Regeneration of H3PO4 from KH2PO4,K2HPO4...

[tpower9s2003]

It appears that H3PO4 could be easily regenerated from K2HPO4 or KH2PO4 with HCl:
K2HPO4 + 2HCl<--->>H3PO4 + 2KCl
KH2PO4 + HCl<--->>H3PO4 + KCl
HCl is a stronger acid therefore seems that the equilibrium would favor H3PO4. Concentrating the H3PO4 if the HCl input was muriatic 33% could be done with annhydrous MgSO4 or atm/fractional distillation. If this works would mean a potential recycling from rxns where these are byproducts or use of clean sources of either/both these salts.

[Osmium]

You people need to grasp the concept of dissociation in aqueous solutions, equilibriums and solubilities, then these questions would stop.

If you pour HCl into an aqueous solution of K phosphates then you end up with a solution of H⁺ and K⁺ cations and all kinds of phosphate plus some Cl[sup-[/sup] anions. You cannot magically separate them and selectively remove one and only one component.
There is no H3PO4 in solution, and neither is there KCl in solution since these are dissociated. If KCl will precipitate and K_xH_yPO4 stay in solution or the other way round depends on solubility products.
The concept of stronger acids forcing the weaker acid to be protonated is an academical curiosity when both acids are strong, and I could give you several real world examples where the weaker acid is forcing the stronger acid out of the mixture, since other factors like solubility, boiling point etc. become important.

[tpower9s2003]

My bad, Shouldve been clearer that it would obviously be aqueous solution of ions. TP didn't mean to imply some magically easy isolation of pure H3PO4. Drying it some was simply means of concentrating the solution if the HCl was the more dilute OTC 33% OTC grades. From here on out the proven Argox method would go to HI. Hence recycled, yes? 

TP really shouldve asked "can someone verify that the equilibrium favors H3PO4 in real world situations?" Nobody likes finding out after the fact that theyre dead wrong.

H3PO4 is considered a weak acid by practically all academic sources that turn up. Its not like comparing two strong acids like HCl to H2SO4 (ala HCl gas generators)... it is significantly weaker. A little excess of HCl over molar amounts might be prudent.  
H3PO4: Ka1= 7.1 x10^-3
HCl: Ka= 1 x10^6
Solubility and BP is also unlikely to appreciably force out HCl or anything else necessary. Both are H20 miscible/soluble with HCl moreso, and so are those potassium salts. All MPs/BPs are all well above STP, FPs below, and there was no implication of active heating/freezing hence would be near to STP.

OK so the method wouldn't be super easy and surely not for know-nothings that are still wondering what went wrong with their 1hr curbshots...

[Osmium]

When you heat up that mixture HCl would escape. Great example how a weaker acid can liberate a stronger acid since it is less volatile.