Research and application of gas - steam combined cycle power generation technology

Gas steam combined cycle (CombinedCyclePowerPlant) power generation unit, referred to as CCPP. Gas turbine is from jet engine technology evolution, it through the turbine compressor will be compressed air, high pressure air in the combustion chamber and a fuel mixed combustion, so that the air acting of rapid expansion, promote power turbine to rotate to drive the generator to generate power. Gas turbine its power generation efficiency is not very high, generally in the 30% - 35%, but the waste heat of the flue gas temperature up 450 - 550 DEG C can through the waste heat boiler again heat recovery converted into steam, to drive a steam turbine and a power, so as to form a gas turbine steam turbine combined cycle power generation, power generation efficiency can reach 58% - 60%, some large units can even more than 60%. Because of the gas turbine rotation continues the acting can be relatively low calorific value of utilization of fuel gas. At the same time, also has a start and stop fast, running load adjustment amplitude and speed characteristics, the technology in iron and steel industry obtained rapid application and for recovery of the blast furnace, Jiao Lusheng production process large fuel gas by-product (blast furnace gas, coke oven gas) for power generation, power generating efficiency is improved, and well meet the need of iron and steel enterprises dynamic balance of gas and reduce the emission.

CCPP in the boiler and turbine can supply steam, can form a combined cycle cogeneration plant. There is a gas compressor (GC) unit in the CCPP system, especially in the low calorific value gas. As is known to all, waste heat boiler and steam turbine is conventional technology, CCPP technology core is gas turbine, gas turbine is generally the floorboard of turbine air compressor, combustor and gas turbine combination. CCPP used in power industry, such as natural gas, heavy oil and other high calorific value fuel, iron and steel plant CCPP to blast furnace gas, and some factories are likely to be mixed with a small amount of coke oven gas, gas calorific value for power generation (1350 - 800) x 4.18kJ/m3, but natural gas 1/6 - 1/10. Low calorific value gas combustion is not stable, gas volume is huge, gas compression power increases, the difficulty of CCPP technology increases.

Low calorific value gas combustion technology mainly has two schools: one is using single cylinder combustor of gas turbine, gas calorific value can be in about 800 x 4.18kJ/m3, products such as abb, Nuovo Pignone; another is multi tube burner combustion engine, used for gas combined cycle power plant (IGCC), calorific value gas 1334 x 4.18kJ/m3, about 10% of the H2 content in the gas and products such as GE and Mitsubishi, Tonghua Iron and steel, Maanshan Iron and steel by the of this unit.

CCPP from equipment layout is divided into two kinds: a single shaft arrangement, namely gas compressor, steam turbine, generator, gas turbine on the same shaft, uniaxial arrangement of high work efficiency, compact layout, covers an area of small; another pivot arrangement, the gas compressor, combustion gas turbine and generator are coaxial, steam turbine, a generator coaxially, the layout of the equipment need two generators, split axle arrangement and the work efficiency is low, covers a large area, but can separate building.

Application of CCPP technology in the steel works

With the construction of 4000m3 blast furnace and its supporting facilities, a large number of blast furnace gas and coke oven gas are produced in the steel plant. The surplus of blast furnace gas is 260000 m3/h (3050kJ/Nm3) and 30000 m3/h (low calorific value is 16410kJ/Nm3). In response to the national energy-saving emission reduction, low carbon production policy calls, while improving economic efficiency, this part of the energy must be fully utilized.

The blast furnace gas is used as the boiler fuel steam turbine power generation and its thermal efficiency can reach 25%; the main advantages are as follows: power efficiency is far more than coal steam turbine power plant. The technology is now used in the domestic large steel plants and the main advantages are as follows: power efficiency far more than coal steam turbine power efficiency. Power efficiency is far more than coal power plant. Changes and other advantages.

Steel companies to increase the use of blast furnace gas and coke oven gas utilization, reduce the operation cost of steel mills, decided to build 1 sets of 150MW gas - steam combined cycle power generation unit.

Selection of CCPP generating set

And process design

CCPP power station was built at the same time, and the coaxial arrangement should be adopted in accordance with the requirements of the design technology of thermal power plant. So this project uses the M701S (DA) type single shaft arrangement unit, the main equipment of CCPP power generation unit is: M701S (DA) type gas turbine (including air compressor), 154MW gas turbine and steam turbine generator, steam turbine, boiler, gas compressor, gas cooler.

The main technology of CCPP generating unit of MITSUBISHI heavy industries, Japan, is: gas system, gas system, air system and steam system.

Gas system. Blast furnace gas and coke oven gas are mixed in the gas mixer, the mixed calorific value is reached 4187 - 4605kJ/Nm3, in order to ensure the stability of gas turbine. Gas mixture

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