Process for production of olive oil
The present invention concerns a process for production of olive oil comprising the following sequential steps: - the olives being crushed to obtain a fruit mash, which contains the liquid phases olive oil and water and a sludge phase,
- the fruit mash being kneaded,
- the kneaded fruit mash being fed to a decanter centrifuge having a screw conveyor inside a rotor for separating most of the water and the sludge from the olive oil, the sludge being discharged out of the decanter centrifuge through a sludge outlet by means of the screw conveyor and at least the olive oil phase being discharged out of the decanter centrifuge through a separate liquid outlet,
- the discharged olive oil phase being fed into an inlet of a centrifugal separator having a rotor forming a separation chamber provided with a stack of separation discs dividing the separation chamber inside the rotor into a number of interspaces, in which remaining water and sludge particles is separated out of the olive oil, the sludge particles being accumulated at a radial outermost part of the separation chamber, from which they are intermittently discharged by discharging at least partially the contents of the separation chamber through an outlet passage at the outermost part of the separation chamber, which can be opened and re-closed, a discharge of the accumulated sludge particles being initiated as often as needed, the separated water being accumulated in a radial layer radially inside the accumulated sludge particles, from which the separated water is discharged through a channel leading to a central water outlet connected to a water outlet conduit, the clarified olive oil being accumulated in a radial layer radially inside the layer of the accumulated water, from which the clarified olive oil
is discharged through a central olive oil outlet located radially inside the water outlet and further out through an olive oil outlet conduit,
In IT 675 801 a process of this kind is disclosed. When the sludge is discharged intermittently out of the centrifugal separator in this process valuable oil present in the separation chamber is lost together with the sludge. To prevent this it is a well-known possibility to supply displacement water to the separation chamber pressing the oil in the separation chamber radially inwardly to the central olive oil outlet and further out through the outlet conduit for the clarified olive oil. However, the oil pressed out of the rotor in this way is contaminated by displacement water and therefore it ought not be mixed with the clarified oil.
Another process of this kind is disclosed in EP 557 758. Also in this process there is a problem to avoid the loss of oil together with the intermittently discharged sludge or to avoid contamination the clarified oil.
The object of the present invention is to decrease the loss of valuable olive oil in a process of this kind together with the intermittently discharged sludge particles without increasing the risk of having water contaminated olive oil leaving the process through the outlet for the clarified olive oil.
According to the present invention this is achieved by following a procedure for an initiated discharge of accumulated sludge particles comprises the following sequential steps: - a valve in the olive oil outlet conduit and a valve in the water outlet conduit being closed,
- opening a valve in a re-circulation conduit connecting the olive oil outlet upstream of the valve in the olive oil outlet conduit with a passage for the olive oil in the process located upstream of the inlet of the of the centrifugal separator having said rotor provided with the stack of separation discs,
- an amount of displacement water being supplied to the separation chamber displacing the layer of separated olive oil radially inwardly and gradually forcing olive out of the rotor through the re-circulation conduit, - the supply of displacement water being stopped when this amount of displacement water has been supplied to the separation chamber,
- the outlet passage for the sludge particles being opened for a short period of time for the discharge of at least a portion of the contents of the separation chamber including the accumulated sludge particles, - then the outlet passage for the sludge particles being re-closed,
- the valve in the water outlet conduit being re-opened, and
- the valve in the olive oil outlet conduit is re-opened.
Hereby, the olive oil content in the separation chamber is pressed back to the process when the discharge of accumulated sludge particles is initiated instead of being lost together with the sludge particles.
■ In a preferred embodiment of the invention the initiated discharge of accumulated sludge particles is started by interrupting the supply of the olive oil to the centrifugal separator having the rotor provided with the stack of separation discs before the valves in the olive, oil conduit and the water outlet conduit are closed and the supply of olive oil is resumed when the valve in the water outlet conduit is re-opened.
Preferably the entire content of the separation chamber is discharged together with the discharge of the accumulated sludge particles.
The water is preferably supplied to the separation chamber at predetermined flow rate during a predetermined time period.
As alternative displacement water can be supplied to the separation chamber until a sensor arranged in the re-circulating conduit indicates that the liquid flowing through this conduit contains mainly water. This indicates that all the olive oil in the separation chamber has been recirculated.
In a special embodiment of the invention the olive oil is re-circulated to an intermediate tank arranged in the process between the decanter centrifuge and the centrifugal separator having the rotor provided with the separation discs.
In another embodiment of the invention is the valve in the re-circulating conduit kept opened and the valve in the olive oil outlet is kept closed for a time period after the valve in the water outlet is re-opened and not reopened until a sensor arranged in the re-circulating conduit indicates that there is no water in the re-circulating olive oil.
In the following the present invention is described in more detail with reference to the attached drawing, on which
figure 1 schematically shows a process for production of olive according to one embodiment of the present invention,
figure 2 schematically shows a process for production of olive oil according to another embodiment of the present invention, and
figure 3 schematically shows a cross section of a rotor of a centrifugal separator used in a process for production of olive oil according to the present invention.
In the process shown in figure 1 the olives are supplied to the process with or without stones at the intake 1 and are washed with water in the washer 2. The washed olives are crushed in a mill 3 and the obtained fruit mash is kneaded in a so-called malaxer 4. The kneaded fruit mash, which contains the liquid phases olive oil and water and a sludge phase, is supplied to a decanter centrifuge 5 having a screw conveyor 6 inside the rotor. In the decanter centrifuge 5 most of the water and the sludge is separated from the oil. The separated sludge is discharged out of the decanter centrifuge 5 through a sludge outlet 7 by means of the screw conveyor 6, which is rotated at rotational speed, which differs from the rotational speed of the rotor. At least the separated olive oil is discharged out of the decanter centrifuge through a separate liquid outlet, an olive oil outlet 8. Most of the water is preferably discharged through a separate liquid outlet, a water outlet 9 as shown in figure, but might also be discharge together with the sludge.
The olive oil discharged out of the decanter is supplied to the decanter centrifuge 5 is supplied to a centrifugal separator 10 via an intermediate tank 11. The centrifugal separator 10 has a rotor, which forms a separation chamber provided with a stack of separation discs dividing the separation chamber into a number of interspaces. Water and sludge particles remaining in the olive oil are separated out of the olive oil mainly in these interspaces. The sludge particles are accumulated at the radial
outermost part of the separation chamber formed in the rotor. The accumulated sludge is intermittently discharged by discharging at least partially the contents of the separation chamber through an outlet passage at the outermost part of the separation chamber, which can be opened and re-closed, a discharge of the accumulated sludge particles being initiated as often as needed. The outlet passage is connected to a conduit 12
The separated water is accumulated in a radial layer radially inside the accumulated sludge particles. From this layer the separated water is discharged through a channel leading to a central water outlet connected to a water outlet conduit 13 provided with a valve 14.
The clarified olive oil being accumulated in a radial layer radially inside the layer of the accumulated water, from which the clarified olive oil is discharged through a central olive oil outlet located radially inside the water outlet and further out through an olive oil outlet conduit 15 provided with a valve 16. The clarified oil is stored in a tank 17. Upstream of the valve 16 in the olive oil outlet conduit 15 a re-circulation conduit 18 is connected to the olive oil outlet conduit 15 in order to conduct liquid present in the olive oil outlet conduit 15, when the valve 16 in the olive oil outlet conduit is closed, to a passage for the olive oil located upstream of the inlet 19 of the centrifugal separator 10. The re-circulation conduit 18 is also provided with a valve 20.
A conduit 21 provided with a valve 22 is connected to the supply of displacement water to the separation chamber formed in the rotor of the centrifugal separator 10.
When a discharge of the sludge accumulated in the centrifugal separator is initiated a sequence of steps, which according to the present invention comprises the following sequential steps:
- The valve 16 in the olive oil outlet conduit 15 and the valve 14 in the water outlet conduit 13 being closed,
- opening the valve 20 in the re-circulation conduit 18 connecting the olive oil outlet upstream of the valve 16 in the olive oil outlet conduit 15 with a passage 11 , which in this embodiment of the invention is the intermediate tank 11 , for the olive oil in the process located upstream of the inlet 19 of the of the centrifugal separator 10 having said rotor provided with the stack of separation discs,
- an amount of displacement water being supplied to the separation chamber displacing the layer of separated olive oil radially inwardly and gradually forcing olive out of the rotor through the re-circulation conduit 18, to the passage 11 which in this case is the intermediate tank 11 ,
- the supply of displacement water being stopped when this amount of water has been supplied to the separation chamber, - the outlet passage for the sludge particles being opened for a short period of time for the discharge of at least a portion of the contents of the separation chamber including the accumulated sludge particles,
- then the outlet passage for the sludge particles being re-closed,
- the valve 14 in the water outlet conduit 13 being re-opened, and - the valve 16 in the olive oil outlet conduit 15 being re-opened.
The embodiment of the process according to the invention, which is shown in figure 2, differs from the process shown in figure 1 in that there is no intermediate tank provided between the decanter centrifuge 5 and
the centrifugal separator 10 having the rotor provided with the stack of separation discs in the separation chamber and in that the re-circulation conduit conducts the liquid in the olive oil outlet to the washer 2 when the valve 16 in the olive oil conduit 15 is closed instead of conducting it to an intermediate tank.
In the following the sequence of steps for an initiated discharge of accumulated sludge particles is described in more detail with reference to figure 3.
A discharge of accumulated sludge is initiated when a predetermined amount of sludge has been accumulated, when the separation result indicates that the sludge should be discharged or at equal time intervals.
When the discharge is initiated the layer of accumulated sludge might have reached the radial level 23 and the interface between the layer of water and olive oil might be located at the radial level 24.
In a preferred embodiment of the invention the sequence of steps of the initiated discharge of accumulated sludge particles is started by interrupting the supply of the olive oil to the centrifugal separator having the rotor provided with the stack of separation discs before the valves 14 and 16 in the water conduit 13 and in the olive oil outlet conduit 15 respectively are closed. When the valve 14 I closed there is no flow of water through the channel leading to the central water outlet connected to the water outlet conduit.
Then the valve 20 in the re-circulation conduit 18 is opened. Thus, the olive oil outlet communicates with the re-circulation conduit 18. Thereafter, displacement water is supplied to the separation chamber 25
provided with the stack of separation discs 29. In the shown embodiments of the invention this is done via the inlet 19 by opening the valve 22 in the conduit 21 for the supply of displacement water.
Gradually, the supplied displacement water presses the the interface between the layer of water and olive oil radially inwardly and the olive oil is pressed out of the rotor via the paring device 26 in the olive oil outlet chamber 27 and further out through the olive oil outlet conduit 15 and the re-circulation conduit 18 to the passage for the olive oil in the process located upstream of the inlet 19 of the of the centrifugal separator 10 having said rotor provided with the stack of separation discs 29.
In the process according to figure 1 this passage consists of the intermediate tank 11 and in the process according to figure 2 the passage consists of the washer 2.
When a certain amount of displacement water has been supplied to the separation chamber 25 all olive oil in the separation chamber has been pressed out of the rotor. The displacement water is preferably supplied to the separation chamber at predetermined flow rate during a predetermined time period, which determines the amount of displacement water supplied to the separation chamber 25.
As alternative water can be supplied to the separation chamber until a sensor 30 arranged in the re-circulating conduit indicates that the liquid flowing through this conduit contains mainly water. This indicates that all the olive oil in the separation chamber has been re-circulated.
Then the outlet passage 28 at the outermost part of the separation chamber is opened for a short period of time and the contents of the
separation chamber 25 is at least partially discharged, preferably the entire content of the separation chamber 25 together with the accumulated sludge particles.
When wanted amount has been discharged the outlet passage is re- closed and the valve 14 in the water outlet conduit 13 is re-opened. Then the supply of olive oil is resumed.
When the valve 14 in the water outlet conduit 13 is re-opened the valve 16 in the olive oil outlet conduit 15 can be re-opened. However, it is preferred that the valve 20 in the re-circulating conduit 18 is kept opened and the valve 16 in the olive oil outlet 15 is kept closed for a time period after the valve 14 in the water outlet 13 has been re-opened and not reopened until a sensor 30 arranged in the re-circulating conduit indicates that there is no water in the re-circulating olive oil.