Stripping steam condensation

Some of the stripping steam condenses in the overhead condenser, shown in Fig. 10.3. The condensed steam, which accumulates in the reflux drum, is totally refluxed back to the top tray of the stripper tower. 

The pressure in the deodorizer is always slighlty higher (0.5-1.5 mbar) than on the suction side of the vacuum unit, because of pressure losses caused by the oil demisters, the fatty matter scrubbers, and other equipment. Consequently, to reach an effective deodorization pressure of 2 mbar, a pressure of not more than 1.5 mbar at the suction side is required. To obtain an efficient steam sublimation at this low pressure, special stripping steam condensers operating at extremely low temperatures (—30°C) are required. (Table 19). 

Neutralizers are injected into the overhead vapor line of the crude tower to maintain the pH value of the stripping steam condensate between 5 and 6. A pH value above 7 can increase corrosion with sour crudes, as weU as fouling and underdeposit corrosion by chloride salt neutralizers. 

Process condensate from reforming operations is commonly treated by steam stripping. The stripper is operated at a sufficiently high pressure to allow the overhead stripping steam to be used as part of the reformer steam requirement (71). Contaminants removed from the process condensate are reformed to extinction, so disposal to the environment is thereby avoided. This system not only reduces atmospheric emissions, but contributes to the overall efficiency of the process by recovering condensate suitable for boiler feedwater make-up because the process is a net water consumer. 

As the organic or volatile material is reduced due to the batch distillation, the steam pressure rises during the progress of the operation due to the loss of the volatile material, and the decrease of pim- When the volatile material is stripped down to a low residual concentration, then Ps approaches the total system pressure, n. When the steam saturation pressure and temperature is greater than 7t, no steam condensation will occur during the operation. 

Most refiners employ continuous water wash as the principal mei of controlling corrosion and hydrogen blistering. The best sourc water is either steam condensate or well-stripped water from a water stripper. A number of refiners use ammonium polysulfat neutralize hydrogen cyanide and to control hydrogen stress crack... 

HPO uses dynamic underground stripping (DUS) technology to inject steam and oxygen into the subsurface. When injection stops, the steam condenses, and contaminated groundwater returns to the heated zone. Chlorinated contaminants in the groundwater mix with the oxygen and condensate and, with the presence of heat, rapidly oxidize into carbon dioxide and chloride. HPO is able to destroy the residual DNAPL components not readily removed by the DUS process. 

The 160°F BFW is efficiently mixed with the incoming steam, in what is effectively a small, vertical stripping tower, mounted above the large deaerator drum. The majority of the steam condenses by direct contact with the 160°F BFW and in so doing, the latent heat of condensation of the steam is used to increase the sensible-heat content of the 160°F BFW to 230°F. 

The stripped 230°F BFW drains into the large deaerator drum. This drum simply provides residence time for the high-pressure BFW pumps, which supply water directly to the boilers. Recovered steam condensate, which should be air-free, is fed to this drum through a separate nozzle. 

A large portion of the stripping steam is used to heat the waste-water feed, shown in Fig. 10.3, from 180 to 230°F. Almost all of this heat comes from the latent of condensation of the stripping steam, and very little of this heat comes from the temperature (or the sensible-heat... 

Many water strippers are initially designed with steam reboilers, rather than with open stripping steam. The amount of steam required is the same in either case. The great advantage of the reboiled stripper is that the steam condensate is recovered, and recycled back to the boilers. When open stripping steam is used, the steam condensate is added to the stripped water, thus increasing the plant s water effluent. Hence, the use of open stripping steam is environmentally unfriendly. 

Note that the collected steam condensate does not pass through the little stripper section. As this stream is just condensed steam, it should be free of air. Hence, it does not need to be stripped. 

Physical Refining. The by-product in the physical refining of crude palm oil is the pahn fatty acid distillate (PFAD). It is obtained as a condensate of the volatile matters carried over from the deodorizer by the action of the stripping steam. It consists of 80-90% of free fatty acid. It has often been used as a raw material for soap making, feed compounding, and oleochemical feedstock. An important and valuable constituent of PFAD is vitamin E in the form of tocopherols and... 

Five or ten trays at the bottom of the column are used for steam stripping the straight-run residue. Because this section is very hot, it is important to ensure that no liquid steam condensate ever enters this section during operation. 

Scheme (1) uses a partial reboiler at the bottom of a plate-type stripping column, generating vapor by the use of steam condensing inside a closed coil. In Scheme (2) the reboiler is omitted and live steam is injected directly below the bottom plate. Determine the number of stages required in each case. 

A mixture of ethylene, high purity oxygen, and recycle gas is reacted in a vertical multitubular reactor filled with silver oxide catalyst. The exothermic heat of reaction is removed by the generation of steam in the reactor shell. The ethylene oxide product is absorbed from the reactor effluent gas with water. It is then recovered from the water stream by steam stripping, partial condensation, and adsorption to form a concentrated aqueous solution. The aqueous solution is further concentrated in a two-stage distillation system. The first-stage separates water and the second removes light ends. 

The vapor leaving the top of the column is condensed in a water- or air-cooled condenser. The liquid distillate is a heavy naphtha stream, which is used for the production of gasoline. It has ASTM 5% and 95% boiling points of 195 and 375 °F, respectively. In some refineries, it is sent to a reforming unit to produce aromatics (benzene, toluene, and xylenes) and hydrogen. The condensed water is decanted off the reflux drum. Note that this water stream is quite large (17,180 Ib/h) because of all the open stripping steam that is used in the column base and sidestream strippers. 

The vapor stream from the meal and oil distillation systems consists of solvent vapor, water vapor (from the stripping steam) and air that has entered the system entrained in the voids of the press cake. Some additional air unavoidably gains entry into the vacuum systems. The vapor stream from the final condenser consists of air saturated with solvent and water vapors. The solvent vapors are selectively scrubbed in a packed tower by a counterflow of special mineral oil. The mineral oil is recycled after being heated, stripped of solvent, and cooled. The hexane vapor remaining in the vent stream should be below the lower explosive limit (1.3% by volume). Nevertheless, overall rapeseed plant losses per tonne flow through the extractor are typically much higher than they are for soybeans. This problem should be researched and, if possible, overcome. 

In the vacuum system described previously, the distilled fatty material is condensed together with the stripping steam in the barometric condenser. Condenser water and condensed vapors are discharged to a basin, which provides a seal against the atmosphere (see Fig. 4). Much of the fatty material floats to the surface in that basin as an emulsion and is skimmed off for recovery. Recovery is done by heating the emulsion in a tank and separating the oily layer by gravity. 

In the partial-recycle process, part of the off-gas ammonia and carbon dioxide from the carbamate strippers is recycled to the urea reactor. Recycling is accomplished by absorbing the stripper gases in a recycle stream of partially stripped urea effluent, in process-steam condensate, or in mother liquor from a crystallization finishing process. In this manner, the amount of NH3 in off-gas is reduced. Any proportion of the unreacted ammonia can be recycled typically, the amount of ammonia that must be used in some other process is reduced to about 15% of that from a comparable once-through unit. 

The key process unit is an FW Evaporative Scrubbing System (ESS). The raw process condensate from the urea unit is first steam stripped to reduce ammonia content. The stripped process condensate is mixed with a circulating stream of urea solution and enters the distribution system of the ESS, which also acts as a cooling tower. The air from the finishing process (prilling or granulation) is introduced into the bottom of the ESS. Particles entrained in the air are dissolved in the urea... 

V/S - 10/(8.33(42)0.15] = 0.191 bbl. steam condensate/bbl. solution. For each mercaptan, values of mr and Ks are read from Figs. 11.5 and 11.6, and the extraction and stripping factors, mrS/G and KsV/Gy calculated. Substitution in Eq. (11.13) permits computation of Xnlxp. The fraction of each mercaptan unextracted multiplied by the fraction of the total mercaptan sulfur each mercaptan represents yields the fraction of the original mercaptan sulfur remaining. The tabulation summarizes the calculations. 

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