Technology, Maintenance Programs Ensure Quality of Fuel in Tanks
May 14, 2008
BY Steven Y. Burris
Fuel quality is perhaps the single most important issue faced by any alternative fuels producer or distributor. Because fuel is transported through numerous channels before it reaches the consumer, there are many points along the distribution chain at which fuel quality may become compromised.
The current storage/distribution infrastructure for handling mineral-based petroleum products was not designed for the dynamics of alternative fuels as they are introduced, substituted and diluted into the system. As environmental and economic pressures dictate the formulation of our fuels, the fuel-handling infrastructure will be impacted, as will fuel quality. Because of the demanding requirements on today's fuel delivery systems, particularly injectors, a clean fuel supply is extremely important.
Contamination Concerns
Oxidation, repolymerization, water, microbial life, rust, waxing and gelling have all been impacting the storage and operability of fuels since the use of petroleum products began.
Cracking heavier products simply accelerated the natural triggers of oxidation and repolymerization that have always existed. The end result of these chemical changes is an infinite variety of new microscopic particulates that stick to each other and form particulates that are big enough to coat tanks, lines, filters, screens and plug nozzles. Adding organic compounds into our fuel will only accelerate these natural processes.
Water is the major cause of the contamination in both mineral and biomass-based fuel. Fuel storage tanks receive water from delivered product, condensation, damaged fill boxes, bad gaskets, loose fittings, and any other non-water/vapor-tight openings. Once the water enters a tank, it falls to the bottom because of gravity. At the bottom, the water is trapped since it is non-soluble with oil.
Aerobic fungus, bacteria and yeast hydrocarbon-utilizing microorganisms begin to grow at the fuel-water interface. Sediments form on the bottom as the organisms go through life processes. As the fuel degrades, sludge, waxes and varnish form. Unfortunately, these processes occur where current fuel supply lines are located. As the layers of sludge and water build toward the fuel pick-up lines, the quality of the fuel severely diminishes. It may become unpumpable and even noncombustible.
Renewables and ULSD
Biodiesel is manufactured from transesterified vegetable oil, animal fat or recycled cooking oil. Biodiesel is a methyl ester, and methyl esters have been used in low volatile organic compound cleaners and solvents for decades.
The problem with introducing biodiesel into diesel storage tanks is that the biodiesel has the tendency of dissolving accumulated sediments into solution. It effectively starts to clean the tank of sludge. This will cause fuel filter plugging and injector scorching. Because of gravity, the contents will be suspended in the lower portion of the tank where current pick up lines are plumbed.
The layer of sludge at the bottom of a tank contains high levels of sulfur. With the required introduction of ultra low sulfur diesel (ULSD) by the U.S. EPA, sulfur content for highway diesel fuel will be reduced from 500 parts per million (ppm) to 15 ppm. The purpose of the rulemaking is to reduce emissions of nitrogen oxides and particulate matter from heavy-duty highway engines and vehicles that use diesel fuel. Sulfur in diesel fuel must be lowered to enable modern-day pollution control technology to be effective. The proposed solution to bring existing inventories within specifications is to blend ULSD into the tank during a phase-in period. In theory, it would require five tank trucks of ULSD to bring a 10,000-gallon tank within specifications.
The only problem with blending is that it depends on 100 percent dilution of both materials. In reality, this will not occur because the sludge will not dissolve into the liquid. Therefore, the sludge will have to be manually removed.
Tank Cleaning Procedure
Before alternative fuel is introduced into an existing tank, the tank should be cleaned. The best method of cleaning a tank is to drain it, enter it, squeegee the bottom, spray the walls and vacuum the contents. This may not be practical because of the expense, time and lack of access into the tank. The preferred method of cleaning a tank is filtering the fuel with low-volume suction. When employing filtration, be sure that the entire bottom is accessed. Filtering at one point in the tank will only clean the immediate area. A good analogy would be cleaning a swimming pool. If you place a suction hose on one end of the pool and there are leaves on the other end, the leaves will remain in place until the
suction wand is over them.
Specifications for a good tank cleaning service should include:
› A contractor willing to provide all labor, tools, equipment and materials necessary to perform the job, including fall protection for aboveground storage tanks, primary and secondary spill containment, and emergency spill kits.
› Before and after samples of fuel straight from the tank for ASTM clear and bright numerical ratings.
› A field report of service and condition of the fuel and tank.
› The mechanical removal of water, microbiological growth and sludge contamination from storage tanks by accessing the entire bottom of the tank.
› Video inspection of the tank interior during the cleaning process.
› Running fuel through a closed-loop filter circulating system utilizing 0.05-micron particulate filters, a coalescing unit and water absorption filters.
› A contractor responsible for capturing, containing, storing, transporting and disposal of all fuel/water contaminants that are generated from the performance of the job.
› An EPA number and manifest for hazardous and/or non-hazardous waste removed.
Unique Tank-Cleaning Techniques
Floating suction is used by the aviation industry to provide the cleanest fuel possible for aircraft. Since contaminants in fuel stratify within the fluid (heavier materials sink to the bottom) clean fuel can be drawn from higher in the column of fluid. One type of floating suction, known as the trademarked FLOATube, is an innovative fuel delivery system that can be attached to existing fuel pick-up lines. The system possesses a floating arm capable of maintaining its position relative to the liquid as the volume changes within the tank.
Since the FLOATube rises and falls with the level of the fuel, the entire capacity of the tank is utilized, ensuring the cleanest fuel is delivered from the tank at all times. If a fuel quality problem occurs, it will be at the bottom of the tank. Since the system draws fuel from the middle of the tank and floats to the bottom with the change in inventory, the tank can remain in service as long as the inventory level remains above the contaminated level. This allows the operator time to schedule a site visit from a tank cleaning service.
Cleaning a fuel storage tank is expensive and time consuming. Once a tank has been cleaned, it would be more economical to remove just the bottom contents periodically before accumulation occurs. This can be achieved by installing a sludge removal system. For example, the trademarked SludgeLine is a permanent suction line that removes contaminants and water from all areas of the tank floor through multiple points of suction. Removing 1 percent of the tank's volume annually will control accumulation. The combination of floating suction and a sludge removal system eliminates the need for tank cleaning. The systems can also be part of a larger fuel quality assurance program.
Fuel Quality Assurance Program
To protect assets and ensure that equipment runs appropriately, a preventive maintenance program should be in place for the fuel and fueling system. A good fuel quality assurance program should include the sampling of storage tanks and the inspection of all fueling components including tanks, vents, caps, dispensers, sumps, gauges, pumps, monitoring systems and foundations. A report should be made with recommendations for corrective action such as fuel treatment, water removal, tank cleaning, fuel filtration and replacement of defective parts.
Biodiesel usage is increasing. In 2004, 30 companies manufactured and marketed 110 MMgy. That capacity is expected to increase to 1 billion gallons per year in 2012. Sulfur restrictions are already in place with a complete phase-in of ULSD by 2010.
With the stricter emission rules and the acceptance of biomass material into our fuel chemistry, a greater demand will be put on our storage/distribution infrastructure. Because of these changes, supply and demand, and political reasons, the cost of fuel will continue to rise. What used to be considered an expense is now an investment. In order to safeguard the investment, consideration should be given to current equipment, operations and maintenance procedures to ensure a good quality product for you and your customers.
Steven Y. Burris is the founder of Petroleum Recovery Services LLC and Fuel Delivery Services, LLC. Reach him at steve@floatube.com or (843) 225-1777.
The current storage/distribution infrastructure for handling mineral-based petroleum products was not designed for the dynamics of alternative fuels as they are introduced, substituted and diluted into the system. As environmental and economic pressures dictate the formulation of our fuels, the fuel-handling infrastructure will be impacted, as will fuel quality. Because of the demanding requirements on today's fuel delivery systems, particularly injectors, a clean fuel supply is extremely important.
Contamination Concerns
Oxidation, repolymerization, water, microbial life, rust, waxing and gelling have all been impacting the storage and operability of fuels since the use of petroleum products began.
Cracking heavier products simply accelerated the natural triggers of oxidation and repolymerization that have always existed. The end result of these chemical changes is an infinite variety of new microscopic particulates that stick to each other and form particulates that are big enough to coat tanks, lines, filters, screens and plug nozzles. Adding organic compounds into our fuel will only accelerate these natural processes.
Water is the major cause of the contamination in both mineral and biomass-based fuel. Fuel storage tanks receive water from delivered product, condensation, damaged fill boxes, bad gaskets, loose fittings, and any other non-water/vapor-tight openings. Once the water enters a tank, it falls to the bottom because of gravity. At the bottom, the water is trapped since it is non-soluble with oil.
Aerobic fungus, bacteria and yeast hydrocarbon-utilizing microorganisms begin to grow at the fuel-water interface. Sediments form on the bottom as the organisms go through life processes. As the fuel degrades, sludge, waxes and varnish form. Unfortunately, these processes occur where current fuel supply lines are located. As the layers of sludge and water build toward the fuel pick-up lines, the quality of the fuel severely diminishes. It may become unpumpable and even noncombustible.
Renewables and ULSD
Biodiesel is manufactured from transesterified vegetable oil, animal fat or recycled cooking oil. Biodiesel is a methyl ester, and methyl esters have been used in low volatile organic compound cleaners and solvents for decades.
The problem with introducing biodiesel into diesel storage tanks is that the biodiesel has the tendency of dissolving accumulated sediments into solution. It effectively starts to clean the tank of sludge. This will cause fuel filter plugging and injector scorching. Because of gravity, the contents will be suspended in the lower portion of the tank where current pick up lines are plumbed.
The layer of sludge at the bottom of a tank contains high levels of sulfur. With the required introduction of ultra low sulfur diesel (ULSD) by the U.S. EPA, sulfur content for highway diesel fuel will be reduced from 500 parts per million (ppm) to 15 ppm. The purpose of the rulemaking is to reduce emissions of nitrogen oxides and particulate matter from heavy-duty highway engines and vehicles that use diesel fuel. Sulfur in diesel fuel must be lowered to enable modern-day pollution control technology to be effective. The proposed solution to bring existing inventories within specifications is to blend ULSD into the tank during a phase-in period. In theory, it would require five tank trucks of ULSD to bring a 10,000-gallon tank within specifications.
The only problem with blending is that it depends on 100 percent dilution of both materials. In reality, this will not occur because the sludge will not dissolve into the liquid. Therefore, the sludge will have to be manually removed.
Tank Cleaning Procedure
Before alternative fuel is introduced into an existing tank, the tank should be cleaned. The best method of cleaning a tank is to drain it, enter it, squeegee the bottom, spray the walls and vacuum the contents. This may not be practical because of the expense, time and lack of access into the tank. The preferred method of cleaning a tank is filtering the fuel with low-volume suction. When employing filtration, be sure that the entire bottom is accessed. Filtering at one point in the tank will only clean the immediate area. A good analogy would be cleaning a swimming pool. If you place a suction hose on one end of the pool and there are leaves on the other end, the leaves will remain in place until the
suction wand is over them.
Specifications for a good tank cleaning service should include:
› A contractor willing to provide all labor, tools, equipment and materials necessary to perform the job, including fall protection for aboveground storage tanks, primary and secondary spill containment, and emergency spill kits.
› Before and after samples of fuel straight from the tank for ASTM clear and bright numerical ratings.
› A field report of service and condition of the fuel and tank.
› The mechanical removal of water, microbiological growth and sludge contamination from storage tanks by accessing the entire bottom of the tank.
› Video inspection of the tank interior during the cleaning process.
› Running fuel through a closed-loop filter circulating system utilizing 0.05-micron particulate filters, a coalescing unit and water absorption filters.
› A contractor responsible for capturing, containing, storing, transporting and disposal of all fuel/water contaminants that are generated from the performance of the job.
› An EPA number and manifest for hazardous and/or non-hazardous waste removed.
Unique Tank-Cleaning Techniques
Floating suction is used by the aviation industry to provide the cleanest fuel possible for aircraft. Since contaminants in fuel stratify within the fluid (heavier materials sink to the bottom) clean fuel can be drawn from higher in the column of fluid. One type of floating suction, known as the trademarked FLOATube, is an innovative fuel delivery system that can be attached to existing fuel pick-up lines. The system possesses a floating arm capable of maintaining its position relative to the liquid as the volume changes within the tank.
Since the FLOATube rises and falls with the level of the fuel, the entire capacity of the tank is utilized, ensuring the cleanest fuel is delivered from the tank at all times. If a fuel quality problem occurs, it will be at the bottom of the tank. Since the system draws fuel from the middle of the tank and floats to the bottom with the change in inventory, the tank can remain in service as long as the inventory level remains above the contaminated level. This allows the operator time to schedule a site visit from a tank cleaning service.
Cleaning a fuel storage tank is expensive and time consuming. Once a tank has been cleaned, it would be more economical to remove just the bottom contents periodically before accumulation occurs. This can be achieved by installing a sludge removal system. For example, the trademarked SludgeLine is a permanent suction line that removes contaminants and water from all areas of the tank floor through multiple points of suction. Removing 1 percent of the tank's volume annually will control accumulation. The combination of floating suction and a sludge removal system eliminates the need for tank cleaning. The systems can also be part of a larger fuel quality assurance program.
Fuel Quality Assurance Program
To protect assets and ensure that equipment runs appropriately, a preventive maintenance program should be in place for the fuel and fueling system. A good fuel quality assurance program should include the sampling of storage tanks and the inspection of all fueling components including tanks, vents, caps, dispensers, sumps, gauges, pumps, monitoring systems and foundations. A report should be made with recommendations for corrective action such as fuel treatment, water removal, tank cleaning, fuel filtration and replacement of defective parts.
Biodiesel usage is increasing. In 2004, 30 companies manufactured and marketed 110 MMgy. That capacity is expected to increase to 1 billion gallons per year in 2012. Sulfur restrictions are already in place with a complete phase-in of ULSD by 2010.
With the stricter emission rules and the acceptance of biomass material into our fuel chemistry, a greater demand will be put on our storage/distribution infrastructure. Because of these changes, supply and demand, and political reasons, the cost of fuel will continue to rise. What used to be considered an expense is now an investment. In order to safeguard the investment, consideration should be given to current equipment, operations and maintenance procedures to ensure a good quality product for you and your customers.
Steven Y. Burris is the founder of Petroleum Recovery Services LLC and Fuel Delivery Services, LLC. Reach him at steve@floatube.com or (843) 225-1777.
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