Steam liquid, mixture

Carbon monoxide has been found to poison cobalt molybdate catalysts. It causes not only instantaneous deactivation but a cumulative deactivation as well. It should be removed from treat gas entirely or at least reduced to a very low value. Carbon dioxide also must be removed since it is converted to CO in the reducing atmosphere employed in Hydrofining. Liquid water can damage the structural integrity of the catalyst. Water, in the form of steam does not necessarily hurt the catalyst. In fact 30 psig steam/air mixtures are used to regenerate the catalyst. Also, steam appears to enhance the catalyst activity in... 

The temperature difference between the exiting vapor-liquid mixture and the inlet shell-side steam or hot fluid should not exceed 75-82°F, primarily due to fouling problems and possible conversion in the tube to inefficient film boiling in the upper section of the tubes. 

Collier, J. G., and D. J. Pulling, 1962, Heat Transfer to Two-Phase Gas-Liquid System, Part II, Further Data on Steam-Water Mixtures in the Liquid Dispersed Region in an Annulus, UK Rep. AERE-R-3809, Harwell, England. (4)... 

Era, A., G. P. Gaspari, A. Hassid, A. Milani, and R. Lavattarelli, 1966, Heat Transfer Data in the Liquid Deficient Region for Steam-Water Mixtures at 70 kg/cm2 Flowing in Tubular and Annular Conduits, Rep. CISE-R-184, Milan, Italy. (4)... 

Since cmcible failures have occurred in numerous instances in the industry—with minor steam explosions, the violence of the event described above is believed to be due to the electrode falling into the water-metal mixture. Somehow, the steam-liquid water-molten titanium mixture changed character from a relatively slow increase in pressure to a sharp shock wave. 

In order to achieve the isothermal heat addition and isothermal heat rejection processes, the Carnot simple vapor cycle must operate inside the vapor dome. The T-S diagram of a Carnot cycle operating inside the vapor dome is shown in Fig. 2.2. Saturated water at state 2 is evaporated isothermally to state 3, where it is saturated vapor. The steam enters a turbine at state 3 and expands isentropically, producing work, until state 4 is reached. The vapor-liquid mixture would then be partially condensed isothermally until state 1 is reached. At state 1, a pump would isentropically compress the vapor-liquid mixture to state 2. 

Visual deflnitions of flow patterns in vertical flow appear to cause more diflBculty than do those in horizontal flow. As the gas rate increases at a constant liquid rate, a dispersed type of flow will be reached at lower gas velocities in a vertical tube than in a horizontal one because of the influence of gravity in causing back flow of liquid. Also, vertical flow patterns tend toward radial symmetry, which is not the case in horizontal flow. A classification of vertical flow patterns based largely on air-water mixtures is given below. Surprisingly little work has been carried out for the vertical upward flow of components other than these, or steam-water mixtures. 

The most widely used is ammonia absorption in water. A flowsketch of the process is in Figure 8.27. Liquid ammonia at a high pressure is obtained overhead in a stripper, and then is expanded through a valve and becomes the low temperature vapor-liquid mixture that functions as the refrigerant. The low pressure vapor is absorbed in weak liquor from the bottom of the stripper. Energy input to the refrigeration system is primarily that of the steam to the stripper reboiler and a minor amount of power to the pump and the cooling water circulation. 

Stripping a means of separating volatile components from less volatile ones in a liquid mixture by the partitioning of the more volatile materials to a gas phase of air or steam (q.v. stabilization). 

For instance, Van Laar s equation for the coefficient of activity of binomial mixture or the steam-liquid balance, is nonlinear by coefficients A and B, as shown in the equation. 

About 1837, F. Mohr separated the bromine in the mother liquids of salt springs by treating them with pyrolusite and sulphuric or hydrochloric acid. He showed that at least 5 per cent, of acid must be present or an appreciable amount of bromine will not be formed. The raw material now employed is carnallite, which contains from 0 25 to 0 42 per cent, of bromine. The mother liquid remaining after the separation of the potassium chloride from carnallite contains from about 0 15 to about 0 25 per cent, of bromine in the form of bromocarnallite. In A Frank s first process 3 the bromine was obtained by mixing the mother liquid with sulphuric acid and manganese dioxide, and heating the mixture by blowing in steam. The mixture of steam, bromine, and chlorine was cooled in a spiral tube. The condensate... 

Due to the much greater volume of flash steam compared with unflashed condensate, sizing of the return line is based solely on the flash steam. It is assumed that all flashing occurs across the steam trap and that the resulting vapor-liquid mixture can be evaluated at the end-pressure conditions. To ensure that the condensate line does not have an appreciable pressure-drop, a low flash-steam velocity is assumed (50 ft/s) [i]. 

Hs = Total enthalpy of steam, Btu/lb mol, or Btu/lb HK = Heavy key component in volatile mixture h = Enthalpy of liquid mixture or pure compound at tray conditions of temperature and pressure, or specified point or condition, Btu/lb mol, or Btu/lb... 

Results by Chenoweth and Martin (Pet. Refiner, 34[10], 151-155 [1955]) indicate that single-phase data for fittings and valves can be used in their correlation for two-phase pressure drop. Smith, Murdock, and Applebaum ( J. Eng. Power, 99, 343-347 [1977]) evaluated existing correlations for two-phase flow of steam/water and other gas/liquid mixtures through sharp-edged orifices meeting ASTM standards for flow measurement. The correlation of Murdock (J. Basic Eng., 84,419-433 [1962]) may be used for these orifices. See also Collins and Gacesa (/. Basic Eng., 93, 11-21 [1971]), for measurements with steam and water beyond the limits of this correlation. 

Liquid temperatures in the tubes of an LTV evaporator are far from uniform and are difficult to predict. At the lower end, the liquid is usually not boiling, and the liquor picks up heat as sensible heat. Since entering liquid velocities are usually very low, true heat-transfer coefficients are low in this nonboiling zone. At some point up the tube, the liquid starts to boil, and from that point on the liquid temperature decreases because of the reduction in static, friction, and acceleration heads until the vapor-liquid mixture reaches the top of the tubes at substantially vapor-head temperature. Thus the true temperature difference in the boiling zone is always less than the total temperature difference as measured from steam and vapor-head temperatures. 

The following property data are given for water at the saturation temperature of 100 °C liquid density gL = 958.1 kg/m3, vapour density go = 0.5974kg/m3, enthalpy of vaporization Ahv = 2257.3 kJ/kg, liquid thermal conductivity Al = 0.677 W/K m, dynamic viscosity of the liquid pl = 0.2822 10 3 kg/s m, specific heat capacity of the steam-air mixture cpg = 1.93kJ/kgK. Further, the heat transfer coefficient between the steam-air mixture and the condensate film is = 30W/m2K. 

---