6.1 Storage Tanks
6.1.1 Emissions
Introduction
Tanks are used at petroleum refineries to store raw materials, intermediate products, finished products, and wastes. There are numerous intermediate products in a refinery including liquefied petroleum gas, gasoline, kerosene, diesels, and fuel oils. The waste products include wastewater, spent acids, and oily sludge.
Categories 55-58 contain point source emissions from refineries tanks, and categories 84- 85 account for point souce emissions from tanks at other sites. Category 940 accounts for point source emissions from cleaning of all storage tanks. Category 1902 and 1903 accounts for area source emissions from storage tanks.
Storage tanks at bulk plants and gasoline stations are inventoried in sections 6.4 and 6.9, respectively.
Methodologies
The categories for storage tanks contain emissions from both point and area sources. Tank emissions are calculated using equations and emission factors from U.S. EPA’s Compilation of Air Pollutant Emisssion Factors, AP-42, Volume I: Station Point and Area Sources. The primary criteria pollutant emitted from storage tanks include hydrocarbon vapors or volatile organic compounds (VOCs).
The predominant types of storage tanks found in a refinery include:
- Fix roof tanks
- External floating roof tanks
- Internal floating roof tanks
- Conservation tanks, pressure tanks, and others
The types of tank along with the following parameters (given below) are used to calculate emissions.
- Tank diameter
- Paint factor
- Tank height
- Vapor space
- Temperature change
- Tank volume
- Throughput
- Stored material
- Factors specific to stored material
Point source emissions are obtained from the District’s data bank system. The data bank contains information submitted by the individual refinery by tank sources. Area Source emissions are derived based on an estimated ratio between area and point source throughputs via tank type.
Monthly Variation and County Distribution
The county, month, and day factors are obtained from the data bank’s information for each category.
category | ALA | CC | MAR | NAP | SF | SM | SNC | SOL | SON |
---|---|---|---|---|---|---|---|---|---|
#55 Cone Roof | 1.0% | 97.0% | – | – | – | – | – | 2.0% | – |
#56 External Floating Roof | – | 95.0% | – | – | – | – | – | 5.0% | – |
#57 Internal Floating Roof | – | 81.0% | – | – | – | – | 6.0% | 13.0% | – |
#58 Other Types | 49.5% | 50.0% | – | – | – | – | – | 0.5% | – |
#84 Cone Roof | 26.0% | 24.0% | – | – | 31.0% | 6.0% | 6.0% | 6.0% | 1.0% |
#85 Other Types | 29.6% | 21.8% | – | – | 0.3% | 2.9% | 12.1% | 32.9% | 0.3% |
#940 Tank Cleaning | – | 96.1% | – | – | – | – | – | 3.9% | – |
#1902 Cone Roof (Area) | 26.0% | 24.0% | – | – | 31.0% | 6.0% | 6.0% | 6.0% | 1.0% |
#1903 Other Types (Area) | 29.6% | 21.8% | – | – | 0.3% | 2.9% | 12.1% | 32.9% | 0.3% |
6.1.2 Trends
History
Historical emissions have varied with refinery throughputs.
Growth
category | backcast | forecast | profile |
---|---|---|---|
#55 Cone Roof | No | Yes | #788 2007 Cec Rpt (1%) |
#56 External Floating Roof | No | Yes | #789 2007 Cec Rpt (1%) |
#57 Internal Floating Roof | No | Yes | #790 2007 Cec Rpt (1%) |
#58 Other Types | No | Yes | #791 2007 Cec Rpt (1%) |
#84 Cone Roof | No | Yes | #795 2007 Cec Rpt (1%) |
#85 Other Types | No | Yes | #796 2007 Cec Rpt (1%) |
#940 Tank Cleaning | Yes | Yes | #792 2007 Cec Rpt (1%) |
#1902 Cone Roof (Area) | Yes | Yes | #795 2007 Cec Rpt (1%) |
#1903 Other Types (Area) | Yes | Yes | #796 2007 Cec Rpt (1%) |
Projected growth for all refinery related categories was taken from the California Energy Commission report on California’s Petroleum Infrastructure (2011) that predicted California refiners expand distillation capacity to remain relatively flat. This is due to increase in fuel efficiency of vehicles from CAFÉ standards as well as steady transition to alternative fuels in the California market. California refiners have recently added and will continue to add more process units to produce reformulated gasoline. However, no large increases in emissions are expected.
Control
Rule 8-5 controls emissions from the storage of organic liquids. Control efficiencies are estimated to range from 17% to 96%, depending on the type of tank, percentage of sources with true vapor pressures above 0.5 psi, and average true vapor pressure of the corresponding category. The following table show the control and rule efficiencies. (Sources with true vapor pressure greater than 0.5 psi are affected by this rule.)
FIXME: INSERT TABLE
By: Tan Dinh Date: January 2014 Base Year: 2011