Orifice chamber

W ste Hea.t Boilers. In a conventional FCCU flue gas system, the regenerator combustion gases pass through two stages of cyclonic separators, a sHde valve, orifice chamber, waste heat boiler, and electrostatic precipitator. The sHde valve and orifice chamber act in combination to reduce the flue gas to essentially atmospheric pressure. 

In most units, the flue gas pressure is reduced to atmospheric pressure across an orifice chamber. The orifice chamber is a vessel containing a series of perforated plates designed to maintain a given back-pressure upstream of the regenerator pressure control valve. 

Controlled catalyst circulation is one of the most important prerequisites for trouble-free operation of the FCC unit. Uniform circulation is ensured by controlling the differential pressure between the reactor and regenerator. The differential pressure in the existing plant is controlled by a differential pressure governor adjusting the position of the double slide valve upstream of the orifice chamber. 

A design consideration for an environmental application of TSS technology is location. In a PRT unit, the TSS is always located in a hot flue gas position. However, a cold flue gas position could be used for environmental applications. Depending upon the pressure control scheme, the TSS can also be located at high pressure before the flue gas slide valve and orifice chamber. This offers significant cost savings, lower material cost, and requires less plot space. On two ERA consent decree applications, this benefit was 40% lower capital cost. 

The actuator contains the final orifice and a finger pad or mechanical linkage for on—off control. The spray pattern is largely affected by the constmction of the actuator, particularly by the chamber preceding the orifice. Actuators are often termed mechanical breakup and nonmechanical breakup depending upon the complexity of this chamber. Mechanical breakup actuators are of more expensive two-piece constmction. Actuators are usually molded from polyethylene or polypropylene the breakup insert may be almost any material, including metal. 

Because the highest possible interfacial area is desired for the heterogeneous reaction mixture, advances have also been made in the techniques used for mixing the two reaction phases. Several jet impingement reactors have been developed that are especially suited for nitration reactions (14). The process boosts reaction rates and yields. It also reduces the formation of by-products such as mono-, di-, and trinitrophenol by 50%. First Chemical (Pascagoula, Mississippi) uses this process at its plant. Another technique is to atomize the reactant layers by pressure injection through an orifice nozzle into a reaction chamber (15). The technique uses pressures of typically 0.21—0.93 MPa (30—135 psi) and consistendy produces droplets less than 1 p.m in size. The process is economical to build and operate, is safe, and leads to a substantially pure product. 

There are two types of impulse printers (Eig. 19). A piezoelectric ink jet propels a drop by flexing one or more walls of the firing chamber to decrease rapidly the volume of the firing chamber. This causes a pressure pulse and forces out a drop of ink. The flexing wall is either a piezoelectric crystal or a diaphragm driven by a piezoelectric incorporated into the firing chamber (Eig. 19a). Thermal impulse ink jets also propel one drop at a time, but these use rapid bubble formation to force part of the ink in a firing chamber out the orifice (Eig. 19b). 

Some of the melted ziac is fed to the ziac-dust unit where the molten ziac may be dropped from a cmcible through a small orifice (2.5 mm) to be atomized ia a blast of air. SoHdifted droplets are collected ia a chamber and screened to the proper size for purification and cadmium plant cementation. Frequently, coarse (+70 200 and fine (—70 fiva) fractions are required. 

Spray characteristics of pressure nozzles depend on the pressure and nozzle-orifice size. Pressure affects not only the spray characteristics but also the capacity. If it is desired to reduce the amount of liquid sprayed by lowering the pressure, then the spray may become coarser. To correct this, a smaller orifice would be inserted, which might then require a higher pressure to produce the desired capacity, and a spray that would be finer than desired might result. Multiple nozzles tend to overcome this inflexible charac teristic of pressure atomization, although several nozzles on a diyer complicate the chamber design and air-flow pattern and risk collision of particles, resulting in nonuniformity of spray and particle size. 

FIG. 14-87 Charactersitic spray nozzles, a) Whirl-chamber hollow cone, (h ) Solid cone, (c) Oval-orifice fan. (d) Deflector jet. (e) Impinging jet. (/) Bypass, (g) Poppet, (h) Two-flnid. ( ) Vaned rotating wheel. 

Continuous, surface blowdown arrangements employ a multistage nozzle valve that permits the BW to expand and flash gradually and safely across each successive orifice and chamber with almost no noise. This effect reduces the flow velocity and virtually eliminates the risk of wire drawing. The BD valve is provided with a regulating lever and calibrated dial (or an electric actuator) for either manual or automatic BD rate adjustment. Continuous blowdown arrangements are entirely suitable for incorporation into FSHR systems. They are commonly employed for WT boilers. 

Coriolis acceleration effects in a combustion chamber (dia 90 and width 30mm), vented at the periphery through four orifices, having 7.5 mm in diameter, 4% propane/air mixture, rotation speed (a) lOOOrpm and (b) 2000rpm. 

A ceramic block such as alumina is generally used because of its chemical inertness and the orifice is bored or drilled to precise dimensions. The block is placed so that two (2) chambers result. Then if a DC voltage is applied across the electrodes, a current will flow onty through the orifice, and an effective resistance arises which depends upon the voltage applied and the size (volume of the conducting solution) of the orifice. Particles are added to one side of the two chambers created by the ceramic block, and the suspension is pumped through to the other side. There will be an electrical pulse as each particle passes through the orifice. 

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