Rheological properties and stability of lignite washery tailing suspensions
Introduction
The lignite washery tailing (LWT) used in this study is a solid waste obtained from a power plant in Indonesia. Lignite from South Sumatra was first dried in a steam tube rotary dryer and subsequently combusted at the power plant. Pulverized lignite fines formed during drying were collected by wet scrubbing, and thus, a wastewater containing powdered lignite was produced. The LWT proper were obtained from this wastewater through precipitation (output of approximately 10–15 t/h). This LWT flow represents a great threat to the environment if it is disposed of incorrectly. However, the LWT is also hard to utilize, with its high water content, low calorific value and difficulties in transportation. Therefore, the disposal of LWTs is of great concern.
Coal water slurry (CWS) in China is commonly used as in clean energy applications. Considering its fine particle and high water contents, LWT is suitable for use as a CWS. Therefore, in this article, suspensions of LWTs (LWTS) were prepared for study as a CWS. Until now, the feedstock for preparing slurry has been widened from traditional bituminous coal to include biomass [1], [2], [3], [4], petroleum coke [5], [6], [7] and lignite [7], [8], [9], [10], [11]. However, no research has been reported until now on the use of LWTs as a CWS. The physicochemical properties of LWTs are different from those of common coal washery tailings: it has a volatile matter content higher than common coal washery tailings, which may be because it derives from lignite. Therefore, it is necessary to study the characteristics of LWTs in all respects to evaluate if LWTs are suitable for use as a CWS. The rheological properties are always the most important parameters of a CWS, and in this article, the rheological properties of the LWTS were first studied.
Researchers from all over the world, e.g., Boylu, Atesok and Dincer from Istanbul Technical University as well as Goudoulas et al. from Aristotle University of Thessaloniki, have extensively studied the rheological properties of CWS. The first group [12], [13], [14], [15], [16], [17] considered the effect of the addition of various chemicals on the viscosity and stability of a CWS. Goudoulas et al. [8], [10], [18] reviewed the rheological properties of lignite–water slurries as well as the solid-loading effects. Moreover, He et al. [19] summarized the methods used for studying slurry rheology, the empirical equations modeling rheological behavior. All of these studies indicated that the slurry rheology models need to be studied further and that a more fundamental approach is desirable to develop models that can be applied to the design of commercial units.
In this study, the stability and rheological properties of LWTS were studied to determine if LWTs are suitable for use as a CWS. Two test methods, i.e., a rotational viscometer and a pipeline test system, were used to study the rheological properties of the LWTS and to distinguish between theory and practice. A fundamental rheological model suitable for the LWTS that could be useful in designing a commercial LWTS reuse system for energy recovery and environment protection was proposed. In addition, the effects of dispersant NDF on the stability and rheological properties of the LWTS were studied.
Section snippets
Materials
The lignite washery tailings were collected from a power plant in Indonesia. The proximate and ultimate analysis results of the LWTs are presented in Table 1. The particle size distribution of the LWTs (Fig. 1) was measured by a Malvern MasterSizer 2000. Most particles were found to be between 1 and 100 μm, in accordance with the usual particle size requirements for a CWS. Therefore, the LWTS is suitable for further processing as a type of CWS.
An anionic dispersant NDF was selected for use in
Stability and apparent viscosity
The stability and apparent viscosity of the LWTS were measured based on the method described in Sections 2.2.1 Measuring stability, 2.2.2.1 Rotational viscometer, respectively. The apparent viscosity was defined as the average of the six values of the apparent viscosity at a 100 s−1 shear rate. The SWsta and apparent viscosity data of the LWTS with various NDF dosages under different solid concentrations are presented in Table 2. It can be observed that the stability and apparent viscosity of
Conclusions
The stability and apparent viscosity of LWTS were studied. The stability and apparent viscosity of LWTS increase with increasing solid concentration. The properties of LWTS in these two aspects all meet the requirements of a CWS.
An anionic dispersant NDF was used to study the influence of dispersant on the stability and rheological properties of the LWTS. We found that this dispersant has no effect on the stability of the LWTS, but it significantly improves the rheological properties of the
Acknowledgments
Financial supports are acknowledged from: the National Basic Research Program of China (Grant 2011CB201500), the National High Technology Research and Development Program (863 Program) of China (Grant 2012AA063505), the Special Fund for National Environmental Protection Public Welfare Program (Grant 201209023-4) and the Program of Introducing Talents of Discipline to University (Grant B08026). The authors want to thank Prof. Dr. Alfons Buekens from our Institute (ZJU) for improving the whole
References (31)
- et al.
Flow and yield stress behaviour of ultrafine Mallee biochar slurry fuels: the effect of particle size distribution and additives
Fuel
(2013) - et al.
The slurrying properties of slurry fuels made of petroleum coke and petrochemical sludge
Fuel Process Technol
(2012) - et al.
Effects of chemicals and blending petroleum coke on the properties of low-rank Indonesian coal water mixtures
Fuel Process Technol
(2008) - et al.
Rheology of Victorian Brown coal slurries. 1. Raw coal water
Fuel
(1987) - et al.
An investigation on effects of various parameters on viscosities of coal–water mixture prepared with Erzurum–Askale lignite coal
Fuel Process Technol
(2006) - et al.
Effect of coal particle size distribution, volume fraction and rank on the rheology of coal–water slurries
Fuel Process Technol
(2004) - et al.
The effects of dispersants (PSS–NSF) used in coal–water slurries on the grindability of coals of different structures
Fuel
(2005) - et al.
The effect of anionic dispersants on grindability of different rank coals
Int J Miner Process
(2005) - et al.
The effect of coal properties on the viscosity of coal–water slurries
Fuel
(2002) - et al.
The effect of chemicals on the viscosity and stability of coal water slurries
Int J Miner Process
(2003)
The effect of carboxymethyl cellulose (CMC) on the stability of coal–water slurries
Fuel
Slurry rheology in wet ultrafine grinding of industrial minerals: a review
Powder Technol
Slip flow of coal water slurries in pipelines
Fuel
Rheological behavior and wall slip of concentrated coal water slurry in pipe flows
Chem Eng Prog
Wall slip and rheological behavior of petroleum-coke sludge slurries flowing in pipelines
Powder Technol
Cited by (23)
Effect of particle size distribution of tailings on pressure gradient and drag reduction characteristics of non-cemented paste considering wall slip
2024, Case Studies in Construction MaterialsA review on slurry-based fuels for engines and furnaces: Preparation, stability, emission characteristics and applications
2024, International Journal of ThermofluidsA new pressure gradient model of slurry shield pipeline system coupling with rheological properties and wall slip behaviour under sandy stratum
2023, Tunnelling and Underground Space Technology