How to reduce the vacuum level of the evaporator?
Thread Content
The evaporator uses a direct condenser combined with an ejector for vacuum creation; the pumping capacity is 1500 L/h. The condenser is equipped with a centrifugal pump of 4 kW, with a flow rate of 12.5 m3/h and a head of 20 m； The ejector is equipped with a centrifugal pump of 4 kW, with a flow rate of 12.5 m3/h and a head of 32 m ； The designed vacuum level for the evaporator is -0.06 MPa(g). Once the vacuum system was started, the vacuum level reached -0.09 MPa(g) in less than 1 minute. With a high vacuum level, the volume of secondary steam is large, and its rise speed within the evaporation chamber is fast. Therefore, to adjust the vacuum level to the designed value of -0.06 MPa(g), how should this be done? I can think of 2 methods: ① Raise the temperature of the circulating cooling water ； ②Reducing the flow rate of the circulating cooling water: Method ① is difficult to control, as the water temperature remains almost unchanged. Moreover, PPR pipes are used, and when the temperature exceeds 60°C, these pipes become soft; therefore, this method is not applicable ； ‘ Method 2: Adjust the outlet valve of the centrifugal pump connected to the injector. Currently, the opening degree of the centrifugal pump’s outlet valve is 1/2, yet the vacuum level remains at -0.08 MP(g) ； Gentlemen, how can this problem be solved?
Where should the vacuum-breaking valve be installed in the pipeline, and is it possible to set a specific vacuum level?
According to the price mentioned above, to break the vacuum at the valve, a control valve can be used, which is linked to the pressure in the buffer tank; alternatively, a stop valve can be added for manual adjustment. The valve is installed on the steam pipe, with a bypass route that leads to the atmosphere；
Isn’t that equivalent to air leaking into the pipeline, with non-condensable gases being drawn in by the vacuum system? I think doing that is a waste of energy.
Install a vent valve on the pipeline leading to the vacuum pump. A chain mechanism can be used, with the vacuum level set to regulate the opening degree of the vent valve.
①Add a damn vacuum valve； ②Apply frequency conversion to the motor in order to reduce its pumping speed and thus lower the vacuum level. It seems that the second option is better
I have a direct condenser + ejector; there is no vacuum pump. Also, does the relief valve function to allow air in or to drain water?
Centrifugal pumps are small, and adding variable frequency control is expensive. It’s better to adjust the centrifugal pump outlet valve directly.
A ejector is what creates a vacuum (a water jet vacuum pump); a vent valve is installed on the intake pipeline to allow air to enter.
The ejector is installed at a high height (11 meters), making it inconvenient to operate the valves manually (no automatic control). Is it possible to adjust the flow rate of the circulating water?