By the book “principle of steam turbine”,we know that steam turbine equipment in the process of starting and normal operation, it need to pulls out the gas that do not condense in the equipment (especially the condenser) pipeline to maintain the vacuum of the condenser and improve the heat transfer effect, improve the steam turbine thermal efficiency of the equipment. Thus, the extraction equipment made by the vacuum degasser for drilling safety, power pump or cooler, soda pipes, valves, etc has become an important part of the condensing equipment.
There are many types of vacuum degasser, according to its working principle they can be divided into positive displacement (or mechanical) and jetting two big kinds. Volumetric ejector is using moving parts in the pump shell of continuous rotary or reciprocating motion to make the volume of the centrifugal pump shell studio produces extraction, which is used for condensing steam power station equipment of rotary piston vacuum pump, mechanical pump and liquid ring pump. These mechanical vacuum degasser for drilling safety, some machine’s structure is more complex, some machine’s build vacuum time needed is too long, some machine’s work is not reliable, therefore, our country at present mainly adopts the jetting air extractor. Flow jet ejector according to its working medium and can be divided into steam jet ejector and water jet ejector two kinds. They are all using fluid with certain pressure, which got inflation accelerated in the nozzle, to leave the inhaling indoor low pressure air at high speed. Flow jet ejector has no moving parts, it has low manufacturing cost, stable and reliable running, can cover an area of an area small, can set up a vacuum in a relatively short period of time (usually 5 to 6 min), and it can recycle water.
The description and analysis of the working process
Steam jet vacuum degasser is mainly composed of nozzle, mixing chamber and the divergent tube three parts, its basic structure is shown in figure 1.On the structure, working nozzle used the scaling of the structure of nozzle, this structure can get supersonic gas flow at the exit. Between the mixing chamber and the divergent tube there is also a section of pipes, its role is to make the working steam and suction gas fully mixed, to reduce the loss of sudden compression. To highlight the main characteristics in the working process of the steam vacuum degasser for drilling safety, we have to take the working medium within the ejector flow as the ideal gas processing, and assumes that the flow of working medium inside the air extractor is a one-dimensional steady-state adiabatic flow.
The role of the vacuum degasser for drilling safety
Vacuum degasser for drilling safety is used to pull out the air that leaked into the condenser and the gas in the steam continuously, in order to keep the condenser always in high vacuum. The merits of the ejector performance can influence of the size of the condensate gas absolute pressure in the vessel, it plays an important role to the safe and economic operation of the unit. In all kinds of power plants, the commonly used vacuum degassers for drilling safety have ejector emanation and main water jet ejector two kinds.