Scale and Corrosion Prevention in Cooling Water Systems Part II: Calcium Sulphate
This paper describes an experimental study on calcium sulphate scaling and prevention by newly treated poly- acrylamide in a laboratory model. In order to study the inhibiting capacity of the chemical used, experiments were per- formed in solutions involving treatment of synthetic sea water with different concentrations of the polymer. Polyacryla- mide gave significantly lower precipitation rate compared to the treatment in absence of inhibitor. The inhibitor probably is adsorbed on the active growth sites of the initially formed crystals. The performances of scale inhibitor with different concentrations were analyzed in terms of the amount of soluble calcium ions in solution. The results showed that the amount of scale was reduced to 0.00%, with, 10-15 ppm polymer additions, after 1 day incubation at 90°C. Antiscale agents specific to calcium sulphate deposits have recently been developed and tested on a laboratory scale. The work was also extended to study the corrosion inhibition of polyacrylamide to both C-steel and copper specimens in contact with synthetic cooling water environment. Electrochemical polarization techniques reveal that the inhibitor acts as anodic type with respect to C-steel and mixed type for copper. Corrosion current jcorr and corrosion rate CR were reduced and inhibi- tion efficiency IE% increases with polymer additions. The inhibition effects are due to the formation of protective film. Morphological investigation for CaSO4. 2H2O gypsum crystals formed in synthetic sea water indicate reduction of cal- cium sulphate crystals in the presence of the polymer as indicated by scanning electron microscopic (SEM) studies.
Progressing the understanding of chemical inhibition of mineral scale by green inhibitors
Abstract Reducing the formation of inorganic deposits in processing industrial waters presents a challenge for desalination systems. Our topic of research progresses the understanding of scaling phenomena in seawater and the effects of green inhibitors. In order to understand the processes occurring at the liquid–surface interface, a procedure has been developed to follow in situ and in real-time the growth of scale particles in the micrometer size range and to quantify the effects of inhibitor on the crystal evolution. Experiments were carried out with a green additive, polymaleic acid, at a concentration of 1 and 4 ppm and with PPCA (commercial phosphonate inhibitor) used as inhibitor reference. On the one hand, results showed that polymaleic acid reduces the formation of scale by acting on the nucleation and growth process namely at a concentration of 4 ppm. In this paper a comprehensive description of the inhibitor/surface interactions will be presented. The role of the green additive in affecting the interface will be discussed in relation to the principal mechanisms by which the inhibitors function.
17 &mgr;m pixel 640 x 480 microbolometer FPA development at BAE Systems
BAE Systems has developed an advanced 640 x 480 focal plane array (FPA) with a 17 &mgr;m pixel pitch. Sensitivity of ≤ 50 mK was demonstrated and the FPAs were used in imaging demonstrations. Successful scaling of BAE Systems' patented single contact per pixel, single-level microbolometer process to 17 &mgr;m pitch provides a path toward next generation microbolometer imaging systems.