JPH0427411A - Method and device for supplying bactericidal gas having a high humidity - Google Patents

Abstract

PURPOSE: To carry out fermentation and cultivation in a bio-plant for a long time by performing a filtration to remove germ by allowing a highly humid gas to pass through a germ removing filter having a hydrophobic polymer membrane as its filter medium while continuously removing, from the membrane surface, water drain generating on the surface of the primary side of the hydrophobic polymer membrane. CONSTITUTION: A gas source (1), a gas-liquid contact apparatus (2) and a germ removing filter apparatus (3B) having a hydrophobic polymer membrane as its filter medium are so arranged that a gas from the gas source passes through the germ removing filter apparatus after increasing its humidity by contact with water in the gas-liquid contact apparatus. In the germ removing filter apparatus, water drain generated on the surface of the primary side of the hydrophobic polymer membrane is removed immediately flowing down without staying on the membrane surface.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a method for supplying filtered and sterilized gas while keeping its humidity high and reducing the energy required for operation. and regarding equipment. [Prior Art] For example, when performing aerobic fermentation or culture, the air blown into a tank must be sterilized to avoid contamination with bacteria. Membrane type sterilization filters are often used for this purpose. However, the membrane that makes up the sterilization filter is made of a hydrophobic material, such as fluororesin, which prevents the moisture contained in the gas from condensing there and making the surface of the sterilizer wet. I can't. This water drain significantly increases the gas passage resistance and eventually leads to water plugging (blockage). To avoid this, when using a sterilization filter that uses a hydrophobic polymer membrane, the gas should be dehumidified before passing through the sterilization filter, so that water drainage on the membrane surface does not become a practical problem. and then pass through the membrane
It was fleeting. FIG. 2 is a flowchart of a conventional sterilizing gas supply device, in which gas from a gas source (1) passes through a drain trap (4) and is stored in a hold tank (5), then a pre-filter ( After dehumidification through the freezing dehumidification II (Ref, ) and adsorption dehydration tower (Abs, ) (6), a sterilization filter (3A
). On the other hand, if the dehumidified and sterilized air is continuously blown into the tank as described above, there is a problem in that the liquid level in the tank gradually decreases. This is simply because the sterilized air is dry for the reason mentioned above. In order to prevent the air being blown into the tank from taking away the moisture in the tank, it is sufficient to provide a certain amount of humidity, but it is not easy to add moisture to the sterilized air while maintaining sterile conditions. . In addition, the dehumidification of the air described above generally involves the steps of lowering the dew point by cooling, removing moisture condensation, and reheating, as shown in Figure 2 using a refrigerated dehumidifier. Although adsorption and dehydration of activated alumina is also used,
In any case, a large amount of energy is consumed for operation, and improvement in this point has been desired. [Problems to be Solved by the Invention] An object of the present invention is to eliminate the need for humidification for sterilization by treating the gas with high humidity when supplying sterilization gas, typically sterilized air. This makes it possible to obtain high-humidity sterilizing gas without any strain, making it particularly useful for ventilation systems in bioplants.It also eliminates the need for dehumidifiers and dehumidifying operations that were unavoidable for supplying sterilizing gas, reducing plant costs and energy costs. The goal is to provide technology. [Means for Solving the Problems] The method of supplying a high-humidity sterilization gas of the present invention involves filtering and sterilizing the high-humidity gas by passing it through a sterilization filter using a hydrophobic polymer membrane as a filtering material. , consists of continuously removing water drainage generated on the primary surface of the hydrophobic polymer membrane from the membrane surface to prevent water plugs in the membrane while allowing gas to continue to pass through. If necessary, before passing through a hydrophobic polymer membrane,
Adding a step of contacting the gas stream with water to increase its humidity. The apparatus of the present invention for carrying out the above method, especially the latter, comprises a gas source (1), a gas-liquid contact device (
2) and a sterilizing filter device @ (3B) that uses a hydrophobic polymer membrane as a filtering material, the gas from the gas source comes into contact with water in a gas-liquid contact device to increase its humidity, and then passes through the sterilizing filter device. The sterilizing filter device has a structure in which water drainage generated on the primary surface of the hydrophobic polymer membrane immediately flows down and is removed without remaining on the membrane surface. In FIG. 1, the gas source (1) is, for example, a near compressor, and the pressure applied here serves as a driving source for circulating air. Of course, as the driving force, a blower may be used in the distribution path, or the gas pressure of a cylinder may be used. Symbols (4) to (6) are the same as in Figure 2, and (7) is a tank that receives water drain, and when the water level is detected by the level sensor (8) and reaches a predetermined level. The structure is such that water is drained by opening a solenoid valve (9). The membrane material of the sterilization filter in the present invention may be any hydrophobic material, such as Teflon,
Polymer membranes such as polysulfone, polypropylene, and polyvinylidene fluoride can be used. The shape of the membrane is conveniently pleated, disk-shaped, or the like. The sterilization performance of the membrane may be selected appropriately depending on the desired degree of sterilization, and is usually 1012 cells/CIi or 1010 cells/r.
Use one with sterilization performance, such as i, 106 cells/cd. (Function) When high-humidity gas is passed through a hydrophobic polymer membrane, condensation of the water contained therein is unavoidable. It is generally believed that the only way to avoid this inconvenience is to dehumidify the gas before passing it through the hydrophobic polymer membrane, and actual plants have been designed and constructed in this way. Regarding the usage of hydrophobic polymer membranes, it is unclear whether the sterilization performance can be maintained under such conditions where water is present, and from this point of view, the presence of water on the membrane surface is
This was a concern for those using hydrophobic polymer membranes. These circumstances are the same when sterilizing exhaust gas from equipment that handles pathogenic bacteria in order to avoid so-called biohazards. The method used is to heat the high-humidity gas to be sterilized to lower its relative humidity, and then pass it through a heat-resistant sterilization filter. The inventors took on the challenge of the conventional problems described above, and found that if high-humidity gas could be filtered and sterilized using a sterilization filter before being supplied, it would be possible to avoid a drop in the water level in the tank into which the sterilization gas was blown. Moreover, we conducted an experiment thinking that the equipment and energy for gas dehumidification would be unnecessary. As a result, water drainage generated on the hydrophobic polymer membrane that is a sterilization filter is mostly present on the primary surface of the membrane, and if it is allowed to flow freely and drained continuously, it will accumulate on the membrane surface. They found that this method does not increase passage resistance or cause the water plug phenomenon, and also confirmed that sterilization performance can be maintained even in the presence of water. [Example] Hydrophobic porous membrane rMcY made of polytetrafluoroethylene
A sterilizing filter with a filtration area of 2300 cd was manufactured using 4463FRPJ (nominal pore size 0.2 t1 m, manufactured by Nippon Ball). Filter housing - Inject water into the next side to 1.5~
4. OK'j/cti range (II's withstand pressure is 4.2Kg
/C11), applying pressure in increments of 0.5 to It was constant (38d). from this result,
It was determined that water did not enter the membrane, but rather adhered to the surface. Next, with the maximum amount of water attached to the membrane, the relative humidity is reduced to 1.
Dry air of 0% or less and air containing 100% saturated moisture were passed through the membrane, and the behavior of water adhering to the membrane was examined. At this time, water was allowed to freely flow down from the surface of the membrane, and the water that flowed down was immediately drained. The results shown in FIG. 3 were obtained, and it was found that water adhering to the membrane was gradually removed not only when dry air was passed through it, but also when highly humid air was passed through it. Considering the case where the air that reaches the membrane contains more than the saturation amount of moisture, we temporarily injected moisture into the air while passing air with 100% humidity. This water is transported in the form of mist and becomes a water drain on the surface of the membrane. The data shown in Figure 4 are obtained, and the pressure drop (Δp) when passing through the membrane increases due to the occasional water plug;
It was found that the condition recovered quickly and returned to its original state, and that Δp did not increase even after long-term operation. From the above results, even if high-humidity air (containing moisture at or near saturation, and sometimes containing moisture exceeding saturation) is passed through a hydrophobic polymer membrane, water drainage generated on the surface of the membrane is suppressed. It was found that if the gas is placed under conditions that allow continuous discharge, the gas can be processed continuously without being affected by water plugs. In order to confirm whether this method of using a hydrophobic polymer membrane did not have a negative effect on the sterilization performance of the filter, we cultured E and Qoli in a fermenter with a capacity of 31 cm, and the air blown there was exhausted. It is considered that the gas with almost saturated humidity that passes through the above-mentioned sterilization filter membrane (filtration area 12007) exits. ), a bacterial challenge test was conducted to examine the bacteria collection efficiency. The results shown in Figure 5 were obtained. Although the filter differential pressure increased over time, by taking measures to remove condensate, this should be suppressed to a level that allows continuous operation for an unlimited period of time in practical terms. In any case, 100
Bacterial collection efficiency was maintained at 100% during the experimental period of hours. [Effects of the Invention] By using the method and apparatus of the present invention, highly humid sterilizing gas can be supplied without requiring dehumidification equipment and processes, and therefore at significantly reduced cost. Therefore, when this technology is applied to air blowing into a tank for aerobic fermentation or culture, it is possible to do so without causing a drop in the liquid level in the tank (or risking the risk of re-humidifying the tank). ), fermentation and cultivation can be carried out for long periods of time in bioplants, which is of great significance.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an example of the configuration of an apparatus for supplying high-humidity sterilizing gas according to the present invention. FIG. 2 is a flowchart showing an example of the configuration of a conventional device for supplying sterilizing gas. Figures 3 to 5 are graphs of data from experimental examples of the present invention, and Figure 3 shows a situation in which water attached to a hydrophobic polymer membrane for a sterilization filter is removed by ventilation. Figure 4 shows the change over time in membrane passage resistance (pressure loss) during continuous operation, and Figure 5 shows the results of the bacterial challenge test. In FIG. 5, the upper row shows the bacteria concentration in the air on the primary side of the sterilizing filter, the interruption shows the differential pressure before and after the filter, and the lower row shows the change over time in the bacteria collection efficiency. 1... Gas source 2... Gas-liquid contact device 3A, 3B... Sterilization filter device 4... Drain trap 5... Hold tank 6... Pre-filter 7... Water drain tank 8...Level sensor 9...Solenoid valve Patent applicant: JGC Corporation Ball Corporation

Claims (5)

[Claims] (1) Highly humid gas is filtered and sterilized by passing through a sterilization filter using a hydrophobic polymer membrane as a filter medium, and water drainage generated on the primary surface of the hydrophobic polymer membrane is continuously removed from the membrane surface. A method of supplying a highly humid sterilizing gas consisting of continuing the passage of the gas while preventing water plugs in the membrane by removal. 2. The method of claim 1, further comprising the step of contacting the gas stream with water to increase its humidity prior to passing through the hydrophobic polymer membrane. (3) The relative degree of gas flow passing through the hydrophobic polymer membrane is 70
100% and the relative humidity of the gas stream after sterilization is substantially the same. 4. The method of claim 1, wherein the gas stream passing through the hydrophobic polymeric membrane contains supersaturated moisture, and the gas stream after filtering and sterilization contains approximately saturated moisture. (5) A gas source, a gas-liquid contact device, and a sterilization filter device that uses a hydrophobic polymer membrane as a filter are sterilized after the gas from the gas source comes into contact with water in the gas-liquid contact device to increase its humidity. The sterilization filter device is a high-density filter that has a structure in which water drainage generated on the primary surface of a hydrophobic polymer membrane immediately flows down and is removed without remaining on the membrane surface. A device that supplies humid sterilizing gas.