Discussion Overview
The discussion centers around the corrosion issues associated with using caustic (sodium hydroxide) as a heating and cooling medium in reactors, particularly in the context of PVC production. Participants explore methods to minimize corrosion in carbon steel (CS) pipelines and reactors, considering alternative additives and their effects on system performance.
Discussion Character
- Technical explanation
- Debate/contested
- Experimental/applied
Main Points Raised
- One participant seeks advice on preventing or minimizing corrosion in carbon steel reactors using caustic as a heating/cooling medium.
- Another suggests adding sodium carbonate to create a passivating iron carbonate coating, questioning the choice of caustic as a heat transfer fluid.
- A participant explains the use of caustic in the PVC process, noting the exothermic reaction and the observed corrosion near bends in the pipeline, expressing concern about the corrosive nature of hot caustic at 12-15% concentration.
- One reply states that calcium carbonate is not suitable due to its low solubility in sodium hydroxide and suggests that galvanic corrosion may be occurring near bends or welds. They propose increasing carbonate levels or considering a complete replacement of sodium hydroxide with carbonate.
- A participant inquires about testing the temperature capabilities of calcium carbonate and sodium carbonate at 110°C, expressing concerns about potential deposition in the reactor and seeking suggestions for experimental methods to assess both temperature increase and corrosion.
Areas of Agreement / Disagreement
Participants express differing views on the effectiveness of calcium carbonate as a solution and the best approach to mitigate corrosion. There is no consensus on the optimal method to address the corrosion problem, and the discussion remains unresolved regarding the best additives and testing methods.
Contextual Notes
Participants mention specific conditions such as the concentration of caustic and the temperatures involved, but the implications of these factors on corrosion and heat transfer remain unclear. The discussion includes assumptions about the behavior of additives in the caustic solution that are not fully explored.