大型对二甲苯装置的节能设计与优化

以某企业1.50 Mt/a对二甲苯装置的设计为例，综合分析该装置中各单元的能耗分布及采用节能设计对装置能耗的影响；结合对二甲苯装置的特点，深入探讨提高加热炉热效率、优化低温热利用方案等措施对降低装置能耗的重要性。结果表明：举例装置基于“95+”的技术改进加热炉设计，最大限度地回收烟气余热，使加热炉热效率超过95%,明显高于常规设计值(92%),可节省燃料费用2 340万元/a;通过采用低温热发生蒸汽技术，1.2 MPa蒸汽产出量为89.2 t/h, 0.6 MPa蒸汽产出量为254.2 t/h,而且余热采用蒸汽压缩可得1.8 MPa蒸汽，满足多个蒸汽用户需求；通过采用低温热制热水，可得110℃热水约746.2 t/h,采用先进热水制冷等技术制备的冷冻水除满足装置自身需求外，还可服务多个用冷装置；通过整体优化设计，使对二甲苯分离、二甲苯异构化、二甲苯分馏等单元的产品能耗仅为5 190.9 MJ/t,与同类装置相比大幅降低，达到国内领先水平。

OPTIMIZING DESIGN OF LARGE PX COMPLEX FOR ENERGY SAVING

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.