Season 6 Challenges

Reward- INR 3,00,000 | Opening Date: 15 JAN 2019  |  Closing Date: 15 APR 2019   
Ferous Oxide

The by-product gases of BF and LD are burnt before releasing to the atmosphere through Chimneys (known as Flare Stacks). This consists of three chimney heads for releasing the main gas, each having 4 ignitors (along with pilot flame burners) at the top of Chimney.  The pilot flame is used for igniting these gases which are positioned at the topmost point of these flare stacks. A detection system (based on the temperature of flame) is used to detect if the pilot flame is glowing. It becomes difficult to detect the presence or absence of the flame for various reasons.

  1. The pilot flame is invisible during day time
  2. Temperature based flame detection sensors are not reliable as it is influenced by heat and ambient condition of dust & moisture
  3. Difficult to maintain as these sensors are not accessible making it further unreliable.

The igniter system consists of an igniter i.e. the spark plug, electrodes & insulators assembly at the top of the Coke Oven Gas (COG) flare stack.  The ignition system consists of ignition transformers located at the panels at the bottom. The HT output of the transformers feeds the ignitors at the top, which generate a spark when energised. This igniter fails to generate enough spark at the spark tip because of internal insulation failure/low insulation, as it is affected by heat and ambient conditions (dust & moisture).

At the start of Blast Furnace & LD Gas the CV values of the gas are lean and at times pilot Gas COG is also lean after shutdown. The CO gas used for Pilot flame also carries impurities and chokes up the Pilot line after a certain time of operation.

If loss of pilot flame is not immediately detected, it can eventually lead to loss of the main flame which is needed for flaring the by-product BF gas. Since BF gas has significant CO concentration, this cannot be released to the atmosphere without flaring which otherwise will be a potential safety threat for people working near the stack and nearby operating units of the Steel Plant.  This situation leads to an unsafe condition and may force the shutdown of Blast Furnace.

Options tried:

  1. As the original CO pipelines meant for pilot flame ignition slowly got choked up with impurities of COG, a set of the new line was laid;  Ring main system on top of Chimney with COG and another line & ring main for LPG to be used as a pilot flame. This system also failed several times because of failure of Flame sensing, igniter system not able to generate a spark and also because of the usage of lean CV during start-up. 
  2. The damaged ignitor assemblies have been replaced with new systems and are relocated closer to the new CO and LPG lines.
  3. The thermocouple cables were provided with heat insulation to prevent damage due to high ambient temperature.
  4. However, there have been failures of the ignition system within three months of operations, due to the failure of the igniters, misalignments of the pilot CO lines and failure of thermocouple based flame detection system. The maintenance of the electrical installations at the top is also very difficult due to restricted & difficult access.

The solution should provide a reliable ignition system and flame detection system for the operation of the flare system with zero maintenance at the top and all controllable features at the bottom of Chimney.

Note: The main gas which has to be ignited by the Pilot burner also has varying CV value in the beginning and the flow volume also changes as per the operating condition of the process.

Successful implementation would comprise of,

  1. A reliable flame detection system, which can send an alarm as soon as any one of the three flames is put-off and remains reliable in conditions not favourable, at the top of Flare Stack.
  2. A reliable ignition system which can ignite the flame with low or no maintenance at the top of Flare Stack with the varying CV of both Pilot COG, main gas of BFG and LDG.
  3. An emergency ignition system which can be operated from the ground to ignite the main gas at top of flare stack in-case of failure of the main ignition system 

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