Liquid purification or separation – Filter – Movable medium
Reexamination Certificate
1998-12-03
2001-06-05
Cintins, Ivars (Department: 1724)
Liquid purification or separation
Filter
Movable medium
C210S390000, C210S398000, C422S261000
Reexamination Certificate
active
06241101
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an installation for separating and purifying solids from a suspension and/or for leaching out solid particles, containing:
a cylinder having a piston which is movable therein and which with a sealing part bears against an interior wall of the cylinder to provide a seal,
a filter which is connected to the piston and which delimits a washing column chamber located above the filter in the cylinder.
a feed line for feeding the suspension of the solid particles to the cylinder and
a discharge line for discharging the liquid from the washing column chamber after filtering through the filter.
An installation, or washing column, of this type is disclosed in Netherlands Patent Application no. 7 106 457 in the name of the Applicant. In said known installation, when the piston is in the lowermost position, the suspension of solid particles in a liquid is passed through the piston into the washing column chamber. A packed bed of particles, for example ice crystals, is located in the upper part of the washing column chamber. The piston is then displaced upwards until it comes into contact with the packed bed. During this operation the liquid is forced through the filter to a discharge line. The particles remain behind on the filter and add to the packed bed from the bottom. The packed bed is melted or scraped off at the top and the purified particles (ice crystals) are discharged from the washing column chamber.
A discontinuous piston washing column of this type has the disadvantage that the purification process is difficult to carry out on a large scale. Furthermore, the system of movable feed and discharge lines requires additional pneumatics and complex seals. Furthermore, it is difficult to scale up the known piston washing column.
SUMMARY OF THE INVENTION
An aim of the present invention is to provide a discontinuous packed bed washing column with which the purification process can be employed on a large scale and with which the number of moving parts is minimised.
To this end the installation according to the invention is characterised in that
the piston in the cylinder delimits a pumping chamber which is locate below the piston and into which the feed line opens,
wherein the filter is located some distance away in the axial direction from the sealing part of the piston so that a discharge chamber in the cylinder is delimited by the cylinder wall, the filter and the piston,
wherein a connecting channel which can be closed off connects the pumping chamber and the washing column chamber and
wherein the feed and discharge lines are at least virtually stationary with respect to the cylinder.
When the piston is in contact with the packed bed, the pumping chamber below the piston has filled with the suspension via the fixed feed line. For this operation the connecting channel between the pumping chamber and the washing column chamber is closed, for example via a non-return valve. The feed line is then shut off and the piston moves downwards in one pump stroke. For this operation the shut-off valve in the connecting channel is opened, so that during the compression stroke the suspension is transferred from the pumping chamber to the washing column chamber. The piston then moves upwards again towards the packed bed, the feed line and the discharge line being opened. The connecting channel is closed. The liquid from the suspension will be forced through the filter towards the discharge chamber, from where the liquid is able to flow away through the opened discharge line.
By use of the discharge chamber located between the filter and the piston and of the closable connecting channel between the pumping chamber and the washing column chamber it is possible for the feed and discharge lines to be attached to the cylinder in a fixed position. The advantages in respect of the ability to scale up the installation ensue from the fact that the diameter of the cylinder can be made many times larger, with only one fixed discharge line and one fixed feed line being required. The number of closable connecting channels can be increased independently thereof. Since there is still only one (rod) seal needed, said washing column can more easily be constructed to sanitary requirements. The risk of leakage to the outside (environment) and to the interior (air, sanitary requirements) is also appreciably less, as a result of which the need for filing under pressure can also be dispensed with.
Preferably, the discharge line opens into the discharge chamber, the distance between the filter and the piston being made such that the sealing part of the piston does not pass beyond the mouth of the discharge line when the piston is moved in the cylinder. In this way the liquid discharged via the filter during the compression stroke can be continuously removed from the discharge chamber.
However, although this is not to be preferred, it is also possible to fit the discharge line in an axial position such that said line is below the sealing part of the piston during the compression stroke. The discharge chamber will be filled during the compression stroke and will be emptied only when the piston has been moved down sufficiently for the discharge chamber to be re-connected to the discharge line. With this arrangement the volume of the discharge chamber must be made sufficiently large.
The connecting channel between the pumping chamber and the washing column chamber can be located in the cylinder, but can also run outside the cylinder in the form of a by-pass line. Preferably, the piston is constructed as a hollow body having an essentially conical wall and an open base. The filter is attached close to the top of the conical piston, where an opening is made in the cylinder wall which is closed off by a non-return valve. During the pump stroke, the suspension is directed in a streamline manner towards the opening. During this operation the liquid, such as water, is placed under pressure and the solid particles, such as ice crystals, are carried along to the washing column chamber.
If the solid particles are heavier than the liquid, the entire cylinder with the conical piston can be placed the other way up. During the cycle time of the washing column according to the present invention, which, for example, is one minute, the ice is able to float up or heavy crystals are able to settle out. The crystals or the ice must be transferred from the pumping chamber to the washing column chamber and must always be brought as close as possible to the non-return valve of the piston in order to ensure efficient removal from the pumping chamber. By placing the cylinder according to the invention the other way up for particles which are heavier than the liquid, said particles will always be located close to the non-return valve of the piston in the pumping chamber, so that blockage caused by these particles remaining behind is counteracted.
To prevent the packed bed from becoming disturbed during the pump stroke as a consequence of the introduction of the suspension into the washing column chamber, the valve is preferably of streamlined construction when an internal connecting channel is used. As a result of this the liquid flow is deflected in the horizontal direction during the pump stroke and the packed bed remains intact. The piston can be provided on the underside with ice-breaking elements, so that the piston movement is not blocked by ice formation during the pump stroke.
REFERENCES:
patent: 1509686 (1924-09-01), Morterud
patent: 3374052 (1968-03-01), Fan et al.
patent: 2 300 576 (1996-11-01), None
patent: 7 106 457 (1971-12-01), None
Cintins Ivars
Niro Process Technology B.V.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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