Cooling chlorinated condensate

Chlorine at normal temperature and atmospheric pressure is a yellow-greenish gas heavier than air (1 lit. of gas weighs 3.2204 g at 0 °C and 760 inm Hg). When cooled it condenses to form a liquid boiling at —34 °C (at 760 mm Hg) at —102 °C it solidifies into a yellow cristalline substance. The critical temperature of chlorine is 144 °C and the critical pressure 76.1 atm. Chlorine dissolves comparatively well in water, but its solubility is considerably reduced by the presence of sodium chloride. Chlorine dissolves better in organic solvents than in water, e. g. in dichlorethane, carbon tetrachloride etc. 

The process is fed with three streams ethane, ethylene, and chlorine. The ethane and ethylene streams have the same molar flow rate, and the ratio of chlorine to ethane plus ethylene is 1.5. The ethane/ethylene stream also contains 1.5 percent acetylene and carbon dioxide. (For this problem, just use 1.5 percent carbon dioxide.) The feed streams are mixed with an ethylene recycle stream and go to the first reactor (chlorination reactor) where the ethane reacts with chlorine with a 95 percent conversion per pass. The product stream is cooled and ethyl chloride is condensed and separated. Assume that all the ethane and ethyl chloride go out in the condensate stream. The gases go to another reactor (hydrochlorination reactor) where the reaction with ethylene takes place with a 50 percent conversion per pass. The product stream is cooled to condense the ethyl chloride, and the gases (predominately ethylene and chlorine) are recycled. A purge or bleed stream takes off a fraction of the recycle stream (use 1 percent). Complete the mass balance for this process. 

The first step in the gas process is cooling. Direct or indirect exposure to a cooling medium brings the gas to a lower temperature. This incidentally condenses most of the water vapor. The condensate must be treated to remove dissolved chlorine before disposal or return to the electrolysis process. Section 9.1.3 discusses chlorine cooling and condensate handling. 

B. Chlorinated Condensate. An important aspect of chlorine cooling is the composition of the condensate. The water removed from the gas, or in the case of direct cooling of the cooling water as well as that condensed, will be saturated with chlorine. This water is often a process waste, and it must be made innocuous before discharge. Usually, the bulk of the chlorine is stripped from the water after adding acid to reverse its hydrolysis. Hie basics of dechlorination of aqueous streams were covered in the chapter on brine treatment (Section 7.5.9). 

Chlorine Cooling. In Fig. 11.21, wet gas from the cell room is cooled to condense most of its water vapor. This usually takes place in two separate heat exchangers (Section 9.1.3). The cooling water exchanger usually runs uncontrolled, but the temperature of the gas leaving the second cooler is controlled to avoid the problems associated with temperatures that are too low (Section 9.1.3.5A). 

Chlorinated condensate arises in the chlorine cooling system and must be stripped before disposal and even before reuse in the process. A secondary dechlorination may be necessary if the water is to be discarded or transferred to another operating unit. 

The volatile chloride products pass from the chlorinator to a separator unit made of magnesium and attached in the most direct manner possible. This is a box fitted with baffles and maintained at 150 to 180°C for condensation of the ferric chloride (b.p. 315°C) and other less volatile chlorides. From the separator, a simple water-cooled tube condenser leads to a magnesium drum which acts as a receiver for the mixed vanadium tetrachloride and oxytrichloride. Magnesium appears to be an ideal constructional... 

D. 3,3-Diahlarothietane 1,1-dioxide. Thietane 1,1-dioxide (5.0 g, 0.047 mol) Is placed In a 500-mL, three-necked, round-bottomed flask equipped with a reflux condenser, magnetic stirrer, and chlorine gas bubbler. Carbon tetrachloride (350 mL) Is added and the solution Is irradiated with a 250-watt sunlamp (Note 5) while chlorine Is bubbled through the stirred mixture for 1 hr (Note 9). Irradiation and chlorine addition are stopped and the reaction mixture is allowed to cool to room temperature. The product Is collected by filtration as a white solid (4.0-4.4 g, 49-53%), mp 156-158°C (Note 10). The product can be used without further purification or It can be recrystallized from chloroform. 

It is liquefied by conducting the gas through a condenser cooled with ice water. Where difficult to obtain, it may be prepared by passing chlorine gas through a stirred suspension of sodium tetrakis(cyano-C)zincate prepared in situ from sodium cyanide and zinc sulfate. ... 

Three moles of chlorine (212.7 g.) is condensed in a tared flask cooled by a dry ice-acetone bath (Note 4). This flask is then connected to the gas inlet tube of the chlorination apparatus, and the cooling bath surrounding the chlorine container is removed. After about 2 hours the chlorine has all been absorbed by the reaction mixture (Note 5). 

---