The invention provides a
system for concentrating
wastewater by heating via low-temperature
flue gas. Multi-grade flashing is realized by using gradient vacuum through a flash tank, so that the
concentration effect of desulfurization
wastewater is increased; meanwhile, steam with different temperature, formed by the multi-grade flashing, enters communicated sub shell sides respectively, and is subjected to cascaded heat exchange with a secondary heat exchange medium, so that the heat exchange effect is improved; a second
heat exchanger is of a tube-shell type structure, and a plurality of subshell sides are adopted, so that the complexity of the structure of the second
heat exchanger and the connection of the shell sides is reduced while the condensation effect of the steam can be improved, and furthermore, the
investment cost and construction period of
system equipment are reduced; after the temperature of the
wastewater is improved, the residual heat of the
flue gas participates inwastewater flashing; and then the residual heat of the
flue gas is further recycled by the second heat exchange medium after being brought out by the steam, and then returns to a low-temperature
heating system. In the case that recycled heat is nearly not lost, the application of the heat is widened, and cascaded utilization of the heat is realized; and the
disadvantage of a conventional
route that high-quality heat is consumed is overcome and the
energy consumption of units is reduced.