WO2003049881A1

WO2003049881A1 - Method and apparatus for inside cleaning of containers

Info

Publication number: WO2003049881A1
Application number: PCT/DK2001/000729
Authority: WO
Inventors: Steffen Carøe VESTERGAARD
Original assignee: Toftejorg Technology A/S; J. Hvidtved Larsen A/S
Priority date: 2001-11-05
Filing date: 2001-11-05
Publication date: 2003-06-19
Also published as: AU2002213837A1

Abstract

A method and apparatus for inside cleaning of a container (11) to be cleaned for liquids (12), solids (12b), or residues (12c) present therein, the method and apparatus comprising steps and means for (a) providing a cleaning liquid (10) different from the liquids, solids, or residues present in the container to be cleaned; (b) introducing said cleaning liquid into the inside of the container without atomisation of said cleaning liquid; (c) withdrawing said introduced cleaning liquid from the container; (d) collecting said withdrawn cleaning liquid in a spent liquid container (7a); (e) separating said cleaning liquid from said collected, spent cleaning liquid from the container to be cleaned; and (f) recirculating said separated cleaning liquid into the inside of the container to be cleaned.

Description

METHOD AND APPARATUS FOR INSIDE CLEANING OF CONTAINERS

DESCRIPTION

1. BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for inside cleaning of containers to be cleaned for gasses, liquids, solids, or residues present therein.

The Technical Field

Many chemical engineering processes in various fields of chemical, pharmaceutical, and food- industry involve application of containers, e.g. containers for containing gasses, liquids, and solids for reaction and storage purposes. The containers are be applied in various processes, including continuous processes as well as batch processes, in applications for which the containers are to be cleaned inside for residues and contaminations on inner surfaces of the containers and surfaces of auxiliary equipment contained therein, and undesired gasses, before e.g. fresh materials are introduced therein, or e.g. before manual inspection of the interior of thereof.

Examples of fields of industry requiring inside cleaning of containers include refineries storing mineral oil and storing refined products of e.g. hydrocarbons; pharma^¬ ceutical industry producing biological compounds and substances in fermentation tanks containing aqueous nutrient culturing media; and food industry producing e.g. vegetable oils involving separation and storage tanks of immiscible liquids and solids such as vegetable oil, water, and plant residues, and various dairy products .

Cleaning operations of such containers in manual batch operations involve personnel entering inside the container and applying cleaning liquids to the inner walls of the container as well as to any auxiliary equipment therein. Besides health hazardous aspects of cleaning personnel, manual cleaning operations often imply polluting discharge of gasses, e.g. hydrocarbons, liquids and solids to the environment, and long shut down periods of the production processes resulting in loss of production and increasing costs of cleaning.

Consequently, there is a need for improving conditions of inside cleaning of containers so that risks to personnel and environment as well as production losses and costs are kept low.

Known tank cleaning systems for cleaning tanks comprises means for applying high pressure cleaning liquid, typically at pressures in the range 100 to 1000 bars, through a wash head in a tank to be cleaned. A drawback of these systems is that the high pressurized cleaning liquid only functions properly as cleaning liquid over relatively short distances of typically less than 1 to 2 meters before the high-pressurized cleaning liquid atomizes into an aerosol. Such an aerosol having little impact on the exposed surfaces to be cleaned and consequently has little cleaning power.

Further, such high-pressure tank cleaning systems comprising high pressure wash heads require cleaning liquids of high purity with respect to particulate contaminants in order for the pressure building mechanism to function properly and in order to avoid particulate blockage of liquid conduits and injection nozzles. Consequently, such cleaning systems require either fresh cleaning liquid or highly efficient and costly separation means for purifying the cleaning liquid before recirculation to the wash heads.

Therefore, there is a need for an improved tank cleaning system using a cleaning liquid which cleaning system does not require high pressure and costly cleaning liquid purification means.

Prior Art Disclosures

GB-A-2 166 043 discloses a tank cleaning system for high pressure cleaning of tanks in ships or railroad cars, the system comprising a vessel for a cleaning liquid, a vacuum pump for producing a vacuum in a region of the cleaning liquid vessel, a pump for pumping cleaning liquid to a wash head in a tank to be cleaned, in a preferred embodiment at about 690 bar (10 000 psi) a suction line for removing dirty liquid containing contaminants from the tank to the cleaning liquid vessel, means for separating the cleaning liquid from the dirty liquid containing contaminants and recirculation of the separated cleaning liquid for reuse thereof.

US 5 085 242 discloses a process for mobilization and removal of black residue from an enclosed tank comprising heating at least a portion of the black oil residue by heating means located inside of the tank, said heating means being supplied by a source of heat for direct heating by steam, water, oil or electrical energy. The mobilized residue is withdrawn separate from the heating medium. A separate cleaning liquid is neither indicated nor suggested.

2. DISCLOSURE OF THE INVENTION

Object of the Invention

It is an object of the present invention to seek to provide improved method and apparatus for inside cleaning of containers to be cleaned for gasses, liquids, solids, or residues thereof by using a cleaning liquid which is different there from, and which method and apparatus do not require high pressure and costly cleaning liquid purification means.

In particular, it is an object of the present invention to seek to provide such an improved method and apparatus for inside cleaning of containers containing gasses, liquids, solids, or residues thereof which are immiscible with the cleaning liquid.

It is still another object of the present invention to seek to provide such an improved method and apparatus for inside cleaning of containers under improved conditions and of reduced health risks to cleaning personnel.

Further objects appear from the description elsewhere.

Solution According to the Invention

Method

According to an aspect of the present invention, providing a method as defined in claim 1 fulfills these objects. It has surprisingly turned out that for inside cleaning of a container, introduction of said cleaning liquid into the inside of the container without atomization of the cleaning liquid, the required pressure on the liquid injection means can be kept low thereby allowing use of low pressure injection means, and further allowing use of injection means which do not require costly fine solid particle separation means for purifying the cleaning liquid to be pressurized in prior art high pressure injection means to a degree of purity which avoids particulates in blocking the high pressure injection nozzles. Thereby the overall costs can be reduced.

Preferred embodiments are defined in the sub claims

Introducing cleaning liquid inside the container

Generally, cleaning liquid is introduced into the inside of the container under pressure conditions including pressure below 25 bars which ensures an effective application of liquid onto the interior of the container without producing atomization of the cleaning liquid.

In contrast to high pressure cleaning liquid systems according to the prior art, and under pressure conditions according to the present invention, effective cleaning is obtained over longer distances of the introduced cleaning liquid because the pressure of the cleaning liquid does not provide atomization before impact on the target, e.g. inner walls of the container or auxiliary equipment contained therein.

According to the present invention, however, the pressure of the cleaning liquid is kept below 25 bars reducing atomization of the liquid thereby allowing use of low- pressure injection means. The amount of cleaning liquid can then be adjusted, usually by increasing the amount of introduced cleaning liquid, to provide an effective cleaning effect on the interior of the container.

Generally, the pressure is kept below 25 bar whereby effectively cleaning is obtained. Preferably, the pressure of the cleaning liquid is in the range 5 to 15 bars, in particular in the range 8 to 12 bars.

Typically, an effective cleaning distance of the pressurized cleaning liquid is in the range 5 to 10 meter, preferably 10 to 30 meter, in particular 20 to 30 meters .

Generally, the amount of cleaning liquid introduced is adjusted according to the selected injection means which adjustment ensures that the required pressures and cleaning distances for effective cleaning are obtained.

Typically, larger amount of cleaning liquids are applied than for high pressure cleaning systems according to the prior art

In a preferred embodiment the amount of cleaning liquid introduced is in the range from 10 to 100 itr/h, preferably in the range from 40 to 80 mVh, in particular about 60 mVh.

In a preferred embodiment, cleaning liquid is introduced into the inside of the container to be cleaned through suitable injections means whereby the direction and hydraulic properties of the injected cleaning liquid can be controlled. Preferably, the cleaning liquid is introduced through rotary injecting nozzles, e.g. beam jet injecting nozzles or flat jet injecting nozzles, onto the inner walls of the container, or auxiliary equipment, respectively. Rotary injecting nozzles are known in the art and provide particularly useful washing patterns.

Generally, the cleaning liquid is selected to be a liquid which is able to carry, either in dissolved or dispersed form, the gasses, liquid, solids, or residues thereof from the container and outside the container.

In a preferred embodiment, said cleaning liquid comprises a solvent for said gasses, liquids, solids, or residues thereof contained in the container to be cleaned whereby e.g. salt scaling can be removed, or e.g. paraffin residues can be removed by gas oils.

In another preferred embodiment, said cleaning liquid comprises an immiscible liquid for said gasses, liquids, solids, or residues thereof contained in the container to be cleaned, e.g. using water as cleaning liquid to remove hydrocarbons .

The cleaning liquid can comprise any suitable auxiliary agent useful for its purpose, i.e. additives providing certain desired properties to the cleaning liquid, e.g. surfactants for dispersing solid particulates.

Accordingly, in a preferred embodiment, said cleaning liquid comprises a surfactant, e.g. a detergent for degreasing purposes. The cleaning liquid can be any liquid suitable for its cleaning purpose and suitable for its handling with respect to risk to health and environment.

In a preferred embodiment, said cleaning liquid comprises water; water being well known for its properties as cleaning liquid, e.g. as an immiscible liquid with oil, heat-carrying medium, and non-hazardous to the environment .

Accordingly, in a preferred embodiment depending on the application, the cleaning liquid is selected among cleaning liquids that are immiscible with the gasses, liquids, solids, and residues present in the container, e.g. with the purpose of later separation in a coalescer.

The container may contain auxiliary equipment e.g. propellers, baffles, distributors, various conduits for liquids and gasses, heating coils, etc. to be cleaned. Consequently, the introduced cleaning liquid can be applied onto such equipment as well.

Withdrawing said spent cleaning liquid from the container

Generally, spent cleaning liquid is withdrawn from the container to be cleaned in any suitable way.

In a preferred embodiment, a vacuum is applied at the location of the spent cleaning liquid to be withdrawn, e.g. at the bottom of the container.

Optionally, the withdrawn spent cleaning liquid is filtered through suitable filter means for e.g. removing coarse particles and foreign bodies. Collecting said spent cleaning liguid

Generally, spent cleaning liquid is collected in any suitable way in a container for spent liquid, said spent cleaning liquid comprising said cleaning liquid applied to the inner surfaces of the container, wholly or partially, having dislodged said liquids, solids, or residues there from and carrying said dislodged liquids, solids, or residues thereof.

In a preferred embodiment, said collection of said spent cleaning liquid is outside the container to be cleaned.

Separation of cleaning liquid from spent cleaning liquid

Generally, cleaning liquid is separated from said collected, spent cleaning liquid from the container to be cleaned in any suitable way.

In a preferred embodiment, separation of said cleaning liquid from said collected, spent cleaning liquid from the container comprises separating immiscible liquids by a coalescence means.

A preferred coalescence means comprises a separator means for separating immiscible liquids, e.g. an oil-water separator containing horizontal coalescensing plates that are assembled into a compact modular pack or packs whereby oil-water separation can be obtained by gravity without any moving parts.

Other oil-water separation means can be used based on e.g. sedimentation or flocculation, or floatation. Recirculation of separated cleaning liquid

Generally, separated cleaning liquid is recirculated into the inside of the container to be cleaned whereby the spent cleaning liquid is reused and waste thereof can be avoided or reduced, which is useful when large amount s of cleaning liquid is used.

Preferably, recirculation of separated cleaning liquid is done by simple introduction of the separated cleaning liquid into the cleaning container, whereby existing conduits can be used.

In another embodiment, recirculation of separated cleaning liquid is done by simple introduction of the separated cleaning liquid into the cleaning container through separate conduits.

Further embodiments

In still another embodiment, the cleaning liquid is heated before it is introduced into the container whereby higher solubilities or melting of the liquids or solids to be removed can be obtained in the cleaning liquid.

In still another embodiment, said separation of said cleaning liquid from said collected, spent clea,ning liquid from the container comprises separating immiscible liquids by a coalescence means whereby a simplified and cost effective separation can be obtained.

In some applications, the container to be cleaned contains hazardous gasses such as explosive gasses or liquid with low flash points . In a preferred embodiment, the cleaning steps are preceded by an inertiation step whereby it is ensured that effects of the hazardous gasses are neutralised. E.g. a tank containing an explosive liquid having a low flash point, the tank is flushed with an inert gas, e.g. nitrogen, to ensure oxygen content below a certain level, e.g. 8% oxygen, thereby avoiding explosive conditions.

Accordingly, in a preferred embodiment, said inertiation step comprises flushing nitrogen gas through the container.

Apparatus

According to another aspect of the present invention, providing an apparatus as defined in claim 12 fulfills these objects.

In a preferred embodiment, said introduction means comprising means for applying said cleaning liquid to the inner walls of the container, and optionally applying to auxiliary equipment contained therein.

In a preferred ^' embodiment, the apparatus further comprising a vacuum pump means for driving said withdrawal of said collected spent cleaning liquid, and optionally for driving said cleaning liquid for introduction into the inside of the container whereby it is ensured that all surfaces are exposed to the cleaning liquid.

In another preferred embodiment, the apparatus further comprising cleaning liquid pump means for driving said cleaning liquid for introduction into the inside of the container whereby the cleaning effect is improved by using rotary jet heads with high impact on long distances .

In another preferred embodiment, the apparatus further comprising a heat exchanger for heating said cleaning liquid before said introduction into the inside of the container whereby it is obtained that the temperature of the liquids, solids and residues to be cleaned off the interior of the container to be cleaned is elevated, thereby melting off some solids and increasing floatability of the liquids and improving cleaning properties. Of course, the cleaning temperature should not be raised too must to course decomposition and undesired deposition of decomposition products instead of removal thereof.

In still another embodiment, the apparatus further comprising coalescence means for separating immiscible liquids by coalescence of the respective liquids.

In a particularly preferred embodiment, the apparatus comprises said cleaning liquid container and said spent cleaning liquid collecting container accommodated in a single container with a partition means there between whereby a particular compact container system of the two can be obtained.

In a preferred embodiment, said partition means is movable within said single container thereby allowing adjustment of the available volumes of the collecting container and the cleaning liquid container.

In a preferred embodiment, said partition means comprises said separation means, whereby a particularly preferred introduction of separated cleaning liquid in to the cleaning liquid container can be obtained.

In a preferred embodiment, said spent cleaning liquid collecting container comprises means for discharging solids .

In a preferred embodiment, the end-part of the collecting container can be opened for discharging solids. In particular, the partition means can further function as a piston pushing out solids through the opened end-part of the collecting container.

3. BRIEF DESCRIPTION OF THE DRAWINGS

In the following, by way of examples only, the invention is further disclosed with detailed description of preferred embodiments. Reference is made to the drawings in which

Fig. 1 shows a sketch of an embodiment of the present invention illustrating an exemplary mobile apparatus for inside cleaning a tank containing liquids, solids, and residues thereof.

4. DETAILED DESCRIPTION

Fig. 1 shows a sketch of an embodiment of the present invention illustrating an apparatus for inside cleaning a tank containing liquids, solids, and residues thereof.

As an exemplary illustration, it is indicated that the embodiment of the apparatus is a mobile apparatus. The apparatus, however, can be stationary. A cleaning container 7b, here the one chamber of a two chamber tank 7a, 7b, contains a cleaning liquid 10. The cleaning container is connected to a media pump, here a positive displacement pump supplied by Vogelsang A/S, Denmark, which media pump is further connected via conduit 14 to inlet means for the cleaning liquid into the container 11, through an heat exchanger 3, e.g. a Tetra Spiraflo CIP heater type CIP 4 from Alfa Laval supplied by Alfa Laval A/S, Denmark. The cleaning liquid container is further connected to a vacuum pump means 4a, 4b, e.g. a Wittig RFW 2000 from Mannesmann De ag, through a flow reduction means 15b.

Spent liquid 12, e.g. an oil residue and/or cleaning liquid containing oil residues and other contaminants, is contained in the bottom, of a container 11, here a tank or vessel, or is adsorbed onto the walls and/or auxiliary equipment (not shown) for used under operation thereof. The container comprises an outlet means, here a discharge conduit 13a communicating liquid from the bottom of the container to a filtering means 1, here e.g. a prefilter of the type HL3-13263 supplied by J. Hvidtved Larsen A/S, Silkeborg, Denmark, outside the container. The container further comprises inlet means, here an inlet conduit 14 connected to injections means, here rotary injecting nozzles 6 that can be vertically moved to obtain a given height in the container, preferably the rotary injection nozzles consists of beam jet injecting nozzles, flat jet injecting nozzles, or a combination thereof. Toftejorg, Ishoj, Denmark, supplies rotary injecting nozzles of both the beam jet and the flat jet types.

The container to be cleaned is otherwise kept closed and sufficiently tight with a minimum of false gas inlet, typically air from the surroundings, when operated under vacuum conditions .

The filtering means 1 are connected to a collecting container 7a of spent cleaning liquid, here a vacuum tank operated under vacuum to provide a driving effect to remove liquid from the container 11. Here, the withdrawn liquid is transported through a filter means; however, depending on the application, this filter means may not be required. The vacuum tank is communicating with a vacuum pump means 4a, 4b through a flow reduction means 15a, here e.g. an on/off butterfly valve/actuator produced by Alfa Laval/Revo and supplied by Klinger Denmark A/S .

The collecting container of spent cleaning liquid is further connected to separation means 5a, 5b, 5c for separating the cleaning liquid from the collected spent cleaning liquid, here illustrated by a coalescence filter 5c, e.g. a Mpak Separator produced by Facet International and supplied by Bech & Co., Denmark, connected to the collecting container by a flow reduction means, here an on/off butterfly valve/actuator of the above-mentioned type. The separation means are further in communication with the cleaning liquid container 7b providing separated cleaning liquid from the separation means to the original cleaning liquid 10, and an separated phase of an immiscible liquid 9 on the top thereof. In a particularly preferred embodiment, the collection container 7a of spent cleaning liquid and the cleaning liquid container 7B are separated chambers of a common container, here a tank separated by a movable separation means 5.

The vacuum pump means 4a, 4b comprises a cyclone for removing solid and liquid particles, which cyclone is connected to a vacuum pump of the RFW type from Gardner Denver Wittig GmbH supplied by J. Hvidtved Larsen A/S, Silkeborg, Denmark.

Claims

METHOD AND APPARATUS FOR INSIDE CLEANING OF CONTAINERSCLAIMS

1. A method of inside cleaning of a container (11) to be cleaned for gasses, liquids (12), solids (12b), or residues (12c) present therein, the method comprising:

(a) providing a cleaning liquid (10) in a cleaning liquid container (7b) , said cleaning liquid being different from the liquids, solids, or residues present in the container to be cleaned;

(b) introducing said cleaning liquid into the inside of the container at a pressure below 25 bar; said introduced cleaning liquid being directed onto inner walls of the container to be cleaned, and optionally onto auxiliary equipment contained therein;

(c) withdrawing said introduced cleaning liquid from the container;

(d) collecting said withdrawn cleaning liquid in a spent liquid container (7a) , said spent cleaning liquid comprising said applied cleaning liquid, wholly or partially, having dislodged said liquids, solids, or residues thereof contained in the container to be cleaned, and carrying said dislodged liquids, solids, or residues thereof;

(e) separating said cleaning liquid from said collected, spent cleaning liquid from the container to be cleaned; and (f) recirculating said separated cleaning liquid into the inside of the container to be cleaned.

2. The method according to claim 1 wherein said cleaning liquid is introduced into the inside of the container to be cleaned through suitable injections means (6) , preferably through rotary injecting nozzles.

3. The method according to claims 1 or 2 wherein said collection of said spent cleaning liquid is outside the container to be cleaned.

4. The method according to any one of the preceding claims 1-3 wherein said cleaning liquid comprises a solvent for said liquids, solids, or residues thereof contained in the container to be cleaned.

5. The method according to any one of the preceding claims 1-3 wherein said cleaning liquid comprises an immiscible liquid for said liquids, solids, or residues thereof contained in the container to be cleaned.

6. The method according to any one of the preceding claims 1-5 wherein said cleaning liquid comprises a surfactant.

7. The method according to any one of the preceding claims 1-6 wherein said cleaning liquid comprises water.

8. The method according to any one of the preceding claims 1-7 wherein said liquids, solids, or residues thereof contained in the container are immiscible with said cleaning liquid.

9. The method according to any one of the preceding claims 1-8 wherein said separation of said cleaning liquid from said collected, spent cleaning liquid from the container comprises separating immiscible liquids by a coalescence means.

10. The method according to any one of the preceding claims 1-9 wherein the cleaning steps are preceded by an inertiation step.

11. The method according to claim 10 wherein said inertiation step comprises flushing nitrogen gas through the container.

12. An apparatus for inside cleaning of a container (11) to be cleaned for gasses, liquids (12), solids (12b), or residues (12c) present therein, the apparatus comprising:

(a) a cleaning liquid container (7b) for containing a cleaning liquid, in operation, said cleaning liquid being different from the liquids, solids, or residues present in the container to be cleaned;

(b) a cleaning liquid inlet means (6) for introducing said cleaning liquid into the inside of the container to be cleaned, said cleaning liquid inlet means being connected to said cleaning liquid container, and said cleaning liquid being introduced into the inside of the container at a pressure below 25 bars; said cleaning liquid inlet means being adapted to direct said cleaning liquid onto inner walls of the container to be cleaned, and optionally onto auxiliary equipment contained therein; (c) a spent cleaning liquid collecting container (7a) for collecting said introduced cleaning liquid from the inside of the container to be cleaned, said collecting means being connected to said container to be cleaned to allow, in operation, withdrawal of said collected spent cleaning liquid, said collected spent cleaning liquid, in operation, carrying, wholly or partially, dislodged liquids, solids, or residues thereof;

(e) separating means (5a) for separating said cleaning liquid from said collected spent cleaning liquid cleaning liquid from said withdrawn collected, spent cleaning liquid from the container to be cleaned; said separating means being connected to said a spent cleaning liquid collecting container (7a) for receiving said spent cleaning liquid, and being connected to said cleaning liquid container (7b) for returning separated cleaning liquid thereto, and optionally being connected to said cleaning liquid inlet means (6) for introducing said separated cleaning liquid directly into the container to be cleaned; and

(f) recirculating means for recirculating said separated cleaning liquid into the inside of the container.

13. The apparatus according to claim 12 wherein said introduction means comprising means for applying said cleaning liquid to the inner walls of the container, and optionally applying to auxiliary equipment contained therein.

14. The apparatus according to any of the preceding claims 12-13 further comprising a vacuum pump means (4) for driving said withdrawal of said collected spent cleaning liquid, and optionally for driving said cleaning liquid for introduction into the inside of the container.

15. The apparatus according to any of the preceding claims 12-14 further comprising cleaning liquid pump means (2) for driving said cleaning liquid for introduction into the inside of the container.

16. The apparatus according to any of the preceding claims 12-15 further comprising a heat exchanger (3) for heating said cleaning liquid before said introduction into the inside of the container.

17. The apparatus according to any of the preceding claims 12-16 further comprising coalescence means for separating immiscible liquids by coalescence of the respective liquids.

18. The apparatus according to any of the preceding claims 12-17 wherein said cleaning liquid container (7a) and said spent cleaning liquid collecting container (7b) are accommodated in a single container with a partition means (5) .

19. The apparatus according to claim 18 wherein said partition means is movable with said single container.

20. The apparatus according to claims 18 or 19 wherein said partition means (5) comprises said separation means

(5a) .

21. The apparatus according to any of the preceding claims 12-20 wherein said spent cleaning liquid collecting container (7a) comprises means for discharging solids .

22. A method for inside cleaning of a container (11) to be cleaned for gasses, liquids (12), solids (12b), or residues (12c) present therein, the method comprising:

(a) providing a cleaning liquid (10) different from the liquids, solids, or residues present in the container to be cleaned;

(b) introducing said cleaning liquid into the inside of the container at a pressure below 25 bars;

(c) withdrawing said introduced cleaning liquid from the container;

(d) collecting said withdrawn cleaning liquid in a spent liquid container (7a) ;

(e) separating said cleaning liquid from said collected, spent cleaning liquid from the container to be cleaned; and

(f) recirculating said separated cleaning liquid into the inside of the container to be cleaned.