I would like to regenerate activated carbon, instead of destroying it, with the aim of optimizing my investment and reducing costs. I have inquired about current methods and have read about two processes:
Thermal regeneration: with pyrolysis, the organic compounds absorbed in the carbon can be destroyed. But this method requires significant investment (purchase of high-temperature ovens) and a loss of 7 to 10% of the carbon.
Chemical regeneration: a solvent is injected at 100 °C and a pH in the range of 12 to 13. This method would allow me to reduce carbon loss to 1%.
However I have not found additional information on chemical regeneration and how it is used in practice. Could someone advise me as to the best technique?
Maybe you can clarify the context of your request: what kind of activated carbon do you use and how?
I use GAC in a ZLD (zero liquid discharge) facility. The water coming into the facility is from an industrial paint company. It undergoes different treatment stages:
- GAC filtration
- softening agent
- reverse osmosis
- evaporation via thermo-compressor
- water demineralization
That's the entire process. The goal of this project is to optimize treatment costs. It is in that context that the idea of regenerating the activated carbon emerged. We would like to evaluate the potential to regenerate in-house. Our consumption is 18 t per year.
I forgot to mention that the purpose of the GAC is to absorb refractory COD that resists the physico-chemical and biological treatment.
The activated carbon is coconut-based and is in polyester tanks. I am leaning towards the chemical solution, but need more information. Specifically, I would like to find a way to regenerate the carbon outside the tanks, because of the high temperature of the water used (between 100 and 180 °C). Our facility is equipped with a biomass boiler that produces water heated to 230 °C. That is why I have the chemical solution in mind. But, I cannot figure out how to design a regeneration system outside the tanks and whether I should us NaOH + hot water.
Thanks for any advice or answers!
If you use chemical regeneration, don't forget that you will have to get rid of the chemical after those regeneration and it can be costly in some case. Sometimes you have to use specialized companies to destroy your reject. Just don't forget to evaluate the cost of it.
Makes no sense to regenerate the GAC by yourself just for as little as 18 t/year. This is absolutely nothing in terms of volume.
Companies such as Norit, Donau Carbon, Chemviron have specialized thermal treatment units in order to treat GAC where they treat thousands of tons efficiently per year.
Furthermore, you need to assure the quality and reproducibility of your regenerated GAC. This is very tricky. After your "own" treatment it might well be that your GAC won't show anymore the previous adsorption capacities.
In general I always recommed to use GAC on service based contract, i.e. the GAC provider provides the absorption units on a rental base and GAC is replaced as needed. No CAPEX only OPEX. Much more comfortable for the industry.