Condenser pressure

The apparatus (Pig. 22) is convenient to use when it is desired to distil at ordinary pressure or in vacuo a solid of high boiling point which would solidify in an ordinary condenser, e.g., a- or jS-naphthol, or benzidine. 

The condenser, made of steel tubing, consists of a 4-inch diameter outer jacket A, surrounding 4 or 6 tubes of J-inch diameter expanded into the plates B. Plate C is in the form of a flat ring, while to plate D is attached the delivery tube from the cast-iron still H. The chamber E then serves as a receiving chamber for the vapours. Similarly, chamber F acts as a delivery chamber for the condensed liquid, which then flows out 

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Melamine - formaldehyde polymers. Melamine (2 4 6-triamino-1 3 5-triazine), obtained by heating dicyandiamide under pressure, condenses with formalin to give melamine - formaldehyde polymers (Beetle - Melamine), which have similar uses, but better stability to heat... 

Figure 4 shows high-pressure condensate (small line) being added to low-pressure condensate without the usual troublesome hammer. The high-pressure condensate has a chance to cool before emerging into the low-pressure condensate line. 

Figure 4. Method for adding high-pressure condensate to low-pressure condensated without troublesome water hammer.

Often in plant operations condensate at high pressures are let down to lower pressures. In such situations some low-pressure flash steam is produced, and the low-pressure condensate is either sent to a power plant or is cascaded to a lower pressure level. The following analysis solves the mass and heat balances that describe such a system, and can be used as an approximate calculation procedure. Refer to Figure 2 for a simplified view of the system and the basis for developing the mass and energy balances. We consider the condensate to be at pressure Pj and temperature tj, from whence it is let down to pressure 2. The saturation temperature at pressure Pj is tj. The vapor flow is defined as V Ibs/hr, and the condensate quality is defined as L Ibs/hr. The mass balance derived from Figure 2 is ... 

This equation expresses the fraction of the high-pressure condensate returned as low-pressure condensate. The input information needed to apply the working equation are tj and P[. Values for h can be approximated from the following ... 

Figure 6.2-2 shows its operation. A mixture of 14% steam and 86% water from the pressure tubes went to steam drums, used to separate steam from liquid water with steam on top and liquid on the bottom. Steam drives the turbine, leaving at reduced temperature and pressure, condensing in the condenser and combining with liquid from the steam drier as feedwater for recycle to the reactor. 

To obtain the most efficient use of an economizer, studies are needed to balance economizer pressure, condenser pressure and temperature, evaporator surface area, and compression horsepower. These are all interrelated, and horsepower can be saved at the expense of surface areas, and vice-versa. 

High-pressure condensate forms at the same temperature as the high-pressure steam from which it condenses, as the enthalpy of evaporation (latent heat) is transferred from it. When this condensate is discharged through a steam trap to a lower pressure the energy it contains is greater than it can hold while remaining as liquid water. The excess... 

Note that the method described assumes that the high-pressure condensate has not been sub-cooled. If any subcooling has taken place, then the figure taken for the enthalpy of water at the higher pressure is reduced by the amount of sub-cooling. The chart or table can still be used if the upstream pressure is taken as that corresponding to saturated steam at the same temperature as the sub-cooled condensate. 

Somewhat similar arrangements can be used when radiant panels or unit heaters heat large areas. Some 10-15 per cent of the heaters are separated from the high-pressure steam supply and supplied instead with low-pressure steam flashed off the high-pressure condensate. The heating demands of the whole area remain in step, so supply and demand for the flash steam are balanced. 

The purpose of the expansion valve is to control the flowof refrigerant from the high-pressure condensing side of the system into the low-pressure evaporator. In most cases, the pressure reduction is achieved through a variable flow orifice, either modulating or two-position. Expansion valves maybe classified according to the method of control. 

Any pure gas, when cooled sufficiently, will condense to a liquid and then, at a lower temperature, will form a solid. There is great variance in the temperature at which this condensation occurs. Apparently there is a corresponding variance of the forces in liquids and solids. For example, lithium fluoride gas at one atmosphere pressure condenses when cooled below 1949°K. When the temperature is lowered to 1143°K, the liquid forms a clear crystal. In contrast, lithium gas at this pressure must be cooled to 1599°K before it forms a liquid and this liquid does not solidify until the temperature reaches 453°K. The solid is a white, soft metal, not resembling crystalline lithium fluoride at all. Fluorine gas is equally distinctive. At one atmosphere pressure it must be cooled far below room temperature before condensation occurs, at 85°K. Then the liquid solidifies to a crystal at 50°K. Why do these three materials behave so differently Can we understand this great variation Let us begin by finding a common point of departure. 

NOTE Values given are for atmospheric pressure condensation at 100°C. Higher Kb equates to a lower amine dosage. Carbonic acid pKa/pKb values also provided for comparison purposes only. 

Benzene vapour, at atmospheric pressure, condenses on a plane surface 2 m long and I m wide, maintained at 300 K and inclined at an angle of 45° to the horizontal. Plot the thickness of the condensate film and the point heat transfer coefficient against distance from the top of the surface. 

The reactor residence time is about 45 minutes, a 95 per cent approach to equilibrium being achieved in this time. The ammonia is fed directly to the reactor, but the carbon dioxide is fed to the reactor upwardly through a stripper, down which flows the product stream from the reactor. The carbon dioxide decomposes some of the carbamate in the product stream, and takes ammonia and water to a high-pressure condenser. The stripper is steam heated and operates at 180°C, whilst the high-pressure condenser is at 170°C and the heat released in it by recombination of ammonia and carbon dioxide to carbamate is used to raise steam. Additional recycled carbamate solution is added to the stream in the high-pressure condenser, and the combined flow goes to the reactor. 

The product stream leaving the stripper goes through an expansion valve to the low-pressure section, the operating pressure there being 5 bar. In a steam-heated rectifier, further ammonia and carbon dioxide are removed and, with some water vapour, are condensed to give a weak carbamate solution. This is pumped back to the high-pressure condenser. 

Prepare an energy balance diagram for the reactor-stripper high-pressure condenser complex. 

Specify suitable control systems for the maintenance of constant conditions in the reactor against a 15 per cent change in input rate of ammonia or carbon dioxide, and examine the effect of such a change, if uncorrected, on the steam generation capability of the high-pressure condenser. 

The five types Of adsorption isotherms. W, weight adsorbed P/P0, relative pressure. Condensation occurs at PIP0 2 1. 

The water vapor is compressed to its saturation pressure, condensed to liquid, compressed to 0.1 MPa, and finally added to the remaining liquid water inside the bomb. 

When the pressure of the adsorbate in the gas phase is increased to the saturated vapour pressure, condensation occurs on the solid surface and vs/vl approaches infinity. In equation 17.13, this condition corresponds to putting p = 1. It may be noted that putting P = 1/(1 — B2) is not helpful. 

Latent heat associated with phase change in two-phase transport has a large impact on the temperature distribution and hence must be included in a nonisothermal model in the two-phase regime. The temperature nonuniformity will in turn affect the saturation pressure, condensation/evaporation rate, and hence the liquid water distribution. Under the local interfacial equilibrium between the two phases, which is an excellent approximation in a PEFG, the mass rate of phase change, ihfg, is readily calculated from the liquid continuity equation, namely... 

Determine the pump power, turbine power, net power output, rate of heat added to the heat exchanger by surface ocean warm water, rate of heat removed from the heat exchanger by deep ocean cooling water, cycle efficiency, boiler pressure, condenser pressure, mass flow rate of surface ocean warm water, and mass flow rate of deep ocean cooling water. 

Depressurization of the oxidation unit is achieved with the use of a high pressure control valve (Annin Wee Willie). This control valve can be set to operate in any one of three control actions proportional, reset, or derivative. Following the control valve, the hot products are directed to a water cooled high pressure condenser. Here they are cooled to ambient conditions before being sent to a holding vessel for GC andysis. 

Bulk chemical compositions of CAIs, AOAs, and chondrules, compared to trends for calculated total condensed solids formed by equilibrium condensation of a hot solar gas at two different pressures. Condensed minerals are corundum (Cor), hibonite (Hib), end members of melilite series gehlenite (Geh) and akermanite (Ak), anorthite (An), diopside (Di), and forsterite (Fo). Modified from MacPherson etal. (2005). 

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