitable alcohols have a boiling point in the range of 60 to 280 ° C., and representative examples thereof include isopropyl alcohol.

In any case, those having an excessively low boiling point have a high volatility and a low flash point, so that even if the oxygen concentration is adjusted, there is a danger of fire, which is not preferable. In addition, those with a high boiling point
This is not preferable because drying after washing requires time.

The above liquid hydrocarbons, oxygen-containing compounds and the like can be used as a mixture.

When the object to be cleaned 2 is a metal machine part processed by cutting or polishing, it is contaminated with fine metal powder,
It is effective to add a surfactant to the detergent to remove them. Also, in other cases, a surfactant can be added to the cleaning agent as needed to improve the cleaning performance. As the surfactant, any of cationic, anionic, nonionic and amphoteric surfactants can be used. The amount of surfactant used is 0.00
The range is from 01 to 10% by weight, preferably from 0.001 to 1% by weight.

<Cleaning Step> Although the inside of the cleaning chamber 3 as a cleaning area is shut off from the outside air, it is not necessary to have a so-called air-tight structure, and it is only necessary to prevent sudden entry and exit of the outside air. That is, it is sufficient that the pressure is maintained at a normal pressure or a slightly pressurized state so that the outside air is not sucked and the oxygen concentration of the indoor atmosphere does not increase. Sending of the article to be cleaned 2 and sending to the next step are performed through a shutter 4 having an appropriate structure.

In the cleaning chamber 3, an appropriate number of cleaning tanks, for example, three cleaning tanks are provided. That is, the first cleaning tank 5 and the second cleaning tank 6
And a finish washing tank 7. At the start of the cleaning process, a new cleaning agent 1 is supplied to these cleaning tanks. Further, by introducing a combustion waste gas 8 described later into the cleaning chamber 3, the oxygen concentration in the cleaning chamber 3 is maintained at a concentration lower than the lower explosive limit of the cleaning agent. The amount and pressure of gas to be introduced
It can be appropriately determined according to the volume of the cleaning chamber 3, the number of cleaning tanks, and the like. Further, in addition to the combustion waste gas, an inert gas such as nitrogen gas or carbon dioxide gas supplied from a suitable inert gas generator or a supply source may be used in combination. Further, the oxygen concentration in the cleaning chamber 3 is measured by an appropriate oxygen concentration detector 9 and adjusted so that the concentration in the cleaning chamber 3 becomes lower than the lower explosive limit of the cleaning agent.

When the oxygen concentration in the atmosphere in the cleaning chamber 3 is higher than the lower explosive limit concentration, the combustion waste gas 8 or an inert gas is introduced into the system to lower the oxygen concentration.

The oxygen concentration at the lower explosion limit varies depending on the type of combustible vapor as a cleaning agent, temperature, pressure and other conditions.
It is necessary to confirm in advance by experiments and other means. Appropriate literature values can also be used. For example,
The lower explosion limit oxygen concentration (limit oxygen concentration) of flammable gases such as hydrogen, carbon monoxide, and acetylene is about 5%, but the lower explosion limit oxygen concentration of most other flammable liquid hydrocarbons is It is around 11-12% by volume. An oxygen-containing compound has a higher limit oxygen concentration.

The oxygen concentration as a set value when the method of the present invention is carried out is set to a value somewhat lower than the actual oxygen concentration at the lower limit of the explosion, for example, a value about 10% to 20% lower in consideration of safety. Is preferred. By keeping the oxygen concentration in the cleaning chamber 3 lower than such a value, an accidental explosion accident can be prevented.

Since the combustion waste gas introduced into the cleaning chamber 3 is originally discarded into the atmosphere, it may be released to the atmosphere as it is after the cleaning or after collecting and removing the cleaning agent vapor as needed.

In the cleaning operation, in order to improve the contact efficiency between the cleaning agent 1 and the object to be cleaned 2, the object to be cleaned 2 is not only immersed in the cleaning agent 1 but also moved up and down,
Alternatively, an arbitrary method such as stirring the cleaning agent 1 by a stirrer, applying ultrasonic vibration by the ultrasonic generator 10, circulating a pump, or flushing can be adopted.

The washing tank may be a single tank type, but if necessary, a two-tank type or a three-tank type as shown in the drawing. The cleaning can be performed efficiently by minimizing the amount of the cleaning liquid to be brought into the finishing cleaning tank 7 as much as possible. As the finish washing tank 7,
In addition to the stirring, the cleaning agent 1 is supplied from above by a shower method, or the cleaning agent 1 is supplied by spraying or jetting from three directions of up and down or 120 degrees.

In addition, when there are many stains of ionic substances or water-soluble stains, or when cleaning non-metallic articles, it is possible to wash with a detergent containing a surfactant and then with water.

The article to be cleaned 2 may be moved sequentially in a batch manner, or may be continuously moved by an appropriate conveyor.

<Drying Step> After the object to be cleaned 2 is washed in the washing step, the cleaning agent 1 attached to the washed article is dried and removed. Normally, the cleaning agent 1 is dried with hot air or hot air at a temperature lower than the flash point. Of course, if the oxygen concentration in the atmosphere within the drying step is maintained below the lower explosion limit as in the above-described cleaning step, hot air or hot air having a temperature higher than the flash point of the combustible material is sent through the heater 12 for drying. can do. In that case, the dryer 11 is provided in the drying chamber 13 and, similarly to the cleaning chamber 3, the combustion waste gas 8 or the inert gas is introduced, and
Adjust the oxygen concentration in 13 below the lower explosion limit of cleaning agent 1. Therefore, it is desirable to provide an appropriate oxygen concentration detector 9 also in the drying chamber 13.

Even if the object 2 to be cleaned is wet to some extent with the cleaning agent 1, depending on the type of the cleaning agent 2, it can be naturally dried by leaving it in the air. Further, when there is no problem in the subsequent processing and other steps, it is not particularly necessary to provide a drying step. For example, when performing a rust prevention treatment after washing a metal article, it is rather preferable that a hydrocarbon-based cleaning agent adheres to the metal surface, and in some cases, the rust prevention treatment is unnecessary. It can be economical.

In the above-mentioned washing step and drying step, the oxygen concentration detector 9 is used.
It is preferable to perform strict monitoring by the above-described method and automatically replenish combustion waste gas or inert gas when the oxygen concentration increases. In addition, a thermometer is installed in the system to monitor that the temperature of the device is below the flash point of the cleaning agent. If the temperature inside the device rises, low-temperature combustion waste gas or inert gas is used. Is preferably introduced.

<Cleaning Agent Recovery Step> After the object to be cleaned 2 is washed, the cleaning agent 1 can be discarded as it is. It is desirable to collect 1b, circulate it for the washing step and reuse it. In that case, when the waste cleaning agent 1a contains foreign matter, metal powder, moisture, or the like, it is preferable to remove the foreign matter in advance by an appropriate separator 15, such as a strainer or a trap.

<Combustion waste gas generation process> Combustion waste gas 8 for reducing the oxygen concentration in the cleaning process
As the source of supply, waste gas from incinerators that incinerate various industrial wastes such as plastics, paper, and wood, and combustion furnaces such as boilers that use oil fractions such as heavy oil and light oil as fuel can be used. In the present invention, preferably, the waste cleaning agent 1a or the residual liquid 1c obtained by collecting the cleaning agent 1b from the waste cleaning agent 1a is burned in the combustion furnace 16, and the combustion waste gas 8 discharged therefrom is used.

General combustion furnaces require dust, SO _X , N
Since O _X and the device for removing heavy metals providing normal,
Extremely clean combustion waste gas is emitted. Moreover, from the viewpoint of energy saving, the combustion furnace is operated by low oxygen operation without supplying an air amount larger than the theoretical air amount required for combustion, so the residual oxygen amount in the waste gas is reduced. Very low, in fact its concentration is of the order of a few percent by volume. Therefore,
By utilizing these combustion waste gases, i.e. simply by introducing a sufficient amount of said waste gases, it is possible to bring the oxygen concentration far below the lower explosive limit of the detergent.

Incidentally, an example of the composition of the combustion waste gas 8 obtained when burning hydrocarbons is shown.

Nitrogen 74.8% by volume Carbon dioxide 11.2% by volume Water 9.4% by volume Oxygen 4.6% by volume As described above, combustion waste gas 8 discharged from the combustion furnace 16
Is clean and has an oxygen concentration sufficiently lower than the limit oxygen concentration of ordinary liquid combustibles, so that it is suitable for use as an atmospheric gas in a cleaning step. However, since it contains water vapor and has a high temperature, before introducing the combustion waste gas 8 discharged from the combustion furnace 16 into the cleaning chamber 3 or the drying chamber 13, the cooler 17, the filter 18, and the moisture remover 19 are required.
It is preferable that the treatment is appropriately performed according to the above.

When the above combustion waste gas 8 is introduced into the cleaning chamber 3 and the drying chamber 13, if the oxygen concentration in these systems cannot be maintained at a value lower than the lower explosive limit of the cleaning agent, nitrogen is separately added. An inert gas such as gas or carbon gas can be additionally introduced.

[Effects of the Invention] According to the method and apparatus of the present invention, a cleaning operation using a combustible cleaning agent, which has conventionally been concerned about a fire, can be performed safely without worrying about occurrence of a fire. In addition, waste combustion gas that has been wasted can be effectively used.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples.

<Example 1> Using an isoparaffinic hydrocarbon (trade name “Nisseki Isosol 300”, manufactured by Nippon Petrochemical Co., Ltd.) as a cleaning agent, the object to be cleaned was moved in a batch manner according to the steps as shown in the figure. Then, the metal bearing balls cut and polished to a diameter of 10 mm were washed.

The properties of Nisseki Isosol 300 used are as follows.

Density (15 ° C, g / cm ³ ) 0.764 Flash point (PM, ° C) 55 Limiting oxygen concentration (%) 11 Initial boiling point (° C) 173 50% point (° C) 181 Dry point (° C) 189 Saturated hydrocarbon (Vol%) 99.8 or more The washing operation conditions are as follows.

Cleaning chamber oxygen concentration (%) 8-9 Temperature in cleaning tank (℃) 40 Cleaning chamber pressure (mmH ₂ O) 1-5 Amount of cleaning agent used (/ kg of object to be cleaned) 3 Cleaning time (min., 3 9) Oxygen concentration of combustion waste gas (%) 4.8 Supply amount of combustion waste gas (Nm ³ / hr, washing room m ³ ) 3 Drying room temperature (° C) 40 Wind speed of waste gas inlet (m / sec) 5 Drying time (minutes) As a result of the cleaning treatment for 15 minutes or more, metal powder, processing oil, etc. were completely removed, and the product was easy to dry. Further, the atmosphere in the cleaning room was not flammable.

<Example 2> A naphthenic hydrocarbon (trade name "Naphthesol M", manufactured by Nippon Petrochemical Co., Ltd.) was used as a cleaning agent, and Example 1 was used.
A cleaning test was performed in the same manner as described above.

The properties of Nisseki Naphthesol M used are as follows.

 Specific gravity (15/4 ° C) 0.815 Flash point (PM, ° C) 86 Limiting oxygen concentration (%) 11 Initial boiling point (° C) 290.5 50% point (° C) 217.5 Dry point (° C) 235.5 Naphthene (%) 75 or more The washing operation conditions are as follows.

Washing room oxygen concentration (%) 8-9 Washing tank temperature (℃) 60 Washing room pressure (mmH ₂ O) 1-5 Ultrasonic wave (kHz) 28 Cleaning agent usage (/ kg to be cleaned) 4 Washing between time (min., 3 bath total) 6 combustion exhaust gas oxygen concentration (%) 5.2 combustion exhaust gas supply amount (N · m ³ / hr · washing chamber m ³⁾ 3.5 drying chamber temperature (° C.) 60 exhaust gas inlet As a result of the cleaning treatment at a wind speed (m / sec) of 10 and a drying time of (min) of 15 or more, a clean cleaning product could be obtained as in Example 1. Further, the atmosphere in the cleaning room was not flammable.

<Example 3> A printed circuit board to which water-based dirt, solder flux, and the like are attached is cleaned in accordance with the steps shown in the figure using a hydrocarbon cleaning agent "1: 1 mixed solvent of naphthesol M and isopropyl alcohol." Was performed.

 The properties of the mixed solvent are as follows.

Density (15 ° C, g / cm ³ ) 0.803 Flash point (Tag, ° C) 25 or less Limiting oxygen concentration (%) 11 The cleaning operation conditions are as follows.

Wash chamber oxygen concentration (%) 8-9 cleaning tank temperature (° C.) 35 wash chamber pressure (mmH ₂ O) 1 to 5 detergent usage (/ object to be cleaned kg) 20 wash between time (min., 3 bath total) 6 combustion exhaust gas oxygen concentration (%) 5.1 combustion exhaust gas supply amount (N · m ³ / hr · washing chamber m ³⁾ 3 drying chamber temperature (° C.) 50 exhaust gas inlet wind velocity (m / sec) 5 As a result of the cleaning process with a drying time (min) of 10 or more, water-based stains and solder flux were completely removed, the product was easily dried, and a clean product was obtained. Further, the atmosphere in the cleaning room was not flammable.

Example 4 A mirror-finished metal part (piston ring) to which ionic dirt and dirt of fine metal particles adhered was cleaned. As a cleaning agent, the hydrocarbon cleaning agent Naphthesol M
And 0.5% of a commercially available anionic surfactant was used.

 The washing operation conditions are as follows.

Cleaning room oxygen concentration (%) 8-9 Cleaning tank temperature (℃) 60 Cleaning room pressure (mmH ₂ O) 1-5 Cleaning agent usage (/ kg to be cleaned) 1 Cleaning time (min., 3 bath total) 5 combustion exhaust gas oxygen concentration (%) 5.2 combustion exhaust gas supply amount (N · m ³ / hr · washing chamber m ³⁾ 4 drying chamber temperature (° C.) 60 exhaust gas inlet wind velocity (m / sec) 10 As a result of the cleaning treatment with a drying time (min) of 15 or more, ionic stains and stains of fine metal particles were completely removed, drying was easy, and a clean washed product was obtained. Further, the atmosphere in the cleaning room was not flammable.

[Brief description of the drawings]

FIG. 1 is a process chart for explaining the cleaning method of the present invention. DESCRIPTION OF SYMBOLS 1 ... Cleaning agent, 1a ... Waste cleaning agent 1b ... Recovered cleaning agent, 1c ... Recovered residual liquid 2 ... Cleaning object 3 ... Cleaning room 4 ... Shutter 5 ... First cleaning tank 6 … Second washing tank, 7… Finish washing tank 8… Combustion waste gas, 9 …… Oxygen concentration detector 10 …… Ultrasonic generator, 11… Dryer 12 …… Heater, 13… Dry room 14… Distillation tower, 15… Separator 16… Combustion furnace, 17… Cooler 18 …… Filter, 19 …… Moisture remover

Claims (4)

(57) [Claims] 1. The cleaning area is maintained at a normal pressure or a slightly pressurized state so as to prevent the oxygen concentration in the atmosphere of the cleaning area from being increased by sucking outside air, using a cleaning agent containing a combustible material, and cleaning. Cleaning the article while maintaining the oxygen concentration in the atmosphere of the region below 10% lower than the oxygen concentration of the cleaning agent at the lower explosive limit. 2. The use of a hydrocarbon-containing cleaning agent and introduction of at least a part of hydrocarbon combustion waste gas to reduce the oxygen concentration in the atmosphere in the cleaning zone to the oxygen concentration at the lower limit of the explosion of the cleaning agent. Cleaning the article while maintaining the value at a lower value. 3. An oxygen detector for detecting the oxygen concentration in the atmosphere in the cleaning area is installed, the cleaning area is kept at normal pressure or slightly pressurized, and the oxygen concentration in the atmosphere in the cleaning area is changed to the cleaning agent. 1 below the lower explosive limit of combustibles contained
An apparatus for cleaning articles, comprising a cleaning area for cleaning articles with a cleaning agent containing combustibles, the cleaning area being maintained at a value lower than a relatively low value. 4. An oxygen detector for detecting an oxygen concentration in the atmosphere in the cleaning area is provided, and the oxygen concentration in the atmosphere in the cleaning area is maintained at a value lower than the lower limit of the explosion limit of the cleaning agent. An article cleaning apparatus, comprising: a cleaning area for cleaning an article with a cleaning agent containing a hydrocarbon, wherein an introduction path of combustion waste gas from a combustion furnace for burning hydrogen is connected to the cleaning area.