Comparison of Three Novel Energy Conversion Technologies, Gasification, Pyrolysis, and Hydrothermal Carbonization (HTC) - Review

Mahbod Shafiei1, Bodo Groß2, Andreas Dengel3 and Pal Szentannai1

1BME Department of Energy Engineering, Budapest, Hungary 2IZES gGmbH, Saarbrücken, Germany 3STEAG New Energies GmbH, Saarbrücken, Germany

BioenNW PartnersBioenNW Objectives1) Create a network of Bioenergy Support Centres (BSC) to provide support to companies,

organisations and local authorities to deliver local bioenergy more efficiently and cost-effectively by providing feedstock testing services, developing biomass energy projects,organising workshops and seminars.

2) Build a number of knowledge based tools to aid the bioenergy development process andassist identification of high potential bioenergy development sites

3) Demonstrate the combined operation of anaerobic digestion and intermediate pyrolysis at acommercial scale to illustrate a broad range of biomass types as input materials

4) Explore at least twenty five new bioenergy schemes and develop five of these to the pointof built.

Building on the project objectives above, each BSC will identify five sites in their region with thehighest potential to be turned into new bioenergy schemes. This means that a total of 25 siteswill be identified through BioenNW. The five selected sites will be taken to the point of build bythe end of the project in March 2015.

IntroductionIndustrialization and population growth are among factors for the rising trend in the

global energy demand. By the year 2030, the global energy demand is forecasted to increaseby 43.64% from the current total of 472 quadrillion Btu to 678 quadrillion Btu. It is alsopredicted that fossil fuel will still remain dominate source of energy by the year 2030 thatcontributes toward fossil fuel depletion and climate change. Hence development ofalternative energy is inevitable. Among all renewable energies, solid wastes and agriculturalresidues (biomass) has became an important source of fuel since the early 1970s.[1]

Figure 1) Rice husk, wood chips, weed grass and pod corn are used as biomass. (Reference: www.majec-biomass.com )

Thermo – Chemical processes are mainly developed by pre treatment of biomass

following by heating material (various heating temperature in technologies) by controllingamount of oxygen, different phase of product can be gathered which by processing ofproducts many range of fuels will be obtained .Gasification, Pyrolysis , and Hydrothermal Carbonization are the thermal conversionprocesses available for thermal treatment of solid wastes which different products such as

combustible gas, liquid fraction ( tars and oil) and solid ( mainly char) are gained.

GasificationGasification is the controlled partial oxidation of a carbonaceous material, by

supplying less oxygen than the stoichiometric requirement for complete combustion (thermaldegradation in the absence of oxygen). It proceeds at temperatures ranging between 600 and1500 C. A striking feature of the technology is its ability to produce a reliable, high-qualitysyngas product that can be used for energy production [2]. Wastes such as refinery residuals,secondary oil-bearing refinery materials, municipal sewage sludge, and Biomass and cropresidues also have been gasified successfully according to the following reaction:

Char + limited oxygen → Gas +Tar + Ashes

Figure 2) Schematic of gasificationProduct gas from gasification consists ofa mixture of carbon, carbon dioxide,methane, hydrogen, and water vapor.The composition of final product isdependent on equilibrium achieved byvarious gas – phase reactions. Air,oxygen, hydrogen or steam are uses asan agent in gasification process toconvert carbonaceous material intogaseous products .(Reference: www.thewatt.com)

Figure 3) Schematic of fast pyrolysisprocess. By upgrading pyrolysis oil,various fuels can be separated viastandard distillation process and threeproduct such as jet fuel, diesel, andnaphtha can be gained.(Reference: www.dynamotive.com)

Hydrothermal Carbonization (HTC)

In the hydrothermal process, biomass is surrounded by water during the reaction,

which is kept in a liquid state by allowing the pressure to rise with the steam pressure in

high – pressure reactors. HTC method has attracted a great deal of attention because it

uses water which is inherently present in green biomass. Typically HTC of biomass is

achieved in water at elevated temperatures (180 -250’ C) under standards pressures (2-10 Mpa) for several hours . HTC produces higher solid yields. [3]

PyrolysisPyrolysis is thermal decomposition occurring in the absence of oxygen. The main

process for char production with significant yields is the dry pyrolysis process. Temperaturerange are between 287 C to 500 C with residence time 2 second to a day [4]. one of thecharacteristics of this process is flexibility of feedstock where it burns part of the load for theheat input. Pyrolysis has three different types include: Fast , intermediate , and slow pyrolysis.Fast pyrolysis is an effort to make the liquid product (bio–oil ) Yield from solid biomass is apotential candidate for power generation.

Figure 4) Schematic of Hydrothermalcarbonization. The composition andstructure of the solid product (hydrochar) from HTC differs substantiallyfrom dry pyrolysis chars. hydro chargenerally has higher H/C and O/C ratiossimilar to natural coal, Also HTC uses aspre treatment for gasification which isreferred to as wet Toreffaction.(References:www.cscarbonsolutions.de)

ConclusionCarbonization of biomass residue and waste materials has great potential to

become an environmentally sound conversion process for the production of a wide

variety of products. Many years of research have shown that conversion technologies

have a great potential in carbon sequestration to reduce the impact of greenhouseeffect.

ACKNOWLEDGEMENTSThis work has been funded by the IZES gGmbH, Germany, as part of the project

BioenNW , and done in Budapest University of Technology and Economics, Hungary.

References[1] Jeng Shiun Lim, Zainuddin Abdul Manan, Sharifah Rafidah Wan Alwi, Haslenda Hashim, 22March 2012, ‘’ A review on utilization of biomass from rice industry as a source of renewableenergy’’ Process Systems Engineering Centre (PROSPECT), Faculty of Chemical Engineering,University Technology Malaysia, 81310 Johor Bahru, Johor, Malaysia[2] Dr. Samy Sadaka, P.E., P.Eng. ’’Gasification’’ Associate Scientist, Center for SustainableEnvironmental Technologies Adjunct Assistant Professor, Department of Agricultural andBiosystems Engineering Iowa State University 1521 West F. Ave. Nevada, IA 50201[3] Hydrothermal carbonization of biomass residuals: a comparative review of the chemistry,processes and applications of wet and dry pyrolysis future science group 10.4155/BFS.10.81 ©2011 Future Science Ltd[4] David Chiaramontia, Anja Oasmaab, Yrjo¨ Solantaustab,26 Jully 2005,’’ Power generationusing fast pyrolysis liquids from biomass’’, University of Florence, Department of EnergyEngineering ‘‘S.Stecco’’, I-50139, Florence, Italy