Hydrate-based CO2 separation is a new technology by which the exhaust gas containing CO2 is exposed to water under high pressure forming hydrates. The mechanism is based on the differences of phase equilibrium. Gas hydrates are crystalline solids, in which low molecular weight guest molecules are trapped inside cages of hydrogen-bonded water molecule. A given hydrate structure is typically determined by the size and shape of the guest molecule. Carbon dioxide is known to form structure I. Each cavity may encapsulate one—or in rare cases more—guest molecules of proper sizes. It is the presence of the guest molecule that stabilizes the crystalline water structure at temperatures well above the normal freezing point. As a separation method, gas hydrates may be used with treated flue gas from power plants in which CO2 is separated from N2 and O2. …show more content…
CO2 is preferentially encaged into the hydrate crystal phase compared to the other components. For instance, the equilibrium pressure of N2 hydrate is three times greater than that of CO2. This difference allows to separate CO2 from treated flue gas, i.e. a CO2-N2 mixture [14].
Flue gas from power plants usually contains from 15% to 20% mol. of CO2 and are released at atmospheric pressure. The gas/hydrate equilibrium pressure for this kind of gas mixture is relatively high. For example, the equilibrium pressures for a gas mixture containing CO2 at 17.61% mol. are 7.6 MPa and 11.0 MPa at 274 K and 277 K, respectively [15]. These pressures are not compatible with the industrial reality, since the operative cost will be expensive if it is necessary to compress the gas to the hydrate formation pressure. Consequently, the main challenge is to obtain a decrease in the operating pressure. This task can be achieved using specific
To use the ideal gas law, the atmospheric pressure was adjusted for due to the lower pressure in the buret when compared to the outer atmospheric pressure. This unequalization of pressures, although corrected, may still be slightly off, thus potentially causing later calculation error when using the ideal gas law to solve for the moles of CO2.
CO2 is not really ideal. There are dispersion forces between the
Hydrates are combinations that are salts with water particles synthetically clung to them. Really, the holding is intriguing in that the water particles bond specifically to the metal cation. Hydrates fall in an expansive class called coordinated compounds in view of the sort
5.Position gas collecting hose so it runs from reaction vessel through gas collecting box to opening of the graduated cylinder. The idea is that any gas coming through the tube will rise in the graduated cylinder and displace the water in it.
Louis Zhou Yijun Zhang (G11B) Pre-AP Chemistry May 22, 2017 Lab: Collecting Gases Over Water 2KClO_3 (s) ∆/(MnO_2 ) 2KCl(s)+3O_2 (g) Objectives
The following laboratory experiment calls for a moderate understanding of what a hydrate is, what its properties are, and how altering a hydrate’s chemical structure may cause the release of both water and acidic vapors. A hydrate itself is a chemical, typically a crystalline salt, which incorporates water (H2O) into its chemical structure. For example, the compound CoCl2 is merely cobalt (II) chloride, however, take the original compound and attach a water molecule and it becomes CoCl2 + 6 H2O. In other words, the original cobalt (II) chloride is now cobalt (II) chloride hexahydrate.
For this experiment we analyze the percent water in a crystalline hydrate. By examining the percentage we then are able to identify the changes in compound and compare them to that of unknown possibilities. In order to identify what hydrate we’re experimenting with, it must first be weighted using an analytical balance and record its initial state. To begin the heating process, the hydrate is moved back and forth over a flame at a 45 degree angle in order to remove any water within the hydrate. Thus it becomes a anhydrous residue after heat is applied. In order to achieve a constant weight of 0.002g or less, the anhydrous needs to be heated several times in order to eliminate most of the water contained. By calculating the the initial and final stage of the hydrate, the percent water will be determined. Finally, by comparing the mass of water lost from the unknown hydrate, the compound can be referenced from a list of unknowns.
(Step 4 cont.) I combined baking soda and vinegar again and attached the stopper with copper and plastic tubing assembly. I added a few ml of limewater to a well of my well plate and ran the CO2 through the tube of the gas assembly through the limewater, which caused it to turn a cloudy color and possibly produce a precipitate. Using the same gas assembly technique, I ran the CO2 through a few ml bromothymol blue in the well plate as well. When the gas contacted the bromothymol, it turned from blue to yellow then to a murky green.
In this lab I found there are huge connects between volume and pressure. In the case of
Gas hydrates form clathrate structures consisting of hydrocarbon molecules within "cages" of water molecules. There are two clathrates of practical interest, the sI and sII structures. The sII structure can accommodate propane molecules, which is not possible for the smaller cages of the sI structure. Alternatively, the sII structure will not form in a gas mixture consisting only of the smaller methane molecules. For the complex mixture of hydrocarbons in natural gas, both sI and sII structures
Figure 3. Diagrammic representation of how the apparatus should be set up to heat the de-ionized water, in which carbon dioxide gas would be dissolved afterwards in a gas syringe, to a selected temperature with the aid of temperature measurement by thermometer
The coal seams are generally filled with water and it is the pressure of the water that keeps the gas as a thin film on the surface of the coal. A combination of water and ground pressure traps the gas in the fracture of the coal seam.
Gas hydrate and free gas are electrical insulators and their relative impact on water saturation (Sw) calculation is the same. The Archie equation (Archie, 1942) can be used to calculate gas hydrate (Sh) and free gas saturations (Sg) from resistivity log measurements (Collett & Ladd, 2000; Lee and Collett, 2009, 2012), but resistivity logs cannot distinguish the difference between gas hydrate and free gas. Archie equation includes the assumed resistivity of the baseline water-saturated (R0) sediment, the resistivity of the connate water (Rw), porosity (ϕ) and Archie constants a and m and can be expressed as follows: (1) The formation resistivity of the water-saturated sediments (R0) to the resistivity of the connate water (Rw) ratio is defined as the formation factor (FF). The resistivity of the connate water (Rw) can be calculated using Arp’s formula (Arp, 1953) with the salinity, the temperature and geothermal gradient obtained from core sample, LWD and temperature
The right hand region covers pressures and temperatures at which hydrates are thermodynamically unstable and is therefore ‘hydrate free’ as indicated. On the left hand, the temperatures and pressures favour hydrate formation. In the ‘hydrate region’, the degree of sub-cooling is sufficient enough to promote hydrate formation spontaneously. Gas hydrate forms in water phase from gas molecules dissolved in that phase. Consequently, H2S and CO2 increase the temperature at which hydrates will form since they are more soluble in water than most hydrocarbons.