The present work is addressed primarily to the study of the effects of glycol aging at elevated temperatures (above 100/sup 0/C). Glycols are known to be susceptible to thermal decomposition producing new product species which may be aggressive to aluminum. In addition, the possible breakdown of corrosion inhibitors due to long term exposure to high temperature are also investigated. Both uninhibited and inhibited ethylene (as well as propylene) glycols have been aged at temperatures up to 190/sup 0/C for over 2000 h continuously to date. Aliquot samples of each glycol solution tested in this program were taken at 1000 and 2000 h of exposure for chemical analysis and pH measurement. Based on the data obtained so far, solution pH was found to decrease steadily with exposure time. The critical pitting potential of 1100 series aluminum in a 50 vol % aqueous ethylene glycol solution is reported as functions of both temperature and chloride ion concentration. This information is essential in the cathodic protection of pitting corrosion of aluminum.
Abstract Aluminum and its alloys are highly susceptible to pitting corrosion in aqueous glycol solutions, especially when chloride and heavy metal ions (Cu+2 and Fe+3) are present. One approach to controlling such corrosion is the use of scavengers to remove the deleterious species from solution, and in this work the role of zinc as an effective heavy metal ion scavenger has been confirmed. In addition, it was discovered that zinc powder in suspension is capable of stopping aluminum pitting corrosion in aqueous glycol solutions containing chloride ions. Zinc is not expected to act as a chloride ion getter. However, it has been established that zinc also gives a protective effect through a cathodic protection mechanism produced by the zinc powder contacting the aluminum surface and concomitantly lowering the open circuit potential of the aluminum sample to below its critical pitting potential. A similar cathodic effect is expected also, of course, in the case of heavy metal ion contamination when simultane...
DocuSign is advancing at a great pace for artificial intelligence and embracing a continuous shift towards developing and deploying an increasing number of deep learning models. During the development stage, developers usually build a number of deep learning models and train them using a bunch of potential hyperparameter configurations to find the best-performed one, which is called hyperparameter optimization (HPO). Such HPO jobs can run for a long time due to ever-larger models and numerous hyperparameter configurations. Furthermore, the HPO jobs at DocuSign are processed in container-based environments so that the best-performed model can be deployed and maintained in production reliably and efficiently.
The development of corrosion control methods for aluminum solar collectors using ethylene glycol heat transfer fluids was studied. Corrosion inhibitors and impurity scavengers have been tested and evaluated at temperatures up to 160 C under various laboratory conditions. A new corrosion rate measurement technique based on the use of thin foil samples was developed and adopted in this program to provide accelerated results. In addition to the development of corrosion control methods, the acquisition of baseline corrosion data was also extended to the aluminum/propylene glycol combination. Propylene glycol was chosen primarily because of its low toxicity. Aluminum corrosion characteristics were determined in 50, 85 and 100% propylene glycol solutions at temperatures between 25 to 160 C. Corrosion behavior of aluminum in more concentrated ethylene glycol solutions (up to 100%) at higher temperatures (up to 160 C) was also obtained in order to broaden the baseline. The cube root pit growth law was also verified experimentally. All the parameters needed to predict the time to plant failure due to pitting perforation were also determined. With regard to the aluminum/propylene glycol combination, aluminum alloys were found to be about ten times more corrosion resistant in propylene glycol than in ethylene glycol solutions under similar conditions. An extensive literature review showedthat phosphates, borates, nitrates and silicates and sodium mercaptobenzothiazole are effective corrosion inhibitors which are compatible with glycol solutions. It was determined that most inhibitor formulas, whether proprietary or prepared in-house, can reduce the overall aluminum corrosion rate to below 1 mpy at temperatures below 100 C.
The structure functions for liquid ethane at (1) T = 105 K and a molecular density ρ = 0.012 70 Å−3, and (2) T = 181 K and ρ = 0.011 10 Å−3 have been derived from new x-ray diffraction data. Treating the –CH3 group as a single scattering site, carbon–carbon (methyl–methyl) intermolecular pair distribution functions have been obtained from the structure function data by Fourier inversion. Using Monte Carlo simulation, no two-site exponential-6 interaction model, with sites at the observed C–C bond length, could be found which reproduce the carbon–carbon distribution function. By considering a different class of interactions models, a model was found which reproduced the distribution function derived from experiment and accurately predicts the second virial coefficient of ethane.
In this study, plantwide control of an absorption/stripping CO 2 capture process using mono-ethanolamine was investigated using dynamic simulation. In this system, CO 2 removal ratio is influenced by operating variables such as lean solvent rate and lean solvent loading, which is in-turn determined by reboiler duty in the stripper. Moreover, we found that the long term stability of the system cannot be achieved unless the water balance is properly maintained. Hence the following control structure was proposed. In this scheme, CO 2 removal target is guaranteed using the lean solvent feed rate to the top of the absorber column. The overall water inventory was maintained by controlling liquid level in reboiler of the stripping column using makeup water. In order to operate process with an appropriate lean solvent loading, the temperature at the bottom of stripper is controlled by reboiler duty. This control structure was tested by disturbances involving inlet flue gas flow, and CO 2 concentrations. Dynamic simulations showed that system can achieve removal targets, stabilize quickly while keeping optimum lean loading constant. To ensure minimum energy consumption, optimizing control can be carried out by adjusting the setpoint of reboiler temperature.
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