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.
The Scale and Antiscale Study of the Reclaimed Water Reused in Industrial Recycling Cooling System
The reclaimed water of municipal sewage reused in industrial recycling cooling system is an effective approach to save water resource and improve the ecological environment. One of its critical factors is controlling scale formation in recycling cooling system. In this paper, the scale formation and antiscale influence factors of the reclaimed water reused in Beijing thermoelectric plant were investigated. The scale of the reclaimed water was measured by SEM, XRD and XRF techniques. Through the static and dynamic simulation test, we obtained an optimum composite antiscale. Furthermore, the effects of ion components，COD and turbidity of the reclaimed water on the scale inhibition efficiency were examined. This can provide a useful information basis for controlling and estimating risks of the reclaimed water reused in industrial recycling cooling system.
Compressive and flexural properties of hemp fiber reinforced concrete
The compressive and flexural properties of hemp fiber reinforced concretes (FRC) were examined in this paper. Natural hemp fiber was mixed using dry and wet mixing methods to fabricate the FRC. Mechanical properties of the FRC were investigated. The main factors affecting compressive and flexural properties of the FRC materials were evaluated with an orthogonal test design. Fiber content by weight has the largest effect. The method for casting hemp FRC has been optimised. Under the optimum conditions, compressive strength increased by 4 %, flexural strength increased by 9 %, flexural toughness increased by 144 %, and flexural toughness index increased by 214 %.