GB2424653A

GB2424653A - A method of reducing atmospheric contamination

Info

Publication number: GB2424653A
Application number: GB0606336A
Authority: GB
Inventors: David Malcolm Owen; Clement Cyril Armitage
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-04-01
Filing date: 2006-03-30
Publication date: 2006-10-04
Also published as: GB0506627D0; GB0606336D0

Abstract

A method of reducing atmospheric contamination by solvent or other volatile substances in the removal of solvent or other voltatile substances from wipes or like cloths by washing, comprises first immersing the wipes in cold water to reduce emissions of volatile materials, with or without the aid of surfactant to emulsify the solvents into the water phase, and washing, such as by counter-current washing, the wipes to remove the solvent content.

Description

A METHOD OF REDUCING ATMOSPHERIC CONTAMINATION

The present invention relates to a method of reducing atmospheric contamination by volatile organic compounds in the removal of solvent or other volatile substances from industrial wipers or cloths by washing.

Provision of industrial wipers, wipes or cleaning cloths are a recognized service product for industry. In the UK several companies are engaged in supplying textile cloths (wipes/wipers) to various industries for the purpose of on-site cleaning of machinery etc. A particularly common application is the supply of wipes to the printing trade where large volumes of solvents are used in the press rooms to clean the printing apparatus. The wipes after use are heavily contaminated with solvents, usually white spirit or toluene and ink pigments and general soils associated with the press room activities.

The wipes are collected and sent to industrial laundries who wash them clean in hot water and ready for reuse.

The problems associated with this recycling of the wipes are as follows: * The solvent burden of the wipes may be greater than 1 5O i of the cloth weight.

* The washing process is a hot wash program and results in large quantities of volatile organic components being volatilised into the atmosphere of the plant.

* The waste water from the washing process is alkaline and contains large quantities of solvent and needs substantial treatment with inorganic coagulants to remove both the soil and the solvent.

* The sludge from the treatment is heavily contaminated with hydrocarbon solvents which makes it difficult to dispose of to landfill under the latest legislation.

The problem may be solved by not allowing the solvent proportion to enter the hot wash cycles as presently operated.

It is object of the invention to provide a method of solvent removal applicable to industrial laundries which minimizes or reduces escape of solvent into the atmosphere and which is both simple to operate and falls within the normal operations of the laundry.

According to the present invention there is provided a method of reducing atmospheric contamination by solvent or other volatile substances in the removal of solvent or other volatile substances from wipes or like cloths by washing, comprises carrying out at least one first washing of the wipes in cold water such that solvent enters the water, and carrying out at least one second, subsequent washing of the wipes, and the second and subsequent washing of the wipes may be in cold or hot water and normally the water is other than the water used for the first washing process.

Preferably a surfactant is added to the cold or unheated water of the first washing.

Thus the method comprises immersing the wipes into cold water of temperatures of preferably e.g. less than about 25 C, to reduce emissions of volatile materials into the atmosphere as would occur with hot washing and may be carried only, with or without the aid of surfactant to emulsify the solvents into the water phase. The water may simply comprise water from the cold tap or the normal mains water supply or other cold water supply. If desired, the water of the first process may be cooled or refrigerated. The wipes are then counter-current washed in cold water preferably in known apparatus as used for the purpose of hot washes, to remove the solvent content (An open system of once through water usage may be considered but is not advisable, given water conservation constraints). The initial washing is not for soil removal but rather primarily for solvent emulsification to reduce or minimize the contamination of the ambient atmosphere by the volatile material. Surfactant systems are available which are more emulsifying than detergent. Such a desirable surfactant product is Treatchem Vocontrol 03 a blended non-ionic surfactant designed to emulsify solvents in water.

Unlike normal soils, the solvent content is high and builds-up rapidly in the system as the water is reused, It is therefore important to have inter-stage or intermediate stage separation of the solvent from the water prior to each theoretical reuse of the water.

The wipes both during the inter-stage (i.e. in intermediate stage between washing cycles) and at the end of the process, are preferably wrung and/or spun, and at the final stage will be substantially solvent free. The water in the damp wipes constitutes a loss from the system.

The wet/damp cloths subsequent to the cold wash are preferably conventionally washed in hot water in normal alkaline surfactant systems (detergent) at temperatures of e.g. in the region of 60 to 80 C. This will produce a much more readily treatable waste with little or no solvent content and of much reduced volume. However, the second washing process may be carried out as a cold wash and advantages still achieved such as in that detergents may be used which would be less effective if the water of the first washing process were used because of the heavy load of solvent and/or surfactant in the first water which, if removed, might be otherwise used.

The whole process is desirably performed in a small self-contained unit such as a front loader with spin drying (extraction) facility. The wash may be placed in a building or container fitted with air extraction and air treatment such as a biobox wherein a wetted matrix of wood chips or peat is contacted with the exit air and significant reductions in the solvent content is observed.

Solvent is preferably recovered from the washing process by decanting to storage or by using activated carbon filters.

The method according to the invention enables recycling of solvent/oil contaminated cloths which have been used as industrial wipes such that there is little or no impact on VOC in the normal washing operations associated with removing non volatile contaminants.

The method comprises removing the solvent by a method of cold washing by emulsification prior to hot washing to remove soil.

In a preferred embodiment according to the invention, the method comprises admitting cloths contaminated with solvents and other into a washing device that is filled with cold water at a percentage commensurate with good washing practice, usually from 0.1% to 20% cloth weight on water used.

Surfactant is added such that emulsification of the solvent is observed. (It is possible that surfactant may not be necessary at times). However, it is preferable to introduce surfactant to the first wash loop, ideally without affecting pH or water chemistry. The surfactant is non-ionic in the embodiment example, although any kind may be used such that emulsification takes place. The water emulsion is then removed by draining the system and wringing or spin drying the wipes. The water so removed is treated with a coagulating chemical, if necessary, to remove the solvent from the water by floatation such that the recovered water may be reused.

The process is repeated several times to obtain a quality of cloth that is suitable for washing subsequently with detergent.

The normal number of stages is four wash and wring cycles. However, practice will determine the number of cycles required.

It is not necessary to have specific cleaning cycles as the process may be set up with continuous washing and cleaning out of the solvent through cleaning loops.

The recovered solvent is preferably subsequently recovered and reused as appropriate and the solid burden from the hot was filtered out and sent to landfill.

Subsequent to the first washing process or processes, the wipes are washed in the second washing process in water other than was used for the first washing process and which may be cold or hot and detergent may be added. Subsequently the water is drained and the wipes spun and/or wrung.

Claims

1. A method of reducing atmospheric contamination by solvent or other volatile substances in the removal of solvent or other volatile substances from wipes or like cloths by washing, comprises carrying out at least one first washing of the wipes in cold water such that solvent enters the water, and carrying out at least one second, subsequent washing of the wipes.

2. A method as claimed in claim 1, in which a surfactant is added to the cold or unheated water.

3. A method as claimed in claim 1 or 2, in which the wipes are immersed in cold water and agitated to reduce the emissions of volatile materials, as would otherwise occur, in the second subsequent washing in hot water.

4. A method as claimed in any of claims 1 to 3, in which the wipes are counter-current washed in at least the first cold washing to remove solvent.

5. A method as claimed in any of claims 1 to 4, in which the initial cold washing is carried out to effect solvent emulsification.

6. A method as claimed in any of claims 1 to 5, in which a blended nonionic surfactant (such as Treatchem Vocontrol 03) is included in the cold wash.

7. A method as claimed in any of claims 1 to 6, in which at least the cold wash water is re-used for first washing processes.

8. A method as claimed in any of claims 1 to 6, in which inter-stage or between the first and second washing processes, separation of solvent from the water is effected prior to each re-use or the theoretical re-use in the first washing.

9. A method as claimed in any of claims 1 to 8, in which the wipes are spun and/or wrung during the inter-stage after the cold washing and/or at the end of the second washing process.

10. A method as claimed in any of claims I to 9, in which after the first cold washing the wet/damp wipes or cloths are conventionally washed in hot or cold water.

11. A method as claimed in any of claims 1 to 10, in which a normal alkaline surfactant system (detergent) is used in the second washing.

12. A method as claimed in any of claims ito 11, in which the washing processes are carried out in a self-contained unit such as a front loader.

13. A method as claimed in any of claims 1 to 8, in which the water for at least the cold first washing is such as comes from the cold mains supply or other cold water store at a temperature of less than 25 C.

14. A method as claimed in any of claims ito 13, in which the second and subsequent washing of the wipes is carried out in water which is other than the water used in the first washing.

15. A method of reducing atmospheric contamination by solvent or other volatile substances in the removal of solvent or other volatile substances from wipes or like cloths by washing, comprises first immersing the wipes in cold water to reduce emissions of volatile materials, with or without the aid of surfactant to emulsify the solvents into the water phase, and washing, such as by counter-current washing, the wipes to remove the solvent content.

16. A method as claimed in claim 15, in which in counter-current washing of the wipes, inter-stage separation of the solvent from the water is effected prior to each theoretical reuse of the water.

17. A method as claimed in claim 15 or 16, in which the wipes are wrung and/or spun both during the inter-stages and at the end of the first process prior to conventionally hot washing the wipes in a normal alkaline surfactant system (detergent).

18. A method as claimed in any of claims 15 to 17, in which the whole process is performed in a small self-contained unit (such as a front loader with spin drying (extraction) facility).

19. A method as claimed in claim 18, in which the whole unit is placed in a building or container fitted with air extraction and air treatment.

20. A method as claimed in claim 19, in which in the air extraction there is used a biobox wherein a wetted matrix of wood chips or peat is contacted with the exit air.

21. A method as claimed in claim 19, wherein extracted air is passed through activated carbon.

22. A wipe whenever produced according to the method of any of claims to 21.

23. A wiper or like cloth whenever cleaned/washed according to the method of at least claim 1.