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Walnut Filter Skid for Efficient Oil Removal in Offshore Produced Water Treatment
Walnut shell filters are highly effective for oily wastewater treatment and are widely regarded as the ideal technology for produced water treatment in oilfields.
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Product Introduction
Walnut shell filters are highly effective for oily wastewater treatment and are widely regarded as the ideal technology for produced water treatment in oilfields.
Due to the oleophilic nature of the filter medium, walnut filters can effectively adsorb and remove dispersed oil. To meet the requirement for compact space on offshore platforms, these systems are commonly designed as skid-mounted packages, enabling integrated transportation and rapid installation.
The Walnut Filter Skid should be applicable to offshore environment, and We should at our own cost arrange inspection and obtain final certificate of the package from one of the certifying agencies authorized by COOOSO, which are ABS, DNV, BV and CCS etc.
Key Advantages & Features
• Efficient Oil Removal & Stable Effluent Quality: The filter medium features oleophilic and hydrophobic properties, exhibiting strong adsorption capacity for oil droplets and organic matter. It can consistently reduce outlet oil content to below 15 mg/L.
• Easy Regeneration & Long Service Life: The filter medium possesses excellent wear resistance. During backwashing, mechanical friction effectively strips away oil contaminants, ensuring strong regeneration performance and low long-term operational costs.
• Reliable Filtration Performance: With moderate density and a well-structured pore system, the filter requires low backwashing energy and achieves effective fluidization. It efficiently captures suspended solids while maintaining high filtration velocity and throughput.
• Eco-Friendly & Cost-Effective, Using Renewable Materials: Raw materials such as walnut shells—agricultural waste products—are utilized, enabling resource recycling. The medium can be cleaned and regenerated, resulting in low overall operation and maintenance costs.
• Skid-Mounted & Integrated, Adapted to Offshore Requirements: Designed as a fully modularized package for easy offshore transportation, installation, and commissioning. Meets platform space constraints and rapid deployment needs.
Structure and Working Principle
The walnut shell filter/system consists of the walnut shell filter (tank body, filter media, backwash mechanism), supporting instruments, valves, pipelines, automatic control system, platforms, ladders, railings, skid base, etc.
During filtration, oily wastewater enters the filter from the top, and water is evenly distributed on the surface of the walnut shell filter media through the water distribution device. The wastewater is filtered from top to bottom through the walnut shell filter layer. The oil in the wastewater fully contacts the walnut shell filter media and is adsorbed on the surface of the filter layer. At the same time, suspended solids are intercepted and removed by the walnut shell filter media as they pass through it. The clean water is discharged from the bottom of the filter. As time goes on, the pollutant-holding capacity of the filter layer continuously increases, and the filter layer tends to become saturated. At this point, the filter media needs to be backwashed and regenerated. Control method:
The main working process of the walnut filter is shown in the following figure:
Component
There are two types of motors for walnut filters: vertical and horizontal. They can be produced and customized according to specific requirements.
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Vertical and Horizontal Motors
To ensure uniform water distribution and high-quality effluent, the filter typically employs a radial structure for water distribution and a baffle nozzle design for water collection.
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Distribution/Collection Device
| The filter media is made of light walnut shells with a specific particle size, which has good hydrophilic and oleophobic properties for oil removal, and strong impurity adsorption and interception capacity. The filter media can be backwashed and regenerated, has strong compressive strength, stable chemical properties (not easily dissolved in acid or alkali solutions), high hardness, good wear resistance. |  |
Technical Specifications
| Parameter | Specification |
| Single Unit Capacity | 5~200m3/h |
| Design Pressure | 0.6MPa，1.0MPa，1.6MPa，or specified |
| Design Temperature | 120℃ |
| Filter Medium Specification | 0.6~1.2mm |
| Filling Height | 1200~1400 mm |
| Filtration Velocity | 4~20 m/h |
| Backwashing Method | Mechanical Stirring + Backwash Water Rinsing |
| Backwash Period | 12~24 h |
| Backwash Duration | 15~20 min |
| Water Backwashing Intensity | 6~15 L/(m2.s) |
| Outlet | Oil Content≤15mg/L，Suspend Solid Content≤10mg/L，Suspend Solid Particle Size≤4μm or designed according to the requirements of the inlet water and outlet water |
| Operation Mode | Switchable for Automatic, Semi-automatic, Manual |
walnut shell filter medium
| Density | ≥1.25 g/cm3 |
| Bulk Density | 0.8 g/cm3~0.85 g/cm3 |
| Wear and Damage Rate | ≤3% |
| Mud Content | ≤2.0% |
| Hydrochloric Acid Solubility | ≤3.5% |
| Skin Shell Rate | ≤0.3% |
| Impurity Rate | ≤0.3% |
| Cleanliness | ≥7% |
Application Fields
• Treatment of oily wastewater from land and offshore oilfields, petrochemical, and metallurgical industries.
• Treatment of oily wastewater from ports, terminals, and oil depots.
• Treatment of oily wastewater from vessels and other sources.
• Filtration treatment for the reuse and recycling of oily wastewater and other oily wastewater in circulation systems of the steel, metallurgical, and coal industries.
• Fine filtration for large-scale reinjection water in oilfields, treatment of produced water from offshore oil platforms, and treatment of regenerated water for thermal recovery boilers in heavy oil fields.
• For the filtration and advanced treatment of cooling circulating water in power plants, refineries, and petrochemical plants.
