2. Revamping of Desulphurisation

3. Coke Oven - Introduction
A coke oven is a device used to produce coke, a product that is
derived from coal. The heating of coking coal at temperatures
ranging from around 1000° to 1200°C within the airless oven
yields the coke and by-products.

4. The raw coke oven gas after getting out of battery through
Gas collecting main is contaminated with various impurities
like Ammonia (NH3 ), Hydrogen sulphide (H2S), Tar, Benzol,
Napthalene etc.
The purpose of the DS unit is to eradicate the H2S from
the coke oven gas after tar has been removed from it.
Coke Oven Gas

5. DesulphurizationSection
Legend
COG line
Solution line

6. Sulphur values in CO gas
Gas coming from the Coal Blast Section = 3-4 gm/Nm3
As per design, Sulphur in CO gas after DS unit = 0.5 gm/Nm3
Sulphur value in CO gas after the revamping of DS unit = 0.1 gm/Nm3
Before revamping, Sulphur in CO gas after DS unit = 0.4 – 1.1 gm/Nm3

7. Problems in Desulphurisation Plant
S.No Criteria Description
1 WHAT is the problem? High sulphur value in COG
2 WHEN does the problem occur? When both towers are not operating efficiently.
3 WHO is affected? HSM
4 WHERE does the problem occur? Scrubber tower -1, scrubbing section.
5 HOW does the problem affect? Defects on rolled coils.

8. Problems in DS section
Serial Number Problem Description
1 Solution leakage into pre-cooling solution
2 Tower temperature not maintained properly.
3 Solution volume increase.
4 Absence of regulating valve in solution line of regenerating tower .
5 Steam coil leakage in circulating tank.
6 Leakage in Emergency Solution tank.

9. Pareto Analysis
Problem Description Problem Serial No.
No. of times
attended by
operations
Solution leakage into lower part of scrubber tower 01 81
Tower temperature not maintained properly. 02 52
Solution volume increase. 03 17
Absence of regulating valve in solution line of
regenerating tower –
04 8
Steam coil leakage in circulating tank. 05 5
Leakage in Emergency Solution tank 06 3

10. Pareto Analysis

11. Cause-Effect Diagram

12. Principle Cause of the Problem
Major Cause –
‘The design of the
covers on the vertical
tubes for passage of CO
gas from the Pre-Cooling
section to the scrubber
section. ’
Solution leakage took
place from the space
between the cover and
the pipes

14. Final accepted Idea
Finally the idea of changing the design of the cover was accepted because:
 It offered least resistance.
Required lesser man-hour to do the modification.

15. Cause-Effect Diagram

17. Final accepted Idea
Finally the idea of insulating tower was accepted because:
 This will protect the material of construction.
Requires least change in the working parameters.

18. Serial
No.
Category Before After
1 COG to Propane gas ratio 60:40 90:10
2 No. of flaring per month 7,50,000 23,000
3 Grades that used COG
4 Furnace cleaning per month 15 to 17 times 2 to 3 times
5 No of times each burner cleaned per month 28 to 31 times 5 to 7 times
6 Choking of Burner per month 10 to 15 times 1 to 3 times
7 Propane Used by HSM per month 48,00,000 Nm3 2,50,000 Nm3
Changes: before and after revamping

19. Advantages
The main advantages of the modifications are :
Less environmental impact as the gas has low sulfur content.
Less defects in HSM, which earlier occurred due to presence of sulfur.
Increased consumption of COG by our customers as the better quality gas
can be used for heating those grades which earlier used propane gas.
Increase in service life of MS gas pipelines in COG plant and consumer end.