Contact section

A mass transfer device, such as a packed or trayed contact section, should be considered (see Fig. 26-21). 

Mass-Transfer Contact Section Where there is a strong possi-bihty that not all of the incoming vapors will be condensed in the pool, a direct-contact mass-transfer section is superimposed on the quench tank. This can be a baffle-tray section (as shown in Fig. 26-21) or a packed column sec tiou. 

Cyclone Scrubbers The vessels of cyclone scrubbers are all in the form of cyclones, which provide for compact integral entrainment separation. The gas-liquid contacting section normally uses some sort of spray generator to disperse liquid throughout the gas. Performance is similar to other spray scrubbers. 

Queen Maud Range, Thorvald Nilson Mts. (86°7 S., 150°8 W.), Antarctica, Upper Amundsen Glacier area, about 955 ft. above basement contact. Section 7, QM 147 Coll. Jan. 1964, W. E. Long, OSU. 

The flow diagram of the continuous process of converting fatty acids into soap (Fig. 5.1) includes an important component—the hydrolyzer— to which the fats and the catalyst were introduced after mixing and preheating in the blend tank. At the same time, deaerated-demineralized hot water is fed to the top contacting section of the hydrolyzer. The fatty acids are discharged from the top of the splitter and the glycerin is... 

Calculate the final temperature reached when two substances of different mass, heat capacity, and temperature are placed in thermal contact (Section 12.3, Problems 11-16). 

The corporate environmental contacts section identifies the way in which the company facilitates further inquiry. Ideally a number of named HS E contacts, their addresses, telephone numbers and e-mail addresses will be given, and there will be reference to a corporate website. 

Armed Forces Medical Intelligence Center (AFMIC) can provide intelligence about the medical, environmental, and industrial threats in the area of concern. The AFMIC Bulletin Board System (BBS) is an automated online system for the dissemination of unclassified medical intelligence products. This system is designed to provide consumers with timely, user friendly access to AFMIC products. AFMIC also produces the MEDIC CD. (See Points of Contact Section). 

EQUATIONS FOR GAS-LIQUID CONTACTS. Consider the countercurrent gas-liquid contactor shown diagrammatically in Fig. 23.9. Gas at humidity and temperature T j, enters the bottom of the contactor and leaves at the top with a humidity and temperature Liquid enters the top at temperature and leaves at the bottom at temperature The mass velocity of the gas is Gy, the mass of vapor-free gas per unit area of tower cross section per hour. The mass velocities of the liquid at inlet and outlet are, respectively, G a and G t,. Let dZ be the height of a small section of the tower at distance Z from the bottom of the contact zone. Let the mass velocity of the liquid at height Z be G,., the temperatures of gas and liquid be Ty and T, respectively, and the humidity be j/f. At the interface between the gas and the liquid phases, let the temperature be 7j and the humidity be 3 . The cross section of the tower is S, and the height of the contact section is Zj-. Assume that the liquid is warmer than the gas, so the conditions at height Z are those shown in Fig. 23.8a. The following equations can be written over the small volume S dZ. 

Distance from bottom of contact zone, m or ft Zf, total height of contact section... 

Gas Scrubbing and Cooling. If the gas contains fluorine, two scrubbing towers in series may be required to remove the fluorine completely. This step is necessary primarily to protect the catalyst in the contact section of the acid plant. Excess scrubbing liquor from the second scrubber is transferred to the first scrubber, and the weak acid purge from the system is taken from the first scrubber. 

Electrostatic Mist Precipitators. The gas leaving the scrubbers is essentially free of halogens and dust but it still contains acid mist. The amount of acid mist depends primarily on conditions in the smelter. In gas from copper converters, the sulfur trioxide content may vary from 2 to 10% of the total sulfur oxides. The amount of sulfur trioxide formed depends largely on the temperature and time the gas contacts the iron oxide in the dust and the scale on the carbon steel flues. The sulfur trioxide combines with the moisture in the gas to form sulfuric acid vapor. When the gas is cooled in the scrubbers, most of this vapor condenses as a finely divided acid mist, although some of it is absorbed in the scrubber liquor. Sulfuric acid mist, which is generally considered to be particles less than 5 is very difficult to remove from a gas stream, so only a portion of the mist will be removed in the scrubber. If the remaining mist were allowed to enter the contact section of the acid plant it would corrode the carbon steel ducts and heat exchangers and the main blower. It must, therefore, be removed as completely as possible in the purification section of the plant. This is accomplished in the electrostatic mist precipitators. 

The gas leaving the mist precipitators should contain only sulfur dioxide, oxygen, nitrogen, and water vapor, but there will be some traces of impurities which are not harmful to the contact section of the acid plant. 

If the gas has not been adequately cleaned, the contact section of the plant will have continuing operating problems. Improper operation of the mist precipitators will permit acid mist to enter the contact section. This will result in corrosion and sulfate accumulation in the gas ducts, the blower, and the heat exchangers. The corrosion is particularly severe in the heat exchangers because the tube wall temperature, with hot sulfur trioxide gas in the tubes, exceeds 300 °F. The sulfate accumulation on the duct walls is normally not a serious corrosion problem but it eventually breaks loose and is carried onto the catalyst beds in the converter. This sulfate, and also any dust that may pass through the purification section, will gradually blind the catalyst beds. This reduces the conversion efficiency and increases the pressure drop through the plant. 

In the contact section of the plant, the saturated gas is first dried by contact with 93% acid and then the sulfur dioxide in the gas is oxidized to sulfur trioxide. The sulfur trioxide is absorbed in 98% acid where it combines with the free water present to produce additional sulfuric acid. Figure 3 is a typical flow diagram of a double-catalysis sulfuric acid plant operating with sulfur dioxide gas from copper converters. 

There are times during the operating cycle of the copper converter when the oxygen-to-sulfur dioxide ratio is lower than is desirable. During these periods dilution air must be mixed with the gas entering the drying tower of the contact section of the plant to increase its oxygen content. 

Material of construction 304 stainless steel for process contact sections carbon steel for jacket, supports, etc. 

When cold treatment is used to clarify new wines or prevent colloidal precipitation, the installation in Figure 12.1 is most appropriate. It may also be used for tartrate stabilization without contact (Section 1.7.2). The process involves ... 

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