JPH0533090B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method and apparatus for sterilizing and cleaning the inside of a membrane device incorporating an ultrafiltration membrane.

<Prior art> In order to separate or concentrate components dissolved or suspended in a liquid, a device equipped with an ultrafiltration membrane is used, and the dissolved organic components, inorganic components, and suspended substances in the liquid are filtered through the membrane. In addition to concentrating on the pressure side, a highly pure solution is obtained on the permeation side of the membrane, and this is used to separate and concentrate proteins, concentrate sugars, concentrate enzymes and bacterial cells, and remove salts. It is used in a wide range of fields, including municipal water, electronic industry cleaning water, and nuclear water.

An important problem with this membrane device is the generation of bacteria due to contamination within the device. Conventionally, the sterilization process was periodically performed with hot water at 80 to 90°C (Japanese Patent Application Laid-Open No. 57-1999).
159587, JP-A-60-110390), 100~
This is done using steam at 130°C (Japanese Patent Application Laid-open No. 159587/1987).

<Problems to be Solved by the Invention> Sterilization with hot water at 80 to 90°C is effective against general bacteria, but is not effective against heat-resistant spore bacteria.

Also, it takes a long time to sterilize.

Sterilization using steam does not have the problems associated with steam hot water, but it may dry out during steam ventilation, which may cause membrane deterioration, or the membrane may be damaged by impact when steam condenses, or condensed water may enter the equipment. Another problem is that the temperature rise in the area where the sterilization accumulates deteriorates, resulting in poor sterilization.

<Means for solving the problem> Therefore, the method for sterilizing a membrane device of the present invention is to
It is characterized by sterilization using pressurized hot water at ℃. In addition, the sterilizer for a membrane device of the present invention supplies a pressurized medium to the hot water production means and the steam hot water production means connected to the stock solution supply system to the membrane device,
The method is characterized by comprising means for producing pressurized hot water, means for pressurizing and supplying sterilized water to the hot water production means, and a system for taking out sterilized water from the membrane device.

<Operation> According to the sterilization method of the present invention, pressurized hot water of 100 to 150°C is supplied to the inside of the membrane device.

Further, the hot water production means connected to the stock solution supply system of the sterilizer of the present invention heats the sterilized water, which is also pressurized and supplied, using the supplied heating medium.
Pressurized hot water of 100-150℃ is supplied to the membrane equipment.
Then, the sterilized pressurized hot water that has sterilized the inside of the membrane device is taken out from the device.

<Example> The figure shows an example of the present invention, which will first be described based on FIG. 1. The example in Figure 1 shows a flow sheet for concentrating a stock solution to obtain a product.
is a membrane device with a built-in ultrafiltration membrane 2, and as is well known, the raw solution in the raw material tank 3 is fed by a liquid supply pump 4 and a pressure pump 5.
The solution is then pressurized by a pressurizing pump 5 and supplied to the pressurizing side 1a of the membrane device 1 through the stock solution supply system 6. As a result, the part of the stock solution that has passed through the ultrafiltration membrane 2 and exited to the permeation side 1b of the device 1 enters the membrane permeation liquid tank 7.

Further, the concentrated stock solution on the pressurized side is circulated through the circulation line 8 to the pressure pump 5 or the raw material tank 3, and a part of the liquid that has reached a predetermined concentration enters the concentrated liquid tank (product tank) 9.

Therefore, operation is performed by sending the stock solution in the raw material tank 3 to the pressurizing pump 5 by the liquid supply pump 4 in the amount that has entered the liquid tanks 7 and 9. In addition, the circulation line 8, the pressurizing side 1a of the device
As shown in the figure, the system 9' that leads the liquid from the liquid to the concentration tank 9 is provided with a valve whose opening degree can be adjusted, and the opening degree of this valve is adjusted to maintain a predetermined product concentration.

In this embodiment, a heat exchanger 10 as a means for producing hot water is provided in the raw solution supply system 6 downstream of the pressurizing pump.
This heat exchanger includes a means 11 for supplying and discharging steam as a heating medium, and a heat exchanger 10 of a stock solution supply system 6 as a means for pressurizing sterilized water and supplying it to the heat exchanger.
A discharge path 13 from the second pressurizing pump 12 is connected to a point upstream of the pump.

The sterilized water is water, preferably pure water,
It is placed in a nearly airtight water tank 14 that is sucked by the second pressurizing pump 12, and the space inside the tank is filled with an inert gas, such as nitrogen gas, to keep it under some pressure. Prevent bacterial contamination.

Then, take-out systems 15a and 15b for sterilized treated water are connected to the pressure side 1a and the permeation side 1b of the membrane device 1, and in this embodiment, the water is circulated back to the water tank 14.

When performing the above-mentioned operation, the pressurizing pump 5 passes the stock solution through the heat exchanger 10 and supplies it to the membrane device 1, so that the heating medium is not supplied to the heat exchanger 10 by the means 11 during the operation.

To sterilize the membrane device, the operation is interrupted, and the second pressure pump 12 supplies the sterilized water in the water tank 14 to the membrane device 1 via the discharge path 13 and the heat exchanger 10. The sterilization temperature of the sterilized water supplied to the membrane device is set at 100 to 150°C by supplying and discharging steam using the means 11.
The pressure P of the pressurized hot water is set to be greater than the sum of the water vapor pressure P _v at the sterilization temperature and the pressure drop ΔP of the semipermeable membrane module (P>P _v +ΔP).

Although not shown, the sterilization temperature is adjusted by adjusting the amount of steam using a thermometer provided in the stock solution supply system 6. Although not shown, the pressure is adjusted by adjusting the opening degree of a valve provided in the extraction system 15a using a pressure gauge provided in the extraction system 15a.

As a result, the sterilized water that has begun to be supplied to the membrane device is gradually heated from room temperature to become pressurized hot water at a predetermined sterilization temperature, and is supplied to the pressurizing side 1a of the device to sterilize this pressurizing side 1a, A portion flows out to the extraction system 15a. Then, the remaining part is passed through the ultrafiltration membrane 2, the ultrafiltration membrane and the permeation side 1b are sterilized, and the extraction system 1
5b, and in this embodiment is circulated to the water tank 14 for recovery.

When the sterilization process is completed, the steam to the heat exchanger 10 is stopped, and the sterilized water in the water tank is supplied under pressure to the membrane device 1 through the heat exchanger 10 with the second pressure pump 12 to cool the membrane device. Once cooled down, operation will resume.
Note that during this cooling step, if necessary, cooling water may be flowed through the steam supply means to enhance the cooling effect. Furthermore, by using the treated water used for sterilization to cool the membrane device, there is no need to newly produce sterile water, and cooling can be easily accomplished in a short time.

In the above description, the water tank 14 is not necessarily a closed type into which nitrogen gas is injected, but may be an open type. If the tank is an open type, a sterile filter is attached to prevent bacteria from entering the tank from the air.

In the above explanation, the heat exchanger 1 is used as the hot water production means.
0 was used, but this heat exchanger may be omitted and steam may be directly supplied to the sterile treated water. In this case, steam is directly supplied to the sterilized water in the water tank 14 as shown by the chain line 11'. In order to drain water corresponding to the supplied steam, a drain pipe having a relief valve 16 is provided in the water tank.

The embodiment shown in FIG. 2 shows another example of the hot water production means. This diagram omits the flow for obtaining the product. Also, since the same reference numerals as in FIG. 1 indicate the same parts, the explanation of those parts will be omitted below.

In this embodiment, a circulation system 20 including a circulation pump 21 and a heat exchanger 22 is connected to the water tank 14.

To sterilize the membrane device, the pressure pump 12 and the circulation pump 21 are operated, and the heat exchanger 22
supply steam to. As a result, the sterilized water in the water tank 14 is gradually heated from room temperature to a predetermined sterilization temperature. After the sterilization process has been carried out for a predetermined period of time, the supply of steam is stopped and the membrane device is cooled.

In the embodiment shown in FIG. 2, temperature and pressure are controlled in the same manner as in FIG.

Next, experimental results of the present invention will be shown.

The experiment was carried out using the experimental apparatus shown in Figure 1, which is equipped with a membrane device consisting of an internal pressure tube-type ultrafiltration membrane (DMH-250 manufactured by Daicel Chemical Industries, Ltd.) containing a polyethersulfone membrane with a molecular weight cut-off of 40,000 or more. Ivy.

Steam is supplied to the heat exchanger so that the temperature on the inlet side of the membrane device is 135°C and the temperature of the treated water at the outlet on the permeate side is 128°C, and the second pressure pump is used to increase the pressure of 5.0 kg/kg on the pressure side of the membrane device. Pressurized hot water was supplied at cm ² and circulated from the pressure side and the permeation side to the water tank using a take-out system to perform sterilization for 30 minutes. After cooling the membrane device, preheat at 145℃ for 15 minutes in a separate device.
A 5% skim milk powder solution that had been sterilized by heating for seconds was supplied to the membrane device at room temperature, circulated for 1 hour, sampled, and the presence or absence of viable bacteria in the sample was determined by a culture test, and no viable bacteria were detected. Nakatsuta.

After performing the above-mentioned sterilization process 100 times, a test was conducted to determine if the performance of the membrane deteriorated due to heat in the membrane device. The test is disclosed in JP-A-60-20135. The removal rate was measured using a 1000 ppm aqueous solution of a reaction product (hereinafter referred to as "PVA-D") of polyvinyl alcohol (hereinafter referred to as "PVA") and a reactive dye (hereinafter referred to as "D"). As a result, PVA-D
The removal rate remained above 99.98%, and no deterioration in membrane performance was observed.

<Effects of the Invention> Since the method of the present invention sterilizes with pressurized hot water at a temperature of 100 to 150°C, it can also sterilize heat-resistant spore bacteria, and
Sterilization can be performed easily and reliably without causing dry deterioration of the membrane when using steam, damage to the membrane due to condensation, or poor sterilization due to temperature drop in a pool of condensed water.

Furthermore, the device of the present invention can easily control the temperature of sterilized water.
The sterilization process can be performed by supplying pressurized hot water at 100 to 150°C to the membrane device without lowering the temperature.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of one embodiment of the present invention, and FIG. 2 is a flow sheet of another embodiment of the present invention. 11 is a heat exchanger, 11 is a means for supplying a heating medium to the heat exchanger, 12 is a second pressure pump that pressurizes and supplies sterilized water to the heat exchanger, and 15a and 15b are sterilized water from a membrane device. The extraction system is shown.

Claims (1)

[Scope of Claims] 1. A method for sterilizing a membrane device incorporating an ultrafiltration membrane, characterized in that the membrane device is sterilized using pressurized hot water at 100 to 150°C. 2. In a sterilizer for a membrane device incorporating an ultrafiltration membrane, a hot water production means connected to a stock solution supply system to the membrane device, a means for supplying a heating medium to the hot water production means, and a means for supplying a heating medium to the hot water production means; Sterilization of a membrane device characterized by having a means for pressurizing and supplying sterilized water to a water production means and turning it into pressurized hot water at 100 to 150°C, and a system for taking out the sterilized water from the membrane device. Device.