Sludge Management
Over the last thirty years oil sludge has become a significant issue for asset owners and contractors. Tank bottom sludge (TBS) is normally a combination of hydrocarbons (oil), sediment (sand & rust), paraffin, wax and water and may include harmful by products such as sour gas, xylene, polycyclic aromatic hydrocarbons, benzene, heavy metals, toluene, and ethyl benzene.
For asset owners TBS can have serious consequences in that it reduces ullage capacity, promotes corrosion, restricts pipeline flow rates, increases wear and tear on pumps and has significant costs when disposed.
In 2015 the World Bank estimated the volume of material in storage tanks, ponds, lagoons and other storage areas was nine billion cubic meters of oil. Its widely thought that this estimate was conservative and the true number a lot higher. That number doesn’t include ponds or pits containing oil from remediation activities that are currently ongoing in countries such as Libya, Iraq and Kuwait. In the ten years since that report was released it entirely feasible that the volume of material could have reduced, however many in the industry believe the number has increased significantly. This is due to the costs involved of treatment or disposal.
Typically TBS was sent for hazardous disposal via landfill. An alternative was high temperature thermal treatment.
NEL have designed, built and sold equipment that not only makes recovery of the sediment in tanks possible but also equipment to harvest and process the sediment into valuable oil, clean water and cleaned sediment.
Sludge Mapping & Quantification
The first step in any project is to know the location & volume of material to be removed and/or processed. NESL have two systems available to accurately determine the makeup of the sludge.
The first is using acoustic measuring equipment. The acoustic inspection system uses solid state acoustic technology to generate a scan of beams that measures the sludge distribution over thousands of points within a tank.
On tanks under forty metres in diameter it is possible to scan the tank from one central position but larger tanks over forty metres in diameter require scan from several positions to enable the data to be merged to give a composite image of the distribution and a sludge volume for the entire tank.
The system is ATEX-certified which makes it suitable for all types of products. The profiler is inserted into the product through the roof support entry-point or manhole entry without the need for the tank to be emptied. Only a small team of our experts is required, minimizing the number of people on the tank roof. By using our advanced software, the survey usually takes only just a day, which makes it fast and cost-efficient.
After processing the raw data, we provide you with a clear report with the sludge distribution represented in a 3-D contour map. We calculate the sludge volume for the entire tank in cubic meters or cubic feet and present information on the actual pile height
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NES Extractor ROV
The Extractor ROV is a standalone system or a bolt on to the HPWJ ROV, that allows for simultaneous jetting and extraction of wash water and product.
The ROV is built to allow for the attachment of vacuum hoses to a connection on the back of the chassis, however it is customisable to allow for an onboard pump to be fitted, this does however increase the units weight and ability to be inserted through the manway.
If ordered with an onboard pump, this unit is better suited to tanks with “D” doors fitted.
The ROV is certified for use in a Zone 1 area (ATEX Group II Cat 2) and the unit includes an anti-static umbilical for extra protection. All electrical components are EX certified, and all fluid path material is stainless steel.
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Tanksweeps
The NESL Tanksweep system is designed for the de-sludging of petroleum & chemical storage tank by the control and circulation of high velocity liquid streams through directable nozzles fitted to the tank shell. Depending on the size of the tank and the product stored up to four sets of tank sweeps might be required with each of them where possible spaced evenly around the tank perimeter. The tanksweeps are all a standard length but where space is restricted a more compact version is available.
Each system is comprised the following major components:
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Tank Sweep Unit
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Filter Units
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Centrifugal Pump Unit
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Hose Set
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Bolt Kit
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Hydraulic Jacking Pump
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Each Tanksweep is capable of a throughput of six hundred and sixty cubic meters per hour when used in conjunction with the NES 500D at a pressure of ten bar and has a sweep angle of two hundred degrees.
The NES 500D pump unit is certified for use in areas classified as a Zone II. Each unit is fitted with automatic shutdown protection including a gas detector, chalwyn valve, and spark arrestor.
Semi/Permanent Tanksweeps
The success of NES Tanksweeps used on problem tanks where the sludge level was above the manways and required a hot-tap to insert Tanksweep has led to the development of the fixed Tanksweep.
NES Fixed Tanksweeps are for use in new tanks or tanks that have been cleaned and are about to be put back into service. Alternatively, they can be used on tanks where the manway can be removed for cleaning and used to re-suspend accumulated solids enabling the tank to be pumped down with a maximum contents removal effected without man entry.
Fixed Tanksweeps are simple to install by using the existing manways and can be connected to the tank operators own pumps and existing pipework.
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The number of tanksweeps required depends on the tank diameter. Typically 2 Tanksweeps are required for tanks up to 50m in diameter, 3 Tanksweeps are required for tanks with diameters between 50m and 80m, and 4 Tanksweeps are required where the tank has a diameter greater than 80m.
Tanksweeps will prevent a build-up of sludge on the tank floor by creating a movement in the oil inside the tank. This movement ensures that any solids are suspended in the mobile oil and do not settle on the tank floor.
Tanksweep nozzles can be rotated 200 degrees either manually from the outside of the tank by means of a hand wheel, or the unit can be hydraulically controlled.
ATC Mud Cannon
ATC Tank Cleaning System (ATC) comprises three main elements:
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Wash system
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Recovery system
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Separation process.
The wash system incorporates an operator control station, a jetting pump, smart nozzle and the umbilical which reaches between the ATC and the nozzle head.
The recovery system comprises a vacuum truck which has been fitted with a modified top manway hatch which has a floating suction installed, and the vacuum hoses between the PSV tank and the vacuum truck
The separation process starts in the vacuum truck, where the liquid and solid portions of the recovered waste are separated, and extends into the ATC where the fluids are transferred through a filtration system into the wash fluid reservoir using one of the jetting pumps. Within the wash fluid reservoir a further separation takes places using a top weir and surface skimming system to remove the oil element of the liquid transferred from the vacuum tanker.
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