Seal pots

In ancient India, a steel called wootz was made by placing very pure kon ore and wood or other carbonaceous material in a tightly sealed pot or cmcible heated to high temperature for a considerable time. Some of the carbon in the cmcible reduced the kon ore to metallic kon, which absorbed any excess carbon. The resulting kon—carbon alloy was an excellent grade of steel. In a similar way, pieces of low carbon wrought kon were placed in a pot along with a form of carbon and melted to make a fine steel. A variation of this method, in which bars that had been carburized by the cementation process were melted in a sealed pot to make steel of the best quaUty, became known as the cmcible process. 

Water may be recycled to two sinks the seal pot and the water-jet compression station. The following constreiints on flowrate and composition of the pollutant (heavy organic) should be satisfied ... 

The gaseous stream exiting the reactor has a flowrate of 0.6 kg/s and contains 600 [ m cresol. It passes through two water scrubbers before it goes Anally to a flare system for burning. To prevent backward propagadon of Are in the flare, water is utilized in a water valve to seal the flare. Water uAlized in scrubber 1 (W ), scrubber 2 (W7), and flare seal pot (Wg) possess the following constraints ... 

Figure 7-70. Suggested seal pot/drum for flare stack system. (See API RP-521, Fig. B-1, 3rd Ed., 1990.) Design adapted with permission by this author from API RP-521, 3rd Ed. (1990) American Petroleum Institute [33].

Two problems arose with the use of the barometric condenser. First, if the condenser operated at subatmospheric pressure, how can the water be drained out of the condenser That is easy. Set the condenser on a hill 34 ft high. Then drain the water down, through a barometric leg, to a seal pot. The pressure which a column of water 34 ft high exerts is equal to one atmosphere, or one bar. Hence the term, barometric leg. ... 

The key to smooth operation of a CFB system is the effective control of the solids recirculation rate to the riser. The solids flow control device serves two major functions, namely, sealing riser gas flow to the downcomer and controlling solids circulation rate. Both mechanical valves or feeders (see Figs. 10.1(a) and (d)) and nonmechanical valves (see Figs. 10.1(b) and (c)) are used to perform these functions. Typical mechanical valves are rotary, screw, butterfly, and sliding valves. Nonmechanical valves include L-valves, J-valves (see Chapter 8), V-valves, seal pots, and their variations. Blowers and compressors are commonly used as the gas suppliers. Operating characteristics of these gas suppliers which are directly associated with the dynamics and instability of the riser operation must be considered (see 10.3.3.2). 

Dilute NHj s oiutioM tank g. Condensate tank k. Cooler i Evaporator k Separator L Seal pot... 

Figure 6-17 Redesigned caustic tank with a properly-engineered seal pot. Courtesy...

The discharge end of the downcomer must project far enough into the tray liquid so that no gas bubbles can enter the open end and bypass the bubble caps. When the liquid contains no sediment, a seal pot or discharge weir is often placed around the discharge end of the downcomer to make certain that no free vapor can enter the open end. The distance between the liquid level on the loaded discharge plate and the bottom of the downcomer when no liquid is flowing is known as the downcomer liquid seal. A downcomer liquid seal, based on a perfectly level tray, in the range of to l in. is usually satisfactory. 

The vacuum at the top of the flash column is often produced by a sequence of three elevated steam-jet eductors with intermediate and final surface condensers to remove the steam. A liquid-ring compressor can be substituted for one or more eductors to conserve steam. Mechanical vacuum pumps are seldom used because of the corrosive nature of the off-gas. The noncondensible sour compressed gas and condensate are led away through a water seal for safety in case of steam system failure. The seal pot is equipped to skim off condensed oil continuously. 

The seal-pot technique has been widely and successfully used. It consists of a closed chamber, half filled with liquid metal and connected by a small line to the point in the piping at which the pressure is being measured. The pressure of the inert gas in the upper half of the vessel is adjusted to balance the liquid metal pressure, so that the level in the chamber is constant. The gas pressure is then measured by conventional means. Proper operation requires that the chamber operate above the oxide saturation temperature of the liquid metal to prevent concentration of oxides in the chamber, and that provision be made to prevent plugging of the gas lines by condensed and solidified sodium. 

Seal pots are optional for any pressure-drop measurement... 

---