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Coal dosing systems and process gas burners for lime kilns

Julien Ryckeboer, RnD Senior Engineer, Fives Pillard, Marseille (France)

Baosteel group Corporation limited, the Chinese #1 steelmanufacturer, produces 3,800 tons per day of high qualitydolomite and lime for steel desulphurization for its Baoshanplant (North of Shanghai).

The 5 rotary kilns producing the lime were originally firing

a mix of steel process gas comprising coke oven gas (COG)and converter gas (LDG) whose characteristics are indicatedopposite.

In 2005, Baosteel decided to use mainly COG on a new powerplant and to progressively switch its 5 lime kilns to pulverizedcoal firing in addition to steel process gas.

For the first kiln to be equipped (kiln No.4), Boasteel choseFives Pillard to provide the complete firing system, includingthe coal storage and Stapildos dosing system, coupled withthe Rotaflam Burner (which is able to simultaneously firesteel process gas and coal).

The main characteristics of the firing system are given as follows:

Steel process gas characteristics

Commissioning period 11/2007 02/2008 09/2007 09/2006 05/2008

Max length of conveying line m 110 110 110 110 110

Max coal/petcoke concentration kg/Nm 3.1 3.1 3.1 4.1 5.5

Max COG flow rate Nm3/h 8,570 8,570 8,570 10,000 13,000

Max LDG flow rate Nm3/h 18,000 18,000 18,000 21,000 27,000

Max flow coal flow rate kg/h 5,000 8,572 5,000 7,000 9,000

Line Capacity TPD 600 600 600 800 1,200

Burner power released MW 42 42 42 49 63

Kiln No.4 was commissioning in September 2006.

Baosteel appreciates:

The coal flow stability ensured by the Fives Pillard Stapildos dosing system (1%) allowing the kiln to keep a stabletemperature profile all along the kiln, (and incidentally, limiting the formation of mid-kiln rings).

The flame stability and concentricity thanks to the air impulse of 9 N/MW which avoids ring formations at the hot endzone.

The ability of the burner to provide reactive lime with a low LCV mix of LDG and COG as well as the possibility to warmthe kiln up with only LDG.

CONTEXT

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Stapildos and Rotaflam firing system characteristics

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STAPILDOS principle

The stapildos coupled with the Rotaflamallows Baosteel to produce high reactivitylime (< 200 ml of HCl) with low sulphurcontent (< 0.05%).

The good performance reached on kilnNo.4 led Baosteel to grant Fives Pillard

with the order for the other kilns (1, 2, 3and 5).The characteristics of these lines are givenin the table above.

STAPILDOS building ROTAFLAM burner line #1,#2 and #3

The client has reached its target of being able to fire the kilns with a mix of COG and coal, with up to 100% coal firing, whilstmaintaining high quality lime and reliable kiln operation.Furthermore, the ROTAFLAM coupled with the STAPILDOS coal dosing system gives a high stability and flexibilityto the kiln operation.

These lines have been commissioned with the same success.

CONCLUSION