JPH021514Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field: The present invention relates to an improvement of a vacuum generating device that combines a steam ejector, an indirect contact condenser, and a liquid ring pump.

Background technology: Vacuum generators with multistage steam ejector systems are widely used in the range of atmospheric pressure from 10 ^-2 Torr (Torr10 ^-2 mmHg abs.) due to their ease of use, stable performance, and low cost. has been done. However, from an energy efficiency perspective,
The efficiency is particularly low in the pressure range of 1 to 2 steps from the atmospheric pressure side (760 torr to about 80 torr). Therefore, various attempts have been made to improve energy efficiency by combining a steam ejector and a liquid ring pump.

For example, a direct contact condenser 3' (barometric type) is arranged in a single-stage or multi-stage steam ejector to remove condensable substances, and then the non-condensable gas (air, etc.) and entrained water vapor are exhausted by a liquid ring pump 5. There is a method of taking cooling water and condensed/dissolved substances out of the system using an atmospheric leg (Figure 2). in this case,
In order to prevent cavitation in a liquid ring pump, it is common practice to maintain the degree of vacuum at about 80 Torr or higher, and it is not preferable to regularly use it at a vacuum level below 60 Torr.

Therefore, it is recommended to further install a steam ejector 10 after the barometric condenser 3', pressurize it to 100 torr or more, then apply it to the barometric condenser, and then apply it to the liquid ring pump 5 (Fig. 3). Efficient but expensive.

Another method for improving the performance of the liquid ring pump is to arrange an air ejector 4 instead of the steam ejector and drive it with the atmosphere.In this case, the amount of water vapor used is reduced, but the liquid ring pump 5 (Figure 4).

All of the above three methods are 1 to 2 on the atmospheric pressure side.
In an attempt to save energy by replacing the stage with a liquid ring pump, the use of a barometric condenser requires installation at a high location, and the latter stage liquid ring pump is usually installed far away, making installation and repair difficult. There is a problem in terms of

In addition, although it is theoretically possible to remove cooling water, condensed water, and non-condensable gas together using a liquid ring pump, there are problems such as a significant increase in the power required for the liquid ring pump. Not used except in polar equipment.

By using an indirect contact condenser instead of a direct contact condenser, there is no need to use an atmospheric leg to discharge the atmospheric cooling water, and only a very small amount of steam drain and condensate of the suction treated fluid is required compared to the amount of cooling water. It is only necessary to discharge the gas to the outside of the system, and it becomes possible to directly discharge it simultaneously with the non-condensable gas using a liquid ring pump. It is also possible to eliminate the difficulty of installing a series of device systems separately in the vertical direction. Further, indirect contact condensers have the advantage that the process fluid and cooling water do not mix, although the equipment costs are higher.

On the other hand, the steam ejector is a typical example of machinery that is said to have a one-point design. Once determined, it is difficult to change the operating state.
However, even if the steam ejector has a compression ratio of more than twice and is in an operating state called critical operation, where the compression flow velocity in the differential user exceeds the speed of sound, if the back pressure falls below the design pressure, the suction will be applied accordingly. It is possible to reduce the amount of driving steam by lowering the driving steam pressure or by reducing the diameter of the driving nozzle using a spindle, etc., without substantially affecting the capacity. Therefore, if the steam ejector back pressure (i.e., the condensing pressure of the indirect contact condenser) decreases due to seasonal changes in the temperature of the cooling water for the condenser (particularly a decrease) or a decrease in load, the amount of steam driving the steam ejector can be reduced. performance can also be maintained.

Problems that the invention aims to solve: In the above case, naturally the vacuum pump downstream of the steam ejector and condenser must be able to cope with the back pressure change, but when a liquid ring pump is used, cavitation is the main problem. Due to these problems, it is difficult to use it regularly in high vacuums below 60 torr.

Means for solving the problems: The vacuum generator of the present invention mainly combines a steam ejector, an indirect contact condenser, and a liquid ring pump with an air ejector, thereby achieving
In particular, the objective is to maintain high performance regardless of the cooling water temperature, which changes depending on the seasons (spring, summer, fall, winter). The present invention allows the liquid ring pump to function effectively even if the condensation pressure decreases, and also allows the condensate generated in the indirect contact condenser to be extracted rationally and efficiently. Therefore, the present invention comprises: (a) one or more steam ejectors and an indirect contact condenser installed downstream thereof; (b) an air ejector for sucking non-condensable gas extracted from said indirect contact condenser; a liquid ring pump installed downstream thereof; and (c) a feeding means for feeding the condensate generated in the indirect contact condenser into a sealing liquid circulation path of the liquid ring pump. This is the summary.

As the feeding means, the condensate of the indirect contact condenser is transferred to a liquid eductor (an ejector that collects and moves other liquids using a driving liquid) or a height differential siphon (the indirect contact condenser is moved to a high temperature equivalent to the differential pressure of the air ejector). The condensate containing the liquid eductor's driving fluid (the former) or the condensate (the latter) is added to the sealing liquid circulation line of the liquid ring pump, but if it contains impurities, the system It may also be released outside.

Effect: Generally, when an air ejector is installed between an indirect contact condenser and a liquid ring pump, it becomes difficult to remove the condensate generated in the indirect contact condenser to the outside of the system.

That is, when the non-condensable gas and condensate are sent to the suction side of the liquid ring pump through the air ejector, the drain discharge capacity of the air ejector is small, so as the amount of condensate increases, the capacity decreases significantly. In order to prevent this, if the condensate is sent to the liquid ring pump together with the non-condensable gas by a liquid eductor bypassing the air eductor, it often generates intense noise and is accompanied by vibrations.
Additionally, both the eductor drive fluid and the condensate load the fluid ring pump, which increases energy consumption.

In the present invention, in order to avoid this, the condensate is removed by a liquid eductor or a height difference siphon.
Since the structure is such that the liquid is fed into the sealing liquid circulation line of the liquid ring pump, it is strictly distinguished from non-condensable gas and does not generate noise. In addition, the temperature of the sealed water in a liquid ring pump increases due to frictional heat during circulation, so it is necessary to cool it using a heat exchanger and to lower the temperature by adding new low-temperature water. The temperature increase can be suppressed by adding water. However, depending on the type of process that requires a vacuum generator, the condensate may contain corrosive impurities.
If necessary, it is advisable to install piping at the outlet of the liquid eductor for draining the condensate out of the system. Normally, the sealing pressure of a liquid ring pump requires a gauge pressure of approximately 1 kg/ ^cm2 , but during operation there is no problem with operation even if the pressure is almost atmospheric or slightly negative, and the eductor's driving water may be water with a gauge pressure of approximately 1 Kg/cm ² .

Power costs can be reduced by using the differential siphon principle instead of the liquid eductor and by placing the indirect contact condenser higher than the liquid ring pump to account for the 50 to 100 torr of compression pressure provided by the air ejector. In general, the use of a differential siphon can reduce the load on the liquid eductor, but the device becomes somewhat vertically discrete.

Embodiment: In FIG. 1, a gas-based fluid from an apparatus undergoing vacuum treatment enters the first stage steam ejector 1 from A, and is further suctioned in series by the second stage steam ejector 2, resulting in indirect contact condensation. Enter vessel 3. The condenser 3 is, for example, a multi-tubular heat exchanger, in which cooling water passes through the tubes and fluid to be treated passes through the outside of the tubes.
The generated condensate collects at the bottom of the shell. The non-condensable gas is sucked by the air ejector 4, further sucked by the liquid ring pump 5, and discharged from the pipe B. It is cooled by a heat exchanger 8 interposed in the conduits of the sealing liquids 6 and 7, which act as pistons in the liquid ring pump. The amount equivalent to the leaked water is replenished as new sealed water. Entrainment due to released gas is removed by a mist separator or the like, but illustration thereof is omitted. The condensate of the indirect contact condenser is extracted by the liquid eductor 9 and sent to an appropriate position in the sealing liquid circulation circuit of the liquid ring pump 5. It should be noted that the process diagram of FIG. 1 does not take into account potential head relationships (vertical positional relationships of component devices).

If there is an altitude difference between the condensate liquid level of the indirect contact condenser 3 and the natural liquid level (potential head 0 surface) of the sealing liquid of the liquid ring pump 5, which is equivalent to the increase in water head due to the air ejector 4, the height difference is approximately 50 to When 100 torr is applied, condensed water can be sent to the sealing liquid circulation section by the water head without using the liquid eductor 9.

Effects of the invention: The vacuum generator of the invention has the following advantages over conventional equipment.

(1) Since a barometric direct contact condenser is not used, the components do not become separated in the vertical direction.

(2) An air ejector is installed after the indirect contact condenser to increase the suction pressure of the liquid ring pump, increasing energy efficiency. In particular, it is effective in reducing the amount of steam in the steam ejector by lowering the cooling water temperature and lowering the condensing pressure due to a reduction in load.

(3) The condenser of the indirect contact condenser is fed into the sealing liquid circulation path of the liquid ring pump, and since there is no condensed liquid on the suction side of the pump, problems such as noise and vibration can be prevented. .

[Brief explanation of drawings]

FIG. 1 shows a process diagram for one embodiment of the present invention. 2, 3, and 4 all show process diagrams of a conventional vacuum generator. 1...First stage steam ejector, 2...Second stage steam ejector, 3...Indirect contact condenser, 3'...
Barometric direct contact condenser, 4...Air ejector, 5...Liquid ring pump, 6, 7...Sealed water circulation pipe of liquid ring pump, 8...Sealed water cooling heat exchanger, 9...Liquid eductor, 10...Steam ejector .

Claims (1)

[Claims for Utility Model Registration] 1. (a) One or more steam ejectors and an indirect contact condenser installed downstream thereof; (b) Suction of non-condensable gas extracted from the indirect contact condenser. an air ejector and a liquid ring pump installed downstream thereof; (c) means for feeding condensate generated in the indirect contact condenser into a sealing liquid circulation path of the liquid ring pump; Characteristic vacuum generator. 2. The vacuum generator according to item 1, wherein a liquid ejector is used as the feeding means for feeding the condensed liquid into the sealing liquid circulation line of the liquid ring pump. 3. The vacuum generator according to item 1, wherein a height difference siphon is used as the feeding means for feeding the condensed liquid into the sealing liquid circulation pipe of the liquid ring pump.