Author: Site Editor Publish Time: 03-19-2020 Origin: Site
Abstract:
Mainly introduces the transformation example for Tangshan, Hebei province Qian 'an Xinda iron & steel Co. LTD. Through the technical analysis and test verification of the transformation, it is shown that the energy saving effect is obvious after using the MV frequency drives system, and the operating condition of the equipment is also greatly improved.
During the process of smelting, hot molten iron and the air produce a great deal of flue gas. The smoke will pollute the environment, and it will cause harm to the workers on site. In order to reduce pollution and improve the working environment, it is necessary to add dust removal fan to the smelting furnaces.
1. Dust removal fan process
In the process of smelting in a steel plant, each smelting cycle can be divided into different time periods, in different time periods; the work of the dust removal fan will also be different. We use Hebei Tangshan Qian an Xinda iron & steel Co.LTD as example.
The converter primary dust removal system has two sets of dust removal fans, one of which is used as standby;
The secondary dust removal system has a dust removal fan.
The converter blowing process is as follows:
A to B is the time for adding iron and scrap, about 2 minutes;
B to C is the fan speed time, about 30 seconds, adjustable;
C to D is oxygen blowing time, about 15 minutes;
D point fan starts to decelerate, about 30 seconds, adjustable;
D to E is the sampling time for temperature measurement in the furnace, about 2 minutes;
E to F is tapping times, about 2 minutes;
F to G is slag splashing time, about 3 minutes;
The entire blowing process cycle is about 25 minutes, of which the high-speed time (C to D) is 15 minutes.
Figure 1 Blowing process cycle
There are high requirements for dust removal during the oxygen blowing process, and the dust removal fan is required to run at high speed. However, in the process of adding iron and scrap steel, temperature measurement and sampling in the furnace, tapping, and slag splashing, the requirements for dust removal are lower, low speed is enough. According to the actual measurement, the rise and deceleration time of the dust removal fan can be combined with the calculation of the low speed operation time, which has less influence on the result.
2. Transformation solution
2.1 System parameters
Motor model | YKK500－2 | Rated voltage | 10KV |
Ranted current | 51．9A | Rated power | 800KW |
Rated power factor | 0．87 | Rated speed | 2985rpm |
Actual working current | 30～32A | Actual power factor | 0．82 |
Manufacturer | Jiangsu Xianda explosion-proof motor co. LTD | ||
Table 1 parameters of the primary dust removal fan nameplate
Motor model | YKK500－6 | Rated voltage | 10KV |
Ranted current | 45．2A | Rated power | 630KW |
Rated power factor | 0．856 | Rated speed | 994rpm |
Actual working current | 40～45A | Actual power factor | 0．83 |
Table 2 parameters of the secondary dust removal fan nameplate
Besides:
Annual running hours of primary dust removal fan: 7500h;
Annual running hours of secondary dust removal fan: 5000h;
Electricity price: 0.5 yuan / kWh
Before the transformation, the dust removal system mainly used a hydraulic coupler to adjust the operation speed of the dust removal fan. There were disadvantages such as poor control accuracy, narrow speed adjustment range, low efficiency, and large loss.
2.2 Speed control requirements
This project adopts two sets of medium-voltage frequency drives equipment produced by Shanghai STEP Electric Co., Ltd., ME800-0800-T10-PA for primary dust removal fan and ME800-0630-T10-PA for the secondary dust removal fan.
The dust removal fan has two main working states. Correspondingly, the drives presets two speed points. Speed point 1 corresponds to the high speed operation status of the dust removal fan, and speed point 2 corresponds to the low speed operation status of the dust removal fan. After field measurement, for the first dust removal fan: when the input frequency is 40Hz, the dust removal fan can be guaranteed to run at a high speed; when the input frequency is 25Hz, the dust removal fan can be kept at a low speed. For the secondary dust removal fan: when the input frequency is 45Hz, the dust removal fan can be guaranteed to run at a high speed; when the input frequency is 25Hz, the dust removal fan can be guaranteed to run at a low speed. In each blowing process cycle, the proportion of dust removal fan working at high speed is: 15/25 = 60%; the proportion of dust removal fan working at low speed is: 1-60% = 40%. At the same time, due to the different roles of the primary fan and the secondary fan, their actual operating conditions also differ. The details are as follows:
Speed point | Fan model | Fan operating state | Corresponding frequency | Proportion |
1 | Primary fan | High speed | 40Hz | 60% |
2 | Primary fan | Low speed | 25Hz | 40% |
1 | Secondary fan | High speed | 45Hz | 60% |
2 | Secondary fan | Low speed | 25Hz | 40% |
Table 3 operating state diagram of the dust fan
At the same time, the drives also provides excellent HMI.
The staff can modify relevant parameters through the HMI according to the field conditions, and adjust the running state of the dust removal fan in time to ensure the dust removal effect.
2.3 System configuration and site photos
According to the site working conditions and motor technical parameters, our company is equipped with two ME800 series medium -voltage drivess on the site after field inspection, the models are: ME800-0800-T10-PA * 1, ME800-0630-T10-PA * 1 and equipped with an automatic bypass system to ensure the safety and continuity of production.
FIG. 2 Automatic bypass cabinet
The automatic bypass system is mainly composed of three vacuum contactors: KM1, KM2, and KM3. KM2 and KM3 have a mechanical interlock function and cannot be closed at the same time to protect the drives.
● In the frequency conversion state: KM1 and KM2 are closed, KM3 is open, and the load runs in the frequency conversion state;
● In the power frequency state: KM1 is disconnected from KM2, KM3 is closed, and it runs in the load power frequency state.
3. Energy-saving effect
3.1 Power consumption of dust removal fan before transformation
According to the operation parameters in table 1 ~ 4, it can be obtained：
(1) The annual power consumption of the first dust removal fan
(2) The annual power consumption of the secondary dust removal fan
3.2 Power consumption of dust removal fan after transformation
After transformation, the power consumption calculation is performed according to the engineering experience formula.
(1) Annual power consumption of the first dust removal fan
When the dust removal fan runs at a frequency of 40Hz, the speed is 2450rpm.
(2) Annual power consumption of the secondary dust removal fan
According to on-site calculations, when the dust removal fan runs at a frequency of 45Hz, the speed is 900rpm.
3.3 Energy-saving effect
3.4 On-site energy saving operation data
STEP performed a comparative test on the power consumption of the motor under the power frequency condition and the frequency conversion condition. The details are as follows:
Medium-voltage drives model | ME800-0800-T10-PA | ME800-0630-T10-PA | ||
Load type | First dust removal fan | Secondary dust removal fan | ||
Motor power | 800KW | 630KW | ||
Running condition | In power frequency state | In frequency conversion state | In power frequency state | In frequency conversion state |
Starting time | 2011/4/20 12：15 | 2011/4/21 10：27 | 2011/4/24 12：15 | 2011/4/23 10：27 |
Meter reading | 1431.3 | 1418.1 | 473.1 | 454.8 |
Finish time | 2011/4/20 18：15 | 2011/4/21 16：27 | 2011/4/24 18：15 | 2011/4/23 16：27 |
Meter reading | 1432.2 | 1418.8 | 475 | 456.1 |
Total power consumption（KWh） | 0.9×4000＝3600 | 0.7×4000＝2800 | 1.9×2000＝3800 | 1.3×2000＝2600 |
Average power consumption (per hour) | 3600/6＝600 | 2800/6＝437 | 3800/6＝634 | 2600/6＝434 |
Energy saving per hour（KWh） | 600－437＝163 | 634－434＝200 | ||
Power saving rate | 163/600＝27.2％ | 200/634＝31.5％ | ||
The electricity price is calculated at 0.5 yuan / KWh, and the annual electricity savings are:
(1) Electricity saving of the first dust removal fan: 163 × 7500 × 0.5 = 61.125 million yuan(86,692 USD)
(2) Electricity saving of the secondary dust removal fan: 200 × 5000 × 0.5 = 50 million yuan(70,913 USD)
Total: The annual electricity saving is 111,125 million yuan(157,605 USD).
