Multi-effect Distillation for RO Reject De-scaling
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Solution Overview
Problem
The disposal of reverse osmosis (RO) reject streams from unconventional wastewater treatment plants poses environmental and health risks due to high levels of endotoxins and toxicity, and the existing treatment systems are costly and inefficient, leading to excessive waste generation and potential contamination of water sources.
Innovation Solution
A multi-effect distillation and de-scaling method utilizing produced water, blowdown steam, and return condensate to remove calcium hardness, magnesium hardness, and silica, producing de-scaled heated brine for improved oil recovery, thereby reducing waste and environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wastewater treatment systems are used to treat RO reject streams, then treatment capacity is provided, but treatment cost increases and waste generation becomes excessive
Solution Approach 1:
The treatment process is divided into three distinct stages: (1) de-oiling stage using hydrophobic membrane contactors to remove oil, (2) de-scaling stage using chemical precipitation to remove calcium and magnesium hardness, and (3) distillation stage using multi-effect distillation to produce fresh water. This segmentation allows each stage to target specific contaminants efficiently, reducing overall system complexity while maintaining treatment effectiveness.
Solution Approach 2:
The multi-effect distillation system serves multiple functions: it produces fresh water for reuse, concentrates brine for disposal, and recovers heat from the process. The hydrophobic membrane contactors simultaneously perform mass transfer and phase separation. This multi-functionality reduces the need for separate treatment systems, lowering overall device complexity.
2Reliability
If existing treatment methods are applied to RO reject streams, then some treatment is achieved, but waste generation increases and environmental contamination risk rises
Solution Approach 1:
The system recovers fresh water from the distillation process for reuse in oilfield operations, recovering valuable water resources. The concentrated brine is carefully managed and disposed of in a controlled manner. Oil is recovered from the de-oiling stage and can be reused or properly disposed of. This approach minimizes waste generation by maximizing resource recovery from the RO reject stream.
Solution Approach 2:
The high salinity and temperature of the RO reject stream, which are typically harmful characteristics, are converted into benefits. The high temperature reduces the energy requirement for distillation, and the high salinity facilitates efficient chemical precipitation of scale-forming minerals. The system transforms what would be problematic waste characteristics into process advantages.
3Loss of substance
If multi-effect distillation is used to treat RO reject streams, then waste reduction is achieved, but energy consumption increases
Solution Approach 1:
The multi-effect distillation system uses periodic heating and cooling cycles across multiple effects, where vapor from one effect condenses and heats the next effect in sequence. This periodic action allows efficient heat transfer and minimizes energy loss. The system operates in a cyclic manner that maximizes energy utilization throughout the distillation process.
Solution Approach 2:
The system exploits phase transitions of water (liquid to vapor and vapor to liquid) across multiple effects to transfer heat efficiently. Each effect utilizes the latent heat of condensation from vapor generated in the previous effect, creating a cascading energy transfer system that minimizes external energy input requirements while achieving significant waste reduction.
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
This approach effectively treats the RO reject streams, reducing waste generation and environmental contamination while providing a cost-effective and efficient means to produce de-scaled brine for enhanced oil recovery, improving the economic and environmental sustainability of the process.
Implementation Method 1
The multi-effect distillation and de-scaling method utilizing produced water, blowdown steam, and return condensate
Implementation Method 2
multi-effect distillation
Implementation Method 3
remove calcium hardness, magnesium hardness, and silica
Data Source
AI summary
Providing new distilling and/or de-scaling methods and systems herein is a matter of allowing for thermal balance without the need to fill a hot wet emulsion separation system with more steam and heat rejection devices to waste steam. One embodiment begins with efficiently utilizing three types of waste: (1) hot produced water along with its inherited thermal energy; (2) blowdown steam from drum-type boilers (DBs); and (3) return condensate of dry steam from the DBs. It ends with: (1) removing calcium hardness, magnesium hardness and silica, thereby recovering them as useful minerals; and (2) producing distillate for viscous oil recovery by steam injection and de-scaled hot brine for improved oil recovery by hot water flooding and/or other related methods. The vehicle to attain this set of solutions is a recycle brine multi-effect distillation (RB-ME) train comprises a forward feed section and a backward feed section along with two flashing stages.