## 3 Results and Discussion
### Case Study A: Hybridization with an ICE (Internal Combustion Engine) Fed with External Fuel  
In this case study (Figure 3), the feed heating to the reaction temperature is reached using exhaust gas and cooling water from an ICE fed with external fuel. Instead, the hot effluent leaving the reactor is used for energy recovery (Organic Rankine Cycle or Vapor Rankine Cycle), and a syngas fuel stream is available for other uses. Configuration parameters of ICE [55] were selected considering the thermal power required to heat the feed stream from ambient to the reactor inlet temperature. Exhaust gas has a temperature between 450 \({}^{\circ}\)C and 550 \({}^{\circ}\)C that will allow a maximum temperature of approximately 530 \({}^{\circ}\)C at the reactor inlet (considering 20 \({}^{\circ}\)C as the minimum pinch  
Figure 7: **(a)** Hydrogen flowrate in the gas stream. **(b)** Methane flowrate in the gas stream. **(c)** Carbon monoxide flowrate in the gas stream. Figures are parametrized as functions of glycerol mass concentration in the feed stream and flowrates are represented versus the reactor inlet temperature in the range from 450 to 600 \({}^{\circ}\)C.  
point temperature). Thus, considering an exhaust gas temperature of 550 \({}^{\circ}\)C, the required flowrate will vary depending on the operating conditions (different glycerol concentration in the feed stream and temperature at the reactor inlet). For each operating case, the selected ICE will generate the exhaust gas flowrate needed to supply the thermal power demanded by the feed stream. In addition, the cooling water stream coming from the ICE refrigeration is also available with a flowrate from 10 to 23 m\({}^{3}\)/h and a temperature of 90 \({}^{\circ}\)C. Both streams, exhaust gases and cooling water coming from ICE, are used as hot fluids in the heat exchangers (first and second preheaters) to increase the feed temperature. Taking into account the performance of an ICE in combined heat and power mode, the thermal power of exhaust gases is used to preheat the feed stream process at the same time that the mechanical power generated is also available for electricity generation. For the first preheater, the cooling water coming from ICE cooling is used as the hot countercurrent fluid in a tube and shell heat exchanger. According to the ICE manufacturer's data [55], the maximum temperature in the hot stream is limited to 90 \({}^{\circ}\)C, therefore, the design of the equipment is carried out by imposing that the cold fluid is heated up to 85 \({}^{\circ}\)C as the maximum temperature (considering the minimum pinch point temperature at 5 \({}^{\circ}\)C). The outlet temperature of the hot fluid only decreases a few Celisius degrees because of the high flowrate of cooling water used in the selected ICE. Regarding the thermal power required for each glycerol concentration, the values are similar, since there is a small variation in the heat capacity of the water-glycerol mixture, ranging from 65.25 kW for 10 wt.% glycerol (mixture heat capacity 4.11 kJ/kg K at 85 \({}^{\circ}\)C) to 64.90 kW when the glycerol concentration is 30 wt.% (mixture heat capacity 4.05 kJ/kg K at 85 \({}^{\circ}\)C). The calculated area of the heat exchanger is almost constant, varying from 3.51 to 3.54 m\({}^{2}\) for the analyzed conditions. In the second preheater, exhaust gas generated in the ICE is used as countercurrent hot fluid in a tube and shell heat exchanger. Considering a maximum temperature in this stream of 550 \({}^{\circ}\)C, the cold stream will be heated from 85 \({}^{\circ}\)C, achieved after leaving the first preheater, to 530 \({}^{\circ}\)C (considering the minimum pinch point temperature in 20 \({}^{\circ}\)C). Figure 8a shows the thermal energy exchanged between the exhaust gases and the feed stream. Figure 8b depicts the exhaust gas flowrate required to supply the energy needed to reach the reactor inlet temperature. As expected, an increase in the demanded thermal power leads to an increase in the required exhaust gas flowrate.