Separation processes cyclones

Cyclone collectors are popularly used both for particle removal and for particle sampling (Fig. 13.1). The separation process of a cyclone relies on the centrifugal accelerations that are produced when particle-laden fluid experi-... 

As a simple and efficient particle separation device, cyclone collectors can be used for anything from dust removal in a fluid stream to material collection in the fluid conveying system. However, the cyclone is not suitable or economical for the separation of extremely small particles (say, less than 1 /xm), which frequently occur in industrial processes. It is recommended that the size of particles to be separated in an industrial ventilation cyclone be in the region of around 10 to 100 p.m. However, for the purpose of aerosol sampling, the size of particles to be separated may be much less than 10 jxm. 

The papers in this section represent the theory and current industry practices in the separation process and in separator design. Because separation is such a basic requirement for the oil and gas industry, a wealth of information has been published concerning the process and the various design techniques used in the manufacture of separation equipment. Some of these techniques are proprietary, however, and the details of the design are not readily available. For instance. British Petroleum has done considerable design and testing of cyclone-type separation equipment in recent years with the objective of miniaturizing the equipment for use on offshore platforms. For further details on this and other proprietary equipment, one must contact the manufacturer or licensee of the equipment. 

The solids are thrown outwards against the wall of the vessel and then move away from the gas inlet and are collected in the conical base of the equipment. This separation process is very effective unless the gas contains a large proportion of solid particles less than 10 p in diameter and is equally effective when used with dust or mist-laden gases. The cyclone separators are obviously rubber lined to withstand wear at the velocity of gas and corrosion and are the most commonly used general purpose separator in the chemical process industry. 

In the process (Figure 8-12), the feedstock is vaporized upon contacting hot regenerated catalyst at the base of the riser and lifts the catalyst into the reactor vessel separation chamber where rapid disengagement of the hydrocarbon vapors from the catalyst is accomplished by both a special solids separator and cyclones. The bulk of the cracking reactions takes place at the moment of contact and continues as the catalyst and hydrocarbons travel up the riser. The reaction products, along with a minute amount of entrained catalyst, then flow to the fractionation column. The stripped spent catalyst, deactivated with coke, flows into the Number 1 regenerator. 

Power supply, 9 from a not gas stream, 12 generation with steam, 11 Pressure control, 42,44,51,52,59,60 Pressure drop cyclone separators, 617 gas-solid flow, 119-120 granular beds, 117 heat exchanger example, 193, 194 heat exchangers, 188 non-Newtonian flow, 106-109 wire mesh pads, 616 Pressure drop, piplines, 92 chart method, 96 two-phase flow, 116 typical values, 95 Ptaskie vessel code, ASME, 625 Prilling, 361,362 equipment size, 367 flowsketch, 366 operating, data. 367 products of, 367 size distribution, 362 Prism membrane separation process, 633 643... 

In the South African mining industry most processes for recovering precious metals, coal, minerals and diamonds are wet methods, involving the suspension of solids in water [1], In the control of such wet abrasive conditions in the pumping of fine particles size slurries, particle size separation in cyclones and in floatation cells, the choice of soft natural rubber lining is the most cost effective. 

Despite the huge demand for biomass processes, its reactors do not present major innovations and most of them are nsed in the oil and petrochemical processes. The literature presents several systems, bnt most of them are fluidized beds, because they satisfy some important reqnirements, such as, low residence times, high heat, and mass transfer and, in particnlar, the large movement of solid particles in contact with gases or vapors, which improves the decomposition reaction and fast evolution of products (gases or vapors) in the reactor. This rapid evolution goes to phase separation in cyclones and condensers. Cyclones and separation/cooling processes will not be discussed here they have been extensively reported in the literature (Lede, 2000). 

For elutriator systems, mechanical screen separators, and cyclone separators, various devices to perform the classification and removal function, include eludriator systems, mechanical system separators, and cyclone separators. Once parts have been ground, there is often a need to remove dust or oversize slivers of material from the regrind prior to its reintroduction into the process. Removal of fines can be accomplished by means of elutriation or air scalper systems which are shown in Fig. 7.24. Mechanical screen separators, such as Fig. 7.25, have the ability to remove both fines and oversize particles in one step. 

As was pointed out at the beginning of this section, there are several other models available for predicting cyclone performance, but those were obtained from curve-fitting exercises and, as such, do not represent a true physical model of the separation process in hydrocyclones. These models are reported in the next section. 

Fig 3, The sand is used as fluidized medium and steam preheated to 400 to 500 C acts as a fluidizing gas. The fluid bed reactor is externally heated by propane burners. The gas/steam mixture passes through a multi - step cooling / separation process. First, solids such as soot and dust are precipitated in a cyclone. Next, water is condensed in a... 

Once the reservoir is in production, a variety of functional chemicals are required to prevent unwanted chemical and biological reactions and discourage precipitation or evolution of undesirable solids or gases in the oil and water streams. They are also used to protect assets from corrosion and fouUng and help in oil, gas, and water separation and cleanup processes. These chanicals often work in tandem with mechanical processes (as in the case in oil/water separation, where separators and cyclones are employed). 

The cross section of a tangential inlet tube to a cyclone is often rectangular. Inlets with circular cross sections ( pipe-type inlets) are mostly used only in small sampling cyclones and in some applications where a simple circular inlet can achieve the desired separation and/or simplicity of construction and low cost are prime considerations. Certain shop and grain-processing cyclones fall into this category. 

For fine pulverization, both dry and wet processes are utilized, but increasingly the dry process is more popular because wet grinding ultimately requires drying and is much more energy intensive. A sensitive fan swirls the dust sizes into the air separator and permits coarse particles to recycle to the grinding mill or be rejected as tailings the fines are drawn into cyclones where the dust is collected. 

The product stream contains gases and soflds. The soflds are removed by using either cyclones, filters, or both in combination. Cyclones are devices used to separate soflds from fluids using vortex flow. The product gas stream must be cooled before being sent to the collection and refining system. The ALMA process uses cyclones as a primary separation technique with filters employed as a final separation step after the off-gas has been cooled and before it is sent to the collection and refining system (148). As in the fixed-bed process, the reactor off-gas must be incinerated to destroy unreacted butane and by-products before being vented to the atmosphere. 

Sodium sihcate (41°Bh, 1 3.22 ratio Na20 Si02) is added in the milling operation to disperse the slime, mosdy kaolin. Dispersion also aids the grinding process. The rod mill serves to grind the ore to 0.833 mm (—20 mesh) or to the point where mica, quart2, feldspar, and iron minerals are Hberated. Cyclones, or rake, hydrauhc, or other types of classifiers, are used after grinding to produce coarse and fine mica fractions that are treated separately. 

The hydrocyclone, commonly referred to simply as cyclone, is a nonmechanical sedimentation-type classifier (2,6,10,27) (Fig. 7). It has no moving parts or power attachments directly connected to it. The hydrocyclone has become the workhorse of most mineral processing operations because of its simplicity, short residence time, compactness, and low cost of operation. It is, however, characterized by lack of sharpness of separation. Equipment... 

Polymerization in Hquid monomer was pioneered by RexaH Dmg and Chemical and Phillips Petroleum (United States). In the RexaH process, Hquid propylene is polymerized in a stirred reactor to form a polymer slurry. This suspension is transferred to a cyclone to separate the polymer from gaseous monomer under atmospheric pressure. The gaseous monomer is then compressed, condensed, and recycled to the polymerizer (123). In the Phillips process, polymerization occurs in loop reactors, increasing the ratio of available heat-transfer surface to reactor volume (124). In both of these processes, high catalyst residues necessitate post-reactor treatment of the polymer. 

Hydrolysis of Dimethyl Terephthalate. Hoechst Celanese and Eormosa Chemical Eibers Corp. produce a polymer-grade terephthahc acid by hydrolysis of high purity dimethyl terephthalate. Hbls-Troisdorf AG hcenses a process with this step (70). Hydrolysis occurs at 260—280°C and 4500—5500 kPa (45—55 atm) in a hydrolysis reactor without catalysis. The overhead methanol and water vapor is separated and the methanol is returned to the dimethyl terephthalate section for reuse. The reactor hquid is crystallized, cycloned, washed, and further cooled. Einahy, the slurry is centrifuged and dried. The product has less than 25 ppm of 4-formylbenzoic acid and very low levels of other impurities. There may be several hundred parts per million of monomethyl terephthalate, which is incompletely hydrolyzed dimethyl terephthalate. 

Handling of alumina and coke presents dusting problems. Hoods and exhaust systems collect the dust, which is then separated from the exhaust air either by cyclones, electrostatic precipitators, filter bags, or a combination of these methods, and recycled to the process (see Air pollution control PffiTHODS). 

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