Immiscible liquids separation apparatus and method

An immiscible liquids separation apparatus (50) comprising: a vessel comprising a first separation chamber (66) and second separation chamber (72) being in first fluid communication with the first separation chamber (66), the first separation chamber (66) being situated above the second separation chamber (72); an inlet (52) arranged at the first separation chamber (66) to allow a liquid to flow into the vessel; a low-density liquid outlet (78) arranged on the second separation chamber (72) to allow low-density liquid separated from the liquid to be removed therefrom; and a high-density liquid outlet (60) arranged at the vessel to allow high-density liquid separated from the liquid to flow out of the vessel, and a corresponding method.

The present technique relates to the field of immiscible liquids separation. More particularly, it relates to immiscible liquids separation apparatus and methods, such as grease removal devices (GRD) and processes, and passive grease removal devices (PGRD) and processes.

Waste liquids, such as waste water, may comprise water as well as fat, oil and/or grease (FOG). Waste liquids separators are used in numerous industrial applications. FOG separators are widely used in Food Service Establishments (FSE), such as commercial and institutional kitchens, to separate FOG from waste water and/or to protect waste water (sewage) systems. They ensure free flow of waste water from kitchen equipment, such as sinks, and prevent grease accumulation and, thus, clogging of waste water pipes.

There are different approaches around the world for standardizing ratings and/or establishing performance requirements for grease separators.

A first type of grease separators, known as gravity grease separators, is usually large, installed outside underground and requires an extended time for grease separation (30 minutes or more). The gravity grease separation occurs owing to a difference in specific gravity between FOG and water.

A second type of grease separators, known as hydro mechanical grease separators, is usually compact, installed inside a building and requires less time than the first type. The hydro mechanical grease separation occurs due to several simultaneous actions: a difference in specific gravity between FOG and water, a hydraulic flow action, and/or other additional actions. This type is covered by PDI G101 standard, for example.

Even well-designed and properly installed grease separators are prone to failure if they are not adequately maintained. As an obvious result, a grease separator becomes unable to separate the FOG from the water owing to overloading, and, thus, passes fat, oil, grease and/or sediment downstream.

To avoid such problems, a company specializing in cleaning separators services may be engaged. This is necessary for large separators, may be an expensive approach.

Alternatively, the grease separator may be configured to remove grease automatically. Further, the grease separator may comprise a strainer basket to capture food debris with high separation efficiency.

Whereas PGRDs comprise a passive system for removing FOG from the waste water without moving parts, active GRDs (AGPRs) may comprise an active system, such as a partially submerged mechanical wheel or drum, driven by an electric motor, for removing FOG from the waste water.

A grease separator is usually placed a washing area of a kitchen, below a sink. However, when the grease separator is connected directly below the sink, a waste water flowrate into the grease separator is often fluctuating. A rinsing sink for dishes and cutlery is usually equipped with a shower head usually having a flowrate of 0.05 l/s to 0.15 l/s, whereas a pot-wash sink often has a removable overflow pipe vertically installed at a bottom of the pot-wash sink upward from a drain hole. Waste water flows over an upper edge of the overflow pipe into the installed grease separator. A length of the overflow pipe determines a steady height of a water level in the pot-wash sink. A small amount of water may flow from a water tap into the pot-wash sink in order to dilute the water with clean water. In this way, typically about 20 l to 30 l of water may be retained in the pot-wash sink. After removing of the overflow pipe, the water retained in the pot-wash sink flows into the grease separator at once. When the length of the overflow pipe is 100 mm, a sink discharge flowrate is 0.5 l/s to 1.3 l/s, depending on a type of trap and a size of drainage pipe. When a sink having a depth of 350 mm is completely filled with water and then drained, the sink discharge flowrate can achieve 2 l/s. Such a high sink discharge flowrate significantly reduces efficiency of water/FOG separation inside the separator. Therefore, some manufacturers install a flowrate damper (reducer) in the inlet pipe of the grease separator and, thus, reduce a maximum flowrate to 0.5 l/s, for example.

However, as the flow of the waste water into the separation apparatus may vary, there is a need for an improved separation apparatus and method.

At least some examples provide an immiscible liquids separation apparatus (50) comprising:

a vessel comprising a first separation chamber and second separation chamber being in first fluid communication with the first separation chamber, the first separation chamber being situated above the second separation chamber;

an inlet arranged at the first separation chamber to allow a liquid to flow into the vessel;

a low-density liquid outlet arranged on the second separation chamber to allow low-density liquid separated from the liquid to be removed therefrom; and

a high-density liquid outlet arranged at the vessel to allow high-density liquid separated from the liquid to flow out of the vessel.

At least some examples provide an immiscible liquids separation method comprising:

providing a vessel comprising a first separation chamber and second separation chamber being in first fluid communication with the first separation chamber, the first separation chamber being situated above the second separation chamber;

through an inlet arranged at the first separation chamber, allowing a liquid to flow into the vessel;

through a low-density liquid outlet arranged on the second separation chamber, allowing low-density liquid separated from the liquid to be removed therefrom; and

through a high-density liquid outlet arranged at the vessel, allowing high-density liquid separated from the liquid to flow out of the vessel.

FIG. 1illustrates example data from a flowmeter installed on an outlet pipe in a commercial kitchen that simultaneously takes waste water from two sinks.

One of the sinks is used for rinsing plates and cutlery, and the other sink is used for washing pots and pans. The graphs inFIG. 1show the dependence of monitored values of an immediate waste water flowrate and an accumulated, total waste water flow for the two sinks in dependence on the kitchen's operating time. The waste water flowrate is less than 0.05 l/s for most of the kitchen's operating time, and the discharged waste water accumulates to 600 l in 5.5 h.

FIGS. 2aand 2billustrate a cross-sectional side view and cross-sectional bottom view of the immiscible liquids separation apparatus50according to the embodiment of the invention, respectively.

The immiscible liquids separation apparatus50comprises a vessel, an inlet52, a low-density liquid (FOG) outlet78, and a high-density liquid (water) outlet60. The immiscible liquids separation apparatus50and/or its components may be made from metal, such as steel or stainless steel, or plastic, for example.

The vessel comprises a first separation chamber66and second separation chamber72. The vessel may be a housing54. The vessel may comprise one or more lids, such as removable lids55,56.

The first separation chamber66is situated above the second separation chamber72. The first separation chamber66may comprise a coarse filtration chamber62. The first separation chamber66may comprise a sloped bottom.

The second separation chamber72is in first fluid communication with the first separation chamber66.

The vessel may further comprise a high-density liquid (water) release chamber80. The high-density liquid (water) release chamber80may be in second fluid communication with the second separation chamber72. The high-density liquid release chamber80may comprise a vertical release shaft86designed to allow the high-density liquid (water) flowing out of the vessel to take fine silt comprised in the liquid out of the vessel. The vessel may further comprise a container58arranged to collect the low-density liquid (FOG) removed from the second separation chamber72.

The vessel may further comprise a sloped plate68arranged to form a/the sloped bottom of the first separation chamber66and/or to form a sloped ceiling of the second separation chamber72. The sloped bottom may comprise at least one hole70arranged at a low end of the sloped bottom to allow the first fluid communication at a first flow rate of the liquid (waste water).

The vessel may further comprise a vertical low-density liquid (FOG) gap75arranged between the first separation chamber66and second separation chamber72to allow the first fluid communication at a second flow rate of the liquid, the second flow rate being higher than the first flow rate of the liquid. The vertical low-density liquid (FOG) gap75may comprise a coalescent filter, for example removable coalescent filter88to increase agglomeration of droplets of the low-density liquid (FOG).

The inlet52is arranged at the first separation chamber66to allow a liquid (waste water) to flow into the vessel. The inlet52may be configured as a rotatable inlet, easing installation.

The low-density liquid (FOG) outlet78is arranged on the second separation chamber72to allow low-density liquid (FOG) separated from the liquid (waste water) to be removed the second separation chamber72. The vessel may further comprise a valve arranged at the low-density liquid (FOG) outlet78to enable or disable flow of the low-density liquid (FOG) out of the vessel. The valve may be a floating-ball valve78comprising a floating member configured to disable the flow of the low-density liquid (FOG) in case the high-density liquid (water) raises the floating member to a predetermined height.

The high-density liquid (water) outlet60is arranged at the vessel to allow high-density liquid (water) separated from the liquid (waste water) to flow out of the vessel. The high-density liquid (water) outlet60may be arranged at the high-density (water) liquid release chamber80.

Thus, waste water comprising two or more immiscible liquids of different densities, such as water (high-density liquid) entrained with oil, grease, fats (low-density liquids) and/or other particles, flows into the inlet52providing a passage into the housing54. The inlet52may be rotatable in order to ensure a variable connection in case of limited installation space in the kitchen. As described in more detail below, the immiscible liquids separate within the housing54. Whereas the less-dense liquid (material), e. g. fat, oil and grease, empties into container58, the more-dense liquid, e. g. water, is discharged from the outlet60. Silt, typically small particles of suspended solids, may accumulate at the bottom of housing54. The silt may be periodically discharged through a silt outlet57, if applicable.

Operation of the separation apparatus50will be described in greater detail with reference toFIG. 2a. A coarse filtration chamber62is defined between the housing54and a perforated plate63that may extend across the full width of the housing54. As waste water enters the coarse filtration chamber62through the inlet52, it passes through a filtering basket64, which filters out solid particles, such as food debris, undissolved fat and other suspended solids.

After passing through the filtering basket64, the waste water enters the first separation chamber66, defined by a control plate67, a sloped plate68and the housing54. Both control plates67and68may extend across the full width of the housing54. There are two exits from the first separation chamber66: over an upper edge69and through holes70, located at a lowest point of the first separation chamber66. A sloped plate68is angled downward to holes70. Small particles of suspended solids passing through the filtering basket64slide down the sloped plate68and fall through holes70to the bottom of the housing54.

At low waste-water flowrates, e. g. less than 0.04 l/s, into the first separation chamber66, all water flows through holes70into the second separation chamber72. A layer of separated oil appears on a free water level73. The separated oil remains in chamber66. The low waste-water flowrate constitutes most of the operating time separation apparatus as shown onFIG. 1, and, thus, promotes oil/water separation in the first separation chamber66. The separated oil can freely flow through the perforated plate63.

At zero waste-water flowrate, the level of waste water in the first separation chamber66decreases to a level74, which is at a same height as an outlet overflow edge85.

At high waste-water flowrate, e. g. more than 0.04 l/s, the waste water is not able to escape from the first separation chamber66only through the holes70. The waste-water level rises up to the upper edge69, and the waste water starts to overflow into the oil gap75. The oil gap75is defined between the housing54and the control plate67with a free opening into the second separation chamber72. The oil gap75keeps a specific amount of separated oil which can occupy the complete height of the oil gap75. This condition supports agglomeration of oil droplets when the separated oil from free water level73and other oily water from the first separation chamber66flow through the oil gap75. This coalescent effect may also be increased by inserting a coalescent filter, e. g. removable coalescent filter88, into the oil gap75.

The waste water passing through the holes70and the oil gap75enters the second separation chamber72which is defined by the sloped plate68, a control plate76and the bottom of the housing54. The control plate76may extend across the full width of the housing54. There are two exits from the second separation chamber72: through a floating-ball valve78and through a passage79, disposed between a bottom edge of the control plate76and the bottom of the housing54. The sloped plate68is angled upward from the bottom of the first separation chamber66towards the floating-ball valve78.

A weir plate82, which may extend across the full width of the housing54, defines a water release chamber80, along with the control plate76and the housing54. The outlet60is disposed through the housing54.

As more of the waste water enters the second separation chamber72, the oil rises. The flow through the second separation chamber72is set at a rate that allows the oil to separate from the water and float upwards towards and touching the sloped plate68, and then further float towards the floating-ball valve78.

The sloped plate68forces the oil to accumulate at the entry to floating-ball valve78. The floating-ball valve78uses a ball that floats at the interface between the high-density liquid (water) and the low-density liquid (oil). When the high-density liquid reaches a predetermined height, the ball rises to height which stops oil flow from the second separation chamber72to the container58.

As the water flows through the separation apparatus50, it has to rise above an outlet overflow edge85(top) of the weir plate82in order to exit the separation apparatus50. Accordingly, the water in the second separation chamber72attempts to rise to approximately the same height as the outlet overflow edge85is placed. As the top of the second separation chamber72is below the outlet overflow edge85, a hydrostatic pressure of an upwards force of the water pushes the separated oil at the top of the second separation chamber72through the floating-ball valve78. However, the water cannot pass through the floating-ball valve78, because the floating-ball valve78will stop its passage. Hence, once all of the separated oil, or FOG, is forced out of the second separation chamber72, the floating-ball valve78remains closed until more oil accumulates.

The separated water passes through the passage79, over the weir plate82and through the outlet60. The silt in the water tends to accumulate at the bottom of the housing54. A silt valve57, located at the bottom of housing54, may be opened periodically, and a flow of water out of the silt valve57flushes the silt out of the second separation chamber72.

As described above, the waste-water flowrate from the sink can vary from less than 0.05 l/s to 2 l/s. As shown inFIG. 1, peak flowrates appear during kitchen operation several times per day. In these cases, a dynamic effect of high waste-water flowrate may be used to take silt from the bottom of the housing54away through the passage79and further through the vertical release shaft86between the control plate76and the weir plate82. The higher the flowrate through the vertical release shaft86is, the greater the effect. At the flow velocity of 0.1 m/s through the vertical release shaft86, fine silt is taken off and away, and discharged over the outlet overflow edge85. In this case, the silt valve57may not need to be opened during daily maintenance.

FIG. 3illustrates a detailed cross-sectional side view of the vertical low-density liquid gap75according to the embodiment of the invention.

In operation, small low-density liquid droplets83, i. e. small oil droplets, can pass through the holes70or flow over the upper edge69into the vertical low-density liquid gap75. Separated low-density liquid from the free high-density liquid level73, free water level, can only pass over the upper edge69into the vertical low-density liquid gap75. The vertical low-density liquid gap75supports agglomeration of the low-density liquid droplets into compact low-density liquid layer that occupies the whole space between the control plate67and housing54. Waste water escaping from the vertical low-density liquid gap75tears a lower partition of the vertical low-density liquid gap75into big droplets84that enter the second separation chamber72. Just a small amount of low-density liquid droplets83flows through the holes70. As big low-density liquid droplets can easier separate from the liquid, separation efficiency in the second separation chamber72is higher.

FIG. 4illustrates a detailed cross-sectional side view of the vertical low-density liquid gap75according to the other embodiment of the invention.

The coalescent filter is prone to clogging. However, the function of the vertical low-density liquid gap75may be improved by using a removable coalescent filter88. The removable coalescent filter88may be removed from the vertical low-density liquid gap75and cleaned externally.

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