SAIL SMS-II, Bhilai, India Commissioning of 130 tons RH Degasser Unit Metals Technologies 1
Production increase through approved technologies The challenge: This project was one of the most critical projects handled by Siemens VAI, considering the fact that this was a complete turnkey project involving civil, structural and erection of plant and equipment, along with supply of almost 1000 tons of equipment and structures. The second RH degasser unit in SMS-II is planned to increase the production of rail steel by another 0.8 million tons per year to cater to the increasing demands of Indian Railways, and also to produce the critical slab grades which will be cast in the new slab caster which is presently in erection stage. Grades of steel to be treated in this unit shall be high carbon rail steel, low carbon, medium carbon, line pipe steel (API X 65, X 70), EDD, ultra low carbon, Extra Deep Drawing Quality, boiler, high tensile grades and low alloy steel. The unit shall operate with a nominal heat size of 130 tons of liquid steel. The average number of heats to be treated per day in this unit shall be around 24 heats per day. Our solution: The team involved four consortium partners, namely Siemens VAI MT Germany, Siemens VAI MT India, BSBK and Beekay Engineering. BSBK & Beekay Engineering are prominent local parties who were responsible for carrying out the civil and structural jobs as well as erection along with supply of majority of mechanical equipment and structures. The consortium was led by Siemens VAI MT Germany. However, the total coordination with the client, consultant and other consortium partners was handled by Siemens VAI MT India. Siemens VAI had earlier, in 2001, installed the first RH degasser unit at SAIL Bhilai, which is running successfully in the plant and degassing the critical rail grade steels produced by BSP, which is the only steel plant within SAIL producing such grades of steel. Compared to the existing one, the new unit is also designed to add micro alloying elements during treatment. This will be extremely beneficial to the plant for producing slab grade steels. Achieved results: Steadily production The second RH degasser unit in SMS-II of Bhilai Steel Plant has been successfully commissioned on 1st May 2008, the plant now producing steadily as per the operational requirement High-level degassing Presently, the minimum hydrogen level after treatment has been as low as 0.6 ppm, which is significantly less and much better than the guaranteed value. 2
The customer: Name: SAIL SMS-II of Bhilai Steel Plant Location: Bhilai, India Services: Steel Authority of India Limited (SAIL) is the leading steel-making company in India. It is a fully integrated iron and steel maker, producing both basic and special steels for domestic construction, engineering, power, railway, automotive and defence industries and for sale in export markets. With a turnover of Euro 6,2 million, the company is among the top five highest profit earning corporates of the country. 3
High-level degassing Steadily production and a minimum hydrogen level BSP Operation in-charges View of the vessel through camera On-line monitoring from the control room Technical features The main purpose of degassing in an RH unit is to remove the dissolved hydrogen content in liquid steel, up-to a guaranteed figure of 1.3 ppm. Presently, the minimum hydrogen level after treatment has been as low as 0.6 ppm, which is significantly less and much better than the guaranteed value. This is achieved with the help of a strong ejector-condenser system capable of attaining a vacuum level of less than 1 mbar within 3 minutes and a recirculating rate of liquid steel equivalent to 110 tons per minute. The unit is also designed to add alloying elements during treatment, which is an added feature in this unit compared to the existing one. This will be extremely beneficial to the plant for producing slab grade steels. Grades of steel to be treated in this unit shall be high carbon rail steel, low carbon, medium carbon, line pipe steel (API X 65, X 70), EDD, ultra low carbon, Extra Deep Drawing Quality, boiler, high tensile grades and low alloy steel. The unit shall operate with a nominal heat size of 130 tons of liquid steel. The average number of heats to be treated per day in this unit shall be around 24 heats per day. The plant is designed to attain a minimum vacuum level of 0.67 mbar, which has been demonstrated successfully a number of times during the commissioning stage. 4
Commissioning summary 2.5 2 25 20 Minimum vacuum Final hydrogen Degassing time 1.5 15 1 10 0.5 5 0 1 2 3 4 5 6 7 8 No. of heats 9 10 11 12 13 14 15 0 Minimum vacuum achieved versus minimum hydrogen level Consortium partners During the entire tenure of the project, Siemens VAI had worked as a team along with BSP and the Consultant, CET along with the other consortium partners to ensure that the execution was smooth and efficient. Eventually, the satisfaction from the client was evident once the unit reached the rated production capacity without any major problems. This project has further strengthened the long-lasting relationship between SAIL and Siemens VAI and has added to the reputation of Siemens VAI as a reliable partner for the forthcoming major expansion programmes in SAIL. Commissioning The unit was started up on 27th February 2008. Since then, the production of the plant gradually picked up depending upon the availability of heats from the plant and commissioning was effected within the period of 28th April 2008 to 1st May 2008. The entire commissioning period was smooth and the plant could achieve most of the guaranteed parameters in terms of production rating, hydrogen removal and minimum vacuum level. The minimum hydrogen level in the bath after treatment was as low as 0.6 ppm, compared to the guaranteed value of 1.3 ppm for rail grades. The minimum vacuum level during treatment went down to as low as 0.54 mbar, compared to the guaranteed value of 0.67 mbar (during cold trials). The commissioning team After a successful start 5
Main design features Excellent solutions for premium steel quality RH vessel Offtake Salient design parameters of RH Degasser Type Fixed treatment station Average heat weight (tons) 130 Minimum vacuum level 0.1 torr Final hydrogen content <1.5 ppm Design capacity (heats /day) 24 Vacuum system Steam ejectors and condensers Circulation speed (t/min.) 110 Preheating temperature of RH vessel 1400 ºC with gas fired burner lance Lift gas Argon Vessel lifting Winch system Provision of Ferro alloy addition during treatment Yes Production capacity of RH-Treatment plant Vacuum pump system Annual Production ~ 800.000 t Annual working days 310 Required heats per day 24 Treatment time: Degassing 23 min Treatment time: Decarburization 26 min RH Vacuum Vessel Hot off take type Vacuum vessel Snorkel level Snorkels Steel circulation rate Vacuum Pump Design Suction capacity L-type Mono block vessel Approx. 6.000 mm Welded to the vessel bottom 110 t/min 7 ejectors, 3 condensers Approx. 500 kg/h @ 0.67 mbar Alloy addition system Vessel lifting arrangement 6
Utility services Water at vacuum pump Inlet temperature max. 35 C Return temperature approx. 50 C Circulation rate approx. 840 m3/h Cooling Water System, Closed Circuit (machine cooling water) Inlet temperature Approx. 35 C Outlet temperature Approx. 48 C Total circulation rate Approx. 90 m3/h Steam manifold Steam Steam temperature at manifold Steam pressure at manifold Flow rate 20 C superheated 12 bar max 15 t/h, Compressed air Pressure Flow rate 0,3-0.4 Mpa at TOP Approx. 270 Nm³/h Argon Buffer tanks for argon & nitrogen Pressure Flow rates lift gas 1.4 1.6 MPa at TOP Approx. 150 Nm³/h Nitrogen Pressure Total simultaneous flow rate 6-6.5 Kg/cm2 at TOP Approx. 160 Nm3/h Coke Oven Gas Calorific value Total simultaneous flow rate 4.150 4.250 kcal/nm³ Approx. 750 Nm3/h Settling tank Oxygen Pressure Flow rate Approx. 1.2 Mpa at TOP Approx. 300 Nm³/h 7
For further information, please contact: Siemens VAI Metals Technologies GmbH Schifferstraße 22 47059 Duisburg, Germany Phone: +49 (0) 20331820 Fax: +49 (0) 2033182100 E-mail: secondarymetallurgy.metals@ siemens.com Headquarters: Siemens VAI Metals Technologies GmbH & Co P.O. Box 4, Turmstraße 44 4031 Linz, Austria E-mail: contact.metals@siemens.com The information provided in this brochure contains merely general descriptions or characteristics of performance which in actual case of use do not always apply as described or which may change as a result of further development of the products. An obligation to provide the respective characteristics shall only exist if expressly agreed in the terms of contract. Order No.: E10001-M3-A46-V1-7600 Printed in Austria Dispo No.: 21661 K-No.: 28103 SPS SVAI-08-00067 PA 04091. Subject to change without prior notice Siemens AG 2009. All rights reserved. www.siemens-vai.com