Dust bag
The dust bag is used in blast furnace systems for the dry, coarse cleaning of the top gas and is directly exposed to the gas emerging from the furnace head via a supply line.
Designs and operating principle
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1) the simplest type, 2) with a conical supply line, 3) with an additional dust container and apex cone
The basic design of a dust bag corresponds in principle to that of a large steel cylinder with a diameter of about 12 m, which is closed at the bottom by a funnel-shaped dust collector with an extraction device.
In the simplest case, the gas enters the dust bag through a downwardly pointing supply pipe, which is attached to the side wall of the cylinder, and exits again via a discharge pipe attached to the ceiling. Two physical principles separate the dust from the gas during passage:
- Due to the inertia of the dust particles, the change in direction between the inlet and outlet pipes leads to the fact that they continue to fly in a straight line in the direction of the inlet pipe pointing downwards.
- Due to the strong reduction in the flow velocity due to the increase in cross section from the line to the dust bag, the gas loses its power to carry the dust with it. It detaches itself from the current, trickles down into the collecting funnel.
A dust bag of this simple design can separate around 65% of the dust.
The separation efficiency can be increased by also attaching the supply pipe to the ceiling and widening it in a conical shape and protruding a little into the dust bag. The forced change of direction to 180 ° increases the degree of dust removal to around 80–90%.
An additional dust container at the lower end of the funnel, which prevents the dust from being swirled up, brings about a further improvement in efficiency of around 5%.
If the dust measurement on the outlet pipe of the dust bag still determines a dust content of more than 10 g / Nm³ , the furnace gas is fed into the "vortex", "cyclone" or centrifugal separator for further dedusting . The dust separated into the dust container is drawn off through a lock, made transportable by moistening and, after sintering , fed back into the blast furnace process.
literature
- Hans Schoppa: What the blast furnace operator needs to know about his work . 4th edition. Verlag Stahleisen mbH, Düsseldorf 1992, ISBN 3-514-00443-9 , p. 61-62 .
- Association of German ironworkers (ed.): Common representation of the ironworking industry . 17th edition. Stahleisen mbH, Düsseldorf 1971, ISBN 3-514-00001-8 , p. 94-95 .
- Karl Taube: Steel production compact: Basics of iron and steel metallurgy . Vieweg Technik, Braunschweig / Wiesbaden 1998, ISBN 3-528-03863-2 , p. 102 .
Web links
- Model of a dust bag at das-stahlwerk-in-z.de