Variateur de fréquence moyenne tension dans système de drainage de gaz de mine de charbon
2010-1-18 9:57:30
1. Préface
La production annuelle de la première mine de Chongqing est maintenant de 1500kt/a. Selon le plan de la compagnie, la production de charbon brut va monter graduellement jusqu’à 2400kt/a. Avec la production et l’exploitation accrue, les risques d’influence du gaz sur la production et le développement dans les mines est de plus en plus grand. Le drainage du gaz via des pompes dans les remblais peut contrôler la quantité de gaz sur la taille et dans le système de retour d’air, et limiter ce dernier, pour qu’il ne soit pas supérieur aux règles de sécurité.
Durant le drainage du gaz dans les remblais, si la quantité de drainage est trop grande, de l’air frais risque d’entrer dans les remblais et d’engendrer un feu. Si la quantité de drainage est trop faible, la concentration de gaz sur la taille est supérieure aux règles de sécurité. Aussi, après investigation et comparaison, la mine de charbon a choisi le variateur de fréquence VFD de Leader&Harvest pour ajuster la vitesse de la pompe. Le variateur de fréquence VFD peut optimiser les paramètres de gaz et économiser de l’énergie.

2. Technics and main parameters

There is a drain pipe of diameter 1000mm which is in gas lane of goaf bottom and comes to pump room. Pump is water ring vacuum pump, model SKA-720. Please see technics diagram in following:

Here are parameters:

2.1 Pump parameters

Model: SKA-720

Rated speed: 340r/min

Max drain flow:  635m³/min

Ultimate vacuum: 160MPa

2.2 Motor parameters

Model: YB63052-4

Rated power: 900kW

Rated voltage: 6kV 

Rated current: 104.2A

Rated speed : 1483r/min

Power factor: 0.87

3.VFD structure

3.1 Harsvert VFD is composed of phase-shifting transformer, power cells and controller. Five power cells make up of a phase. Please see following diagram:

3.2 VFD parameters

Model: HARSVERT-A06/110

Power: 900kW

Rated output current: 110A

Input power factor: 0.95

VFD efficiency:>0.96

Frequency resolution: 0.01Hz

Overload capacity: 120% for 1min and 150% immediately

Analogue input: 0～10V/4～20mA

Analogue output: 0～10V/4～20mA

Accelerating/decelerating time: 0.1～3000s

Digital input/output: 4 routes output/4 routes input

Cooling type: air cooling

3.3 Main circuit

Gas drain pump as well as main ventilation blower is main equipment in coal mine. In the light of safety regulation of coal mine, power is supplied by double routes. There are two pumps in room, one work and one standby. So scheme of “ VFD drive two” is selected. Its main diagram is following:

System can implement following operation modes:

a.       With bus I supplying power, VFD drives 1# pump, consisting of QS1, QF1, QS3, QS7.

b.      With bus I supplying power, VFD drives 2# pump, consisting of QS1, QF1, QS3, QS8.

c.       With bus II supplying power, VFD drives 2# pump, consisting of QS2, QF2, QS4, QS8.

d.      With bus II supplying power, VFD drives 1# pump, consisting of QS2, QF2, QS4, QS7.

e.       With bus I supplying power, 1# pump runs in direct on line, consisting of QS1, QF1, QF5.

f.       With bus II suplying power, 2# pump runs in direct on line, consisting of QS2, QF2, QS6.

3.4 VFD installation and commissioning

a. Draining gas of pump room is inflammable and explosive gas. All equipments in pump room are explosion proof. But VFD is non-explosion proof device, it should be installed in an isloated room.

b. After installation and commissioning, gas draining system puts into service. Make statistic for the system when pump runs in 30~50Hz. Here are average values:

4. VFD effect in gas draining system

4.1 It meets demand of working condition

Goaf draining system is used to control gas amount not beyond safety regulation, thereby ensuring safe production of mine. In the light of survey, pump usually runs in 35~45Hz. Operation frequency is determined by distance of coal face and drain tail hole. When coal face is close to drain tail hole, frequency is low. Otherwise, frequency is high. Measure gas parameters perodically, analyse and determine operating frequency of pump. In this way, system can ensure gas amount not beyond safety regulation, and ensure fresh air not to enter goaf, avoiding natural fire accident. So raw coal production is enhanced a lot.

4.2 Soft start

Because of big power, start time is long and start current is big during direct start, which threatens motor insulation and also brings impact on power gird and mechanism. VFD can implement soft start and soft stop with following advantages:

a.       Impact on motor and other equipments during start and stop is eliminated. Lifetime of pump and motor is extended.

b.      VFD control limits impact on power grid during start, reduces peak start power loss.

c.       With speed down, lubrication condition of equipments is improved and driving mechanism failure is reduced.

4.3 Energy saving effect

4.3.1 Energy saving calculation

Pump usually runs in 35~45Hz and mostly in 45Hz. Average work time is 350 days(maintaince needs one day per month),

a.       power consumption in 50Hz:

b.      power consumption in 45Hz

c.       yearly energy saved:

Power price: 0.5yuan/kWh, so 707000yuan (USD103970)is saved.

4.3.2 Power factor is improved

Rated power factor of motor is 0.87. VFD can raise it up to 0.95. So power quality is heightened and power cost declines.

5. Concluding

In gas draining system of Chongqing First Coal Mine, medium voltage VFD controls gas amount of coal face and air return system effectively. It ensures safe production and saves considerable energy.