The invention discloses a utilization method for
waste heat and excess pressure of a gas
fractionation apparatus. According to the method, a
material flow from the bottom of a propylene
tower and a saturated solution from a working medium pump are mixed and then undergo heat exchange in a low temperature
waste heat exchanger; obtained steam and low
pressure injection steam are introduced into an
injector; deceleration and pressurization are carried out by the
injector so as to obtain medium-pressure overheated steam which enters into a circulating water condenser or an air cooler for condensation into a medium-pressure saturated solution; one part of the medium-pressure saturated solution is pressurized by the working medium pump to a pressure which is same as the pressure at the bottom of the propylene
tower and is then mixed with the
material flow at the bottom of the propylene
tower, and an obtained mixture is sent back to the low temperature
waste heat exchanger for cyclic usage; the other part of the medium-pressure saturated solution is converted into a medium-pressure supercooled
liquid phase by a circulating
water cooler and then divided into two paths, wherein one path of the medium-pressure supercooled
liquid phase is discharged as a product from a
system, and the other path of the medium-pressure supercooled
liquid phase is throttled and decompressed by a
thermal expansion valve so as to obtain a cold source which is used for cooling a
material flow at the top of a deethanization tower, a material flow at the top of the propylene tower and
refrigerant water. With the method provided by the invention, waste heat and excess pressure of the material flow at the bottom of the propylene tower are fully used, operation stability of the propylene tower is improved, and product quality is guaranteed.