Cyclone degritter for solids liquids separation

#The present invention relates to hydrocyclones for separating solid from liquids and particularly to cyclones for degritting water used in applications such as laboratories, air conditioning systems, household use and the like.

#Cyclones are widely used for separating solids from liquids. A cyclone separator comprises a generally cylindrical/conical shell having a tangentially positioned inlet for fluid infeed and outlets for underflow and overflow. In the cyclone the fluid stream is forced to spiral inward and upwardly through a centrally located overflow outlet in the form of a purified liquid stream. The grit or heavy particles carried by the liquid are flung outward against the wall of the cone by reason of the vortex action and centrifugal force. The solids exit the cyclone through the apex of the cone as underflow. Ordinarily, a small perentage of the grit remains in the liquid spiraling inward and is carried with the overflow.

#Underflow solids collectors called grit pots are used in applications where the feed solid fraction expected to be classified to the underflow is relatively small and the continuous loss of liquid to the underflow is undesirable. Once the solid concentration in the grit pot reaches a level at which the overflow quality of the cyclone can be affected, the pot is purged.

#Preferred embodiments of the invention have been chosen for purposes of illustrating its principles in which:

#FIG. 1 is a perspective view partly broken away showing a preferred embodiment of cyclonic separator for degritting water in accordance with the present invention.

#FIG. 2 is a side elevation thereof partly in section for illustrating the interior arrangement of separators according to the invention.

#Referring now to the drawing, particularly FIGS. 1-5, a preferred embodiment of the cyclonic degritter assembly 10 according to the present invention includes a housing 12 having upper 14 and lower 16 housing members for encasing the cyclonic cartridge unit 18 and being particularly suited to household installation. The cyclonic degritter cartridge 18 is sealed within housing 12 with bottom and top gaskets 17. Feed inlet 19 and overflow outlet 20 openings are provided in upper housing member 14. The cyclone degritter cartridge within the housing includes a top closure 21, shell 22, together with a cyclone plate 24 interfacing and lying beneath a vortex finder plate 26. All parts of the cartridge 18 are assembled and held together mechanically or by adhesive. A plurality of conical cyclones 28, of suitable number of handle feed flow volume, depend from the cyclone plate into the interior of the shell defining the primary cyclones for removing grit from household water. The vortex finder plate is provided with a complementary number of vortex finders 30 aligned axially with each cyclone and defining upwardly open ducts 32 for carrying overflow from the cyclone to the clean water outlet. The cyclones include an open apex 34 for allowing grit separated from the water flow to be deposited in the bottom of the shell or grit pot 36 through downwardly extending tubes or baffles 38. These tubes direct separated solids toward the bottom of the grit pot reducing the opportunity of upward flow through the cyclone.

#In operation water infeed is directed to the tangential inlets 40 at the upper end of each cyclone at sufficient pressure and velocity so that the water flows in a vortex in the cyclone with the grit being removed by centrifugal force and the cleansed overflow issuing through the vortex finders and out of the cyclone degritter for household use. The descending grit forms part of the underflow which is deposited in the lower region of the grit pot.

#It is well known that cyclones operating with a grit pot suffer a loss of collection efficiency due to recycling of the underflow back into the body of the cyclone. According to the present invention, there is provided a bleed flow from the settled portion of the grit pot into the overflow. In one form of the invention, a bleed hole 42 is formed in the cyclone and vortex finder plates to provide for the bleed flow. The bleed hole is dimensioned to accommodate a very small bleed flow on the order of 2% to 8% of feed flow in the preferred embodiment. Preferably, the bleed flow is in the range of between 2% and 4% of feed flow. By this arrangement the grit pot is designed to function as a settling chamber so that the bleed flow exits the grit pot through the top, i.e., cyclone and vortex finder plates directly into overflow chamber 44 with as little solids as possible. Test results have determined that this very small settled bleed flow improves collection efficiency to 86% from 76% when a grit pot is used. The result accomplished by having this very small bleed flow is substantially the same as the operating efficiency of a cyclone degritter without a grit pot and also without a reduction of overflow occurring when grit pots are not used.