The Mechanism of Barium Sulfate Deposition Inhibition and the Prediction of Inhibitor Dosage

Abstract

Scale inhibitors are widely used to prevent mineral scale deposition and precipitation in industrial processes. In this study, the performance of scale inhibitors is systematically investigated in a flow loop apparatus, designed to mimic the barite deposition in pipelines. The inhibitors are tested in tubing with and without a precovered barite scale layer. DTPMP (diethylenetriamine-pentamethylene phosphonic acid), PPCA (phosphinopoly carboxylic acid), and SPCA (sulfonated poly­(carboxylic acid)) are the main inhibitors tested in this work. The heterogeneous deposition rate constants at 120 °C in a clean tubing in the presence of 0.25 ppm of DTPMP/PPCA/SPCA are 0.00, 10.3 × 10–5, and 32.1 × 10–5 cm/s, respectively. The deposition rate constants at 120 °C in a tubing fully covered with barite in the presence of 2.0 ppm of DTPMP, PPCA, or SPCA are 5.97 × 10–5, 36.8 × 10–5, and 28.0 × 10–5 cm/s, respectively. In tubing fully covered with barite, all three inhibitors require a higher concentration to reach the same level of inhibition as observed in the uncoated tubing. The experiments in fully covered tubing were conducted in a wide temperature range (50–150 °C) with various dosages of inhibitors (0.02–40 ppm). The impact of inhibitors on deposition rate constants is modeled with a Langmuir-type equation by using an adsorption equilibrium constant K eq, fractional occupancy θ, and unoccupiable fraction θ0 in the fully covered tubing. θ represents the fraction of active sites occupied by the inhibitors, and θ0 represents the fraction that cannot be occupied by the inhibitors. The adsorption isosteric enthalpies of functional groups on the inhibitor molecules are calculated from the fitted associate equilibrium constants. A kink site adsorption mechanism has been proposed as the inhibition mechanism.

Density-Functional Theory Investigation of Barite Scale Inhibition Using Phosphonate and Carboxyl-Based Inhibitors

“…Furthermore, an experimental study has analyzed the mechanism of barium sulfate deposition inhibition for multiscale inhibitors. 23 This experimental study on barite scale inhibition showed that DETPMP inhibitor has a very high efficiency compared to other classical inhibitors such as phosphinopoly carboxylic acid and sulfonated poly(carboxylic acid), which supports the findings of this theoretical investigation. 23 DETPMP is a classical inhibitor that used a lot for scale inhibition, and it is experimentally proven that it has an excellent performance in inhibiting barite scale.…”

“… 23 This experimental study on barite scale inhibition showed that DETPMP inhibitor has a very high efficiency compared to other classical inhibitors such as phosphinopoly carboxylic acid and sulfonated poly(carboxylic acid), which supports the findings of this theoretical investigation. 23 DETPMP is a classical inhibitor that used a lot for scale inhibition, and it is experimentally proven that it has an excellent performance in inhibiting barite scale. 20 , 21 , 29 Moreover, the theoretical studies provide insights into why DETPMP has a superior performance compared to the other two inhibitors, PASP and NTMP.…”

“…Nevertheless, it corroborates the adsorption energy and further confirms why DETMPM has the strongest adsorption among the three, which agrees with experimental observations. 23 The top view of the inhibitors on the barite scale indicates that DETPMP covers more surface area on the barite scale compared to the other two inhibitors, thereby contributing to why it has the highest adsorption energy among the three inhibitors.…”

Fluorescent‐tagged Antiscalants: A New Look at the Scale Inhibition Mechanism and Antiscalant Selection

“…An antiscalant evidently retarded gypsum deposition from supersaturated aqueous solution, obtained by mixing calcium and sulfate brines at ambient temperature. But contrary to popular view, [3,5–9,14] that an antiscalant interacts with the gypsum nuclei, “shielding” them from calcium and sulfate ions sorption, no any interaction of HEDP‐F and CaSO 4 ⋅ 2H 2 O crystals was fixed, Figure 2a. The typical colorless stick‐like gypsum crystals grew up on their own, while HEDP‐F formed its own separate solid phase as calcium salt Ca‐HEDP‐F (blue spherical particles), Figure 2b, c. Some Ca‐HEDP‐F particles, detected on gypsum crystals surfaces, are likely to reflect a coalescence of both phases.…”

“…A widely used solution for controlling scale deposition is an application of chemical inhibitors: polycarboxylates, phosphonates, some natural “green” additives [2] . However, irrespective of an enduring and successful antiscalant application, the mechanisms of calcium carbonate and gypsum scale inhibition still remain the matter of discussion [3–10] . At the same time, an intensive work has been performed recently worldwide in order to obtain new, more efficient scale inhibitors [11] .…”