Ammonia and carbon di:oxide recovery from dil. aq. soln. - vaporising soln. and passing gas mixt. in counter flow with wash liquor obtd. by scrubbing carbon di:oxide contg. gas mixt.

摘要

Recovery of ammonia and carbon dioxide which are at least partially bound in the form of urea in a dil. aq. soln., comprises vaporising the soln. and passing the NH3 and CO2 contg. gas stream into a stripping zone in counterflow contact with a soln. obtd. by scrubbing a CO2-contg. gas mixt., and recovering from the stripping zone a soln. contg. mainly ammonia, and a gas mixt. consisting predominantly of the CO2 introduced with the vapour mixt. and with the scrubbing soln. together with water vapour. Pref. (a) the ammonia-contg. soln. from the stripping zone is re-used for scrubbing the CO2-contg. gas mixt. and the ammonia is stripped out of the soln. by the gas mixt. (b) the water is separated from the CO2 in the CO2/water vapour mixt. from the stripping zone by cooling and the water is processed into boiler feed water. (c) the CO2 is separated out of the NH3/CO2 vapour mixt. in the CO2 scrubbing section of ammonia synthesis gas prodn. (d) the ammonia recovered from the dil. aq. soln. is mixed with ammonia synthesis gas.