DESCRIPTION OF GAS CLEANING PLANT

The dust-laden blast furnace gases after dust catcher are cleaned in the gas Cleaning Plant. The unit is of latest design consisting of two-stage High Energy ventury Scrubber system. The first stage ventury provides precleaning and cooling of BF gases. The second stage ventury provides final cleaning of the BF gases. The system is highly efficient and yields cleaned BF Gas.

In the first stage, hot dust laden gases are cooled to below saturation temperature in variable throat ventury scrubber. Coarse dust particles are removed in the scrubber removing 90 – 95% of the dust from the gases. Water is supplied to the scrubber through recirculation (clean) water pumps from Clarifier plant. Two pumps, one working and one standby, are provided for this purpose. Dust laden water is discharged through water sealing system to the launder for treatment and recycling by PURCHASER.

The precleaned gases leaving after first stage ventury passes into the second stage of gas cleaning plant which comprises a high energy ventury scrubber of adjustable flaps. In the venturi throat, the gas moves against the water spray which forms fine lamellae filters for separation of fine dust particles.

The venturi throat is equipped with mechanism to adjust the throat area, which allows optimum adaption to the gas volume generated in the blast furnace. Differential pressure across the GCP controls second stage venturi throat opening automatically.

The gas leaving the second stage venturi enters the moisture separator where the finest water droplets are flung against the scrubber shell and run down into the sump, and gas gets free from water particles leaving the gas cleaning plant for distribution through pipeline network to various applications.

Gas cleaning system is designed for minimum water consumption to achieve desired cleaning efficiency as well as temperature at outlet of GCP. Corresponding slurry volume generated and discharged for treatment is also minimum.

The gas cleaning plant is provided with service platforms and supporting structures, as required.

There is good access from outside to all vital parts. The space requirement is kept minimum.

WORKING PRINCIPLE

Flue Gas from Blast Furnace of quality ranging from 74,000 Nm3/hr/max and pressure of 8000 mm WG Normal will enter into the dust catcher, and then first stage, wet approach venturi scrubber from the top centre while scrubbing liquid is introduced from the wall, through open pipe. The gas and scrubbing liquid are thoroughly mixed in the ventury throat. The ventury throat is electrically actuated. The gas with entrained solids and liquids are passed through centrifugal separator after second stage venturi where scrubbing liquid and collected solids flow down to the water seal and clean gas exist through the side top gas outlet.

OUTSTANDING FEATURES :

Simple trouble free design
There are no special nozzles or distribution jets in which solids can collect, thereafter, slurries of any solids capable of being pumped can be handled.

No wet / dry build up.
Scrubbing liquid introduced through open pipe on the internal surface of the convergent section, swirls down in flow pattern that assures through wetting of surface

Adjustable Throat.
For system with anticipated wide variations in gas flow, Ventury Scrubber with adjustable throat is recommended. This design consists of two side plates mounted on parallel shaft located on each, at the long side of the entrance to rectangular throat. Throat area can be decreased by shaft rotation so that the blade edges move from the sidewall, towards central line of the throat.

Constant Pressure drop
In order to maintain constant pressure drop across the Venturi, a constant throat gas velocity is maintained, thus throat must widen with increased gas volume and reduce in width with decreased volume. This is accomplished by moving blades supplied for automatic operation.

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