Modify particle source terms in PeleLMeX

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Hi, I am learning PeleLMeX and trying to use it to calculate issues related to the combustion of metal particles. Therefore, I need to add some code such as melting and heterogeneous surface reactions (HSR) during the particle combustion process. Where is the most appropriate place to add this part of the code？

In addition, for the gas-phase reaction mechanism of metal combustion, which solver is more suitable for solving such gas-phase reactions due to its strong rigidity? I am attaching my reaction mechanism document here.
mechanism.zip

Thank you. Waiting for your response.