For thermal system of M701F4 series "2 on 1" split-shaft unit with gas-steam combined cycle in Huaneng Beijing thermal power plant

its features and start-up mode were introduced.Practical applications show that

problems such as big difference in temperature between upper and lower casing

difficulty in bypass control and high pressure in IP(intermediate pressure) exhaust steam etc.which occur during the steam combination

can be solved by method of combining IP steam first

then HP(high pressure) steam

and LP(low pressure) steam finally.After the improvement of bypass control

the unit can be easily operated during the combination and decomposition of steam.The load is stable and satisfies the request that the unit should start-up and shut-down quickly during peak regulation or two-shift operation.