Adsorption adsorber vessel

Pressure Swing Adsorption. A number of processes based on Pressure Swing Adsorption (PSA) technology have been used in the production of carbon dioxide. In one version of the PSA process, CO2 is separated from CH using a multibed adsorption process (41). In this process both CH4 and CO2 are produced. The process requires the use of five adsorber vessels. Processes of this type can be used for producing CO2 from natural gas weUs, landfiU gas, or from oil weUs undergoing CO2 flooding for enhanced oil recovery (see Adsorption, gas separation). 

Adsorber Vessel The most frequently used method of fluid-solid contac t for adsorption operations is in cyhndrical, vertical vessels, with... 

FIG. 16-46 Pressurized adsorber vessel. (Reptinted with peirrussion of EPA. Reference EPA, Process Design Manual for Carbon Adsorption, U.S. Envir. Protect. Agency., Cincinnati, 1973.)... 

HG. 16-47 Ambient pressure adsorber vessel. (Reptinted with permission of Ann Arhor Science. Reference Leatherdale in Cheremisinoff and Ellerhusch, Carbon Adsorption Handbook, Ann Arhor Science, Ann Arhor, 1978. )... 

The third process used in the production of carbon dioxide is pressure swing adsorption. The feed gas usually contains approximately 20 percent carbon dioxide, 70 percent hydrogen, and the remainder methane, carbon monoxide, nitrogen, and water. The feed gas is typically under a pressure of 125 100 psig at temperatures of 80-120°F. The carbon dioxide and water are strongly adsorbed in the adsorb beds and the residual gas stream is depressurized for further recovery. The adsorber vessel is then evacuated through vacuum blowers where the carbon dioxide, which has been adsorbed by the bed, is released at purities of essentially 99+ percent pure. 

Three generic adsorptive process schemes have been commercialized to serve most of the applications shown in Table 1. They include 1) temperature swing adsorption (TSA) 2) pressure swing adsorption (PSA) and 3) concentration swing adsorption (CSA).P The fluid mixture (feed) to be separated is passed over a regenerated adsorbent (contained in an adsorber vessel) to produce a stream enriched in the less strongly adsorbed components of the mixture. 

Another very important adsorbent property affecting the adsorption process is the adsorption capacity because it determines the size of an adsorbent vessel, the amount of adsorbents required, and the related capital and operating costs. The requirements for commercial sorbents are discussed briefly as follows. 

Purification is based on advanced PSA technology. The process units contain 3 12 adsorber vessels. One or more adsorbers are on the adsorption step, while the others are undergoing various stages of regeneration. No feed treatment other than entrained liquid removal is required. Materials for piping and adsorbers are carbon steel. According to the licensor of the technology, UOP,... 

Adsorption capacity (or loading) is probably the most important characteristic of an adsorbent. More detail is provided in Section 14.3.2. The loading is the amount of adsorbate taken up by the adsorbent, per unit mass (or volume) of the adsorbent, and it depends on the fluid-phase concentration, the temperature, and other conditions (especially the initial condition of the adsorbent). Typically, adsorption capacity data are plotted as isotherms (loading of adsorbate on the adsorbent versus fluid-phase adsorbate concentration at constant temperature), isosteres, isobars, and others mentioned later. Examples are shown in Figures 14.1 through 14.3. Adsorption capacity is of paramount importance to the capital cost, because it sets the amount of adsorbent required and also the volume of the adsorber vessels the costs of both are significant if not dominant. When comparing alternate adsorbents, it is fair to express their capacity on a per unit volume basis, since that fixes... 

Figure 4-6 shows a discontinuously operated adsorption unit including three adsorber vessels connected in series, and filled with active carbon beds for the pretreatment of wastewater. Regeneration... 

The mechanical properties such as crush strength and attrition resistance are important properties for industrial adsorbents, especially for uses in moving or fluidized bed processes. Adsorbents with poor mechanical properties are usually not appropriate for industrial applications in fixed-bed processes due to the problems of dust formation in the adsorbent vessels, which will change the particle size distribution of the adsorbents and increase in the pressure drop of the adsorption system. Furthermore, the loss of the adsorbent weight due to dust formation will also deteriorate the performance of the adsorption system. 

These needs are defined by three criteria. All are employed in the design of the adsorber vessel, and are that the vessel (1) has adequate capacity for internal transfer of heat from the adsorbent to the moving air , (2) holds up the moving air stream for an adequate time to allow for adsorption to be complete, and (3) contains a sufficient quantity of activated carbon to provide service forwhatever long-term period is desired. 

The adsorber vessel is filled with zeolitic crystals [2.26] which are bound with ceramic material and formed to spheres of about 3 mm diameter or rods. The crystalline components have pores with diameters in the range of approx. 1 nm. H2O as well as other polar or easily polarizable impurities such as CO2 and various hydrocarbons are retained in the pores. Frequently a thin layer of activated aluminium oxide for H2O adsorption is arranged in front of the zeolitic layer. 

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