乙烯裂解炉裂解气在线采样装置开发和应用

Development and application of on-line sampling device for cracking gas in ethylene cracking furnace

关键词:  乙烯  裂解  在线采样  分析  优化 

Key words:  ethylene  cracking  on-line sampling  analysis  optimization

摘要:

目的 进行乙烯裂解炉裂解气在线采样装置开发,得到结构紧凑、气液分离充分、采样分析误差小,可提高裂解气分析准确性的裂解气在线采样装置。方法 分析已有裂解气采样装置的缺点后,确定新开发采样设备应具备全组分采样、气液分离充分、采样和分析误差小、结构紧凑、便于移动、组装检修方便的优点,最终形成两步冷凝、气液分离充分、分析数据真实可靠的裂解气在线采样装置。结果 形成的裂解气在线采样装置在冷凝壳体I和深冷壳体II的体积分别不小于140 L和130 L,在采出裂解气流量为15～25 L/min,采出裂解气出口温度≤550 ℃的条件下,气液分离后气相物料温度≤25 ℃,能实现裂解气的全组分采样,而且气液分离充分。结论 通过开发的裂解气在线采样装置采样分析后,反推出的裂解炉水油比为0.498,与实际操作水油比0.50 非常接近,表明裂解气在线采样装置使用的采样方法和数据处理算法具有很高的科学合理性。应用裂解气在线采样装置对工业裂解炉进行标定,用标定数据指导工业裂解炉出口温度(COT)的优化调控,随COT从845 ℃逐步提升到855 ℃。虽然,丙烯和丁二烯的收率变化不大,但乙烯收率由27.78%提升到30.31%,增加2.53个百分点,效果显著。总体来看,双烯和三烯收率随裂解炉出口温度的提升先略降低而后提高,提高幅度分别达到5.83%和5.42%,有效提高了装置效益。 

Abstract:

Objective sThe on-line sampling device for cracking gas in ethylene cracking furnace was developed, and an on-line sampling device for cracking gas was obtained with compact structure, sufficient gas-liquid separation, and small sampling and analysis error, which can improve the accuracy of cracking gas analysis. Methods After analyzing the shortcomings of the existing cracking gas sampling devices, it is determined that the newly developed sampling device should have the advantages of full-component sampling, sufficient gas-liquid separation, small sampling and analysis errors, compact structure, easy movement, and convenient assembly and maintenance. It is an on-line sampling device for cracking gas with two-step condensation, sufficient gas-liquid separation, and real and reliable analysis data. Results The volume of the condensing shell I and cryogenic shell II of the formed cracking gas on-line sampling device are not less than 140 L and 130 L, respectively, the produced cracked gas flow rate is 15-25 L/min, and the produced cracking gas outlet temperature is not more than 550 ℃, under the above conditions, the temperature of the gas-phase material after gas-liquid separation is not higher than 25 ℃, which can realize the full-component sampling of the cracking gas, and the gas-liquid separation is sufficient. Conclusion sAfter sampling and analysis of the developed cracking gas on-line sampling device, the water-oil ratio of the cracking furnace deduced is 0.498, which is very close to the actual operation water-oil ratio of 0.50, indicating that the sampling method and data processing algorithm used by the cracking gas online sampling device have high performance scientific rationality. The industrial cracking furnace was calibrated by using the on-line sampling device of cracking gas, and the calibration data were used to guide the optimization and control of the outlet temperature (COT) of industrial cracking furnace. With the gradual increase of COT from 845 ℃ to 855 ℃, the yield of propylene and butadiene did not change much, but the ethylene yield increased from 27.78% to 30.31%, with an increase of 2.53 percentage points, and the effect was remarkable. In general, the yield of diene and triene decreased slightly at first and then increased with the increase of outlet temperature of cracking furnace, the increase range reached 5.83% and 5.42%, respectively, which effectively improved the efficiency of the plant.