Based on the T-H diagram

the gradual optimization integration strategy for a large-scale complex process was proposed.By drawing the T-H diagram of the process

the bottlenecks and unreasonable heat transfer processes were analyzed.Through improving the process

introducing the turbine and heat pump of the system

the hot and cold streams were increased or changed

and the T-H diagram was changed accordingly.Repeating the above steps

two approximate parallel hot and cold stream curves were constructed.Energy was reasonably used

and the consumption of utilities was significantly reduced.In this strategy

energy utilization procedure and conversion procedure were comprehensively considered.By applying this strategy to a methanol to olefins plant

the energy integration of the plant was optimized.The results showed that this strategy was effective and convenient.