Atmospheric pressure flash separator

The carbonylation reaction takes place at 160°C and 7.106 Pa absolute. Dinitroto-luene conversion is virtually complete, for a residence time of 21/2 hours. After cooling to 60°C, the effluent obtained is flashed. The C02 formed is extracted by diethanolamine, and excess CO is recycled. The liquid fraction is filtered to remove the catalyst Distillation is then practised at atmospheric pressure to separate the alcohol (methanol), followed by the carbamate, which is decomposed under vacuum in a series of three reactors, around 250 C, in the presence of zinc naphtbenate as catalyst. 

The liquid from the high pressure separator was depressured and flashed at atmospheric pressure. The... 

The liquid stream passes a separator (2), then a let-down valve (3) for pressure release, and enters a flash evaporator (4) where the major part of inerts and unconverted reactants is taken overhead. The flashed-off gases are compressed and returned to the reactor, whereas the liquid is heated and fed to a first distillation column (5), from which vaporized aldehydes are taken as head stream. As the bottoms still contain aldehydes, a second distillation column (6) with sub-atmospheric pressure is required to concentrate the catalyst solution. The gaseous aldehydes from both units are condensed and sent to the upgrading section the separated gases (7) are recycled (after compression) or vented. In order to limit... 

C02 can be separated from the shifted syngas stream in a Selexol type of absorber. Multistage flash drums can be used to extract C02 from absorbed solvents at various pressure levels typically ranging from atmospheric pressure to 400 psi. The C02 product stream is usually compressed to high pressure (llObar) for geologic storage or enhanced oil recovery. 

The latter operation takes place around 110 0, at 12.10 Pa absolute, in the presence of precompressed air. By flashing at 0.15.10 Pa absolute, the off-gases are separated from the catalyst system, which is sent to the oxidation reactor after the addition of make-up hydrochloric arid and chlorides to offeetluiy losses. The organic compounds, including acetone, stripped in the gas phase, are recovered by water scrubbing in an absorption column operating at atmospheric pressure around 50°C, and recycled with the catalyst solution. 

Problem 8.8 Two flash separators in series operate at 1 atmosphere total pressure. The feed (K) into the first drum is a binary mixture of methanol/water that is 55 mol % methanol with flow rate 10,000 kg moles/h. The second flash drum operates at temperature, Ta and the liquid product composition (xj is 15 mol % methanol. 

The liquid ammonia from the separator contains a small amount of dissolved gases. These are partly released by pressure reduction in a iet-down vessel normally to about 2.5 MPa. After the let-down vessel the ammonia is further flashed to almost atmospheric pressure before being sent to the ammonia storage tank. In order to reduce the risk of stress corrosion cracking in the ammonia storage tank, the ammonia product should contain minimum 0.2% of water. 

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