Liquid purification or separation – With heater or heat exchanger – With treating fluid addition
Patent
1991-04-15
1992-09-29
Dawson, Robert A.
Liquid purification or separation
With heater or heat exchanger
With treating fluid addition
210180, 210181, 210187, 210210, 210218, 210259, 55267, B01D 3325
Patent
active
051511762
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns a filter for continuous filtration of a liquid by means of at least one filter element particularly but not exclusively adapted to be used as a filter in a causticizing process.
Similarly to prior art filters, a filter according to the present invention includes a vessel containing the liquid to be filtered and gas in a space located above the liquid level, at least one rotatable filter element provided in the vessel and defining an inner space for filtrated liquid obtained by the filtration, a device for washing material separated from the liquid and deposited on the filter element, communication between said inner space of the filter element and an outlet from said vessel, and a separator connected to said outlet for separating the filtrated liquid and gas entrained therewith.
SUMMARY OF THE INVENTION
As distinguished from prior art filters a filter, according to the present invention is characterized in that for to provide the pressure differential necessary for filtration between the gas space of the vessel and the inner space of the filter element, means are provided outside the vessel for generating an overpressure in the gas space of the vessel and a lower pressure in the inner space of the filter element at least corresponding to the evaporation temperature of the filtrated liquid in order to keep the filtrated liquid in the state of evaporation in the separator, and in that the separator is provided with a device for cooling of the separated gas and with outlet means for discharging condensate obtained upon cooling.
According to the present invention, by providing said means for pressurizing and said separator with said cooling device and said outlet means for condensate a number of advantages are obtained. Thus, a higher concentration of filtrated liquid (filtrate) is produced because a substantial part of the washing liquid (water) supplied for the above-mentioned washing, which would otherwise dilute the filtrated liquid, is withdrawn by the condensation. Further, an improved separation of condensate and gas vapor is obtained, so that a smaller amount of gas has to be added to the filter system, which in turn reduces the risk of oxidation in the system of the medium passing through the filter system. In certain cases, condensate can be recycled to the washing device in which case it would not be necessary to supply washing liquid and this may also result in a simplified structure. Further, a greater capacity is produced because in a higher revolutionary speed of the filter element is possible.
In summary, the principal advantages of the present invention are optimum expulsion of gas from the filtrated liquid and also an optimum expelling of washing liquid.
One embodiment of the present invention also comprises a conduit between the gas space of the separator and the gas space of the vessel for recirculating gas to the gas space of the vessel, said gas conduit comprising said means for generating said overpressure and said lower pressure. This results in a simple embodiment for obtaining said overpressure and said lower pressure, and also a simple provision for mutal adaption, especially when in a development of this embodiment said pressure generating means is divided into at least two pressure generating means separated along the gas conduit, at least said means provided closest to the separator generating said lower pressure in said space within said filter element and a subsequent means increasing the pressure for obtaining the overpressure existing in the gas space of the vessel. In this last mentioned embodiment, prevailing atmospheric pressure may be preferably be at a point between said pressure generating means for obtaining said lower pressure and said overpressure, respectively. The higher concentration of filtrated liquid is also caused by a preferred embodiment wherein the filter element comprises at least one disc element mounted on a substantially horizontal shaft, and wherein said washing device is arranged for washing onl
REFERENCES:
patent: 4120787 (1978-10-01), Yargeau
patent: 4775484 (1988-10-01), Schmidt et al.
patent: 4931176 (1990-06-01), Guinara
Karlsson Hans A.
Larsson Per
Strid Kent
Dawson Robert A.
Millard W. L.
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