Message for kenvlach - Re: Hindering CaO+ Water rxn 1

[bbqnw12]

Hello.

You're just so helpful, I think I'm going to just stick with forwarding my queries straight to you! Thanks a lot.

I just have one thing to ask: You proposed using nitrogen gas. However, we feel it's too cold, especially as the solid is being used in a reaction to produce heat in situ in the first place. We were thinking along the lines of using a hydrocarbon alkane, around the region of C6 - C10. This way, the hydrocarbon can be heated to our desired temperature before it is mixed with the CaO and injected
into the required site of reaction with water.

I think I may have worded the question wrongly before, as I meant to ask for a suitable medium to handle CaO in order to facilitate transportation in a pipe before it (hopefully) reacts on meeting with a water body. Purely speculative, as it is worryingly possible for the hydrocarbon to form a layer preventing the water from reacting with the solid.

Please give me any help and suggestions you can. Thanks a lot.

bbqnw12 (Chemical) Jul 28, 2003
Hello People!

Please, I need help with this: Which solvent can be used to handle CaO in order to prevent it from reacting with water? I think it is some sort of oil, but I am not too sure. Please bear in mind that this is to be used on a large scale and so it would help if it were rather cheap.

Thank you very much in advance.


kenvlach (Materials) Jul 29, 2003
1) Don't use oil, you will end up with a messy slurry.
2) Don't use any organic acid or alcohol or anything else with an OH; CaO will react to form Ca(OH)2.
3) Don't use anything with F; it will form CaF2.
4) Don't use anything with SO2, SO3, etc.
5) Don't use CO2 gas.
6) Suggest using dry N2 gas.

 

[kenvlach]

OK, let me see if I understand the setup.
The alkane liquid will preheat and transport the CaO through a pipe to a reactor where it mixes with water and creates heat. I presume the heated alkane will be floated off the water and recycled back.

I still don’t understand how you will use the heat, and have some concerns about temperature and flammability.
What is your initial alkane + CaO temperature?
Why do you want to use preheat? Or is this something that will naturally happen once the alkane gets heated in the reactor?
What is the calculated temperature rise from the CaO + H₂O reaction (depends upon quantity of water and your inert liquid)?
Will you purge your vessel with N₂ to prevent igniting the alkane?

The vapor pressure of C₆H₁₄ may be too high for your temperatures; maybe use C₁₀H₂₂.

 

[kenvlach]

Still seems rather dangerous, feeding gasoline into a hot reactor.

Consider an alternative, like using a conveyor belt within an enclosure to a hopper above the reactor, with a one-way flapper valve at the bottom of the hopper. Pressure within the reactor could be a problem. It is possible to have a double trapdoor system, at top and bottom of the hopper, with the top closing to allow pressurizing with N₂, to allow discharge through the bottom. It works for blast furnaces, but maybe too complex, and batch feeding is probably not as good as continuous for this application.

There is probably a better means of feeding a powdered solid into a pressure vessel, such as a screw auger. If this seems reasonable, I suggest posting a question under Mechanical Engineering -- Other topics.