# Diffusion of particles in batch reactors

• pippobaudo
In summary, Dino is seeking help in calculating the concentration of saturation for solid particles in a batch still tank reactor. The solid particles are likely limestone and react with hydrochloric acid, releasing Ca++ ions. Dino has tried using the solubility product, but the calculated value is too small. The mathematical model requires a positive difference between the saturation concentration and the concentration at a given time, but Dino is unsure of what saturation concentration to use. They are wondering if considering the total moles of samples dissolved is a viable option.
pippobaudo
Hello everybody, I don't know if this is the right place to post this question. Sorry for that.

I have the following system: small particles (I don't know exactly the composition) in a batch stilled tank reactor in which i add some hydrochloric acid.
How I evaluate the concentration of saturation of those particles into the bulk?
I am able to calculate the loss in volume vs time considering the total volume.
I practice if we consider the solid particles as "A" and "Ca" the concentration of A, then I want to evaluate [Ca(saturation)-Ca(at a time t)] i am able to calculate Ca(at a time t) but i am not sure about Ca(saturation).
I was thinking to consider Ca(saturation) as the concentration of all A dissolved into the bulk but I am not sure about it.

Thanks very much, you can also write me at: dinodeblasio@yahoo.it

Have you tried using the value of the solubility product of the ion A in water, to calculate the saturation concentration?

Also, what is the HCl supposed to do? Does it react with the solid particles, or with whatever diffuses out from the solid?

Last edited:
diffusion of solid particles

Hello and thank you for answering,
my solid is suppose to be some kind of limestone CaCO3, it reacts with HCl and releases Ca++ ions. In literature there are data on the concentration of saturation of Ca++ in water, but the value is too small because if i measure sperimentally the mass of solid lost and convert it to moles/liter, the moles of Ca++ should be much more. For this reason there is some other solid (impurities) that react with HCl or just dissolve into the water but in the mathematical model i don't know what concentration of saturation of Ca++ i should consider because in the mathematical model [Ca(saturation)-Ca(at time t)] must be positive.
Is that completely wrong to consider the saturation for that system as the total moles of samples dissolved? The amount of acid I put into the reactor should be sufficient to dissolve all the Ca++, HCl is in a bit excess.
Thanks again.
Dino

## 1. What is diffusion in batch reactors?

Diffusion in batch reactors refers to the movement of particles from areas of higher concentration to areas of lower concentration. In a batch reactor, the concentration of particles changes over time as the reaction progresses, causing diffusion to occur.

## 2. How does the diffusion of particles affect the reaction in a batch reactor?

The diffusion of particles plays a crucial role in determining the rate of reaction in a batch reactor. As particles diffuse, they bring reactants together, allowing them to react and form products. Without diffusion, the reaction would proceed at a much slower rate.

## 3. What factors influence the rate of diffusion in batch reactors?

The rate of diffusion in batch reactors is influenced by several factors, including the concentration gradient, temperature, and the size and shape of the particles. A larger concentration gradient, higher temperature, and smaller particle size all lead to faster diffusion.

## 4. How can the diffusion of particles be controlled in batch reactors?

The diffusion of particles can be controlled in batch reactors by adjusting the mixing rate, temperature, and the size and shape of the reactor vessel. These factors can be optimized to ensure efficient diffusion and lead to a faster reaction rate.

## 5. How is the diffusion coefficient calculated in batch reactors?

The diffusion coefficient in batch reactors can be calculated using Fick's second law of diffusion, which relates the diffusion flux to the concentration gradient and the diffusion coefficient. It can also be experimentally determined by measuring the rate of diffusion under different conditions and using the resulting data to calculate the diffusion coefficient.

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