JPH0470931B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for recovering the loss of overcapacity that occurs when a porous membrane is used as a material. More specifically, the present invention relates to a method for recovering the loss of capacity of wood that occurs when wax content is removed by passing through edible oil. The object of the present invention is to complete a method for quickly, easily, and completely recovering the reduction in overcapacity caused by the accumulation of wax content. Currently, in the refining process of vegetable liquid oil, the waxes contained therein are removed by passing it through a precoat filter using a supernatant. To be more specific, vegetable crude oil is rapidly or slowly cooled to precipitate wax, and then passed through a filter press pre-coated with a supernatant to obtain dewaxed oil. The filter leaf board is often clogged with wax, and the filter leaf board must be cleaned several times a day, and the super-aid containing a large amount of wax and neutral oil must be disposed of. When restarting the process, a new precoat layer must be made and filtration must be started, resulting in considerable time and loss of new supercoat. Even in porous membrane (hereinafter referred to as ``membrane'') dewaxing processes, the accumulation of wax on the membrane surface during the dewaxing process results in a significant decrease in overspeed, so it is necessary to clean or restore the membrane surface at regular intervals. Some means must be taken to improve the permeation flow rate. Wax adhering to or depositing on the membrane surface becomes more difficult to separate from neutral oil due to a decrease in viscosity at low temperatures, such as during wintering. The inventors of the present invention have investigated ways to quickly and easily recover from the decrease in overcapacity as described above, and have found that wax crystallized at low temperatures can be
During the filtration process, it adheres to the membrane surface and forms a layer with a certain thickness, but this wax layer is flushed or backwashed (in the case of oil, use oil or gas from the permeate side to the raw liquid side). In particular, the present invention was completed based on the knowledge that the membrane surface and permeation flow rate at the initial stage of use can be restored. That is, in the process of filtering fats and oils containing wax through a porous membrane to separate and remove the wax, the present invention involves blowing and removing the stock solution accumulated in the module with compressed gas, and then removing it from the membrane and the permeate. A method for restoring the filtration ability of a porous membrane, which is characterized by performing backwashing from the liquid side to the raw liquid side using compressed gas, and the present invention also provides a method for recovering the filtration ability of a porous membrane, which is characterized by performing backwashing from the liquid side to the raw liquid side using compressed gas. This method is characterized by combining backwashing with oil. In the present invention, the gas or oil used for backwashing is desirably in a temperature range that can dissolve wax, and is optimally at room temperature or above 40 to 100°C. It goes without saying that even if the temperature of the gas or oil is not necessarily high (even room temperature), it plays an effective role in wax removal and blowing operations. The inert gas used is generally nitrogen gas,
Carbon dioxide gas, dry air, etc. are the cheapest and can be used in large quantities. When using oil, it is possible to use the excess oil at room temperature, but if it is heated to the melting temperature of the wax, a better backwashing effect can be obtained. When heated oil is used, there is a flushing effect when using the external pressure/internal pressure backwash method. Also, when backwashing with compressed gas and backwashing with heated oil are performed in combination, the frequency of backwashing with compressed gas is higher than the frequency of backwashing with heated oil, and the frequency of backwashing with compressed gas is higher than the frequency of backwashing with heated oil. Preferably, the interval is shorter than the interval between backwashes with heated oil. Next, conditions during recovery (backwashing) will be described. When trying to clean the membrane surface where wax has accumulated so that the flow rate can be restored to the original, the backwash pressure of gas or liquid (oil) should be 0.5 to 10 kg/ It is convenient within ^cm2 .
When carrying out the process, the feed of the undiluted solution is stopped and the undiluted solution that has accumulated inside the module is expelled through the special blowing piping. At this time, the wax attached to the membrane surface is left intact. The important point is to maintain a stable condition. If backwashing is performed without removing the stock solution accumulated inside the module, the wax content attached to the membrane surface will dissolve into the stock solution, making it impossible to recover the wax content as a by-product in a highly pure state. However, if the undiluted solution accumulated in the module is removed and then backwashed, the wax adhering to the surface of the membrane will be recovered as is, making it possible to obtain highly pure wax. I can do it. When most of the neutral oil has been blown out, by applying reverse pressure from the permeate side to the non-permeate side using gas (N ₂ ) or liquid (dewaxed oil),
Wax or impurities stuck to the membrane surface can be peeled off, and then the peeled wax can be blown off with gas or oil from the other blow pipe for cleaning. By repeating these operations, the
This allows the dewaxing process to continue without human intervention. Note that the quality of the dewaxed oil produced by such a method is better than that of the conventional method. The effects of the method of the present invention are as follows. It is expected that the yield will improve. Under the current method for sunflower oil, it is impossible to recover it as pure wax, and the entire amount, including the neutral oil, is disposed of along with the filter aid, but with the membrane dewaxing method, there is less loss of neutral oil. Since the wax can be separated relatively easily, this has a great effect on the production process. There is no need for super-aiding agents, and the cost of purchasing super-aiding agents is eliminated. Separated crude wax can be used in cosmetics and other products, opening up its applications as high value-added products. All dewaxing work will be automated and throughput will be improved. The quality of dewaxed oil improves. Example 1 Figures 1 and 2 are explanatory diagrams of membrane dewaxing by the total filtration method. The structure was such that the stock solution was supplied from the outside of the membrane, and when external pressure was applied, the liquid came out from the inside, so that impurities such as wax would adhere to the outside of the membrane. To describe an example of dewaxing sunflower oil, first, a sunflower stock solution (using bleached oil) that has been rapidly cooled to below 10°C is supplied from a stock solution supply tank A to a supply pump _P1 , and a module M schematically represents a membrane. Oil is sent to At this time, only the supply side valve 1 and the liquid outlet B valve 2 are opened, the others are fully closed, and overwork is performed at an overpressure of 0.5 to 3 kg/cm ² . After about 1 to 2 hours, the overspeed will be 50% of the initial speed.
Cleaning (backwashing) of the membrane as it drops below
Switch to work. At this time, the supply pump P ₁ and valves 1 and 2 are closed, valves 4 and 9 are opened, the stock solution inside the module is removed, and after valves 4 and 9 are closed, valves 3 and 5 are opened, and gas flows into the inside of the module. Gas (N ₂ ) enters from the supply port E and is pushed out at a pressure of 2 to 3 kg to peel and scatter the wax adhering to the outer wall, and the wax is obtained from the discharge port C via the valve 3. Extraction time is approximately 2
~3 minutes. Next, the wax discharged between the outside of the membrane M and the housing is removed by opening the valve 9 and discharging it through the valve 3.
It is blown for 10 to 30 seconds towards the discharge port C side. After blowing the wax and cleaning the membrane surface, return to the original process and pump _P1 .
Use to feed the stock solution from supply valve 1,
resume the past. These series of overcycles are all automatically operated by sequence control. The above sequence mechanism is shown in Table 1.

[Table] ×: Closed

A backwashing process using heated dewaxed oil is added in case backwashing is insufficient when the work has been continued for a long time or different types of oil have been used. As will be explained in accordance with FIG. 2, the method involves pumping heated dewaxed oil from the heated oil tank G to the inside of the membrane M via the pump P ₂ and the pulp 7, as in the case of N ₂ gas. The wax adhering to the membrane (or hollow fiber surface) is dissolved by heating, and the wax is obtained from the discharge port C via the valve 3. The frequency of such backwashing can be said to be almost rare compared to gas backwashing. In addition, in Fig. 1, 4 is a valve, D is a circulation pipe that returns the feed stock solution to the stock solution supply tank A, and in Fig. 2, 6 and 8 are valves, and F is an outlet for heating dewaxed oil. be. Embodiment 2 A case of internal pressure filtration and external pressure backwashing using the total filtration method will be explained with reference to FIGS. 3 and 4. The structure is such that the stock solution is supplied from the inside of the membrane M, internal pressure is applied, and the liquid comes out to the outside. Impurities such as wax are attached to the inside of the membrane M, and the method for removing the deposits is reverse from the outside. This is done by washing. Similar to Example 1, an example of dewaxing sunflower oil will be described. First, a sunflower stock solution (using decolorized oil) that has been rapidly cooled to below 10°C is sent from the stock solution supply tank A' to the module by the supply pump _P'1 . At this time,
Only the supply side valve 10 and the liquid outlet B' valve 11 are open, the others are fully closed, and the overpressure is 0.5~
Work is carried out at 3Kg/ ^cm2 . After about 1 to 2 hours, the overspeed decreases to less than 50% of the initial speed, so the work is switched to membrane cleaning (backwashing). At this time, the supply pump P ₁ and valves 10 and 11 are closed, valves 12 and 14 are opened, and gas (N ₂ ) enters the module from the gas supply port E' and accumulates inside the module at a pressure of 2 to 3 kg. The stock solution in the field may be discharged from the valve 12 through the outlet C', or the valve 13 may be opened and the stock solution returned to the stock solution supply tank A' through the circulation pipe D'. At this time, it is desirable that the wax or impurities that adhere to the membrane surface remain inside the tube and that only the neutral oil is discharged.The adhered wax is then backwashed from the outside with gas or dewaxed oil. Once removed, highly pure wax can be recovered. To discharge wax, open valve 12,
Gas (N ₂ ) is supplied from the gas supply port H through the valve 15.
was introduced to peel off the wax adhering to the inner wall, and the wax was blown with _N2 pressure. The following procedure is the same as in Example 1. In addition,
In Figure 4, G' is a heating oil tank, _P'2 is a pump,
16 and 17 are valves. Normally, backwashing can be done using room temperature or warm gas during overspeeding, but once the overspeed begins to gradually decrease (once a day or once every two days).
(3) After completely dissolving the wax adhering to the inner surface of the hollow fibers using heated dewaxing oil, the re-waxing operation is started. In this case, the number of washes, the time for one wash (timer), etc. are all automatically operated by sequence control.

[Brief explanation of drawings]

Figures 1 and 2 show external pressure overflow using the total overflow method.
FIGS. 3 and 4 are explanatory diagrams for performing internal pressure backwashing, and FIGS. 3 and 4 are explanatory diagrams for performing internal pressure backwashing and external pressure backwashing using the total filtration method.

Claims (1)

[Scope of Claims] 1. In the step of filtering fats and oils containing wax through a porous membrane to separate and remove the wax, the raw solution accumulated in the module is blown away using compressed gas, and then the membrane is removed. A method for restoring the filtration ability of a porous membrane, characterized by backwashing from the permeated liquid side to the raw liquid side using compressed gas. 2. In the process of filtering fats and oils containing wax through a porous membrane to separate and remove the wax, compressed gas is used to blow away the stock solution accumulated in the module, followed by backwashing with compressed gas and heating. A method for restoring the filtration ability of a porous membrane, characterized by carrying out the method in combination with backwashing with oil.