Optimization and application of TRT equipment for medium and heavy plate

In view of the problems existing in No. 1 TRT turbine unit of medium and thick plate, measures such as turbine transformation, shaft end seal optimization and top pressure regulation control program optimization were taken to ensure the long-term safe and stable operation of TRT, and the daily power generation was increased by 47800 kWh and the average power generation per ton of iron was increased by 7.13 kwh.

Blast furnace top gas residual pressure recovery turbine power generation device (TRT) uses the pressure energy and heat energy in blast furnace top gas to drive the generator for power generation through turbine expansion, and recovers about 30% of the capacity required by blast furnace blower. In fact, it recovers the energy lost by the original pressure reducing valve. This power generation mode neither consumes any fuel, nor produces environmental pollution, and has low power generation cost. It is a major energy-saving project in the blast furnace smelting process, with remarkable economic benefits. There are three sets of TRT power generation supporting blast furnaces of China plate Corporation, including one 10MW generator set and two 12MW generator sets. Due to the lack of blast furnace dust removal system and dechlorination system, the blades are worn, resulting in reduced power generation and high blade repair cost.  The system is optimized through new technology to reduce blade wear, ensure power generation efficiency in the maintenance cycle, reduce maintenance costs and improve power generation.  This optimization transformation has been widely used in TRT power generation system of Tangshan Iron and Steel Co.

Analysis of existing problems

(1) Due to the dust erosion and chloride ion corrosion in blast furnace gas, the thickness of No. 1 TRT blade is reduced, resulting in the increase of the top clearance of moving blade and stationary blade. The measured value reaches 5mm, which is 3mm larger than the design value, which greatly reduces the efficiency of the turbine. In 2015, at the initial stage of unit operation, the daily power generation reached 159000 kwh, the daily power generation before transformation was about 145000 kwh, the efficiency of turbine was about 79%, and the efficiency of generator unit was seriously reduced.

(2) The shaft end seal of No. 1 TRT adopts the combined shaft seal technology of labeling seal + carbon ring seal + N2 seal. The sealing effect is poor, the gas leakage is serious, and the gas concentration in the machine room seriously exceeds the standard. The operators cannot carry out normal spot inspection and maintenance in the machine room, which affects the power generation efficiency, safe and stable operation of the unit.

(3) When the production of blast furnace is abnormal, the sharp fluctuation of top pressure and flow will have an impact on the automatic TRT, resulting in frequent burning of thrust pad and frequent opening of stationary blade at a large angle, which is very easy to damage the linkage mechanism of stationary blade and seriously affect the power generation operation rate of the unit.

transformation scheme

2.1 turbine transformation

Scheme 1: carry out aerodynamic calculation according to the existing operating parameters of blast furnace gas, make use of the old main shaft and bearing cylinder, and optimize and transform the turbine rotor and flow channel.

① The blade is changed to TRT special high-efficiency new blade type, which has high flow efficiency, is not easy to accumulate dust, block and wear resistance.

② The original main shaft and bearing cylinder are processed by laser cladding. After blade replacement and reconstruction, the daily power generation can be guaranteed to be about 175000 kwh.

Scheme 2: carry out aerodynamic calculation according to the existing operating parameters of blast furnace gas, and optimize and transform the turbine rotor and flow channel.

① The blades are changed to TRT special high-efficiency new blade type, and the number of blades is increased. It has high flow efficiency, high efficiency, and is not easy to accumulate dust, block and wear-resistant.

② Redesign and replace the main shaft, inlet ring, diffuser, bearing cylinder and regulating cylinder to improve the channel performance, reduce the scouring of gas on blades and improve the gas flow efficiency. After replacement, the daily power generation can be guaranteed to be about 178000 kwh.

Based on the 355d operation of each unit every year, the annual power generation will increase by about 1065000 kwh. Based on the electricity price of 0.5 yuan / kWh, 532500 yuan will be created in the whole year.

Scheme I costs 1.9 million yuan, scheme II costs 3.95 million yuan, and scheme II costs 2.05 million yuan more than scheme I. Compared with scheme 1, scheme 2 can generate 1.065 million kwh more power each year and create 532500 yuan more efficiency. The excess cost can be recovered after 3 years and 10 months. Due to the long recovery cycle, scheme I is adopted after comprehensive consideration. The turbine is replaced with new moving and stationary blades, the main shaft hub and bearing cylinder are repaired by laser, and the rotor is dynamically balanced again.