MATHEMATICAL INHIBITOR MODEL FOR BARIUM-SULFATE SCALE CONTROL

A semiempirical mathematical model has been developed to predict inhib itor efficiency for barium sulfate scale control in industrial process es. This model can be used for selecting effective inhibitors and dete rmining the minimal effective concentration needed for a given system. The model incorporates experimental data of the nucleation and inhibi tion kinetics. Specifically, the induction period in the presence and absence of scale inhibitors has been measured experimentally and input ted into the model: C-inh = (1/b) log[t(inh)/t(0)], where C-inh is the inhibitor concentration, t(inh) is the inhibition time (e.g., 20 min) , to is the nucleation induction period of the scaling mineral crystal , and b is the inhibitor efficiency. The inhibition kinetics of barium sulfate nucleation with is(hexamethylene)triaminepenta(methylenephosp honic acid) (BHMTPMP) and several other polyphosphonate and polyacryla te inhibitors have been measured. Many factors which are important to nucleation and inhibition kinetics, such as the degree of supersaturat ion, temperature, and solution pH, have been included in the inhibitor model. The model prediction for barium sulfate scale control was in g ood agreement with laboratory observations and field experience.