Treatment technology for the “three types of sludge” in refineries
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At present, domestic petrochemical companies mainly handle sludge by concentrating and dehydrating it to reduce its oil content, and then dispose of it through landfilling or other methods. Its process mainly involves solid-liquid separation. Therefore, the level of moisture and oil content in the dried sludge after treatment serves as indicators to measure the effectiveness of this sludge treatment process. The Power Plant of Lanzhou Petrochemical Company initially used vacuum filters for the treatment of sludge. Method of incineration in an incinerator ； Due to the large amount of smoke and dust generated during incineration, which pollutes the environment and results in high energy consumption, the method was later changed to centralized landfilling of the sludge cakes produced by the filter. The sludge cake produced after filtration by the filter has a high water and oil content, and the labor intensity is high. To improve processing capacity and efficiency, the HILLER three-phase horizontal screw centrifuge is mainly composed of a drive unit, a rotating drum, and a screw conveyor. It features a compact structure and small size. Its operation is based on the principle of sedimentation; that is, solid particles that are heavier than the liquid settle out within a predetermined time. This principle can also be applied to two liquids with a difference in specific gravity that are immiscible with each other. When the material enters the high-speed rotating drum, it rotates inside the drum in sync with it. Due to differences in specific gravity, the centrifugal force acting on each particle varies; solid particles with higher specific gravity experience the greatest centrifugal force, followed by water, and the least by contaminated oil. As a result, a concentric layer of solids and two layers of liquid are formed, from the outside inward, depending on the magnitude of the centrifugal force applied. The solids are pushed out by a screw conveyor, while the liquids are discharged through their respective liquid guides. Therefore, the use of a three-phase horizontal screw centrifuge not only allows for the separation of solids from the three types of sludge, but also enables the separation of oily substances from them, thereby facilitating solid-liquid-liquid separation. German HILLER horizontal spiral centrifuge
Now, the sludge generated by refineries in treating wastewater is being disposed of through incineration; previously, it was mainly landfilled.
Principle of three-sludge treatment: feeding – demulsification – conditioning – sludge-water separation – chemical addition – centrifugal dewatering – drying – bagging. Equipment for tri-clay treatment ； The sludge oil system includes a sludge oil inlet (sludge adjustment tank), filters, and a sludge pump; the flow rate is adjusted according to the annual processing volume (sludge separation unit), where demulsification takes place. The sludge oil after demulsification is sent to a water-oil separator, and after separation, it is pumped back into the sludge oil system by a sludge oil pump. There is also a demulsifier tank and a demulsifier pump, as well as a conditioner tank and a conditioner pump. The pH value of the material after conditioning is kept between 6 and 8. The conditioned material is then sent to a sludge-water separator; after treatment, the water is sent to a wastewater treatment plant. After going through these processes, the sludge is pumped using a sludge pump and a dosing pump, and then fed into a centrifugal dehydrator. The dehydrated sludge is stored in a sludge tank, while the dehydrated wastewater is sent to a wastewater treatment plant. The sludge in the tank is pumped using a dry sludge pump and sent to a paddle dryer for drying. The gases generated during the drying process are directed to a water seal purification tower for cleaning. The dried mud can meet the **required emission standards**. It can also be sent to the incineration system for burning. The entire system utilizes a (PLC) automatic interlock system. It’s very easy to use.
There are currently no good methods for resource recovery. Dongxing also has many problems. New technologies still need to be developed