Analysis of the current situation of steam turbine and motor drag
The electric motor is now an indispensable rotary drive device in the production process. It covers the production links of all walks of life with the advantages of stable operation, simple start-stop control, low technical content and relatively low maintenance cost. However, large motors (rated) The power is large. The power capacity requirement is high at the time of starting, which easily affects the normal operation of the surrounding equipment; the equipment has high technical content, complicated control mode and speed regulation mode, and high maintenance cost and price.
Turbines have been widely used in electric power, chemical, petroleum, metallurgy, building materials, environmental protection, textile, paper and other industrial fields, and have been widely praised for their superior performance, energy saving and simple structure.
2 Air compressor adopts the initial setting and investment analysis of motor drag
The air compressor is the key equipment in the oxygen generator equipment, also known as the raw material compressor. Since the 40 000 m3/h oxygen generator requires 220 000 m 3 / h of 0. 45 M Pa 0. 5 M Pa of air, the air compressor has a rotating shaft power of 18 500 kW.
First of all, before the factory design, the author believes that technical exchange should be carried out with the air compressor manufacturer. If the air compressor is equipped with a dragging device, the rated voltage is 10 kV and the motor power is 19 800 kW. The domestic power cannot be produced. Only imported ABB or Siemens motors are used; the purchase cost of the motor is high and the delivery period is 18 months.
2. 1 Air compressor motor drag design and analysis
The motor parameters of the air compressor under the same process conditions: the voltage is 10 kV; the power is 19 800 kW; the current is 1 283 A; the power factor is 0. 9. Since the torque is too large when the air compressor is directly started, the starting current is rated. 6 times the current, the voltage drop of the busbar is also very large (required can not be greater than 15%), so a special starting method is adopted:
(1) Start with a transformer-motor unit.
If this kind of starting method is adopted, it is necessary to build a 3 25 MVA, 35 /10 kV substation to supply power to 3 air compressor motors. Three 20 MW air compressor motors are powered by a transformer-motor unit.
According to the minimum short-circuit capacity S m in= 632 MVA of the 35 kV bus, the actual starting current I q = 4 697. 446 A.
Calculate the motor start time as:
Motor starting time = ( GD)2 N r2 /< 365Prm( Uqm2M qp- M j) > = 8. 000 1 470. 000 2 /< 365 20 000. 000 ( 0. 610 2 1. 100- 0. 300) > = 21. 664 calculated that the 35 kV bus voltage drop is 12%, but the 35 kV substation has a large area, and the 35 kV bus voltage drop exceeds the voltage fluctuation requirements of the hot rolling mill inverter, and will be converted to other online units. The operation of the device has an effect, which will cause the inverter to trip.
(2) Start with a thermal resistor.
If this kind of starting method is adopted, it is necessary to build a 3 50 MVA, 35 /10 kV oxygen-making substation to supply power to 3 40 000 m 3 /h oxygen generator, and 3 35 kV power supply from steel east change < 4 >.
According to the minimum short-circuit capacity of the 35 kV busbar S m in = 632 MVA, the minimum short-circuit capacity on the 10 kV side is calculated as S min = 299. 4 MVA.
According to the calculated minimum short-circuit capacity of 10 kV busbar, the current can be controlled within 24 times due to the step-down of the thermal resistor, which meets the starting requirements. However, the thermal variable resistor is used to reduce the voltage and start to occupy a large area. The resistance changes drastically with temperature, which leads to poor control of current and time during starting, and cannot be constant for a certain value, which is relatively dangerous; it will have adverse effects on equipment.
(3) Start with high voltage inverter.
According to the minimum short-circuit capacity of the 10 kV busbar, it can be known that the starting condition is met, the starting is stable, and there is no impact on the power grid; however, the investment cost is high, the domestic production cannot be produced, and the foreign procurement cycle is very long, which will affect the construction progress and the date of production.
Investment Analysis. Comprehensive analysis shows that ensuring the completion of expansion and expansion of the substation in advance is the premise for the commissioning of the oxygen production project. According to the above calculation and analysis, in order to avoid affecting the power supply of other units in the system, the author recommends using high-voltage variable frequency starting method, but combined with the project's production date, Therefore, the above can not meet the requirements.
2. 2 analysis of operating costs of air compressors
(1) 3 40 000 m 3 /h oxygen unit 1 air compressor annual power consumption:
Annual average operating power: 19 800 kW 0. 9; average electricity price: 0. 4 yuan / kWh; annual operating hours: 350 days 24 hours = 8 400 hours; annual electricity fee: 19 800 kW 0. 9 8 400 hours 0. 4 Yuan / kWh = 59 875 200 yuan.
(2) It does not include electricity and daily maintenance costs for each start-up.
3 Air compressor adopts steam turbine dragging initial design and investment analysis
The primary steam generated by the boiler has high temperature and high pressure, and can be well utilized on the steam turbine, and the steam turbine is used to drive the work.
In this case, it can replace the motor to drive the air compressor to do work to save energy. According to the important parameters required for the above air distribution sleeve compressor, a saturated steam turbine of 4.5 M Pa, 450, 19 800 kW can be selected, which is equivalent to replacing the electric motor of 19 800 kW. The use of steam turbines to drag air compressors is not only simple in control, low in cost, but also consumes far less energy than the motor runs, creating continuous economic benefits for the enterprise.
3. 1 Air compressor drag design and analysis
A saturated steam turbine of 4.5 MPa, 450, 19 800 kW is used under the same process conditions. In order to meet the steam demand of 70 t / h required by the steam turbine, after comprehensive consideration, two new 220 t / h boilers need to be built, and the construction period is short, which can be completed before the oxygen production project is put into production.
The newly built boiler adopts the operation mode of purely burning gas, and the gas is produced by the ironmaking blast furnace; this not only makes effective use of energy, but also environmental protection, which greatly reduces the cost; secondly, it builds two sets of 220 t/h according to the comprehensive consideration of regional development. The boiler not only solves the heating problem in the factory area and living area, but also can ban and dismantle small boilers to meet environmental protection requirements.
3. 2 analysis of operating costs of air compressors
(1) 3 40 000 m 3 /h oxygen production air compressor annual steam consumption: average steam price: 64 yuan / T; hourly dosage: 64 yuan / T 70 = 4 480 yuan / hour; annual operating hours : 350 days 24 hours = 8 400 hours; annual consumption costs: 70 8 400 hours 64 yuan / T = 37 632 000 yuan.
(2) Excluding daily maintenance and repair costs.
4 operational economy, reliability analysis
The steam inlet pressure of the steam turbine is generally 4.5 M Pa, 450, power 19 800 kW, exhaust - 0. 09 M Pa, speed 4 550 r / min, in the arrangement, the steam station of the steam turbine is arranged The lower part of the steam engine body directly installs the steam engine body, the governor and the water pump above it, and has a small footprint and is convenient to install and use. The speed control system of the unit adopts the electro-hydraulic adjustment mode, and uses the US ICS TC3000 control system to adjust the turbine guide vane opening to achieve the purpose of speed regulation.
The motor drives the compressor to run. Because the compressor speed is high, the gearbox connection must be installed between the compressor and the motor to meet the actual operation requirements. As shown, the motor needs to overcome the large speed in order to reach the rated speed when the load is started. The load torque, and this has a great impact on the grid.
By using a steam turbine instead of a motor to drag the load, controlling the high-speed regulating valve of the steam turbine can increase the rotational speed slowly until the rated rotational speed, so that the starting is not only relatively linear, but also the rotational speed is gradually increased, the overcome torque is relatively small, and the operation is stable and reliable.
5 investment costs
In this study, the motor traction and supporting high-voltage frequency conversion devices and substation construction costs totaled 65 million yuan (1 unit); the selection of the above-mentioned steam turbines required a steam turbine and auxiliary equipment and boilers, with a total investment of about 80 million yuan.
6 operating costs
If it is driven by a motor, it will cost about 59,875,200 yuan per year for 8 400 hours of full-load operation. With the steam turbine unit driven above, the cost of steam consumed is about 37 632 000 yuan, and the annual cost savings is 22 243 200 yuan compared to the motor drive.
Combined with the comparative analysis of different drag modes (as shown), although the use of steam turbine drag is higher than the investment cost of using variable frequency motor, the operating cost is much lower than the latter; one year (running 8 400 hours) Saving 2,224.32 million yuan for enterprises, the investment in steam turbines can quickly recover the cost.
7 Conclusion
In the case of saturated steam, steam turbines can be used as a power source to replace the motor, avoiding direct emptying or unreasonable waste of resources.
With the development of chemical refining petrochemical, metallurgical light industry and textile industries, as well as the need to save energy, industrial steam turbines will be more widely used. With the development of production process systems such as petrochemicals to large-scale and high-efficiency, the steam parameters and power level ranges of industrial steam turbines will also increase accordingly. In order to better save energy and make rational use of low-grade waste heat, the development of small industrial steam turbines using steam or other working fluids will receive increasing attention.
Chocolate Fountain,Chocolate Fountain Machine,Fondue Fountain,Chocolate Fondue Fountain
CIXI XINPU JIANKE ELECTRIC APPLIANCE FACTORY , https://www.cxjianke.com