**Output Variables**


Data collection/sampling plan: The syngas is collected and analyzed in the areas named U, V, and W.

Design of experiments: The first part of the project is to identify the optimal conditions of two process variables (1) a Mixture of RDF and wood and (2) Equivalence ratios. Syngas' quality typically determines the optimal conditions considering five indicators: carbon conversion, H2/CO ratio, CH4/H2 ratio, gas yield, and gasification efficiency [47]. **Table 3** shows the DoE to determine the best RDF/Wood mixture and ER.


*Application of the Six Sigma DMAIC Methodology to the Gasification Process DOI: http://dx.doi.org/10.5772/intechopen.111850*

#### **Table 3.**

*DoE for best mixture and equivalence ratio.*

#### **4.3 Analyze**

The analysis phase delivers process setup baselines, capability analysis, and identifying sources of variation. So, the first step is to calculate the process's baseline Sigma to understand how well it performs and how much work will be required to reach Six Sigma quality.

#### *4.3.1 Experimental results*

This section presents the gasifier's operating conditions, temperature profiles over time, gas composition (CO, CO2, CH4, and C2H4) profile, and the average gas composition. Finally, the dry gas LHV and efficiency parameters (Ygas, CGE, and CCE) are exhibited. The results are presented in **Table 4** and are discussed below.

#### *4.3.2 Operational conditions*

The pilot-scale gasifier of the University of Aveiro operates under the auto-thermal regime. Therefore, an external heating supply was not necessary. The average temperature was 785°C, sustained by the feedstock's ash fusibility

