Efecto en resultados por impuesto a las ganancias

While several researchers have undertaken studies into the pre-treatment of WS using AKP, only few research published investigated sequential treatment of DAP after AKP for WS and none have extensively investigated the combined effect of the main process factors, solvent concentration, treatment duration and temperature and/or the interaction for CL.

The cellulose and other carbohydrates content in the CL and WS discussed in Section 6.3.1 and 6.3.3 was used to calculate coefficients for the RSM equation.

These coefficients were then used to generate the second order polynomial equation

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which was used to predict the conditions for optimum cellulose content for sequential DAP after AKP of CL or WS.

The statistical analysis of the RSM indicated that all the three individual pre-treatment variables X¹, X² and X³ were of significance (p < .10). The coefficients were fitted to Eq. (6-3) and (6-4) to generate the model for the CL and WS cellulose. The fit of data into the model demonstrates a correlation with R² value of 86.03% and 90.23%, respectively for WS and CL. The model for pre-treatment parameters and cellulose content for CL and WS after sequential DAP after AKP were described by the following equations:

Y^CL_H2SO4 = 0.3489 - 0.0298 X¹ + 0.000165 X² - 0.002097 X³ + 0.00271 X¹² % -

0.000002 X²² + 0.000011 X³² + 0.000023 X¹X² + 0.000238 X¹X³ + 0.000002 X²X3 (6-3)

Y^WS_H2SO4 = 0.5797 - 0.0258 X¹+ 0.000450 X² - 0.002580 X³ + 0.00293 X¹² -

0.000005 X²² + 0.000016 X³² - 0.000057 X¹X² + 0.000321 X¹X³ + 0.000007 X²X3 (6-4)

where Y^{CL_ H2SO4}and Y^WS_H2SO4 is the cellulose content of the CL and WS following treatment, X¹, X² and X³ are H²SO⁴ concentration (%), pre-treatment time/duration (min) and treatment temperature (°C), respectively. These values are in un-coded units. Predictions from the second order polynomial to describe the effect of pre-treatment variables on the CL and WS cellulose content for sequential DAP after AKP are described in the following section. According to the RSM predictions, the optimum conditions for cellulose enrichment are 3% H²SO⁴, at 120 °C for 30min for WS (59.66%) and 3% H²SO⁴, at 120 °C for 90min for CL (30.23%). Validating the model was undertaken to confirm the accuracy within the investigated range, the optimised conditions of CL and WS. The predicted and measured values for the cellulose content of the sequential DAP after AKP pre-treated CL were 30.16% and 29.27% and WS sequential DAP following AKP were 59.41% and 58.52%

respectively. The predicted values generated by the model are comparable with the measured results and are within the 5% error associated with the model. These results confirm the model can be used to determine the cellulose content of the CL and WS for sequential DAP following AKP pre-treatment at conditions in the range investigated within the model.

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6.4 Conclusions

Sequential pre-treatments of AKP followed by DAP showed a positive effect on CL and WS degradation, improving cellulose yield and solibilisation of hemicellulose and lignin compared with those obtained with single AKP pre-treatment. The total cellulose yield achieved with DAP after AKP indicated that this sequential pre-treatment was very effective in reducing lignin and hemicellulose, which was associated with an increase in cellulose content. AKP could unlock approximately 40-87% of the residual lignin from the lignin–cellulose complex, and DAP unlocked 35-80% of the residual hemicellulose leaving cellulose more accessible for utilisation, thus resulting in higher cellulose yields as well as water soluble content.

Interestingly, time was not as important as temperature in the range of experimental conditions for AKP and sequential DAP. Therefore, feasibility of AKP and DAP pre-treatment versus the enhanchment in biogas yield worth assessing before scale-up of pre-treatment processes and an AD facility.

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Chapter 7 Effect of Pre-treatment on Sequential Anaerobic