Water-removal trays

Many columns have water removal trays designed into the column. Top or bottom temperatures may have to be changed to expel the water if the column isn t provided with water removal trays. In some instances, the water can be expelled by venting the column through the safety relief system. 

Determine How much water is removed from the overhead accumulator and the intermediate dehydrator or water removal tray No water is removed from the bottoms due to the use of superheated steam. 

TEG RATE, GAL/LB WATER REMOVED Figure 8-13. Glycol concentration vs. glycol circulation when n = 1 theoretical tray. 

Davey A modification of the Parkes process for removing silver from lead. A water-cooled tray is floated on the molten lead. Invented by T. R. A. Davies in 1970 and operated by Penarroya in Brazil, France, Greece, and Spain. 

Carbon dioxide removal in ammonia plants is usually accomplished by organic or inorganic solvents with suitable activators and corrosion inhibitors. In a few circumstances, C02 is removed by pressure swing adsorption (PSA) (see Chapter 3). The removed C02 is sometimes vented to the atmosphere, but in many instances it is recovered for the production of urea and dry ice. Urea is the primary use of carbon dioxide and, in case of a natural gas feed, all of the C02 is consumed by the urea plant. This practice is especially significant since C02 is a proven greenhouse gas. Typically, 1.3 tons of C02/ton of NH3 is produced in a natural gas-based ammonia plant. The C02 vented to the atmosphere usually contains water vapor, dissolved gases from the absorber (e.g., H2, N2, CH4, CO, Ar), traces of hydrocarbons, and traces of solvent. Water wash trays in the top of the stripper and double condensation of the overhead help to minimize the amount of entrained solvent. The solvent reclaimer contents are neutralized with caustic before disposal. Waste may be burned in an incinerator with an afterburner and a scrubber to control NOx emissions. 

After the hydrogen b removed by flash, the separation treatment comprises a series of five distillation columns which separate in succession the light compounds (15 trays), water (45 trays), heavy compounds (20 trays), butanediol (40 trays), and recover the product carried off in the heavy fractions (25 trays). The total hydrogenation yield is 95 molar per cent for butanediol for virtually total butynediol conversion. 

In services using water-cooled condensers, a tube leak can lead to water being refluxed into the coliunn. In one case (358), this caused a pressure surge and severe tray damage. The effect of a condenser tube leak should be examined if a pressure surge may result, water removal facilities should be provided at the reflux drum. 

Because of this limitation, drying rates attainable in practice are much below the maximum rates attainable with ice. Thns, for materials loaded into the freeze dryer at abont 8-18 kg/m of tray surface, which corresponds to indnstrial practice [1], average drying rates are of the order of 1.5 kg of water removed... 

Insufficient absorption or off-specification for exit scrubbed gas feed gas concentration off spec/feed gas temperature or pressure outside operating window for amine absorbers > 50 °C for H2S and < 24 °C for C02/feed gas pressure has de-creased/[solvent flowrate too low] for glycol dehydration 12.5 to 25 L TEG per kg water removed/[solvent incorrect] /incorrect feed tray location/[column operation faulty] /absorber operating conditions differ from design/[absorber malfunction]. ... 

Next, use a valve (Pressure ChangelValve) to flash the liquid product from the drum to a specified pressure of 3.44 bar. Add a distillation column block (via Col-umnlDistillation) to facilitate water removal from the product leaving the flash valve. Use 12 theoretical stages, a condenser, and a reboiler. Note that when you first create the block, the popup window asks for a number of theoretical trays. However, this is a misnomer, because it counts the condenser and reboiler as theoretical trays. Once you double-click the column to open the specifications form, you can visually verify that there are 12 stages identified. Once you have made the block, add mass streams for the bottoms and distillate and be sure to coimect the distillate stream to the vapor port (so you will have a partial condenser). Specify the top tray as 3.44 bar with no pressure drop in the column in the Pressure Profile tab. Be sure to increase the number of iterations from the default 15 to about 100 (15 is not likely to be enough). Next, in the Feeds and Products tab, select the feed to tray 5 with the feed convention sent to Flash the feed adiabatically..This means that, because the feed is a mixture of vapor and liquid, the vapor portion rises to the tray above (4) and the liquid... 

Water entrained in the stripper feed is not properly removed at the water drawoff tray. (See Fig. 20—3 for details of a water drawoff tray.)... 

Reaction times can be as short as 10 minutes in a continuous flow reactor (1). In a typical batch cycle, the slurry is heated to the reaction temperature and held for up to 24 hours, although hold times can be less than an hour for many processes. After reaction is complete, the material is cooled, either by batch cooling or by pumping the product slurry through a double-pipe heat exchanger. Once the temperature is reduced below approximately 100°C, the slurry can be released through a pressure letdown system to ambient pressure. The product is then recovered by filtration (qv). A series of wash steps may be required to remove any salts that are formed as by-products. The clean filter cake is then dried in a tray or tunnel dryer or reslurried with water and spray dried. 

Burning Pyrites. The burning of pyrite is considerably more difficult to control than the burning of sulfur, although many of the difficulties have been overcome ia mechanical pyrite burners. The pyrite is burned on multiple trays which are subject to mechanical raking. The theoretical maximum SO2 content is 16.2 wt %, and levels of 10—14 wt % are generally attained. As much as 13 wt % of the sulfur content of the pyrite can be converted to sulfur trioxide ia these burners. In most appHcations, the separation of dust is necessary when sulfur dioxide is made from pyrite. Several methods can be employed for this, but for many purposes the use of water-spray towers is the most satisfactory. The latter method also removes some of the sulfur... 

Knox has provided the following graphs for estimating the required vent steam from boiler feedwater deaerators. Vent steam rate depends upon the type of deaerator (spray or tray type) and the percentage of makeup water (in contrast to returning condensate). Low makeup water rates require relatively lower steam vent rates, but there is a minimum rate required to remove CO2 from the returning condensate. 

In one process the naphtha fraction boiling between 160 and 180°C is washed with caustic soda to remove the acids and then with suilphuric acid to remove basic constituents such as pyridine and quinoline. The naphtha is then frozen to remove naphthalene, and agitated with sulphuric acid, then with caustic soda and finally with water. Concentrated sulphuric acid is then run into the purified naphtha at a temperature below 0°C. The reaction is stopped by addition of water after 5-10 minutes, any sediment is removed, and the solution is neutralised and then washed with water. Residual naphtha is distilled off under vacuum, leaving behind the resin, which is run into trays for cooling. 

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