TANK FARM
Unit Feed:
Unit Rundown:
- Crude Complex Rundown
- FCC Complex Rundown
- CCR Complex Rundown
- Alkylation Complex Rundown
Rundown Summary
Gasoline Blending:
Product Distribution:
- Truck Loading
- Pipelines
- Rail Car Loading
- Marine Terminal
Other Pumping Responsibilities:
- Tank Sampling
- Sour Water
- Administrative Duties
- Maintenance Duties
Pumping Overview
The general process flow through the tank farm can be diagrammed as follows:
The primary responsibilities are:
- Unit Feed
- Unit Rundown
- Gasoline Blending
- Product Distribution.
Other responsibilities in the tank farm involve product sampling, water treatment, surface water control, and care of equipment. Equipment care includes oiling pumps, correcting leaks, and generally ensuring that everything is in good working order.
Unit Feeds:
Operation of the Refinery's process units depends upon the ability to supply feedstock to those units. For the most part, those Feedstocks are stored in the tank farm. These process unit inputs are:
- Crude Oil
- Gas Oil
- Sour Naphtha
- Sweet Naphtha
- HDS Fractionator Bottoms
- Isobutane
- Light Cycle Oil (LCO)
- High Sulfur Diesel (HSD)
- Normal Butane
- Olefins
Crude oil:
Feedstock comes from several sources, depending upon the product. The most important of these is crude oil. Crude is supplied via the Capline pipeline, from Louisiana to a Valero storage facility near Collierville, TN, which in turn pumps it via pipeline to the Refinery's storage tanks.
The Refinery currently has three crude storage tanks, 73, 74, and 75, offering the option of storing more than one type of crude. Although all three tanks are used as the primary feed tanks, the piping and pump arrangement allows some flexibility as to which crude tank is being sent to the Crude Units.
The quantity of crude can be varied, as well as the mixture, if more than one type of crude is being used. There is also the option of feeding different blends of crude to the two crude units.
Gas oil:
The other unit feedstock comes from other units, either directly or from a holding tank in the field. Gas oil is used as feed to the FCC Unit. Some of that gas oil comes directly from the Crude Unit, while the remainder is fed from storage in 67 and 68 tanks. There are two feed pumps, which can be lined up singly or in tandem.
Sour naphtha:
The Naphtha Hydrogen Desulfurization Unit is fed from 001 tank. 001 contains sour naphtha, which is a mixture of heavy straight run gasoline and crude column overhead. Two pumps are used to feed sour naphtha to the NHDS Unit.
NHDS Fractionator bottoms:
During NHDS Unit startup, a sweet feed is required. NHDS Fractionator bottoms are used for this purpose. Fractionator bottoms are stored in 43 tank, and when needed, are fed to the unit by a single pump.
Isobutane:
Isobutane is used as feed to the Alkylation Unit. Iso is pumped from storage in the LPG tank farm, using one or both feed pumps.
Light cycle oil:
Light cycle oil is normally fed directly to DHT 18 and DHT 13. When either of the DHT’s are down, the LCO is sent to storage in 82 tank. It is then pumped back to DHT 18 or DHT13 when the unit comes back on stream.
High Sulfur Diesel
High sulfur diesel is shipped to the refinery by barge and stored in 85 tank. The high sulfur diesel is unit feed for DHT 13 and DHT 18.
Normal butane:
Normal butane is pumped to the CCR or FCC Unit to boost gasoline vapor pressure. Butane in storage is received from the Alkylation Unit, the Sat Gas Plant, or from outside the Refinery by rail car or truck.
Olefins:
Olefins are used as C3/C4 splitter charge. Olefins are received from the FCC Gas Con Unit.
Unit Rundown:
Certain tanks in the field are set aside to receive and store products produced on the process units. The collection of unit rundown is essentially a passive operation, but requires constant monitoring to prevent overfilling a tank and to ensure that the product is going to the right storage tank. Once in the tank, the rundown product is held in storage, shipped to customers, used as blendstock, or pumped back to another process unit as feed.
Most rundown products have designated storage tanks. For some products, specifically gasoline blending components, the rundown stream can be redirected to other tanks to facilitate the blending process.
The rundown streams you are responsible for are:
- Alkylate
- Blended Fuel Oil
- FCC Gasoline
- Gas Oil
- HDS Fractionator Bottoms
- High-Sulfur Diesel
- Low-Sulfur Diesel
- Isobutane
- Isomerate / Naphtha Stabilizer Bottoms
- Kerosene
- Light Cycle Oil
- Main Column Bottoms
- Normal Butane
- Olefin (Propane/Propylene And Butane/Butylene)
- Platformate
- Poly Gasoline
- Propane
- Sat Gasoline
- Sour Naphtha
- Spent Caustic
Crude Complex Rundown:
The Crude Unit Complex feeds eight rundown products to storage: Sats gasoline, kerosene, sour naphtha, gas oil, propane, normal butane, isobutane, and high sulfur diesel.
Sat gasoline:
Sat gasoline is a gasoline blend component produced at the Sat Gas Plant. The sat gas stream runs down to 46 and 47 tanks, where it can be fed to the gasoline inline blender.
Kerosene:
Kerosene is a light distillate off of the West Crude Unit kerosene Fractionator. Before running down to storage, west kerosene goes through the Merox and Merichem treaters to remove sulfur compounds. The sweetened product is then used either as Jet A commercial jet aviation fuel, JP-8 military jet fuel, or 1-K grade heater/lamp fuel.
To qualify as Jet A fuel, the kerosene may contain no more than 0.003% mercaptan sulfur or 0.3% total sulfur. Because 1-K kerosene is used in open heaters and lanterns, it must pass a burn test and may contain no more than 0.04% total sulfur. Because of these and other differences, Jet A, JP-8, and 1-K are stored separately. The pumper will be notified when specifications change, necessitating a change in the kerosene rundown lineup. Tanks 51, 52, 56, 101, 102, and 115 may be used for kerosene rundown and storage.
Sour naphtha:
Sour naphtha is a combination of crude column overhead and heavy straight run gasoline from the east and west units. These untreated light distillates are sent to 001 tank for storage as charge to the Naphtha HDS Unit.
Gas oil:
Gas oil is a residual fraction off of the east and west crude columns and is used as charge to the FCC Unit. A portion of the rundown stream is fed directly to the FCC, and the remainder goes to storage in the tank farm. Tank 67 is the designated FCC charge tank, although 66 and 68 tanks can be used as a backup storage tank if 67 tank fills up. Because of its low API gravity, gas oil must be stored at high temperature (about 150 - 160) to keep it fluid enough to pump.
Propane:
Propane is the overhead off of the Sat Gas depropanizer tower. The propane goes to the common propane rundown line to storage in the LPG tank farm. The propane is then available for sale to customers as HD-5 or commercial grade propane.
Normal butane:
Normal butane is the bottoms product off of the deisobutanizer (DIB) tower in the Sat Gas plant. Normal goes to storage in the LPG tank farm, from where it is used to pump to the FCC and CCR units and to the gasoline blender. It is used to control gasoline vapor pressure.
Isobutane
Isobutane is the overhead off of the deisobutanizer tower. It goes to storage in the LPG tank farm to be used as feed to the Alkylation Unit.
Spent caustic
Spent caustic from the kerosene Merox and Merichem treaters is sent to storage in the tank farm, although it is not technically a unit rundown. The spent caustic goes to 604 tank.
FCC Complex Rundown
The Fluid Catalytic Cracking Unit feeds the products of reaction and fractionation to storage. Following fractionation, FCC products undergo varying degrees of stabilization, treatment, and additional reactions before going on to storage. FCC rundowns include products from the Gas Con and Polymerization units. (if the poly unit is in service)
Olefins:
Olefins are unsaturated leftovers from the Gas Con unit in the FCC. They are sent to storage in the LPG tank farm to be used as charge to the C3/C4 splitter at the Alkylation Unit
FCC gasoline:
FCC gasoline is a stabilized and treated product off the bottom of the Gas Con debutanizer. Debutanizer bottoms (DBB) goes to the FCC Gasoline Merox Treater, where it is sweetened before being fed to storage. FCC gasoline is then used as blendstock to the inline gasoline blender. FCC gasoline is normally stored in tank 72. Piping alignment can be changed to feed FCC gasoline to 16, 60, or 81 tanks.
Light cycle oil:
Light cycle oil is a side cut off of the FCC main column that normally goes directly to DHT 18 and DHT 13. When the DHT is down, LCO goes to storage in 82 tank. LCO is pumped to the DHT for blending into blended fuel oil.
Main column bottoms:
Main column bottoms, or slurry bottoms, is a residual product from the FCC main column. Once transferred to storage, MCB is sold as No. 6 fuel oil. MCB is even heavier than gas oil, so it also must be stored at high temperature. MCB is normally stored in 66 or 65 tanks, and may also be fed to 15001, 15002 tanks for truck loading.
Spent caustic:
Spent caustic is left over after being used to sweeten FCC gasoline and LPGs. Spent caustic is not technically a unit rundown stream. Caustic is, however, sent to storage after it is used in the FCC gasoline Merox Treater and the FCC LPG Merox Treater. Spent caustic from the FCC gasoline Merox Treater is sold to chemical companies, which extract cresylic acid for use in manufacturing. The FCC LPG Merox spent caustic is not suitable for this purpose, so the two spent caustic streams must be segregated in separate storage tanks. LPG spent caustic is stored in 44 tank. FCC gasoline spent caustic is sent to 44 tank.
CCR Complex Rundown
Platformate, HDS Fractionator bottoms, and Isomerate all run down from the CCR Complex.
Platformate:
Platformate is the product (gasoline blending component) of reacting a desulfurized / sweet naphtha feed in the presence of a catalyst. This reaction creates a high-octane blendstock for unleaded gasoline.
NHDS Fractionator bottoms:
Naphtha feedstock to the CCR Unit must be treated to remove sulfur compounds that would quickly deactivate the reforming catalyst. The process of naphtha Desulfurization results in small amounts of a residual gasoline called HDS Fractionator bottoms. Fractionator bottoms normally go to the CCR, but the rundown stream can be diverted to the tank farm for storage. A tank full of HDS Fractionator bottoms is kept in reserve to serve as "sweet feed" for CCR Unit startup. Pumps and piping are also available to blend Fractionator bottoms into gasoline.
Isomerate:
Isomerate is the product of additional catalytic reforming. The naphtha Desulfurization process leaves C5's and C6's that aren't used in the CCR. These light gases go to the Isomerization Unit, where they are isomerized (reformed) into a light gasoline. Rundown from the Isom Unit goes to storage in the tank farm, where it can be blended into motor gasoline.
Alkylation Complex Rundown:
The Alkylation Unit feeds Alkylate, normal butane, propane, and propane/propylene (P/P) mixture to storage in the tank farm.
Alkylate:
Alkylate is a high-octane gasoline component used for blending into motor gasoline. Olefin and isobutane combined feed react in the presence of hydrofluoric acid catalyst. Alky feed eventually goes to the iso Fractionator column where it undergoes fractionation. The bottoms off of the iso Fractionator goes to storage in the tank farm as Alkylate.
Normal butane:
Normal butane also comes off of the iso Fractionator column. The normal rundown stream goes to storage in the LPG tank farm. From there it can be pumped to the units, truck loading, or to the inline blender to raise gasoline vapor pressure.
Propane:
Propane results from additional processing at the Alkylation Unit. The overhead from the iso Fractionator column goes to a depropanizer. The overhead from the depropanizer is stripped and treated for the removal of HF acid, then goes on to storage as alky propane. From storage, propane is sold directly to customers.
Propane/Propylene (P/P):
Propane/propylene mixture is a product off of the C3/C4 splitter. It is sold to customers in the petrochemical industry.
Rundown Summary
Alkylate, FCC gasoline, Isomerate, poly gasoline, Platformate, and sat gasoline are fed to storage for the sole purpose of serving as blendstock for the gasoline inline blender. Most of the time, FCC gasoline and poly gasoline are fed to the same rundown tank, although, if necessary, they can be separated and fed to different tanks.
Gas oil, HDS Fractionator bottoms, isobutane, light cycle oil, normal butane, and sour naphtha are collected for use as feed to other units. Gas oil is an output of the crude unit and is used as feed to the FCC Unit. Isobutane runs down from the FCC depropanizer to be used as feed to the Alkylation Unit. As explained above, LCO goes to storage only when the Distillate Hydrotreater is down. Normal butane runs down from the Alkylation Unit and is used to raise gasoline vapor pressure. From its storage tank, normal is pumped to the CCR or FCC Unit, or it can be pumped directly to the gasoline inline blender. HDS Fractionator bottoms and sour naphtha are used as Naphtha HDS Unit feed. Sour naphtha is used during normal unit operating conditions. HDS Fractionator bottoms is reserved for unit startup, when a sweetened feed is needed.
The remaining products, blended fuel oil, kerosene, main column bottoms, and propane are sold directly to customers. Blended fuel oil is a mixture of diesel, kerosene, and light cycle oil, and is sold as No. 2 fuel oil. LCO from the FCC Unit, and kerosene and diesel from the Crude Unit are treated and blended at the Distillate Hydrotreater before being transferred to storage. Kerosene from the Crude Unit is sold as JP-8 military jet fuel, Jet A commercial aviation fuel, or as 1-K kerosene. Main column bottoms from the FCC Unit is collected for sale as No. 6 fuel oil. Propane is sold as a heating fuel.
Spent caustic is left over after being used to sweeten kerosene, FCC gasoline, and LPGs. Spent caustic is not technically a unit rundown stream. Caustic is, however, sent to storage after it is used in the kerosene Merichem Treater, the kerosene Merox Treater, the FCC gasoline Merox Treater, and FCC LPG Merox Treater. Spent caustic from kerosene treaters and the FCC gasoline Merox Treater is sold to chemical companies, which extract cresylic acid for use in manufacturing. The FCC LPG Merox is not suitable for this purpose, so the spent caustic streams from the various units must be segregated in separate storage tanks. LPG spent caustic is stored in 44 tank. FCC gasoline spent caustic is sent to 44 tank. Spent caustic from the kerosene treaters goes to 604 tank.
Gasoline Blending:
There are two aspects to gasoline blending: Preparing the feed tanks to the inline blender and lining up a receiving tank for storage and distribution of the finished product.
No. 1 end:
As described in the section on unit rundown, some unit outputs are used only as blendstock for the inline gasoline blender. The tanks used to receive unit rundown are used also as blender feed tanks. Although the Blending Chemist controls the blending process, the No. 1 Pumper ensures that the tanks, pumps, and pipelines are properly lined up to deliver the blendstock to the blender header.
The actual products used depend upon the octane needed for the finished product. There is some flexibility in which tanks are used for blendstock storage, but routine tank designations are as follows:
16 tank Platformate, FCC/Poly gasoline, or Isomerate
46 tank Sat gas, or Alkylate
47 tank Sat gas, or Isomerate
60 tank Platformate
72 tank FCC/Poly gasoline
81 tank Platformate or FCC/Poly gasoline
73, 74, 75 tanks Crude Oil
84 tank Blend Component
45 tank Benzene Stripper
48 tank Sour Water Stripper
125001 tank Naptha
15001, 15002, 65, 66 tanks #6 Oil
67, 68 tanks Gas Oil
85 tank High sulfur diesel.
No. 2 end:
At the other end of the process, the No. 2 Pumper ensures that blended gasoline is directed to the right tank for storage and distribution. Tank designations change from time to time depending upon market needs and refinery storage requirements. Both the octane rating and vapor pressure may be changed to satisfy the market or to comply with environmental regulations. The following tanks are currently used for gasoline storage:
- 58 tank 93 octane unleaded gasoline
- 59 tank 87 octane unleaded gasoline
- 71 tank 87 octane unleaded gasoline
- 76 tank 87 octane unleaded gasoline
- 002 tank 87 octane unleaded gasoline
- 53 tank 93 octane unleaded gasoline
- 54 tank 93 octane unleaded gasoline
- 80 tank Ethanol
Each gasoline tank is equipped with pumps and piping to deliver it to bottom loading for tank truck loading or to the river dock for barge shipment. Gasoline storage tanks may also be used to receive barge shipments. The capability also exists to transfer product from one storage tank to another.