Techno-economic evaluation of a mechanical pulp mill with gasification

Abstract

SUMMARY: Mechanical pulping processes, including thermomechanical pulp (TMP), groundwood (SGW and PGW), and chemithermomechanical pulp (CTMP) processes, each have a very high wood-to-pulp yield. Producing pulp by means of these processes is a prerequisite for paper (such as printing paper and paperboard) grades requiring high printability and stiffness. However, mechanical pulping processes consume a great amount of electricity, which may account for up to 40% of the total pulp production cost. In mechanical pulping mills, wood (biomass) residues are commonly utilized for electricity production through an associated combined heat and power (CHP) plant. This techno-economic evaluation deals with the possibility of utilizing a biomass integrated gasification combined cycle (BIGCC) plant in place of the CHP plant. Implementing BIGCC in a mechanical pulp production line might greatly improve the overall energy efficiency and cost-effectiveness, especially when more biomass from forest (such as branches and tree tops) is available. When the fibre material that negatively affects pulp properties is utilized as a bioenergy resource, the overall efficiency will be further improved. A TMP+BIGCC mathematical model is developed with ASPEN Plus. By means of modeling, three cases are studied: 1) adding more forest biomass logging residues in the gasifier, 2) adding the reject fibres in the gasifier, and 3) decreasing the TMP-specific electricity consumption (SEC) by up to 50%. For a TMP+BIGCC mill, the energy supply and consumption are analyzed in comparison with a TMP+CHP mill. The production profits are evaluated. ADDRESSES OF THE AUTHORS

Economic Evaluation on Bio-Synthetic Natural Gas Production Integrated in a Thermomechanical Pulp Mill

“…The energy balance over the TMP + BtSNG mill is studied by applying the model, in comparison with other two cases of TMP + BIGCC and TMP+ Boiler studied previously [7], as seen in Figure 5.…”

“…The total steam demand is kept constant because of the constant paper throughput, and is provided from the steam energy recovered mainly from the TMP refining process and also from the BtSNG process to a minor The energy balance over the TMP + BtSNG mill is studied by applying the model, in comparison with other two cases of TMP + BIGCC and TMP+ Boiler studied previously [7], as seen in Figure 5.…”

“…The techno-economic analysis of TMP + BIGCC has been studied previously [7]. Coal-based IGCC technology has been effectively commercialized.…”

“…For gas phase processes, the Peng-Robinson equation of state with Boston-Mathias modification was applied [11,13]. For the H&P system, the Property Method STEAM-TA was employed [7,16]. For the units involving electrolytes, the electrolyte non-random two liquid model, ELECNRTL, in ASPEN Plus was applied.…”

“…A previous study investigated the profitability of a TMP mill integrated with a biomass integrated gasification combined cycle (BIGCC) for electricity generation [7]. In the present study, the feasibility of biomass gasification-based technology to produce CH 4 in a TMP mill is evaluated and compared with TMP + BIGCC in terms of the technical and economic aspects.…”