Screw press application in oily sludge dewatering
Currently, the primary mechanical dewatering tools for oily sludge used worldwide are plate and frame filter presses, belt filter presses, centrifugal dehydrators, and screw presses. This article will focus on the use of the screw press for sludge treatment.
Introduction to the oily sludge
In recent times, there’s been a significant uptick in oilfield surface engineering construction projects. The sewage treatment system plays a pivotal role in these ground engineering constructions, with the oily sludge treatment system being essential.
Oily sludge typically comprises water-in-oil and oil-in-water emulsions, as well as suspended solids. The particles within oily sludge are both cohesive and fine, often appearing in flocculated forms. Moreover, they have a minimal density difference from water, retain high water content, and given the extensive use of chemicals in the sewage treatment system, the makeup of this sludge is intricate. Its serious emulsification makes it hard to settle, and its susceptibility to decomposition leads to foul odors, air pollution, and significant environmental harm. Given the rising environmental protection standards, neutralizing, minimizing, and recycling oily sludge has become a pressing developmental trend.
What is a screw press?
The screw press is an emerging sludge dewatering tool that has swiftly evolved, innovated, and gained popularity in our nation. Its ease in separating mud from water and resistance to clogging has led to its successful implementation in locations like Yanchang Petroleum in Shaanxi, Shengli Oilfield in Shandong, and Hailaer Oilfield in Daqing.
What is a screw press? A screw press is a machine that uses a rotating screw to press sludge against a permeable filter to drain water and produce a dry sludge cake. The screw p...
How does a screw press work?
The screw press employs the screw extrusion principle to achieve sludge concentration and filter press dehydration within a single cylinder. Once the sludge is introduced into the filter body, the turning of the screw shaft causes the fixed ring and the moving ring to move relative to each other so that the filtrate quickly flows out from the lamination gap to achieve rapid concentration; as the screw shaft keeps moving forward, the sludge moves to the dewatering area, and as the filter gap and screw pitch gradually become smaller, the space in the filter cavity continues to shrink. Then, the internal pressure of the sludge continues to increase to achieve dehydration, and mud cake is formed after dehydration.
Application example of screw press
The screw press was first applied in the fishery and food industries. In recent years, it has been gradually developed and applied to the petroleum and chemical fields.
It has been consistently enhanced and innovated to handle the corrosive operational conditions presented by oily sludge with high viscosity and elevated chlorine content. At present, it has been initially applied in domestic petroleum and petrochemical industries such as Qilu Petrochemical, CNOOC Offshore Platform, Daqing Oilfield, and Shengli Oilfield.
The treatment of oily sludge in the Hailaer Oilfield Combined Station is used to discharge the sludge from the settling tank into the sludge storage tank and recover the supernatant. Because a large amount of oil sludge is placed in the sludge storage tank in the open air, it is very easy to produce rot and stench, polluting the air and the surrounding soil environment. Affected by the climate, it cannot be operated in winter, and the recovery of the supernatant will cause the sludge to re-enter the sewage treatment system, causing a vicious cycle. The quality of the effluent water is not up to standard. In order to solve the above problems, the combined station uses a screw press to treat the oily sludge in the sewage recovery tank. After the sludge is treated, the emulsified mud layer in the sewage disappears, which reduces the difficulty of sewage treatment, significantly improves the quality of the effluent, and reduces environmental pollution.
The application of a screw press effectively reduces the environmental hazards and risks of oily sludge. Compared with other types of dehydrators, it can reduce sludge thickening equipment, simplify chemical dosing equipment and auxiliary facilities, thereby simplifying the process flow, and has the characteristics of relatively low investment, small floor space, low operating costs, and a wide range of applicable sludge concentrations. It is a better choice for dewatering oily sludge in oil fields.