WO2004101186A1

WO2004101186A1 - Receptacle and methods of decontamination using said receptacle

Info

Publication number: WO2004101186A1
Application number: PCT/GB2004/002126
Authority: WO
Inventors: David Grouse; Paul Theile
Original assignee: Mel Limited
Priority date: 2003-05-17
Filing date: 2004-05-17
Publication date: 2004-11-25
Also published as: EP1633503A1; GB0311421D0

Abstract

The invention relates to a receptacle (1) suitable for containing a contaminated material, and methods of decontamination using said receptacle (1), particularly soil decontamination and methods of use thereof. The receptacle (1) comprises heating means (9), outlet means (12a, 12b) and means (8) to guide contaminants to an outlet.

Description

RECEPTACLE AND METHODS OF DECONTAMINATION USING SAID RECEPTACLE

Field of the invention

The invention relates to a receptacle suitable for containing a contaminated material, and methods of decontamination using said receptacle, particularly soil decontamination and methods of use thereof.

Background to the invention

The most common soil contaminants are petroleum-based, such as hydrocarbons derived from diesel fuel and gasoline. Polyaromatic hydrocarbons (PAHs) are considered to be particularly hazardous to the environment and also to human health, as they are known carcinogens.

Soil contamination, particularly with hydrocarbons, is poses a serious problem in areas adjacent to coking works. These works in addition to manufacturing coke also process carbonisation by-products such as sulphuric acid, ammonium sulphate, benzene, toluene, xylene, naphthalene and numerous other acids and organic compounds. The contaminants generally comprise coal tars, lime sludges, acids, polyaromatic hydrocarbons, volatile organic compounds, spent oxides, ammoniacal wastes, asbestos and heavy metals. The extent of the pollution from these coke works is widespread, with contamination being found within lagoons, waste tips, sites soils, surface and groundwater and above and below ground storage tanks and sumps.

Low Temperature Thermal Desorbtion (LTTD) is a known alternative to the use of chemicals in soil decontamination. LTTD is widely recognised as being a low cost, safe and proficient technology.

A prior art example of applying LTTD technology in-situ requires a system which comprises layered cells into which contaminated soil is placed. The system has to be constructed at the point of use. Burners, either catalytic or thermal oxidisers deliver heated air through a system of inter-laced perforated pipes and manifolds laid within the soil pile. The soil is heated over a period of 4-10 days, depending on the level and type of contamination and the required clean-up criteria. During this time contaminants are volatilised and migrate to a low-pressure area between the soil pile and a steel cover. The volatilised contaminants are then drawn into a vapour treatment system under vacuum and destroyed prior to discharge to the atmosphere. On completion of the process, rehydration of the soil is achieved by the use of a simple sprinkler system connected to the domestic water supply.

There is however a need for a system for decontaminating soil using LTTD technology which overcomes at least some of the disadvantages of the prior art system.

Statement of the invention

Thus according to an aspect of the invention a receptacle is provided suitable for receiving a contaminated material, the receptacle comprising a means to heat said material, at least one outlet to facilitate the exit of a at least one contaminant from said receptacle characterised in that said receptacle comprises a means to guide said contaminant to an outlet.

The provision of a means to guide a contaminant to an outlet of the receptacle increases the efficiency of the removal of a contaminant from the material. Preferably said means to guide is at least one channel. Even more preferably the receptacle comprises an internal wall that divides the receptacle into a receiving chamber which receives the contaminated material and at least one channel for guiding a contaminant to an appropriate outlet.

In a further preferred embodiment of the invention the contaminated material can be placed in inserts, for example, trays or baskets which are stacked or racked within the receiving chamber. The trays or baskets can be free stacking, ie. on top of each other, or can be slid into a pre assembled grid within the receiving chamber. There are a number of advantages associated with the use of trays or baskets, it maximises the surface area around the sludge like materials and speeds up the heating process. It also aids the removal or drainage of liquids within the materials to be treated. It also allows the heated air to flow around the materials in both a horizontal and vertical direction. It provides a more efficient materials handling process both pre- and post- treatment

The contaminant can be transported from the receiving chamber to a channel by the provision of a plurality of perforations on the internal wall. The channel may either extend vertically in order to guide a fluid in a vertical direction and/or extend horizontally in order to guide a contaminant in a horizontal direction. Even more preferably at least one vertical and at least one horizontal channel are connected. At least one vertical channel is preferably adjacent to a side wall and at least one horizontal channel is preferably adjacent to the lid or the base of the receptacle.

Even more preferably still the contaminant is at least partially in a fluid phase upon exit from the receptacle. The contaminant may exit the receptacle as a component of a liquid phase or alternatively as volatilised component of a gas phase.

The contaminant may be in solution or in suspension within the liquid phase. Particularly when treating sludges there may be a considerable liquid component which requires separate treatment. Preferably therefore a liquid comprising a contaminant can be transported from the contaminated material in the receiving chamber through the perforations on an inner wall to a horizontal channel positioned adjacent to the base which guides the liquid to a liquid outlet. The liquid is then further treated.

This gas can be transported from the contaminated material in the receiving chamber through the perforations on an inner wall to a vertical channel positioned adjacent to a side wall. This channel may extend along the entire height and width of a side wall and its function is to guide the gas in a vertical direction. Furthermore this vertical channel may connect with horizontal channel adjacent to the lid of the receptacle, which guides the gas to a gas outlet. The off-gas is then further treated.

In order to achieve efficient volatilisation, particularly of the hydrocarbon and PAH contaminants, the material is heated to approximately 500°C. The source of this heat is generally a catalytic oxidiser. Due to the compact nature and non-conductive properties of for example soil, the transfer of heat from the heat source throughout the soil is conventionally a somewhat inefficient process, taking a prolonged period of time and having high fuel consumption rates. However, using the receptacle of the present invention, homogenous and efficient heating of the material throughout the receptacle can be achieved by the provision of heating elements throughout the receptacle.

In a further embodiment of the invention a receptacle is provided which comprises one or more heating elements which extend substantially perpendicular relative to the receptacle's base. These vertical pipes are more efficient at transferring heat than horizontal pipes, as they require less air volume pressure to pump a heated gas through the pipes. Preferably these heating elements comprise at least one channel through which a heated fluid can pass. Even more preferably the channel is perforated to enable passage of the heated fluid out of the channel and into the contaminated material. Preferably the heated fluid is a heated gas, for example hot air which has been heated by an external heating source such as a catalytic oxidiser. Alternatively the heated fluid is a liquid, such as hot water. Alternatively the heating elements may be electric heating elements positioned throughout the receptacle.

hi a still further preferred embodiment of the invention the receptacle comprises thermal insulation. Even more preferably, when in use, the receptacle stands on a base with the walls of the receptacle comprising the thermal insulation.

Due to the need for the material to be heated to approximately 500°C, the provision of thermal insulation has a number of significant advantages. Firstly, the reduction of heat loss by conduction through the metal walls will increase the overall efficiency of the heating process and thus have the effect of reducing fuel consumption. Secondly, the provision of thermal insulation has important safety implications and enables the receptacle to be left unmanned for periods of time without the potential risk of injury to individuals.

The preferred insulation means is for the walls of the receptacle to be lined with Rocksil ® available from Owens-Corning Building Products, UK. In a further preferred embodiment of the invention the receptacle comprises a rehydration system.

During the decontamination process the heating of the material results in its dehydration. If, for example, soil is to be re-introduced into the site and support fauna and flora it will require rehydration. Whilst it is possible to simply rehydrate the soil using hose-pipes connected to the domestic water supply, it would be preferable to rehydrate the soil prior to it being released from the receptacle. This would be particularly advantageous as it would prevent the soil, in an ash-like form, being blown away from the site.

The rehydration system is preferably an integral sprinkler system. More preferably still the receptacle comprises one or more water distributing elements which extend substantially perpendicular relative to the base of the receptacle, when it is in use, and wherein these water distributing elements comprise at least one channel having at least one perforation through which water can pass through. This enables an even rehydration of the material throughout the receptacle and will prevent there being any hot spots remaining within the material. Even more preferably still the channels through which water is distributed are the same channels through which heat is distributed.

In a further preferred embodiment of the invention the receptacle comprises a connector to connect at least one fluid outlet to at least one heating element for the recycling of the heated fluid.

The heating of a contaminated material to temperatures in excess of 500°C is a very energy poor system, particularly when the heated fluid, such as a heated gas, is either released to the atmosphere or rapidly cooled down to yield the volatilised contaminants for further processing. Efficiency of the process is therefore dramatically increased by either (i) recycling the hot fluid within the same receptacle during the volatilisation phase or recycling the hot fluid in an in-line process to other receptacles. Preferably the heated fluid is hot air which is recycled within the same receptacle, but alternatively the hot air is recycled to at least one other receptacle. Even more preferably a receptacle connected to a heat source, such as a catalytic oxidiser is connected in-line to a plurality of other receptacles. Even more preferably still hot air is recycled in an in-line process comprising at least five receptacles.

It will be understood to one skilled in the art that the material to be decontaminated in the receptacle may be a semi-solid or solid material which may be selected from the group consisting of soil, sand, shale, sludge or tar.

Preferably the contaminant is a semi-volatile or volatile organic compound selected from the group consisting of hydrocarbons, spent oxides or cyanides. Even more preferably still the contaminant is a polyaromatic hydrocarbon.

Preferably the receptacle of the invention is adapted to be portable. This may be achieved by the provision of wheels.

According to a further aspect of the invention there is provide a system suitable for receiving a contaminated material, the system comprising a receptacle, a means to heat said material, at least one outlet to facilitate the exit of at least one contaminant from said system characterised in that said system comprises a means to guide said contaminant to an outlet, heating elements, thermal insulation and a rehydration system

According to a further aspect of the present invention there is provided a method for guiding at least one contaminant from a contaminated material contained within a receptacle comprising the steps of;

(i) providing a receptacle suitable for receiving a contaminated material (ii) placing contaminated material in the receptacle described in (i); (iii) heating said receptacle to a pre-determined temperature and;

(iv) guiding at least one contaminant to at least one outlet. According to a further aspect of the present invention there is provided a method of recycling the heated fluid used for heating a contaminated material comprising the steps of;

(i) providing a receptacle suitable for receiving a contaminated material (ii) placing contaminated material in the receptacle described in (i);

(iii) heating said receptacle to a pre-determined temperature and; (iv) recycling said heated fluid by connecting at least one outlet a receptacle in (ii).

According to a further aspect of the present invention there is provided a method of decontaminating soil using a receptacle according to the invention.

According to a further aspect there is provided soil whenever decontaminated using a receptacle according the invention.

According to a further aspect there is provided soil whenever decontaminated using a method of the invention

The invention will now be illustrated by way of example only and with reference to the accompanying drawings in which;

Description of the drawings

Figure 1: Illustrates a side view of the receptacle with a side wall cut-away. Figure 2: Illustrates a cross section end view of the receptacle with the front wall cutaway.

Figure 3: Illustrates an end view of the front wall of the receptacle. Figure 4: Illustrates a plan view of the receptacle with the lid removed.

Detailed description of the invention

Referring to the drawings and initially to Figure 1 a side view of the receptacle 1 in which a side wall has been cut-away. The receptacle has four external walls 2a-d; a front wall 2a, a rear wall 2b, and two side walls 2c/2d (not shown in this figure). The receptacle is also provided with a base 3 on which it stands when in use and a lid 4, through which contaminate material enters the receptacle. The lid is designed to create a large void space above the contaminated material for gases to collect. The decontaminated material is removed from the receptacle through the hinged rear wall 2b. The four external walls 2a-d and base 3 are insulated with Rocksil RS60 slab insulation 5.

A further six internal walls 6a-f are provided which are substantially parallel with the exterior walls 2a-d (referred to as 6a-6d) (internal wall 6d is not shown), base 3 (referred to as 6e) and lid 4 (referred to as 6f). These internal walls 6a-f function to divide the receptacle 1 into a central receiving chamber 7 which is surrounded by horizontal guiding channels 8a and vertical guiding channels 8b which facilitate in the guiding of a fluid comprising at least one contaminant to an outlet. The rear wall 2b is a hinged door that allows contaminated material to be placed in the receiving chamber 7.

A plurality of substantially vertical heating elements 9 are positioned within the receiving chamber 7 to facilitate the efficient transfer of hot air throughout the contaminated material from a hot air inlets lOa/lOb (10b is not shown). These hot air inlets lOa lOb are connected to a heating means such as a catalytic oxidizer. Preferably the heating elements 9 are perforated stainless steel columns which are distributed in two parallel rows extending along the base 3. The heating elements 9 may be secured in place by the provision of a securing means, for example bolts or chains or held in a cuff 11 by gravitational forces.

Fluid outlets 12a/12b are shown traversing the front wall of the receptacle. Fluid outlet 12a traverses the upper portion of the front wall and is a gas outlet. Fluid outlet 12b traverses the lower portion of the front wall and is a liquid outlet.

During the heating of the contaminated material to approx. 500°C, certain volatile or semi-volatile contaminants such as PAHs will volatilize into the gas phase. This gas can move horizontally through the contaminated material pass through the perforations in the internal walls to enter a vertical guiding channel 8b. From there the gas is guided into the upper horizontal channel 8a which then guides the gas horizontally towards the gas outlet 12a. Alternatively the gas can escape from the contaminant material by direct upwards movement through the material and directly enter into the upper horizontal channel 8a.

When a contaminated sludge is being treated it is particularly advantageous for the liquid component of the sludge to be separated from the solid component for separate treatment. A lower horizontal guiding channel 8a is provided between an internal wall 6e and the base 3. This internal wall 6e is perforated and this facilitates the transport of the liquid component from the material in the receiving chamber 7 into the horizontal guiding channel 8 a for transport towards the liquid outlet 12b.

The receptacle may provided with wheels 13 which enables it to be portable. These wheels may be adjacent to each of the four corners of the base 3.

Figure 2: Illustrates a cross section end view of the receptacle illustrated in Figure 1 with the front wall cut-away.

Figure 3: Illustrates an end view of the front wall of the receptacle illustrated in Figure 1.

Figure 4: Illustrates a plan view of the receptacle illustrated in Figure 1 with the lid removed.

Claims

1. A receptacle suitable for receiving a contaminated material, the receptacle comprising a means to heat said material, at least one outlet to facilitate the exit of at least one contaminant from said receptacle characterised in that said receptacle comprises a means to guide said contaminant to an outlet.

2. A receptacle according to claim 1, wherein the contaminant is at least partially in a fluid phase upon exit from said receptacle.

3. A receptacle according to claims 1 or 2, wherein the contaminant exits the receptacle as a component of a liquid phase.

4. A receptacle according to claims 1 or 2, wherein the contaminant exits the receptacle as a volatilised component within a gas phase.

5. A receptacle according to claim 1, wherein the means to guide is at least one channel.

6. A receptacle according to claim 5, wherein the receptacle comprises an internal wall which divides the receptacle into a receiving chamber which receives the contaminated material and a channel for guiding said a fluid comprising at least one contaminant to an outlet.

7. A receptacle according to claim 6, wherein the internal wall has a plurality of perforations for the transport of said fluid from the receiving chamber to a channel.

8. A receptacle according to any of claims 5-7, wherein, when in use, the receptacle has a base and the channel for guiding the fluid extends substantially perpendicular in relation to this base.

9. A receptacle according to any of claims 5-7, wherein, when in use, the receptacle has a base and the channel for guiding the fluid extends substantially horizontally in relation to this base.

10. A receptacle according to any of claims 1-9, wherein the means to guide is located adjacent to the base of the receptacle when in use.

11. A receptacle according to any of claims 1-9, wherein the means to guide is located adjacent to at least one side wall.

12. A receptacle according to Claim 1, wherein the receptacle comprises one or more heating elements.

13. A receptacle according to Claim 12, wherein the heating elements extend substantially perpendicular relative to the base.

14. A receptacle according to Claims 12 or 13, wherein the heating elements comprise at least one channel through which a heated fluid can pass.

15. A receptacle according to Claim 14, wherein said channel comprises at least one perforation to enable passage of said heated fluid out of said channel.

16. A receptacle according to any of claims 1 to 15, wherein the receptacle comprises at least one heat distributing element.

17. A receptacle according to claim 16, wherein the heat distributing element comprise at least one channel through which a heated fluid can pass.

18. A receptacle according to claim 17, wherein said channel comprises at least one perforation to enable passage of said heated fluid out of said channel.

19. A receptacle according to claim 18, wherein said heated fluid is a gas.

20. A receptacle according to claim 19, wherein said gas is hot air.

21. A receptacle according to claims 19, wherein said heated fluid is a liquid.

22. A receptacle according to .any of claims 1 to 21, wherein the receptacle comprises thermal insulation.

23. A receptacle according to any of claims 1 to 22, wherein the receptacle comprises a rehydration system for rehydrating the contaminated material after decontamination.

24. A receptacle according to 23, wherein the rehydration system comprises one or more water distributing elements.

25. A receptacle according to claim 24, wherein the water distributing elements comprise at least one channel through which water can pass.

26. A receptacle according to claim 25, wherein the channel comprises at least one perforation to enable passage of said water out of said channel.

27. A receptacle according to any of Claims 1 to 26, wherein the receptacle comprises a connector to connect at least outlet to at least one heat distributing element for the recycling of the heated fluid.

28. A receptacle according to claim 27 wherein the heated fluid is recycled within the same receptacle.

29. A receptacle according to claim 27 wherein the heated fluid is recycled to at least one other receptacle.

30. A receptacle according to any of claims 1 to 29, wherein said receptacle is adapted to be portable.

31. A receptacle according to any of claims 1 to 30, wherein the contaminated material is a semi-solid or a solid selected from the group consisting of; soil, sand, shale, sludge, tar.

32. A receptacle according to any of claims 1 to 31, wherein the contaminant is a semi- volatile or volatile organic compound selected from the group consisting of hydrocarbons, spent oxides and cyanides.

33. A receptacle according to claim 32 wherein said contaminant is a polyaromatic hydrocarbon.

34. A system suitable for receiving a contaminated material, the system comprising a receptacle, a means to heat said material, at least one outlet to facilitate the exit of at least one contaminant from said system characterised in that said system comprises a means to guide said contaminant to an outlet, heating elements, thermal insulation and a rehydration system.

35. A method for guiding a heated fluid comprising a contaminant from a contaminated material contained within a receptacle comprising the steps of;

(i) providing a receptacle suitable for receiving a contaminated material

(ii) placing contaminated material in the receptacle described in (i);

(iii) heating said receptacle to a pre-determined temperature and;

(iv) guiding said heated fluid comprising a contaminant to at least one outlet.

36. A method of recycling the heated fluid used for heating a contaminated material comprising the steps of;

(i) providing a receptacle suitable for receiving a contaminated material

(ii) placing contaminated material in the receptacle described in (i); (iii) heating said receptacle to a pre-determined temperature and; (iv) recycling said heated fluid by connecting at least one outlet a receptacle in (ii).

37. A method according to claim 36, wherein said heated fluid is recycled within the same receptacle.

38. A method according to claim 36, wherein said heated fluid is recycled within at least one other receptacle.

39. A method of rehydrating a decontaminated material comprising the steps of;

(iii) dehydrating said material by heating to a pre-determined temperature and;

(iv) rehydrating said material.

40. A method according to claim 39, wherein said material is rehydrated prior to opening of the receptacle.

41. A method of decontaminating soil using a receptacle as claimed in the invention.

42. Soil whenever decontaminated using a receptacle according to any of the preceding claims.

43. Soil whenever decontaminated using a method as claimed in the invention.

44. A receptacle or a method or a system substantially as described with reference to the accompanying description and examples.