This study had compared raw biomass and pre-treated biomass co-gasified with coal with the aim of investigating the reliability of pre-treated biomass for enhancing gasification performance. Sawdust (SD) and wood pellet (palletisation form of sawdust - WP) and blends of these two feedstocks with sub-bituminous coal (CL), were gasified in an air atmosphere using an external heated fixed-bed downdraft gasifier system. Response surface methodology (RSM) incorporating the central composite design (CCD) was applied to assist the comparison of all operating variables. The three independent variables were investigated within a specific range of coal blending ratios from 25% to 75%, gasification temperature from 650 Celcius to 850 Celcius and equivalence ratio from 0.20 to 0.30 against the dependent variables, namely the H2/CO ratio and higher heating value of the syngas (HHVsyngas). The results revealed the H2/CO ratio and a higher heating value of the syngas of more than 1.585 and 6.072 MJ/Nm3, respectively. Findings also showed that the H2/CO ratio in the syngas from CL/WP possessed a higher value than the CL/SD. In contrast, CL/SD possessed a higher heating value for syngas with about 1% difference compared to the CL/WP. Therefore, co-gasified coal with wood pellets could potentially be a substitute for sawdust.

---

The CL/SD and CL/WP blends were used as feedstock in this study. The CL was obtained from an electric utility company in Malaysia through a third-party company. Meanwhile, the SD and WP were obtained from a wood industry company located in Penang, north of Malaysia. Both SD and WP are recognized as the by-product of woodworking operations and pre-treated sawdust in a pelletized form. Fig. 1 shows the images of CL, SD and WP. Both CL and SD were received in powder form, whileWP was in solid form. The dimensions of the feedstock were determined by using the Brunauer-Emmett-Teller (BET) the-ory and the Malvern particle sizer model. The feedstock was received prior to the day of the experiment from a local sup-plier. The feedstock was prepared for investigating the texture, structure and chemical properties of CL, SD and WP aswell as corresponding co-gasi?cation experiments. Sampleswere ?rst weighed to obtain the required mass neededthroughout the experiment. Next, samples were dried in anoven at a temperature of 105 Celcius for about 24 h. The mainpurpose of the drying process was aimed at removing most ofthe moisture in the samples. Subsequently, samples weremechanically mixed into different blending ratios (25%, 50%,and 75%). Then, the dried samples were placed into an air-tight container to avoid any moisture coming in contactwith the samples. The properties of the feedstocks weredetermined by a proximate analysis as per the ASTME1131 procedure using a thermogravimetric analyser (Hitachi STA7000), ultimate analysis as per the ASTM D3176 procedureusing an elemental analyser (Elementar: vario MACRO cube),and higher heating value (HHV) using a bomb calorimeter (IKAC200).

---

Temperature and Gasification Efficiency:Increasing gasification temperature leads to the dissipation of CO2, increasing the yield of CO during co-gasification.

Coal and Wood Pellet Blend Impact:Blends of coal and wood pellets (CL/WP) with higher volatile matter enhance the production of combustible gases, contributing to a higher H2/CO ratio in the syngas.

Equivalence Ratio Influence:Higher equivalence ratios at higher temperatures lead to increased feedstock conversion and higher fuel quality in terms of H2/CO ratio.

Temperature and Gasification Efficiency:Increasing gasification temperature leads to the dissipation of CO2, increasing the yield of CO during co-gasification.

---

Further Research and Commercialization:The need for additional experiments and the fitting of proposed models with experimental results indicate potential for further research and development, with eventual commercial applications in mind.

Energy Industry Applications: The focus on heating value (HHVsyngas) and H2/CO ratio is relevant to the energy industry, suggesting potential applications in sectors requiring clean and high-quality syngas for energy production.

Optimization Opportunities: The identification of optimum conditions for co-gasification with different feedstocks (CL with SD and CL/WP) suggests potential opportunities for optimization in coal and biomass blending ratios, gasification temperatures, and equivalence ratios. This could lead to more efficient and productive gasification processes.

Syngas Quality Improvement: The study highlights the influence of gasification temperature and equivalence ratio on the quality of syngas produced (H2/CO ratio and heating value). This implies a potential for technologies that enhance syngas quality, which is crucial for various industrial applications.

---