Temperature monolithic

A. Nakhjavan, P. Bjombom, M.F.M. Zwinkels, and S.G. Jaras, Numerical analysis of the transient performance of high-temperature monolith catalytic combustors Effect of catalyst porosity, Chem. Eng. Sci. 50 2255 (1995). 

Figure 50. Influence of the dynamics in the exhaust gas composition on the conversion of carbon monoxide over a three-way catalyst at various settings of the exhaust gas temperature, (monolith catalyst 62 cells cm engine bench light-off test, space velocity 60000Nll- h- Pt 1.42gr>, Rh 0.28gr ).

Figure 52. Influence of the exhaust gas oxygen content on the conversion of (a) CO (b) HC and (c) NOjt reached over a three-way catalyst at various settings of the catalyst temperature (monolith catalyst with 62 cells cm , three-way formulation with Pt 0.38gl , Rh 0.16gC ), fresh model gas reactor space velocity 60000 Nil h static conditions).

Figure 1 5. Conversion of carbon monoxide, gaseous hydrocarbons and sulfur dioxide reached over a diesel catalyst with and without measures to suppress the formation of sulfates, as a function of the exhaust gas temperature (monolith catalyst with 62 cells cm dedicated diesel washcoat formulations with platinum at a loading of 1.76 g I" diesel engine test bench light-off test at a space velocity of 120000 N1 F h diesel engine bench aging procedure for 100 h at a catalyst inlet temperature of 773 K).

Figure 113. Conversion of nitrogen oxides and gaseous hydrocarbons reached over different NO.v-reduction catalyst formulations, as a function of the exhaust gas temperature (monolith catalyst with 62 cells cm dedicated NO t-reduction catalyst formulations with zeolites and with different active components, after laboratory oven-aging in air at a temperature of 1023 K for 16 hours light-off test in a model gas reactor at a space velocity of 50000 N11 h model gas simulates the exhaust gas composition of an IDl/NA passenger car diesel engine at medium load and speed, except for the hydrocarbon concentration, which was increased to reach yHc yNO, 3 1 (mol mol)).

Drop in temperature. Monoliths. Advanced beads. In Africa, burning of grassland to cultivate tubers. 

I. M. Lachman, R. N. McNally, High Temperature Monolithic Supports for Automobile Exhaust Catalyst , American Ceramics Society, May 1981. 

Blanco, J., Avila, R, Marzo, L., Suarez, S., and Knapp, C. Low temperature monolithic SCR catalysts for tail gas treatment in nitric acid plants. Stud. Surf. Sci. Catal 2000,130, 1391-1396. 

W.G. Fahrenholtz, G.E. Hilmas, A.L. Chamberlain, J.W. Zimmermann and B. Fahrenholtz Processing and characterization of ZrB2-based ultra-high temperature monolithic and fibrous monolithic ceramics. Journal of Materials Science 39, 5951-5957 (2004). 

For monolithic refractories, the formulations are made so that the ceramic properties develop when they are exposed to high temperatures. Monolithic refractories, like plastics, ramming mixes, dry vibratables, mortars, and coatings. 

Fig. 9. Monolithic multilayer ceramics (MMCs) derived from multilayer capacitor, high temperature cofire, and thick film technologies.

Work in the area of simultaneous heat and mass transfer has centered on the solution of equations such as 1—18 for cases where the stmcture and properties of a soHd phase must also be considered, as in drying (qv) or adsorption (qv), or where a chemical reaction takes place. Drying simulation (45—47) and drying of foods (48,49) have been particularly active subjects. In the adsorption area the separation of multicomponent fluid mixtures is influenced by comparative rates of diffusion and by interface temperatures (50,51). In the area of reactor studies there has been much interest in monolithic and honeycomb catalytic reactions (52,53) (see Exhaust control, industrial). Eor these kinds of appHcations psychrometric charts for systems other than air—water would be useful. The constmction of such has been considered (54). 

Creep Resistsince. Studies on creep resistance of particulate reinforced composites seem to indicate that such composites are less creep resistant than are monolithic matrices. Silicon nitride reinforced with 40 vol % TiN has been found to have a higher creep rate and a reduced creep strength compared to that of unreinforced silicon nitride. Further reduction in properties have been observed with an increase in the volume fraction of particles and a decrease in the particle size (20). Similar results have been found for SiC particulate reinforced silicon nitride (64). Poor creep behavior has been attributed to the presence of glassy phases in the composite, and removal of these from the microstmcture may improve the high temperature mechanical properties (64). 

Since NO production depends on the flame temperature and quantity of excess air, achieving required limits may not be possible through burner design alone. Therefore, many new designs incorporate DENOX units that employ catalytic methods to reduce the NO limit. Platinum-containing monolithic catalysts are used (36). Each catalyst performs optimally for a specific temperature range, and most of them work properly around 400°C. 

Catalytic Unit. The catalytic unit consists of an activated coating layer spread uniformly on a monolithic substrate. The catalyst predominantly used in the United States and Canada is known as the three-way conversion (TWC) catalyst, because it destroys aU three types of regulated poUutants HC, CO, and NO. Between 1975 and the early 1980s, an oxidation catalyst was used. Its use declined with the development of the TWC catalyst. The TWC catalytic efficiency is shown in Figure 5. At temperatures of >300° C a TWC destroys HC, CO, and NO effectively when the air/fuel mixture is close to... 

The activated coating layer must possess two additional properties. It must adhere tenaciously to the monolithic honeycomb surface under conditions of rapid thermal changes, high flow, and moisture condensation, evaporation, or freezing. It must have an open porous stmcture to permit easy gas passage iato the coating layer and back iato the main exhaust stream. It must maintain this porous stmcture even after exposure to temperatures exceeding 900°C. 

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