JPS61289192A - Pressure pulp chlorine treatment and introduction of chlorine by minute air bubbles - Google Patents

Abstract

A method and apparatus are provided for increasing the efficiency of treatment of a paper pulp slurry with chlorine gas, such as in the bleaching or delignification of deciduous wood chemical pulps, coniferous wood chemical pulps, and non-wood fibrous chemical pulps. Chlorine gas is intimately mixed with the pulp in a fluidizing mixer (14), the pulp preferably having a consistency of about 7-12%, and then is passed to a retention vessel (20). The discharge of pulp from the mixer to the retention vessel, and from the retention vessel to other treatment structures, is throttled by valves (30, 31) so as to increase the pressure in both the mixer and the retention vessel to above atmospheric, and preferably in the range of about 15-150 psig (1 to 10 bar above atmospheric pressure). The chlorine gas is added to the mixer through one more discs (53) of porous materials having pore sizes in the range of about 5-175 microns, such as porous ceramic or sintered metal discs. The increased pressure during the chlorine treatment, and the introduction of the chlorine gas in the form of minute bubbles, improve the solubility of the chlorine in the pulp slurry and thereby increase the efficiency of treatment. (Figure 1).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for chlorinating a slurry of pulverized fibrous cellulose material.

BACKGROUND AND SUMMARY OF THE INVENTION In typical moderate concentration chlorination equipment, such as chemical valve bleaching or delignification, chlorine is injected through a nozzle into a mixer and then at near atmospheric pressure. Transfer to holding container. While the valve remains in the mixer and holding vessel, the chlorine removes impurities and crusts in the valve slurry (
lignin and tree bark) to effect the desired bleaching or delignification.

The present invention provides a method and apparatus for significantly increasing the efficiency and effectiveness of processing milled cellulose fibrous material slurries with chlorine gas, particularly for bleaching or delignification of chemical valves. According to the invention, the pressure within the mixer and/or holding vessel is approximately 10-15
It has been found that when raised to a range such as 0 psigQ, the solubility of chlorine gas increases. Also, under elevated pressure, chlorine gas tends to take the form of microbubbles and increase the total reaction area, and the combined mN network at this pressure suppresses gas bubble coalescence. Further in accordance with the present invention, the chlorine gas has a pore size of about 5-175 microns. Since it is introduced into the mixer through a disc of porous material, such as a porous ceramic disc or a porous sintered metal disc, the chlorine is in the form of microbubbles from the time of introduction.

The improved solubility of chlorine gas in the valve slurry made by the present invention results in reduced total chemical consumption, use of more chlorine than chlorine dioxide (chlorine dioxide is also added during processing and is more expensive than chlorine gas), and retention. These include reduced slurry volume in the vessel, relatively low kappa handling, less chemical waste, and reduced bleach consumption in subsequent processing.

It has many beneficial effects.

According to the present invention, chlorine gas is intimately mixed with the valve slurry in a fluidizing mixer, and the valve slurry is approximately 2.5-16%
, preferably at a concentration of about 7-12%.

It is then desirable to transfer the slurry through a discharge line to a holding container. In the discharge line from the mixer, a throttle valve is used to throttle the discharge, thereby increasing the pressure within the mixer and maintaining it in the range of about 1 s-150 psig.

A similar throttle valve also reduces the pressure within 15-
Placed at the discharge of the holding vessel to maintain within 150 psig. When introduced into the mixer, chlorine gas is introduced through a disc of porous material so that it takes the form of microbubbles.

A primary object of the present invention is to provide a more effective treatment of milled cellulose fibrous material slurry with chlorine gas. This and other objects of the invention from reading the detailed description of the invention.

It will also become clear from the appended claims.

DETAILED DESCRIPTION The present invention is applicable to a wide variety of methods of treating pulverized cellulose fibrous material slurries with chlorine gas. In particular, the present invention provides deciduous chemical valves, coniferous chemical valves, and chemical valve mixtures.

and in the bleaching of non-wood fiber chemical valves. As a first step in a bleaching feedstock; as a step following an initial delignification using oxygen; as a first step in a delignification process; and in bleaching, delignification, and related processes, etc. .

For purposes of illustration, 1 the method according to the invention will be described for chlorine bleaching of chemical valves with chlorine dioxide;
It is clear that it has wider applicability.

A chemical valve is provided in 9 a conventional bleach feed storage tank 10, into which the valve is introduced through a lambda port 11;
and tank 12 using a conventional fluidizing centrifugal pump 12, such as the type shown in U.S. Pat. No. 4,435,193.
raised from the bottom. The bulb has a concentration of about 2.5-16%, preferably 3.5-13%, most preferably about 1-12%.

The temperature of the valve slurry is typically 50°F = 160°F.
°F, more preferably 80-150"F.

Valve 2 to normal fluidizing centrifugal mixer 14, line 13
The inside is guided by a pump. The mixer 14 is preferably capable of fluidizing the valve even with concentrations up to about 16% in order to effectively mix the added chemical and the valve within the mixer.

The type of mixer 14 taken is shown in Canadian Patent No. 1102604, and such mixers are commercially available (Kaiyr,
Inc, of Glens Falls, Ne
wYork), sold under the trademarks rMcJ.

Chlorine gas from source 15 passes through pneumatic loop 16' into line 16 and is added to mixer 14, as does chlorine dioxide from source 17 through line 18. Typically, the chlorine gas has a temperature in the range of about 75°F-140″F, more typically about 90″F-125°F. The pressure in source 15 and line 16 is typically about 60-
In the range of 125 psiCl.

Normal safety devices, valves, and interlocks are used with chlorine gas systems.

Chlorine dioxide from source 17 is typically 35°F-10
0"F, more commonly 1 degree between 40"F and 55F. Chlorine dioxide is added in liquid form at a concentration of 4-14 gpl, preferably 6-10!1 it) l;
Ru.

The total holding time of the pressurized area (mixer 14 and/or vessel 20) is about 0.01-60 minutes, preferably about 0.1-60 minutes.
It is 20 minutes.

The present invention is particularly directed to the bleaching of deciduous tree chemical bulbs with kappa numbers in the range 10-25 (more generally 15-20).

Kappa number 25-150 (more commonly 28-38)
It is applicable to the bleaching of softwood chemical valves in the range of , the bleaching of chemical valve mixtures, and the bleaching of non-wood fiber chemical valves with a kappa value in the range of 14-150.

From mixer 14, the valve moves to holding vessel 20.

With the diluent added through the introduction structure 21.

There it flows upward. The valve is drained by a scraper at the top of the holding vessel into a drain line 23.

It then passes through a storage line and from there to a preferably pressure diffuser or similar isobaric vessel for subsequent holding or cleaning under pressure.

The pressurization of mixer 14 and/or vessel 20 significantly increases the solubility of chlorine in the valve, thus causing a! I faced the sun roughly. It has been found by the present invention that a more effective reaction with impurities in the outer skin (such as lignin and bark) within IIAN and IIAN is caused. Moreover, the application of pressure favors the generation of microbubbles of chlorine gas.

The network of interlaced fibers, together with the increased pressure, suppresses gas bubble coalescence. The final result is.

Reduced total chemical consumption, reduced degree of replacement of chlorine by chlorine dioxide (chlorine dioxide is more expensive).

Reduced slurry volume in vessel 20, lower extraction kappa number of the valve, less chemical waste, and reduced bleach consumption in subsequent processing.

Pressurization of mixer 14 and container 20 is achieved through discharge from mixer 14 through valve 30. and discharge 23 from tank 20
It is desirable to perform this using the valve 31. valve 30
．． 31 of materials that withstand the corrosive aggressive conditions that exist.
You can choose from a wide range of available throttle valves, such as valves with all wet parts. for example.

Valve 30 can include a 4 inch diameter ball valve;
Valve 31 can include an 8 inch diameter ball valve. Typical throttle pole valves available in this regard are commercially available (WKM of Houston, T
From exas, product name Dyna sea+350)
. Of course, a wide range of other commercially available throttle valves can also be used. Valve 30.31.

The pressure within mixer 14 and/or tank 20 is approximately 15
- 150psiO (preferably about 30-120ps
9 operated either manually or automatically to control the pressure to be within the range of io).

In order to ensure that the chlorine gas takes the form of microbubbles from the moment of introduction, preferably the structure illustrated in Figures 2-5 is used. FIG. 2 shows mixer 14 through line 16.
A source 15 is shown connected to.

The particular connection structure illustrated in FIG. 2 includes a branch connection 40 having branch conduits 41,42 extending therefrom. A filter 44 and one or more valves 45 are disposed in each branch conduit, and each branch conduit terminates in a chlorine gas injection nozzle 47. Two such structures are utilized in case of malfunction (in which case it can be closed and the other available until repairs are made) and for the constant introduction of chlorine gas into the mixer. . The injection nozzle 47 (
(equipped with a reasonable number of nozzles) is connected to the mixer 14 on the opposite side of the mixer's circular cross-section valve inlet portion 5°.

A typical filter 44 is illustrated in FIG.

It includes a solid annular metal body 52 upon which is mounted a circular disk 53 of porous material. Typical porous materials for disk 53 include porous ceramics and sintered metals.

A typical chlorine gas injection nozzle 47 is illustrated in FIGS. 4 and 5 and includes an annular flange 55. and the deepest end of one body 56 (nearest the mixer 14, or

a conical surface 5 formed on the end (extending to the mixer 14);
It includes a metal housing including an annular body 56 with 7. A disk 58 is disposed within the nine body 56 and has a conical surface abutting the nine conical surface 57. The disk 58 is
including means for introducing chlorine gas in the form of microbubbles;
- Includes porous materials with pore sizes in the range of 175 microns.

Typical porous materials that can be used to form disk 50 include commonly available 5. Porous ceramics and porous sintered metals.

The disk 58 is fitted with a gasket 59. It is held in place against the two conical surfaces 57 by a retaining ring 60° and a retaining clip 61. Clip 61.

Body 56 and ring 60 engage to hold them in the position shown in FIG. 4 with one ring 60 pressing against gasket 59 and disc 58.

Retaining ring 60 may be threaded to mate with body portion 56 (which is internally threaded).

It will thus be seen that in accordance with the present invention, a method and apparatus have been provided that enhance the efficiency and effectiveness of the treatment of pulverized cellulose I fibrous material slurry with chlorine gas. The invention is herein presented in what is believed to be a practical and preferred embodiment of the present invention.

And, although described, many modifications may be made within the scope of the invention, which scope is subject to the broadest interpretation of the appended claims to encompass all equivalent methods and apparatus. This will be clear to those skilled in the art.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an exemplary apparatus according to the present invention for bleaching chemical valves according to the present invention. FIG. 2 is a detailed end view of the front of the mixer of the apparatus of FIG. 1, showing the interconnections of the mixer to the chlorine gas and chlorine dioxide liquid sources. 3 is a side cross-sectional view of the structure 44 of FIG. 2. FIG. FIG. 4 is a side sectional view of the introduction nozzle 47 of FIG. 2. Figure 5 is. FIG. 5 is an end view of the nozzle of FIG. 4; In the figure, 10 is a bleach feed material storage tank, 12 is a pump,
14 is a fluidizing centrifugal mixer, and 15 is a chlorine source. 16 is a line, 17 is a chlorine dioxide source, 20 is a holding container,
23 is the discharge line, 30.31 is the throttle valve, 4
4 is a filter, 47 is a chlorine gas injection nozzle, and 53 is a disk.

Claims (10)

[Claims] (1) A method of treating a slurry of ground fibrous cellulosic material with a chlorine gas comprising: (a) intimately mixing chlorine gas with the slurry; and (b) feeding the slurry into a holding vessel (20). (c) maintaining a pressure within the holding vessel between about 15 psig and 150 psig to increase the solubility of chlorine gas in the slurry, thereby increasing the efficiency and/or efficacy of the chlorination. A method characterized by: 2. The method of claim 1, further comprising the step of: (2) step (a) being performed in a mixer 14 and maintaining the pressure within the mixer between about 15 psig and 150 psig. 3. The method of claim 2, further characterized in that: (3) the slurry is held at a pressure between about 15-150 psig for a time within the range of about 0.01-60 minutes. . 4. The method of claim 2, further characterized in that the concentration of the slurry is in the range of about 7-12% during the performance of steps (a)-(c). . (5) chlorine gas by passing it through a porous disk (53) having a pore size in the range of about 5-175 microns to improve the solubility in the slurry and thereby increase the efficiency of the process; 2. A method according to claim 1, further comprising introducing into the mixture in the form of microbubbles. (6) During the performance of steps (a) to (c), the slurry is
having a concentration between about 2.5-16%, steps (a)-(c)
6. The method of claim 5, further characterized in that a pressure of about 30-120 psig is maintained during the performance. (7) The discharge of slurry from the holding container is controlled by the first throttle valve (30), and the discharge of slurry from the mixer is controlled by the second throttle valve (31). 3. The method of claim 2, further comprising maintaining the pressure. (8) a fluidization mixer (14) for intimately mixing chlorine gas with the slurry and a discharge line extending therefrom, the mixer including at least one chlorine gas introduction nozzle (47); In a slurry chlorine gas treatment device; a first throttle valve (30) arranged in the discharge line to throttle the slurry discharged from the mixer and thereby control the pressure in the mixer;
on the opposite side of the first throttle valve from the mixer, the holding vessel (20
), the holding vessel includes an inlet line and a holding vessel discharge line that connects with the mixer discharge line (23);
and a second throttle valve located in the holding vessel discharge line for controlling the pressure within the holding vessel (
31) A device for treating slurry with chlorine gas. (9) The above-mentioned at least one chlorine gas introduction nozzle,
a disk (53) of porous material disposed in the nozzle through which chlorine gas passes to the mixer, the material having a pore size in the range of about 5-175 microns; 9. The device of claim 8, further comprising means for introducing microbubbles into the air. (10) the at least one chlorine gas introduction nozzle includes a pair of chlorine gas introduction nozzles (47) arranged substantially opposite each other in functional association with the mixer;
The nozzle is connected to a common line containing chlorine gas under pressure (
16) through branch conduits (41, 42), each of said chlorine gas introduction nozzles containing a disk of a first porous material; 10. The device according to claim 9, further characterized in that it includes a second disk of porous material serving as a filtering means (44) for filtering particles from the flow of.