SPECIAL SECTIONRevamping of Billet Reheating Furnace

By changing the design of the roofand combustion system of the 35

tonnes/hr furnace at ISWP, Jamshedpur(a subsidiary of Tata Steel), Encon Ther-mal Engineers Pvt Ltd (ETPL) was ableto achieve a saving of approximately 10ltr/tonne of furnace oil and increase inproduction of 5 tonnes/hr, the scale losshas been reduced by 0.5 per cent. Thefrequent breakdowns due to failure ofbull nose have been eradicated. The fur-nace has been running successfully formore than three years without break-downs.

BackgroundIndian Steel and Wire Product

(ISWP), Jamshedpur, is a subsidiarycompany of Tata Steel Ltd. It is thecountry’s first and the oldest wire prod-uct company, and was taken over by TataSteel in 2003, when it was declared asick company.

The furnace was designed to produce30 to 32 tonnes/hr. The heating zone ofthe furnace had 9 IIP Encon Burners onthe top of the furnace out of which 4 wereof 5A in size and 5 were of size 4A, thesoaking zone had 9 burners of size 4A.

The furnace had a Bull Nose design.The bull nose of the furnace was watercooled, over the years the water-cool-ing of the bull nose was discontinued dueto which the clients were facing the fol-lowing problems:� Bull nose area furnace refractory

bricks were getting damaged wasfrequently falling, and

� Bull nose area refractory hangingbricks and cast steel hangers weregetting burnt.

Apart from the above, followingwere the constant issues:� Burner blocks were getting damaged

and falling, there was no provisionto replace them without completeshut down of the furnace

� Burner block back plate was gettingexcessively heated in the heatingzone due to refractory failures

� There was failure in the short skidand long skids joints

� Long skids were bending� Recuperator was damaged and leak-

ing� Heat loss due to water seepage in

bottom flue duct� Burners were manually operated and

were choking frequently, and

� High specific fuel consumptions.Encon was approached by ISWP in

January 2009 to carry out a diagnosticstudy on the furnace and suggest themways in which ISWP could eradicate thefrequent bull nose failure.

After carrying out the diagnostics ofthe furnace the following observationswere made:

Table 1: Furnace details

G A Original Design of the Furnace

Figure 1: Failure of Bull Nose

186 Industrial Products Finder, May 2011

SPECIAL SECTIONSPECIAL SECTIONSPECIAL SECTIONIt was observed that the Bull Nose

construction and design were the reasonsfor majority of the failure. Due to gapsin the bull nose the cast steel hangers,which were holding the refractory bricks,were getting heated quickly, the tempera-ture of the hanger and roof near the bullnose was alarmingly above the standard.

Combustion EquipmentIt was observed that the present

recuperator is made of plain tubes andwas only giving a maximum air pre-heattemperature is 1900oC.

In order to achieve a continuous pro-duction of 35-tonnes/hr in the furnacethe heat load of the furnace was calcu-lated and found to be insufficient. Heatload of the furnace was increased and

so was the type of burners in the furnace.The blower size was also found to beundersized for a production of 35 tonnes/hr accordingly the air and oil pipelinealso had to be modified. There was no

Side Walls

Before

Roof

Bull Nose Modifications

After

temperature control system in the dueto which the flow of the fuel was notbeing regulated in the furnace.

Modifications Madein the Furnace

The soaking and heating zone of thefurnace were completely redesigned.The bull nose of the furnace was re-placed with a camel hump design. Sideburners were given in the heating zoneinstead of top burners. The design ofthe hanger was changed and state of theart refractory lining was used instead ofthe conventional lining for the roof.

To increase the firing rate in the fur-nace Encon high velocity burners of size4A were used in the sidewalls instead of4 IIP-Encon 5A burners and 5 IIP-Encon4A burners on the top of the furnace, theburners in soaking zone remained thesame.

The firing rate was increased from1350 ltrs/hr to 1665 ltrs/hr. The blowercapacity and the size of air and oil pipe-line were also changed accordingly. Level1 temperature controls were provided withwhich the quantity of air and oil werealtered according to the temperature feed-back from the furnace.

By carrying out the above changesISWP is deriving the following benefits:� Fuel consumption has come down

to 32.6 ltrs/tonne of steel produced.� Scaling is down to 1per cent� There has been no failure in the fur-

nace for almost 3 years the furnacehas been operational, and

� The furnace is constantly producingsteel at the rate of 35 tonnes/hr.

(Contact: Mr Puneet Mahendra,Encon Thermal Engineers Pvt Ltd, 297,Sector 21-B, Faridabad, Haryana 121001. Mobile: 099714-99079. Tel: 0129-4041185, 4047847. Fax: 91-129-4044355. Email: pm@encon.co.in) �

G A Original Design of the Furnace

188 Industrial Products Finder, May 2011