2. Simultaneous absorption of H2S and CO2 from gaseous streams into an aqueous MEA solution using a packed bed pilot-scale contactor has been studied theoretically and experimentally. As a first conclusion, the packing size affects the relative absorption (selectivity) of CO2 and H2S in MEA solution as a new proposed structural parameter.
Smaller packing size leads to decrease in selectivity of H2S absorption. The results also show that, increasing of total pressure, which helps the diffusion steps in absorption, increases the H2S absorption selectivity and rate. It also could be seen that increasing L/G as a potential for liquid phase events, decreases the H2S absorption selectivity while increases the absolute rate of absorption. It is the same, when amine concentration is increased. Increasing the amine concentration, L/G and decreasing the packing size conceptually means the increase in absorption potential per bed volume which decreases the selectivity.£¨15 points£©
3. Green Chemistry is the design, development, and implementation of chemical products and processes to reduce or eliminate the use and generation of substances hazardous to human health and the environment. Unlike regulatory requirements for pollution prevention, Green Chemistry is an innovative, non-regulatory, economically driven approach toward sustainability. Green Chemistry considers the entire life cycle of chemical processes as an opportunity for design innovation. Rather than regulatory restrictions for controlling hazards, Green Chemistry challenges innovators to design and
utilize matter and energy in a way that increases performance and value while protecting human health and the environment.£¨10points£©
4. Diffusivity of chromate was taken from the literature. To test the effect of suspended solids on the rate of diffusion controlled corrosion of the impeller, porcelain particles were used. Particle size ranged from 0.3 to 0.7 mm while particle concentration ranged from 1% to 3% by volume. In order to test the effect of drag reducing polymers on the rate of diffusion controlled corrosion of the impeller, polyethylene oxide (polyox WSR-301) a product of Union Carbide was used in the form of suspension at concentrations of 200, 200, 400 and 500 ppm. The solid polymer powder has a density of
1.15¡À1.26 g/cm3, particle size ranged from less than 38 mm to larger than 500 mm. The polymer was used as received and no attempt was made to separate different sizes. The chemical stability of the polymer in acidified chromate was tested in separate experiments by adding polyox to acidified chromate solution (blank) for 1 h after which chromate concentration was determined, no change in chromate concentration was found to take place, i.e polyox is chemically stable in the solutions used in the present study. Rheological measurements showed that all polymer containing solutions were Newtonian; polymer addition in the form of solid particles to the blank solution was found to have a negligible effect on the physical properties of the solutions. Table 1 shows the physical properties of the solutions.£¨20points£©
5. A common oxidative coupling reactor design has a fluidized bed, though many other designs are also being considered. In the reactor, methane (CH4) and oxygen react over a catalyst to form water and a methyl radical (CH3). This reaction is called partial oxidation of methane. The methyl radicals combine to form a higher alkane, mostly ethane (C2H6) which dehydrogenates into ethylene (C2H4). The function of the catalysts is to control the activity of oxygen ions so that reactions can be kept on the desired path. Complete oxidation (rapid formation of CO2 before the radicals link up to form ethane and ethylene) is an undesired reaction. The catalysts used are mostly oxides of alkali, alkaline earth and other rare earth metals. Hydrogen and steam are sometimes added to reduce coking on catalysts. After one pass, roughly 80% of the total oxygen feed by mass is consumed. Ideally, 100% is desired since oxygen is difficult to separate and can cause undesired combustion or even explosion. The per-pass ethylene yield on a mass basis of methane is about 30% due to low conversion and poor selectivity to ethylene. £¨15points£©
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