JPH06264384A - Bleaching equipment for medium density pulp - Google Patents

Abstract

(57) [Summary] [Purpose] To obtain pulp of any Kappa number. [Structure] A storage tank 4 for storing the medium-concentration pulp after washing is provided. Downstream of the storage tank 4, the first
Mixer 7, first blow tank 11, second mixer 1
5, reactor 19, and second blow tank 22 are sequentially installed. A circulation pipe 20 is provided between the reactor 19 and the first blow tank 11. 1 sent from storage tank 4
A batch of pulp is circulated between the reactor 19 and the first blow tank 11, and a reaction regulator is added in each case, and the reaction is carried out in several stages.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bleaching apparatus for medium density pulp used as a papermaking stock.

[0002]

2. Description of the Prior Art Medium-concentration pulp that has been cooked and washed is
Usually, it has a yellow or brown color, so that a bleaching step is required to remove these coloring substances or to decompose them to make them colorless and give pure white pulp.

A conventional medium density pulp bleaching apparatus is as follows.
As shown in FIG. 2 as an example, an alkali (oxidized white liquor, N
a pulp such as aOH) b having a concentration of 10 to 15% is mixed with the low pressure steam d by the first mixer c, and then sent to the second mixer j by the high concentration pump g,
Here, the medium pressure steam e and oxygen f as a bleaching agent are mixed and sent to the reactor h, and further, the pulp after the reaction work in the reactor h is sent to the blow tank i so that the bleaching treatment is continuously performed. It will be done in.

[0004]

However, in the above conventional bleaching apparatus for medium-concentration pulp, the reaction rate of oxygen f in the pulp for delignification in the pulp is relatively fast (for example, about 20 minutes). However, since the entire apparatus is configured in a continuous manner, the reactor h has a margin in order to sufficiently carry out the reaction (for example, 40 to 6).
0 minutes) needed. It has been conventionally known that the delignification rate can be increased by dividing the reaction of oxygen f with delignification in pulp into several stages.
Since the pulp is treated continuously, various reaction conditions such as chemical addition rate and reaction time cannot be freely controlled, and any Kappa number (residual lignin amount)
Was difficult to obtain. Further, in the case of ozone bleaching of medium-concentration pulp, in order to efficiently react ozone with lignin, the addition amount is one stage and 0.3 to 0.4% per pulp is the limit. Therefore, it is necessary to repeat several steps in order to obtain an arbitrary Kappa number.

Therefore, the present invention makes it possible to freely control various reaction conditions such as the reaction time of each stage and the chemical addition rate by using the bleaching process as a batch cycle.
It is intended to obtain pulp having practically any Kappa number.

[0006]

In order to solve the above-mentioned problems, the present invention provides a storage tank for storing a medium-concentration pulp after washing and delivering it to one batch. Downstream, first via respective transfer pipes
A mixer, a first blow tank, a second mixer, a reactor and a second blow tank are installed, and a circulation pipe for circulating pulp is connected between the outlet of the reactor and the inlet of the first blow tank. In addition, a first reaction adjusting agent supply pipe for supplying a first reaction adjusting agent to the first mixer is provided, and a bleaching agent supply pipe and a second reaction adjusting agent for supplying a bleaching agent to the second mixer are supplied. The second reaction control agent supply pipe is provided.

[0007]

The pulp for one batch fed from the storage tank is put into the reactor through the first mixer, the first blow tank and the second mixer to carry out the bleaching reaction.
Next, this pulp is returned to the first blow tank by a circulation pipe, and then sent to the reactor with the required bleaching agent and reaction modifier added, and the reaction is performed again. The pulp, which has been circulated and reacted the required number of times in the same process, is sent to the second blow tank for storage. Thereafter, similarly, the pulp is subjected to the reaction for one batch and stored.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.
A first high-concentration pump 2 is provided downstream of the bleached pulp washing machine 1.
Storage tank 4 is installed via the transfer pipe 3
The pulp with a concentration of 10 to 15% after being washed in the machine 1
The storage tank 4 can be stored in the storage tank 4.
Downstream of the storage tank 4, the first steam pipe 5 and the first reaction
The first mixer 7 connected to the adjusting agent supply pipe 6 is connected to the second high concentration
Installed via a transfer pipe 9 equipped with a pump 8
The first part of the pulp stored in the storage tank 4
The first mixer is configured to be fed to the mixer 7.
-1 downstream of the first blow tank 11 via the transfer pipe 10.
By installing the low pressure steam and the first steam pipe 5
Mix the first reaction modifier through the 1 reaction modifier supply pipe 6
Pulp from the first mixer 7 to the first blow tank 11
Of the first blow tank 11
Downstream, the second steam pipe 12, the bleach supply pipe 13, and the second
The second mixer 15 to which the reaction adjusting agent supply pipe 14 is connected,
Connection via a transfer pipe 17 equipped with a third high-concentration pump 16
The pulp in the first blow tank 11 into the second mixer.
-15, the second mixer 1
5, a reactor 19 is installed downstream of 5 through a transfer pipe 18.
The medium pressure steam and bleach with the second steam pipe 12.
By the bleaching agent via the supply pipe 13 and the second reaction adjusting agent supply pipe 14,
The pulp mixed with the reaction modifier
From the above to the reactor 19, and
Outlet of the reactor 19 and inlet of the first blow tank 11
A circulation pipe 20 is connected between the
The pulp is sequentially transferred to the circulation pipe 20, the first blow tank 11 and the transfer.
Reactor via feed pipe 17, second mixer 15, transfer pipe 18
To be circulated in the rear part 19
A second blow tank is provided downstream of the engineer 19 via a transfer pipe 21.
Install the reactor 22 and terminate the reaction in the reactor 19.
After the pulp is sent to the second blow tank 22 for storage.
To be able to

A level meter 23 is attached to the lower portion of the storage tank 4, and the transfer pipe 9, the first steam pipe 5, the first reaction adjusting agent supply pipe 6, the circulation pipe 20, and the transfer pipe 2 are provided.
1, control valves 24, 25, 26,
27 and 28 are provided, and a control device 29 for controlling the level meter 23 and the control valves 24 to 28 is further provided.

In the present invention, the storage tank 4 has a capacity of 1.5 times or more that of the batch cycle (for example, 5 to 30 minutes) in order to process pulp in a batch system.

When bleaching the pulp washed by the unbleached pulp washing machine 1, first, the pulp in the unbleached pulp washing machine 1 is sent into the storage tank 4 by the first high-concentration pump 2 through the transfer pipe 3. . Next, the pulp in the storage tank 4 is fed by the second high-concentration pump 8 through the transfer pipe 9 to the first mixer 7 for one batch, and the second high-concentration pump 8 is supplied.
Is stopped and the remaining pulp is stored in the storage tank 4.

In the first mixer 7, low-pressure steam supplied through the first steam pipe 5 and alkali (oxidized white liquor, NaOH, etc.) as the first reaction modifier supplied through the first reaction modifier supply pipe 6 ) Or an acid (sulfuric acid, oxalic acid, etc.) is mixed into the pulp, and the pulp is once stored in the first blow tank 11 via the transfer pipe 10.
Subsequently, the pulp contained in the first blow tank 11 is sent by the third high-concentration pump 16 to the second mixer 15 through the transfer pipe 17, where the medium pressure steam supplied through the second steam pipe 12 and the bleaching are carried out. Oxygen or ozone as a bleaching agent supplied through the agent supply pipe 13 is mixed, and then, supplied to the reactor 19 through the transfer pipe 18.

Next, one batch of pulp after carrying out a predetermined reaction in the reactor 19 is passed through the circulation pipe 20 to the first
It is discharged into the blow tank 11 and further transferred to the transfer pipe 17 and the second
Reactor 19 via mixer 15 and transfer pipe 18
And the reaction is again performed in the reactor 19. At this time, in order to carry out a desired reaction in the reactor 19, if necessary, the second mixer 15
A necessary amount of reaction modifier such as alkali (oxidizing white liquor, NaOH, etc.) and acid (sulfuric acid, oxalic acid, etc.) is supplied through the second reaction modifier supply pipe 14, and oxygen and ozone are supplied by the bleaching agent supply pipe 13. To supply.

After repeating the above circulation reaction a required number of times, 1
The batch of pulp is discharged from the reactor 19 through the transfer pipe 21 to the second blow tank 22 for storage. Further, in a similar process, one batch of the pulp stored in the storage tank 4 is supplied, and the pulp is sequentially circulated in the reactor 19 to be accommodated in the second blow tank 22. The above steps are performed by opening and closing the control valves 24, 25, 26, 27, 28 and the like of the respective parts according to a command from the control device 29.

As described above, in the present invention, since the pulp can be reacted in several stages by using the bleaching step as a batch cycle, the reaction time of each stage and the chemical addition rate of the bleaching agent, the reaction modifier, etc. The reaction conditions of can be freely controlled.

Although the pulp from the unbleached pulp washer 1 is sent to the storage tank 4 in the above embodiment, a thickener is used instead of the unbleached pulp washer 1. This is arbitrary, and it goes without saying that various changes can be made without departing from the scope of the present invention.

[0018]

As described above, according to the medium density pulp bleaching apparatus of the present invention, one batch of the washed pulp stored in the storage tank is delivered and circulated in the reactor portion. Since the reaction can be carried out in several steps, it is possible to freely control various reaction conditions and obtain an excellent effect that pulp of any Kappa number can be obtained. .

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a bleaching apparatus for medium-concentration pulp of the present invention.

FIG. 2 is a schematic diagram showing an example of a conventional bleaching apparatus.

[Explanation of symbols]

 4 Storage Tank 6 1st Reaction Modifier Supply Pipe 7 1st Mixer 9, 10 Transfer Pipe 11 1st Blow Tank 13 Bleach Supply Pipe 14 2nd Reaction Modifier Supply Pipe 15 2nd Mixer 17, 18 Transfer Pipe 19 Reactor 20 Circulation pipe 21 Transfer pipe 22 Second blow tank

Claims (1)

[Claims] 1. A storage tank is provided for storing the medium-concentration pulp after washing and delivering it to one batch, and the storage tank is provided downstream of the storage tank via a transfer pipe.
A mixer, a first blow tank, a second mixer, a reactor and a second blow tank are installed, and a circulation pipe for circulating pulp is connected between the outlet of the reactor and the inlet of the first blow tank. In addition, a first reaction adjusting agent supply pipe for supplying a first reaction adjusting agent to the first mixer is provided, and a bleaching agent supply pipe and a second reaction adjusting agent for supplying a bleaching agent to the second mixer are supplied. A bleaching device for medium-concentration pulp, characterized in that it has a configuration provided with a second reaction modifier supply pipe.