RH process is an important out-of-furnace refining method, which has the functions of degassing, decarbonization, temperature compensation, uniform molten steel temperature composition, removing inclusions in steel and so on. Because of its good refining effect and short processing period, it has been widely used in steelmaking.
In the environmental protection relocation project of Chongqing Iron and Steel Company, RH vacuum refining technology was introduced in order to further improve the product structure and steel quality. Since the development of RH vacuum refining technology in 1959, the equipment and process have been mature. The vacuum equipments used in traditional RH process are all multi-stage steam jet pump vacuum system. However, it is found that the vacuum system of multi-stage steam jet pump is restricted by steam from home and abroad, and the steam is moved to comply with the environmental protection of Chongqing Steel. The concept of effective recovery and utilization (the construction of distributed waste heat power station) is studied, and the RH vacuum system is studied.
After investigation, two kinds of vacuum systems are generally used in domestic and foreign vacuum systems: multistage steam pump (widely used in RH, VD, VOD) and dry (mechanical) pump (used in very small tonnage VD, VOD). The comparison and demonstration of the two kinds of vacuum systems show that they can meet the technical requirements of RH process. Therefore, 210tRH vacuum system of Chongqing Iron and Steel Co. The system decides to adopt dry type (mechanical pump) vacuum pump.
The production practice of 210t RH in Chongqing Iron and Steel Co. shows that the metallurgical effect of vacuum system with dry vacuum pump applied to RH can reach or surpass that of vacuum system with multi-stage steam ejector pump. The removal rate of [H] reaches 63.5%, the limit decarbonization capacity is 10 @10-6, and the energy consumption of vacuum system with multi-stage steam ejector pump is 7174 yuan/t lower than that of vacuum system with multi-stage steam ejector pump. Dry vacuum pump is driven by electric energy. Its operation is not restricted by steam pressure and temperature. It can start and stop at any time according to the actual production situation. The production organization is flexible.
The main technical parameters and the general situation of dry type (mechanical pump) vacuum system are as follows:
EVP Series Dry Scroll Vacuum Pump
Technical Parameter:
| Model | EVP1000 | EVP600 | EVP300 | EVP150 | EVP75 | ||||||
| Displacement | 50Hz | l/s | 16.6 | 8.7 | 4.3 | 2.0 | 1.0 | ||||
| l/min | 996 | 522 | 258 | 120 | 60 | ||||||
| m3/h | 59.8 | 31.3 | 15.5 | 7.2 | 3.6 | ||||||
| cfm | 35.8 | 18.7 | 9.3 | 4.3 | 2.2 | ||||||
| 60Hz | l/s | 19.9 | 10.4 | 5.1 | 2.4 | 1.2 | |||||
| l/min | 1194 | 624 | 306 | 144 | 72 | ||||||
| m3/h | 71.6 | 37.4 | 18.3 | 8.6 | 4.32 | ||||||
| cfm | 42.8 | 22.3 | 10.9 | 5.1 | 2.5 | ||||||
| Ultimate pressure | Pa | ≦1.0 | ≦1.0 | ≦2.6 | ≦8.0 | ≦8.0 | |||||
| torr | ≦7.5×10-3 | ≦7.5×10-3 | ≦1.9×10-2 | ≦6.0×10-2 | ≦6.0×10-2 | ||||||
| mbar | ≦1.0×10-2 | ≦1.0×10-2 | ≦2.6×10-2 | ≦8.0×10-2 | ≦8.0×10-2 | ||||||
| psi | ≦1.4×10-4 | ≦1.4×10-4 | ≦3.8×10-4 | ≦1.2×10-3 | ≦1.2×10-3 | ||||||
| Leakage with outlet & air flush port off | 1×10-2Pa·l/s（1×10-4mbar· l/s） | ||||||||||
| Max. inlet /outlet pressure | mpa | 0.1 /0.13 | |||||||||
| Ambient Temperature | ℃/℉ | 5～40 / 41～104 | |||||||||
| Max. moisture disposal capacity | G/h | 60 | 60 | 60 | 50 | 50 | |||||
| Motor | Power | kw/hp | 1.50/2.00 | 0.75/1.00 | 0.55/0.74 | 0.25/0.30 | 0.25/0.3 | ||||
| Voltage | VAC | 380/220 | 380/220 | 220 | 380/220 | 220 | 380/220 | 220 | 380/220 | 220 | |
| Speed | rpm | 1410 | 1425 | ||||||||
| Noise level | dB(A) | ≦63 | ≦63 | ≦63 | ≦57 | ≦54 | |||||
| Inlet/outlet diameter | mm | KF40/16×2 | KF40/16 | KF25/16 | KF25/16 | KF25/16 | |||||
| External dimension | mm | 548×359×397 | 487×316×360 | 457×290×336 | 416×245×277 | 405×225×260 | |||||
| Weight | kg | 52 | 36 | 32 | 18 | 15 | |||||
| Cooling type | / | Air cooled | |||||||||
| Others | / | With timer & air ballast | |||||||||
The 210tRH layout of Chongqing Iron and Steel Co., Ltd. is a three car five bit, dual processing form, and the annual capacity of molten steel is about 2 million 200 thousand T. Vacuum pump adopts mechanical roots pump and screw pump, the maximum pumping capacity is 800kg/h at 67 Pa, and the limit vacuum degree is 18 Pa. The vacuum pump system, top gun system, hydraulic system, ladle trolley system, charging system and energy medium system are all fully automatic controlled by PLC. Temperature control and prediction model, component simulation calculation model, decarbonization model and exhaust gas infrared analyzer are configured.
Vacuum pump is one of the necessary equipments for RH refining equipment. Its pumping capacity and pumping rate directly affect the normal operation and metallurgical effect of RH. The maximum pumping capacity of 210tRH vacuum pump designed by Chongqing Iron and Steel Co. is 800kg/h when the pumping capacity is 67 Pa, which is basically the same as that of domestic steam pump with the same tonnage RH.
The 210 tRH dry (mechanical pump) vacuum pump system at Chongqing Iron and Steel Co. consists of 19 sets (1 set of standby) double-row parallel dry (mechanical pump) vacuum pumps. Each set of dry vacuum pumps consists of 4 Mechanical pumps. The first stage is an IDX1300 screw pump (standard atmospheric pressure pumping capacity 1300m3/h); the second stage is a SN7000 Roots pump (standard atmospheric pressure pumping capacity 1300m3/h); and the second stage is a SN7000 Roots pump (standard atmospheric pressure pumping capacity 1300m3 Quantity 8000m3/h); the third level is 2 HV40000 roots pump (40000m3/h of each pump under standard atmospheric pressure). The screw pump and roots pump use electric energy as energy medium.
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