Urea and urea production system for absorbing melamine tail gas

The invention relates to the field of co-production of melamine and urea, aims to solve the problem that a low-pressure system and a high-pressure system in a urea production process are difficult to operate stably during co-production of melamine and urea in the prior art, and provides an ammonia gas and melamine tail gas absorption urea production system. Comprising a urea low-pressure system, a medium-pressure decomposition tower and a urea high-pressure system, ammonia and carbon dioxide tail gas generated during melamine production directly enter the urea low-pressure system in a gas phase form to form a low-pressure methylamine solution; the low-pressure methylamine solution is mixed with decomposition gas of the medium-pressure decomposition tower and then enters a medium-pressure methylamine mixer to generate a medium-pressure methylamine solution. The low-pressure methylamine solution is changed into the medium-pressure methylamine solution with higher temperature and lower water content by utilizing