Grease interceptor for a waste water stream from an exhaust fan assembly

To facilitate the collection of grease and water from commercial kitchen exhaust fans the invention provides a collection tank in communication with the drainage spout of the fan assembly. The tank has a lid for sealing the tank, a first reservoir for collecting the stream of grease and water and a second reservoir below the first reservoir for receiving water separated from the grease and water stream in the first reservoir. The first and second reservoirs are separated by a sloping plate. The tank also includes a siphoning apparatus which when connected to a source of high pressure fluid such as water or steam can purge the second reservoir of water and recycle the water back to a fan cleansing operation or to a disposal facility.

CROSS REFERENCE TO RELATED APPLICATIONS

This is the U.S. National Stage of International Application No. PCT/IB2012/052269, filed May 8, 2012, which was published in English under PCT Article 21(2).

TECHNICAL FIELD

The present invention relates generally to removal of organic contaminants from wastewater and in particular, to removal and collection of wastewater fats, oils, and grease from the waste water stream of commercial exhaust fans such as those found on the roof tops of large kitchen facilities.

BACKGROUND ART

A typical kitchen ventilation system includes an exhaust hood or canopy, ductwork, fan system, and a means of providing adequate make-up air. The entire system must constitute a fire-safe assembly within the building.

Exhaust hoods and canopies capture heat and contaminates in the air by means of filters, extraction baffles (cartridges), and water mist systems. There are many style variations of hoods with canopy styles-a large box with and open bottom-being the most common. Styles selection is based on the type of oven and the expected contaminates to be removed. Referring toFIG. 1, there is a drawing of one type of venting arrangement comprising a back shelf hood over a cook line. While there are several styles of hoods, all fall within two major categories:

Type I hoods carry a listing label and are manufactured and installed according to the manufacturer's and listing agencies' requirements. They are designed to handle grease and include a number of integrated components within the hood.

Type II hoods are used in the collection of steam, vapor, heat, and odors—but not grease. The two sub-classifications of Type II hoods are condensate and heat/fume.

Referring toFIG. 2, there is shown one example of an exhaust hood and associated duct work installed in a ceiling. The exhaust ductwork transfers contaminated air, cooking heat, and grease vapors from the hood to the exhaust fan. Exhaust ducting should have the following qualities:

Ducts that accumulate combustible grease should be constructed from 16-steel or 18-gage stainless steel as per code requirements.

Ducts must be securely supported by non-combustible duct bracing and supports designed to carry the gravity and seismic loads as per code requirements. No fasteners should penetrate the duct.

Duct enclosures made from materials such as of gypsum board, plaster, concrete, or ceramic tiles must be approved as a continuous fire-rated enclosure.

Referring toFIG. 3there is shown a typical exhaust fan used for a commercial kitchen. Exhaust fans move the heat and contaminated air out of the building. All exhaust fan components must be accessible or have removable access panels for cleaning and inspection and must be designed to contain and drain any excess grease. There are three major types of exhaust fans:

Up-blast fans are typically aluminum centrifugal fans that are designed for roof mounting directly on top of the exhaust stack.

Utility fans are normally roof-mounted with the inlet and outlet 90 degrees from each other and are typically used where high-static pressure losses exist.

Inline fans are typically located in the interior duct and are used where exterior fan mounting is impractical.

Fire Code Requirements

As kitchen ventilation is used, grease laden vapors are carried through the entire system. This action deposits oil on all interior parts of the system which must be cleaned to reduce the risk of fire. The minimum frequency and standard for cleaning is provided by the National Fire Protection Association (NFPA) and fire codes NFPA96.

Cleaning ducting and fans also requires following these codes:

Restaurant NFPA Fire Code 96: 4.1.5

The responsibility for inspection, maintenance, and cleanliness of the ventilation control and fire protection of the commercial cooking operations shall be the ultimate responsibility of the owner of the system provided that this responsibility has not been transferred in written form to a management company or other party.

Fan Access Panel NFPA Fire Code 96: 8.1.5.3.1

Up-blast fans shall be supplied with an access opening of a minimum 76 mm by 127 mm (3 in. by 5 in.) or a circular diameter of 101 mm (4 in.) on the curvature of the outer fan housing to allow for cleaning and inspection of the fan blades.

Rooftop terminations shall be arranged with or provided with the following: (8) a hinged up-blast fan supplied with flexible weatherproof electrical cable and service hold-open retainer to permit inspection and cleaning that is listed for commercial cooking equipment.

Approved up-blast fans with motors surrounded by the airstream shall be hinged, supplied with flexible weatherproof electrical cable and service hold-open retainers, and listed for this use.

Wiring systems of any type shall not be installed in ducts.

Rooftop Grease Containment NFPA Fire Code 96: 7.8.2.1

Rooftop termination shall be arranged with or provided with the following: (4) The ability to drain grease out of any traps or low points formed in the fan or duct near the termination of the system into a collection container that is noncombustible, closed, rainproof, and structurally sound for the service to which it is applied and that will not sustain combustion. (5) A grease collection device that is applied to exhaust systems that does not inhibit the performance of any fan.

Up-blast fans shall have a drain directed to a readily accessible and visible grease receptacle not to exceed 3.8 L (1 gal).

The entire exhaust system shall be inspected for grease buildup by a properly trained, qualified, and certified company or person(s) acceptable to the authority having jurisdiction and in accordance with Table 11.4. [SeeFIG. 4]. Upon inspection, if the exhaust system is found to be contaminated with deposits from grease-laden vapors, the contaminated portions of the exhaust system shall be cleaned by a properly trained, qualified, and certified company or person(s) acceptable to the authority having jurisdiction. Hoods, grease removal devices, fans, ducts, and other appurtenances shall be cleaned to remove combustible contaminants prior to surfaces becoming heavily contaminated with grease or oily sludge.

Kitchen Ventilation Cleaning Process

The kitchen Ventilation cleaning process can be broken into 5 stages:

Cleaning of Filters

Bagging the Hood

Exhaust fan cleaning

Fans Grease receptacle

Ducting and Hood

Cleaning of Filters

The kitchen exhaust cleaning personnel first remove and clean the filters from the hood, this cleaning is usually done by means of applying a degreaser and washing with high pressure steam over a containment tank to capture all waste generated. This process is complete once all built up oil and grease in no longer present on the visible surfaces.

Bagging the Hood

Once the hoods filters are removed, the cleaning personnel begin what is called the bagging process. Using plastic, tape and clamps, the kitchen hood is surrounded with plastic in a manner to capture all wash water. This is then to be collected and funneled into a collection container and not to fall on the floor or ground.

Exhaust Fan Cleaning

Once the hood is bagged, the cleaning personnel begin the cleaning process of the exhaust fan on the roof. This includes spraying chemical degreasers and high pressure steam onto the interior parts of the fan. During this process all wash water injected into and onto the fans parts is expelled through the precipitation drain and onto the roof and eventually into the storm drain connecting to the roof top. This cleaning process merely displaces the grease from the fan to the roof drain and causes pollution. This task is complete once all built up of oil and grease in no longer present on the visible surfaces.

Fans Grease Receptacle

The grease receptacle must be emptied of oil and grease and or the filters must be changed. Typically this unit is mounted to the fan to collect the oil that drips from the fan during operation. Rain water must also pass this system so grease is easily carried away and onto the roof. A typical capturing design is a collection box that fails its intended function. This is because once full of rain water, the oil floats to the top and spills onto the roof. This grease receptacle can also contain filter media to hold onto the grease and prevent escape; unfortunately this media most often does not get changed due to its unavailability or its inability to perform its deigned function. The result is the hazardous condition depicted in the photograph inFIG. 5.

Ducting and Hood

Once the fan is cleaned, chemical degreasers and high pressure steam are sprayed into the ducting below the fan leading down from the roof and towards the kitchen below. In most cases access doors can be found that supply additional cleaning points for further cleaning. This wash water and chemical flows towards the hood and is then directed by the tarp into the collection container. Once the ducting is cleaned the hood is washed by the same manor of steam and chemicals. All waste water is then disposed of according to the local sewer use bylaw.

The Exhaust Fan Drain Spout

Referring back toFIG. 3, there is shown one example of an exhaust fan. Since the first edition of NFPA96 in 1961 exhaust fan design has improved in order to meet rigid fire safety requirements. Thanks to the adoption of these codes by local fire departments across North America there have been dramatic improvements in fire safety. Prior to the enforcement of these codes, fans would discharge oil directly and uncontrollably from multiple drain points directly onto the roof. As restaurants upgraded over the years to conform to the NFPA standards, exhaust fans have become more reliable and waste discharge points have been focused to one spout.

Through this spout, rainwater that falls into the interior of the fan is permitted to escape.

Without the spout, water would build up inside the fan and eventually spill into the interior of the building.

This spout also permits excess oil to be released from the fan

Exhaust Fan Grease Discharge

Still referring toFIG. 3, exhaust fans are welded to their base; these fans rarely leak or drain from any place other than the spouts. However, exhaust fans have a silicon seal around the bottom and these seals typically begin to leak within one year of installation. The only way to properly reseal these leaks is by an adhesive. Silicon will break down under oily conditions.

Another common problem with a silicon seal is that the exhaust fan cleaning process tends to remove any silicon and makes replacement necessary. An adhesive will withstand both the properties of operating and cleaning.

Environmental Requirements

The kitchen exhaust fan has proven to be the most difficult to manage both during operation and maintenance. Oil can be observed leaking from the fan during the cooking operation and rain provides the transportation it needs to be carried to the roof and drain. This event is both harmful for the roof and the environment.

When servicing the exhaust fan, a typical service company will use high pressure steam, water and chemicals. These methods are used to break down the oil and grease from exhaust fan.

Grease and chemicals can be observed discharging from the drain spout during the cleaning process. Costly truck mounted vacuums or effective onsite improvisation is needed to avoid this infraction.

Therefore, considering the above shortcomings, there is still a requirement for a device that will capture contaminated water waste and grease operation and maintenance and eliminate the pollution caused by cleaning and operation of exhaust fans. There is also a requirement for a device that will help restaurants and cleaning personnel to meet stringent fire codes and anti-pollution codes.

DETAILED DESCRIPTION

One object of the present invention is to meet NFPA 96 requirements.

Another object of the invention is to protect the roofs of kitchen buildings from grease and oil spillage.

Yet another object of the invention is to provide adequate grease capture capacity.

A further object of the invention is to fit all commercial exhaust fan systems.

Still another object of the invention is to provide an economical solution in the marketplace.

One advantage of the present invention is that it requires far less maintenance than known technology.

A second advantage of the present invention is that it can be coupled to a treatment process such as biotechnology cleansing process resulting in an effluent which places significantly less stress on both public and private sewer systems.

Yet another advantage of the invention is that grease and oil can be collected and then used in the manufacture of biodiesel.

Yet another advantage is the cost savings to both public and private entities that result from such cleaner effluent.

Still a further advantage of the invention is that there is no mechanical process involved in collecting the waste water stream.

Referring now toFIG. 6there is shown a typical installation of an exhaust fan assembly2on a roof30. The exhaust fan assembly2may be on the roof of a restaurant or other commercial kitchen facility. The exhaust fan assembly2comprises a housing28for housing the exhaust end of the ventilation ducting16coming up from a stove or an oven. The ducting housing28is fixed to the roof by support members26and18. On top of the duct housing28is installed the fan and motor assembly29. The fan and motor assembly29comprises an electric motor8, a belt drive6to connect the motor to a fan drive shaft7and a fan belt tension adjuster4. Drive shaft7is connected to a set of fan blades to create suction within the ducting and blow the exhaust out the exhaust cowling32which encircles the fan and motor housing34. Cooling vent10provides cooling air to the electric motor8. The fan and motor housing34is hinged14to the duct housing28for access to the upper reaches of the duct16for cleansing and servicing. A drain spout22is provided to drain rain water that falls into the interior of the fan housing and to prevent a buildup of water within the fan housing that would eventually spill into the interior of the building. The water that flows through the drain spout is highly contaminated with fats, oils and grease. The drain spout drains into a grease containment tray24which is often prone to overflowing onto the surface of the roof30as illustrated in the photograph ofFIG. 5.

Referring now toFIG. 7there is shown the same exhaust fan assembly2ofFIG. 6indicating the path of exhaust air40from the duct16through the exhaust cowling32and into the atmosphere.

Referring now toFIG. 8there is shown the same exhaust fan assembly2roof top installation indicating pathways42of rainwater and wash water/chemical mixtures into the fan and motor assembly29. Furthermore, fan blade12when rotating at very high speeds drives grease-laden moisture44into the spout22where it drains46into grease containment tray24.

Still referring toFIG. 8and toFIG. 5, it can be seen that failure to properly clean the ducting and exhaust fan assembly2, blockage of the drainage spout22or over flowing of the grease collection tray24will result in significant spillage, environmental liability and damage to the roof. Therefore there is a requirement to provide for a waste collection device that prevents these spills and provides for a clean and cost effective way to maintain the exhaust fan and housing assembly.

Referring now toFIG. 9there is shown one embodiment of the invention80in operation with fan assembly and ducting installation50installed on roof52. The exhaust cowling54and the motor fan housing64are mounted to duct housing56. Exhaust pathways58are shown from ducting60through exhaust cowling54. Rainwater and wash water pathways70are shown draining74through drain spout76into the invention80. This embodiment of the invention80, shown in cross-section, comprises a collection tank82, a tank cover plate84, a wall mounting bracket86for mounting the collection82to a side wall88of the duct housing56and a piping assembly90the operation of which is more fully explained below.

Referring now toFIG. 10there is shown a containment tank100of one embodiment of the invention from a right-hand top perspective. The containment tank100is manufactured from ‘16 gauge 316 stainless steel’. The containment tank100comprises a right hand wall102, a left hand wall104, a front wall106, a rear wall108and a bottom110. The tops of the walls102to108each have a lip112to118to permit sealing placement of a cover plate (described below) using bolts120and122and a suitable nut such as a butterfly nut. The right hand wall102includes an aperture130which connects the containment tank a piping assembly more fully explained below.

Referring now toFIG. 11there is shown the containment tank100ofFIG. 10in cross-sectional view through section A-A inFIG. 10. The front surface106, the back surface108and the bottom surface110are formed from a single piece of 316 stainless steel and bent so that the corners132and134are rounded. The front wall lip136projects outwards from the containment tank and the rear wall lip138projects inwards into the containment tank. The back wall108mounts adjacent to the duct housing containment wall88and projecting the lip138inwards prevents interference with the installation of the containment tank against the duct housing wall.

Referring now toFIGS. 12A, B and C there is shown inFIG. 12Aa top view of right hand wall102, inFIG. 12Ba front view of right hand wall102and inFIG. 12Ca side view of right hand wall102. The right hand wall102is manufactured from a single piece of 16 gauge 316 stainless steel. The front view shows the location of aperture130. Corners140and142are cut to fit corners132and134respectively of tank100.FIG. 12Ashows the top lip116of wall102having aperture144to accommodate bolt122as shown inFIG. 10.FIG. 12Cshows the wall in side view with lip116projecting into the containment tank. Wall102is fixed in place to the right hand side of the containment tank using suitable fixing means such as welding.

Referring now toFIGS. 13A, B and C there is shown inFIG. 13Aa top view of left hand wall104.FIG. 13Bshows a front view of the left hand wall104andFIG. 13Cshows a side view of left hand wall104of the containment tank100. The corners150and152of wall104are contoured to fit the left hand side of the containment tank100corners132and134respectively. The top view inFIG. 13Aillustrates the lip114projecting into the tank100and the bolt aperture154which is used to accommodate bolt120. The side view ofFIG. 13Cshows lip114in side view.

Referring now toFIG. 14there is illustrated containment tank100in a left hand wall104top perspective view. Piping assembly200is installed within the tank100. The piping assembly200is connected to the containment tank by way of aperture130in right hand wall102.

Referring now toFIGS. 15Ato D there is shown the piping assembly200in top view inFIG. 15A, in side view inFIG. 15B, in front view inFIG. 15Cand in cross-sectional side view inFIG. 15D.

Referring toFIG. 15B, the piping assembly comprises a piping elbow202, a ‘J’-shaped venturi pipe204, a connector206which is inserted into aperture130in right hand wall102and a stiffening member208. The first end205of the venture pipe204is located within the elbow202and the second end207of the venture pipe204is open to atmosphere above the tank lid and outside of the tank. The operation of the piping assembly is more fully explained below.

Referring now toFIGS. 16Aand B there is shown inFIG. 16Aa front view of elbow202and inFIG. 16Ba side view of elbow202. The elbow is manufactured from 16 gauge 316 stainless steel. In the embodiment shown the pipe is about 1.5 inch in diameter and forms a90degree elbow. The elbow has in inlet201and an outlet203. The elbow is used to drain water from the tank100that will fill the tank100during the course of cleansing operations as more fully explained below.

Referring now toFIGS. 17Ato D there is shown inFIG. 17Aa front view of one embodiment of the venture pipe204.FIG. 17Dshows a side view of the venture pipe andFIG. 17Cshows a top view of the venturi pipe204. A detailed view of pipe end210is shown inFIG. 17B. The venturi pipe204is a ‘J’-shaped pipe having a higher end212and a lower end210. End212penetrates the top lid of the tank as more fully explained below and is exposed to atmospheric pressure whereas end210is tapered so as to create a venturi tube. The venturi pipe204acts with elbow202to siphon water from the containment tank second reservoir either in a recirculating mode during cleaning and degreasing of the fan and ducting; or, in a draining mode to drain the containment tank to a mobile disposal unit.

Referring toFIG. 18there is shown one embodiment of the lid220for placement over the top of the containment tank100. The lid220comprises a flat stainless steel panel222surrounded by upwardly disposed edges on each side224to230. The lid220is fastened to the top of the containment tank100by bolts120and122as shown inFIG. 10which are placed through lid apertures232and234inFIG. 18. A suitable nut such as a butterfly nut can be used to tighten the lid onto the surface of the container. Aperture236is a drain aperture and is used to drain fluids that drip from the fan housing during operation as a result of rain or to drain cleaning and degreasing fluids during servicing onto the top of the lid and into the container. Aperture238permits end207of the venturi pipe204to have access to atmospheric pressure.

Referring now toFIG. 19there is shown a perspective view of one embodiment of the wall mount assembly240used to mount the containment tank100to the sidewall of the duct housing88as illustrated inFIG. 9. The wall mount assembly240comprises a wall mount bracket242having a plurality of apertures244for mounting to the side wall88of the duct housing56. The profile of the bracket240is ‘L’ shaped. Fixed to the bottom leg246of the wall mount bracket is an adjusting bracket248. The adjusting bracket relies upon nut and bolt assemblies250for fixing to the wall mount bracket240. The wall mount assembly ensures the top surface of the tank remain horizontal.

Referring now toFIG. 20there is shown another embodiment of the containment tank300with internal structures. The horizontal lid is removed. The containment tank300comprises a first upper reservoir366and a second lower reservoir368separated by sloping plate312. The plate312has a sloped portion320and a horizontal portion324. The plate312has at least three apertures. Aperture343permits the end310of the venture tube304to penetrate the plate312and rise above the lid. Aperture322and aperture342surrounded by a standpipe340permits drainage of fluids from the top reservoir366to the bottom reservoir368. Piping assembly302comprising venturi pipe304and elbow306are located in the lower reservoir368of the containment tank300. The discharge end327of the elbow306penetrates wall314through aperture308. On the bottom inside surface326of containment tank300is an upwardly projecting baffle member328extending across the width of the tank. Depending down from the sloped section320of plate312is a second baffle330. The bottom331of the second baffle is above the surface326of the tank300thereby permitting water to move from bottom reservoir section330to the main section326.

Still referring toFIG. 20and also toFIG. 21the operation of the invention is explained.FIG. 21shows the duct housing350and the motor fan housing352mounted to a roof354. The exhaust outlet cowling356surrounds the fan and motor housing352. During operation significant amounts of grease and dirt will accumulate on the inside surface of the cowling356and on the fan blades360. Rain and moisture falling into the exhaust cowling will collect grease and dirt which will be drained off through the outlet362and into the containment tank300. The top reservoir of the containment tank366is sealed from the bottom portion368by the inclined separation plate320. The top reservoir366of the containment tank300has a capacity of about 1.3 gallons according to code and is intended to collect grease between scheduled cleanings of the fan assembly and the duct. The fluid draining into the top reservoir of the containment tank is an oil and grease/water mixture. The oil and grease will be floating on top of the water. As the fluid level in the upper reservoir366of the tank300rises, water will flow into the bottom reservoir368by way of aperture322; however, stand pipe340will prohibit the oil from entering into the lower reservoir of the containment tank. If the fluid level in the upper reservoir of the containment tank is excessive then grease and oil will overflow into the standpipe340and into the bottom reservoir368by way of aperture342and into the sump portion330instead of overflowing the tank and falling onto the roof of the building354.

During cleaning operations the exhaust cowling, the fan and motor housing and the fan blades will be thoroughly cleaned using high-pressure water, steam and degreasers. The contaminated solution will flow through outlet362into the tank top reservoir366and then into the bottom reservoir368. Since oils and grease are dissolved in the run-off it is necessary to purge the containment tank of the contaminated cleaning run-off. The top portion of the separating plate will be cleaned by degreasers and steam and that run-off will flow into the lower reservoir. To cleanse and purge the containment tank300a high-pressure water source351is attached to the top end312of the venturi pipe304. High pressure water is forced through the venturi304pipe and through the tapered opposite end of the venturi370. The water is then expelled out of the containment tank by way of elbow306and into a recirculating hose380. The high-pressure water flowing through the venturi nozzle210inFIG. 17creates a syphoning effect inside of the elbow306which will draw all of the fluid in the lower reservoir368out and into the recirculating hose. When the cleaning is finished, the water can be directed to a waiting mobile containment tank for further treatment and disposal.

The invention is defined by the following claims.