【作者】 闫正兵；

【导师】 吴俊； 刘兴高；

【作者基本信息】 浙江大学 ， 控制科学与工程， 2010， 博士

【摘要】 空分是对空气进行分离,得到氮、氩、氧等高纯工业气体的国民经济重要行业,广泛用于石化、冶金、航空航天等领域。随着经济的发展,空分行业的能耗问题成为该行业进一步发展的瓶颈。内部热耦合精馏是迄今为止所提出的四大精馏节能技术中节能效率最高而唯一没有商业化的节能技术,是国际上精馏节能控制研究的前沿和热点。将内部热耦合精馏技术用于空分塔,将能带来良好的节能效果,但是由于没有有效地掌握内部热耦合技术的特殊稳态特性和动态特性,该技术还没有实现工业化。本文对内部热耦合空分塔(ITCASC)进行了建模和优化研究,分析其稳态特性和动态特性,为ITCASC的控制、设计和实现奠定基础。主要工作及贡献如下：1.建立了ITCASC的平衡级稳态机理模型,进行了自由度分析,给出了有效的求解方法。进行了稳态特性分析和节能分析,研究结果表明,由于内部热耦合的影响,在同样的操作压力下,ITCASC的换热板温差比传统空分塔增加了约1.7K,这意味着ITCASC的高压塔压力可以进一步降低,表明了ITCASC极大的节能潜力。2.为了缩短模型求解时间,进一步建立了ITCASC的混合模型。建立了液相组成、压强和平衡温度的PCA-CGA-RBF统计模型,将泡点法计算平衡温度的时间减少95.36%,而与机理计算结果的平均相对误差仅为0.002%。与机理模型相比较,所建立的混合模型的求解时间从原来的31.06秒减少为11.18秒,模型求解时间减少了64.01%。3.首次建立了ITCASC的稳态扩散双膜非平衡级动态模型。其中,非平衡级模型需要计算大量物性参数,经过系统分析比较,给出了有效的物性计算方法。进一步,对所建立非平衡级动态模型进行了适当的变换,给出了有效的非平衡级动态模型求解算法。研究结果表明,所建立的非平衡级模型可以很好跟踪逼近过程内部特性,在温度、汽液相流量、组分浓度上的预测误差仅为千分级,表明了所建非平衡级动态模型的有效性。进一步,进行了ITCASC动态特性分析,发现了ITCASC过程强烈的反向响应和非对称等非线性特征,可为ITCASC的进一步设计和控制提供指导。4.在所建ITCASC混合模型的基础上,进一步建立了过程的节能优化模型,用序列二次规划算法进行了求解。研究结果表明,高压塔压强可以从原来的590KPa下降为313.74KPa,将比现有的空分塔的较好操作水平节能40%以上,定量揭示了ITCASC的巨大节能潜力。同时,在产品产量和纯度基本不变的情况下,总的加工空气量也减小了,从原加工量的188.1mol/s,降低到最优节能操作工况下的169.76mol/s,这表明ITCASC过程与CASC过程相比,不仅可以大大降低能耗,而且ITCASC过程的产品提取率大大增加,这就意味着ITCASC过程的单位产品能耗与CASC过程相比实际上还进一步降低了。更多还原

【Abstract】 Cryogenic air separation is the distillation process of air to obtain high purity nitrogen, argon, oxygen and other important industry gases, which is widely used in petroleum, chemical, metallurgy, energy, aerospace and beverage and other areas. With economic development, energy consumption of cryogenic air separation industry has become a bottleneck for further development. Internal Thermally Coupled Distillation is the best one out of the four distillation energy saving technologies. Introducing this technology to cryogenic air separation will bring great energy saving effect.The main research works and contributions are listed as following:1. The steady model of internal thermal coupling air separation column (ITCASC) is established. The degree of freedom of the model is analyzed. The analyses of the steady state characteristic and the energy consumption of ITCASC show that the temperature differences of ITCASC increase about 1.7K than the conventional air separation column under the same operation pressure, which reveals that the operation pressure of ITCASC can be further reduced.2. To shorten the computation time for solving the model, a hybird model is proposed for ITCASC. The statistical approach, PCA-CGA-RBF is employed to estable the model of liqud molar fraction, pressure and equilibrium temperature. The computation time of bubble point method decreases 95.36%. And the average relative error is only 0.002%. Compared to the principle model, the proposed hybrid model can decrease the computation time from 31.06s to 11.18s, decreasing 64.01%.3. A non-equilibrium stage dynamic model of ITCASC is proposed first time. After a systematic comparison, the effective methods of calculating the physical properties are explored. With the appropriate segmentation and simplification the proposed dynamic model, an effective algorithm.is given. Simulation studies are conducted to evaluate the obtained results and confirm the validity of the proposed non-equilibrium stage model.4. Based on the hybrid model of ITCASC, an optimization model is established further and solvede. The results show that the high pressure of ITCASC can reduce from 590KPa to 313.74KPa, which means about 40% energy saving. This reveals the huge energy saving potential of the ITCASC. Meanwhile, the flow rate of feed air decreases, from the original 188.1 mol/s to optimal operating conditions 169.76 mol/s, while the flow rate and purity of the product keep almost the same, which reveals that the energy consumption per unit product for ITCASC process can further decrease comparing the CASC process.更多还原