Filtration combustion process

The algorithm described above was successfully used for simulation of the filtration combustion process for the synthesis of nitrogen ceramics. 

We will first discuss some results obtained for a onedimensional formulation of the filtration combustion process. The initial conditions are given by... 

VHiereas the previous case revealed temperature and conversion profiles propagating with almost constant velocity ("constant-pattern profiles"), the next case shows oscillatory behavior of the filtration combustion process for parameters a = 1.0, p = 0.08, y = 0.05, 6 = 1.0, (A) = 100.0, L =50.0 and 8 = -10.0. Figure 3a... 

The first case covers for example flue-gas treatment, which requires the filtration of fly-ash and the reduction of NOx, or gasification processes, where particulates and high-boiling tars have to be removed. An example of the second case is that of combustion processes, where incomplete combustion leads to the emission of carbonaceous particulates. The most relevant topic in this category is the reduction of diesel particulate emissions ( diesel soot ) by catalytic filtration. A more exotic example is the reaction cyclone for the thermal conversion of biomass, which also combines chemical reactions and separation in one apparatus, though its separation mechanism is not filtration. 

Aldushin, A. R, Ivleva, T. R, Merzhanov, A. G., Khaikin, B. I., and Shkadinskii, K. G., Combustion front propagation in porous exothermic metallic samples with oxidizer filtration. In Combustion Processes in Chemical Engineering and Metallurgy (Russ.) (A. G. Merzhanov, ed.). USSR Academy of Science, Chemogolovka, Russia, 1975, p. 245. 

As previously mentioned, bag filters have, practically, the same applications of cyclones, being normally coupled with these in order to remove the finest tails of particle size distributions of diverse industrial powders. They can be used in recovery of fines fractions in spray drying and pneumatic conveying. They are also widely used in industries and many o er places for purification of ambient air. Recovered materials by filtration are varied and include granite powder, fumes from combustion processes, fine dust released in many industrial applications, and so on. 

Filtration combustion-based processes. In the production of syngas, it is necessary to supply energy into the reaction mixture to initiate endothermic steps and, at the same... 

The carbon black (soot) produced in the partial combustion and electrical discharge processes is of rather small particle si2e and contains substantial amounts of higher (mostly aromatic) hydrocarbons which may render it hydrophobic, sticky, and difficult to remove by filtration. Electrostatic units, combined with water scmbbers, moving coke beds, and bag filters, are used for the removal of soot. The recovery is illustrated by the BASF separation and purification system (23). The bulk of the carbon in the reactor effluent is removed by a water scmbber (quencher). Residual carbon clean-up is by electrostatic filtering in the case of methane feedstock, and by coke particles if the feed is naphtha. Carbon in the quench water is concentrated by flotation, then burned. 

Once an undesirable material is created, the most widely used approach to exhaust emission control is the appHcation of add-on control devices (6). Eor organic vapors, these devices can be one of two types, combustion or capture. AppHcable combustion devices include thermal iaciaerators (qv), ie, rotary kilns, Hquid injection combusters, fixed hearths, and uidi2ed-bed combustors catalytic oxidi2ation devices flares or boilers/process heaters. Primary appHcable capture devices include condensers, adsorbers, and absorbers, although such techniques as precipitation and membrane filtration ate finding increased appHcation. A comparison of the primary control alternatives is shown in Table 1 (see also Absorption Adsorption Membrane technology). 

Step 4 Define the System Boundaries. This depends on the nature of the unit process and individual unit operations. For example, some processes involve only mass flowthrough. An example is filtration. This unit operation involves only the physical separation of materials (e.g., particulates from air). Hence, we view the filtration equipment as a simple box on the process flow sheet, with one flow input (contaminated air) and two flow outputs (clean air and captured dust). This is an example of a system where no chemical reaction is involved. In contrast, if a chemical reaction is involved, then we must take into consideration the kinetics of the reaction, the stoichiometry of the reaction, and the by-products produced. An example is the combustion of coal in a boiler. On a process flow sheet, coal, water, and energy are the inputs to the box (the furnace), and the outputs are steam, ash, NOj, SOj, and CO2. 

Modem coal combustion employs two principal techniques combustion in a fluidized bed or pulverization, followed by combustion of fine particles suspended in moving air. Figure 1 shows a schematic of pulverized coal combustion, a process much used in steam-raising plants. Each process produces a characteristic residue fluidized bed combustion gives rise mainly to a clinker-like or granular product, whereas pulverization, followed by combustion, produces mainly a much finer, micrometre-sized ash residue. Pulverization also yields a coarser fraction, the so called bottom ash , which is periodically removed without difficulty. However, the finer fly ash has to be recovered by filtration and electrostatic precipitation. Commercially, fly ash has... 

Volcanic and Other Surface Deposits. Sulfur is recovered from volcanic and other surface deposits by a number of different processes, including distillation, flotation, autoclaving, filtration, solvent extraction, or a combination of several of these processes. The Japanese sulfur deposits are reached by tunnel, and mining is done by the room-and-pillar, chamber-and-pillar with filling, and cut-and-fill systems. Sulfur was historically extracted from the ore by a distillation process performed in rows of cast-iron pots, each containing about 180 kg of ore. Each row of pots is connected to a condensation chamber outside the furnace. A short length of pipe connects each pot with a condenser. Brick flues connect combustion gases under the pots. Sulfur vapor flows from the pots to the condensation chamber where the liquid sulfur is collected. The Japanese ore contains 25—35 wt % sulfur. This method has been superseded by other sources of sulfur production. 

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