Elsevier

Energy

Volume 214, 1 January 2021, 118967
Energy

Efficiency of a power generation alternative regarding the composition of feeding biomass-glycerol slurry; theoretical assessment

https://doi.org/10.1016/j.energy.2020.118967Get rights and content

Highlights

  • Contribution to studies of power generation consuming biomass and bio-fuel residue.

  • Investigation on the influence of glycerol content in the slurry with biomass pumped into a new power-generation process.

  • Appraisal on the use of highly pressurized fluidized bed gasification of biomass-glycerol mixtures.

  • Presentation of details related to steam and gas combined cycles consuming sugar-bagasse and glycerol.

  • Theoretical verification that feeding solid fuel as slurry might lead to efficient power generation.

Abstract

Following studies on Fuel Glycerol Slurry Integrated Gasification/Gas Turbine (FGSIG/GT) power generation processes, the present investigates the efficiency of a FGSIG/GT alternative regarding the composition of the slurry pumped into the process. Such slurry is prepared by mixing sugar-cane bagasse (SCB) and raw glycerol—a residue of biodiesel production. Differently from previous investigations, the current one considers the alternative where the wet solid fuel is dried before mixing with raw glycerol to form the slurry to be pumped into the gasifier. Such feeding alternative circumvents the use of cumbersome multiple lock-hoppers, usually applied in feeding of particulate solid into pressurized vessels. The stream leaving the gasifier goes through cleaning before being injected into commercial turbines. Energy recovering drives two Rankine cycles. Despite biomass fuel enhancement provided by the glycerol, it has been shown that the highest power generation efficiency can be achieved for slurries with relatively small glycerol content. The 1st and 2nd thermodynamic law efficiencies reached maxima nearing 47% and 36%, respectively. Those values are much higher than the 20% 1st law efficiency currently achieved at sugar mill units as well as the 33% predicted by theoretical studies on Biomass Integrated Gasification/Gas Turbine process consuming only sugar cane bagasse.

Introduction

The efforts to improve the share of renewables as sources for power generation are increasing. To provide an example, units consuming sugar-cane bagasse (SCB) are already responsible for 27% of the total 160 GW Brazilian installed capacity [1]. On the other hand, the rate of biodiesel country’s production is also growing, nearing now 4.5 million m3 per year [2].

As a residue, raw glycerol represents around 10% of the biodiesel production, was considered for applications in various industrial fields [3]. However, others have shown high relatively high costs involved in its purification [4]. Alternatively, some have studied the feasibility of raw glycerol as fuel and fuel additives [5] and others the opportunity of co-gasification of that residue with biomass for the generation of fuel gas [6]. On the other hand, feeding solid particulate fuels into pressurized equipment require special measures to avoid interruptions and high-maintenance costs. Since long, it has been verified [7] that slurry-feeding greatly simplifies the more conventional methods using series of lock-hoppers [8]. Nonetheless, fibrous particles might entangle inside a hopper, thus preventing them to proceed to rotary valve beneath it. This is particularly true in cases of SCB. In addition, lock-hoppers require to be under cooled inert atmospheres (such a nitrogen) to preclude fuel pyrolysis and combustion inside them. Thus, slurry-feeding brings substantial savings on capital, operation, and maintenance of power generation units based on pressurized combustion or gasification. Therefore, added to the enhancement of SCB as fuel by mixing it with raw glycerol, that strategy allows easy feeding of the solid fuel into pressurized equipment composing the power generation process.

Section snippets

State of Art

The present work adds to a series of theoretical ones aiming the application of biomass, and other residual solid fuels, mixed with water and pumped into boilers. In all of them the concept of fuel slurry-feeding, with the advantages described above, have been applied.

The Karita Power Station (Kyushu Electric Power Co., Japan) was the first and only reported unit operating with pressurized boiler combustion chamber into which a water slurry of coal was pumped [9,10]. The basic conceptual idea

Objective

Differently from a previous theoretical work [29], the present one concentrates on Configuration A (Fig. 4) to study the influence of glycerol proportion in the slurry with SCB fed into the gasifier on the overall process power generation efficiency. This might provide parameters for the decision-taking phase related to the application of RG toward enhancing power generation based on SCB. Six cases with different amount of the dry solid content in the slurry are analyzed.

Tools

The optimization procedures described here were accomplished by applying two simulation software.

CeSFaMB©2 was used to optimize the gasifier and dryer operations. It provides detailed descriptions of temperatures, pressures, and flows inside the equipment as well important overall operational data. The mathematical model behind the simulator is described elsewhere [9] and summarized in the Appendix. The simulator has been validated against real operational of boilers [[30], [31],

Methodology

For the present optimization study, the following methodology has been followed:

  • 1)

    First Stage: Initial gasifier optimization. As seen, dried SCB and glycerol are fed into the gasifier (Fig. 4). To be conservative, the dry particles entering the gasifier were assumed to be at the ambiance temperature. Thus, the gasifier and dryer optimizations could be accomplished independently. At this step, the rate of air injected into the gasifier and the mass flow of glycerol added to the slurry with SCB,

Premises

The following were assumed during this investigation:

  • 1.

    The gasifier and dryer operate under the bubbling fluidized bed (BFB) technique. SCB leaving the mill might carry small rocks and other materials along the harvested cane. BFB units are capable of operating within a wide range of feeding particle sizes and densities [30,42]. Well-designed equipment might allow for the removal of heavier materials that might drop on the distributor surface without interrupting the operation. Nonetheless, other

Results and discussions

Having in mind the assumptions listed above, preliminary simulations verified that a 5 m internal diameter bed allowed for a wide range of gasification operations, most of them within the feasible bubbling fluidization regime. Therefore, that was taken for this first round of optimization.

Fig. 6 depicts the EE for different rates of air injected into the equipment against the feeding slurry DSC. Few points were not be plotted because they led to operational conditions outside the feasible range

Conclusions

The theoretical investigation regarding the influence of sugar-cane bagasse (SCB) and raw glycerol slurry composition on the efficiency of an alternative power generation unit has been carried. The FGSIG/GT (Fuel-glycerol Slurry Integrated Gasifier/Gas Turbine) process operating under the option of biomass drying prior to its mixing with glycerol has been chosen. This differs from a previous study [29], which applied the alternative of wet SCB-glycerol slurry gasification.

The work also presents

Credit author statement

Marcio L. de Souza-Santos, Conceptualization, Methodology, Software, Review, Final text (in English), Answers to reviewers. Carina Crisp Cadavez, Computations, Simulations, Result analysis, Figures, Original Text (in Portuguese)

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors are grateful for the grant received from the National Council for Scientific and Technological Development (CNPq).

References (57)

  • M.L. de Souza-Santos

    CSFB applied to fluidized-bed gasification of special fuels

    Fuel

    (2009)
  • M.L. de Souza-Santos

    Application of comprehensive simulation to pressurized fluidized bed hydroretorting of shale

    Fuel

    (1994)
  • M.L. de Souza-Santos

    A study on thermo-chemically recuperated power generation systems using natural gas

    Fuel

    (1997)
  • M. Ayoub et al.

    Critical review on the current scenario and significance of crude glycerol resulting

    Renew Sustain Energy Rev

    (jun 2012)
  • D. Aquaro et al.

    High temperature heat exchangers for power plants: performance of advanced metallic recuperators

    Appl Therm Eng

    (2007)
  • J. Schulte-Fischedick et al.

    An innovative ceramic high temperature plate-fin heat exchanger of EFCC processes

    Appl Therm Eng

    (2007)
  • A. Sommers et al.

    Ceramics and ceramic matrix composites for heat exchanges in advanced thermal systems—a review

    Appl Therm Eng

    (2010)
  • Management report

  • ANP

    Biodiesel evolution (B100) – 2008-2017, year report

  • D.T. Johnson et al.

    The glycerine glut: options for the value-added conversion of crude glycerol resulting from biodiesel production

    Environ Prog

    (2007)
  • N. Pachauri et al.

    Value-added utilization of crude glycerol from biodiesel production: a survey of current research activities

    ASABE meeting presentation

    (2000)
  • High pressure feeder and method of operating to feed granular or fine materials, US patent number 20110146153 A1

  • Power technology

  • T. Satoh

    The large capacity gas turbine for pressurized fluidized bed combustion (PFBC) boiler combined cycle power plant

    Bulletin of GTSJ

    (2003)
  • Dedini industries

  • M.L. de Souza-Santos et al.

    Development of studies on advanced power generation based on combined cycle using a single high-pressure fluidized bed boiler and consuming sugar cane bagasse

    Energy Fuels

    (2012)
  • M.L. de Souza-Santos et al.

    Technical evaluation of a power generation process consuming municipal solid waste

    Fuel

    (2012)
  • M.L. de Souza-Santos et al.

    Fuel-slurry integrated gasifier/gas turbine (FSIG/GT) alternative for power generation applied to municipal solid waste (MSW)

    Energy Fuels

    (2013)
  • View full text