Objective
To date, the steelwork's gas from two ld steel plants (nr 1 with three 160 T converters, nr 2 with three 210 T converters) in the Dunkirk plant has been released unused to the environment after cleaning. At the beginning and end of the blast process the gas is more or less non-combustible. But, for most of the time during the blast process, the gas contains a high CO fraction (40%-70%) so that a mean calorific value of 8 400 kj/nm3 is to be expected. The aim of the project is to develop and test a technique for the recovery, storage, distribution and use of this gas. A total of 100 000 toe is to be expected for an annual production of 6 500 000 ton of steel and an energy recovery of 710 mj/ton.
Design and erection of the planned components, adaptation to the existing gas network, modifications to the gas mixing facilities and to the burners of the furnaces fired with gas mixtures were carried out on schedule. First of all the steel work gas was only used in the milling sector to heat pusher furnaces. It was mixed in different ratios with blast furnace gas and coke plant gas. For this purpose, it was necessary to set the burners to the required wobbe index. Extensive measurement and control programmes were developed to permit automatic operation.
A provisional mean CO content of approximately 71% (CO2 = 14%, N2 = 12%) resulted from extensive tests on the composition of the gas mixture during blast operation. This corresponds to a lower calorific value of 9 070 kj/nm3 30-40 % of the steelwork's gas during the blast process seems possible. The results obtained to date show that the target recovery rate of 710 mj/t of casting steel was at least achieved from time to time. The elimination of the detected weak points and further optimization work, which has been planned, lead one to expect the successful completion of the project.
The steel converters foreseen for the recovery of furnace gas are equipped with a special three direction valve to ensure that non-usable gas is discharged via the flare at the beginning and end of the blast process while usable gas is fed into a gasometer with a volume of approximately 100 000 m3. This valve system is automatically controlled depending on the CO content of the gas. Special precautions are necessary to seal the single waste gas lines. These are effected by water joints. A special emergency system takes care of the automatic separation of the gas network from the converter or flare system in the event of danger. The steelwork's gas stored in the gasometer is transferred to the overpressure station via a cleaning facility (electric filter). This station compresses the gas to the required network pressure of approximately 1 600 mmws.
It is planned to use the gas in two ways: either for the enrichment of the blast furnace gas to heat the cowpers. In this case, the coke plant gas used to date can be used to heat pushing kilns instead of oil.
Or for direct use to heat the mills pushing furnaces (hot strip mill and plate mill). In each case, it is necessary to adjust and tune the network, the mixing facilities and the burners (wobbe index). Furthermore, an extension of the automatic control system is planned. A 2 year period is scheduled for the design and erection of the facilities. The choice has been : the first solution. Following preliminary tests and successive commissioning of all components, the actual trial operation of the overall plant is to take place during the second half of 1983. If the results are positive, commercial utilization is to be expected as from 1984.
Programme(s)
Topic(s)
Call for proposal
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DEM - Demonstration contractsCoordinator
59381 DUNKERQUE
France