Wet Air Oxidation Scale Reduction via Temperature Moderation
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Solution Overview
Problem
Wet air oxidation (WAO) systems face significant scaling issues due to scale-forming contaminants like calcium sulfate, leading to system shutdowns and inefficiencies, with existing solutions being time-consuming and hazardous, such as hot nitric acid washes, which require system downtime.
Innovation Solution
Implementing a system with a scale reducing heat exchanger that moderates the temperature of treated materials before they enter a second heat exchanger, keeping scale-forming contaminants in solution by maintaining temperatures below their solubility limits, thereby reducing scaling in WAO systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high temperature and pressure conditions are used in WAO systems to oxidize contaminants, then oxidation efficiency is improved, but scaling due to inverse solubility of calcium sulfate worsens
Solution Approach 1:
The patent applies preliminary action by pre-heating the feed stream in a heat exchanger before it enters the WAO reactor, using the hot effluent stream as the heating medium. This temperature moderation prevents the feed stream from exceeding the solubility temperature of calcium sulfate, thereby preventing scale formation in upstream components while still achieving the required oxidation conditions in the reactor.
2Object-generated harmful factors
If hot nitric acid wash is used to remove scale forming contaminants, then scaling is reduced, but system downtime and operational complexity increase
Solution Approach 1:
The patent converts the harmful effect of hot effluent stream into a beneficial heating source. The hot effluent, which would normally cause scaling if directly contacted with the feed stream, is instead used as the heating medium in the heat exchanger. This allows temperature control that prevents scaling while utilizing the thermal energy, eliminating the need for separate acid washing operations.
3Use of energy by moving object
If temperature of treated material is not moderated before entering heat exchanger, then heat transfer efficiency is improved, but precipitation and accumulation of scale forming contaminants worsens
Solution Approach 1:
The patent applies parameter changes by controlling the temperature of the treated material entering the heat exchanger to remain below the solubility temperature of calcium sulfate. By adjusting this temperature parameter, the system prevents precipitation and accumulation of scale forming contaminants while still achieving effective heat transfer for process efficiency.
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
Substantially reduces the incidence of undesired scaling in WAO systems, preventing system shutdowns and maintaining efficiency by ensuring scale-forming contaminants remain soluble, thus preventing their precipitation and accumulation in heat exchangers and other components.
Implementation Method 1
a scale reducing heat exchanger that moderates the temperature of treated materials before they enter a second heat exchanger
Implementation Method 2
keeping scale-forming contaminants in solution by maintaining temperatures below their solubility limits
Data Source
AI summary
There is provided a system and a method for regenerating a material that reduce the incidence of scaling due to scale forming contaminants. The method may include reducing a temperature of a treated material exiting a wet air oxidation unit in a scale reducing heat exchanger prior to delivery of the treated material to a second heat exchanger which heats a source waste material comprising a scale forming contaminant therein with heat from the first treated material to form a heated waste material comprising the scale forming contaminant.