The main plants in utilities are : 1. Raw water systems
2. De mineralised plant 3. Power plants I &II 4. Captive power plant 5. Cryogenic nitrogen unit 6. Flare system
1. Raw water systems
Raw water is received from Tatipudi, Raiwada and Mindi reservoirs. There are high lift pump house and low lift pump house for sourcing sea water for cooling process streams and fire fighting systems.
There are cooling water towers to provide cooling water to cool equipments. Drinking water plants to satisfy drinking water demand in refinery.
The water system from Yarada bore well was used but stopped later on due to the contamination of ground water system.
There are 3 types of water systems:
a. Raw water system
Water from Tatipudi and Mindi is sent to the de mineralised plant and power plant I depending on the equitability of water. If the pump is tripped or failed,
alternative sources are used and maintenance is done.
b. Service water system
It was installed during the time of VREP I and VREP II. From PP I service water is sent to VR and VREP II and then sent to CDU I, CDU III, FCCU, flairs and desalters. From VREP I service water is sent to desalter CDU II and BBU.
c. Drinking water
The drinking water consists of PSF and activated carbon filters. Filtered water is
chemically dosed and stored in drinking water sump. In sump NaOCl is added to kill bacteria and free residual chlorine is maintained.
2. Demineralised plant Equipment
:Sand filter, Strong acid cation , Weak base anion, Strong base anion, Degasser , Mixed bed.
Process:
Raw water is processed in ion exchangers to get demineralised water. The latest technology used in VRCFP for demineralising water is reverse osmosis. Morpholine is used to maintain pH of water.
Unit process flow description
1. Alum dosing tank
There is a mixer and level gauge, depending on how raw water is analysed percentage of aluminium dosage is prepared and used. Suction line is provided with strainer.
2. Alum dosing pump
Flow adjustment depends on raw water turbidity. For light particles dosing is not enough so poly electrolyte is added. In laboratory alum dosing quantity is
determined to have better filtration in PSF.
3. Sodium sulphite dosing tank
Mixer and level gauge, suction line are provided with strainer.
4. Sodium sulphite dosing tanks
Delivery line is connected to PSF inlet.
5. PSF [pressure sand filters]
To measure the differential pressure a DP indicator is used. In PSF mechanical filtration of coagulated raw water is achieved and turbidity is reduced. Non ionic
and suspended impurities like dirt, salt and mud is removed.
6. SAC [strong acid cation]
There are 2 co-flow operation pipes and 1 counter current regeneration. After 10 cycles or when DP is greater than 0.8kg/sq cm it is back washed.Ca2+, Mg2+,Na+ are removed by exchange of H+ ions in the resins and convert into acids. It is then passed through degassed tower.
7. Degassed tower
The water devoid of cations is passed to degasser air blower.
8. Degasser air blower
Low pressure and high velocity is maintained here. Degasser water is sent from top to bottom of the blower while the air from bottom to top. When H2CO3comes in contact with O2and splits as water and CO2which blows out of the vent hole.
Residual free CO2is maintained in degasser storage tank.
9. Degasser water storage tank
It is an inlet to air blower and outlet to water pumps degasser.
10. Degasser water pumps
There are 3 service pumps and 1 standby pump. The degassed water is transferred to WBA/SBA for further ion exchange. A part of water is sent to SAC for
regeneration.
11. WBA [weak base anion]
There are 2 pipes in service and 1 in standby for regeneration. It exchanges load such as Cl, NO3, SO4from degassed water. Outlet is checked by conductivity test.
12. SBA [strong base anion]
Weak acids such as leakages from degasser, traces of chlorides and silica is exchanged to OH form. It is then sent to MB polisher units.
13. Mixed bed
Anion and cation resins are in mixed form. Due to differences in specific gravity both cation and anion resins are separated in back wash. First anion resin is regenerated and then the cation resin. Both resins are then mixed with mixed bed blower and anions are trapped in resins. It is then stored in DM storage tank.
14. DM storage tank
The demineralised water is stored here and sent to various units of the plant like Deaerator, DHDS, CPP etc.
15. Acid day tank
It is used for regeneration of resins.
16. Alkali day tank
It is used for regeneration of resins.
Plant capacities
Design capacity : DM I : 75 M3/Hr DM I : 120 M3/Hr DM I : 180 M3/Hr
3. Power plants Equipment
:Deaerator , Economiser , Bank tubes , Super heater , CO chamber.
Process :
DM water is processed to generate VHP , MP, HP steam in boilers.
Steam is also generated from the heat conservation of CO. Power plants are mainly used for steam generation and power generation. Steam is also generated from the flue gas from the gas turbine gas generators. PP I consists of WIL- 8 , BHPV, NCO , IBH-9, IBH-10 boiler . PP II consists of WIL–B , CO, BOP boilers. Water from DM
plant is sent to Deaerator where dissolved oxygen present is water is removed by HP steam and then sent to boilers in PP I & PP II.
PP I generates HP, LP, MP steam for CDUs, Desalter, FD fans for boilers.
PP II generates HP, MP steam for deaerators , oil burners and heating systems.