**Acknowledgements**

The feedstock composition and operating conditions, except COT, were fixed. However,

Accumulate coke thickness in each period was related to the operating conditions of all previous periods. Eq. (23) is simplified as eq. (22) to make the model easier to regress and the error caused by the simplification is acceptable according to the error shown in Table 5.

> **Serial (wt %)**

*dtt t d d f t COT COT COT* <sup>+</sup><sup>1</sup> = ( 1 2 ,L L , *<sup>t</sup>* ) "*t N* Î= {1,2,, , -- 1, } (23)

**COT C2H4 C3H6**

**Parallel (wt %)**

 872.00 872.00 0.00 32.13 32.13 0.01 16.54 16.54 0.00 872.00 872.00 0.00 32.22 32.24 0.05 16.55 16.55 0.00 872.00 872.00 0.00 32.31 32.36 0.14 16.57 16.57 0.01 872.00 872.00 0.00 32.42 32.48 0.21 16.59 16.59 0.02 872.00 872.00 0.00 32.56 32.65 0.27 16.58 16.56 0.14 872.00 872.00 0.00 32.70 32.84 0.44 16.55 16.49 0.34 870.58 871.38 0.09 32.84 33.02 0.54 16.46 16.40 0.34 865.58 866.38 0.09 32.89 33.07 0.54 16.31 16.22 0.52 860.58 861.38 0.09 32.98 33.09 0.35 16.11 16.04 0.39 855.58 856.38 0.09 33.11 33.09 0.04 15.87 15.88 0.07

error - - 0.04 - - 0.26 - - 0.18

A multi-scale steam cracking model was established in this chapter. An elementary reaction network was generated to obtain a more accurate and robust model. The results showed that the established multi-scale model agrees well with the industrial data. A surrogate coke thickness model is thus proposed to make multi-period optimization with parallel simulation possible. A case study showed that multi-period optimization with parallel computing possesses an 8.55 x speedup compared to optimization with serial simulation. Parallel computing makes real-time optimization (RTO) possible in multi-period optimization. The average error of optimization using a parallel simulation model was 0.04% compared to optimization using a serial model. The error was deemed acceptable for the optimization of

**Error (%)**

**Serial (wt %)**

**Parallel (wt %)**

**Error (%)**

d

138 Advances in Petrochemicals

**Period Serial (°C)**

Average

**4. Conclusion**

**Parallel (°C)**

**Error (%)**

**Table 5.** Summarized optimization results for serial and parallel calculation.

large-scale industrial steam cracking processes.

The authors gratefully acknowledge the financial support of the National Basic Research Programme (No. 2012CB720500) and the NSFC (No. 21306100).
