Assuming that gas line was coming out of the Puxin scrubber it may be sulfur as well as iron oxide. Iron oxide is desirable in the scrubber system because the Hydrogen Sulphide that you are trying to remove reacts with that and not the raw iron. The reaction is H2S + FeO2 -> FeS + H20 So the Hydrogen Sulphide reacts with the rust on the iron balls and produces iron sulphide and water. The water generates more iron oxide (rust) creating more reactive surface area for the Hydrogen sulphide. This is also an endothermic reaction and works most effectively above 20ºC However, iron Sulphide reacts with oxygen and turns back to iron Oxide + sulfur (FeS +1/2O2 -> FeO + S) So you get rust and sulfur produced which is probably what you can see in the tube. So the appearance of rust is not an issue and supports the scrubbers chemistry. What you may find is that the rust inside the Puxin scrubber has bonded the balls together and reduced its overall surface area. you might be able to alleviate this issue by smashing the container on the floor a few times to break apart all the rusted together balls. Also because the iron sulphide reaction is exothermic a large scrubber that has not been purged for a while could spontaneously ignite or at least get very hot when opened to the air. It's possible that enough oxygen is coming from the biogas to prevent saturation of the scrubber with iron sulphide. Because the steel wool in the new scrubber has a much greater surface area its possible that all of the steel wool structure will corrode to iron oxide powder and bond together into a solid lump in the new scrubber making it less effective over time. I guess thats why the Puxin uses steel balls to mitigate the iron oxide gluing everything together. Ideally you want to get a gas analyser that can detect low levels of Hydrogen sulphide and measure the raw gas and scrubbed gas to see how effective the scrubbers really are. www.sciencedirect.com/topics/engineering/iron-sponge-process#:~:text=H2S%20reacts%20with,form%20iron%20sulfide%20and%20water.
Assuming that gas line was coming out of the Puxin scrubber it may be sulfur as well as iron oxide. Iron oxide is desirable in the scrubber system because the Hydrogen Sulphide that you are trying to remove reacts with that and not the raw iron.
The reaction is H2S + FeO2 -> FeS + H20 So the Hydrogen Sulphide reacts with the rust on the iron balls and produces iron sulphide and water. The water generates more iron oxide (rust) creating more reactive surface area for the Hydrogen sulphide. This is also an endothermic reaction and works most effectively above 20ºC
However, iron Sulphide reacts with oxygen and turns back to iron Oxide + sulfur (FeS +1/2O2 -> FeO + S) So you get rust and sulfur produced which is probably what you can see in the tube. So the appearance of rust is not an issue and supports the scrubbers chemistry.
What you may find is that the rust inside the Puxin scrubber has bonded the balls together and reduced its overall surface area. you might be able to alleviate this issue by smashing the container on the floor a few times to break apart all the rusted together balls.
Also because the iron sulphide reaction is exothermic a large scrubber that has not been purged for a while could spontaneously ignite or at least get very hot when opened to the air. It's possible that enough oxygen is coming from the biogas to prevent saturation of the scrubber with iron sulphide.
Because the steel wool in the new scrubber has a much greater surface area its possible that all of the steel wool structure will corrode to iron oxide powder and bond together into a solid lump in the new scrubber making it less effective over time. I guess thats why the Puxin uses steel balls to mitigate the iron oxide gluing everything together.
Ideally you want to get a gas analyser that can detect low levels of Hydrogen sulphide and measure the raw gas and scrubbed gas to see how effective the scrubbers really are.
www.sciencedirect.com/topics/engineering/iron-sponge-process#:~:text=H2S%20reacts%20with,form%20iron%20sulfide%20and%20water.
Keep up the good work and best wishes for the future. Keep up the good work
Good explanation 👏 😊😊
looks good. is there a noticeable difference? does the gas look and smell different with this on? Is rust the biggest concern with dirty biogas?
Thanks