ISSN:0734-9343    

DOI:10.1080/07349349708905141

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

An upgrading process for Indonesian low rank coal was developed to produce a highly loaded coal water mixture (CWM). The upgrading consisted of a combination of vacuum drying and tar coating processes. This treatment has enabled us to prepare a CWM with more than 60wt% of solid content and with reduced viscosity. The maximum temperature and pressure were 300°C and 0.5 MPa, respectively. Mild operating conditions employed in the newly developed upgrading process are promising to reduce the overall costs.

ISSN:0734-9343    

DOI:10.1080/07349349708905142

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In the tests described in this paper, humic acids were used to modify coal surface properties and to study the effect of such modification on the rheology of coal-water slurries (CWS).

ISSN:0734-9343    

DOI:10.1080/07349349708905143

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The preparation of Pittsburgh No.8 coal-water slurry requires a clean coal; thus, ash and pyrite must be rejected. For this purpose, Pittsburgh No. 8 coal was floated in the presence of a new family of pyrite depressant. To understand the effect of these reagents on the depression of pyrite during coal flotation, both the surface chemistry and the rheology of coal-pyrite systems must be studied. This paper summarizes the results of flotation tests at a 200 mesh of grind of Pittsburgh No. 8 coal using TEPA reagent for pyrite depression. The flotation results using TEPA show an increase of 5% in pyritic sulfur rejection (equivalent to 20% rejection of the remaining pyrite in the concentrate) at equal combustible material recovery (60%) as compared with the case when no depressant was used. Chemical and electrokinetic studies for Pittsburgh No. 8 coal and pyrite were performed to determine the effect of coal cleaning and that of this new reagent on the surface charges of coal and pyrite. The rheology of Pittsburgh No. 8 coal was also studied in the absence and presence of TEPA and related to the flotation behavior of Pittsburgh No. 8 coal. These studies indicate that TEPA not only makes the surface of pyrite more hydrophilic, but also disperses the system.

ISSN:0734-9343    

DOI:10.1080/07349349708905144

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The rheological behaviour of coal-water slurries from two low-rank coals in South Australia has been studied as a function of solids concentration, particle size and size distribution. Coal slurries consisting of particles finer than 45 micron dispersed in water were found to exhibit a wide spectrum of flow behaviour ranging from Newtonian at low solids concentrations to shear-thinning and viscoplastic with a yield stress at higher concentrations. By adding a coarser coal fraction (208–279 micron) to the fine coal slurries, the flow characteristics of the resulting mixtures at a fixed total solids concentration could be changed dramatically with a substantial reduction in the slurry viscosity. There exists an optimum coarse to fine particle ratio of 40:60 at which the slurry is Newtonian with a minimum viscosity of several orders of magnitude lower than the viscosity of a slurry containing only fine particles at the same solids concentration. A further reduction in the slurry viscosity was achieved by adding a second coarser coal particle fraction to the bimodal slurry. The significant improvement in the rheological behaviour with changing the particle size distribution may be explained in terms of rearrangement of the particles, and an effective reduction of the concentration of the fine suspension, which controls the rheology. The results obtained in this study indicate that, by carefully controlling the particle size distribution, it is possible to prepare an ‘optimum’ coal-water slurry which has a low viscosity but with high solids loadings.

ISSN:0734-9343    

DOI:10.1080/07349349708905145

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Sedimentation of coal particles should be avoided during the transportation of coal water mixtures (CWMs) by sea in tankers. The sedimentation of coal particles under shear flow plays an important role in the stability of CWMs. It is important to understand how the theological characteristics of CWMs are related to the sedimentation stability. In this study, the stability of CWMs prepared with and without a stabilizer was evaluated using test equipment developed at Yamaguchi University. The Theological measurements of CWMs were also conducted, and the results obtained were correlated with the sedimentation stability of CWMs.

ISSN:0734-9343    

DOI:10.1080/07349349708905146

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The changes in CWM rheological properties by means of high speed agitation were investigated through batch agitation tests using a laboratory-scale agitator. In this study, the rheological properties were measured according to the CWM Quality Test Method, (Center for Coal Utilization, JAPAN United Method). It was found possible to decrease the apparent viscosity of a CWM and improve the statical stability by agitation. The decrease in the apparent viscosity is mainly attributable to the more uniform dispersion of dispersant promoted by high shear agitation. The improvement of statical stability is mainly attributable to the increase in the structural viscosity caused by clay minerals liberated from the coal surface during agitation.

ISSN:0734-9343    

DOI:10.1080/07349349708905147

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In order to develop a process for the production of a coal-water slurry fuel with a high solids concentration, a novel process, elevated-temperature mechanical expression, has been proposed, and the fundamentals of the process for mechanically dewatering Hydrothermally Dewatered (HTD) brown coal slurry have been investigated. Batch tests have been carried out using a compression-permeability cell to study the pore destruction and dewatering characteristics of HTD coal slurry over a wide range of process-related variables such as applied pressure, temperature, and expression rate. A significant improvement in the pore destruction and moisture reduction of HTD coal slurry has been realised by using elevated-temperature expression. The solids concentration of compressed pellets can be as high as 80 wt%. The pressure required in the elevated-temperature expression is much lower than in a traditional mechanical expression. Therefore, elevated-temperature expression could potentially be an effective dewatering technique for brown coal.

ISSN:0734-9343    

DOI:10.1080/07349349708905148

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor