17-12-2012, 02:27 PM
GAS CLEANING PLANT (GCP) & TILT DRIVE SYSTEM OF VESSEL
1GAS CLEANING PLANT.docx (Size: 8.56 MB / Downloads: 240)
ABOUT TATA STEEL
Tata Steel is on the threshold of its centenary celebrations.
In 2007 it will commemorate 100 long years of existence. . It has stood the test of time as a
Robust, young Company because it has constantly anticipated the requirements of the market and upgraded its technology and introduced several innovative practices that have made it an agile and a seamless company. It continues to bear fruition to the vision of its Founder, Jamsetji Nusserwanji Tata with a business paradigm that wholeheartedly integrates social responsibility into it. Tata Steel is an enterprise with a mandate beyond profit making. It believes in wealth creation and improving the quality of life for its people. In the early eighties, the Company had embarked on a four phased programme of modernization for the entire steel plant. Completed in 2000, at a cost of over Rs 60000 million, this programme had transformed the company into a world class steel plant. In the past few years, Tata Steel has also commissioned and completed its 1.2 million tonne capacity Cold Rolling Mill complex and is now fully integrated into the competitive market with highly stringent demands with a sophisticated range of products including hot rolled, cold rolled and coated strips from its CRM complex.
GAS CLEANING PLANT (GCP)
Steel is made in LD converters by lancing pure oxygen, which converts the carbon present in the pig iron into carbon mono-oxide (CO). Oxygen is blow through the lances into the converter charged with hot metal, iron scrap, ferroalloys, lime and iron ore. Iron ore is used as a coolant, which adjusts hot metal scrap ratio to large extent. High purity oxygen blown into the furnace removes carbon and silicon in the molten iron mainly by oxidation. The basic oxide furnace is feed with flux to remove the siliceous impurities. Certain alloying material may also be added to enhance the characteristics of the steel. During oxygen blowing process, a large amount of fumes and gases are generated, which contains fine particles of the charged materials and carbon mono-oxide (CO) gas.
It is necessary to clean the Gas before it is sent to compressor & Gas turbine, otherwise it may damage the turbine & compressor blades. For this purpose a Gas Cleaning Plant in included in the system.
The Gas cleaning plant is that section of the gas handling system from the outlet of the water cooled membrane hood section through to the tip of the Flare Stack The function of the Gas Cleaning Plant is to cool the gas from approximately 1200OC to 60OC, to clean the gas, and to deliver it to the Flare Stack for combustion before exhaust to atmosphere or for gas recovery system (Annexure 1.1).
Primary Separating Elbow:-
The purpose of the 90OC separating elbow is to collect the bulk of the slurry from the Primary Venturi Scrubber.
This is achieved by reducing the gas velocity in the elbow, by increasing the cross sectional area in the direction of flow and by the use of internal guide vanes which channel the slurry into a total of six drain branches which are located on each side and at the bottom of the elbow.
The drain branches convey the slurry to the Primary Seal Tank. A water spray is provided to flush the elbow during a period after the end of the blow (duct washing) to prevent dust build-up and to assist in slurry removal.
Primary Seal Tank:-
This tank receives all the effluent from the Primary Separating Elbow and discharges via an internal overflow channel and drain pipe to a Launder and thence to the Effluent Treatment Plant. The Tank is fitted with a Bottom Deflector Cone and two Agitators Sprays to keep solid particles in suspension. This Tank also receives cooling water
discharged from the Pressure Relief Door Seal at the top of the Radiation Section of the Hood. The Tank has a sealed top to prevent the ingress of air or the escape of CO rich gases but a ventilation pipe is fitted which extends to the outside of the building.
Fan Discharge Duct and Flare Stack: -
The Fan Discharge ducting comprises a 40° bend at the Fan Outlet and a swept bend which joins to the Flare Stack Inlet. The Flare Stack extends to a height of 79m. Gas flow is being measured through Venturi and diff. pressure transmitter, maximum gas flow rate is 250000 Nm3 / Hr. In the Stack, there is also pressure and temperature measurement and gas sampling for analysis; of O2.' CO: and CO2, if the oxygen level in the gas goes above 3% then an alarm is triggered.
The Flare Stack Tip is fitted with three Pilot/Igniters equidistant around its periphery.
A drain pipe at the bottom of the Flare Stack drains any condensate to the ID Fan Sump. The Venturi Meter is purged (back flushed) for approximately 2 seconds at the end of each blow with Instrument Nitrogen.
Secondary Cleaning: -
Clarified water is pumped to the plant through line. A small amount of the water is used to provide agitation in the ID Fan sump but, during a blow, the remainder is used in the Secondary Venturi Scrubber Sprays and for Secondary Venturi Damper Blade Washing. The water then drains via the Secondary Separating Elbow to the ID Fan Sump (the Hood Skirt Seal Overflow Water and condensate from the Flare Stack also drains to the ID Fan Sump).