大型直接空冷机组真空泵的选择

在缺水的西、北部地区将陆续投运一批大型300、600MW直接空冷凝汽器，针对空冷器后的水环式真空泵是否能完全适应空冷机组运行要求的问题，从真空系统运行中漏气量的确定、容量选择和启动要求、对不同运行工况的适应性、空气漏入率与真空容积的关系等方面论述了大型直接干冷机组真空泵抽吸容量的选择和各种运行因素对容量的影响，提出了适合空冷器在运行中的空气泄漏率的意见：(1)直接空冷机组真空泵容量选择可以参照湿冷机组HEI的标准选取，但应注意采用湿冷机组凝汽器的最低运行压力；(2)空冷器设计应注意其逆流段出口的过冷却符合HEI标准的要求；(3)真空泵运行水温过高使真空泵排出的混合气体中的蒸汽分量加大，其数量可以通过计算求取；(4)对600MW直接空冷机组的空气泄漏率应以不大于30Pa／min为宜。

Selection of vacuum pump for large direct dry cooling unit

Since a host of 300 MW and 600 MW direct dry cooling generating units are expected to go into operation in the north and west part of China lacking water, the capacity of vacuum pump of large direct dry cooling steam turbine and the interference of different operating factors were discussed from various quarters of determination of air leakage into vacuum system,capacity selection,starting requirement, adaptability to different operating conditions, and relation between air leakage flow rate and vacuum volume etc. taking water-ring vacuum pump in account whether or not it was able to meet operation requirements of direct dry air cooling units. And suggestions are offered in regard to air leakage flow rate appropriate for directly air-cooled condenser: (1) The capacity of vacuum pump to the direct dry cooling unit can be selected by reference of HEI Standard of wet cooling steam turbine, but a minimum operating pressure of its condenser should be adopted. (2) Outlet subcooling degree of reverse flow section should be in conformity with the requirement of HEI Standard. (3) Excessive operating water temperature of vacuum pump enables a steam component in air-steam-mixture from it to increase. The component can be calculated. (4) The air leakage flow rate to 600 MW direct dry cooling units should not be greater than 30 Pa/min.