Piston Press Dewatering Saline Sludge with Flexible Drains
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current dehydration processes for sludge from seawater desalination cannot achieve high dryness levels of at least 30% and are inefficient in reducing salt concentration, especially for sludge with salinity between 5 and 50 g/l, and often result in high energy consumption and environmental pollution.
Innovation Solution
A piston press dehydration process using flexible drains and alternating pressures, combined with the injection of drinking water and a strongly alkaline reagent to reduce salt concentration and enhance dehydration efficiency, while maintaining high dryness levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dehydration processes are used for saline sludge, then the process is simpler, but the dryness content remains below 30% and salt concentration is not reduced
Solution Approach 1:
The dewatering process is divided into multiple distinct phases: filling phase with polyelectrolyte injection, dewatering phase with pressing, and washing phase with potable water injection. The press operation is segmented into forward piston movement for pressing and backward movement for draining, allowing each phase to be optimized independently to achieve high dryness content
Solution Approach 2:
The sludge is pre-conditioned with polyelectrolyte during the filling phase before the actual dewatering process begins. This preliminary action modifies the sludge properties to facilitate better dewatering performance and enable the achievement of dryness content above 30%
2Object-generated harmful factors
If conventional pressing methods are used, then energy consumption is lower, but salt concentration in the sludge remains high causing environmental pollution
Solution Approach 1:
The piston press operates in periodic cycles, alternating between forward movement (pressing phase) and backward movement (draining and washing phase). During the backward movement, potable water is injected to wash salts from the sludge. This periodic action enables salt removal without requiring continuous high energy input, as the system utilizes the natural drainage phase for washing
Solution Approach 2:
Potable water is introduced as an intermediary substance during the washing phase to facilitate salt removal from the sludge. The water acts as a medium that dissolves and carries away salts during the backward piston movement, reducing salt concentration in the dewatered sludge without requiring additional energy-intensive treatment processes
3Productivity
If the piston press uses rigid drains, then the structure is simpler, but the draining efficiency is reduced due to inability to adapt to sludge compression
Solution Approach 1:
The drain structure is designed with flexible elements that can dynamically adapt to the compression forces applied during dewatering. The flexible drains deform under pressure to maintain contact with the sludge matrix, ensuring continuous drainage pathways are maintained throughout the compression process, thereby maximizing dewatering efficiency
Solution Approach 2:
The drain structure incorporates flexible shells or films that can bend and deform under the varying pressure conditions during the pressing cycle. This flexibility allows the drains to conform to the compressed sludge geometry, maintaining effective drainage surfaces and preventing channeling, thus improving overall dewatering performance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process achieves sludge dryness greater than 30%, reduces energy consumption, and minimizes environmental impact by lowering salt concentration, making the dehydrated sludge less polluting and suitable for discharge into natural environments.
Implementation Method 1
flexible drains formed by flexible sheaths of material permeable to liquid but impermeable to solids, each drain comprising an internal passage which opens into an associated opening, the press operating in batches, and in that during pressing, the piston makes back and forth movements and applies alternating and variable pressures on the sludge, while the flexible drains deform, the expressed liquid of the product passing through the wall of the drains and being discharged as filtrate
Implementation Method 2
during pressing, the piston makes back and forth movements and applies alternating and variable pressures on the sludge
Implementation Method 3
the injection of potable water in a volume between 50% and 150% of the volume of sludge subjected to a dewatering cycle, this injection being carried out during the dewatering cycle or during the sludge filling phase of the piston press in a sufficiently high dosage, to reduce the salt concentration of the dewatered sludge while maintaining a high dryness
Implementation Method 4
an injection of potable water with added highly alkaline reagent can be carried out at a sufficiently high dosage to precipitate metals in the dewatered sludge and increase the final dryness of the dewatered sludge to a value greater than 35%
Data Source
Figure 1
Figure 2~4
Figure 5
AI summary
A method for the forced dewatering, by pressing, of saline residues produced by drinking water production, or by the treatment of municipal or industrial wastewaters, in which method the saline residues are introduced into the cylinder (12a) of a piston press (12) comprising flexible drains (12e) formed by flexible sheaths from a material that is permeable to liquid but impermeable to solids, each drain (12e) comprising an inner passage that opens into an associated opening (12g), the press operating in batches, and characterised in that during pressing, the piston carries out reciprocal movements and applies alternating and variable pressures to the sludge, while the flexible drains are deformed, the liquid pressed out from the product passing through the wall of the drains and being discharged as a filtrate, while the dewatered sludge remains outside the drains and is discharged by opening the press.