GB2423310A - Method of generating a pressure differential - Google Patents

Method of generating a pressure differential Download PDF

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Publication number
GB2423310A
GB2423310A GB0503650A GB0503650A GB2423310A GB 2423310 A GB2423310 A GB 2423310A GB 0503650 A GB0503650 A GB 0503650A GB 0503650 A GB0503650 A GB 0503650A GB 2423310 A GB2423310 A GB 2423310A
Authority
GB
United Kingdom
Prior art keywords
spacer elements
vessel
pressure
pressure vessel
wood
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.)
Withdrawn
Application number
GB0503650A
Other versions
GB0503650D0 (en
Inventor
Ian Robert Berriman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Arch Timber Protection Ltd
Original Assignee
Arch Timber Protection 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.)
Filing date
Publication date
Application filed by Arch Timber Protection Ltd filed Critical Arch Timber Protection Ltd
Priority to GB0503650A priority Critical patent/GB2423310A/en
Publication of GB0503650D0 publication Critical patent/GB0503650D0/en
Publication of GB2423310A publication Critical patent/GB2423310A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
    • B27K3/02—Processes; Apparatus
    • B27K3/08—Impregnating by pressure, e.g. vacuum impregnation
    • B27K3/10—Apparatus
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J3/00—Processes of utilising sub-atmospheric or super-atmospheric pressure to effect chemical or physical change of matter; Apparatus therefor
    • B01J3/006—Processes utilising sub-atmospheric pressure; Apparatus therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J3/00—Processes of utilising sub-atmospheric or super-atmospheric pressure to effect chemical or physical change of matter; Apparatus therefor
    • B01J3/04—Pressure vessels, e.g. autoclaves
    • B01J3/042—Pressure vessels, e.g. autoclaves in the form of a tube
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
    • B27K—PROCESSES, APPARATUS OR SELECTION OF SUBSTANCES FOR IMPREGNATING, STAINING, DYEING, BLEACHING OF WOOD OR SIMILAR MATERIALS, OR TREATING OF WOOD OR SIMILAR MATERIALS WITH PERMEANT LIQUIDS, NOT OTHERWISE PROVIDED FOR; CHEMICAL OR PHYSICAL TREATMENT OF CORK, CANE, REED, STRAW OR SIMILAR MATERIALS
    • B27K3/00—Impregnating wood, e.g. impregnation pretreatment, for example puncturing; Wood impregnation aids not directly involved in the impregnation process
    • B27K3/02—Processes; Apparatus
    • B27K3/08—Impregnating by pressure, e.g. vacuum impregnation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/18—Details relating to the spatial orientation of the reactor
    • B01J2219/182—Details relating to the spatial orientation of the reactor horizontal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/19—Details relating to the geometry of the reactor
    • B01J2219/194—Details relating to the geometry of the reactor round
    • B01J2219/1941—Details relating to the geometry of the reactor round circular or disk-shaped
    • B01J2219/1943—Details relating to the geometry of the reactor round circular or disk-shaped cylindrical

Abstract

Apparatus comprising a pressure vessel having within it a plurality of removable spacer elements <B>1, 2</B> and means for generating a pressure differential between the exterior and the interior of the vessel. The pressure vessel can be cylindrical and the spacer elements can be made of a polymeric material, preferably polypropylene, polyethylene or acrylonitrile butadiene styrene. The spacer elements can be cylindrical, hollow and/or of different sizes. In another aspect, a method of generating a pressure differential between the exterior and interior of the vessel. The pressure can be elevated or reduced and the apparatus/method is particularly suitable for the treatment of wood. The spacer elements reduce the amount of void space in the pressure vessel, thus reducing the amount of air to be evacuated for vacuum treatment. Also, if liquid treatments are applied, the volume of said liquids is reduced.

Description

Method of Generating a Pressure Differential This invention relates to a
method of generating a pressure differential in a pressure vessel, and a pressure vessel suitable for use in such a method The method is applicable particularly, but not exclusively, to the treatment of wood There is a need to treat wood to provide it with desired properties, e.g to harden it, to protect it against degradation, to protect it against insect attack, or to protect it against the effect of micro-organisms There are many known processes for treating wood Amongst these, some methods are canied out at elevated pressure and some are carried out under vacuum. When carrying out processes under vacuum, the air retained in the vessel must be evacuated, e g by vacuum pump Furthermore, there are known processes which involve filling a treatment vessel charged with wood with liquid media comprising, for example, preservatives Clearly the vessel must be sufficiently filled with the treatment medium in order to carry out the treatment It is an object of the invention to improve on known methods and when viewed from a first aspect, the invention provides a method of generating a pressure differential between the exterior of a pressure vessel and the interior of the pressure vessel comprising generating a pressure differential between the exterior of the vessel and the interior of the vessel, said pressure vessel having within it a plurality of removable spacer elements.
Furthermore, the applicant has devised a pressure vessel suitable for use in such a method When viewed from a second aspect, the invention provides an apparatus comprising a pressure vessel having within it a plurality of removable spacer elements and a means for generating a pressure differential between the exterior and the interior of the vessel Thus it will be seen by those skilled in the art that in accordance with the invention the spacer elements reduce the amount of void space in the pressure vessel. Consequently, the amount of air to be evacuated from the pressure vessel in order to create a vacuum is reduced The capability requirements of the means employed to create a vacuum, e.g vacuum pump, are therefore reduced and evacuation times are shortened Similarly, the requirements of the means employed to create an elevated pressure in the pressure vessel are reduced for the same reasons.
Furthermore, in methods in which liquid compositions are employed, the volume of liquid composition required is minimized and the time taken to fill and/or empty the pressure vessel is reduced Such liquid compositions normally contain chemicals. The spacer elements minimize the amount of chemicals needed and therethre the potential damage to the environment is reduced The pressure differential may involve generating a vacuum in the pressure vessel or may involve generating an elevated pressure in the vessel Preferably the method comprises placing a plurality of pieces of wood in the pressure vessel and treating said wood using a fluid at an elevated or reduced pressure When treating wood, the vessel is charged with wood which is usually in square or rectangular section packs When packs, for example of square or rectangular section, have been inserted into a pressure vessel of, for example, circular cross-section, an unusable void is created between the pack of wood and the wall of the pressure vessel In a preferred embodiment, the method comprises a step in which wood is treated at elevated pressure For instance, the method of the invention may comprise a step in which the pressure is greater than 5 bar, preferably greater than 8 bar, more preferably greater than 10 bar, most preferably at 13 bar Additionally or alternatively the method of the invention may comprise a step in which wood is treated under vacuum The method of the invention may comprise a step in which wood is treated in the presence of a liquid composition. Preferably, the liquid composition comprises one or more wood preservatives The pressure vessel is preferably cylindrical and may be positioned horizontally or vertically as required by the process being used The vessel of the invention could be manufactured from any suitable material, for example, carbon steel, stainless steel, aluminium, or copper and could typically be of welded construction When carried out on a smaller scale, the pressure vessel may be manufactured from any suitable polymeric material The treatment vessel may be of any size In preferred embodiments, it is suitable for the industrial treatment of wood. However, it preferably has a diameter of from I Urn to lOm, preferably from 2 Um to 8.Orn, more preferably from 2 5m to Urn, most preferably from 3 Urn to 4 Urn The length of the treatment vessel may also vary but is preferably from 5 Urn to 25rn in length, more preferably from I Urn to 20m, even more preferably from 12m to 18m, most preferably from l4m to 16m The spacer elements may be made of any suitable robust material For IU instance, they may be made of metal but in order to avoid the need for constructing stronger foundations to support heavier pressure vessels and to allow the methods of the invention to be employed in existing pressure vessels, the spacer elements are preferably made of polymeric material Polymeric materials, e g plastics, are generally lighter than metals and can significantly reduce the weight of the treatment vessels of the invention Of course, the polymeric material employed must be capable of being subjected to the pressure differential that is generated in the methods of the invention If elevated temperatures are also employed in the methods of the invention, the polymeric material must also be capable of being subjected to the required temperature 2U Preferably the polymeric material is capable of being subjected to pressures of between 0 and 15 bar, more preferably between 8 and 14 bar, most preferably 13 bar.
In preferred embodiments the spacer elements are made of one or a mixture of polypropylene, polyethylene, or acrylonitrile butadiene styrene (ABS). Most preferred is polypropylene In preferred embodiments the polymeric material has a density of from U 7 to 1 4 g/cm3, more preferably from U.8 to 1 3 g/cm3, even more preferably from U 9 to 1 2 g/cm3 If the spacer elements are made of polypropylene, the polypropylene preferably has a density of from U 9U to U 91 g/cm3 If the spacer elements are made of polyethylene, the polyethylene preferably has a density of from 0 94 to U 97 g/cm If the spacer elements are made of ABS, the ABS preferably has a density offroml lOtol l5g/cm3 The spacer elements may be any shape. For example, they can be spherical However, in order to facilitate the loading and unloading of the spacer elements into and from the pressure vessel, the spacer elements are preferably prismatic More preferably, the spacer elements are cylindrical Preferably, the spacer elements extend along substantially the whole length of the pressure vessel. This allows them to minimize the amount of void space in the vessel.
In a preferred embodiment the spacer elements are of circular crosssection.
This maximises their ability to withstand a pressure differential for a given wall thickness In the most preferred embodiments of the invention the spacer elements are cylindrical and are of circular cross-section.
The spacer elements may be solid However, in order to make them lighter and maxim ise their volume, the spacer elements are preferably hollow. Lighter spacer elements avoid the need for stronger foundations at the site of treatment, and allow the methods of the present invention to be used in existing treatment sites Where the spacer elements are hollow, it is particularly preferred that they are of circular cross-section so as to maxirnise their ability to withstand pressure and minimise the necessary wall thickness required such that they are capable of being subjected to the pressure differentials created during the course of the methods of the invention When spacer elements which are hollow, cylindrical and of circular cross-section are employed, they preferably have rounded caps at each end, e.g welded on, to enhance their pressure resistance.
When the spacer elements are hollow, they could be evacuated or pressurised as appropriate in order to reduce the pressure differential they experience in use and thus the pressure resistance they are required to have However, to facilitate manufacturing of the spacer elements, the pressure within them is preferably substantially at normal atmospheric pressure In preferred embodiments of the invention, the pressure vessel comprises support means for supporting the spacer elements In arrangements of the invention in which the spacer elements are prismatic, the support means preferably comprises at least two supports for supporting the spacer elements at different points along them Such supports can help to reduce sagging of the spacer elements under their own weight. For example, the pressure vessel may comprise one or more plates along the length of the pressure vessel into which are cut holes through which the spacer elements will fit Due to the accuracy which is required to form the holes, it is preferred that the holes are laser cut Such plates can be made of any suitable material such as stainless steel or carbon steel.
In a preferred embodiment, the support means are arranged such that there is space between the spacer elements. It is preferable to retain at least a minimal gap between the spacer elements in methods employing a liquid composition so as to allow free liquid to run off the surface for pumped recovery In order to avoid movement of these plates, the plates may be welded to the inside wall of the pressure vessel and the plates may be prevented from bending by reinforcing sections manufactured, for example, from steel In preferred embodiments the pressure vessel comprises one or more partition plates between the spacer elements and the main part of the interior of the vessel, e.g containing wood being treated Such partition plates can protect the spacer elements from any movement within the pressure vessel, in particular whilst the wood is being loaded and unloaded.
The spacer elements are preferably of different sizes, i e different cross- sectional areas Different sizes of spacer elements allow optimisation of the void that is taken up within the pressure vessel since it is possible to pack them closer together, particularly where the pressure vessel is curved, e g. circular cross-section In a preferred embodiment of the invention, the spacer elements take up at least 2% of the total volume of the pressure vessel, more preferably at least 5%, even more preferably at least 10%, most preferably at least 20% A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which Fig I is an end view of a pressure vessel in accordance with the invention, and Fig. 2 is a view of an embodiment of a spacer element in accordance with the present invention.
Turning to Figure 1 there may be seen a pressure vessel in accordance with the invention which is adapted for the industrial treatment of wood with preservatives and the like The pressure vessel is cylindrical and generally comprises three horizontal zones 3,4,5 which run the entire length of the pressure vessel, namely a large approximately rectangular central zone 4 and two smaller side zones 3,5 of segment shape. Wood to be treated is charged into the central zone 4 of the treatment vessel, and zones 3 and 5 are charged with a plurality of spacer elements 1,2 in the form of cylinders, preferably made from polypropylene The spacer elements fill up space in the pressure vessel and displace air The pressure vessel contains two sizes of spacer elements The inclusion of larger spacer elements 1 and smaller spacer elements 2 allows the segmented void space to be fitted more efficiently than just using the larger elements, whilst not requiring an unreasonably large number The spacer elements extend substantially along the entire length of the pressure vessel and are supported by a horizontally spaced series of plates 6 are mounted off the internal walls of the vessel The plates 6 provide holes 7 through which the spacer elements fit The plates 6 are made for example from stainless steel or carbon steel and shaped to fit closely to the walls of the pressure vessel Two partition plates 8 are provided to protect the spacer elements when wood is being moved in and out of the pressure vessel. To facilitate loading and unloading of wood, the pressure vessel is provided with internal rails 9 along which the wood can be transported as is well known in the art in addition, the pressure vessel can be provided with antiflotation rails (not shown) to minimise movement of the wood during treatment as is well known in the art Turning to Figure 2 there may be seen a spacer element in accordance with the present invention. The spacer element is prismatic and of circular cross-section The spacer element maybe made of plastic, e g a light-weight plastic such as polypropylene. The spacer elements are hollow, i e. tubes Each tube can be made up of several supplied lengths to make up the individual component and would be butt welded using Butt Fusion machines complete with tooling, including planers, clamps, temperature gauges and heating plates Each tube is then fitted with an end-cap. These are fusion welded to the end of the hollow tubes in the same way as the different lengths of tube described above

Claims (13)

  1. Claims I A method of generating a pressure differential between the
    exterior of a pressure vessel, and the interior of the pressure vessel comprising providing a plurality of removable spacer elements in the vessel then generating a pressure differential between the exterior of the vessel and the interior of the vessel.
  2. 2 The method of claim 1 wherein said method comprises placing a plurality of pieces of wood in the pressure vessel and treating said wood using a fluid at an elevated or reduced pressure
  3. 3 The method of claim 2 wherein said method comprises a step in which wood is treated at elevated pressure.
  4. 4 The method of claim 3 wherein the pressure is greater than
  5. 5 bar The method of any one of claims 2 to 4 wherein said method comprises a step in which wood is treated under vacuum
  6. 6 The method of any one of claims 2 to 5 wherein the fluid is a liquid corn position comprising one or more wood preservatives
  7. 7 The method of any one of the preceding claims wherein the pressure vessel is cylindrical
  8. 8. The method of any one of the preceding claims wherein the spacer elements are made of polymeric matenal
  9. 9. l'he method of claim 8 wherein the polymeric material is polypropylene, polyethylene, or acrylonitrile butadiene styrene
  10. 10. The method of any one of the preceding claims wherein the spacer elements are cylindrical and of circular cross-section
  11. 11 The method of any one of the preceding claims wherein the spacer elements are hollow
  12. 12 The method of any one of the preceding claims wherein the spacer elements are of different sizes.
  13. 13 An apparatus comprising a pressure vessel having within it a plurality of removable spacer elements and a means for generating a pressure differential between the exterior and the interior of the vessel 14 The apparatus of claim 13 wherein the pressure vessel is cylindrical IS The apparatus of either claim 13 or claim 14 wherein the spacer elements are made of polymeric material 16 The apparatus of claim 15 wherein the polymeric material is polypropylene, polyethylene, or acrylonitrile butadiene styrene 17. The apparatus of any one of claims 13 to 16 wherein the spacer elements are cylindrical and of circular cross-section 18 The apparatus of any one of claims 13 to 17 wherein the spacer elements are hollow 19 The apparatus of any one of claims 13 to 18 wherein the spacer elements are of different sizes
GB0503650A 2005-02-22 2005-02-22 Method of generating a pressure differential Withdrawn GB2423310A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB0503650A GB2423310A (en) 2005-02-22 2005-02-22 Method of generating a pressure differential

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB0503650A GB2423310A (en) 2005-02-22 2005-02-22 Method of generating a pressure differential

Publications (2)

Publication Number Publication Date
GB0503650D0 GB0503650D0 (en) 2005-03-30
GB2423310A true GB2423310A (en) 2006-08-23

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ID=34401130

Family Applications (1)

Application Number Title Priority Date Filing Date
GB0503650A Withdrawn GB2423310A (en) 2005-02-22 2005-02-22 Method of generating a pressure differential

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1589781A (en) * 1977-01-10 1981-05-20 Balfour Beatty Ltd Impregnation of fluid-permeable bodies
JPS62270894A (en) * 1986-05-16 1987-11-25 Kobe Steel Ltd Repairing method for pressure vessel with lining
US5948356A (en) * 1995-02-15 1999-09-07 Framatome Process for high-pressure sterilization of products
FR2781413A1 (en) * 1998-07-27 2000-01-28 Clextral Seals between batches of material undergoing high pressure treatment deform under pressure to improve seal.
GB2349933A (en) * 1999-05-12 2000-11-15 Vauxhall Motors Ltd Apparatus for treating elongate members

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1589781A (en) * 1977-01-10 1981-05-20 Balfour Beatty Ltd Impregnation of fluid-permeable bodies
JPS62270894A (en) * 1986-05-16 1987-11-25 Kobe Steel Ltd Repairing method for pressure vessel with lining
US5948356A (en) * 1995-02-15 1999-09-07 Framatome Process for high-pressure sterilization of products
FR2781413A1 (en) * 1998-07-27 2000-01-28 Clextral Seals between batches of material undergoing high pressure treatment deform under pressure to improve seal.
GB2349933A (en) * 1999-05-12 2000-11-15 Vauxhall Motors Ltd Apparatus for treating elongate members

Also Published As

Publication number Publication date
GB0503650D0 (en) 2005-03-30

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)