Advanced Biomass Gasification

New Concepts for Efficiency Increase and Product Flexibility

Steffen Heidenreich, Michael Müller, Pier Ugo Foscolo

• Publisher: Academic Press
• Year: 2016
• Print ISBN: 9780128042960
• eBook ISBN: 9780128043677
• Topic: Technology & Engineering
• Subtopic: Chemical & Biochemical Engineering
• Index: Technology & Engineering

Advanced Biomass Gasification: New Concepts for Efficiency Increase and Product Flexibility provides a thorough overview on new concepts in biomass gasification and consolidated information on advances for process integration and combination, which could otherwise only be gained by reading a high number of journal publications. Heidenreich, Müller and Foscolo, highly respected experts in this field, start their exploration with the compact UNIQUE reactor, gasification and pyrolysis, gasification and combustion, and catalysts and membranes. The authors then examine biomass pre-treatment processes, taking into account the energy balance of the overall conversion process, and look into oxygen-steam gasification and solutions for air separation, including new options for integration of O2-membranes into the gasifier. Several polygeneration strategies are covered, including combined heat and power (CHP) production with synthetic natural gas (SNG), biofuels and hydrogen, and new cutting-edge concepts, such as plasma gasification, supercritical water gasification, and catalytic gasification, which allows for insights on the future technological outlook of the area. This book is then a valuable resource for industry and academia-based researchers, as well as graduate students in the energy and chemical sectors with interest in biomass gasification, especially in areas of power engineering, bioenergy, chemical engineering, and catalysis. - Explores state-of-the-art technologies that allow for greater efficiency and flexibility in gasification, including process integration, combination, and polygeneration strategies - Consolidates information that was, up until now, scattered among several sources, including journal articles - Provides a valuable resource for industry and academia-based researchers, as well as graduate students in the energy and chemical sectors with interest in biomass gasification, especially in areas of power engineering, bioenergy, chemical engineering, and catalysis

Chapter 1

Introduction

Abstract

Considerate exploitation of the available natural resources is a key issue in the sustainable supply of energy in terms of heat, power, and fuels. In this context, the utilization of renewable energy sources is a major contribution. Moreover, global warming and climate change concerns are resulting in efforts to reduce CO₂ greenhouse gas emissions by increasing the use of renewable energies and increasing the energy efficiency. Besides solar, wind, and hydro energy, biomass is considered as the main renewable energy source. As a renewable solid fuel it is suitable to replace fossil solid fuels like hard coal and lignite. In a renewable energy mixture with fluctuating availability of solar and wind energy, biomass can be exploited as a storable and adjustable energy source that will be used in increased amounts when wind and solar energy supply is low. Therefore, several developed as well as developing countries all over the world have set targets for the share of biomass to the national energy supply and have introduced policies to promote the increasing use of biomass as an energy source.

Keywords

Greenhouse gas; heat; power; biomass energy; biomass gasification

Considerate exploitation of the available natural resources is a key issue in the sustainable supply of energy in terms of heat, power, and fuels. In this context, the utilization of renewable energy sources is a major contribution. Moreover, global warming and climate change concerns are resulting in efforts to reduce CO₂ greenhouse gas emissions by increasing the use of renewable energies and increasing the energy efficiency. Besides solar, wind, and hydro energy, biomass is considered as the main renewable energy source. As a renewable solid fuel it is suitable to replace fossil solid fuels like hard coal and lignite. In a renewable energy mixture with fluctuating availability of solar and wind energy, biomass can be exploited as a storable and adjustable energy source that will be used in increased amounts when wind and solar energy supply is low. Therefore, several developed as well as developing countries all over the world have set targets for the share of biomass to the national energy supply and have introduced policies to promote the increasing use of biomass as an energy source.

Since the discovery by mankind of how to make fire, biomass has been the main energy source for thousands of years and still today it contributes in the range of more than 10% to the world energy supply and ranks as the fourth source of energy in the world [1]. In rural agricultural areas, biomass is still the main energy resource for heating and cooking and often it is the only available energy source. In developing countries in Asia and Africa more than one-third of the total energy consumption is based on biomass. A big advantage of biomass is its availability at every place all over the world which is in contrast to fossil fuels like coal, oil, or natural gas. By way of example, India has very large coal reserves of more than 250 billion tons in the state of Bihar and northeast. However, transportation costs play a major role in the distribution of the coal all over the country. In contrast, biomass is uniformly and widely distributed over the whole country [2].

Beside combustion of biomass for production of heat and power, which is still the main energetic utilization of biomass, gasification is a key technology for the use of biomass. It offers the advantage of a high flexibility in using different kinds of feedstock materials as well as in the generation of different products. In principal, all different types of biomass can be converted by gasification into a product gas mainly consisting of hydrogen, carbon monoxide, carbon dioxide, and methane. From this product gas, all kinds of energy or energy carriers, for example, heat, power, biofuels, hydrogen, and biomethane, as well as chemicals, can be provided. Synthesis of Fischer-Tropsch diesel, dimethyl ether, methanol, and methane from synthesis gas are established technical processes. The use of the available biomass resources needs to be highly efficient and sustainable. Gasification offers high potential and high process efficiency for the use of biomass [3].

Gasification of biomass is performed by partial oxidation of the carbon contained in the biomass at high temperature using a controlled amount of an oxidant which can be either air, pure oxygen and steam, or a mixture of several gasification agents. The yield and composition of the product gas depend on the biomass feedstock, the gasifier type, and the operation conditions of the gasifier, such as the used gasification agent, the temperature, and the residence time in the gasifier.

Biomass comprises a broad range of different kinds of bio materials, such as wood, forest and agricultural residues, waste from wood and food industry, algae, energy grasses, straw, bagasse, sewage sludge, etc. The use of different kinds of biomass results in different challenges and solutions for transportation, storage, pretreatment and feeding of the biomass, for operation of the gasifier, and for cleaning of the produced syngas. Most commonly used types of biomass gasifiers are fixed bed and moving bed, fluidized bed, and entrained flow gasifiers.

Depending on the use of the syngas, its cleaning needs to be very efficient. Catalytic synthesis reactions or its use in fuel cells, for example, require high purity of the syngas. The main impurities in the syngas are fly ash particles and tar. Other impurities in the syngas are typically sulfur compounds (eg, H₂S, COS), hydrogen chloride, alkali compounds, and ammonia. Tar formation is a main problem in biomass gasification. Tar condensation at lower temperatures can cause clogging or blockage of pipes, filters, catalyst units, or engines. Tar formation also lowers the syngas yield and the heating value of the gas. Tar removal has been the subject of much research leading to the development of primary and secondary measures for tar reduction. Overviews on this topic have been recently given, for example, see Han and Kim [4], Aravind and de Jong [5], and Shen and Yoshikawa [6].

In order to promote the utilization of biomass gasification, advanced concepts are required which have to maximize the syngas yield, optimize the gas quality, increase the gas purity, increase the overall process efficiency, and improve the economic viability by decreasing system and production costs.

This book aims at providing an overview on such new concepts in biomass gasification. After a short introduction to fundamental concepts and pretreatment options, concepts for process integration and combination, new and improved gasification concepts, as well as polygeneration strategies are presented.

References

1. Saidur R, Abdelaziz EA, Demirbas A, Hossain MS, Mekhilef S. A review on biomass as a fuel for boilers. Renew Sustain Energy Rev. 2011;15:2262–2289.

2. Buragohain B, Mahanta P, Moholkar VS. Biomass gasification for decentralized power generation: the Indian perspective. Renew Sustain Energy Rev. 2010;14:73–92.

3. Ahrenfeldt J, Thomsen TP, Henriksen U, Clausen LR. Biomass gasification cogeneration—a review of state of the art technology and near future perspectives. Appl Therm Eng. 2013;50:1407–1417.

4. Han J, Kim H. The reduction and control technology of tar during biomass gasification/pyrolysis: an overview. Renew Sustain Energy Rev. 2008;12:397–416.

5. Aravind PV, de Jong W. Evaluation of high temperature gas cleaning options for biomass gasification product gas for solid oxide fuel cells. Prog Energy Combust Sci. 2012;38:737–764.

6. Shen Y, Yoshikawa K. Recent progress in catalytic tar elimination during biomass gasification or pyrolysis e a review. Renew Sustain Energy Rev. 2013;21:371–392.

Chapter 2

Fundamental Concepts in Biomass Gasification

Abstract

Gasification is a thermochemical process to convert fuels into a combustible gas, the so-called “producer gas.” This chapter deals with the basic chemistry and technology of gasification processes.

Keywords

Chemistry of gasification; gasification technology; fixed bed gasifier; fluidized bed gasifier; entrained flow gasifier

2.1 Chemistry of Gasification

Gasification is a thermochemical conversion of a solid or liquid fuel into combustible gases by understoichiometric addition of a gasification agent (oxygen/air, steam, carbon dioxide) at high temperature. The so-called “producer gas” (also called product gas, synthesis gas, or syngas) can be used for heat production, (combined heat and) power generation, and the production of chemicals and fuels [1–3]. Fig. 2.1 shows a general scheme for possible process chains.

Figure 2.1 Pathways for the conversion of biomass to several products. SNG, synthetic natural gas; FT, Fischer–Tropsch; ORC, organic Rankine cycle.

The gasification process itself can be divided into several steps, which are heating up of the fuel, drying of the fuel, pyrolysis, and gasification. As a fuel particle is heated, the evaporation of the water contained in the fuel occurs at temperatures above 100°C depending on operation pressure. During devolatilization or pyrolysis...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Chapter 1. Introduction
• Chapter 2. Fundamental Concepts in Biomass Gasification
• Chapter 3. Biomass Pretreatment
• Chapter 4. Advanced Process Integration: The UNIQUE Gasifier Concept—Integrated Gasification, Gas Cleaning and Conditioning
• Chapter 5. Advanced Process Combination Concepts
• Chapter 6. New and Improved Gasification Concepts
• Chapter 7. Polygeneration Strategies
• Chapter 8. Conclusions and Outlook
• Index