Propane vapor, condensation

Note that the propane vapor is still condensing to propane liquid at 120°F. The condensed liquid is in intimate contact with the propane vapor, as it drips off the outside surface of the colder condenser tubes. The saturated propane vapor condenses directly to saturated propane liquid at 120°F. The saturated, or bubble-point, liquid then drips from the condensation zone of the condenser into the subcooling zone of the condenser. This is the zone where the tubes are submerged in liquid. 

A tube has failed in one of the four condensers about once every three years. If a condenser tube fails, the affected condenser can be removed from service by closing four isolation valves (propane vapor inlet valve), liquid propane outlet valve, cooling water supply valve, and cooling water return valve). However, if a tube fails, it is essential that the operator close the two propane isolation valves before closing the two water isolation valves. Closing the two water valves first would allow pressure to build on the tube side of the condenser and rupture the tube head. 

A.3 Identify all the physical properties and changes in the following statement The camp nurse measured the temperature of the injured camper and ignited a propane burner when the water began to boil some of the water vapor condensed on the cold window. ... 

Recycle designs of this type are limited to applications in which the components of the gas mixture, if sufficiently concentrated, can be separated from the gas by some other technique. With organic vapors, condensation is often possible adsorption, chemical scrubbing or absorption can also be used. The process shown in Figure 8.20 is used to separate VOCs from nitrogen and air or to separate propane, butane, pentane and higher hydrocarbons from natural gas (methane). 

Ethylene-vapor Ethylene vapor Condensate Chilled water Calcium Brine-25% Ethylene liquid Propane vapor Lights chlor. HC Unsat. light HC, CO, CO2, H2 Ethanolamine Steam Steam... 

As soon as the liquid propane is added to the tank, the liquid begins to evaporate. In the closed container, the vapor particles that have escaped from the liquid are trapped. The concentration of propane vapor rises quickly to the concentration that makes the rate of condensation equal to the rate of evaporation, so there is no net change in the amount of liquid or vapor in the tank. There are constant changes (from liquid to vapor and vapor to liquid), but because the rates of these two changes are equal (the rate of evaporation equals the rate of condensation), there is no net change in the system (the amount of liquid and vapor remains constant). Thus the system is a dynamic equilibrium. 

The material distilled in some towers becomes super-corrosive when exposed to moisture. Some depropanizers in sulfuric-acid alkylation service are quite susceptible to moisture-initiated corrosion. One such depropanizer had a long history of corrosion failures. Most frequently, the overhead condenser tubes would start leaking. When this occurred, propane vapors rose from the cooling tower. Often, the effects of corrosion were less subtle clouds of hydrocarbons would burst forth from leaking lines. 

It is obvious that the mols of vapor will increase up the tower, since the steam does not condense under the conditions given, and the propane vaporizes into it as it passes up the tower. This will cause 0/V to vary through the tower, and points on the operating line must... 

If the pipe to the condenser maintained a liquid level, then the shell side of the condenser would be full of propane. But if the shell side of the condenser were really liquid full, the tubes would not contact the vapor. If the tubes do not contact the vapor, then the rate of condensation is zero. Perhaps a small amount of heat transfer would take place, as the liquid propane became subcooled. But none of the propane vapor would condense. 

Natural gas Hquids are recovered from natural gas using condensation processes, absorption (qv) processes employing hydrocarbon Hquids similar to gasoline or kerosene as the absorber oil, or soHd-bed adsorption (qv) processes using adsorbants such as siHca, molecular sieves, or activated charcoal. Eor condensation processes, cooling can be provided by refrigeration units which frequently use vapor-compression cycles with propane as the refrigerant or by... 

Solid-Bed Dehydration. Sihca gel, bauxite, activated alurnina, or molecular sieves can be used for removing dissolved water to meet propane specifications. The soHd-bed dehydrators are used in a cycHc adsorption process. After an adsorption cycle has completed, the bed is heated with a purge gas or a vaporized Hquid-product stream for regeneration. If the latter is used, the Hquid product is condensed, separated from the free water, and returned to the process. After the beds are regenerated, they are cooled and returned to the adsorption cycle. 

Absorption recovers valuable light components such as propane/propylene and butane/ butylene as vapors from fractionating columns. These vapors are bubbled through an absorption fluid, such as kerosene or heavy naphtha, in a fractionating-like column to dissolve in the oil while gases, such as hydrogen, methane, ethane, and ethylene, pass through. Absorption is effectively performed at 100 to 150 psi with absorber heated and distilled. The gas fraction is condensed as liquefied petroleum gas (LPG). The liquid fraction is reused in the absorption tower. 

There is a written procedure for condenser isolation, but it is normally a simple step-by-step task that is second nature to the operator and is performed from memory. However, imder the threat of a potential vapor cloud explosion, the operator may forget to close the propane valves first (Error A). The HEP in Handbook Table 20-7 5 footnote (.01) is increased by a factor of 5 per Handbook Table 20-16 6a to account for stress. 

Thus, if a gas mixture exerts 100 psia total pressure and is composed of 20% by volume (mol%) propane and 80% by volume butane, the partial pressures are 20 and 80 psia for propane and butane, respectively. The liquid in equilibrium with this mixture of vapors would have a lower percentage of propane and a higher percentage of butane. If this mixture is used as a refrigerant, the low-boiling component (propane) reaches equilibrium with a higher concentration in the condenser (as liquid) and increases the total pressure in the condenser. This requires more head and more horsepower at the compressor. 

The vapor composition at the top of the condenser (Y,i) is different from that at the bottom (Y, ). The condenser may be compared to a fractional distillation problem in reverse. Butane, having a higher boiling point, will condense out faster than the propane, although both are condensing at the same time. Thus, the vapor and liquid mol fractions from the top to the bottom of the condenser tube bundle are always changing. Proceed as follows The vapor at the top has the same composition as the gas leaving the evaporator. Therefore, Y,. = Y,. 

The average composition in the condenser (vapor) = 95.7% propane, 4.3% butane, average temp. = 100°F... 

Another item to keep in mind is that if there is any leakage in a system such as this, the leakage will be preferential. For example, a vapor leak in the condenser would leak proportionally more propane than butane. This would change the performance of the cycle considerably. 

A, Find the optimum liquid concentration of the propane isobutane mixture in an auto lefrigerated alkylation reactor. The exothermic heat (10 Btu/h) of the alkylation reaction is removed by vaporization of the liquid in the reactor. The vapor is com pressed, condensed, and flashed back into the reactor through a pressure letdown valve. The reactor must operate at 50°F, and the compressed vapors must be condensed at 110°F. 

The overhead vapor from a depropanizer distillation column is totally condensed in a water-cooled condenser at 120°F and 227 psig. The vapor is 95 mol % propane and 5 mol % isobutane. Its design flow rate is 25,500 lb yh and average latent heat of vaporization is 125 Btu/lb . 

J0. A Cj Splitter column uses vapor reoompression. Bei use of the low temperature required to stay below the critical temperatures of ethylene and ethane, the auxiliary condenser must be cooled by a propane refrigeration system. 

Boiler Thermal Efficiency Traditionally, boiler thermal efficiency is calculated pour/pm, where in is the LHV (lower heating value) of the fuel. A rule of thumb for economizers is that boiler efficiency increases by 1 percent for every 22°C (40°F) drop in temperature of the dry flue gas. These two statements do not reveal the considerable quantity of additional heat, available to be recovered through condensation of the water vapor in the flue gas, which is lost to atmosphere with hot flue gas. Based on fuel HHV (higher heating value), the total latent heat loss can be substantial an additional 9.6 percent (natural gas), 8.0 percent (propane), 6.5 percent (heating ou). 

Straight chain saturated hydrocarbon molecules from propane (C3H8) to octane (CgHis) were deposited from the vapor phase on platinum and silver(l 11) crystal surfaces in the temperature range 100—200 K. The ordered monolayer was produced first and then, with decreasing temperature a thick crystalline film was condensed and the surface structures of these organic crystals were also studied by LEED ... 

Subcooling in a shell-and-tube condensers. Figure 13.3 is the same propane condenser shown in Fig. 13.2. Let s assume that the pressure drop through the shell side is zero. Again, we are dealing with a pure component propane. The inlet vapor is at its dew point. That means it is saturated vapor. Under these circumstances, the outlet liquid should be saturated liquid, or liquid at its bubble point. As the inlet dew-point temperature is 120°F, the outlet bubble-point temperature should be 120°F. But, as can be seen in Fig. 13.3, the outlet shell-side liquid temperature is 90°F, not 120°F. Why ... 

---