JPH0283015A - Gas dehumidification - Google Patents

Abstract

PURPOSE:To carry out gas dehumidification economically in gas dehumidification method wherein humidity is diffused through a membrane by measuring humidity of a humid body taken out as a side stream and controlling the flow amount of the gas taken out as a side stream depending on the measurement results. CONSTITUTION:In dehumidification wherein a pressurized humid gas is flowed along to a thin membrane of tubular fibers (D) and the humidity is allowed to permeate the membrane, a part of a gas already dehumidified is taken out as a side stream from a side stream part (H), its pressure is reduced to more or less atmospheric pressure by a valve (I), and then the resulting gas is flowed along to a permeating side of the membrane so as to diffuse humidity through the membrane. At the time, a hygrometer (M) is installed between a side stream taking out part (K) of a dehumidifier (C) and a humid gas discharging part (L) and a controller (I') is operated depending on the indication of the hygrometer to control the open degree of the valve (I) and keep it constant so that an obtained dried gas discharged from a dried gas discharging part (G) could have a constant dew point. As a result, dehumidification is carried out economically and efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field] The present invention relates to a method for removing moisture from a humid gas.

[Conventional technology and problems to be solved] There are many industrial fields that require dry gas. In particular, the compressed air that drives automatic regulating valves and remote control valves must be dry. This is because if compressed air containing moisture is used, the moisture may freeze inside the device in cold weather, stopping valve operation and causing a serious accident.

Therefore, this compressed air must be dehumidified in some way.

Conventionally, methods for dehumidifying moisture-containing gas include: ■ Using an adsorbent that adsorbs moisture ■ Cooling to a low temperature to reach the dew point, removing condensed moisture, and then heating to room temperature There are methods such as washing with diethylene glycol and absorbing water, and recently there are methods such as: - flowing moisture-containing gas under pressure on one side of a thin film of polymeric material that selectively permeates water, and reducing the pressure on the other side. A method that allows only moisture to pass through is being put into practical use.

Among the above methods, method (2), which uses a thin film of polymeric material that selectively permeates moisture, does not require heat, has no moving parts in the equipment, and can be used continuously. This method is considered to be the most economical since it can be done economically, but it is predicted that if this is improved, the work efficiency can be improved even more economically.

Therefore, the problem to be solved by the present invention is to improve the method (2) above.

[Means to solve the problem]

The present invention has been made against the background of the above-mentioned prior art, and has been made for the purpose of improving a gas dehumidification method using a thin film of a polymeric substance having a function of selectively permeating moisture. When pressurized moisture-containing gas flows along a thin membrane and the moisture is removed by passing through the membrane, a part of the gas from which moisture has already been removed is taken out as a side stream and is depressurized back and forth to atmospheric pressure. In a gas dehumidification method in which moisture is diffused through a membrane by flowing along the permeation side of the membrane, the humidity of the moisture discarded as a side stream is measured, and the flow rate of the gas taken out as a side stream is determined based on the measurement result. It is characterized by being adjustable.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

The figure is a system diagram of the present invention, in which A is a humid compressed gas supply section, B is a valve, and C is a ventilator containing a bundle of tubular fibers made of a polymeric material that has the function of selectively permeating moisture. In a humidifier, four fibers out of many are conceptually shown in the figure. E is the humid gas inlet of the dehumidifier C, F is the dry gas outlet, G is the dry gas discharge part, H is the side flow part provided in the pipe 2 between F and G, ■ is the valve, and ■' is the I controller, J
is a side flow intake section installed near the dry gas outlet F of the dehumidifier C,
K is a side flow extraction part provided near the humid gas inlet E of the dehumidifier C, L is a humid gas discharge part, M is a hygrometer, and the humid compressed gas supply part A and the dehumidifier C are connected to piping 1. , the dehumidifier C and the dry gas discharge part G are connected to piping 2, the side flow part H and the side flow intake part J of the dehumidifier C are connected to piping 3, and the side flow outlet part of the dehumidifier C is connected to the moisture gas discharge part. is piping 4
Valve B is installed in pipe 1, Valve I is installed in pipe 3, and Hygrometer M is installed in pipe 4.
The hygrometer M and the controller 1' of the valve I are connected by a signal line 5.

In the above, a fiber bundle was used as the thin film of a polymer substance that selectively transmits moisture because if the thin film is made of fibers, it can withstand internal pressure and easily accommodate a large area.

The humid compressed gas from the humid compressed gas supply section A, which has been compressed to about 5 to 10 atmospheres, is introduced into the dehumidifier C from the inlet E through the valve B, and passes between the bundles of tubular fibers. Then, the moisture is diffused outside the fibers and becomes a dry gas that flows out from the outlet F. Most of it is supplied from the discharge part G to the required part, and a part is branched off as a side stream in the side flow part H. and piping 3
The pressure is reduced by the valve I, and the pressure becomes almost atmospheric, enters the dehumidifier C from the side flow intake part J, and flows along the outside of the fiber bundle, causing moisture inside and outside the Ti fibers to be removed. Due to the difference in partial pressure, the moisture diffuses out of the fibers, is taken away by the side flow gas, flows out from the side flow outlet K, and is disposed of outside through the moisture discharge section. If this side stream gas is large, dry gas discharge part G
Although the dew point of the dry gas obtained from the dry gas decreases, the loss of the compressed gas supplied from the humid gas supply section A increases. Therefore, conventionally, the flow rate in the moist compressed gas supply section A or the dry gas discharge section G is measured, and the indicated value is used to control the valve I.
The opening degree of the valve was adjusted, but this work became extremely troublesome.

Therefore, in the present invention, a hygrometer M is provided between the side flow outlet part of the dehumidifier C and the moisture discharge part, and the opening degree of the valve E is adjusted by operating the controller' according to the reading of the hygrometer M. However, by keeping this constant, the dew point of the dry gas obtained from the dry gas discharge section G is made constant.

As a result, when the flow rate of the compressed gas supplied from the humid compressed gas supply section A changes, the side flow rate branched at the side flow section H is proportional to the supply amount from the humid compressed gas supply section A. Therefore, the conventional moist compressed gas supply section A
Alternatively, it is possible to omit the trouble of measuring the flow rate at the dry gas discharge section G and adjusting the opening degree of the valve (2) based on the indicated value.

According to this method, under appropriate conditions, 7
It is not difficult to operate at atmospheric pressure and obtain dry air with a dew point of -60°C.

When the method of the present invention was actually carried out on moist compressed air using a dehumidifier with a length of about 50 ports and a diameter of 4 cm, the following results were obtained.

Humidity measurement points (shown in the figure) (I) (n)
(III) (IV) Air flow rate (1/min)
288 240 48 48 Air pressure (kg
/dG) 6,65 6.15 0 0
Dew point (atmospheric pressure/'C) -6-40-4
018 Relative humidity (pressure, temperature/%) 100 3.
37 0.48 82.9 Water vapor partial pressure (mmHg)
19.820.6680.096 15.52 Water vapor volume (1/min) 1.011 0.03
0,006 0.98 In the above example, 16.67% of the air supplied from the humid compressed gas supply section A is transferred to the side flow section H.
branched into a side stream from The compressed air with a dew point of -6°C supplied from the supply section A passes through the bundle of tubular fibers and has a dew point of -40°C, and approximately 16.7% of the air is branched from the side flow section H, and the compressed air has a dew point of -6°C. While flowing outside, it reaches a dew point of 18°C and is discharged. This dew point of 18° C. corresponds to a relative humidity of 82.9%, which is quite close to saturation.

The present invention is not concerned with the performance of a device that employs the same, but with the purpose of improving the ability of the device to respond to changes in capacitance.

Now, if it is required to reduce the amount of air supplied to the above device to, for example, 50%, the side flow in the side flow section H should be reduced accordingly from economical considerations.

The adjustment is done by Valve, but if you want to automate this,
It is most rational to set the dew point in the dry gas discharge section G in advance and operate the valve (2) so that the dew point becomes constant, but it is extremely difficult to specify a low dew point without delay.

However, in the present invention, valve (2) is activated by the humidity in the side stream moisture discharge section, and as shown in the table above, the relative humidity of this exhaust exceeds 80%. can be easily measured without delay using an inexpensive high humidity sensor such as a hair hygrometer.

〔Effect of the invention〕

Since the present invention is as described above, moisture-containing gas is flowed under pressure on one side of a thin film of a polymer material that selectively allows water to permeate, and the other side is depressurized to allow only water to permeate and dehumidify. If this method is adopted, dehumidification can be performed extremely economically and effectively, and therefore it is extremely useful in industrial fields that require dry gas.

[Brief explanation of the drawing]

The figure is a system diagram showing an example of implementation of the present invention.

Claims (1)

[Claims] When pressurized moisture-containing gas flows along a thin membrane and the moisture is removed by passing through the membrane, a portion of the gas from which moisture has already been removed is taken out as a side stream and depressurized to around atmospheric pressure. In a gas dehumidification method in which moisture is diffused through a membrane by flowing along the permeation side of the membrane, the humidity of the moisture discarded as a side stream is measured, and the flow rate of the gas taken out as a side stream is determined based on the measurement result. A method of dehumidification of gases characterized by regulating.