Ryuichi Ashida

Dewatering of coal through solvent extraction

A new non-evaporative coal dewatering method was presented, in which a bed of coal was contacted with a flowing non-polar solvent at less than 200 °C. Water in coal was released by thermal energy added and the released water was dissolved into solvent and was carried away from the coal bed. When the solvent was recovered at room temperature, most of water is separated from the solvent due to the decrease in the solubility of water in the solvent. Then the water is easily separated from the solvent by decantation. This method, therefore, removes water without causing phase change of water. When an Australian brown coal whose water content was 50% was treated by tetralin at 150 °C, the water content was reduced to less than 2%. This clarified that the presented method is more effective than the other methods from both the energy saving viewpoint and dewatering efficiency. The mechanism of dewatering was discussed based on the strength of hydrogen bonds formed between coal and water and the change in the solubility of water in the solvent with increasing temperature.

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.

Measurement of CO2 Gasification Rate of Coal Char Under High Pressure and High Temperature Using a Mini Directly-Heated Reactor

A mini directly-heated reactor (mini-DHR) was constructed to measure the gasification rate handily under high CO2 pressure of ~ 2 MPa in the presence of other gases, such as CO and H2, at T = ~ 1,200°C. The mini-DHR was made of U-shaped SUS or Pt tubing of 3 mm I.D. The reactor itself was used as a heating element. An electric current of 75–150 A and a few volts were introduced to the reactor to heat up the reactor up to 900–1,200°C. About 1 mg of char was placed in a platinum mesh basket of 1.0 mm I.D. and 10 mm high. The basket with the char sample was placed just above a thermocouple in the reactor. The conversion of char, X, was estimated by weighing the remaining char sample. The X vs. t relationships obtained under various conditions were analyzed to formulate a gasification rate equation in the presence of both CO2 and CO for a char prepared from an Australian brown coal.

Upgrading of low-rank coal and biomass utilizing mild solvent treatment at around 350°C

The authors have been proposing methods to dewater, and fractionate coal by using the sequential thermal solvent extraction. They have recently showed that the degradative extraction at around 350°C using a non-polar solvent such as 1-methylnaphthalene under 10 MPa is effective to recover several fractions having similar chemical and physical properties from a wide range of low-rank coals. In this paper the applicability of the method to much lower grade carbonaceous resources is examined. Two biomasses, cellulose, lignite, a peat and four low rank coals, and mixed samples of biomass and two coals were treated by 1-methylnaphthalene at 350°C to upgrade and to fractionate the raw materials into several fractions having similar chemical and physical properties. The extracted fractions, Solubles and Deposits, were very close to each other in elemental composition, chemical structure, molecular weight distribution, pyrolysis behavior, and softening/melting behavior. Thus, the proposed degradative solvent extraction method was found to be effective to convert low grade carbonaceous resources into solid fuels having higher heating values and significantly upgraded compounds having similar chemical and physical properties.