Hongzhang Chen and Junying Zhao

Abstract This chapter presents several integrated refining and fractionation tech­nologies for multiple products platform based on the understanding of the hetero­geneous property of corn stalk. This heterogeneous property was found at the levels of tissue, cell, and chemical composition. This property can be advantageous when proper fractionation technologies are adopted to pro-duce different products. Based on low pressure steam explosion technology, steam explosion integrated me-chanical carding, steam explosion integrated super grinding and steam explosion integrated washing and alkali extraction are designed to realize stalk fractiona-tion at different levels. Industry implementation of these technologies was also presented.

Keywords Lignocelluloses ■ Inhomogeneity ■ Steam explosion ■ Integrated ■ Fractional refining ■ Multi-production

4.1 Introduction

At present, stalk-based products from stalk refining has been regarded as perspective both in research and industrialization [1,2]. In that, the world is rich in stalk [3, 4] without application completely. However, stalk refining is hard to be industrialized for lack of cost-competitiveness.

The main reason for lack of cost-competitive is that stalk is converted into one product as a whole with single linear technology. For example, corn stalk is con­verted into ethanol with dilute acid pretreatment and simultaneous saccharification and fermentation technology [5]. The whole corn stalk is regarded as raw material with single conversion property. As a result, only about 30 % cellulose and a little hemicellulose are converted into ethanol. Other components including lignin are dis­charged as wastes. Therefore, this increases cost and causes pollution. Lignin from stalk could also be converted into various products [6]. However, if lignin in stalk

H. Chen (H) ■ J. Zhao

National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China e-mail: hzchen@home. ipe. ac. cn

Z. Fang (ed.), Pretreatment Techniques for Biofuels and Biorefineries,

Green Energy and Technology,

DOI 10.1007/978-3-642-32735-3_4, © Springer-Verlag Berlin Heidelberg 2013 is converted into products as the only effective component, there would be the same problems including high cost and pollution. Hemicellulose in corn cob is usually converted into furfural [7]. There is report that microorganism could also convert pentose from hemicellulose [8]. Therefore, cellulose, hemicelluloses, and lignin in stalk are all potential resources. If only one component of stalk is converted with single linear technique, high cost and pollution would be unavoidable.

Lignocellulose materials including stalk are not only heterogeneous in the level of component but also in the levels of tissue and cell [9, 10]. Therefore, the conversion properties of stalk are also different. If the whole stalk is converted into one product, the product quality is hard to be controlled.

So it is necessary to fractionate stalk according to its heterogeneous characteristics in levels of component, cell, and tissue; then different fractions are converted into op­timum products. The whole process from stalk to products includes pretreatment, sac­charification, and fermentation. Fractionation should be realized in pretreatment pro­cess. Pretreatment methods reported focus on separation of one component including steam explosion [11], dilute acid or alkali [12], and hot water [13], and the whole stalk could not be fractionated completely into different fractions with only one of these technologies. Though there is report about integrated pretreatment technology, it is also amid at one product [14]. The intrinsic property of heterogeneity is ignored.

For example, steam explosion method is integrated with many other pretreatment technologies to improve ethanol yield including methanol, hydrogen dioxide, sodium hydroxide [15], ammonia, and sulfur dioxide. Sodium hydroxide and 1,4-dihydroxy — anthraquinone pretreatment are integrated for corn stalk to improve the methane yield [16]. Chemical and ultrasonic techniques are integrated to remove lignin and hemicelluloses in wood and get 5-10 nm fiber [17]. Therefore, integrated technology system should be set up to realize fractionation of stalk.

The author team have found heterogeneous characteristics of stalk and its different conversion properties [1, 9]. Moreover, steam explosion integrated pretreatment technology is set up to fractionate stalk into fractions and converted into multiple products. Different fractionation technologies are designed for different levels of fractionations.

This paper analyzes the heterogeneous characteristic of stalk and its require­ment for conversion technology, and then steam explosion integrated pretreatment technologies are introduced as a multiple products model. Finally, industrial demon­stration is given and advantages of fractionation refining technology oriented by multiple products are presented.