Scale Mitigation in Phosphoric Acid Evaporators
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Solution Overview
Problem
The formation of scale in phosphoric acid plants is a persistent issue, leading to reduced efficiency, increased production costs, and significant downtime due to the accumulation of hard, intractable scales on heat exchanger surfaces, which are difficult to clean and can cause equipment damage.
Innovation Solution
A method involving the use of an aqueous scale-mitigating composition comprising polyamino polyether methylene tetraphosphonate, a copolymer of acrylic acid and 2-acrylamido-2-methylpropane sulfonic acid, and additional polymers is applied to phosphatic compositions to form a second phosphatic composition, which is then contacted with scale-accumulating surfaces, resulting in the deposition of softer, more easily removable scales.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If phosphoric acid is concentrated in an evaporator, then the acid concentration increases, but scale accumulates on heat exchanger surfaces reducing efficiency
Solution Approach 1:
The patent applies scale-mitigating compositions to phosphoric acid before it contacts the heat exchanger surfaces in the evaporator. This preliminary treatment prevents scale formation at its source, allowing concentration to proceed without the subsequent efficiency loss that would require shutdowns for cleaning
Solution Approach 2:
The scale-mitigating composition acts as an intermediary substance between the phosphoric acid and the heat exchanger surfaces. It modifies the interaction by preventing direct adhesion of scale-forming materials to the metal surfaces, thereby maintaining heat transfer efficiency during concentration
2Productivity
If scale accumulates on heat exchanger surfaces, then production continues, but cleaning requires shutdown and mechanical effort
Solution Approach 1:
By applying scale-mitigating compositions before scale formation occurs, the patent prevents the need for subsequent cleaning operations. This preliminary protective action maintains production continuity without the periodic interruptions required by conventional approaches
Solution Approach 2:
The patent converts the harmful scale-forming process into a beneficial outcome by using scale-mitigating compositions that alter the deposition mechanism. Instead of forming hard, adherent scale that requires mechanical removal, the treatment produces softer deposits that are easily removed or prevented entirely, turning a production-disrupting phenomenon into a manageable condition
3Object-generated harmful factors
If scale is hard and adheres tenaciously, then scale formation occurs, but cleaning becomes difficult and resource-intensive
Solution Approach 1:
The patent changes the physical and chemical parameters of the scale deposits by applying scale-mitigating compositions. These compositions modify the deposition characteristics to produce softer, less adherent scales with different mechanical properties, transforming the cleaning task from a difficult mechanical operation to an easily performed maintenance activity
Solution Approach 2:
The scale-mitigating composition serves as an intermediary that modifies the interface between the phosphoric acid environment and the heat exchanger surfaces. It changes the nature of scale formation to produce deposits that are softer and more easily removed, thereby reducing the mechanical effort and resources required for cleaning
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 approach significantly reduces scale accumulation, extends the time between required cleanings, and facilitates easier removal, thereby increasing productivity and reducing the risk of equipment damage by producing softer, more tractable scales that can be easily washed or disintegrated.
Implementation Method 1
adding an aqueous scale-mitigating composition to a first phosphatic composition to form a second phosphatic composition; and contacting a scale-accumulating surface with the second phosphatic composition
Data Source
AI summary
Disclosed herein are compositions and methods of mitigating scale in phosphoric acid and ammonium phosphate plants. Scale-mitigating compositions of the invention can be added to phosphoric acid before or during the concentration in the evaporator cycle of a phosphoric acid plant. The compositions retard the formation of scale on surfaces in contact with the phosphoric acid, and thus time between cleaning is extended and plant productivity increased. Further, the scale that forms is softer and more easily cleaned from surfaces, reducing non-operation time of the plant and/or evaporator. Methods of mitigating scale formation in phosphoric acid production and phosphoric acid handling plants are disclosed. In the methods, scales accumulate more slowly and are softer, more tractable, and more easily cleaned from surfaces to which they adhere.