just a question, why do you want to evaporate the acid washes?
most of the salts of dmt are not solid, but rather sticky and oily (with the notable exception of dmt fumarate).
I doubt citric acid would deteriorate dmt citrate, but what might possibly happen, appart from a sticky product as mentioned above, is having some citric acid contamination in your final product.
So once again I ask for you to tell us why exactly are you doing this and then we can suggest an alternative solution