GB2452071A

GB2452071A - An apparatus for treating sediment

Info

Publication number: GB2452071A
Application number: GB0716467A
Authority: GB
Inventors: Paul Willacy; Michael Jones
Original assignee: Willacy Oil Services Ltd
Current assignee: Willacy Oil Services Ltd
Priority date: 2007-08-24
Filing date: 2007-08-24
Publication date: 2009-02-25
Also published as: FR2920098A1; GB0716467D0

Abstract

An apparatus and method for treating sediments, such as hydrocarbon waste products of a type including intractable liquids, sludges and solids etc. comprises a hermetically sealable chamber, into which the sediment to be treated is deposited and a heat source for heating the sediment within the chamber to thereby release one or more gaseous components. The apparatus further comprising a controller arranged to monitor the conditions within the chamber so as to automatically purge the chamber when a predetermined pressure and/or gaseous content is exceeded. Ideally the purge comprises inert gas. The apparatus and method having particular application in hydrocarbon recovery processes, where it is desired to minimise the quantity of hydrocarbon waste released into the environment.

Description

AN APPARATUS FOR TREATING SEDIMENT

The present invention relates to the disposal and treatment of waste products, and in particular relates to an apparatus and method for treating sediment The management and disposal of waste products produced by, for example, industries manufacturing andlor processing hydrocarbon materials, is an important environmental concern. To minimise the impact of such products on the environment, it is usually necessary to process the waste products via specialist disposal and recovery techniques Hydrocarbon waste products, such as intractable liquids, sludges and solids may be processed to recover some of the hydrocarbon components, which may then be re-used in another application In this way, the amount of organic material to be released into the environment is consequently reduced, which thereby minimises the overall volume of the waste product. Such recovery processes can be beneficial in the treatment of hydrocarbon waste destined for landfill sites, as environmental agencies impose strict regulations on the amount of organic material that can be deposited in such facilities.

In many of the recovery processes, the hydrocarbon waste is subjected to a multi-phase centrifugation, to separate out the solid and liquid components of the waste.

The remaining semi-solid waste or sediment then forms what is generally known as a sludge cake' or centrifuge cake', which allows for relatively easier handling of the residual waste product.

However, it is found that the centrifuge cake formed in some of the recovery processes may still contain concentrations of hydrocarbon components or other organic materials that could potentially have an impact on the environment.

Therefore, in some cases it may not be appropriate for the centrifuge cake to be deposited in a landfill site. As a result, other arrangements may be required for the disposal of the waste, which may increase costs for the company involved.

Moreover, it is usual for the centrifuge cake to have a relatively high degree of moisture trapped within the sediment that typically increases the volume of the waste, thereby further burdening the already limited resources of the landfill site.

According to an aspect of the present invention there is provided an apparatus for treating sediment, comprising: a hermetically sealable chamber, into which the sediment to be treated is deposited; a heat source for heating the sediment within the chamber to release one or more gaseous components; and a controller arranged to monitor the conditions within the chamber so as to automatically purge the chamber when a predetermined pressure and/or gaseous content is exceeded.

According to another aspect of the present invention there is provided a method of treating sediment, comprising the steps of depositing the sediment into a hermetically sealable chamber; heating the sediment within the chamber to release one or more gaseous components; and monitoring the conditions within the chamber so as to automatically purge the chamber when a predetermined pressure and/or gaseous content is exceeded.

Provision of a hermetically sealable chamber, into which the untreated sediment (e.g. centrifuge cake) is deposited, allows the sediment to be treated within a controlled environment, such that the pressure and gaseous content within the chamber can be closely monitored. The sealable chamber enables a controlled atmosphere' to be created within the chamber that may be independent of the atmosphere external to that of the chamber. The use of a controlled atmosphere is advantageous in the treatment of certain sediments, such as those containing hydrocarbon components, as the atmosphere may be controlled to limit the amount of oxidising gases within the chamber at any particular time, thereby avoiding the build up of a potentially explosive mixture of gases.

A heat source is provided within the chamber to heat the sediment. A heat source within the chamber is advantageous, as the heating of the sediment promotes the release of gaseous components, such as hydrocarbon compounds, which thereby substantially reduces the organic content of the treated sediment. As a result, the environmental impact of the treated sediment is significantly lowered, as a smaller amount of hydrocarbon waste is required to be deposited into the environment.

The heating of the sediment may also have the advantageous effect of dnving off moisture from within the sediment, so that the sediment substantially dries and Jo may shrink in size, thereby reducing the volume of the waste product. In this way, more of the waste product may then be deposited into a given volume of the landfill site, which consequently reduces the demands on the available resources within that site.

Provision of a controller arranged to monitor the conditions within the chamber allows the pressure and/or gaseous content to be monitored during the treatment of the sediment. In this way, a pressure threshold or gaseous content level may be set at which the internal atmosphere within the chamber is to be purged (e.g. vented, replaced etc.), thereby ensuring a safe treatment and handling of the sediment and/or the gaseous components. The controller is preferably arranged to control the whole treatment process, such that upon encountering a pressure or gaseous content in excess of the predetermined threshold or level, it can automatically purge the chamber and may also, preferably, interrupt the heating of the sediment.

The automatic purging of the internal atmosphere within the chamber is advantageous as it avoids the build up of a potentially explosive and/or flammable mixture of gases.

The controller may be arranged to monitor the gaseous content of oxidising gases within the chamber, most notably oxygen. Therefore, in response to a build up of too much oxygen (e.g. corresponding to a content that is likely to create an explosive mixture of gases), the controller can automatically purge the chamber to reduce the amount of oxygen, thereby eliminating the risk of a potentially explosive event within the chamber.

In an exemplary embodiment, the heat source is an infra-red (IR) heat source that is arranged to irradiate the sediment within the chamber. The use of an hR heat source is particularly advantageous, as the wavelength of the emitted IR radiation may be selected to excite specific molecular bonds of compounds within the sediment to promote enhanced evaporation and/or release of these compounds from the waste product. For instance, to evaporate hydrocarbons, a wavelength strongly absorbed by C- C and C-H bonds may be selected, whereas for releasing water, a different wavelength absorbed by 0-H bonds may be selected. The wavelength of the IR radiation may be controlled by altering the temperature (and hence spectral emissivity) of the heat source. The IR heat source preferably comprises a plurality of conventional IR heating tube lamps that may be sealed behind a substantially transparent (i.e. to IR radiation) window. Sealing the heat source behind a window is advantageous, as it not only shields the heating tubes from any dust and/or debris thrown up by the sediment, but also enables the electrical terminal connections to the heating tubes to be air cooled to prevent possible overheating, without introducing oxidising gases (e.g. oxygen) into the sealed chamber.

It is to be appreciated however, that any suitable heat source may be used within the chamber in accordance with the invention, including conductive and/or convective heating based devices, as well as radiative processes. However, as will be apparent to a person skilled in the art, naked flames or burners are not suitable due to the potentially explosive nature of the gases within the chamber.

The sediment within the chamber may be supported by a processing bed or platform, preferably located beneath the IR heat source. The processing platform may act as a conveyance for the sediment such that the sediment is made to pass from one side to the other beneath the IR heat source. The processing platform is preferably associated with an agitating means to agitate the sediment. In this way, the particulate matter within the sediment is advantageously agitated (e.g. shaken and/or vibrated) to enable an increased exposure to the JR radiation. Agitating the sediment further improves the efficiency of the treatment process, as it typically leads to a significantly increased evaporation and/or release of hydrocarbon compounds and facilitates faster drying of the sediment as it passes beneath the JR heat source.

The agitating means may comprise a plurality of motors, most preferably 3, that are arranged to vibrate the processing platform, preferably in a controlled sequence, so that the sediment passes from one side of the platform to the other.

However, it is to be understood that the agitating means may be operated according to any appropriate vibrational pattern to either advance the sediment across the processing platform, to halt and vibrate the sediment at a particular location on the platform, or to repeatedly reverse the direction of the sediment, so that it passes back and forth across the platform, or any combination of these patterns, in order to optimise the degree of agitation of the sediment.

The plurality of motors may be controlled to convey a batch of sediment from one side of the processing platform and then to form a substantially uniform layer of sediment on the platform by vibrating the sediment to uniformly distribute it across the processing area of the platform. The sediment may then be vibrated in place (i.e. without transverse displacement of the sediment) to achieve agitation and to thereby expose a continually refreshed surface of the sediment to the radiant heat treatment. Thereafter, upon drying, the motors can be controlled to convey the dried sediment off the processing platform for subsequent disposal.

The operation of the motors may be directly controlled by the controller, which may be programmed to advantageously vary the vibrational patterns and treatment cycle according to the nature and/or type of sediment being treated.

Hence, in accordance with the invention, the treatment of hydrocarbon waste products can be significantly improved, as both the heating and agitation of the sediment can be specifically controlled to optimise the drying process and the release of gaseous components.

It is to be appreciated however, that any suitable form of agitating means may be used to agitate the sediment on the processing platform, including hydraulic and/or electrical actuators etc. The processing platform may also incorporate a substantially non-stick surface or coating onto which the sediment is deposited, to thereby assist with the propagation of the sediment across the platform.

The purging of the chamber is accomplished by way of purging means that are preferably installed within the chamber. The purging means may be controlled directly by the controller, so that automatic purging can commence should the pressure and/or gaseous content within the chamber exceed the predetermined threshold or level. In preferred embodiments, the purging means is arranged to introduce a substantially inert gas into the chamber. The purging of the chamber removes oxidising gases and/or other gaseous components (e.g. water vapour, CO2 and hydrocarbon compounds) from within the chamber and instead replaces them completely, or in part, with the inert gas so as to dissipate any potentially explosive mixture of gases.

The inert gas may be a single gas, most preferably nitrogen, or a mixture of inert gases and may be introduced into the chamber at atmospheric pressure However, it is to be appreciated that the inert gas can be introduced at other pressure levels depending on the particular application and purging requirements.

The chamber may further comprise a gas extraction system having an extractor, preferably in the form of one or more exhaust fans, to facilitate the removal of the oxidising gases and/or other gaseous components during the purging process. The gas extraction system may be fitted externally to the chamber with the one or more exhaust fans being arranged such that the chamber gases may be extracted via an aperture or vent located in a surface of the chamber, while maintaining a hermetic seal against the external atmosphere surrounding the chamber.

A gas scrubbing unit may also be fitted to the chamber so as to receive the gases extracted by the gas extraction system. The gas scrubbing unit and the gas extraction system may be directly coupled together within the same unit or else may be connected via piping or other suitable gas-carrying conduits. The gas scrubbing unit removes potentially harmful gases from being directly released into the environment and can also lower the amount of organic gases (e.g. CO2. H2S) that are vented into the atmosphere. In preferred embodiments, the gas scrubbing unit includes a condenser unit and one or more activated carbon filters, as conventionally used in the art.

To ensure that the chamber remains hermetically scaled from the external atmosphere surrounding the chamber, means are provided that enable the sediment to be loaded and discharged without allowing the ingress of air into the chamber and/or the egress of gases out of the chamber. The means for maintaining the hermetic seal may include both an entry and exit airlock, preferably disposed so as to be substantially diametrically opposed on either side of the chamber. Sediment may be loaded into the entry air lock whereupon a valve mechanism isolates the sediment so that it may be deposited within the chamber without the internal atmosphere of the chamber coming into contact with the external atmosphere. In like manner, the treated sediment may then be discharged from the chamber by way of a second valve mechanism in the exit airlock.

The airlocks allow the sediment to be processed through the chamber in accordance with the method of the invention, while avoiding the introduction of additional oxygen into the chamber from the surrounding air Moreover, the airlocks also serve to minimise, or eliminate, the undesired release of gaseous components into the environment while loading/discharging the sediment.

The apparatus may further comprise loading means for loading and depositing the untreated sediment into the chamber. The loading means may be a series of conveyor belts, which in preferred embodiments, includes an inclined conveyor that feeds a substantially horizontal conveyor which abuts the entry airlock. The sediment may be loaded onto the loading means by way of a feed hopper or other funnelling device forming part of the apparatus.

A transporting means for removing the discharged (or treated) sediment away from the chamber may also be provided, which in preferred embodiments may also comprise one or more conveyor belts that is/are arranged to receive the discharged sediment from the exit airlock.

However, it is to be appreciated that any suitable form of loading and discharging means and/or any configuration of conveyors may be used in conjunction with the chamber andlor method of the present invention.

In certain situations it may be useful to cool the heated sediment following discharge from the chamber to facilitate easier handling of the waste product.

Therefore, the apparatus may be fitted with cooling means for decreasing the temperature of the treated sediment. The cooling means may comprise a cooling jacket that is preferably arranged around the transporting means, which in one embodiment involves enclosing an exit conveyor in a water cooled jacket.

It should be appreciated however that any suitable form of cooling means may be used to cool the sediment after treatment, including radiators, fans and air blowers or any combination thereof Although the present invention is ideally suited for treating sediment derived from hydrocarbon recovery processes, it will be recognised that one or more of the principles of the invention could also be used in other waste treatment and disposal applications. Moreover, the apparatus of the invention may either be permanently sited at a waste processing facility or else may be mobile so that it can be transported along with the recovery equipment for in situ processing at a refinery or petrochemical plant or other industrial site handling hydrocarbon contaminated sludges etc In mobile embodiments, the apparatus may be configured to be housed within a transport container, which in one embodiment is a customised 40 ft (approx. 12 metres) transport container housing the chamber and controller, thereby permitting ease of storage and transportation to the processing site. The mobility of the apparatus is advantageous as it allows the apparatus to be deployed and used at a number of different sites, as and when waste processing is required. In this way, the need to permanently allocate a fixed site for the apparatus can be avoided, which thereby can liberate valuable working space within the industrial site at which the waste is to be processed. Preferably, only the loading and discharge means, along with the gas scrubbing unit, need be installed outside of the transport container. However, it is to be appreciated that any suitably sized container or vessel may be used to house the apparatus of the invention in accordance with any of the above embodiments.

An embodiment of the invention will now be described in detail by way of example and with reference to the accompanying drawing in which: Figure 1 is a schematic representation of a particularly preferred arrangement of a sediment treatment apparatus according to the invention.

With reference to Figure 1, there is shown a schematic representation of one example of a sediment treatment apparatus I according to the invention. In this embodiment, the apparatus 1 is configured to be mobile and has been temporarily deployed at the waste processing site for use with a conventional hydrocarbon recovery system. The apparatus I comprises a steel chamber 10 having an interior cavity that is capable of being hermetically sealed from the surrounding atmosphere. The chamber 10 is a pressurisable vessel that is approximately 10 metres in diameter, having a wall thickness sufficient to withstand several times atmospheric pressure.

A heat source in the form of an array of infra-red (IR) heating tubes 12a..12c is fitted within the chamber 10 to heat the sediment 14. In the example of Figure 1 the IR heating tubes 12a.. 12c are arranged so as to irradiate the sediment 14 as it passes beneath the tubes. Each IR heating tube has a power output of 2kW, with a typical array having 48 tubes (i.e. a power output of 96 kW in total). The combined power output of the JR heating tubes I 2a.. I 2c is sufficient to raise the temperature within the chamber 10 to between about 250 degrees C to about 300 degrees C. To prevent contamination of the JR heating tubes 12a.. 12c by dust and/or debris from the sediment 14 and also to permit cooling of the tube terminals, the tubes are sealed behind a glass window 16 having a thickness of 3 mm. The glass is specially selected so as to be substantially transparent to JR radiation, while also being able to withstand the temperatures encountered within the chamber 10. A thickness of 3mm is found to be the optimum thickness for the window, as this is sufficient to maintain structural strength and integrity, while not unduly attenuating the JR radiation from the heating tubes.

The sediment 14 is loaded into the chamber 10 so that it is deposited on a processing platform 18. The platform 18 provides a substantially planar support surface located beneath the JR heating tubes 12a..12c. To withstand the temperatures within the chamber 10, the platform 18 is made from mild steel and is approximately 6mm in thickness, but can vary between 5 to 10 mm depending on the particular arrangement. The use of such a material is found to be cost effective as it is ideal for withstanding the conditions within the chamber, but is readily available and convenient to implement.

Mounted beneath the platform 18 is a series of vibrating motors 20 that are arranged to vibrate in a controlled sequence so that the sediment 14 is urged to propagate from one side of the platform 18 to the other. The vibrating sequence can be adapted to create whatever vibrational pattern, or combination of patterns, that is most appropriate for the particular sediment, such that the frequency and/or amplitude of the vibrations can be altered to increase/decrease the rate at which the sediment is processed. The optimum processing rate is around 1000 kg of sediment per hour, but other rates can be employed depending on the particular application.

The vibrating motors 20 also serve to agitate the sediment 14 on the platform, which significantly increases the sediment's exposure to the radiation from the JR heating tubes 12a. 12c Agitating the sediment 14 in this way, leads to an enhanced release of gaseous components and/or moisture from the sediment 14.

The heating and agitation of the sediment are controlled by a microprocessor based controller 22, which is able to monitor the conditions within the chamber 10 by way of conventional pressure and gas sensors (not shown) The controller 22 is connected to the sensors by way of a sensor interface which permits pressure and gas contentllevel data to be communicated to the controller 22. To ensure a safe and reliable operation of the apparatus 1, the controller 22 is programmed to invoke automatic procedures in response to the pressure and/or gas content exceeding a predetermined threshold or level. In this way, a build up of potentially explosive gases within the chamber 10 can be avoided.

The apparatus 10 further comprises a purging means 24 that includes nitrogen gas tanks coupled to injectors located within the chamber 10. The purging means 24 are under the direct control of the controller 22 and can be invoked to purge the chamber 10 by introducing nitrogen to flush out the oxidising gases and/or other gaseous components (e.g. water vapour, CO2 and hydrocarbons etc).

The purging of the chamber 10 is facilitated by an exhaust fan 26 mounted at the top of the chamber 10, which extracts the oxidising gases and/or other gaseous components and passes them into a gas scrubbing unit 28 of conventional design.

The gas scrubbing unit 28 is mounted externally to the chamber 10 and receives the extracted gases by way of a vented aperture in the exhaust fan 26. The gas scrubbing unit 28 removes any potentially harmful gases by passing the gases through a condenser and activated carbon filter, as known in the art. In this way, the impact that the released gases have on the environment is significantly reduced.

The controller 22 is programmed to automatically invoke the purging of the chamber 10 when either the predetermined pressure threshold and/or the gas content level exceeds pre-set values for safe operation (i.e. to avoid the build up of explosive gases) The automatic procedures will then activate the exhaust fan 26 to extract the gases from within the chamber 10, and will subsequently introduce nitrogen by way of a replacement. The controller 22 will also interrupt the heating of the sediment 14 by denying power to the JR heating tubes 12a..12c.

Referring again to Figure 1, the untreated sediment is loaded into the chamber 10 by way of an entry airlock 30. The airlock 30 has an integral valve mechanism that isolates the sediment so that it may be deposited without allowing additional oxygen (from the air) into the chamber 10. This mechanism prevents the oxygen content within the chamber 10 from reaching a level at which an explosive event may occur and also maintains the hermetic seal of the chamber 10.

In like manner, an exit airlock 32 is also provided which allows for the discharge of treated sediment without the ingress of additional oxygen or egress of undesired gaseous components. The operation of the entry and exit airlocks 30, 32 is fully automated and is under the control of the controller 22.

Untreated sediment is loaded into the entry airlock 30 by way of two conveyor belts 34a, 34b. One of the conveyors 34a is inclined with respect to the ground level, while the other 34b is substantially horizontal and fixed at the height of the entry airlock 30. An advantage of using an inclined conveyor 34a is that the sediment loading operations can be performed manually at ground level with the conveyor 34a transporting the sediment up to the height of the airlock 30. A feed hopper 36 is positioned over the inclined conveyor 34a and is loaded at ground level by way of a small excavator under manual control.

To transport the treated sediment away from the chamber 10 a further conveyor belt 38 is used that is located adjacent to the exit airlock 32. The treated sediment will be at a relatively high temperature (e.g. 250 to 300 degrees C) when it is discharged from the chamber 10. Therefore, to ensure a safe disposal the apparatus I is fitted with a water cooling jacket 40 that is fixed around the conveyor 38 to lower the temperature of the sediment and permit easier handling of the waste product, prior to loading into a disposal drum 42 etc The above embodiment is described by way of example only Many variations are possible without departing from the invention

Claims

1. An apparatus for treating sediment, comprising: a hermetically sealable chamber, into which the sediment to be treated is deposited; a heat source for heating the sediment within the chamber to release one or more gaseous components; and a controller arranged to monitor the conditions within the chamber so as to automatically purge the chamber when a predetermined pressure and/or gaseous content is exceeded.

2. The apparaius as in Claim I, wherein the heat source is an infra-red heat source.

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3. The apparatus as in Claim 2, wherein the infra-red heat source comprises a plurality of infra-red heating tubes.

4. The apparatus as in Claim 2 or Claim 3, wherein the infra-red heat source is sealed behind a substantially transparent window.

5. The apparatus as in any preceding claim, further comprising a processing platform within the chamber to receive the deposited sediment.

6. The apparatus as in Claim 5, wherein the platform is associated with an agitating means to agitate the sediment.

7. The apparatus as in Claim 6, wherein the agitating means comprises a plurality of vibrating motors.

8. The apparatus as in any preceding claim, wherein the controller is arranged to monitor the level of oxidising gases within the chamber.

9. The apparatus as in any preceding claim, further comprising purging means under the control of the controller for introducing a substantially inert gas into the chamber.

10. The apparatus as in any preceding claim, further comprising loading means for depositing the untreated sediment into the chamber.

ii. The apparatus as in any preceding claim, wherein the chamber includes an airlock through which the untreated sediment enters the chamber.

12. The apparatus as in any preceding claim, wherein the chamber includes a seoiid airlock through which the treated sediment is discharged from the chamber.

13. The apparatus as in any preceding claim, further comprising means for transporting the treated sediment away from the chamber.

14. The apparatus as in Claim 12 or Claim 13, further comprising cooling means for decreasing the temperature of the treated sediment.

15. The apparatus as in any preceding claim, further comprising a gas scrubbing unit connected to the chamber.

16. The apparatus as in Claim 15, wherein the gas scrubbing unit includes a condenser unit and at least one activated carbon filter.

17. The apparatus as in Claim 15 or Claim 16, further comprising an extractor, coupled to the gas scrubbing unit, for removing gases from the chamber.

18. A method of treating sediment, comprising the steps of: depositing the sediment into a hermetically sealable chamber; heating the sediment within the chamber to release one or more gaseous components; and monitoring the conditions within the chamber so as to automatically purge the chamber when a predetermined pressure and/or gaseous content is exceeded.

19. The method as in Claim 18, wherein the heating step involves irradiating the sediment with infra-red light.

20. The method as in Claim 18 or Claim 19, further comprising the step of agitating the sediment before andlor during and/or after the heating step.

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21. The method as in any of Claims 18 to 20, wherein the purging step includes extracting gases from within the chamber.

22. The method as in any of Claims 18 to 21, wherein the purging step includes introducing a substantially inert gas into the chamber.

23. The method as in any of Claims 18 to 22, further comprising the step of interrupting the heating when the predetennined pressure and/or gaseous content is exceeded.

24. The method as in any of Claims 18 to 23, wherein the step of depositing includes loading the sediment into the chamber via an airlock in the chamber.

25. The method as in any of Claims 18 to 24, further comprising the step of transporting the treated sediment away from the chamber via a second airlock in the chamber.

26. The method as in any of Claims 18 to 25, further comprising the step of cooling the treated sediment to decrease its temperature.

27. An apparatus and method as substantially described herein with reference to the accompanying drawings. I'