CA1300321C - Gas diffuser - Google Patents
Gas diffuserInfo
- Publication number
- CA1300321C CA1300321C CA000527165A CA527165A CA1300321C CA 1300321 C CA1300321 C CA 1300321C CA 000527165 A CA000527165 A CA 000527165A CA 527165 A CA527165 A CA 527165A CA 1300321 C CA1300321 C CA 1300321C
- Authority
- CA
- Canada
- Prior art keywords
- slurry
- tube
- casing
- gas
- passage
- Prior art date
- Legal status (The legal status 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 status listed.)
- Expired - Lifetime
Links
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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/30—Injector mixers
- B01F25/31—Injector mixers in conduits or tubes through which the main component flows
- B01F25/313—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced in the centre of the conduit
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
- B01F25/00—Flow mixers; Mixers for falling materials, e.g. solid particles
- B01F25/30—Injector mixers
- B01F25/31—Injector mixers in conduits or tubes through which the main component flows
- B01F25/313—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced in the centre of the conduit
- B01F25/3133—Injector mixers in conduits or tubes through which the main component flows wherein additional components are introduced in the centre of the conduit characterised by the specific design of the injector
- B01F25/31331—Perforated, multi-opening, with a plurality of holes
- B01F25/313311—Porous injectors
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
Abstract
ABSTRACT
A diffusing unit made up of an elongated cylindrical casing and an elongated gas diffusing tube, having a microporous surface, held axially therein. The casing and tube provide an annular passage for fast moving agitated pulp slurry, receiving masses of gas bubbles from the porous surface. Gas is supplied through a connection leading through the casing to the diffusing tube, downstream of the microporous surface, and the upstream end of the tube is tapered and mounted so as to minimize obstruction to the smooth flow of the slurry in contact with the microporous surface. Apparatus is employed in a method of bleaching, in which bleaching gas is intimately mixed in a cellulose pulp slurry and subsequently reacted with the cellulose.
A diffusing unit made up of an elongated cylindrical casing and an elongated gas diffusing tube, having a microporous surface, held axially therein. The casing and tube provide an annular passage for fast moving agitated pulp slurry, receiving masses of gas bubbles from the porous surface. Gas is supplied through a connection leading through the casing to the diffusing tube, downstream of the microporous surface, and the upstream end of the tube is tapered and mounted so as to minimize obstruction to the smooth flow of the slurry in contact with the microporous surface. Apparatus is employed in a method of bleaching, in which bleaching gas is intimately mixed in a cellulose pulp slurry and subsequently reacted with the cellulose.
Description
13U03~1 This invention relates to the introduction of bleaching gas into a pulp slurry.
More particularly, the invention concerns a method of dispensing oxygen, in a mass of minute bubbles, into a stream of cellulose pulp slurry and subsequently causing the oxygen to react with the cellulose to provide delignification or bleaching.
Considerable work has been done on the use of oxygen for delignification or bleaching, as described in Canadian Patent Application 507,000, Lee et al filed April 18, 1985, and the patents and publications referred to therein.
One of the problems is to bring about intimate contact between the oxygen and the cellulose, throughout the slurry. To this end, the prior application discloses a method in which a stream of cellulose pulp slurry is forcibly fed through a cylindrical casing providing a passage so that the slurry has a velocity at which it behaves as a liquid.
Oxygen is diffused, through a microporous wall in intimate contact with the slurry in the form of minute bubbles, which are rapidly mixed throughout by the turbulence of the slurry.
The stream, containing the oxygen bubbles dispersed throughout, is then released into a reactor passage of much greater cross-section than the diffusing and mixing passage, so that the slurry assumes plug flow and the oxygen has time to react with the cellulose.
One apparatus, in which this is done, includes a cylindrical casing enclosing a diffusing-mixing passage and an elongated diffusing tube extending axially and mounted centrally of the passage and provided with a microporous 1;~)03;~1 -la-wall. The tube is supported and held in place by a spider at each end. An oxygen supply connection extends from the wall of the casing, including an elbow, to the upstream end of the tube.
The upstream end of the casing leads from a pump effective to feed the slurry under a pressure such that it acts as a liquid in the casing. The downstream end of the casing leads to a reactor where ' 13~0~1 the slurry proceeds at plug flow velocity, providing residence time for reaction with the pulp.
The applicant has now found that, because of the high velo-city of the pulp going through the casing, what might otherwise be considered, by one skilled in the art, to be detailed modifications of construction are actually features of great importance e~ the "fine tuning" of the diffusion-mixing method, to bring about maximum efficiency.
Having regard to what has been said, the invention will be summarized as follows. In an apparatus of the type just described, the diffusing tube is firmly, but detachably, mounted axially and centrally of the casing. The upstream end of the tube is supported from the casing by supporting means which offers minimum resistance to the flow of the slurry into the casing. This can be a spider extending from the wall of the casing which supports a pin aligned axially and centrally of the casing and extending downstream thereof to receive the upstream end of the tube.
An oxygen supply connection leads from the wall of the casing, in the cross-stream direction, to the downstream end of the tube. This connection preferably includes an elbow and short pipe lengths connecting it to the casing end and the end of the tube respectively. Preferably the oxygen connection is also used to support the downstream end of the tube from the casing wall.
In a preferred construction, the upstream spider supports a pin aligned centrally and axially of the casing and extending down-stream thereof which fits into a receiving bore in a tapered nose piece on the diffusing tube. This allows for a certain amount of axial play of the upstream end of the diffusing tube to take care of expansion or other slight displacement of the nose of the diffusing tube. Preferably the spider is provided with vanes angled to the direction of incoming slurry flow so as to direct it spirally into the diffusing and mixing passage.
13~03Z~
In this way, the downstream end of the diffusing tube can be supported entirely by the oxygen supply connections so that additional support at the downstream end is not required. The fixtures include a special nut connected to the downstream end of the diffusion tube, the nut being disconnectably connected, in turn, to a sleeve which joins one end of an elbow and the other end of which is connected to a sleeve which extends cross-stream to a wall of the casing and is connected thereto.
Arrangement of the parts, in the manner described, permits the streamlined flow of the rapidly moving slurry through the diffusion and mixing passage in contact with the diffusing tube without the formation of eddies or other irregularities which would interfere with the efficient diffusion of the oxygen throughout the slurry.
Where vanes are employed at the upstream end of the passage, the streamlined flow is spiraled about the diffusing tube providing still better access of the bubbles to the slurry. The construction des-cribed also permits ready assembly and disassembly.
More specific features of the invention will be apparent from the following detailed description. In this detailed description, the drawing is a perspective view in partial vertical cross-section through the casing.
Referring more particularly to the drawings, the main parts of the preferred diffusing apparatus shown include an elongated cylindrical casing R. An elongated diffusion tube S extends axially and centrally of the casing R and has a slurry-contacting microporous wall positioned for direct contact with the pulp slurry travelling through the annular passage P formed between the surfaces of the casing R and the tube S, whereby oxygen supplied to the tube S is diffused into the pulp slurry in the form of minute bubbles.
30The apparatus is constructed as follows. The casing R has a LJ ~
flange 117 at the upstream end 4~ a flange 119 at the downstream end.
13Q(~3Zl The flange 117 is mounted on a plate 121 supported from superstructure. The flange 119 is mounted on a plate 123 supported from superstructure. The p]ate 121 is provided with a circular inlet opening 121a of the same diameter as the inside diameter of the casing R. The plate 123 has a circular outlet opening 123a having a diameter smaller than that of the inside diameter of the casing R and concentric to it. A spider, indicated generally by 131, is held within the opening 121a by several converging legs 133, preferably vanes, having their outer ends connected to a ring 135, fixed to the inside surface of the plate 121, surrounding the opening 121a. The inside ends of the legs are fixed to a mounting pin 136 extending axially therefrom in the downstream direction.
The diffusing tube S is provided, at its upstream end, with a tapered nose piece 138 having an internal socket opening 137 which receives the pin 136 in a sliding fit.
The downstream end of the tube 125 is provided with a gas supply connection including hexagonal nut 143, pipe section 144 and an elbow 141 which, in turn, is connected to a short pipe section 149 which joins a pipe 147 extending in the cross-stream direction through the wall of the casing R
and connected to it as at 126.
The upstream end of the casing R is connected downstream of pump capable of delivering the pulp at a pressure such that when it is confined in the passage P, its velocity is such that the slurry acts like a turbulent liquid. The downstream end of the casing R is connected to a - ~a-reactor for receiving the pulp with the gas bubbles mixedthroughout. This arrangement of pump, diffusing apparatus and reactor is shown in Canadian Patent Application 507,000.
The diffuser tube S is connected to a continuous supply of bleaching gas under pressure. Appropriate controls are included in the system for controlling the pulp slurry pressure and the gas pressure.
Operation The pulp slurry is delivered continuously by the pump to the upstream end of the casing R at a pressure such that it assumes a velocity within the annular diffusing and mixing passage P, at which the slurry behaves as a liquid.
The slurry passes rapidly through the passage P, surrounding lS and, in intimate contact with the tube 115, and exits through the outlet opening 123a. Meanwhile, oxygen under pressure is continuously passed into the tube S, whence it is diffused through the microporous wall into the slurry in the form of a mass of minute bubbles which are immediately mixed throughout the turbulent liquid-behaving slurry.
On leaving the passage P, the slurry containing gas bubbles dispersed throughout passes into a reactor of much greater cross-section than that of the passage P. The velocity of the slurry is thus reduced to plug flow and is retained in the reactor to give time for the gas to react with the cellulose.
Preferably the spider 131 is provided with vanes angled to the direction of flow of the slurry, so as to guide it, in a spiral path, about the tube S.
~a .
13V03;~1 The principle of diffusing and mixing oxygen in a mass of small bubbles into the pulp slurry moving at a velocity at which it behaves as a liquid is described in Canadian Patent Application 507,000. The present invention provides refinements enabling the method to be carried out with greater efficiency.
Constructional Features The connection between the diffusion tube S and the casing wall downstream of the tube S improves the flow pattern of the slurry. The applicant has found that, with the gas supply connection to the diffusing tube extending transversely to the flow, at the upstream end, undesirable interruption of the flow pa-ttern takes place. This can be considerable at the high velocity at which the slurry flows 1~003~1 through the passage and eddies are formed which result in unven distribution of the gas bubbles in the slurry.
At the upstream end, centering the diffusing tube in the casing ~ , with a nose piece 138 tapered, streamlines the flow of slurry around the tube S with a minimum disturbance of the flow pattern. The upstream end of the tube S is also mounted so that it can move axially to accommodate limited movement of that end of the tube with temperature changes or other forces.
The spider 131, mounting the diffusing tube S, at the up-stream end is designed to offer minimum obstruction to the flow ofthe slurry. It is provided with slender vanes, preferably slightly angled to the direction of flow so as to induce a spiral flow of slurry through the passage P. This improves the interface contact between the slurry and tube 125 which, in turn, contributes to better diffusion of the bubbles into the slurry.
Advantages The diffuser is uniquely suspended to optimize the forma-tion of bubbles in a laminar flow in the liquid and the dispersion of bubbles is further mixed into the fluid flow by an angular dis-turbance through an expansion of the pipe into a low velocity region.
The invention permits larger gas flows producing smallbubbles at a minimum gas and liquid pressure drop. The diffuser is positioned to benefit from a slight radial flow from an upstream elbow, without producing turbulence and vortices which interfere with bubble formation.
The unique suspension system positions the diffuser to permit axial flexibility to accommodate thermal expansions and maintains the diffuser on the centerline of the pipe to prevent side loads which would damage the brittle diffuser wall material.
The gas is delivered to the diffuser which is in the centerline of the pipe by means of a feed elbow at the downstream end of the .
~.3~0~21 5~ k~ ~ ~ diffuser. This eliminates the Von Karman vortex ~Y~t which would flow over the diffuser if the feed elbow were located, in the con-ventional manner, at the upstream end of the diffuser.
The position of the diffuser on the centerline of the pipe causes the porous surface to be parallel to the liquid flow and eliminates damage to it by tramp materials in the slurry.
The inside diameter of the casing and outside diameter of the diffuser are sized to optimize the slurry velocity to maintain fluidity it it is a pulp stock suspension of any concentration.
Provision is made for in-situ cleaning by H.P. steam or other solvent as required to remove contaminents which may adhere to the diffuser surface.
The unique suspension system for the upstream end of the diffuser may be made of streamlined materials or designed to cause a slight rotation of the liquid as it passes over the diffuser surface.
Downstream of the diffuser a vane or angled orifice is used to discharge the liquid into a larger diameter pipe to cause macro-mixing of the fine bubbles into the liquid.
The gas inlet pressure may be monitored to indicate the condition of the diffuser.
The tapered streamlined cone ensures laminar flow over the diffuser. This cone also provides the sliding fit required to allow axial movement for thermal expansion. This axial flexibility eliminates the need for accurate assembly procedures and accommodates various gasket thicknesses between the diffuser pipe section and the inlet piping along with variations in the assembly caused by varying clamping forces between the flange halves.
The rapid expansion from the diffuser pipe into the larger diameter process piping increases the macro-mixing of the bubbles dispersion into the liquid.
13(;~(~3~1 The high shear flow field around the diffuser causes a velocity distribution which forces the bubbles to move into the high shear zone and increase the radial displacement of the bubbles from the diffuser surface.
This design permits the surface area to be optimized by varying the diameter and length to minimize the gas pressure drop and remain within the proper ratio of diffuser surface to gas flow-rate which minimizes the bubble size.
Variable Factors Generally speaking, the criteria of the method, using the improved diffuser of the invention, are similar to those of prior application 507,000.
The following are preferred criteria.
Pulp consistency within the range of 8% to 16%, desirably 10% to 12%.
Velocity of pulp slurry in passage P, 5 to 50 meters a second.
Bleaching gas - an oxygen-containing gas containing 90% or more of oxygen and preferably 98% or more.
Porosity of microporous walls such as to provide minute bubbles, desirably less than 10 microns in diameter.
Slurry temperature, 40C to 90C.
Bleaching gas temperature, at least that of the slurry temperature.
Oxygen injection through diffuser S in an amount to satisfy the formula:
Volume of oxygen + gas Volume (oxygen + gas + pulp) < 0-1 and generally within the range from 30 to 300 normal cubic meters per minute per square meter of porous surface.
There may also be several stages in each of which the slurry is passed through a diffuser, according to the in~ention, followed by a reactor as explained in prior application 507,000.
More particularly, the invention concerns a method of dispensing oxygen, in a mass of minute bubbles, into a stream of cellulose pulp slurry and subsequently causing the oxygen to react with the cellulose to provide delignification or bleaching.
Considerable work has been done on the use of oxygen for delignification or bleaching, as described in Canadian Patent Application 507,000, Lee et al filed April 18, 1985, and the patents and publications referred to therein.
One of the problems is to bring about intimate contact between the oxygen and the cellulose, throughout the slurry. To this end, the prior application discloses a method in which a stream of cellulose pulp slurry is forcibly fed through a cylindrical casing providing a passage so that the slurry has a velocity at which it behaves as a liquid.
Oxygen is diffused, through a microporous wall in intimate contact with the slurry in the form of minute bubbles, which are rapidly mixed throughout by the turbulence of the slurry.
The stream, containing the oxygen bubbles dispersed throughout, is then released into a reactor passage of much greater cross-section than the diffusing and mixing passage, so that the slurry assumes plug flow and the oxygen has time to react with the cellulose.
One apparatus, in which this is done, includes a cylindrical casing enclosing a diffusing-mixing passage and an elongated diffusing tube extending axially and mounted centrally of the passage and provided with a microporous 1;~)03;~1 -la-wall. The tube is supported and held in place by a spider at each end. An oxygen supply connection extends from the wall of the casing, including an elbow, to the upstream end of the tube.
The upstream end of the casing leads from a pump effective to feed the slurry under a pressure such that it acts as a liquid in the casing. The downstream end of the casing leads to a reactor where ' 13~0~1 the slurry proceeds at plug flow velocity, providing residence time for reaction with the pulp.
The applicant has now found that, because of the high velo-city of the pulp going through the casing, what might otherwise be considered, by one skilled in the art, to be detailed modifications of construction are actually features of great importance e~ the "fine tuning" of the diffusion-mixing method, to bring about maximum efficiency.
Having regard to what has been said, the invention will be summarized as follows. In an apparatus of the type just described, the diffusing tube is firmly, but detachably, mounted axially and centrally of the casing. The upstream end of the tube is supported from the casing by supporting means which offers minimum resistance to the flow of the slurry into the casing. This can be a spider extending from the wall of the casing which supports a pin aligned axially and centrally of the casing and extending downstream thereof to receive the upstream end of the tube.
An oxygen supply connection leads from the wall of the casing, in the cross-stream direction, to the downstream end of the tube. This connection preferably includes an elbow and short pipe lengths connecting it to the casing end and the end of the tube respectively. Preferably the oxygen connection is also used to support the downstream end of the tube from the casing wall.
In a preferred construction, the upstream spider supports a pin aligned centrally and axially of the casing and extending down-stream thereof which fits into a receiving bore in a tapered nose piece on the diffusing tube. This allows for a certain amount of axial play of the upstream end of the diffusing tube to take care of expansion or other slight displacement of the nose of the diffusing tube. Preferably the spider is provided with vanes angled to the direction of incoming slurry flow so as to direct it spirally into the diffusing and mixing passage.
13~03Z~
In this way, the downstream end of the diffusing tube can be supported entirely by the oxygen supply connections so that additional support at the downstream end is not required. The fixtures include a special nut connected to the downstream end of the diffusion tube, the nut being disconnectably connected, in turn, to a sleeve which joins one end of an elbow and the other end of which is connected to a sleeve which extends cross-stream to a wall of the casing and is connected thereto.
Arrangement of the parts, in the manner described, permits the streamlined flow of the rapidly moving slurry through the diffusion and mixing passage in contact with the diffusing tube without the formation of eddies or other irregularities which would interfere with the efficient diffusion of the oxygen throughout the slurry.
Where vanes are employed at the upstream end of the passage, the streamlined flow is spiraled about the diffusing tube providing still better access of the bubbles to the slurry. The construction des-cribed also permits ready assembly and disassembly.
More specific features of the invention will be apparent from the following detailed description. In this detailed description, the drawing is a perspective view in partial vertical cross-section through the casing.
Referring more particularly to the drawings, the main parts of the preferred diffusing apparatus shown include an elongated cylindrical casing R. An elongated diffusion tube S extends axially and centrally of the casing R and has a slurry-contacting microporous wall positioned for direct contact with the pulp slurry travelling through the annular passage P formed between the surfaces of the casing R and the tube S, whereby oxygen supplied to the tube S is diffused into the pulp slurry in the form of minute bubbles.
30The apparatus is constructed as follows. The casing R has a LJ ~
flange 117 at the upstream end 4~ a flange 119 at the downstream end.
13Q(~3Zl The flange 117 is mounted on a plate 121 supported from superstructure. The flange 119 is mounted on a plate 123 supported from superstructure. The p]ate 121 is provided with a circular inlet opening 121a of the same diameter as the inside diameter of the casing R. The plate 123 has a circular outlet opening 123a having a diameter smaller than that of the inside diameter of the casing R and concentric to it. A spider, indicated generally by 131, is held within the opening 121a by several converging legs 133, preferably vanes, having their outer ends connected to a ring 135, fixed to the inside surface of the plate 121, surrounding the opening 121a. The inside ends of the legs are fixed to a mounting pin 136 extending axially therefrom in the downstream direction.
The diffusing tube S is provided, at its upstream end, with a tapered nose piece 138 having an internal socket opening 137 which receives the pin 136 in a sliding fit.
The downstream end of the tube 125 is provided with a gas supply connection including hexagonal nut 143, pipe section 144 and an elbow 141 which, in turn, is connected to a short pipe section 149 which joins a pipe 147 extending in the cross-stream direction through the wall of the casing R
and connected to it as at 126.
The upstream end of the casing R is connected downstream of pump capable of delivering the pulp at a pressure such that when it is confined in the passage P, its velocity is such that the slurry acts like a turbulent liquid. The downstream end of the casing R is connected to a - ~a-reactor for receiving the pulp with the gas bubbles mixedthroughout. This arrangement of pump, diffusing apparatus and reactor is shown in Canadian Patent Application 507,000.
The diffuser tube S is connected to a continuous supply of bleaching gas under pressure. Appropriate controls are included in the system for controlling the pulp slurry pressure and the gas pressure.
Operation The pulp slurry is delivered continuously by the pump to the upstream end of the casing R at a pressure such that it assumes a velocity within the annular diffusing and mixing passage P, at which the slurry behaves as a liquid.
The slurry passes rapidly through the passage P, surrounding lS and, in intimate contact with the tube 115, and exits through the outlet opening 123a. Meanwhile, oxygen under pressure is continuously passed into the tube S, whence it is diffused through the microporous wall into the slurry in the form of a mass of minute bubbles which are immediately mixed throughout the turbulent liquid-behaving slurry.
On leaving the passage P, the slurry containing gas bubbles dispersed throughout passes into a reactor of much greater cross-section than that of the passage P. The velocity of the slurry is thus reduced to plug flow and is retained in the reactor to give time for the gas to react with the cellulose.
Preferably the spider 131 is provided with vanes angled to the direction of flow of the slurry, so as to guide it, in a spiral path, about the tube S.
~a .
13V03;~1 The principle of diffusing and mixing oxygen in a mass of small bubbles into the pulp slurry moving at a velocity at which it behaves as a liquid is described in Canadian Patent Application 507,000. The present invention provides refinements enabling the method to be carried out with greater efficiency.
Constructional Features The connection between the diffusion tube S and the casing wall downstream of the tube S improves the flow pattern of the slurry. The applicant has found that, with the gas supply connection to the diffusing tube extending transversely to the flow, at the upstream end, undesirable interruption of the flow pa-ttern takes place. This can be considerable at the high velocity at which the slurry flows 1~003~1 through the passage and eddies are formed which result in unven distribution of the gas bubbles in the slurry.
At the upstream end, centering the diffusing tube in the casing ~ , with a nose piece 138 tapered, streamlines the flow of slurry around the tube S with a minimum disturbance of the flow pattern. The upstream end of the tube S is also mounted so that it can move axially to accommodate limited movement of that end of the tube with temperature changes or other forces.
The spider 131, mounting the diffusing tube S, at the up-stream end is designed to offer minimum obstruction to the flow ofthe slurry. It is provided with slender vanes, preferably slightly angled to the direction of flow so as to induce a spiral flow of slurry through the passage P. This improves the interface contact between the slurry and tube 125 which, in turn, contributes to better diffusion of the bubbles into the slurry.
Advantages The diffuser is uniquely suspended to optimize the forma-tion of bubbles in a laminar flow in the liquid and the dispersion of bubbles is further mixed into the fluid flow by an angular dis-turbance through an expansion of the pipe into a low velocity region.
The invention permits larger gas flows producing smallbubbles at a minimum gas and liquid pressure drop. The diffuser is positioned to benefit from a slight radial flow from an upstream elbow, without producing turbulence and vortices which interfere with bubble formation.
The unique suspension system positions the diffuser to permit axial flexibility to accommodate thermal expansions and maintains the diffuser on the centerline of the pipe to prevent side loads which would damage the brittle diffuser wall material.
The gas is delivered to the diffuser which is in the centerline of the pipe by means of a feed elbow at the downstream end of the .
~.3~0~21 5~ k~ ~ ~ diffuser. This eliminates the Von Karman vortex ~Y~t which would flow over the diffuser if the feed elbow were located, in the con-ventional manner, at the upstream end of the diffuser.
The position of the diffuser on the centerline of the pipe causes the porous surface to be parallel to the liquid flow and eliminates damage to it by tramp materials in the slurry.
The inside diameter of the casing and outside diameter of the diffuser are sized to optimize the slurry velocity to maintain fluidity it it is a pulp stock suspension of any concentration.
Provision is made for in-situ cleaning by H.P. steam or other solvent as required to remove contaminents which may adhere to the diffuser surface.
The unique suspension system for the upstream end of the diffuser may be made of streamlined materials or designed to cause a slight rotation of the liquid as it passes over the diffuser surface.
Downstream of the diffuser a vane or angled orifice is used to discharge the liquid into a larger diameter pipe to cause macro-mixing of the fine bubbles into the liquid.
The gas inlet pressure may be monitored to indicate the condition of the diffuser.
The tapered streamlined cone ensures laminar flow over the diffuser. This cone also provides the sliding fit required to allow axial movement for thermal expansion. This axial flexibility eliminates the need for accurate assembly procedures and accommodates various gasket thicknesses between the diffuser pipe section and the inlet piping along with variations in the assembly caused by varying clamping forces between the flange halves.
The rapid expansion from the diffuser pipe into the larger diameter process piping increases the macro-mixing of the bubbles dispersion into the liquid.
13(;~(~3~1 The high shear flow field around the diffuser causes a velocity distribution which forces the bubbles to move into the high shear zone and increase the radial displacement of the bubbles from the diffuser surface.
This design permits the surface area to be optimized by varying the diameter and length to minimize the gas pressure drop and remain within the proper ratio of diffuser surface to gas flow-rate which minimizes the bubble size.
Variable Factors Generally speaking, the criteria of the method, using the improved diffuser of the invention, are similar to those of prior application 507,000.
The following are preferred criteria.
Pulp consistency within the range of 8% to 16%, desirably 10% to 12%.
Velocity of pulp slurry in passage P, 5 to 50 meters a second.
Bleaching gas - an oxygen-containing gas containing 90% or more of oxygen and preferably 98% or more.
Porosity of microporous walls such as to provide minute bubbles, desirably less than 10 microns in diameter.
Slurry temperature, 40C to 90C.
Bleaching gas temperature, at least that of the slurry temperature.
Oxygen injection through diffuser S in an amount to satisfy the formula:
Volume of oxygen + gas Volume (oxygen + gas + pulp) < 0-1 and generally within the range from 30 to 300 normal cubic meters per minute per square meter of porous surface.
There may also be several stages in each of which the slurry is passed through a diffuser, according to the in~ention, followed by a reactor as explained in prior application 507,000.
Claims (8)
1. An apparatus for diffusing a bleaching gas into a pulp slurry, comprising, an elongated imperforate tubular casing leading from an upstream inlet to a downstream outlet, an elongated diffuser tube having a microporous wall and of smaller diameter than that of the casing, held in an axial position within the casing whereby the diffuser tube and casing form therebetween an annular passage for pulp slurry, and a gas supply connection leading in a cross-stream direction from the casing wall to one end of the tube, in which, the gas supply connection is to the downstream end of the tube.
2. An apparatus, as defined in claim 1, in which the upstream end of the tube has a tapered nose to reduce resistance to the flow of slurry.
3. An apparatus, as defined in claim 1, in which there is spider means extending from the casing to support the tube at the upstream end.
4. An apparatus, as defined in claim 1, in which the upstream end of the tube has a tapered nose and there is spider means extend-ing from the casing to support the upstream end of the tube whereby resistance to the flow of slurry is minimized.
5. An apparatus, as defined in claim 2, in which the spider means is provided with centrally located means for engaging the nose to prevent lateral movement but allowing limited axial movement.
6. An apparatus, as defined in claim 2, in which the gas supply connection includes an elbow and means connecting one end of the elbow to the tube and the other end to the wall of the casing.
7. A method of bleaching or delignification of cellulose pulp, in which pulp slurry is force fed through a restricted annular passage between the inside of a cylindrical casing and the outside surface of a diffusing and mixing tube supported axially and centrally in said passage and having a microporous wall in direct contact with the slurry, the slurry being fed at a velocity such that, confined by the passage, it behaves as a turbulent liquid, the slurry being fed past a supply connection for gas extending from the wall of the casing at one end of the tube, comprising, feeding the slurry into the end of the passage remote from the supply connection whereby gas is introduced into the slurry before the slurry encounters the supply connection.
8. A method, as defined in claim 7 in which the slurry is acted on as it enters the passage to cause it to assume a spiral path about the diffusion tube.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000527165A CA1300321C (en) | 1987-01-13 | 1987-01-13 | Gas diffuser |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000527165A CA1300321C (en) | 1987-01-13 | 1987-01-13 | Gas diffuser |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1300321C true CA1300321C (en) | 1992-05-12 |
Family
ID=4134736
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000527165A Expired - Lifetime CA1300321C (en) | 1987-01-13 | 1987-01-13 | Gas diffuser |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1300321C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3485968A4 (en) * | 2016-06-15 | 2020-02-12 | Satoshi Anzai | Ultrafine bubble generation device for aquaculture or wastewater treatment |
-
1987
- 1987-01-13 CA CA000527165A patent/CA1300321C/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3485968A4 (en) * | 2016-06-15 | 2020-02-12 | Satoshi Anzai | Ultrafine bubble generation device for aquaculture or wastewater treatment |
| US11084003B2 (en) | 2016-06-15 | 2021-08-10 | Satoshi ANZAI | Ultrafine bubble generation device for aquaculture or wastewater treatment |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4601165B2 (en) | Method and apparatus for supplying chemical agents into a liquid stream | |
| US7878705B2 (en) | Static mixing element and method of mixing a drilling liquid | |
| US4474477A (en) | Mixing apparatus | |
| US5322222A (en) | Spiral jet fluid mixer | |
| KR920007009B1 (en) | Method of and means for hydro-dynamic mixing | |
| US5183335A (en) | Hydraulic jet flash mixer with flow deflector | |
| CA2167719A1 (en) | Nozzle including a venturi tube creating external cavitation collapse for atomization | |
| ES8200822A1 (en) | Device for mixing carbonated liquids and solid particles with turbulance. | |
| AU603891B2 (en) | Process and device for injecting a matter in fluid form into a hot gaseous flow and apparatus carrying out this process | |
| AU595842B2 (en) | Pulp bleaching | |
| US4840753A (en) | Device for aerating fluids, in particular during flotation | |
| US5023021A (en) | Cartridge venturi | |
| US6869213B2 (en) | Apparatus for injecting a chemical upstream of an inline mixer | |
| JP2681711B2 (en) | Method and device for dissolving a fixed amount of gas in a fixed amount of flowing liquid | |
| CA1300321C (en) | Gas diffuser | |
| SU1498545A1 (en) | Uniflow mixer | |
| US5256375A (en) | Mixing device | |
| CN208727215U (en) | Venturi microbubble generator | |
| RU2585029C2 (en) | Mixer | |
| SU1308370A1 (en) | Jet mixer-reactor | |
| JPH11304067A (en) | Mixed fluid pipeline | |
| CN211864584U (en) | Micro-power gas-liquid or liquid-liquid mixed nano-scale fluid generator | |
| SE9804552D0 (en) | Method and apparatus for mixing a flowing gas and a powdered material | |
| CN107570029A (en) | Feeder for gas-liquid mixed | |
| CN111151150A (en) | Micro-power gas-liquid or liquid-liquid mixed nano-scale fluid generator |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |