AU613952B2

AU613952B2 – Method of bleaching or delignification of cellulose pulp with oxygen
– Google Patents

AU613952B2 – Method of bleaching or delignification of cellulose pulp with oxygen
– Google Patents
Method of bleaching or delignification of cellulose pulp with oxygen

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Publication number
AU613952B2

AU613952B2
AU22021/88A
AU2202188A
AU613952B2
AU 613952 B2
AU613952 B2
AU 613952B2
AU 22021/88 A
AU22021/88 A
AU 22021/88A
AU 2202188 A
AU2202188 A
AU 2202188A
AU 613952 B2
AU613952 B2
AU 613952B2
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AU
Australia
Prior art keywords
slurry
oxygen
steam
pulp
temperature
Prior art date
1987-06-08
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Ceased

Application number
AU22021/88A
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AU2202188A
(en

Inventor
Jack A. Davidson
Derek Hornsey
Robert Lee
Arthur S. Perkins
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Canadian Liquid Air Ltd

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Canadian Liquid Air Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1987-06-08
Filing date
1988-09-08
Publication date
1991-08-15

1988-09-08
Application filed by Canadian Liquid Air Ltd
filed
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Canadian Liquid Air Ltd

1990-06-28
Publication of AU2202188A
publication
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patent/AU2202188A/en

1991-08-15
Application granted
granted
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1991-08-15
Publication of AU613952B2
publication
Critical
patent/AU613952B2/en

2008-09-08
Anticipated expiration
legal-status
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Status
Ceased
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Classifications

D—TEXTILES; PAPER

D21—PAPER-MAKING; PRODUCTION OF CELLULOSE

D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR

D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere

D21C9/10—Bleaching ; Apparatus therefor

D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications

Description

I*
AUSTRALIA
Patents Act COCPLETE SPECIFICATICN (ORIGINAL) 6 19 Class t. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority o o .o 0 0000 o o 0 0 0 0 o t o 0 6 a ao oo o0 o a0 0 00 0 00 0 0 Related Art: APPLICANT’S PRFER~CE: S.2938/JV/MLP Name(s) of Applicant(s): Canadian Liquid Air Ltd Air Liquide Canada Ltee Address(es) of Applicant(s): 1155 rue Sherbrooke Ouest, Montreal,
CANADA.
Address for Service is: PHILLIPS OE=IODE FITZPA’TPCK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Complete Specification for the invention entitled: IETX)O OF BLEACHRIG OR DELIGNIFICATICN OF CELLU .SE PULP WITH OXYGEN Our Ref 105817 POF Code: 1290/57304 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): 6003q/1 1 la- BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to bleaching or delignification of cellulose pulp.
2. Description of the Prior Art Perkins and Davidson, filed April 18, 1986 contains a bibliography on the use of oxygen in bleaching cellulose pulp slurry.
The disclosure of prior application and bibliography are hereby 1 0 incorporated by reference.
S°The Lee et al application discloses a process and o01O apparatus for bleaching pulp in the form of an aqueous slurry having a consistency from 8% to 16%, by introducing oxygen into a 00the slurry, in the form of minute bubbles, at the time the 15 slurry is passing, under pumping pressure, through a diffusing 00 00and mixing conduit which confines the slurry to a cross section a oo 0 00 so that, at the pumping pressure, it moves at a high velocity oo0000 o° effective to provide turbulent liquid flow. The phenomenon of the liquid behavior of pulp slurry confined under high velocity 20 is explained in an article entitled «Medium Consistency 0 00 Technology» appearing in the TAPPI Journal, Vol. 64, No. 6, June 1981, and in the Lee et al Application 507,000, the disclosures of which are hereby incorporated by reference.
The slurry containing the bubbles is immediately passed from the mixing conduit into and through a reaction vessel which releases the slurry to a cross section at which it assumes relatively slow plug flow, to give the oxygen L. l/ -2bubbles dispersed through it, time to react with the cellulose.
The treated slurry is recovered from the reaction vessel. Dispersing the bubbles within the turbulent liquid slurry is accomplished by passing the oxygen, under pressure greater than that of the slurry pressure, through a microporous wall into contact with the slurry.
The slurry may be preheated by passing it through a steam mixer, on the way to the pump, and the heated slurry deposited in a storage vessel upstream of the pump.
1. 0 The minuteness of the bubbles, produced initially by
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0 o diffusing the oxygen into the slurry through the porous wall, 0000 favours good dispersion throughout the mass of the pulp and consequently good bleaching or delignification contact with 0 00 0 00 the pulp fibers.
SUMMARY OF THE INVENTION It is an aim of the present invention to improve contact between the oxygen and the pulp still further so as to 0 achieve enhanced bleaching action with the same amount of oxygen.
This is accomplished, according to the invention, by injecting the oxygen into the diffusing and mixing conduit in the way described above, but as a mixture of oxygen and steam.
Minute bubbles of the oxygen-steam mixture are formed momentarily as the mixture passes from the minute pores of the injector wall, but as each bubble meets the pulp, the steam condenses and leaves the oxygen content as a smaller bubble.
The condensing steam imparts additional heat to the slurry.
1 it 3- Preferably as much of the steam needed to bring the slurry to reaction temperature as possible is injected, in one stage, through the diffuser-mixer. Whether this can be done depends on capacity of the diffuser-mixer. Therefore, additional steam may be injected, if required, in a steam mixer bringing it to a supply temperature in a preliminary stage, through an injector between the pump and the oxygen-steam diffuser-mixer to raise the temperature closer to reaction.
Steam may also be injected to preheat the slurry upstream of 1 0 the pump.
ov a o So, the invention contemplates: Jo o O a) preferably injecting all the steam, in the o diffuser-miser, in the form of an oxygen- O 00 steam mixture, or 5) injecting some of the steam between the pump and the diffuser-mixer to raise the pump to 0 0 0 an intermediate temperature, and c) in combination with either a) or b) injecting steam to preheat the pulp upstream of the S0 20 pump, to preheated supply temperature.
By injecting the oxygen into the liquid-behaving slurry, in an oxygen-steam mixture, as compared with injecting oxygen alone through the same microporous surface, under the same conditions, the effective surface area of the oxygen, in contact with the pulp, may be increased from twice to ten times, with a preferred increase from three to five times. This bring about a corresponding increase in the bleaching effect of the 12 t!_ of the oxygen and a consequent saving of chemical bleaching agent. Heating the slurry with the injected steam, at this stage, is also advantageous.
For bleaching, the proportion of oxygen to steam may range from 20 to 200:1, by weight, with 100 to 150:1 preferred.
Or, in terms of volume, the proportion of oxygen to steam may range from 50 to 500:1 with 300 to 400:1 preferred. For delignification, the oxygen may range from 80 to 800:1, by weight, with 400 to 600:1 preferred. Or, by volume, the oxygen may range from 200 to 2000:1, with 1200 to 1600:1 preo ferred.
The oxygen to pulp ratio may range from 10 Ibs. to 0 Ibs. per ton of pulp, measured on a dry basis. Then it is desirable to add as much steam as possible with the oxygen- 15 steam mixture. Since the amount of steam which can be added 0 ‘O is limited by the capacity of the diffuser, it may be necessary as well to add steam at an earlier stage, in order to inject n 9 0 S° enough heat to bring the slurry to reaction temperature.
The invention provides for potential maximum utiliza- °O 20 tion of oxygen and steam in the delignification or bleaching process in the following way. The total amount of steam, injected into the slurry, is a controlled amount that will heat the slurry to reaction temperature in the reaction vessel. Preferably, according to the invention, the proportion of the total amount of steam injected with the oxygensteam mixture in the diffuser would be substantially the maximum allowed by the capacity of the diffuser to inject it I w i i
I
‘i 0 0 0p 0 P 00 o OP 0 PP o 006 pp~ 0 P P 0 00 *o 0 0 P p’,P0 0 00 p 00 or a proportional selected amount close -to this maximum, say or more. The remainder of the steam necessary to heat the slurry to reaction temperature may then be injected into it upstream of the diffuser. The optimum proportion of oxygen to’be injected into the pulp for good delignification or bleaching is determined by tests, as is well known in the art, and selected for the particular plant and the particular conditions involved.
Oxygen fnjection is then controlled to feed the selected amount continually to the slurry. The injection of steam, along with the oxygen, results in the oxygen being injected in smaller bubbles than if oxygen alone were being injected which, in turn, provides a greater surface area of the oxygen in contact with the pulp and better absorption for a given amount of oxygen.
15 The invention, therefore, provides several advantages, namely that a large amount of steam used for heating is injected where it is needed just prior to the reaction zone and, at the same time, the injection of the oxygen along with the steam results in greater surface area of the oxygen injected and better reaction with the pulp for a given amount of oxygen. In this way, the utilization of both oxygen and steam is substantially at a maximum for the particular plant.
If all the steam needed to bring the slurry to reaction temperature can be added at the diffuser control may be exerted continuously by regulating the amount of steam fed in the steam-oxygen mixture by the temperature of the slurry downstream of the oxygen-steam diffuser while keeping the supply of oxygen constant or by controlling it in keeping with some .i -6 relevant variable. If it is necessary to add additional steam upstream of the diffuser the temperature control will also regulate such upstream supply.
The invention lends itself particularly to the incremental dosage of the pulp slurry with oxygen. This is done by feeding of a stream of cellulose pulp slurry under pressure.
from a supply, through a reaction path made up of a plurality of successive stages, in each of which the stream is first confined to a cross-section at which it has a velocity such as to fluidize 10 it to liquid flow and is then expanded to a cross-section at which it has a velocity such as to provide plug flow. In each stage, 0009 gp oxygen is injected into the liquid flow under pressure, in the form of a mass of minute bubbles to disperse them throughout, whereby most of the oxygen is reacted with the pulp in the plug flow at that stage. The treated slurry is then recovered from :0 the final stage.
The invention also contemplates a preferred further mixing of the slurry leaving the oxygen diffuser by passage through a pulp fluidizing mixer. This can be located adjacent C’0 o 20 to the diffuser or positioned some distance downstream. This mixer provides the effective further mixing and dispersing of any agglomeration of oxygen so that the oxygen remains in finely divided form and is more intemately mixed with the slurry. A preferred static mixer is made up of a pipe tapering down to a choke, followed by a pipe that flares out to the diameter of the pipe in which the pulp slurry is flowing. The velocity through the choke will be about the same as that in the diffuser.
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-7 0’00000 00 0 0 0 rl0 0 0 0000U 00 0 0 00~ 00 0 0 0 J 0Q 00 0 01 00 0 00 0 00 00 0L 4, 4., The invention also contemplates means for coordinating the flow of oxygen to the flow of pulp slurry so as to maintain the proper oxygen dosage. This may be accomplished by an apparatus which includes a flow measuring device, for example, an orifice plate within the path of the slurry, in advance of the diffuser, the orifice plate being connected to a differential pressure cell which, in turn, is connected to a controller.
The controller sends a signal to an oxygen flow control valve controlling the oxygen supply to the diffuser. There 10 is an orifice plate or other device in the oxygen supply line that measures the oxygen flow. The control mechanism may include a computer that maintains a constant, predetermined and set ratio of oxygen to pulp so as to increase and decrease the dosage to keep pace with the differing flow rates of the pulp slurry.
15 An apparatus, according to the invention, includes a supply vessel for the slurry, a substantially unobstructed injection and mixing conduit for confining the slurry to a stream for substantially free flow therethrough, a reaction vessel having a greater cross-section than said conduit and 20 connected therewith, means for continuously force-feeding the slurry under pressure from the supply vessel to the conduit, and means for regulating the feeding pressure so that the slurry in the conduit has a velocity such as to provide a turbulent liquid flow therethrough and the slurry in the reactor assumes plug flow. There is diffusing means, including an extensive microporous surface interfacing with the slurry, in the conduit, to diffuse an oxygen-steam mixture into the iii L I:i .1 -8 slurry’under pressure higher than the pulp feeding pressure thereby to form a mass of minute oxygen bubbles and mix them throughout the slurry in the conduit whereby they remain in contact with the thick pulp throughout the plug flow to provide delignification or bleaching action. The control mechanism includes a supply conduit for supplying a mixture of oxygen and steam to the diffusing means and means for regulating the flow of oxygen therethrough, a steam conduit leading from a source of steam to said supply conduit and means for regulating 10 the flow of steam therethrough, the means for controlling the steam supply being responsive to the temperature of the slurry oooo passing from the mixing conduit to the reaction vessel.
0R 0 Means may also be provided for adding steam to the 0.
0 00 slurry prior to the diffusing means. In this event, the means for controlling the steam supply responsive to the temperature of the slurry may also control the additional supply of steam.
In a preferred apparatus, the pulp slurry flows through o an initial oxygen diffuser and a plurality of reactors each preceded by an oxygen diffuser. Any or all may be passed into a 00 20 reaction tower to allow further extraction with caustic soda.
BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further explained by reference to the accompanying drawings, in which: FIG. 1 is a side elevation partly in section through apoaratus of the type currently used for steam and oxygen addition to pulp in a bleaching process; 9- FIG. 2 is a similar side elevation partly in section through a preferred apparatus effective for carrying out a preferred method, according to the invention; and FIG. 3 is a side elevation, partly in section through a preferred diffusing device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 illustrates a prior method of employing steam and oxygen together in bleaching pulp.
1 I0 Referring to Fig. 1, a pulp mixture, which is normally Ca thick heavy mass, is continuously passed from a source of an supply through a steam mixer 15 which preheats it to a temperature from 1000 to 150’F to 170′ to 200OF and thence through a C pipe 16 to the top of a storage chute 17. From the storage chute 17 the pulp, mixed with steam, is pumped, as a slurry, Cby a pump 19, through another pipe 21 through an oxygen disperser conduit 23 illustrated in more detail in Fig. 3. The CO C pressure at which the slurry is pumped is effective to cause it to flow through the conduit 23 at a velocity such that it acts CoC 20 as a turbulent liquid. This phenomenon is described in the Lee et al application 507,000, referred to above. Steam is supplied to the steam mixer 15 from a source of supply through a pipe The supply of steam is regulated by a temperature controller 27 connected to a valve 29 in the pipe Oxygen is supplied to a diffusing device within the conduit 23, through a line 31 leading from a source of oxygen supply through a p’ressure controller 33. The diffusing device L i0 has a microporous wall interfacing with the slurry.
Oxygen is thus continuously introduced into the heated pulp slurry through the diffusing device in the form of a mass of minute bubbles at a time when it acts as a turbulent liquid, so that the oxygen bubbles are diffused into the slurry and mixed throughout. The slurry containing the oxygen passes through a pipe 35 into the bottom of a retention tube 37 provided with a back pressure control valve 39. The slurry slows down in the tube 37 to plug flow velocity at which it reassumes o 10 its normal thick condition and is held under pressure so that it o gradually absorbs the oxygen which reacts with it.
The, pulp is retained in the retention tube for suffi- 0′ ciently long to allow the oxygen to react with the cellulose.
0 The parts of the preferred apparatus of Fig. 2 have been given the same tens and digits as in Fig. 1 but have been raised by 100.
Method of the Invention v o In the apparatus of Fig. 2, illustrating a preferred method, according to the invention, steam is added to the pipe S o 20 131 conducting the oxygen to the diffusing device A (see Fig. 3) within the disperser conduit 123 to form an oxygen-steam mixture.
The steam supply is controlled by a temperature controller 127 linked to the pipe 135 between the disperser 123 and the retention tube 137. Thus, steam is first mixed with oxygen and the oxygen-steam mixture added to the slurry, through the diffusing device A, in the form of a mass of minute bubbles. When the oxygen-steam mixture contacts the pulp, the 11 steam condenses to water vapor, imparting heat to the pulp, and leaving the oxygen-gas within the pulp in the form of smaller bubbles (than the oxygen-steam bubbles) which are dispersed through the slurry by its turbulence. Better sub-division and dispersion of the oxygen is achieved to provide a much greater effective surface area of the oxygen interfacing with the slurry than would occur without the steam. This increases the oxygen transfer rate accordingly and less oxygen need be employed, than otherwise, to obtain the same bleaching effect.
The pressure of the oxygen-steam mixture, as injected, o°°o is about the same or slightly higher than the oxygen pressure as oooo in the method of Fig. i.
o oIn cr,trast to the prior method, steam is mixed with 0 the oxygen just before injection of the mixture i.nto the diffuser A and the control of the steam flow is carried out by S0a temperature controller 127 sensing the temperature of the 0 0 0 00 0 pulp downstream of the disperser.
Q990 0 0The pulp then passes into the pressurized retention tube 137 where it assumes plug flow and moves at relatively 009 20 slow speed, under pressure, with the oxygen dispersed throughout the plug in small bubbles to react with the cellulose.
In the case where several diffusers are used in series, as for example in the Lee et al Canadian Application 507,000, steam is added to the first stage.
The diffuser through which the oxygen-steam mixture is injected into the slurry in the diffuser A may take various forms, some of which are shown in-the Lee et al application 0 Li~~i&r i’ 0000a4 4n 0 o co o t’ &00o 00 0 o e 0 0 40C O0 0 01 04 4U O ti 44 12 referred to above all of which include a microporous wall which interfaces with the slurry and through which the oxygen-steam mixture is diffused. This is preferably a sintered stainless steel element as described in Bulletin M 201 of Pall Trinity Micro Corporation, a subsidiary of Pall Corporation and in U.S.
Paent 2,554,343. Such elements are generally used for filtering.
The pore size should be within the range from about 2 microns to 100 microns, preferably less than about 10 microns. The porosity should be substantially uniform with voids making up 10 about 40 to 50% of the volume of the wall, which has a thickness of from about 1/32 of an inch to about 1/2 inch.
A preferred form of diffuser A is shown in Fig. 3. It is made up of a cylinder 123 providing a passage for the pulp slurry. The cylinder has flanges 63, 64 on its ends for connecting into a pipeline. A tube 65 extends transaxially and centrally across the passage 123 and is held in it by a suitable socket 69 formed on the wall of the cylinder 123. The pipe 131 for the delivery of the oxygen-steam mixture to the tube 65 leads to the diffusion tube 20 The minute streams of oxygen-steam mixture, as the mixture passes through the pores in the tube 65 wall, as they leave the porour surface, are stripped therefrom by the slurry as minute bubbles. The steam condenses from each bubble, immediately it contacts the slurry and leaves a bubbles of oxygen, having a fraction of the size it would have had oxygen alone been injected. While there may be some coalescence, generally speaking, the mass of oxygen bubbles are dispersed I i i j i;.a ;i: j.- 111 s.
i :r d -13throughout the slurry by its turbulence as it passes with great rapidity through the conduit 123 and the bubbles are carried in the slurry into the reaction chamber 137 where it assumes relative slow plug flow. The oxygen therefore has time to react with the pulp and is absorbed as the plug of slurry passes relatively slowly through the vessel 137..
The Diffuser The diffusing element may include a conduit or cylinder through which the slurry passes, the wall of the cylinder 10 defining the flow path. The diffusing element may form a part o 8 of the wall of the cylinder, may take the form of a porous pipe %oo extending transaxially of the cylinder, or may take the form of °o a porous pipe extending axially of the cylinder. In all cases, o 0 4 the path of the slurry is relatively unobstructed. Where the cylinder has a porous wall, the slurry passes directly through 0°4 the cylinder without any obstruction. In the case of a pipe °8 within the cylinder, it takes up a minor space so that the major volume of the space in the cylinder is taken up by the slurry moving through it in contact with the porous diffusing 20 surface.
Starting Material The starting material for the present process will depend on whether the method is being employed at the delignification stage or the bleaching stage of the pulp treatment.
For delignification, the aqueous pulp slurry comes from three or four washing stages following the brownstock washing stage, with the pulp containing considerable lignin, IJ* *I i i .i4.- 14 as indicated by a Kappa number between 30 and 60, typically to 50. It will contain 8 to 16%, preferably 10 to 12%, by weight, solids. Caustic will be added in an amount from 2 to by weight, typically prior to delignification according to the present invention.
Bleaching is effected, according to the invention, usually after the slurry has been washed, following the first chlorination stage. Then, it will have a Kappa number from 3 to 8, typically 4 to 5. It will contain from 8 to 16%, preferably 10 to 12%, by weight, solids. Again, caustic will be added in an amount of 2 to by weight, typically to provide the 00 starting material for bleaching, according to the invention.
Q
o0 Turbulent Liquid Flow A typical diffusing and mixing conduit 123 may range oooo 15 in cross-sectional area from about 4 to about 17 sq. inches.
o0Oo0 To produce turbulent flow, the slurry is fed through the conduit at a pressure from about 20 to about 200 psig. This gives the o0o0 slurry a velocity from about 0.5 to about 50 meters per second, preferably from about 3 to about 10 meters per second.
0 00 0oo 20 The residence time in the conduit 123 will then range from about 0.001 to about 0.120 seconds. The residence time in the reactor tube 137 will range from about 1 to about 5 minutes.
Temperature Steam serves both the function of heating the slurry and as a vehicle for the injection of the oxygen so as to reduce the size of the bubbles of the latter mixed into the slurry.i Typical preferred temperatures are: i i aa) the starting pulp slurry prior to the mixer will usually have a temperature below around 130°F, b) in the mixer 15 the temperature will be raised from 130’F to about 140°F, c) after the preliminary injection downstream of the pump and prior to the oxygen-steam diffuser mixer to an intermediate temperature between 140’F and 160’F, d) after the diffuser mixer to a reaction temperao 0 o 10 ture in the range from about 160’F to 180F, e) before entry into the retention vessel the pulp 0o should have a temperature within a range from a 0V o about 160F to about 180’F.
0 00 Porous Surface 00 15 The surface of the porous wall interfacing with the 0oo0o °0000slurry may preferably have an area ranging from about 0.05 to 0oo about 0.2 sq. feet covered with pores having a diameter within oo .o~ the range from about 10 to about 100 microns.
0 Oxygen-Steam The oxygen employed may be molecular oxygen, as commercially available, containing 90% or more and preferably 98% or more of oxygen. Or, the oxygen can be in the form of a gas containing more than 50% oxygen. The starting pulp slurry may contain about 10 to about 20% of air by volume of the pulp dispersed which dilutes added oxygen. For a pulp containing little or no air, the concentration of the added oxygen containing gas may be I at the lower end of the oxygen content range aiid for a pulp 16 containing a lot of air, the added gas may contain oxygen toward the upper end of the oxygen range.
In order to control the oxygen dosage to meet requirements, the oxygen content of off-gas leaving the vent of the final treatment vessel is measured. From this it can be determined whether good mixing is being achieved. Adjustments can be made accordingly and the incremental dosage can be manipulated in order to achieve the best results.
In a multi-stage process, as described, large total 000000 amounts of oxygen can thus be added incrementally to a pulp 00 0, slurry, by adding small amounts at each stage according to the .VI 0formula: o9 0 Volume of oxygen gas 0< 00 Volume ('oxygen gas pulp steam) 0. This formula is calculated at the operating pressure of 0 00 0 15 that particular stage. 0 The dosage may be proportioned evenly to each stage or 0 o may be varied to suit varying'conditions such as changes in the nature of the pulp or otherwise. 0 0 The oxygen employed should have at least 90% oxygen content by volume, preferably more than 98% measured under standard conditions. The steam should be saturated steam. The oxygen-steam mixture injection pressure should be greater than the pulp slurry pressure from about 15 to 150 psig. The temperature of the oxygen-steam mixture, at injection, should be from about 265 0 F to about 390 0 F. 17 The rate of injection of the oxygen-steam mixture should be within the range from about 10 lbs. of oxygen to about Ibs. of oxygen per ton of pulp measured on a dry basis. As will be understood by one skilled in the art, the vessels and piping should be insulated so as to retain heat. 00..o 0 0 0 o o a o o 0 04 0 0 o 0 0 O0 a 04 0960 0 00 0 0 0 0 00 0 1 Claims (10) 7.. THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 0 0 o 0 00 0 o o0 0 000 0 00 a 0 0 0 oo 09 ow e 0 00 a oo S6 0 00 0 1. A continuous method of bleaching or delignification of cellulose pulp, in which the pulp, in the form of an aqueous stream of slurry, is passed under pressure from a source of supply by pumping means through a diffusing and mixing conduit at a velocity such that it behaves as a turbulent liquid and then through a reaction vessel under pressure at a velocity at which it assumes plug flow, and oxygen is injected, at a pres- sure higher than that of the slurry, into the slurry in the o conduit, through a microporous wall, in the form of minute bubbles which are dispersed throughout the slurry in which, the oxygen is injected to the stream, through said microporous wall, in an oxygen-steam mixture whereby the steam condenses in and heats the slurry leaving the oxygen as smaller tosn +ke bubbles whereby the effective surface area of the oxygen in contact with the slurry is substantially greater than the sur- face area resulting from injecting oxygen alone into the slurry under the same conditions. 2. A method, as defined in claim 1, in which the injection Io of the steam is effective to raise the temperature of the slurry to at least 160 0 F. 4 4 0404 4 4t 44 4. 0 4 4 4 44: 3. A method, as defined in claim 1, in which the steam is also mixed into the pulp, in a preliminary stage, between the pumping means and the oxygen-steam diffuser, to raise the temperature of the pulp from preheated supply temperature to an intermediate temperature below reaction temperature. /o r.ci*3R' /uZ I zi i4/ U- i%: 4 4 4i 4thr 4 ril. r4 V I 44 4 44 4P 4 4 4 4 4 -19- 4. A method, as defined in claim 1, in which steam is mixed into the pulp, upstream of the pumping means, to bring it to a preheated supply temperature. A method, as defined in claim 1, in which the oxygen- steam mixture is prepared by moving at least a major proportion of the steam employed to heat the slurry to the oxygen just prior to injection into the slurry and continuously regulating the amount of steam mixed with the oxygen in response to the temperature of the slurry. lo 6. A method, as defined in claim 1, in which there is injected into the slurry a total amount of steam effective to heat the pulp to reaction temperature, the steam supplied in the oxygen-steam mixture is adjusted to at least .80% of the maximum steam handling capacity of the diffuser and-the remainder of the steam is supplied up- stream of the diffuser. 7. A method, as defined in claim 6, in which the oxygei is injected within the range from abut--10 to abut 50 Ibs. per ton of pulp on a dry basis. 0o 8. A continuous method, as defined in claim 1 or 6, in whiclh the proportion of steam to oxygen in the mixture is with- in the range from a-beu-t-5-O volumes of steam to 1 volume of oxygen to a-bout 400 volumes of steam to 1 volume of oxygen. 4 '5 ti 5 V 9. A method, as defined in claim 1 or 6, in which the pore size of the microporous wall is not greater than 100 microns. A method, as defined in claim 1 to 6, in which the slurry stream is pumped at a pressure within the range from t to about-.L&t Jig through a conduit having a cross- section area within the range from-abet ~4 to aet- 17 sq. inches. 11. A method, as defined in claim 1 or 6, in which the 0 o0, g oxygen-steam mixture is injected at a higher pressure than i o0o° 1 0 o that of the slurry, within the range from j3 to 2zo psig. 12. .A method, as defined in claim 6, in which the reaction temperature of the slurry is regulated by controlling the amount of steam supplied in the oxygen steam mixture in response to the 0 04 0o,* temperature of the slurry downstream of the introduction of the oxygen-steam mixture. 13. A method, as defined in claim 2, in which steam is 0. 0 mixed into the pulp, upstream of the pumping means, to bring the pulp to a preheated supply temperature. 14. A method, as defined in claim 1, in which the reaction ao temperature is within the range from 160 0 F to 180 0 F. 44 v r I I." -21- An apparatus for reacting an oxygen-containing gas with a cellulose pulp slurry having a consistency from 8% to 16% and being, at rest, a thick aqueous dispersion of pulp fibers, to effect delignification or bleaching, comprising, a supply vessel for the slurry, a substantially unobstructed injection and mixing conduit for containing the slurry to a stream for substantially free flow therethrough, a reaction vessel having a greater cross-section than Q o said conduit and connected therewith, no°° means for continuously force-feeding the slurry under a 0a o ao pressure from the supply vessel to the conduit, o means for regulating the feeding pressure so that the slurry in the conduit has a velocity such as to provide a turbulent liquid flow therethrough and the slurry in the reaction 00y assumes plug flow, o '0o diffusing means including an extensive microporous surface interfacing with the slurry in the conduit to diffuse O oxygen-containing gas into the slurry under pressure higher S than the pulp feeding pressure thereby to form a mass of minute bubbles and mix them throughout the slurry in the con- duit whereby they remain in contact with the thick pulp throughout the plug flow to provide delignification or bleaching action, a gas connection to the diffusing means, means for supplying oxygen to the gas connection, i 'i -22- means for supplying steam to the gas connection, means for controlling the oxygen supply, means for controlling the steam supply, and means for recovering treated slurry from the reactor. 16. An apparatus, as defined in claim 15, in which the means for controlling the steam supply is responsive to the temperature of the slurry leaving said.mixing conduit. 17. An apparatus, as defined in claim 15, in which there j is means for injecting steam into the slurry between the pump *C to and said mixing conduit. 0 0 oo 0 18. An apparatus, as defined in claim 15, in which there is a steam mixer for mixing the slurry with steam upstream of o o the pump. 0 10 19. A method as defined in claim 1, substantially as e hereinbefore described with reference to the example,. 20. An apparatus, as defined in claim 15, subEtantially as hereinbefore described with reference to the acco'ipanying drawings. DATED; 8 September 1988 PHILLIPS ORMONDE FITZPATRICK 9-o Attorneys for: CANADIAN LIQUID AIR LTD. AIR LIQUIDE CANADA LTEE *i C i AU22021/88A 1987-06-08 1988-09-08 Method of bleaching or delignification of cellulose pulp with oxygen Ceased AU613952B2 (en) Applications Claiming Priority (1) Application Number Priority Date Filing Date Title CA 539056 CA1300322C (en) 1987-06-08 1987-06-08 Method of bleaching or delignification of cellulose pulp with oxygen Publications (2) Publication Number Publication Date AU2202188A AU2202188A (en) 1990-06-28 AU613952B2 true AU613952B2 (en) 1991-08-15 Family ID=4135839 Family Applications (1) Application Number Title Priority Date Filing Date AU22021/88A Ceased AU613952B2 (en) 1987-06-08 1988-09-08 Method of bleaching or delignification of cellulose pulp with oxygen Country Status (5) Country Link EP (1) EP0295180A3 (en) JP (1) JPH0299681A (en) AU (1) AU613952B2 (en) CA (1) CA1300322C (en) FR (1) FR2617877B1 (en) Families Citing this family (5) * Cited by examiner, † Cited by third party Publication number Priority date Publication date Assignee Title CA2046717A1 (en) * 1991-02-06 1992-08-07 Beloit Technologies, Inc. Method and apparatus for treating fibrous materials with a gaseous reagent SE469398B (en) * 1991-11-06 1993-06-28 Sunds Defibrator Ind Ab HEATING DEVICE FOR EXAMPLE OF CELLULOSAMASSA THEREOF APPLIED BY A MULTIPLE, SCRUBLED LOCATION, TAKEN IN A TRANSMISSION WALL US5690786A (en) * 1991-11-26 1997-11-25 Air Products And Chemicals Inc. Process for the treatment of pulp with oxygen and steam using ejectors US5372679A (en) * 1992-06-08 1994-12-13 Air Products And Chemicals, Inc. Reactor system for treating cellulosic pulp at a constant upward flow velocity EP0647466A3 (en) * 1993-10-08 1996-01-17 Akzo Nobel Nv Cellulosic membranes. Citations (2) * Cited by examiner, † Cited by third party Publication number Priority date Publication date Assignee Title EP0106460A1 (en) * 1982-09-30 1984-04-25 The Black Clawson Company Improved method and apparatus for oxygen delignification AU595842B2 (en) * 1985-11-15 1990-04-12 Canadian Liquid Air Ltd. Pulp bleaching Family Cites Families (1) * Cited by examiner, † Cited by third party Publication number Priority date Publication date Assignee Title US4177105A (en) * 1973-05-22 1979-12-04 Kamyr, Incorporated Apparatus for delignifying and bleaching cellulose pulp 1987 1987-06-08 CA CA 539056 patent/CA1300322C/en not_active Expired - Fee Related 1987-07-08 FR FR8709702A patent/FR2617877B1/en not_active Expired - Fee Related 1988 1988-06-08 EP EP88401393A patent/EP0295180A3/en not_active Withdrawn 1988-09-08 AU AU22021/88A patent/AU613952B2/en not_active Ceased 1988-09-29 JP JP24587888A patent/JPH0299681A/en active Pending Patent Citations (2) * Cited by examiner, † Cited by third party Publication number Priority date Publication date Assignee Title EP0106460A1 (en) * 1982-09-30 1984-04-25 The Black Clawson Company Improved method and apparatus for oxygen delignification AU595842B2 (en) * 1985-11-15 1990-04-12 Canadian Liquid Air Ltd. Pulp bleaching Also Published As Publication number Publication date AU2202188A (en) 1990-06-28 FR2617877A1 (en) 1989-01-13 JPH0299681A (en) 1990-04-11 EP0295180A2 (en) 1988-12-14 CA1300322C (en) 1992-05-12 FR2617877B1 (en) 1995-01-06 EP0295180A3 (en) 1989-10-11 Similar Documents Publication Publication Date Title US4198266A (en) 1980-04-15 Oxygen delignification of wood pulp US3655343A (en) 1972-04-11 Apparatus for oxidizing a spent pulping liquor US5338366A (en) 1994-08-16 Acid pre-hydrolysis reactor system CN1036728C (en) 1997-12-17 Process for continuous cooking of pulp US5498347A (en) 1996-03-12 Reactor for the ozonization of water GB2141942A (en) 1985-01-09 Mixing apparatus AU613952B2 (en) 1991-08-15 Method of bleaching or delignification of cellulose pulp with oxygen CA2045436A1 (en) 1992-03-01 Gas sparged centrifugal separation and/or mixing AU595842B2 (en) 1990-04-12 Pulp bleaching US4853136A (en) 1989-08-01 Process for oxidizing substances dissolved or in suspension in an aqueous solution US5411633A (en) 1995-05-02 Medium consistency pulp ozone bleaching JPS61113889A (en) 1986-05-31 Control of oxygen bleaching process JPH06299496A (en) 1994-10-25 Sizing method for paper IE922086A1 (en) 1992-12-30 Treatment of water Scott et al. 1966 Gas absorption in horizontal cocurrent bubble flow US4239590A (en) 1980-12-16 Method of maintaining uniformity of fibrous material fed to a continuous digester US4058433A (en) 1977-11-15 Conversion of sulfur in blank liquor to eliminate odorous emissions and facilitate the collection of sulfate soaps NZ226059A (en) 1990-04-26 Continuous method for bleaching or delignification of cellulose pulp; apparatus therefor CA1080214A (en) 1980-06-24 Mixing apparatus EP0167060B1 (en) 1990-01-31 A process for dispersing one fluid in another EP1528149A1 (en) 2005-05-04 Low consistency oxygen delignification process CA1332833C (en) 1994-11-01 Process for contacting gases with liquids JPH01160476A (en) 1989-06-23 Bubble tower-type reactor JPS6171900A (en) 1986-04-12 Method and device for particularly adjusting waste water sludge Wood et al. 1973 Factors influencing batch flotation tests
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