Abstract: Taking the design of a 1.50 Mt/a p-xylene (PX) complex in an enterprise as an example, the energy consumption distribution of each unit in the plant and the influence of adopting energy-saving design on the energy consumption of the plant were analyzed, and the importance of improving fuel thermal efficiency and optimizing low-temperature heat utilization scheme to reduce energy consumption of heating furnace was discussed. The results show that the design of heating furnace for the example device based on the “95+” technology is improved, and the waste heat of flue gas to the maximum extent is reclaimed. The thermal efficiency of heating furnace is more than 95%, obviously higher than that of the conventional design(92%), and fuel cost is reduced by 23.4 million Yuan/a. By adopting the low temperature heat generating steam technology, the output of 1.2 MPa and 0.6 MPa steam was 89.2 t/h and 254.2 t/h, respectively. The output of 1.8 MPa steam could be obtained by steam compression and pressurization, which could meet the needs of many steam users. The 110 ℃ hot water quantity was 746.2 t/h by using low temperature heat. The chilled water prepared by advanced hot water refrigeration technology can not only meet the needs of the equipment itself, but also serve many cooling devices. The energy consumption of p-xylene separation unit, xylene isomerization unit and xylene fractionation unit was only 5 190.9 MJ/t by overall optimization design.

Key words: p-xylene, aromatics extraction, isomerization, energy saving