Vapour Injectors for Low Pressure Heater Evacuation Systems

Invention patent number: ZL 2014 1 0407667.3

1. Features:
   During the start-up of the unit, more steam will enter the condenser when the boiler ignites the steam turbine to warm up. If a certain vacuum is not established in the condenser, steam and water will enter the condenser to form a positive pressure, which will damage the equipment. The establishment of vacuum in the condenser is an essential condition for the turbine to rush. When the condenser and some low-pressure equipment (such as condensate pump, drain pump and some low-pressure heaters, etc.) are in normal operation, the interior is in a vacuum state.
   Because the pipes and shells are not tight, air will leak in, thus destroying the condenser vacuum and endangering the safe and economic operation of the steam turbine. At the same time, the partial pressure of air in the condenser increases, which leads to the increase of dissolved oxygen in condensate, thus aggravating the corrosion of thermal equipment and pipelines. The existence of air also increases the heat transfer resistance in the condenser, affects the cooling of the exhaust steam of the steam turbine by circulating cooling water, and increases the auxiliary power consumption. Therefore, when the condenser is running, the air must be continuously pumped out.
 
 In a word, the functions of the vacuum pumping system are:
(1)establishing condenser vacuum at the initial stage of unit start-up;
(2) Keep the condenser vacuum during the normal operation of the unit to ensure the safe and economical operation of the unit. 
    The vacuum pumping equipment of condenser mainly includes air extractor and vacuum pump. The vacuum pumping system of water jet air extractor is widely used in domestic large and medium-sized units because of its simple system and reliable operatio

2. Structure and working principle of water jet air extractor:
   In modern power plants, the jet air extractor is the most widely used one, which has the advantages of compact layout, simple structure, convenient maintenance, reliable operation and the ability to establish the required vacuum in a short time. Jet air extractor can be divided into steam jet air extractor and water jet air extractor according to different working media.

 Therefore, at present, large-capacity units in China adopt water jet air extractor, which is mainly composed of working water  inlet, working nozzle, mixing chamber, diffuser and check valve.
   Vacuum system of water jet air extractor. It consists of a water jet air extractor, a water jet pump, a water jet tank and a connecting pipeline. The exhaust of each low-pressure heater, condensate pump and drain pump flows into the condenser through the exhaust pipe, and the condenser is connected with the working room of the water jet air extractor. The water from the jet tank from circulating water or deep well is boosted by the jet pump (one is in normal operation and the other is standby) and then pumped into the jet air extractor. The high-speed water jet from the nozzle in the air extractor generates a high vacuum in the working room to extract the gas-steam mixture in the condenser, and these gas-steam mixtures return to the injection tank after being expanded.


3.Model description


4.Product and unit packages table