Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Patent
1996-05-12
1998-08-11
Kastler, Scott
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
502316, B01D 5000
Patent
active
057924325
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a catalyst unit for purifying a gas and more particularly, to a catalyst unit employing a plate-shaped catalyst elements for efficiently reducing nitrogen oxides (hereinafter referred to as "NOx") with ammonia (NH.sub.3), and gas processing employing the catalyst unit.
BACKGROUND ART
The NOx contained in the exhausted gas discharged by power plants, plants, automobiles and such is a substance causative of photochemical smog and acid rain. An exhaust gas denitrating method that employs NH.sub.3 as a reducing agent for selective catalytic reduction has been prevalently used as an effective denitrating method principally in thermal power plants. A titanium oxide (TiO.sub.2) catalyst containing vanadium (V), molybdenum (Mo) or tungsten (W) as an active ingredient is used. Particularly, a catalyst containing vanadium (V) is highly active, difficult to be deteriorated by impurities contained in exhaust gases and effective even at low temperatures. Therefore, such a catalyst is the most currently prevalent denitrating catalyst (JP-A No. 50-128681).
Generally, catalyst elements are formed in the shape of a honeycomb or a plate. Various methods of manufacturing catalyst elements have been developed. A well-known flat catalytic plate is formed by coating and cladding a mesh base member formed by working a thin metal sheet in a metal lath and spraying aluminum over the metal lath, a textile fabric or a nonwoven fabric with a catalyst. This flat catalytic plate is worked to obtain a plate-shaped catalyst element 1 having ribs 2 of a wavelike cross section, and flat sections 3 in an alternate arrangement as shown in FIG. 2. A plurality of such catalyst elements 1 are stacked in layers in a case 4 with the ribs 2 extended in the same direction to construct a catalyst unit 8 (JP-A No. 54-79188 and JPO filing No. 63-324676) as shown in FIG. 43. Since this known catalyst unit 8 causes comparatively small pressure loss and cannot be easily clogged with soot and coal ashes, the catalyst unit 8 is employed prevalently in denitrating apparatuses for denitrating the exhaust gases of boilers for thermal power generation.
The number of power generating installations equipped with gas-turbines or combinations of gas-turbines and waste heat recovery boilers has progressively increased in recent years to cope with peak power demand in summer. Most of such power generating installations are located in the suburbs of cities, and exhaust gas processing apparatus must be highly efficient and compact in view of site condition and pollution control. Under such circumstances, a method of efficiently reducing the NOx content of exhaust gases proposed in JP-A No. 55-152552 employs a catalyst unit 8 constructed by stacking catalyst elements 1 as shown in FIG. 2 so that the respective ribs 2 of the adjacent catalyst elements 1 extend perpendicular to each other, and disposes the catalyst unit 8 with the ribs 2 of the alternate catalyst elements 1 extending perpendicular to the direction of gas flow 6 and with the ribs 2 of the rest of the catalyst elements 1 extending in parallel to the direction of gas flow 6 as shown in FIG. 44.
A catalyst unit 11 proposed in JP-Y.sub.2 No. 52-6673 is formed by working metal laths or a metal sheets to obtain corrugated sheets 9 having successive ridges 10 of a wavelike cross section and not having any flat section as shown in FIG. 46, constructing a support structure by stacking the corrugated sheets 9 so that the respective ridges 10 of the adjacent corrugated sheets 9 extend across each other as shown in FIG. 47, and a catalyst is supported on the support structure to complete the catalyst unit 11. The catalyst unit 8 of FIG. 43 needs the following improvements to construct a high-efficiency, compact exhaust gas processing apparatus. FIG. 48 shows some of gas passages defined by the catalyst elements 1 stacked with the ribs 2 extended in parallel to the direction of gas flow 6. Catalyst units 8 of this type causing very small pressure loss, the exhaust g
REFERENCES:
patent: 4285838 (1981-08-01), Ishida et al.
Ishikawa Tomihisa
Kato Yasuyoshi
Kuroda Hiroshi
Michimoto Takashi
Morii Masaharu
Babcock-Hitachi Kabushiki Kaisha
Kastler Scott
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