1. The polar impurity substances of C4/C5 hydrocarbon from the RCC sweetening unit, such as nitriles and acetone, can be removed by the washing tower.
2. The water we supply to the washing tower is ultra-pure water, the UPW pH is 6~7. When the UPW wash the C4/C5 hydrocarbon, the UPW pH is rise to 9~10.
3. The pH of the UPW we washed is 9.6, the substance of the UPW we analysis (as the table) cannot find the alkali matter.
Could someone kindly tell us, other substances we neglect, and some substance we should test again to sure the alkali matter of UPW washed, thanks.
Dear all, The RCC (Residue Catalytic Cracking) sweetening unit is a process within an oil refinery that removes sulfur-containing compounds, primarily hydrogen sulfide (H2S), from hydrocarbon streams produced by an RCC unit.
Concrete washwater, specifically from the washing of concrete mixing equipment, is typically
highly alkaline , with a pH value ranging from 11 to 12+ . Some sources even cite a pH as high as 12.9. This high pH is attributed to the presence of cement, which has a natural alkalinity.
Important Considerations:
This high pH is problematic for the environment and can harm aquatic life if discharged into water bodies.
Proper management systems are implemented to reduce the pollutants associated with this high pH washwater.
Treatment methods, such as using carbon dioxide, can be employed to neutralize the washwater and lower its pH to acceptable levels for discharge.
Ultra Pure Water when used to wash RCC ( I presume is Reinforced Concrete), the wash water will have a high pH of the high pH of the concrete itself (anywhere around 11-12). Soak RCC in UPW for an hour or so, and test the pH of the water. It will.have a very high pH because of the Calcium salts conained in the RCC.
This process appears to be related to the sweetening of C4/C5 hydrocarbons —likely in a refinery or petrochemical plant where the hydrocarbons are treated to remove impurities (such as nitriles and acetone) using a washing tower . The ultra-pure water (UPW) used to wash these hydrocarbons has a rising pH, which could indicate the removal of certain acidic or polar impurities, leading to an increase in pH.
Process Description:
Washing Tower in Hydrocarbon Sweetening : The washing tower is used to treat the C4/C5 hydrocarbons by washing them with UPW to remove polar impurities like nitriles and acetone . These impurities may react with water, causing the pH of the water to rise as the wash liquid interacts with acidic impurities.
pH Rise in UPW : The ultra-pure water (UPW) has an initial pH of 6-7, but after being used to wash the C4/C5 hydrocarbons, the pH rises to 9-10 . This suggests that some acidic impurities are being removed, which could lead to the formation of alkaline compounds in the UPW, raising the pH.
pH of 9.6 : After washing, the UPW pH is 9.6 , but the analysis does not show any alkali substances (such as hydroxides or carbonates). The lack of alkali matter in the UPW suggests that the alkali is likely in the form of less easily detectable species or may be bound to other compounds.
Possible Missing Substances to Test:
Given the pH rise and absence of typical alkali substances, here are a few potential substances to consider testing :
Amines : Some impurities may involve amine compounds that could raise the pH but may not show up as typical alkali materials. Amine-based compounds are commonly found in hydrocarbon sweetening processes.
Organic Acids or Anions : The hydrocarbon impurities could also include organic acids (such as acetic acid or formic acid), which could neutralize and form salts or other species that contribute to the pH change.
Aldehydes/Ketones : Acetone and other ketones could potentially react with the UPW and may influence the pH but may not necessarily appear as simple alkali substances.
Ammonium Compounds : The presence of nitriles may lead to the formation of ammonium salts or similar nitrogen-containing compounds, which could contribute to the pH increase.
Buffering Agents : If any buffering agents are used in the sweetening process, they may also raise the pH without showing typical alkali compounds.
Testing Recommendations:
Amines (such as methylamine, diethylamine) should be tested, as they can influence pH.
Acidic compounds , especially organic acids , might also be a source of the pH rise.
Ammonium ions (NH₄⁺) could also be tested as a byproduct of nitrile washing.
Consider looking for complexing agents (e.g., chelating agents) that may bind alkali ions in a less detectable form.
By testing for these potential impurities, you can better determine the source of the pH change and confirm whether alkali matter is indeed present in a different form.
This process is likely part of a hydrocarbon purification or sweetening process in the petrochemical or refining industry , where removing impurities from the C4/C5 fraction is crucial to ensure the quality of the final product.
