Xianqing Zhu

Novel carbon-rich additives preparation by degradative solvent extraction of biomass wastes for coke-making.

In this work, two extracts (Soluble and Deposit) were produced by degradative solvent extraction of biomass wastes from 250 to 350°C. The feasibilities of using Soluble and Deposit as additives for coke-making were investigated for the first time. The Soluble and Deposit, having significantly higher carbon content, lower oxygen content and extremely lower ash content than raw biomasses. All Solubles and most of Deposits can melt completely at the temperature ranged from 80 to 120°C and 140 to 180°C, respectively. The additions of Soluble or Deposit into the coke-making coal significantly improved their thermoplastic properties with as high as 9°C increase of the plastic range. Furthermore, the addition of Deposit or Soluble also markedly enhanced the coke quality through increasing coke strength after reaction (CSR) and reducing coke reactivity index (CRI). Therefore, the Soluble and Deposit were proved to be good additives for coke-making.

Degradative solvent extraction of demineralized and ion-exchanged low-rank coals

Abstract Dehydration and upgrading are essential pretreatment methods for efficient utilization of low-rank coal. In previous works the authors employed degradative solvent extraction method to dehydrate and upgrade low-rank coals and fractionate them into several fractions. For further study of this method, two low-rank coals (MM and LY) were pretreated by acid washing for demineralization or acid washing and Na/Co ion-exchange. The pretreated and raw coals were then extracted by 1-methylnaphthalene (1-MN) at 350°C and fractionated into upgraded coal (UC), high molecular weight extract (deposit), low molecular weight extract (soluble), as well as a little H 2 O and gas products. The results show that both acid washing and ion-exchange enhance the yields and carbon contents of the two extracts. Ion-exchange obviously promotes the removal of oxygen-containing functional group during extraction. The yield of high molecular weight extract of demineralized MM increases from 3.5% to 9.5%, and the carbon content and oxygen content of low molecular weight extract of Na ion-exchanged LY are as high as 85.3% and less than 6.4%, respectively. Ion-exchange has a distinct influence on physical and chemical properties of the extracts. The influence of Na ion-exchange is especially remarkable. Thus, demineralization and ion-exchange have evident promotion for the degradative solvent extraction of low-rank coal.

Preparation of carbon fibers from low-molecular-weight compounds obtained from low-rank coal and biomass by solvent extraction

Abstract The practical use of carbon fibers is limited by their high price mainly due to the high price of precursors. We have examined a high temperature solvent extraction method to prepare carbon fiber precursors from low-rank coals and biomass, using a lignite from Australia and rice straw. 1-methylnaphthalene at 350 °C was used for the extraction and some of the extract in the solvent was precipated at room temperature. The soluble fractions at room temperature were obtained for use as the precursors by solvent evaporation. They were spun into fibers by a centrifuge spinning system and were then were extracted by cyclohexane to increase the softening point, stabilized by a temperature-programmed thermal treatment in air from 80 °C to 330 °C and carbonized at 1 000 °C for 1 h in N 2 to obtain carbon fibers. The carbon and oxygen contents of the final carbon fibers were 92 and 6.0 wt%, respectively, similar to those of commercial carbon fibers. The fiber diameter was around 4-6 µm. The soluble fractions were found to be promising low-cost precursors for carbon fibers.

Upgrading and multistage separation of rice straw by degradative solvent extraction

Abstract Upgrading and multi-stage separation (UMSS) of rice straw was conducted at different temperatures using 1-methylnaphthalene (1-MN) as solvent. Three main solid products were obtained: low molecular weight extract (soluble), high molecular weight extract (deposit) and extraction residue (residue). The elemental composition, chemical structure and physicochemical characteristic of each component were analyzed in detail. Alkali and alkaline earth metal (AAEM) contents of solid products and rice straw were also measured by ICP-MS. The results showed the yield of soluble increased with temperature, and the carbon-based yield of soluble reached 33.48% at 350°C. The carbon content and oxygen content of three solid products (soluble, deposit, and residue) increased and decreased with temperature, respectively. The carbon content of soluble and deposit reached up to 82.36% and 80.59% respectively. Meanwhile the oxygen contents of them were as low as 9.50% and 12.03% respectively. More than 86.99% oxygen of rice straw was removed as H 2 O and CO 2 . Soluble was almost free from ash, and the ash content of deposit was also less than 1.50%. The higher heating values (HHV) of three solid products were significantly higher than that of rice straw. The FT-IR results indicated that not only dehydration reaction and decarboxylation reaction occurred, but also including obvious aromatization reaction. The contents of Na, Mg and K of soluble and deposit were extremely low, and they decreased with temperature gradually. In conclusion, the degradative solvent extraction method realized dehydration, deoxygenation and multistage separation of biomass under mild condition, and obtained a variety of products of low ash and oxygen content as well as high carbon content and HHV.

Combustion Behavior of Low-Rank Coal Upgraded by Degradative Solvent Extraction

The authors have recently separated one lignite and one subbituminous coal into several fractions at around 350 °C by a degradative solvent extraction. The main products obtained are solvent-soluble fractions (extracts) and insoluble fraction which we call “upgraded coal (UC).” The UCs, with the yields of around 75 %, have rather lower moisture content, lower oxygen content, and higher energy content, compared with the raw coals. In this work, the combustion behaviors of the UCs and their raw coals were investigated preliminarily by a thermogravimetric analyzer. The results showed that the comprehensive combustibility index S of the UC was slightly improved by the degradative solvent extraction. For the lignite, the temperature of ignite temperature (T ig) and burnout temperature (T bo) of the lignite were increased slightly, while the maximum weight loss rate (R max) was slightly increased. But for the subbituminous coal, the T ig and T bo were decreased by about 20 °C. The mechanism of the changes was also primarily investigated.

Novel additives obtained from low grade biomasses for coke-making

In this study, a rice straw (RS) and a fir sawdust (SD) were extracted by 1-methylnaphthalene (1-MN) in an specially designed autoclave at different temperatures (250-350°C). Two extracts, low molecular weight extract (termed as Soluble) and high molecular weight extract (Deposit), were obtained. The feasibility of using these two extracts as additives in coking coal blends was investigated for the first time. The Soluble and Deposit addition into the coke-making coal blends obviously increased the resolidification temperature and plastic range, thus improving the thermoplastic properties of the coal blends, especially for the Soluble and Deposit obtained at higher temperature. Solubles and Deposits contained significantly higher carbon content, lower oxygen groups (such as –OH groups) and extremely lower ash content in comparison with raw biomass. These unique properties of the Solubles and Deposits could explain their good performance in thermoplasticity modification of the coal blends. The addition of Deposits and Solulbles also markedly enhanced the quality of coke with increased coke strength after reaction (CSR) and reduced coke reactivity index (CRI). Therefore, it is highly feasible to use Soluble and Deposit prepared from degradative solvent extraction of biomass as additives to coking blends.