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“Copyright © 2007. MECON Limited. All Rights Reserved” Chapter – 4.5 Page 1 of 4

4.5 BLAST FURNACE GAS CLEANING SYSTEM 4.5.1 Scope of work The scope of work of the Bidder under this specification covers, but not

limited to, the following :

i) Design engineering, manufacture, assembly, inspection, testing, shop painting and erection, testing & commissioning of complete BF Gas Cleaning plant as per technical specification and relevant Chapter of GTS.

ii) Demonstration of performance guarantee. iii) Supply of commissioning spares (list to be furnished by the Bidder

and to be approved by the Purchaser/Consultant). iv) Supply of spares for 2 years normal operation of the plant. A list of

such spares shall be furnished by the Bidder alongwith quantity & itemised price. The list shall be approved by the Purchaser / Consultant.

v) All the matching flanges / utility connections shall be included. vi) Supply of all consumables, initial fill of oils, lubrication and other

consumables. 4.5.2 Data / Drawings to be Furnished Alongwith Tender

i) Overall layout drawing of complete Gas Cleaning Plants showing major dimensions & clearances

ii) General arrangement and cross-sectional drawings of GCP

indicating the location various systems, equipments, auxiliaries, piping, etc.

iii) GA drawings of major equipments. iv) List of pumps, drives alongwith specification and Kw rating. v) Data sheets / catalogues for various equipment, valves and bought

out items. vi) Process flow sheets and schematic diagrams of various utilities

indicating flow rates, pressures, temperatures, consumption’s, etc.

vii) Schematic diagrams for hydraulic /pneumatic / lubrication systems

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“Copyright © 2007. MECON Limited. All Rights Reserved” Chapter – 4.5 Page 2 of 4

viii) Equipment schedule indicating quantity, estimated weights and source of supply (Indigenous / Imported)

ix) Detailed write-up on features provided for process & safety

interlocks including functional diagrams

4.5.3 The data/ drawings to be furnished by successful Bidder for Purchaser/ Consultant’s approval i) Write-up on ‘Control philosophy’ for smooth operation of gas

cleaning plant. ii) GA & Cross Sections drgs of GCP with binding dimensions. iii) Equipment GA drawings showing details and Sections alongwith

technical data sheet, bill of material. iv) Structural drawing showing platforms with approach ladders at

various levels of GCP tower for maintenance of different equipment.

v) Utility / services requirement and terminal point where such utilities

/ services are required. 4.5.4 Technical Specification 4.5.4.1 Description of the unit

The dust laden gas from dust catcher enters the gas cleaning plant based on the principle of two stage wet gas cleaning housed in a single tower and designed for the following parameters. i) Medium to be handled : Blast furnace gas ii) C.V. of gas : 875 kcal/ Nm³

iii) Expected analysis of : CO2 - 24.3 % B.F. Gas (by volume) CO - 26.1 % H2 - 3.1 % N2 - 46.5 %

iv) Type : Two – stage system with

Annular gap scrubber

v) No. of units : One

vi) Volume of BF gas : 5,40,000 Nm³ /hr (Normal) 5,90,000 Nm³ /hr (Max)

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vii) Temp. of the gas : 150 – 200°C 600°C (Peak Temp. for 30 min.)

viii) Pressure of the gas : 2.3 – 2.5 kg/cm² (g) at inlet ix) Dust content of the : 17 .0 gms/ Nm³ (max) inlet gas to GCP 8.0 gms/ Nm³ (normal)

x) Moisture content of inlet : 70 gm/ Nm³.

Gas of GCP

xi) Outlet pressure of the gas : 2.0 – 2.3 kg/cm² (g) (when TRT is in operation) 1000 mmWC (when TRT is not in operation) xii) Dust content of the gas : 5 mg/Nm³ (max)

at the outlet xiii) Outlet temp.of the gas : 40 deg.C

The hot dust laden gas from the dust catcher enters the 1st stage of the GCP tower from the top located above the annular gap cone scrubber, and cooled to saturation temperature by direct contact with water in a hollow scrubber where the gas stream enters the spraying zone of the scrubber and passes through the water curtain emitted by the injecting nozzles (BISCHOFF TYPE TOWER) arranged to give an upward and downward sprays into the downward flowing gas. Pumped water from the cone base and returned clarified water will be used for spraying. There shall be provision of emergency water supply to the upper stage of the scrubber in case of power failure. In the 1st stage, besides saturation, coarse dust particles are also entrapped into the water droplets. The slurry water from the 1st stage will be directed to the existing over ground launder for discharging into the existing effluent treatment plant. The greater part of the free water in the gas will be separated into the tower sump as the gas leaves the 1st stage of the tower.

Part of the pre-cleaned gas coming out after the 1st stage cleaning can be used for pressure equalizing of the BF top equipment. The saturated, cooled pre-cleaned gas from the 1st stage now enters the 2nd stage cleaning equipment housed in the same tower (along with 1st stage equipment). The 2nd stage gas cleaning equipment comprises of annular gap scrubber (BISCHOFF TYPE), where the gas flows through the annular gap passage. Radial and tangential sprays will supply the clarified water necessary for the removal of dust particles. Normally 3 nos. of single annular gap elements are provided. Each of the three elements

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“Copyright © 2007. MECON Limited. All Rights Reserved” Chapter – 4.5 Page 4 of 4

will comprise a fixed cone within which a hydraulically operated inner cone operates. The differential pressure necessary for gas cleaning and top pressure will be regulated by raising or lowering the movable cones to vary the annular gaps. Sufficient power shall be provided to move to the cone 100% in either diversiform in emergency. 1st stage as well as 2nd stage of GCP tower shall be provided with sump water level control system to maintain BF operation as will prevent gas escape. GCP shall be suitable for Blast furnace operation with coal injection and hence appropriate corrosion protection necessary will be applied to meet the acidic re-circulating water found with the use of coal injection. The clean gas, coming out of the 2nd stage scrubber, passes through water droplet separator (demister), wherein water droplets get separated out from the gas stream. The gas entering the demister, passes through fixed directional vanes inducing a spinning action in the gas stream. Free moisture is collected as a result of the centrifugal forces produced by the spinning action.

Slurry water is collected at the bottom of the 2nd stage scrubber and also at the bottom of the droplet separator. The slurry water is then directed to over ground launder for discharging into the effluent treatment plant. Clarified water from the effluent treatment plant will be pumped back to GCP 1st stage and 2nd stage scrubber. The clean gas with dust content of 5 mg/ Nm³ from the moisture separator will be used to meet the fuel requirements of various consumers of the steel plant. The clean gas line will also be provided with suitable facilities for connection to TRT for power generation. When TRT is in operation the pressure drop across the scrubber will only be that necessary to achieve the required gas cleanliness. The remaining pressure reductions to a pressure suitable for distribution within the works shall be performed by .the TRT. The scrubber and TRT shall be interlocked to insure accurate control of the furnace top. In case TRT is out of operation the scrubber will reduce the outlet gas pressure to the pressure in the clean gas system. The GCP will be complete with all the necessary instrumentation and controls, electrics, service platforms and supporting structures, stairs / ladders for easy approach to various instruments / valves / equipment, handling facilities as required, etc. for easy operation and maintenance.