Pier Ugo Foscolo

Advanced Process Integration: The UNIQUE Gasifier Concept—Integrated Gasification, Gas Cleaning and Conditioning

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. In this chapter, an example for a promising process integration is described—the recently developed UNIQUE gasifier concept. The UNIQUE gasifier integrates gasification, gas cleaning, and conditioning in one reactor unit. This concept offers a compact design with decreased requirements for footprint as well as reduced investment costs.

Chapter 7 – Polygeneration Strategies

Polygeneration is a concept to improve the economic viability and sustainability of the utilization of biomass via gasification by combining the production of at least two products. The goal is to maximize the efficiency to transform energy and material of the feedstock into products. Syngas from biomass gasification can be converted into a broad range of energy products, for example, electricity, heat, gaseous or liquid fuels, or chemicals. Polygeneration offers high flexibility with regard to changes of market demands. For example, a polygeneration process for combined production of biofuels, heat, and power could be used as a back-up power plant. If the current electricity consumption increases, the production of biofuels can be switched to the production of power. Higher flexibility requires higher capital investments as well as higher costs for operation and maintenance. n nIn this chapter, some polygeneration strategies are described starting with the classical example of combined heat and power production followed by newer approaches, such as combined synthetic natural gas, heat and power production, combined biofuels, heat and power production, as well as combined hydrogen and heat production.

Chapter 2 – Fundamental Concepts in Biomass Gasification

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.

Chapter 5 – Advanced Process Combination Concepts

Gasification is a process to convert carbonaceous material into gas by using a gasifying agent. If this thermochemical process is performed in a conventional one-stage biomass gasifier, several process steps are overlapped, such as heating and drying of the fed biomass, pyrolysis of the volatiles, oxidation and gasification of the charcoal. n nTo improve the gasification process, modern, advanced gasification concepts discussed in Section 5.1 combine separated pyrolysis and gasification stages. Two different approaches are shown in this chapter: (1) combination of pyrolysis and gasification directly in a multistage gasification process; (2) pyrolysis and gasification at different locations. n nGasification of biomass can advantageously be combined with a combustion stage. In Section 5.2 three concepts are described: (1) dual fluidized bed process with internal combustion; (2) gasification with partial oxidation for the reduction of tar in the product gas; (3) gasification for cofiring of the product gas in a coal combusted power plant. n nAlso the combination of downstream processes can simplify the overall processes and increase their efficiency. One concept, which will be discussed in Section 5.3, is the combination of the water gas shift reaction and the following separation of H2 and CO2 in one single catalytic membrane reactor.

Chapter 6 – New and Improved Gasification Concepts

Even though gasification is an old technology, there is still much potential for improvement, for example, related to efficiency, complexity, and flexibility. Beside the technical aspects, economic aspects also drive the development of new and improved gasification technologies. Some new and improved gasification concepts are described in this chapter. Oxygen–steam gasification, being state-of-the-art in coal gasification, is still under investigation for biomass gasification and needs further innovation for an economically feasible oxygen supply, for example, by membranes, as discussed in Section 6.1. Section 6.2 deals with an alternative for oxygen supply in gasification, that is, the chemical looping (oxidation and reduction) of oxygen carrier materials. Section 6.3 gives an overview on supercritical water gasification which has particular advantages in the gasification of wet biomass.

Chapter 3 – Biomass Pretreatment

Biomass feedstock can have a wide variety of chemical and physical properties. In contrast to that, conversion processes like gasification usually require specific physical and chemical properties of a fuel. Several pretreatment methods are used to adjust the fuel properties to the process requirements. This chapter will give a brief overview on relevant physical, thermal, and thermochemical pretreatment methods, which are partly already state-of-the-art or promising new processes.