Gas separation – Deflector – Fixed gas whirler or rotator means
Patent
1994-06-23
1997-09-23
Weber, Thomas R.
Gas separation
Deflector
Fixed gas whirler or rotator means
B01D 4512
Patent
active
056699484
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The following invention relates to a cyclone, mainly for separating liquid from gas/vapour which is formed on pressure reduction of spent cooking liquid in connection with pulp production, comprising a casing, an inlet arrangement, a lower outlet line for liquid and an upper outlet line for vapour and gas, said inlet arrangement being connected to a supply line with a valve. The invention relates to a cyclone of the abovementioned type which is cost-effective and which can in a flexible manner be optimised with regard to different operating conditions. The invention also relates to a method for counteracting foam formation.
BACKGROUND OF THE INVENTION
Cyclones are used in the main for separating a liquid phase from a gas/vapour phase. In industry today, use is in general made of cyclones which are specially manufactured with regard to the operating conditions in which the cyclone is principally to work. This trend towards special manufacturing leads to a small batch size, which in turn gives rise to relatively high costs. Furthermore, cyclones known today are in most cases constructed in such a manner that they cannot be adapted to different operating conditions, at least not without a considerable effort, as a result of which they often, in the event of a change in the production process, come to be used in operating conditions which are not optimum.
GB-A-550260 and U.S. Pat. No. 3,516,551, for example, show that this last-mentioned problem has been known for a long time and that there is a number of proposals for solutions of said problem. Common to known solutions, however, is the fact that flow variations are compensated in direct connection with the inlet into the cyclone by, in the case of a small flow, reducing the flowthrough area in the inlet arrangement of the cyclone so that the inlet rate is kept almost constant in order to obtain an optimum separation and by, in the case of a large flow, doing the opposite. In the case of liquids with a tendency to foam, however, such a solution proves to have undesirable after-effects, since the regulation gives rise to a change in the flow pattern and causes a pressure drop which in turn, because of the vapour formation etc., leads to an uneven flow pattern in connection with the outflow inside the cyclone and is thus a cause of foam formation. Foam formation is very disadvantageous since it disturbs the flow conditions inside the cyclone and thus counteracts optimum operating conditions.
SUMMARY OF THE INVENTION
The aim of the following invention is to produce a cyclone which at least in the main eliminates the abovementioned problem, so that a cyclone is made available, with the aid of which it is possible in a flexible manner to adapt the inlet arrangement to prevailing operating conditions so that the outflow rate inside the cyclone can be optimised and that such an inlet arrangement is constructed in such a manner that it counteracts the appearance of foam.
The abovementioned aim is achieved with the aid of an inlet arrangement which consists of an exchangeable insertion pipe with essentially constant cross-sectional area, the length of which exceeds 1 meter. In the preferred case, the length of said insertion pipe exceeds 2 meters, and it has proved to be particularly advantageous in connection with pressure release of spent cooking liquid from a digester for pulp production if the insertion pipe has a length of between 2.5 and 3.5 m.
With the aid of a set of insertion pipes with different cross-sectional areas, that is to say in the preferred case different diameters, it is possible to select an insertion pipe which has a diameter adapted to the relevant operating conditions, so that an optimum inflow rate into the cyclone is obtained. Furthermore, it is brought about, owing to the length of the pipe, that is to say more than 1 meter, that the foam formation is reduced in connection with outflow from the pipe inside the cyclone, and that the foam which is formed all the same is, owing to the controlled inflow, "broken up"
REFERENCES:
patent: 3516551 (1970-06-01), Wallen et al.
patent: 3668838 (1972-06-01), McNeil et al.
patent: 3753336 (1973-08-01), Drew et al.
Perry's Chemical Engineers' Handbook, 6th Ed., McGraw Hill Book Company, 1984, pp. 18-73 and 20-83 to 20-88.
Brottg.ang.rdh Goran
Jansson Ulf
Kamyr AB
Weber Thomas R.
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