Hydrogen production decarbonization solution
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Our hydrogen production plant uses a potassium carbonate-based decarburization solution as its purification system; potassium carbonate serves as the absorbent, diethanolamine as the accelerator, and vanadium pentoxide as the corrosion inhibitor. The reason why the solution becomes dirty after a certain period of time (several months) is that this leads to fluid accumulation, and in severe cases, it causes significant fluctuations in the two towers, with the semi-poor liquid pump often running dry. Previously, our solution did not contain diethanolamine; instead, aminoacetic acid was used as a catalyst. At that time, there were never any issues such as liquid buildup. What is causing the solution to become dirty? Seeking advice from experts
Reply 1# sadpan: What is the coating inside your alkali storage tanks? The fundamental cause of the solution becoming dirty is the peeling of the protective layer in the alkali storage tank; solid particles mixed with the solution, along with bubbling, lead to impact wear. This may be caused by poor construction quality or boiling occurring when the solution is heated in winter, which results in the corrosion and peeling of the coating. Generally, the composition of the phenol solution in decarbonization systems is: 27% K2CO3 + 3% DEA (diethanolamine). To prevent complete corrosion of the K2CO3 solution, a corrosion inhibitor of V2O5 is added to the solution, thereby forming a dense black-brown protective film on the surface of carbon steel with a thickness of less than 100 Å. At 90–100 °C, the corrosion rate of carbon steel in the phenanthroline solution was 0.307 mm/year before the addition of vanadium; however, after the addition of vanadium, this rate dropped to 0.051 mm/year. This is because the oxidation of V5+ in the solution resulted in the formation of a γ-Fe2O3 protective film, which reduced the corrosion current of carbon steel and thereby slowed down its corrosion. Therefore, it is recommended that you repair the coating layer in the alkali storage tank once again by using reinforced epoxy putty combined with glass cloth to strengthen the coating and improve its resistance to bumping corrosion. In addition, the following points should also be taken into consideration: 1—It is essential to strictly control the quality of the phenol solution: improve the filtration of the potassium alkali solution to reduce wear caused by mechanical impurities, and replace the crushed activated carbon and ceramic balls in the filter with fresh ones to ensure the quality standards of the filtered solution. 2—It is possible to consider re-passivating the purification system at an appropriate time: the solution is first left to stand in the two towers for 36 hours for static passivation, after which a circulation of lean solution and semi-lean solution is established to carry out dynamic passivation for 4–5 days. 3—Strictly control process parameters: Keep the concentration of the potassium carbonate solution below 10%, and control the temperature at the top of the regeneration tower