A Food Processing Gases Treatment Apparatus

Abstract

Gas treatment apparatus 12 has an inlet 24 receiving a stream of gases from a food-processing apparatus (10, Fig. 1) and an outlet 26 exhausting treated gases. A pump 36 transfers liquid from a reserv

Description

06 01 25 The present invention relates to a food processing gases treatment apparatus and relates particularly, but not 5 exclusively, to an apparatus for reduction or removal of odour by treating the gases and vapour produced as a biproduct of largescale factory frying, cooking and food processing. Odour and oil mist emissions from applications such as frying, cooking, coating and seasoning within the food industry 10 can cause major problems and lead to complaints to environmental and health regulators. Processes such as frying lead to the thermal breakdown of oil, the creation of acridity, ammonia or the breakdown of spices. Some of these biproducts are soluble in water, some will cool and condense and some require chemical 15 treatment for example by the application of acid or alkali. The problems caused by odour are subjective and different people will pick up different odours and have different threshold levels as to what is acceptable and what is not. Removing one identified compound or obvious smell will often unmask others 0 that had not been noticeable previously. This makes odour reduction and removal particularly difficult. These food preparation processes often produce sticky particulate, fat droplets and oil mist which are hard to filter with traditional methods and can coat nearby buildings and roofs. Oil mist in 25 ducts can cause hygiene and maintenance problems and uncontrolled oil mist can lead to a build-up of inflammable material with the inherent risk of fires. Existing systems typically only deal with one these problems. For example, packed towers and carbon filters or UV &Ozone cannot deal with the 30 level of sticky particulate, fatty or oily droplets. Similarly, fluidised liquid beds, impingement scrubbers or other particulate type wet scrubbers only remove the particulate and droplets but do not treat the gases produced in the cooking 06 01 25 processes. This in turn leads to the less effective removal of sub-micron particulates from cooking gas streams. Preferred embodiments of the present invention seek to overcome or alleviate the above described disadvantages of the 5 prior art. According to an aspect of the present invention there is provided a food processing gases treatment apparatus comprising: an inlet for receiving a stream of gases generated from a foodprocessing apparatus and an outlet for exhausting the gases once 10 treated, thereby creating a gas flow stream from said inlet to said outlet; at least one reservoir for containing a volume of liquid; at least one pump for transferring said liquid to and / or from said reservoir; 15 at least one perforated waterbath having at least one liquid input for receiving said liquid from said reservoir and at least one liquid output for directing the liquid to said reservoir, said perforations receiving the stream of gases such that the gases pass through the liquid in said waterbath; 20 at least one reaction pad located downstream of said waterbath, said reaction pad comprising a porous material and said stream of gases passing through said reaction pad; at least one reaction chamber located downstream of said reaction pad; 25 at least one mist eliminator located downstream of said reaction chamber, said mist eliminator comprising a porous material angled transverse to the direction of gravity when the apparatus is in use, such that said stream of gases passes therethrough; and 30 at least one drainage system for directing liquid from said mist eliminator back to said reservoir. 06 01 25 By providing a food-processing gas treatment apparatus including a reservoir and a pump, the advantage is provided that water can be recirculated which reduces the volume of liquid (primarily water) required to undertake the gas treatment 5 process and also allows for easier collection of contaminants such as oil for treatment. Furthermore, additives can be added to the water reservoir which can enhance the gas treatment process and recirculating water via a reservoir and a pump decreases the total amount of additive required to effectively 10 treat the gas. The use of the perforated waterbath assists in the breaking up of the gas stream into smaller streams which are each passed through the water contained in the waterbath. Using a multiplicity of perforations helps to increase the volume of gas in contact with the water and the resultant bubbling of the 15 water produces a water mist which enters and saturates the reaction pad. By having water in the reaction pad which creates multiple pathways for the gas to pass through thereby increasing the contact surface area of the water. By locating a reaction chamber between the reaction pad and the mist eliminator the 0 advantage is provided that further contact time between the gas been treated and water droplets is provided. By providing a mist eliminator which includes a pad similar to the reaction pad but which is angle relative to the force of gravity, the advantage is provided that the majority of the water droplets 25 in the stream of gas are collected and drain from the reaction pad. In a preferred embodiment the reaction pad is located in use above said waterbath. In another preferred embodiment the reaction chamber is 30 located in use above said reaction pad. In a further preferred embodiment the mist eliminator is located in use above said reaction chamber. 06 01 25 By locating the components of the present invention one above another the advantage is provided that water can be simply pumped from the reservoir into the waterbath and a combination of the energy from the stream of gases and the force of gravity 5 cooperate to move the water around the apparatus returning it to the reservoir for recirculation. The apparatus may further comprise at least one liquid return for collecting liquid from at least one of said waterbath, said reaction pad and said mist eliminator. 10 In a preferred embodiment the liquid return comprises a double barometric leg. By using a double barometric leg the advantage is provided that air is not drawn through the drains. The double barometric leg is a compact and simple way to enable the liquor to return 15 from the perforated plate and the mist eliminators without needing two systems. It is effective, simple and straightforward to keep clean. In a preferred embodiment the reservoir comprises an overflow leading to an oil separator. 20 In another preferred embodiment the reservoir further comprises at least one liquid additive dosing device for introducing an additive into the liquid in said reservoir. Including a chemical dosing device provides the advantage that the recirculated water efficiently removes the contaminants 25 from the gas stream in a manner that allows the repeated use of the water before it needs to be replaced. The apparatus may further comprise at least one activated carbon filter located downstream of said mist eliminator. The apparatus may further comprise at least one coalescing 30 filter located downstream of said mist eliminator. 06 01 25 In a preferred embodiment the coalescing filter is located between said mist eliminator and said activated carbon filter. In another preferred embodiment the at least one of said reaction pad and said mist eliminator comprises at least one 5 fibre pad. In a further preferred embodiment the fibre pad comprises at least one metal fibre. The reaction pad may be positioned relative to a fill level of the waterbath so as to ensure that in use the reaction pad 10 remains saturated with water. According to another aspect of the present invention there is provided a food-processing apparatus comprising: a food cooking apparatus producing by-product gases; a gas extraction apparatus for directing said by-product gases 15 into a stream of gases; and a gas treatment apparatus for receiving and treating said stream of gases as set out above. In a preferred embodiment the food cooking apparatus comprises at least one fryer for cooking food in heated fat. 20 Preferred embodiments of the present invention will now be described, by way of example only, and not in any limitative sense with reference to the accompanying drawings in which: Figure 1 is a schematic representation of a food-processing an apparatus of an aspect of the present invention; 25 Figure 2 is a sectional view of a food processing gases treatment apparatus of another aspect of the present invention; Figure 3 is a close up view of a portion of the apparatus of figure 2; and Figure 4 is a close up view of another portion of the apparatus 30 of figure 2. Referring to figure 1, a food-processing apparatus 10 includes a food-processing gases treatment apparatus 12 for treating gases, indicated schematically at 14, generated from a food-processing apparatus, indicated schematically at 16. A 5 gases collecting hood 18 is connected to ducting 20 and a fan 22 generates a stream of the food-processing gases 14. With additional reference to figures 2 to 4, the ducting 20 is connected to an inlet 24 of the food-processing gas treatment apparatus 12 which also has an outlet 26 for venting the treated 10 gases to the atmosphere via a chimney 28. The flow of gases from the inlet 24 to the outlet 26 defines a stream of gases, the inlet 24 at the most upstream end of the food-processing gases treatment apparatus 12 and the outlet 2 6 at the most downstream and of that apparatus. 15 LO CM The food-processing gases treatment apparatus 12 includes a reservoir 30 for containing a volume of a liquid (primarily water). The reservoir 30 has a water inlet 32 which allows top up water to be added to the reservoir as it is needed. A pumped outlet 34 draws water from the reservoir 30 and, using a pump 36 via pipework 38, transfers water from reservoir to the remainder of the food-processing gases treatment apparatus 12. It should be noted that reference to upstream and downstream within this application is made to the direction of the flow of gases and not to the flow of water. As seen from the description 25 below, once the water has left the pipework 38 the flow of water is generally in the opposite direction to the flow of the stream of gases. A waterbath 40 is provided with a perforated base 42 and a portion of the water flowing through pipework 38 is directed 30 into the waterbath 40 via waterbath inlet pipes 44 which contain a series of holes 46. When in use, the stream of gases for treatment pass through the perforations in the base 42 of the waterbath 40 which mixes the gases with the water and significantly slows the draining of the water from the waterbath. As the stream of gases bubbles through the water the mixing of the gas and the water not only begins the process of water-soluble gases being dissolved into the water but also 5 generates water spray which further mixes with the stream of gases being treated. Above, and therefore downstream of, the waterbath a reaction pad 48 is provided. The reaction pad 48 is porous and is in the form of a mat of fibres which can include, but are not 10 limited to, steel wires, glass fibre, Polyester, Polypropylene, galvanised wire and PTFE. The purpose of the reaction pad is to ensure thorough mixing of the stream of gases with the water spray from the waterbath. As a result, other forms of porous reaction pad are suitable for use including, but not limited to, 25 stacked layers of mesh such as steel mesh. Above, and therefore downstream of, the reaction pad is a mist eliminator 50 for removing larger droplets of the water mist which have escaped the reaction pad 48, together with entrained particulates, fats and oils. The mist eliminator 50, like the reaction pad 48, is a porous material and is also in the form of a mat of fibres. The material chosen for the mist eliminator can be the same as or can be different from the material used in the reaction pad. The mist eliminator is in two parts which, when the apparatus is in use and as shown in the figures, are transverse with respect to the force of gravity (acting downwards as shown in the figures) that is, the pads of the mist eliminator are neither parallel to nor perpendicular to the direction of the force of gravity and in the embodiment shown resemble a pitched roof with an angle approximately 30° to the horizontal. Located between the reaction pad 48 and the mist eliminator 50 is a reaction chamber in the form of a void 52. This void allows continued mixing of the stream of gases with the water mist before the mixed stream of gases and water contacts the mist eliminator. The combination of reaction pad 48 and mist eliminator 50 are formed from materials which provide temperature and chemical resistance whilst maintaining an 5 acceptable, that is not too great, pressure drop across the apparatus . Water from the mist eliminator 50, reaction pad 48 and waterbath 40 are returned to the reservoir 30 via a drainage system 54. Water from the mist eliminator 50 runs down a first 10 drainage surface 56 and between an outer wall of the apparatus 56 and a wall 58 of the waterbath 40 and into the drainage system 54. The waterbath 40 contains a drain 60 which also runs into the drainage system 54. Water from the first drainage surface 56 and from the bath drain 60 run into a trough 64 which fills 25 with water and has an overflow 66 for returning water to the reservoir 30. These two inputs into the trough create a double barometric leg which ensures that air is not drawn through the drains. This is required because a fan 67, on the discharge side of the apparatus, generates a negative pressure and if there was not a barometric leg it would allow the air to rush up the drains and bypass the treatment area. The double barometric leg is a compact and simple way to enable the liquor to return from the perforated plate and the mist eliminators without needing two separate return systems. It provides and effective and simple water return system which is also straightforward to keep clean. Returning to the reservoir 30, which is shown most clearly in figure 4, as well as the pump outlet 34 the reservoir is provided with other outlets including an oil drain 68 which is 30 fed from an oil sump (or separator) 7 0 which in turn receives water from an overflow 72 of the reservoir 30. In the example shown in figure 4 the oil sump 70 is shown on the left-hand side of the reservoir 30 and is therefore below one of the trough overflow 66 of the drainage system 54. As a result, a deflector plate 74 is located over the oil sump 72 to direct the flow of water from the trough overflow 66 directly to the reservoir 30. Further outlets of the reservoir 30 are a pair of drainage 5 outlets 76 and 78 which are provided to allow complete draining of the reservoir 30 and the oil sump 70 respectively. A dosing device, indicated schematically at 80, is provided to add treatment chemicals to the water as it leaves the reservoir 30 via pipe 34. This avoids problems of incorrect concentrations 10 (both too high and too low) due to insufficient mixing. Examples of additives include, but are not limited to, sodium hydroxide and sodium hypochlorite. In addition to the water inlet pipe 44 for the waterbath 40 an additional water input to the apparatus from the pipework 25 38 and before the waterbath is from sprays mounted on a pipe 82. This is used to spray water onto the underside of the perforated base 42 of the water bath 40. The purpose of the spray is to remove and / or prevent any build-up of contaminants such as grease and fats thereby dislodging any solids which attach to the underside of the water bath and washing them into the reservoir. An access hatch 83 is also provided allowing inspection of the base plate 42 of the water bath 40 as well as other components associated with the reservoir 30. An electrical interlock is provided on the door of access hatch 83 which cuts power to the gases treatment apparatus 12 if the door is opened. Located adjacent the inlet 24 is a spray nozzle 85 which sprays a mist of water which cools and condenses gases in the gas stream prior to entering the main chamber. This improves 30 efficiency and acts as a fire barrier in the event of a fire in the duct 20. Located above, and therefore downstream of, the mist eliminator 50 is a coalescing filter 84 for further removal of water. Located above, and therefore downstream of, the coalescing filter 84 is an activated carbon filter 86 for further treatment of the stream of gases. Operation of the apparatus will now be described. Gases 5 14 produced by the cooking process, which can include but is not limited to frying, baking and broiling, on the cooking apparatus 16 are drawn into the hood 18 by the fan 22. The stream of cooking gases thus created is directed through the ducting 20 to the inlet 24 where it passes over the reservoir 30 and is 10 contained within the external walls 58 of the apparatus. The only way for the stream of cooking gases to exit the apparatus is via the outlet 26 which requires the gases to pass through the perforations and the base 42 of the waterbath 40, through the reaction pad 48, the reaction chamber 52, the mist eliminator ^15 50, the coalescing filter 84 and the activated carbon filter 86. LX) C\J The stream of gases passes through the mist created by the outlets in pipe 82 and then through the perforations in the base 42 of the waterbath 40. The holes 46 in waterbath inlet pipe CO 44 ensure a continual flow of water enters the waterbath. Some ¢-^20 of this water runs through the apertures in the perforated base 42 but the pressure created by the stream of cooking gases prevents much of this water from running through the perforations. As a result, gases bubble through the waterbath which is filled to a height which reaches the bottom of the 25 reaction pad 48. As the stream of gases passes through the water in the waterbath the bubbling effect generates a mist and larger droplets which pass into the pores in the reaction pad 48. As a result, the reaction pad becomes saturated with water and the 30 separated streams of gas are forced into multiple contacts with the water ensuring maximum opportunities for contact between the water and the stream of cooking gases. As the gases pass through the upper surface of the reaction pad 48 the mist of droplets enters the reaction chamber where there is further opportunity for mixing of the mist droplets with the stream of cooking gases thereby increasing the likelihood of any components of the stream of gases which are water-soluble or soluble in the mixture 5 of water and additives to be extracted from the stream of gases into the water for treatment and disposal. The stream of gases and droplets of mist then pass through the mist eliminator. The porous nature of the fibres that form the mat of the mist eliminator encourage the mixing and collision 10 of the water droplets which accumulate to form larger droplets too large to be carried in the stream of gases. As a result, these drops of water run down through the mist eliminator 50 to the drainage surface 56. The stream of gases exit the mist eliminator 50 and pass LO 5 through the coalescing filter 84 which further reduces the water C\J content from the gases. Before exiting the apparatus via the outlet 26 the gases finally pass through the activated carbon filter 8 6 which reduces the odour from components of the gas CO stream which are not soluble in water or the combination of ¢-^2 0 water and additive. The water, mixed with dissolved components of the stream of cooking gases which are collected from the mist eliminator 50 onto the first drainage surface 56, runs between the inside of the outer wall 58 and the outer surface of the bath wall 60 25 of the waterbath 40 and into the trough 64 of the drainage system 54. Also entering the trough 64 is water draining from the waterbath 40 via the bath drain 62. This drain is sized to ensure a continuous flow of water through the waterbath whilst maintaining the depth described above. The water draining from 30 the mist eliminator 50 and the waterbath 40 that together enter the trough 64 flows over the trough overflow 66 and returns to the reservoir 30. - 12 - Oils and fats which are mixed into the water in the reservoir 30 will tend to float and by occasionally increasing the volume of liquor (water and perhaps including one or more additives) in the reservoir via the water inlet 32 these floating 5 oils and fats will tend to run over the reservoir overflow 72 and into the oil sump 70. Because the deflector plate 74 prevents water draining from the trough 64 from directly entering the oil sump 70 and is protected from the stream of gases entering from the inlet, the water in the sump is agitated 10 much less than the water in the reservoir thereby allowing the fats and oils to separate from the water more fully. These fats and oils can then be drawn off this water via the oil drain 68 for treatment or disposal. When periodic cleaning of the apparatus is required all of the contents of the reservoir 30 15 and oil sump 70 can be drained through the respective drainage i n / outlets 76 and 78. CM The apparatus described above is designed to be a Clean in Place (CIP) system. In many food factory frying and cooking applications fat and grease build on the ducts and has to be ^*^2 0 cleaned off as it presents a fire risk, especially on frying applications. As a result, a CIP system is installed on the ducts to spray the insides with hot caustic solution and clean the ducts when the fryer is being cleaned. The apparatus described above includes, as part of its 25 control system, an automatic clean cycle, leaving the reaction pads and mist eliminators in place. As a result, the hygiene or cleaning teams do not have to open the access doors and manually clean very often (although regular checks are still recommended) . Hot water being used to clean the fryer is 30 transported to the scrubber via CIP duct nozzles, although could be pumped, it is then mixed with caustic (which can be manually or automatically added). The control system controls the cleaning steps and recirculates the liquor around the scrubber to clean it and then discharges it. The ducts and other parts cleaned are then flushed and rinsed with fresh water to clean debris and liquor from the scrubber after which the bath automatically fills with water and the system is ready for use. 5 It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the protection which is defined by the appended claims. For 10 example, in the embodiment set out above and shown in the figures the various major components of the apparatus are stacked one on top of the other. This is the most logical arrangement for these components particularly those where water drains as this ensures the shortest path draining and gravity for water to LO 15 return to the reservoir. However, alternative configurations CM most notably where the coalescing filter and activated carbon filter are not located directly above the other components are perfectly acceptable. Furthermore, the coalescing filter and activated carbon filter can be replaced with other components. It is also the case that the coalescing filter and activated carbon filter could be removed for some applications where the other components provide sufficient odour removal from the stream of cooking gases. With similar regard to the arrangement of components it is possible that the reservoir can be located 25 elsewhere and indeed the feed from the reservoir to the waterbath can be utilising gravity with the water being pumped back up to the reservoir. Apparatus of this sort is also suitable for use in the treatment of gases produced in the manufacturing of textiles, paper, cardboard, plastics and rubber. Furthermore, 30 chemical processes that drive off ammonia, organic and inorganic acids, alkalis and water soluble solvents can also be treated using the process of the present invention as well as gases and odours produced by some recycling plant processes. 06 01 25

Claims

1. A food processing gases treatment apparatus comprising:an inlet for receiving a stream of gases generated from a foodprocessing apparatus and an outlet for exhausting the gases once 5 treated, thereby creating a gas flow stream from said inlet to said outlet;at least one reservoir for containing a volume of liquid;at least one pump for transferring said liquid to and / or from said reservoir;10 at least one perforated waterbath having at least one liquid input for receiving said liquid from said reservoir and at least one liquid output for directing the liquid to said reservoir, said perforations receiving the stream of gases such that the gases pass through the liquid in said waterbath;15 at least one reaction pad located downstream of said waterbath, said reaction pad comprising a porous material and said stream of gases passing through said reaction pad;at least one reaction chamber located downstream of said reaction pad;20 at least one mist eliminator located downstream of said reaction chamber, said mist eliminator comprising a porous material angled transverse to the direction of gravity when the apparatus is in use, such that said stream of gases passes therethrough; and25 at least one drainage system for directing liquid from said mist eliminator back to said reservoir.

2. An apparatus according to claim 1, wherein said reaction pad is located in use above said waterbath.

3. An apparatus according to claim 1 or 2, wherein said 30 reaction chamber is located in use above said reaction pad.06 01 254. An apparatus according to any preceding claim, wherein said mist eliminator is located in use above said reaction chamber.

5. An apparatus according to any preceding claim, further comprising at least one liquid return for collecting liquid from 5 at least one of said waterbath, said reaction pad and said mist eliminator .

6. An apparatus according to claim 5, wherein said liquid return comprises a double barometric leg.7 . An apparatus according to any preceding claim, wherein said 10 reservoir comprises an overflow leading to an oil separator.8 . An apparatus according to any preceding claim, wherein said reservoir further comprises at least one liquid additive dosing device for introducing an additive into the liquid in said reservoir .15 9. An apparatus according to any preceding claim, furthercomprising at least one activated carbon filter located downstream of said mist eliminator.

10. An apparatus according to any preceding claim, further comprising at least one coalescing filter located downstream of 20 said mist eliminator.

11. An apparatus according to claim 10, wherein said coalescing filter is located between said mist eliminator and said activated carbon filter.

12. An apparatus according to any preceding claim, wherein at 25 least one of said reaction pad and said mist eliminator comprises at least one fibre pad.

13. An apparatus according to claim 12, wherein said fibre pad comprises at least one metal fibre.

14. An apparatus according to any preceding claim, wherein said 30 reaction pad is positioned relative to a fill level of waterbathso as to ensure that in use the reaction pad remains saturated with said liquid.

15. A food-processing apparatus comprising:a food cooking apparatus producing by-product gases;5 a gas extraction apparatus for directing said by-product gases into a stream of gases; anda gas treatment apparatus for receiving and treating said stream of gases as set out in any of the preceding claims.

16. An apparatus according to claim 15, wherein said food10 cooking apparatus comprises at least one fryer for cooking food in heated fat.

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