Introduction aux applications du variateur de fréquence moyenne tension en métallurgie
2010-1-6 15:50:42

I. Application du variateur de fréquence haute tension en métallurgie.

1. Gamme d’application
Les équipements de production de l’aciérie peut être divisés en équipements à ajustement de vitesse et équipements sans ajustement de vitesse. Tous les équipements nécessitant l’ajustement de vitesse peuvent utiliser un variateur de fréquence haute tension VFD.
Ils sont divisés en type de besoins de techniques de production et en type de besoin d’économie d’énergie. Pour des besoins en techniques de production, on a besoin de démarrage en douceur et del’entraînement pour laminoir. Une autre application importante du VFD est l’économie d’énergie pour les pompes et ventilateurs, comme le ventilateur de dépoussiérage, la pompe à boue et le système de circulation.

In term of production process, VFD applies in coking, furnace, steel refining and steel rolling. 1#, 2# fan of Baoshan Steel Plant, rolling machine of High Speed Wire Plant, R3 rolling machine of 2050 Heat Rolling Mill all use high voltage VFD. VFD also applies in most SA dusting fan system. It can improve operation effect of dusting system.

2. VFD application in primary dusting system

2.1 Technics period

A-B: add waste steel, about 1 minute.

B-C: fan acceleration, 1min for temporary, can be adjusted

C-D:oxygen blowing, about 12 min

D: fan starts to decelerate

D-E:temperature sample, about 2 min

E-F: steel output, about 2 min

F-G:slag splashing, about 3 min

Whole technics period needs 26 min. High speed time (C-D) is 12min. High speed is 45Hz temporary and can be adjusted. Low speed is 5Hz temporary and can be adjusted. Set up limitation and down limitation by upper PC in remote control.

2.2 Energy saving effect

Fushun Xinfugang Steel Plant uses high voltage VFD for all PA fans.

Before reform with VFD, 1＃2＃3＃ manchine are in the same state. After reform with VFD, 1# fan is drived by VFD, 2# and 3# fans are driven by hydraulic coupling. Here are data:

Compared with hydraulic coupling control , power consumption of steel reduces 3.05kW.h/t;

According to forecast, 1# will output steel 350000t, power price is 0.44yuan/kW.h, yearly cost saved: 350000t×3.05×0.44＝469700yuan (USD69070)

3. VFD application in SA dusting fan

Furnace 750m³ is a new project. In process of iron output, there are two problems. First,
furnace mouth discharges much red-brown gas which pollutes environment. next, in direct on line state, valve adjustment is used to satisfy refining technics. Much power is wasted on valve. In order to solve these problems, the plant use high voltage VFD for dusting fan.

3.1 Original technics

Original design of dusting fan is constant speed without any throttle adjustment device. Speed of fan can not be adjusted. Look at following drawing:

A-B: time of iron output

B-C: time of no iron output

High speed during iron output, low speed during no iron output

3.2 Reform with VFD

Dusting fan runs in very low speed when there is no iron output, no need to run in full load. Variable frequency operation ensures technics and saves energy.

Harsvert-A VFD work process:

Site informs personnel to control VFD speed (local control and remote control via upper PC). When plant outputs iron (A-B), VFD runs in high speed. When no iron outputs(B-C), VFD runs in low speed. Personnel can set according to site state. It can realize that motor reaches highest speed before 5min of opening mouth and lowers to lowest speed after 5min of blocking mouth.

Control system of VFD is following:


Technics drawing after VFD reform

3.3 Energy saving

Motor parameters:

Rated power: 630KW

Rated voltate:6kV

Rated current: 82.9A

750 furnace has been running well since VFD was put into operation. It can satisfy technics requirement and save much energy.

High speed stage accounts for 40% time (output iron 45min, daily output 13 furnaces). Because of high power factor, current reduces to 52A.

Make statistic for high/low speed time according to VFD operation record. Yearly work time is 8600h,

P_{high speed}=1.732×6×52×0.96×8600×40%=1784000yuan (USD 262352)

P_before=1.732×6×82.9×0.8×8600=5927000yuan(871617)

Yearly energy saving rate is more than 50%.

II. Concluding remarks

With competition increasing, energy saving and emission reduction are key points for enterprise development in future. Although VFD cost is big, it has replaced other speed adjustment modes as its high repay rate, high reliability and high automatization level.