JP2019002087A - Cleaning method of water storage part and cleaning method of circulation water system including water storage part - Google Patents

Abstract

To provide a cleaning method capable of reducing usage of cleaning agent used for cleaning of pulp and paper manufacturing equipment.SOLUTION: The invention provides a cleaning method for a water storage part of a pulp and paper manufacturing equipment A, wherein a cleaning agent is added to a water storage part 9, etc., in a state where a water is stored, and agitation is conducted using a water flow.SELECTED DRAWING: Figure 1

Description

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

  Papermaking is performed by making a raw material slurry in which pulp is dispersed in water. At that time, a large amount of white water containing fine fibers and filler is discharged from a paper machine or the like. This white water is circulated and used in the paper making process from the viewpoint of effective use and reuse of water resources. However, white water contains many organic substances such as fillers, starches, sizing agents, latexes, and caseins, so it is suitable for the growth of microorganisms such as bacteria and fungi. Slime, scale, and pitch derived from such microorganisms Origin deposits are likely to occur in the circulating water system. There is a concern that such deposits become defects when attached to the product, leading to a decrease in product yield.

  In addition, sediment accumulates at the bottom of the water storage section of pulp and paper manufacturing equipment, which can rot and produce malodorous substances, which can cause odors in the paper mill or adhere to the product. is there.

  In order to improve these problems, for example, it has been proposed to stop the operation of the equipment at a frequency of about once every several weeks to several months and perform cleaning using a cleaning agent (see Patent Document 1). Specifically, for circulating water containing the water reservoir, an alkaline agent such as sodium hydroxide as a cleaning agent, and hydrogen peroxide, a surface activity as a cleaning aid that constitutes the cleaning agent together with the cleaning agent Add water, mineral oil, chelating agent, etc., circulate water for about 1 to 3 hours, then drain. After that, the worker cleans the water reservoir and removes the remaining deposits. At this time, the cost of the cleaning aid used in combination with the cleaning agent is higher than that of the cleaning agent, and a reduction in the amount used has been required, but no drastic study has been conducted.

JP 2007-277769 A

  An object of the present invention is to solve such problems of the prior art. That is, the present invention provides a water storage unit cleaning method that enables reduction of the amount of cleaning agent used for cleaning pulp and paper manufacturing facilities, and a circulating water system cleaning method including the water storage unit. Objective.

The above object is solved by the present invention described below. That is, the water storage part cleaning method of the present invention is a water storage part cleaning method in pulp and paper manufacturing equipment,
A cleaning agent is added to the water storage part in a state where water is stored, and stirring by a water flow is performed.

  In the method for cleaning a water reservoir of the present invention, the agitation by the water flow can be agitation that generates a water flow at the bottom of the water reservoir or in the vicinity thereof.

  In the present invention, stirring by the water flow can be performed with an underwater stirrer.

  Moreover, in this invention, stirring by the said water flow can be performed with the nozzle attached to the water supply port to the said water storage part.

  On the other hand, the cleaning method of the circulating water system including the water storage part of the present invention is configured to apply a cleaning agent to the circulating water system including the water storage part while cleaning the water storage part by the above-described cleaning method of the water storage part of the present invention. It is characterized by having a stirring / circulation step of circulating the water it contains.

  Moreover, in the washing | cleaning method of the circulating water system containing the water storage part of this invention, it can have the drainage process which drains the water of the said circulating water system after the said stirring and circulation process.

  According to the water storage part cleaning method of the present invention and the circulating water system cleaning method including the water storage part of the present invention, the cleaning agent in a state where water is stored in the water storage part in the pulp and paper manufacturing facility. The amount of the cleaning aid used can be reduced by the configuration having the stirring and washing step of adding water and stirring with a water flow. Further, since the cleaning property is improved, it is possible to shorten the cleaning time and reduce or omit the burden of the cleaning work by the worker in the subsequent process.

It is a model figure which shows an example of the pulp and paper manufacturing equipment with which the washing | cleaning method of the water storage part of this invention and the washing | cleaning method of the circulating water system containing the water storage part of this invention are implemented. It is a model figure which shows the example of the stirring method by an underwater stirrer.

The present invention will be described below with reference to the drawings.
<Pulp and paper manufacturing equipment>
The water storage part cleaning method of the present invention is applied to the water storage part cleaning performed in pulp and paper manufacturing facilities in a paper mill.

  In the present invention, the “water storage section” of the pulp and paper production facility includes a water storage section such as a pulp selection system, a raw material adjustment system, a white water circulation system, a white water recovery system, and other areas around the coater. It means all the water reservoirs in the entire water circulation process, including the collection and reuse of aqueous solutions (so-called “white water”, etc.) discharged in large quantities at production facilities. White water usually contains fine fibers derived from raw pulp used during paper manufacture, other papermaking chemicals, and the like.

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

  First, raw pulp is washed with a washer 1 as a pulp selection system A1, then concentrated and dehydrated, and 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 bleach processor 3. Although not shown in FIG. 1, this pulp selection system A1 is provided with an aqueous water circulation line so that the used water can be reused.

  The raw material is adjusted by the raw material adjustment system A2 provided with the raw material adjustment tank 5 and the machine chest 6. That is, a raw material and water containing pulp from the high-concentration chest 4 are supplied to the raw material adjustment tank 5, and further water supplied from the recovered water tank 16 by the pump 17 is added to adjust the pulp slurry. The adjusted pulp slurry is supplied to the machine chest 6, and various papermaking chemicals such as a viscosity adjusting agent and a paper strength enhancer are added, and then supplied to the white water circulation system A 3 by the pump 7. Then, it is mixed with white water from the white water silo 9 (water containing some amount of the paper component), and is supplied to the inlet 10 as a paper material by the pump 8, and the wire 11 a that is rotationally driven from the inlet 10 to the wire part 11. Supplied to. The stock 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 pulp slurry containing various papermaking chemicals supplied by the pump 7 and supplied to the inlet 10 by the pump 8 to form the white water circulation system A3.

  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 and subjected to solid-liquid separation processing. The water of the components subjected to the solid-liquid separation treatment is stored in the recovered water tank 16, and then a part thereof is supplied to the raw material adjustment tank 5 of the raw material adjustment system A2 by the pump 17 and used for adjusting the concentration of the pulp slurry. Further, another part of the water is used for shower water for keeping the wire 11a of the wire part 11 and the felt of the press part 12 clean through a pipe (not shown). As reused. Thus, the white water recovery system A4, together with the pulp selection system A1, the raw material adjustment system A2, and the white water circulation system A3, constitutes the water system of the pulp and paper manufacturing facility, and water circulates in this circulation water system. Other part of the water in the recovered water tank 16 is discharged out of the system for concentration adjustment and sent to a wastewater treatment facility (not shown).

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

  In the pulp and paper manufacturing facility A of FIG. 1, the water storage part in which water is stored is not particularly limited, but the place where water temporarily stays, such as a water tank existing in the papermaking water system, is targeted. Specifically, in the water system in the pulp production facility, the concentrated dewatering pit 2, in the water system in the paper production facility, the machine chest 6, the white water silo 9, the seal pit 13, the recovered water tank 16, etc., and into the water system in the paper production facility In the water system to be used, the cushion tank 18 may be mentioned, but the water storage part in the present invention is not limited to these. For example, in order to supply water to the water storage part of the water system around the coater or the raw material adjustment tank, All the water storage parts existing in the water system in the pulp and paper manufacturing facility and the water system flowing into the water system, such as the prepared water pit, are included in the water storage part in the present invention.

  In FIG. 1, an example is shown in which the water in the water line 19 flowing into the circulating water system of 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 outside the circulating water system is supplied as dilution water for pulp and various papermaking chemicals, the water from the outside flows into the circulating water system of the pulp and paper manufacturing facility of the present invention. It is. In addition, you may collect | recover the water discharged | emitted from the process after papermaking processes, such as the press part 12, to the white water silo 9, the seal pit 13, etc. FIG.

[Washing method of water reservoir]
First, the method for cleaning the water storage part of the present invention will be described.

<Water reservoir>
In the washing method of the water storage part in the pulp and paper production facility 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) These water systems (hereinafter collectively referred to as “papermaking water systems”), and further, water storage portions existing in the water systems (reference numerals 18 to 20) flowing into these water systems are to be cleaned.

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

  These reduce the effectiveness of the slime control agent added to the aqueous system to prevent the generation of slime, which can be a drawback of the product. Therefore, the cleaning is usually performed by stopping the manufacturing apparatus regularly, for example, once a month. Specifically, production is discontinued, and for each water system, an alkaline cleaning agent such as sodium hydroxide as a main cleaning agent, and a cleaning aid containing an oxidizing agent such as hydrogen peroxide, a surfactant, mineral oil, etc. The water is circulated after usually circulating the aqueous water for 1 to 3 hours. In addition, it may heat in the case of circulation of this water.

  In such prior art cleaning, deposits often remain at the bottom of the water reservoir despite the circulation of aqueous water containing a cleaning agent. Therefore, it has been generally performed to clean the inside of the water storage part by an operator after cleaning.

<Agitation of water reservoir>
The water storage part cleaning method of the present invention is characterized in that the aqueous water in the water storage part is stirred by a water flow. The means for generating a water flow in the aqueous water in the water reservoir is not particularly limited, but it is preferable to perform stirring using an underwater agitator (underwater pump). In particular, it is possible to give a water flow into the water storage unit by simply putting an underwater stirrer into the water storage unit and driving it without attaching a pipe or a hose. Of course, you may attach piping, a hose, etc., and manage these suitably in water. In the example shown in FIG. 1, the submersible agitator S (lateral injection type) is provided in each of the concentration 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 that are water storage units. Are installed).

  Here, the underwater stirrer has the advantage that it can be installed in existing papermaking systems without extensive modifications. As the underwater stirrer, it is preferable to use a horizontal injection type or a downward injection type. When an upward jet type underwater stirrer is used, the force of the water flow that winds up the deposits is weak, making it difficult to obtain the effects of the present invention.

  In addition, piping work or installation of a pump may be required for installation, but a water flow may be generated by stirring a nozzle at the end of a line that supplies water to the water storage part. Of course, it is included in the category of “stirring by water flow” in the present invention. In this case, in particular, it is preferable to use a nozzle (for example, a liquid stirring nozzle EJX manufactured by Ikeuchi Co., Ltd.) having a hole for sucking in surrounding water on the side surface because a larger water flow can be obtained.

  In the present invention, for example, in the above-described example, water existing in 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, or a water system flowing into such a water system. Wash while stirring the reservoir. With such a configuration, the cleaning effect is enhanced as compared with the case where stirring is not performed, and the amount of cleaning aid added can be reduced. Therefore, it is preferable to perform washing while stirring in as many water storage units as possible, and further, in all the water storage units in these water systems, while taking into consideration economics and the like.

  The stirring by the water flow in the present invention is preferably stirring that generates a water flow at the bottom of the water reservoir or in the vicinity thereof. Specifically, it is preferable to generate a water flow toward the bottom of the water storage unit, or to generate a water flow that proceeds substantially parallel to the top of the bottom of the water storage unit. By generating a water flow at or near the bottom of the water reservoir, the effect of removing and cleaning the deposits deposited at the bottom of the water reservoir is exhibited, and the amount of deposits can be reduced. Therefore, the cleaning effect of the bottom part of the water storage part is enhanced.

  Here, taking the case of using an underwater stirrer as an example, several stirring methods, particularly examples of stirring methods for generating a water flow at or near the bottom of a water reservoir, will be described using the model diagram of FIG. To do.

  FIG. 2A shows an example in which a downward injection type is used as the underwater agitator 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. Since the water flow is directly generated toward the bottom of the water reservoir 30, the deposit removal effect is high.

  In FIG. 2 (b), a submerged jet type is used as the underwater stirrer S, and the submerged stirrer S is installed obliquely so that the water flow is directed obliquely downward, being arranged at a position slightly higher than the bottom of the water reservoir 30. This is an example. Also in this case, the water flow strikes the bottom of the water storage unit 30 obliquely and can be removed so as to remove the deposit, so that the deposit removal effect is high.

  FIG. 2C is an example in which a horizontal injection type is used as the underwater agitator S, as in FIG. 2B, and the water flow is installed sideways as it is approximately parallel to the bottom of the water storage unit 30. In this case, the water flow does not go to the bottom of the water storage unit 30, but the deposit can be removed so as to advance in the vicinity and sweep the deposit, so that the deposit removal effect is high.

  When a laterally-injected underwater agitator is installed in the bottomed cylindrical water reservoir 30 as shown in FIGS. 2B and 2C, as shown in FIG. 2D as a model. In addition, it is preferable that the water flow be installed along the inner peripheral surface of the water reservoir 30. By installing in this way, a water flow is produced in the whole bottom part, and the deposit removal effect of a wide area can be heightened.

  Further, as shown in model form in FIG. 2 (e), it is also preferable that the water flow be installed in a circular diametric direction in the vicinity of the bottom of the water reservoir 30. By installing in this way, the deposit removal effect can be most efficiently enhanced near the center of the bottom portion, and the deposit removal effect of the entire bottom portion can be enhanced.

  In any case, the type, capacity, installation position, etc. of the submerged stirrer may be appropriately selected so that the deposit cleaning and removing effects can be obtained as much as possible in accordance with the capacity and shape of the water reservoir. In these examples, one underwater stirrer S is installed in each water storage unit 30, but a plurality of submerged agitators S may be installed as necessary. Further, in order to enhance the cleaning effect, gas bubbles such as air may be blown into the water flow. Even when an apparatus other than the underwater stirrer is used as an apparatus for stirring by a water flow, the apparatus can be installed according to the contents described above.

  In order to realize the effect of cleaning / removing the sediment deposited on the bottom of the water reservoir at a high level, the flow velocity at the location where the sediment is easily deposited in the water reservoir is, for example, 0.5 m / second 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 facilities can be used. Many cleaning agents are composed of a cleaning agent and a cleaning aid. The cleaning agent is an alkaline cleaning agent such as sodium hydroxide, and the cleaning aid is hydrogen peroxide, a fatty acid derivative, a surfactant, phosphonic acid, or the like. Examples include chelating agents and mineral oils.

  Here, the hydrogen peroxide peels off deposits stuck to the wall surface and bottom surface of the apparatus and the water storage unit and the pipe. Fatty acid derivatives and surfactants act as detergents and contribute to the degradation of the sediment mass, and phosphonic acids act as chelating agents and solubilize to scale. Mineral oil removes oil stains in the presence of alkaline detergents.

  According to the method for cleaning a water reservoir of the present invention, in a general case, the amount of cleaning aid used is higher than that of the main cleaning agent and is about 1/3 to 2/3 that of the conventional cleaning method. The amount of reduction can be determined by confirming the actual cleaning state.

[How to wash the circulating water system]
Next, the cleaning method of the circulating water system including the water storage part of the present invention will be described.

<Aqueous water circulation>
In conventional cleaning methods, cleaning is performed while circulating aqueous water to which a detergent is added 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 an aqueous system near the coater. However, in the cleaning method of the present invention, it is preferable to circulate such aqueous water from the viewpoint of cleaning an aqueous part other than the water storage part, for example, pipes and equipment / devices. However, it is not always necessary to continue the circulation while stirring the water reservoir.

  For example, after the piping, equipment, and devices are cleaned in advance by circulation of the aqueous water, cleaning is performed only by stirring the water storage section, or cleaning by circulation of the aqueous water and cleaning by stirring of the water storage section are performed simultaneously. When the cleaning of piping, equipment and devices other than the water storage unit is completed by cleaning with the circulation of the aqueous system, the circulation of the aqueous system is stopped and only the cleaning by the stirring of the water storage unit is continued. An example is given.

<Washing time>
The cleaning time may be set by appropriately examining depending on the contamination state, stirring, the degree of circulation, the type of cleaning agent, etc., but according to the cleaning method of the present invention, the water storage unit is cleaned by stirring. Accordingly, it is possible to shorten the cleaning time as compared with the cleaning time by the conventional cleaning method.

<Cleaning after washing>
According to the method for cleaning a water storage part of the present invention, since the effect of cleaning is high, the time required for cleaning the water storage part conventionally performed after completion of cleaning and drainage can be greatly reduced, or Cleaning itself can be omitted.

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

  A person skilled in the art can appropriately modify the water storage part cleaning method and the circulating water system cleaning method including the water storage part of the present invention in accordance with conventionally known knowledge. Such modifications are still included in the scope of the present invention as long as the configuration of the water storage part cleaning method and the circulating water system cleaning method including the water storage part of the present invention are provided.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the water storage unit cleaning method and the circulating water system cleaning method including the water storage unit according to the present invention are not limited to this example.
In the following examples, various experiments were conducted in an existing pulp and paper manufacturing plant by appropriately remodeling the apparatus and stopping or operating the apparatus.

≪Study with underwater stirrer≫
Example 1
In a pulp and paper production facility that has been shut down for water-based cleaning, the following tests were conducted in a white water circulation system (conditions I to IV in Table 1 below) having white water silos (water amount: 20 m ³ ). Carried out. The pulp and paper manufacturing facilities are as described with reference to FIG. 1. In this example, the experiment was performed by washing the white water circulation system (A3) in FIG. The underwater stirrer was installed in the white water silo 9 in FIG.

<Agitator>
Among the white water silos, an underwater stirrer (SHG-101HS6 manufactured by Fuji Machinery Co., Ltd.) was installed at the bottom of each of the white water silos I and III of the white water circulation systems I and III so that the water flow was parallel to the bottom surface of the white water silo.

<Aqueous water circulation>
In the white water circulation systems I to IV, each of the aqueous water was circulated under the same conditions as in normal washing.

<Cleaning agent>
While maintaining the circulation of aqueous water, 100 L (liter) of 48 mass% sodium hydroxide aqueous solution (hereinafter also referred to as “48% NaOH”) as a cleaning main agent, and 35 mass% hydrogen peroxide water (hereinafter referred to as “cleaning aid”). , And 35% H ₂ O ₂ ), and AQUAS detergents (containing fatty acid derivatives, surfactants, phosphonic acids, mineral oils, hereinafter referred to as “detergents”) in this order. Then, the drug amount shown in Table 1 below was added.

<Washing>
Washing was performed by continuing circulation of each aqueous system for 2 hours after the addition of the above chemicals. During this time, in the white water circulation systems I and III, the underwater agitator in the white water silo was operated.

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

The conditions I to IV are conditions for the following purposes.
White water circulation system I: The present invention is applied under the same conditions as in the conventional (II).
White water circulation system II: Conventional circulation cleaning system.
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 circulation cleaning method (II).

  As shown in Table 1, in the white water circulation systems I and III that were cleaned by operating the underwater agitator of the white water silo, the deposits were removed by the cleaning, so that the cleaning work by the workers after the cleaning becomes unnecessary. It was. In addition, since sufficient cleanability was confirmed even in the white water circulation system III, it can be seen that the amount of cleaning aid used can be reduced by half. On the other hand, in the white water circulation systems II and IV in which no underwater stirrer was installed, cleaning work after washing was necessary. In addition, in the white water circulation system IV in which the amount of the cleaning aid was halved, the amount of remaining deposits was larger than that in the white water circulation system II, and the time taken for the cleaning work after washing was longer.

(Example 2)
After the above experiment, during the next cleaning of the white water circulation systems I and III, these white water circulation systems were performed in the same manner as in Example 1, except that only 35% H ₂ O ₂ as a cleaning aid and the addition amount of the cleaning agent were used. Was reduced to 6.6 kg and 6 kg, respectively, and the washing time was 90 minutes in the white water circulation system III, and both were washed while operating the underwater stirrer. In both of these white water circulation systems I and III, Sediment in the white water silo was removed and cleaning after cleaning was unnecessary. As a result, it was found that the amount of the cleaning aid used can be reduced by 2/3 and that the cleaning time can be shortened.

A An 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 Bleach processing 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 reservoir

Claims (6)

A method for cleaning a water reservoir in a pulp and paper manufacturing facility,
A cleaning method for a water storage part, wherein a cleaning agent is added to a water storage part in a state where water is stored, and stirring is performed by a water flow.   The method for cleaning a water storage unit according to claim 1, wherein the stirring by the water flow is stirring for generating a water flow at or near the bottom of the water storage unit.   The water storage unit cleaning method according to claim 1 or 2, wherein the stirring by the water flow is performed by an underwater stirrer.   The water storage unit cleaning method according to claim 1 or 2, wherein the stirring by the water flow is performed by a nozzle attached to a water supply port to the water storage unit.   Stirring / circulation in which water containing a cleaning agent is circulated in a circulating water system including the water reservoir while the water reservoir is cleaned by the method for cleaning a water reservoir according to any one of claims 1 to 4. A method for cleaning a circulating water system including a water storage part, comprising a step.   6. The method for cleaning a circulating water system including a water storage unit according to claim 5, further comprising a draining process of draining the water of the circulating water system after the stirring and circulating process.

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