ODDA Process Lime Removal via Polyacrylamide Flocculation
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Solution Overview
Problem
The ODDA process for fertilizer production faces challenges in removing residual calcium carbonate (CaCO3) from the ammonium-nitrate containing liquid, which interferes with pH levels, heat exchange in evaporators, and granulation processes, and traditional methods like pressure filtration are costly and labor-intensive.
Innovation Solution
The use of an ultrahigh molecular weight anionic polyacrylamide flocculant, such as Magnafloc 919, is added in low concentrations to the sedimentation vessel to facilitate the complete precipitation of calcium carbonate, eliminating the need for pressure filtration and reducing maintenance costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pressure filtration is used to remove calcium carbonate, then CaCO3 removal efficiency is improved, but maintenance costs and process downtime increase
Solution Approach 1:
The harmful component (CaCO3) is extracted from the solution through enhanced sedimentation using flocculant, separating it from the ammonium nitrate solution without requiring complex filtration equipment that needs frequent maintenance
Solution Approach 2:
A flocculant is introduced as an intermediary substance to facilitate the aggregation and sedimentation of CaCO3 particles, enabling effective removal through simple sedimentation rather than complex pressure filtration
2Manufacturing precision
If pressure filtration is used to remove calcium carbonate, then CaCO3 removal efficiency is improved, but maintenance costs increase
Solution Approach 1:
The process replaces expensive, maintenance-intensive pressure filtration equipment with simple sedimentation vessels and inexpensive flocculant chemicals, accepting that the flocculant is consumed but eliminating equipment maintenance costs
Solution Approach 2:
The mechanical pressure filtration system is replaced with a chemical-facilitated sedimentation system, where chemical flocculation replaces mechanical filtration to achieve the same separation goal with lower maintenance requirements
3Reliability
If lime is present in the AN solution, then pH control is maintained, but heat exchange capability in evaporators deteriorates
Solution Approach 1:
The harmful effect of lime accumulation in evaporators is prevented by converting the lime into easily removable sediment through flocculation, allowing the lime to be beneficially separated before the evaporation stage rather than causing heat exchange problems
4Quantity of substance
If lime is present in the overflow liquid, then ammonium carbonate is available for conversion, but granulation process is negatively interfered with
Solution Approach 1:
The solution applies different treatment to different components: ammonium carbonate is preserved in solution for conversion reactions, while calcium carbonate is selectively flocculated and removed to protect the granulation process, achieving local quality differentiation in the treatment approach
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 achieves nearly complete removal of CaCO3 (up to 99.99%) without the need for pressure filtration, improving process efficiency and reducing downtime and costs by ensuring effective sedimentation and preventing blockages in evaporators.
Implementation Method 1
the addition of less than 5 ppm of an ultrahigh molecular weight anionic polyacrylamide as flocculant leads to an effective and complete removal of CaCO3
Implementation Method 2
The mixture is then cooled, in general to below 0 °C. The calcium nitrate crystallizes
Implementation Method 3
CaCO3 precipitates from the reaction mixture obtained by chemical equation 4 in the thickener
Data Source
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AI summary
The present invention is directed at an ODDA process with an improved lime removal for fertilizer production. In a preferred embodiment, the improved lime removal is obtained by the addition of an ultra-high molecular weight anionic polyacrylamide as flocculant.