JP6991000B2 - A method for cleaning the water reservoir and a method for cleaning the circulating water system including the water reservoir. - Google Patents

Description

The present invention relates to a method for cleaning a water reservoir in a pulp and paper manufacturing facility, and a method for cleaning a circulating water system including the water reservoir.

Papermaking is performed by making a raw material slurry in which pulp is dispersed in water, and at that time, a large amount of white water containing fine fibers and a filler is discharged from a paper machine or the like. From the viewpoint of effective utilization and reuse of water resources, this white water is circulated and used in the papermaking process. However, since white water contains a large amount of organic substances such as fillers, starches, sizing agents, latex, and casein, it is suitable for breeding microorganisms such as bacteria and fungi, and slime, scale, and pitch derived from such microorganisms. Derived deposits are likely to occur in circulating water systems. If such a deposit adheres to the product, it becomes a defect, and there is a concern that the product yield may decrease.

In addition, sediment accumulates at the bottom of the water reservoir of pulp and paper manufacturing equipment, which can spoil and generate malodorous substances, which can cause odors in paper mills or adhere to products. be.

In order to improve these problems, it has been proposed to stop the operation of the equipment and perform cleaning with a cleaning agent, for example, once every few weeks to several months (see Patent Document 1). Specifically, for circulating water system water including a water reservoir, an alkaline agent such as sodium hydroxide as a cleaning main agent, and hydrogen peroxide and surfactant as a cleaning auxiliary agent constituting the cleaning agent together with the cleaning main agent. Add an agent, mineral oil, a chelating agent, etc., circulate the water for about 1 to 3 hours, and then drain the water. After that, workers clean the water reservoir to remove the remaining sediment. At this time, the price of the cleaning aid used in combination with the cleaning main agent is higher than that of the cleaning main agent, and it has been required to reduce the amount used, but no drastic study has been conducted.

Japanese Unexamined Patent Publication No. 2007-277769

An object of the present invention is to solve such a problem of the prior art. That is, the present invention provides a method for cleaning a water reservoir and a method for cleaning a circulating water system including the water reservoir, which can reduce the amount of a cleaning agent used for cleaning pulp and paper manufacturing equipment. The purpose.

The above object is solved by the following invention. That is, the method for cleaning the water reservoir of the present invention is a method for cleaning the water reservoir in the pulp and paper manufacturing equipment that has stopped operation .
A cleaning agent is added to the water reservoir where the sediment is deposited at the bottom of the water reservoir, and the water flow is applied to the bottom of the water reservoir or its vicinity with a horizontal, downward, or diagonally downward water flow . It is characterized by performing agitation to generate it .

Further, in the method for cleaning the water storage portion of the present invention, the cleaning agent may be configured to contain an alkaline cleaning agent as a cleaning main agent .

In the present invention, the agitation by the water flow can be performed by an underwater agitator.

Further, in the present invention, stirring by the water flow can be performed by a nozzle attached to the water supply port to the water storage unit.

On the other hand, in the method for cleaning the circulating water system including the water storage portion of the present invention, the cleaning agent is applied to the circulating water system including the water storage portion while cleaning the water storage portion by the above-mentioned cleaning method for the water storage portion of the present invention. It is characterized by having a stirring / circulation step of circulating the contained water.

Further, in the method for cleaning a circulating water system including a water storage portion of the present invention, it is possible to have a drainage step of draining the water of the circulating water system after the stirring / circulation step.

According to the method for cleaning the water reservoir of the present invention and the method for cleaning the circulating water system including the water reservoir of the present invention, the cleaning agent in a state where water is stored in the water reservoir in the pulp and paper manufacturing facility. It is possible to reduce the amount of the cleaning aid used by the configuration having a stirring cleaning step of adding water and stirring with a water stream. Further, since the cleaning property is improved, the cleaning time can be shortened and the burden of cleaning work by the worker in the post-process can be reduced or omitted.

It is a model figure which shows an example of the pulp and paper manufacturing equipment which carries out the cleaning method of the water storage part of this invention, and the cleaning method of the circulating water system including the water storage part of this invention. It is a model figure which shows the example of the stirring method by the underwater stirrer.

The present invention will be described below with reference to the drawings.
<Pulp and paper manufacturing equipment>
The method for cleaning a water reservoir of the present invention is applied to cleaning a water reservoir carried out in a pulp and paper manufacturing facility in a paper mill.

In the present invention, the "water storage unit" of the pulp and paper manufacturing equipment includes a water storage unit such as a pulp selection system, a raw material adjustment system, a white water circulation system, a white water recovery system, and other coater peripherals, and includes pulp and paper. It means all the water storage parts in the entire water circulation process including the recovery and reuse system of the aqueous solution (so-called "white water" etc.) discharged in a large amount in the manufacturing equipment. White water usually contains fine fibers derived from raw material pulp used in paper production, other paper-making chemicals, and the like.

FIG. 1 shows a model diagram of Example A of a pulp and paper manufacturing facility used for explaining a method for cleaning a water reservoir and a method for cleaning a circulating water system including a water reservoir according to the present invention. It is not limited to an example.

First, as the pulp selection system A1, the raw material pulp is washed with a washer 1 and then concentrated and dehydrated, and the water generated by the dehydration is collected in the concentrated dehydration pit 2. On the other hand, the dehydrated pulp is temporarily stored in the high-concentration chest 4 after being bleached by the bleaching machine 3. Although omitted in FIG. 1, the pulp selection system A1 is provided with an aqueous water circulation line so that the water used can be reused.

The raw material is adjusted by the raw material adjusting system A2 provided with the raw material adjusting tank 5 and the machine chest 6. That is, the raw material containing pulp from the high-concentration chest 4 and water are supplied to the raw material adjusting tank 5, and the water sent from the recovered water tank 16 by the pump 17 is further added to prepare the pulp slurry. The prepared pulp slurry is supplied to the machine chest 6, various paper-making chemicals such as a viscosity modifier and a paper strength enhancer are added, and then supplied to the white water circulation system A3 by the pump 7. Then, it is mixed with white water (water containing a certain amount of paper material component) from the white water silo 9, supplied to the inlet 10 as a paper material by the pump 8, and the wire 11a of the wire part 11 is rotationally driven from the inlet 10. Is supplied to. The paper material supplied to the wire part 11 is dehydrated into a sheet shape, and is sent to the processes after the press part 12 to become a paper product. On the other hand, the water remaining in the wire part 11 is stored in the white water silo 9 as white water. The white water stored in the white water silo 9 is mixed with a pulp slurry containing various paper-making chemicals supplied by the pump 7 and supplied to the inlet 10 by the pump 8 to form the white water circulation system A3.

A part of the white water stored in the white water silo 9 is supplied from the white water silo 9 to the seal pit 13 of the white water recovery system A4. The white water supplied to the seal pit 13 is sent to the solid-liquid separation device 15 by the pump 14 for solid-liquid separation processing. After the water among the components that have been subjected to the solid-liquid separation treatment is stored in the recovered water tank 16, a part of the water is supplied to the raw material adjusting tank 5 of the raw material adjusting system A2 by the pump 17 and used for adjusting the concentration of the pulp slurry. And another part is used for shower water to keep the wire 11a of the wire part 11 and the felt of the press part 12 clean through a pipe (not shown). Will be reused as. As described above, the white water recovery system A4 constitutes the water system of the pulp and paper manufacturing equipment together with the pulp selection system A1, the raw material adjustment system A2, and the white water circulation system A3, and water circulates in the circulation water system. Some of the other water in the recovered water tank 16 is discharged to the outside of the system for concentration adjustment, and is sent to a wastewater treatment facility (not shown).

When the water in the pulp and paper manufacturing equipment A is insufficient, in this example, the water stored in the cushion tank 18 supplied from the water line 19 is supplied to the seal pit 13 by the pump 20. The solid content of the components separated by the solid-liquid separation device 15 is reused as a papermaking raw material or treated as waste.

In the pulp and paper manufacturing equipment A of FIG. 1, the water storage portion in which water is stored is not particularly limited, but a place where water temporarily stays, such as a water tank existing in these papermaking water systems, is targeted. Specifically, in the water system in the pulp manufacturing facility, the concentrated dehydration pit 2, in the water system in the paper manufacturing facility, the machine chest 6, the white water silo 9, the seal pit 13, the recovered water tank 16, etc., and inflow into the water system in the paper manufacturing facility. The water system includes a cushion tank 18, but the water storage unit in the present invention is not limited to these, for example, in the raw material adjustment system for supplying water to the water storage unit or the raw material adjustment tank of the water system around the coater. All the water storage portions existing in the water system in the pulp and paper manufacturing equipment and the water system flowing into the water system, such as the prepared water pit, are included in the water storage unit in the present invention.

FIG. 1 shows an example in which the water of the water line 19 flowing into the circulating water system in the papermaking process is supplied to the seal pit 13, but the supply location is not limited to the seal pit 13. For example, when water from an outside other than the above-mentioned circulating water system is supplied as diluting water for pulp and various paper-making chemicals, the water from the outside flows into the circulating water system of the pulp and paper manufacturing equipment of the present invention. Is. The water discharged from the process after the papermaking process of the press part 12 or the like may be collected in the white water silo 9, the seal pit 13, or the like.

[How to clean the water reservoir]
First, a method for cleaning the water storage portion of the present invention will be described.

<Water storage>
In the method for cleaning the water storage portion in the pulp and paper manufacturing equipment of the present invention, the pulp selection system (A1), the raw material adjustment system (A2), the white water circulation system (A3), the white water recovery system (A4), or the periphery of the coater (not shown). (Hereinafter, these are collectively referred to as "papermaking water system"), and further, the water storage portion existing in the water system (reference numerals 18 to 20) flowing into these water systems is subject to cleaning.

In the water reservoir, solids and suspended solids contained in water are deposited on the bottom. Since the vicinity of the sediments deposited in this way or the inside of the sediment layer formed by stacking the sediments is rich in organic matter, it becomes a hotbed for microorganisms such as bacteria and becomes anaerobic, and is a metabolite of microorganisms. As a result, reducing substances such as hydrogen sulfide and methyl mercaptan will be produced.

These reduce the effectiveness of slime control agents added to the water system to prevent the generation of slime, which can be a drawback of the product. Therefore, the manufacturing apparatus is usually stopped and cleaned regularly, for example, once a month. Specifically, production will be discontinued, and for each water system, alkaline cleaning agents such as sodium hydroxide and cleaning aids containing oxidizing agents such as hydrogen peroxide, surfactants, mineral oils, etc. will be used as cleaning main agents. Is added, and the aqueous water system is circulated for 1 to 3 hours, and then drained. In addition, it may be heated during the circulation of this water.

In such conventional cleaning, deposits often remain at the bottom of the water reservoir despite the circulation of water-based water containing a cleaning agent. Therefore, it has been common practice for workers to clean the inside of the water storage section after cleaning.

<Stirring of water reservoir>
The method for cleaning the water storage portion of the present invention is characterized in that the water-based water in the water storage portion is agitated by a water flow. There is no particular limitation as a means for generating a water flow in the water system water in the water reservoir, but it is preferable to perform stirring using a submersible agitator (submersible pump). In particular, it is possible to give a water flow to the water storage unit by simply putting the submersible stirrer into the water storage unit and driving it without attaching a pipe or a hose. Of course, pipes, hoses, etc. may be attached and these may be appropriately routed in water. In the example shown in FIG. 1, the submersible stirrer S (horizontal injection type) is provided in each of the concentrated dehydration pit 2, the machine chest 6, the white water silo 9, the seal pit 13, the recovered water tank 16, and the cushion tank 18, which are water storage portions. Things) are installed.

Here, the submersible stirrer has the advantage that it can be installed in an existing papermaking system without major modification. As the submersible stirrer, it is preferable to use a horizontal injection type or a downward injection type. When an upward injection type submersible stirrer is used, the force of the water flow that winds up the sediment is weak, and it becomes difficult to obtain the effect of the present invention.

In addition, plumbing work and pump installation may be required for installation, but water flow may be generated and agitated by attaching a nozzle to the tip of the line that supplies water to the water storage section. In this case. Of course, it is included in the category of "stirring by water flow" in the present invention. In this case, it is particularly preferable to use a nozzle having a hole for sucking the surrounding water on the side surface (for example, a nozzle EJX for liquid stirring manufactured by Ikeuchi Co., Ltd.) because a larger water flow can be obtained.

In the present invention, for example, in the above example, a water system composed of a pulp selection system, a raw material adjustment system, a white water circulation system, or a white water recovery system, a water system near a coater, and water existing in a water system flowing into such a water system. Cleaning is performed while stirring the reservoir. With such a configuration, the cleaning effect is enhanced and the amount of the cleaning aid added can be reduced as compared with the case where no stirring is performed. Therefore, it is preferable to perform cleaning while stirring as many water storage units as possible, and all water storage units in these water systems, while considering economic efficiency and the like.

As the stirring by the water flow in the present invention, it is preferable that the stirring is such that a water flow is generated at or near the bottom of the water storage portion. Specifically, it is preferable to generate a water flow toward the bottom of the water storage portion or to generate a water flow that travels substantially in parallel just above the bottom of the water storage portion. By creating a water flow at or near the bottom of the water reservoir, the effect of removing and cleaning the deposits deposited on the bottom of the water reservoir is exhibited, and the amount of deposits can be reduced. Therefore, the cleaning effect of the bottom of the water storage portion is enhanced.

Here, taking the case of using an underwater agitator as an example, some agitation methods, particularly an example of a agitation method for generating a water flow at or near the bottom of the water reservoir, will be described using the model diagram of FIG. do.

FIG. 2A is an example in which a downward injection type is used as the submersible stirrer S. In this example, an underwater stirrer S is installed in the center of the water storage unit 30, and a water flow is generated toward the bottom immediately below the submersible stirrer S. Since the water flow is directly generated toward the bottom of the water storage portion 30, the effect of removing deposits is high.

In FIG. 2B, a horizontal injection type water stirrer S is used, arranged at a position slightly higher than the bottom of the water storage unit 30, and the water stirrer S is installed diagonally so that the water flow faces diagonally downward. This is an example. In this case as well, the water flow hits the bottom of the water storage portion 30 diagonally and can be removed so as to dispel the deposits, so that the effect of removing the deposits is high.

FIG. 2C is an example in which, as in FIG. 2B, a horizontal injection type water stirrer S is used and the water flow is installed sideways as it is so as to be substantially parallel to the bottom of the water storage unit 30. In this case, the water flow does not go toward the bottom of the water reservoir 30, but it can be removed in the vicinity thereof as if sweeping the sediment, so that the effect of removing the sediment is high.

When a horizontal injection type submersible stirrer is installed in the bottomed cylindrical water storage section 30 as shown in FIGS. 2 (b) and 2 (c), as shown in FIG. 2 (d) as a model. In addition, it is preferable to install the water flow along the inner peripheral surface of the water storage unit 30. By installing in this way, it is possible to generate a water flow over the entire bottom and enhance the effect of removing deposits over a wide area.

Further, as shown as a model in FIG. 2 (e), it is also preferable to install the water flow so as to be directed in the circular radial direction near the bottom of the water storage portion 30. By installing in this way, the sediment removal effect can be most efficiently enhanced near the center of the bottom, and the sediment removal effect of the entire bottom can be enhanced.

In any case, the type, capacity, installation position, etc. of the underwater agitator may be appropriately selected so that the effect of cleaning and removing the deposits can be obtained as much as possible according to the capacity and shape of the water reservoir. Further, in these examples, one submersible stirrer S is installed in each of the water storage units 30, but a plurality of submersible stirrers S can be installed as needed. Further, in order to enhance the cleaning effect, bubbles of gas such as air may be blown into the water stream. Even when a device other than the underwater agitator is used as the device for agitating by the water flow, it can be installed according to the contents described above.

In order to realize the effect of cleaning and removing the sediments deposited on the bottom of the water reservoir at a high level, the flow velocity at the place where the sediments are likely to be deposited in the water reservoir is, for example, 0.5 m / sec or more. It is preferable to do so.

<Cleaning agent>
As the cleaning agent used in the present invention, various cleaning agents used for cleaning pulp and paper manufacturing equipment can be used. Many cleaning agents are composed of a cleaning main agent and a cleaning auxiliary, and the cleaning main agent is an alkaline cleaning agent such as sodium hydroxide, and the cleaning auxiliary agent is hydrogen peroxide, a fatty acid derivative, a surfactant, a phosphonic acid, or the like. Examples include chelating agents and mineral oils.

Here, hydrogen peroxide exfoliates the deposits stuck on the wall surface and bottom surface of the device and the water storage part, and in the pipe. Fatty acid derivatives and surfactants act as detergents and contribute to the decomposition of sediment masses, while phosphonic acids act as chelating agents for scale and solubilize. Mineral oil removes oil stains in the presence of an alkaline cleaner.

According to the method for cleaning the water reservoir of the present invention, in a general case, the amount of the cleaning aid, which is more expensive than the main cleaning agent, is about 1/3 to 2/3 as compared with the conventional cleaning method. It is possible to reduce the amount, but the amount of reduction may be determined by confirming the actual cleaning condition.

[Washing method for circulating water system]
Next, a method for cleaning the circulating water system including the water storage portion of the present invention will be described.

<Circulation of water system>
In the conventional cleaning method, when cleaning a water system composed of a pulp selection system, a raw material adjustment system, a white water circulation system, a white water recovery system, and a water system near a coater, the water system to which a cleaning agent is added is circulated for cleaning. However, even in the cleaning method of the present invention, it is preferable to perform such circulation of water-based water in that water-based parts other than the water storage portion, for example, pipes, equipment / devices can be cleaned. However, it is not always necessary to continue circulation while stirring the water reservoir.

For example, after cleaning pipes, equipment / devices, etc. by circulating water-based water in advance, only the water storage unit is cleaned by stirring, or cleaning by circulating water-based water and cleaning by stirring the water storage unit are performed at the same time. When the cleaning of pipes, equipment, etc. other than the water storage part is completed by cleaning by the circulation of water-based water, the circulation of water-based water is stopped and only the cleaning by stirring of the water storage part is continued. An example is given.

<Washing time>
The cleaning time may be appropriately examined and set according to the state of contamination, stirring, the degree of circulation, the type of cleaning agent, etc., but according to the cleaning method of the present invention, cleaning by stirring the water reservoir is performed. As a result, it is usually possible to shorten the cleaning time as compared with the cleaning time by the conventional cleaning method.

<Cleaning after cleaning>
According to the method for cleaning the water reservoir of the present invention, the effect of cleaning is high, so that the time required for cleaning the water reservoir, which has been conventionally performed after the completion of cleaning and drainage, can be significantly shortened, or Cleaning itself can be omitted.

Although the present invention has been described above with reference to preferred embodiments, the method for cleaning the water reservoir and the method for cleaning the circulating water system including the water reservoir of the present invention are limited to the configuration of the above embodiment. is not it.

Those skilled in the art can appropriately modify the method for cleaning the water reservoir of the present invention and the method for cleaning the circulating water system including the water reservoir according to the conventionally known knowledge. Even with such a modification, it is, of course, included in the category of the present invention as long as it has the configuration of the method for cleaning the water storage portion of the present invention and the method for cleaning the circulating water system including the water storage portion.

Hereinafter, the present invention will be described in more detail with reference to examples, but the method for cleaning the water reservoir and the method for cleaning the circulating water system including the water reservoir of the present invention are not limited to this embodiment.
In the following examples, various experiments were conducted in an existing pulp and paper manufacturing plant by appropriately modifying the equipment and stopping or operating the equipment.

≪Examination by submersible stirrer≫
(Example 1)
In a pulp and paper manufacturing facility that was shut down for cleaning the water system, the following tests were performed with a white water circulation system (conditions I to IV in Table 1 below) having a white water silo (water volume: 20 m ³ ). Carried out. The pulp and paper manufacturing equipment was as described with reference to FIG. 1, and in this example, the experiment was carried out by washing the white water circulation system (A3) in FIG. The underwater stirrer was installed in the white water silo 9 in FIG.

<Stirrer>
Of the white water silos, a submersible stirrer (SHG-101HS6 manufactured by Fuji Machinery Co., Ltd.) was installed at the bottom of the white water silos I and III of the white water circulation system I and III so that the water flow was parallel to the bottom surface of the white water silo.

<Circulation of water system>
In the white water circulation system I to IV, the water system water was circulated under the same conditions as in the normal washing.

<Cleaning agent>
While maintaining the circulation of aqueous water, 100 L (liter) of 48% by mass sodium hydroxide aqueous solution (hereinafter, also referred to as "48% NaOH") as a cleaning main agent, and 35% by mass hydrogen peroxide solution (hereinafter, also referred to as "48% NaOH") as a cleaning aid. , "35% H ₂ O ₂ "), and a cleaning agent manufactured by Aquas (containing a fatty acid derivative, a surfactant, a phosphonic acid, and a mineral oil; hereinafter referred to as a "cleaning agent") in this order. Then, it was added so as to have the amount of the drug shown in Table 1 below.

<Washing>
After the addition of the above chemicals, the water system water was continuously circulated for 2 hours for washing. During this period, the underwater stirrer in the white water silo was operated in the white water circulation systems I and III.

<Evaluation>
After draining the water system water in the white water circulation system I to IV, the bottom surface of the white water silo of the white water circulation system was observed, and the presence or absence of deposits and the necessity of cleaning by the worker after cleaning were investigated. The results are summarized in Table 1 below.

The conditions I to IV are for the following purposes.
White water circulation system I: The present invention is applied under the same conditions as the conventional (II).
White water circulation system II: Conventional circulation cleaning method.
White water circulation system III: The present invention is applied after halving the amount of cleaning aid from the conventional (II).
White water circulation system IV: The amount of cleaning aid is halved with the conventional (II) circulation cleaning method.

As shown in Table 1, in the white water circulation systems I and III, which were washed by operating the underwater stirrer of the white water silo, the deposits were removed by the washing, so that the cleaning work by the worker after the washing became unnecessary. rice field. In addition, since sufficient detergency was confirmed in the white water circulation system III, it can be seen that the amount of the cleaning aid used can be reduced by half. On the other hand, in the white water circulation system II and IV in which the underwater stirrer was not installed, cleaning work after cleaning was required. The white water circulation system IV, in which the amount of the cleaning aid was halved, had more residual deposits than the white water circulation system II, and the cleaning work after cleaning took longer.

(Example 2)
After the above experiment, at the next cleaning of the white water circulation systems I and III, the same as in Example 1 in these white water circulation systems, but only 35% H ₂ O ₂ of the cleaning aid and the amount of the cleaning agent added. Was reduced to 6.6 kg and 6 kg, respectively, and the washing time was set to 90 minutes in the white water circulation system III, and both were washed while operating the underwater stirrer. Both of these two white water circulation systems I and III were washed. The deposits in the white water silo were removed and no cleaning was required after cleaning. It was found that this can reduce the amount of cleaning aid used by 2/3 and shorten the cleaning time.

A Example of pulp and paper manufacturing equipment A1 Pulp selection system A2 Raw material adjustment system A3 White water circulation system A4 White water recovery system 1 Washer 2 Concentrated dehydration pit 3 Bleaching machine 4 High concentration chest 5 Raw material adjustment tank 6 Machine chest 7, 8, 14 , 17, 20 Pump 9 White water silo 10 Inlet 11 Wire part 11a Wire 12 Press part 13 Seal pit 15 Solid-liquid separator 16 Recovery water tank 18 Cushion tank 19 Water line 30 Water storage

Claims (6)

It is a method of cleaning the water storage part in the pulp and paper manufacturing equipment that has stopped operation .
A cleaning agent is added to the water storage part where the sediment is deposited at the bottom of the water storage part, and the water flow is applied to the bottom of the water storage part or its vicinity with a horizontal, downward, or diagonally downward water flow . A method for cleaning a water reservoir, which comprises performing agitation to generate the water. The method for cleaning a water reservoir according to claim 1, wherein the cleaning agent contains an alkaline cleaning agent as a cleaning main agent. The method for cleaning a water storage portion according to claim 1 or 2, wherein the stirring by the water flow is performed by an underwater stirrer. The method for cleaning a water storage unit according to claim 1 or 2, wherein stirring by the water flow is performed by a nozzle attached to a water supply port to the water storage unit. By the method for cleaning the water storage unit according to any one of claims 1 to 4, the water storage unit is cleaned, and the water containing the cleaning agent is circulated in the circulating water system including the water storage unit. A method for cleaning a circulating water system including a water reservoir, which comprises a step. The method for cleaning a circulating water system including a water storage unit according to claim 5, further comprising a drainage step of draining the water of the circulating water system after the stirring / circulation step.

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