Aspen Plus simulation for effluent reuse in thermomechanical pulp mills.

The objective of this study was to evaluate the closing of the water circuit and reusing the treated effluent in the production of TMP, using simulations performed with the Aspen Plus®. The treated effluent was reused to replace 50, 75 and 100% of the well water. An adaptation of the Aspen Plus® program simulating the TMP production process and a dynamic simulation test to verify the accumulation of non-process elements (NPEs) in industrial processes at different proportions of reuse were evaluated. The quality of the final product was assessed in laboratory bleaching tests for pulp brightness and brightness reversion. The concentrations of the NPE were 0.00097, 0.00122 and 0.00145 kmol/h for Mn2+, 0.012929, 0.018368 and 0.023595 kmol/h for Fe2+ and 0.000542, 0.000722 and 0.000948 kmol/h for Cu2+, with the recycling of the treated effluent of 50, 75 and 100%, respectively. The brightness and brightness reversion of the pulp were similar with the different proportions of effluent reuse and with the use of fresh industrial water, with values ranging from 83.37 to 83.97% ISO and 5.43 to 6.38 ISO units, respectively. The use of treated effluent did not affect the pulp quality, which could diminish the water use a pulp mil.

Hydrothermal carbonization of microalgae biomass produced in agro-industrial effluent: Products, characterization and applications.

Hydrothermal carbonization is a thermochemical treatment whose objective is to convert carbohydrate components of a given biomass into carbon-rich material in an aqueous medium. Biomass of wastewater grown microalgae is among the various potential biomasses for this route. However, operational parameters of hydrothermal carbonization for different types of biomass are still being investigated. In general, larger temperature ranges (180-260 °C) are applied to woody biomasses, which have fibrous and/or ligneous structures and, therefore, are more thermally stable than algae biomass. This study presents the hydrothermal carbonization of microalgae biomass cultivated in an agro-industrial effluent. For this purpose, a Parr reactor was operated at different temperatures (130, 150 and 170 °C) and retention times (10, 30 and 50 min). Results showed improvements in the properties of the hydrochar, mainly energy yield and carbon concentration, after the thermochemical treatment. Energy recovery was improved, as well as hydrophobicity of the carbonized material. It was observed that in the retention time of 10 min, the increase in temperature provided an increase of 7.53% in the yield of solids. On the other hand, in the retention times of 30 and 50 min, when the temperature was increased, the solid yield decreased 6.70% and 0.92%, respectively. Thus, the highest yield of solids (77.72%) and energy (78.21%) was obtained at the temperature of 170 °C and retention time of 10 min. There was a high ash content in the raw biomass (32.99%) and an increase of approximately 3% in the carbonized material, regardless of the applied treatment. With the exception of potassium and sodium, the other macro and micronutrients were concentrated in the hydrochar after thermochemical treatment, indicating the potential of the material for agriculture application, in addition to energy use. Results showed that the retention time was the most significant operational parameter of the process.

Hydrothermal and organic-chemical treatments of eucalyptus biomass for industrial purposes.

This study aimed to evaluate the promising feasibility of the hydrothermal pre-processing of eucalyptus wood and eucalyptus bark under organosolv and organic acid conditions to produce a highly concentrated cellulose feedstock. For that, particulate samples of both biomasses were heated in water solutions containing from 0 to 50%vol/vol of ethanol and from 0 to 50 mmol.L-1 of oxalic acid at temperatures between 140 and 180 °C. Significant differences on the thermal degradation profiles were observed for both biomasses indicating the partial hydrolysis converted them into a more homogeneous solid fraction with higher contents of cellulose. It was also observed a significant variation of the glycan content from approximately 39 to 76% for wood particles, whereas the variation for bark was from 32 to 50%. In general, the proposed pre-processing route was considered potentially feasible to concentrate the cellulose/glycan contents of eucalyptus biomasses for subsequent industrial utilization.

A multi-criteria decision analysis of management alternatives for anaerobically digested kraft pulp mill sludge.

The Multi-Criteria Decision Analysis (MCDA) procedure was used to compare waste management options for kraft pulp mill sludge following its anaerobic digestion. Anaerobic digestion of sludge is advantageous because it produces biogas that may be used to generate electricity, heat and biofuels. However, adequate management of the digested sludge is essential. Landfill disposal is a non-sustainable waste management alternative. Kraft pulp mill digested sludge applied to land may pose risks to the environment and public health if the sludge has not been properly treated. This study is aimed to compare several recycling alternatives for anaerobically digested sludge from kraft pulp mills: land application, landfill disposal, composting, incineration, pyrolysis/gasification, and biofuel production by algae. The MCDA procedure considered nine criteria into three domains to compare digested sludge recycling alternatives in a kraft pulp mill: environmental (CO2 emission, exposure to pathogens, risk of pollution, material and energy recovery), economic (overall costs, value of products) and technical (maintenance and operation, feasibility of implementation). The most suitable management options for digested sludge from kraft pulp mills were found to be composting and incineration (when the latter was coupled with recycling ash to the cement industry). Landfill disposal was the worst option, presenting low performance in feasibility of implementation, risk of pollution, material and energy recovery.