Economizer nozzles

Main feedwater flow during plant startup is only delivered to the economizer inlet feedwater nozzles of the steam generators at temperatures at or above 200°F, which minimizes the probability of condensation-induced water hammer in the economizer sections of the generators. Below a predetermined power level, main feedwater is delivered to the downcomer feedwater inlet nozzles. Changeover to the economizer nozzles at this power level is effected by the Main Feedwater Control System. Emergency feedwater is always delivered to the downcomer inlet nozzles. (See CESSAR-DC, Sections 10.4.7.2.ID and 7.7.1.1.4.)... 

The Cockenzie steam drum failure of May 6 1966 [5] happened during the final, seventh cycle of hydraulic pressure testing before the steam drum would have been declared ready for service. It failed adjacent to one of the economizer nozzles, the transition pieces to the high-pressure pipes in operational service, would have led water from the underside of the drum to the boiler tubes (See Fig. 7.6.)... 

The failure was caused by a crack next to the replaced economizer nozzle, created during the manufacturing process, which had penetrated part-way through the thick... 

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. 

The Majac jet pulverizer (Ho.sokawa Micron Powder Sy.stems Div.) is an opposed-jet type with a mechanical classifier (Fig. 20-55). Fineness is controlled primarily by the classifier speed and the amount of fan air dehvered to the classifier, but other effects can be achieved by variation of nozzle pressure, distance between the muzzles of the gun barrels, and position of the classifier disk. These pulverizers are available in 30 sizes, operated on quantities of compressed air ranging from approximately 0.6 to 13.0 mVmin (20 to 4500 ftV min). In most apphcations, the economics of the use of this type of jet pulverizer becomes attractive in the range of 98 percent through 200 mesh or finer. 

A typical non-condensible blowdown drum and its associated equipment and headers are illustrated in Figure 1. A single blowdown drum may be used for more than one process unit, if economically attractive. However, when this is done, all units served by it must be shut down in order to take the drum out of service, unless cross connections are made to another system of adequate capacity. Normally all closed safety valve discharges are combined into one header entering the drum, although separate headers and inlet nozzles are acceptable if economically advantageous. The following releases are also normally routed into the safety valve header ... 

Steam jet thermocompressors or steam boosters are used to boost or raise the pressure of low pressure steam to a pressure intermediate bettveen this and the pressure of the motive high pressure steam. These are useful and economical when the steam balance allows the use of the necessary pressure levels. The reuse of exhaust steam from turbines is frequently encountered. The principle of operation is the same as for other ejectors. The position of the nozzle with respect to the diffuser is critical, and care must be used to properly posidon all gaskets, etc. The thermal efficiency is high as the only heat loss is due to radiation [5]. 

Steam is the preferred atomizing medium, since it is more economic than compressed air. Steam consumption is typically less than 0.5 per cent of the fuel burnt on a mass basis, although this rises in direct proportion to turndown ratio. On very large burners, the steam flow is modulated in proportion to fuel burnt. Turndown ratios range from about 5 1 for small shell boilers to 12 1 in watertube applications, making this one of the most versatile burners. The steam condition is important in that it must be dry saturated or slightly superheated at the nozzle to avoid condensate formation. On small or non-continuously running plant where no steam is available for start-up a compressed air supply must be provided until steam becomes available from the boiler. 

Lap-joint flanges, Figure 13.33c are used for piped work. They are economical when used with expensive alloy pipe, such as stainless steel, as the flange can be made from inexpensive carbon steel. Usually a short lapped nozzle is welded to the pipe, but with some schedules of pipe the lap can be formed on the pipe itself, and this will give a cheap method of pipe assembly. 

Determine the liquid heights of the light and settling liquids, and arrive at the drum diameter and overall height via a compromise with vapor-phase separation requirements. Adjust the design for such considerations as economic L/D4 ratio and location of inlet nozzle. 

In the plant used for academic purposes [4], both the solvent and exhausted CO2 are wasted. In an industrial plant both streams should be recycled after purification, for obvious economic reasons. The precipitator size and plant-flow-rates are obtained by increasing 80-fold the relative quantities used in the pilot plant [4]. This scale factor was suggested by the company that supplied the drug. Two vessels, P, in parallel are needed while the former is running, the latter can be cleaned and the solid product can be recovered. Cleaning and product-recovery expenses are not directly evaluated in this example. In the pilot plant, the flow of THF-polymer-drug solution was 0.072 kg/h, and the CO2 flowed in the quantity of 1.08 kg/h (the ratio CO2 to solution equals 15). The precipitator was a 0.4-liter vessel. The actual precipitator scale-up is not considered here. The main factor to consider in scaling-up the precipitator is the nozzle scale-up. The nozzle-size, nozzle-shape, and number of nozzles per reactor volume, determine the precipitate size in a complex and still incompletely understood way [5-8], It is assumed that issues related to the injectors are already solved. 

Circulation and shear of the liquid in a vessel can be accomplished with external pumps and appropriate location of suction and discharge nozzles, but a satisfactory combination of vertical and lateral flows is obtained more economically by internal impellers, baffles, and draft tubes. Some general statements about dimensions, proportions, and internals of a liquid mixing vessel can be made. 

The full lift position affords the biggest possible API orifice, where the nozzle area gives the capacity. In this case, when the bolt is fully screwed down, a lower size valve provides more capacity than another standard API valve, which could make it more economic, lighter, and so forth. 

The way the inlet nozzle enters the vessel it is protecting can also have a serious impact on inlet pressure losses. Of course, the ones which give the biggest pressure drops are also the most economic vessel penetrations. 

In general, a pneumatic nozzle can produce sprays of fine droplets to provide a large interface area for heat and mass transfer but the power consumption for atomization is very high. In some cases, e.g., when it is used in technical equipment for environmental protection to remove harmful gases, its high power consumption may become a significant economic problem. 

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