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atom12345
Post  Post subject: Fire Suppression System with A Chemical Reaction: Project  |  Posted: Sat Feb 04, 2017 2:10 am

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I'm a high school sophomore and my Chemistry teacher assigned me the following project:

I have to create a fire suppression system using baking soda (NaHCO3) and hydrochloric acid (HCL). I have to simulate a flammable facility, using a 15cm by 30cm by 10cm 3D cardboard structure. In this structure, I will have to have 8 "rooms", where a candle will be placed and lit. There is no roof or floor for the cardboard cutout. I have to develop an automatic fire suppression system that will be triggered by one or more candle flames. The trigger mechanism will cause the 1M HCl solution and the NaHCO3 to mix, ultimately producing CO2. I will also have to build a delivering system which will deliver the CO2 into the box to extinguish all 8 candles within one minute.

I also have to use Stoichiometry to calculate how much baking soda and hydrochloric acid I will need in order to produce a calculated amount of carbon dioxide.

I need help thinking of a system that will be able to do this (the triggering, the mixing, and the delivering system). This project is worth a hefty amount of points for my class. This is also my first post in this forum, so I'm really looking forward to your responses!

Thanks in advance!


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iNow
Post  Post subject: Re: Fire Suppression System with A Chemical Reaction: Projec  |  Posted: Sat Feb 04, 2017 2:54 am
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Well, you need a trigger. Something the candle flame will melt or cause to expand/open, and that trigger needs to release whatever you're using get to separate the chemicals while they're being stored... hence they mix and flow into the rooms.

My first thought involves a mesh of fishing lines strung together above the rooms in such a way that if any filament melts from the flame then the whole thing separates/falls and allows the chemicals to mix, but I bet a few of our other members have far better ideas.

We're not the busiest site, but the majority of folks who are here are great people with some high horsepower brains. Welcome to the community, and good luck!

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PhDemon
Post  Post subject: Re: Fire Suppression System with A Chemical Reaction: Projec  |  Posted: Mon Feb 06, 2017 1:05 am

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You could have a small dish of acid in the centre of your box. Empty a tea bag of tea leaves and use this as the container for your bicarbonate (it is light, will allow the acid to react with the bicarbonate and will prevent the powder spreading). Suspend the tea bag over the dish of acid (you could use a clamp stand outside of the box as a crane and use cotton thread from the tea bag over the arm of the stand, over where your candle flame would be and attach the other end to the wall of your box). When the candle is lit the flame will burn the thread dropping the tea bag into the acid producing CO2. As CO2 is heavier than air it will fill your box from the bottom up extinguishing the candles.

If you need help with the stoichiometry calculations let me know...

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PhDemon
Post  Post subject: Re: Fire Suppression System with A Chemical Reaction: Projec  |  Posted: Mon Feb 06, 2017 6:59 pm

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In the PM you sent me you say you can't have the acid in the box...

As a cunning plan you could have a conical flask stoppered with a bung and delivery tube outside the box. Now this is the cunning bit ;) Have the tea bag containing the NaHCO3 in the flask suspended above the acid, feed the cotton suspending it through the delivery tube and into the box over the candles. If the delivery tube is pointed into the box and you use enough of the reactants you will easily generate enough CO2 to fill the box in under a minute.

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iNow
Post  Post subject: Re: Fire Suppression System with A Chemical Reaction: Projec  |  Posted: Mon Feb 06, 2017 7:33 pm
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Thanks, PhDemon, for keeping the conversation open here so we can all learn from it. I understand the desire to use PM, but it seems too secretive for no good reason in this instance.

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PhDemon
Post  Post subject: Re: Fire Suppression System with A Chemical Reaction: Projec  |  Posted: Mon Feb 06, 2017 7:48 pm

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No problem, I don't like PMs... They seem to defeat the purpose of a discussion forum...

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Pong
Post  Post subject: Re: Fire Suppression System with A Chemical Reaction: Projec  |  Posted: Mon Feb 06, 2017 11:52 pm
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Seems this model need only be viable from a chemistry perspective. Architectural reality is thrown out the ceiling! For the sensor, that really bugs me - there's no sure way to catch rising heat or smoke unless you drape a canopy over the model. The candle will be placed in one of eight rooms, selected at random, right? The hotness and location of the flame is unknown. So the most ingenious trigger fails unless the flame is positioned where you need it.

Well, if the trigger can't function as in a real building (with ceilings), then I suggest a trigger that works just for this demonstration: Rather than tinker room-by-tiny-room, hang a funnel that acts as a chimney, over the entire box. Put an ordinary "hard-wired" (line voltage) heat or smoke detector above the funnel. You can borrow that from any legal dwelling. The detector will have an additional (red) com wire that energizes when fire is detected. This wire can power any old appliance(s) you like for mixing/delivering the suppressant. Like I dunno a coffee grinder, an aquarium pump, anythings.


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atom12345
Post  Post subject: Re: Fire Suppression System with A Chemical Reaction: Projec  |  Posted: Sat Feb 11, 2017 3:06 am

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Pong wrote:
Seems this model need only be viable from a chemistry perspective. Architectural reality is thrown out the ceiling! For the sensor, that really bugs me - there's no sure way to catch rising heat or smoke unless you drape a canopy over the model. The candle will be placed in one of eight rooms, selected at random, right? The hotness and location of the flame is unknown. So the most ingenious trigger fails unless the flame is positioned where you need it.

Well, if the trigger can't function as in a real building (with ceilings), then I suggest a trigger that works just for this demonstration: Rather than tinker room-by-tiny-room, hang a funnel that acts as a chimney, over the entire box. Put an ordinary "hard-wired" (line voltage) heat or smoke detector above the funnel. You can borrow that from any legal dwelling. The detector will have an additional (red) com wire that energizes when fire is detected. This wire can power any old appliance(s) you like for mixing/delivering the suppressant. Like I dunno a coffee grinder, an aquarium pump, anythings.


Sorry if I wasn't clear enough, but there are 8 candles in each of the 8 rooms in the model (so I have to extinguish all eight of them under one minute). I really liked PhDemon's approach to this problem:

PhDemon wrote:
In the PM you sent me you say you can't have the acid in the box...

As a cunning plan you could have a conical flask stoppered with a bung and delivery tube outside the box. Now this is the cunning bit ;) Have the tea bag containing the NaHCO3 in the flask suspended above the acid, feed the cotton suspending it through the delivery tube and into the box over the candles. If the delivery tube is pointed into the box and you use enough of the reactants you will easily generate enough CO2 to fill the box in under a minute.


I wasn't sure how to start working on my stoichiometry calculations. I feel like I would need to know how much CO2 I'll need to extinguish the flame to get started, but I'm not entirely sure. Ideas?
Also, sorry about using PM. As it was my first post on the forum, I really wasn't sure what to do when I received a response!! :)

Thanks for everyone's responses!


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PhDemon
Post  Post subject: Re: Fire Suppression System with A Chemical Reaction: Projec  |  Posted: Sat Feb 11, 2017 8:28 am

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No problem...

As for the stoichiometry problems you can assume you will need to make at least enough CO2 to fill your box. What is the volume of this box?
You may want to have a larger volume (the volume of the box will be a minimum requirement if you want all the flames out)
You now have a volume of gas, use the ideal gas law to calculate how many moles of gas this is.

Write down a (balanced!) chemical equation for the reaction of the acid with the bicarbonate. Use the stoichiometry (the numbers in front of each chemical formula) to deduce the number of moles of acid and bicarbonate you need to produce enough CO2.

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