# Design of Pyrolysis Plant for Waste Methyl Ethyl Ketone from the Polarizer Manufacturing Process
## 3 Results and Discussion
### Field System  
The field system was designed using SolidWorks, as shown in Figure 12. The design concept of the scaled-up system closely resembled that of the lab-scale reactor, with the main modifications being the adjustment of the spiral width and reactor volume to accommodate the difference in flow rate. The spiral width was kept fixed to prevent carbon accumulation near the inner tube during thermal decomposition. A larger space height could result in lower velocity and reduced heat transfer efficiency, as the energy transferred from the outer barrel wall may be compromised [28]. The pitch of the spiral remained fixed to meet the heat transfer requirements, with a furnace heat capacity of 66 kW and the reactor constructed using SUS 310 material. The design followed ASME VIII July 2017 standards, with a maximum allowable pressure of 1.8 kg/cm\({}^{2}\) at 900 \({}^{\circ}\)C. The 3D model during the design process is shown in Figure 12b. The heat transfer coefficient for the liquid-gas reaction was estimated based on previous works to be in the range of 30-120 W/m\({}^{2}\)/K [20]. The kinetic data used for design were obtained from [PERSON] and [PERSON]'s research [9], with frequency factor and activation energy of 1.21 \(\times\) 10\({}^{15}\) and 67.2 kcal/mol, respectively, to determine the required reaction volume. The Aspen Plus PFR model with the non-random two-liquid (NRTL) thermodynamic model was used to calculate the heat of vaporization and correct the phase equilibrium at 1.0132 bar, as shown in Figure 13a, with regression based on actual experimental data [29]. The detailed calculations of the reaction phenomena in the various parts of the reactor are shown in Figure 13b, which includes three zones: (1) MEK vaporization zone, (2) cracking zone, and (3) stabilization zone. The first 0.5m is mainly for solvent gasification, with a requirement of at least 3.6 kW of heat and a temperature of approximately 525 \({}^{\circ}\)C. As the temperature rises, the solvent undergoes thermal cracking in the 0.5 to 2 m stage, with the temperature reaching 700\({}^{\circ}\)C. The design of the reaction zone ranging from 2 to 2.5 m is primarily intended for safety spare considerations. The entire process requires approximately 24 kW of energy consumption in this theoretical calculation. The capacity of the field system, as shown in Figure 12a, was designed to handle approximately 15 tons of MEK per month. SUS 310 material with a thickness of about 10 mm and a body height of 2300 mm was used for the reactor. The practical volume of the reactor was approximately 163 L. The residence time, which varied depending on the flow rate of MEK ranging from 100 to 450 mL/min, was calculated to be around 4.7 to 19.2 s using the previously mentioned equation (Equation (13)). The heat exchanger, which incorporated a solid-gas cyclone shown in Figure 12c. The sizing of the heat exchanger was estimated using Aspen Plus EDR. The target cooling temperature was set at approximately 45 \({}^{\circ}\)C for burner-friendly use. The heat-exchanger zone was composed of 163 branches of an 800 mm steel tube, providing a total heat-exchange area of approximately 13.83 m\({}^{2}\). The cyclone was positioned in front of the tube bundle to allow particles larger than 50 \(\upmu\)m to settle in the collection box, thereby minimizing fouling effects at the heat-exchange zone and ensuring long-term operational convenience. The entire system in the factory, as depicted in Figure 14, shows promising results in terms of meeting the required capacity of the reaction zone. However, it is important to consider engineering amplification factors to account for process instability. The char kinetic parameters related to temperature exceedance were not fully consistence with the previous design. Nevertheless, the results obtained were reliable and will provide a basis for scaling up a stable system. The pyrolysis temperature of MEK falls within the range of 540-630 \({}^{\circ}\)C [10].