| OCR Text |
Show 1.0 INTRODUCTION (con't) 1.2 Reactor Development The ''first generation" reactor type developed was of the so-called Parallel Passage Reactor (PPR) type (see Ref. 2 and Fig. 1). In this reactor type, the flue gas moves at a relatively high velocity through narrow gas channels. by diffusion, gas is transported laterally into the adjoining catalyst slabs where the reduction of NOx with ammonia takes place. The first commercial project where PPR technology was applied was in the revamp of an ethylene cracker at ROW (Rheinische Olefine Werke) in the FRG (W. Germany), a 50/50 Shell/BASF joint venture. The furnace section was supplied by KTI; Shell supplied the denox system. The design temperature for the denox system is 3200 F. The amount of catalyst installed is about 60 m3 . Start up of the unit proceeded successfully and without problems in April, 1990. A further development is represented by the so-called Lateral Flow Reactor (LFR), schematically represented in Figure 2. In this reactor type, the gas is forced through the catalyst slabs which results in better catalyst utilization than attainable with the PPR, particularly in the higher (> 5000 F) temperature range. Although the LFR concept was primarily conceived for low fouling environments (e.g., gas fired furnaces), several schemes have been developed to overcome fouling problems when and if they occur. For horizontal gas flows, the catalyst slabs can be vertically oriented and fouled material can be discharged by gravitational flow and replaced by clean catalyst loaded from the top of the slabs. Several charge/discharge devices are conceivable using, for example, vacuum suction systems, aerated plates, etc. For vertical gas flows, the slabs can be tilted at an angle greater than the angle of repose of the granules so that gravity discharge is still possible (see Fig. 3). For nonfouling flows, the option exists to house the catalyst in modules, which facilitates the manufacture of the reactor, especially if the reactor size is large (see Fig. 4). In Section 2.0, we shall consider the design of an LFR unit in detail. 2 |
