JPS6042360B2 - How to operate a multi-stage steam ejector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of operating a multi-stage steam ejector, and more particularly to a method of operating a multi-stage steam ejector that can save driving steam.

Steam ejectors that use water vapor as the driving fluid have a simple structure and are easy to operate, so they are widely used as a type of vacuum pump, but there is a limit to the degree of vacuum that can be achieved with a single steam ejector. For vacuum distillation, vacuum concentration,
BACKGROUND ART In various apparatuses such as vacuum deodorization and vacuum drying, so-called multi-stage steam ejectors are generally used, in which a plurality of steam ejectors are arranged in series and at least one condenser is interposed between the steam ejectors.

The number of steam ejectors and the number of condensers used are usually selected appropriately depending on the target degree of vacuum. By the way, in a multi-stage steam ejector incorporating a condenser, the outlet gas pressure of the condenser affects the ultimate vacuum of the multi-stage steam ejector.
The outlet gas pressure of the condenser depends on the temperature of the cooling water supplied to the condenser. Therefore, when designing a multi-stage steam ejector, the multi-stage steam ejector should be designed based on the maximum value of the cooling water temperature, taking into account the temperature difference between summer and winter, or the temperature difference between day and night, of the cooling water for the condenser. It is customary to design a steam ejector. However, since there is usually a large difference in the temperature of cooling water, especially between summer and winter, the multi-stage steam ejector designed as described above can maintain a cooling water temperature lower than the designed value throughout the year. It will be in operation for a considerable period of time. Operating a multi-stage steam ejector by supplying cooling water at a lower temperature than the design value to the condenser does not impair the function of the ejector itself, but it wastes driving steam.

This is because if the temperature of the condenser cooling water decreases, the condenser outlet gas pressure will inevitably decrease. This is because the target vacuum pressure of '' can be maintained for the ejector as a whole. However, in the conventional operating method of the multi-stage steam ejector, the amount of driving steam to be supplied to the serious ejector is not so much saved as it is estimated from the temperature of the cooling water for the condenser. It's just a matter of manually and dynamically adjusting. However, this manual adjustment method can always reduce the amount of steam less than the theoretical amount of steam that can be saved, so the actual amount of drive steam saved is only a small amount. . This is because the industrial sector has a characteristic that if a situation occurs where the minimum necessary amount of driving steam is not supplied, the pressure balance of the industrial sector group will immediately collapse and the target vacuum pressure will increase significantly. This is because in the case of manual adjustment, which can actually be adjusted only intermittently, the adjustment must be made with a considerable margin.
The present invention provides a method for operating a multi-stage steam industry sector that can significantly reduce the amount of driving steam compared to the above-mentioned manual adjustment method. In a method of operating a multi-stage engineering sector in which a capacitor is interposed between them, the pressure or temperature of the outlet gas of the capacitor is detected, the deviation between the detected value and the design value is taken out as a signal, and the The object of the present invention is to automatically adjust the amount of driving steam supplied to the steam sector located upstream of the condenser. The method of the present invention will be explained below with reference to the accompanying drawings. The drawing shows an example of a multi-stage steamworks sector system diagram in which the method of the present invention is implemented, and in the illustrated example, four steamworks sectors E1 to E1 are shown. E4 are connected in series,
Moreover, capacitors C1 and C2 are installed between steam sector E2 and E3 and between E3 and E4, respectively.

As mentioned above, the design of the multi-stage steam engineering sector is based on the maximum temperature of the cooling water for the condenser, but in the illustrated example, the design is based on the assumption that the cooling water temperature T1 of the condenser C1 will reach a maximum of 34°C. has been done. In other words, when the cooling water temperature rises to 34°C in this multi-stage steamworks sector,
Ezek. The extraction side pressure P3 (same as the outlet gas pressure of the condenser 7-C1) in the evening E3 is maintained at 55T0rr', and the driving steam supply amount of the industrial sector E2 is 3.530k91hr (
9k91dG), and the extraction side pressure P2 is 11T0r.
As a result, the bleed side pressure P of the engineering sector E1
1 is the target vacuum! It is designed to maintain the pressure at 0rr. Now, the cooling water temperature T1 of capacitor C1
When C decreases below the maximum value of 34 C, the outlet gas pressure of the capacitor C1, ie P3, also necessarily decreases.

In this case, even if the discharge side pressure of the working sector E2 is lowered from the design value, the bleed side pressure of the working sector E2 is 11T0r.
can be maintained at r'. This means that the cooling water temperature T1
When the temperature decreases, even if the amount of driving steam supplied to the steam sector E2 is reduced from the design value of 3.530k91hr, the ultimate vacuum pressure P1 of the multistage steam sector is maintained at the target value of 0rr. means to be Therefore, in the method of the present invention, the extraction side pressure P3 of the industrial sector E3, that is, the outlet gas pressure of the capacitor C1 is detected by the detection section 1, and this detected pressure is sent to the calculation section 3 via the input signal transmission section 2. From here, the detected pressure and design value (in this example, 55T0r
A signal commensurate with the deviation from r) is transmitted. This signal then passes through the output j signal transmission section 4 and is sent to the control valve 5.
The amount of driving steam supplied to the industrial sector E2 is automatically controlled in accordance with the above deviation. The following table shows the relationship between the cooling water temperature T1 of the condenser C1 and the minimum required driving steam pressure P$ and amount W supplied by the production sector E2 at that time.

In the illustrated embodiment, an example has been described in which the outlet gas pressure of the capacitor C1 is detected, but instead of this pressure, it is also possible to detect the temperature of the outlet gas.

However, considering that the amount of air that leaks into the vacuum system from the outside affects the pressure but not the temperature, detecting the pressure would improve the accuracy of adjustment. When the temperature is detected, a design value regarding the temperature is adopted by the arithmetic unit, and an output signal is of course produced from the deviation between this and the detected temperature. As is clear from the above explanation, according to the method of the present invention, in response to a decrease in the cooling water temperature of the condenser, without impairing the overall function of the multi-stage steam sector, the There is an advantage that the amount of steam for driving the installed steam industry sector can be automatically reduced without excess or deficiency.

[Brief explanation of drawings]

The drawing is a system diagram showing one embodiment of the present invention.

Claims (1)

[Claims] 1. In a method of operating a multi-stage steam ejector in which a condenser is interposed between steam ejectors, the pressure or temperature of the outlet gas of the condenser is detected, the deviation of the detected value from the design value is extracted as a signal, and the signal is A method for operating a multistage steam ejector, characterized in that the amount of driving steam supplied to the steam ejector located upstream of the condenser is automatically adjusted according to the amount of steam ejector located upstream of the condenser.