Oil tank sludge removal process

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I. Introduction of the problem: When oil storage tanks are used to store oil, especially crude oil, over time small amounts of mechanical impurities, sand particles, soil, heavy metal salts, as well as heavy oil components such as paraffins and asphaltenes settle at the bottom of the tank due to differences in density. This results in the formation of a dark, thick gel-like layer. It is generally necessary to remove this layer during regular tank cleaning every 5 to 6 years; this process gives rise to tank sludge, whose volume typically accounts for 1% to 2% of the tank’s capacity. Tank bottom sludge differs from ordinary oily sludge; due to its extremely high hydrocarbon content, it is an excellent resource that can be recycled. Long-term investigations and tests have shown that the sediment at the bottom of oil tanks contains about 25% water and 5% inorganic substances such as silt; the remaining 70% is composed of hydrocarbons (of which asphaltenes account for 7.8%, paraffins for 6%, and ash for 4.8%). Through appropriate separation techniques, the hydrocarbon recovery rate can exceed 98%. Therefore, if no effective measures are taken to recycle and reduce the amount of sludge at the bottom of the tanks, it will result in a significant loss of oil resources and cause environmental pollution. Developed countries **have long established relevant regulations that explicitly prohibit personnel from entering tanks to carry out tank cleaning tasks. At present, many domestic enterprises are adopting the “HSE” management model for safe production, which involves integrating health, safety, and environment into a unified management system. Traditional tank cleaning methods require personnel to enter and carry out manual work. Even after the tank has been subjected to processes such as steaming and ventilation over an extended period of time, the interior of the tank remains filled with oil vapor and gas, which severely harms the health of the workers. It can even lead to poisoning incidents and problems related to unpleasant odors. II. Domestic methods for tank cleaning and treatment of tank bottom sludge\nFor tank cleaning, when a tank reaches the scheduled time for cleaning, the commonly used method in China is as follows: after extracting as much crude oil as possible from the tank, an appropriate amount of water is poured in along with steam – this is what is known as \"steam cleaning\". Once the temperature reaches a certain level, some of the oil does not rise to the surface from the milky sludge present at the bottom; thereafter, the oil on the surface is pumped out, completing one cycle of steam cleaning. Under normal circumstances, in order to recover as much oil as possible from the sediment, two or more “distillation tank” treatments are usually employed. After treatment in the \"steaming tank,\" the manhole is opened for natural or forced ventilation; at the same time, the cleaning hole at the bottom of the oil tank is opened to allow the flowing oil and water along with some sediment to flow automatically into the sediment storage tank located next to the oil tank. Once the self-flowability of the sediment deteriorates until self-flowing ceases, gas samples are taken from the tank; only after the explosion tests prove successful can operators enter through the manhole to carry out manual sediment removal and tank cleaning. Due to the numerous processes required for preparation, the complexity of the steps involved, and the high level of risk, the entire process of tank cleaning takes a considerable amount of time. As an example, cleaning a 50 km3 tank generally requires 45 to 50 working days. The treatment method for oil tank sludge involves the addition of clean water during the \"vaporization\" process, along with flash water generated by the steam; this not only increases the total amount of sludge but also requires an emulsification-breaking step in the sludge treatment process, resulting in higher difficulties and energy consumption. Therefore, the common practice is to send the sludge from oil tanks to some small oil processing plants located near the factories to produce refined oil, or to use it as fuel in brick and tile factories. This approach results in low utilization rates, and since these makeshift oil processing plants or brick and tile factories lack proper environmental protection measures, secondary pollution easily occurs during the transportation and reuse of the oil tank sludge. Some factories have begun to explore methods for recycling sludge, such as sending it to coking units for catalytic coking reactions, but these methods still rely on manual tank cleaning. The obvious disadvantages include the following: first, the insecurity of having workers enter the tanks and the potential harm to their health; second, there is still a risk of secondary pollution during the transfer of sludge from the oil tank area to the facilities for its comprehensive utilization; third, the economic inefficiency of recovering and reusing petroleum resources. III. Micava’s tank cleaning technology products: Micava provides the oil industry with unique chemical products for cleaning oil-contaminated waste, drill cuttings, drilling mud, heavy crude residues, and refinery waste. Many oilfield service companies, waste management companies, and tank cleaning companies use Micava’s tank cleaning products. Our products can effectively treat various oil-contaminated wastes and are widely used around the world. From gasoline to naphtha, from crude oil to heavy fuel oil, Micava’s products can effortlessly convert any pollutants into a liquid form and remove them. Recycle 95% of the oil from waste ； Reduce waste by 60 - 98%. Moreover, this product is biodegradable, with low residues in oil. The products offered by Micava for the treatment of refinery waste and heavy fuel oil residues are based on microemulsion technology. They are used for cleaning refineries and storage tanks, and can effectively remove crude oil residues, bottom sediment, heavy fuel oil, as well as most other hydrocarbon residues and wastes. Micava’s unique chemical products make it possible to recover oil from refinery waste or heavy oil residues. These products can rapidly reduce the viscosity of the oil sludge, allowing it to be removed easily, so that a horizontal screw centrifuge can be used to separate the oil sludge. The result of the separation is a dense dry cake containing all the solid waste. The recovered liquid can be separated into oil and water under the force of gravity. Reclaimed oil can be reprocessed by refineries, while reclaimed water can be treated through standard wastewater treatment processes. Oil recycling products enable the separation of waste materials without the need for heating, resulting in higher-quality recycled oil, which adds value to the oil recycling process. Most oil recycling processes require heating. The waste stream must be heated to 70-95 degrees Celsius in order to recover the oil in its free state. The oil recovered in this way usually still has a high water content. Micava’s products ensure a very low moisture content