Movement of gases

FIG. 25-71 Vents used to control tlie lateral movement of gases in landfills, (a) Cell, (h) Barrier, (c) Well. From G. Tchohanoglous, H. Theisen, and R. Eliassen, Solid Wastes Engineering Principles and Management Issues, McGraw-Hill, New Yor k, 1977. )... 

Control of ga.s movement by recovery. The movement of gases in landfills can also be controlled by instadhng gas-recovery wells in completed landfills (see Fig. 25-74b). This is considered an active venting system. Clay and other hners are used when landfill gas is to be recovered. In some gas-recovery systems, leachate is collected and recycled to the top of the landfill and reinjected through perforated lines located in drainage trenches. Typically, the rate of gas production is greater in leachate-recirculation systems. 

Solid-wa.ste-filling plan. The specific method of filling will depend on the characteristics of the site, such as the amount of available cover material, the topography, and local hydrology and geology. To assess future development plans, it will be necessary to prepare a detailed plan for the layout of the individual solid-waste cells. On the basis of the characteristics of the site or the method of operation (e.g., gas recovery), it may be necessaiy to incorporate special features for the control of the movement of gases and leachate from the landfill. 

The movement of gases and vapors is more difficult to visualize than that of particulates. However, most gases and vapors have strong absorption peaks in the infrared band. If a flat screen, heated to some 15 C or more above ambient temperature, is positioned on one side of a source with an infrared camera and filter on the other side, then the gas cloud will absorb a certain amount of infrared. Although the basic method is simple, special equipment (camera and filters) is required. 

Primary emphasis is given to flow through circular pipes or tubes since this is the usual means of movement of gases and liquids in process plants. Flow through duct systems is treated with the fan section of Compression in Volume 3. 

The movement of gases through the atmosphere, such as the fragrance of a rose moving from the flower to our noses, generally involves air currents as well as diffusion. Convection, the flow of gas in a current, moves molecules much more rapidly than... 

Above the atmospheric film lies the bulk atmosphere, which is well mixed by turbulence and advection and, hence, is homogeneous in gas composition. Below the sea surfece film lies the bulk seawater, which is also well mixed by turbulence and advection and is consequently homogeneous in gas composition. The thin films are regions in which turbulence and advection play minor roles, such that molecular diffusion controls the movement of gases. Because of the limited degree of air and water motion in... 

The movement of gases tnrough the soil as a criterion of soil structure. Univ. Arizona Coll. Agr. Tech. Bull. No. 39. 

The function of the pumping apparatus is ensure the appropriate movement of gases between the environment and the central airways and is evaluated by measuring ventilatory patterns. Ventilatory parameters must include measures of respiratory rate, tidal volume... 

Currie, J.A., 1970. Movement of gases in soil preparation. Soc. Chem. Ind., Monograph 37 152-169. Cwick, G.J., Bishop, M.P., Howe, R.C., Mausel, P.W., Everitt, J.H. and Escobar, D.E., 1995. Multispcctral video data for detecting biogeochemical conditions at an Alabama oil field site. Geocarto International, 10 59-66. 

One can further investigate the volume increase by using a model experiment for the particle movement of gases. The instrument for kinetic gas theory , which sets small steel spheres in movement in a see-through cylinder, shows a larger volume of moving spheres by increasing the movement frequency of the spheres. This model however has to be discussed in two respects 1. the gas particles move independently and need no vibration motor in order to move,... 

The movement of gases, either through one another or into regions of very low pressure, has many important applications. 

Agglomeration in low density fluidized beds is different in that at least part of the drying takes already place during growth and in the equipment itself The stochastic movements of gases, droplets, and particles, the occurrence of coalescence and bonding and the mechanisms of drying can be modeled and mass, particle size, heat and moisture balances can be established [B.49, B.72, B.93]. Nevertheless, it is an art, performed by experienced personnel of specialized vendors, to successfully scale-up from the performance of test units to commercial equipment and systems. Capacity increases are often obtained by installation of multiple feed points (gas and powder inlets, liquid spray nozzles), which are housed in suitably sized and shaped containments (e.g., towers). 

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