Measurement of bulk modulus of elasticity of dense pastes and its effects on flow rate in long pipeline

Advances in Mechanical Engineering

Zhang

et al. 2019

Self Cite

Calcium carbide sludge is a kind of dense paste; when transported by pipeline, the pressure loss is enormous. However, how to calculate the pressure loss accurately has not been solved until now. This article aims to present a new method to build a pressure loss calculation model based on the experimental data of pipeline transportation. To determine the relationship between the pressure loss and the properties of calcium carbide sludge, a new circulating pipeline testing apparatus was designed. The test studied pressure losses arising from changes in the mass concentration of the paste, flow velocity, pipe diameter, and pipe length. Analyzing the obtained data by means of nonlinear curve fitting, the adsorption coefficient and viscosity coefficient were defined and then the calculation formula was deduced. Finally, the calculation formula was verified for a project pipeline with a relatively large diameter equal to φ200 mm and the same parameters as those of industrial applications. The results show that under the appropriate conditions of applying the model, the relative error is less than 20%, so the model can be applied to engineering pressure loss estimation. This method provides a suitable pipe transportation calculation method for dense paste, combining experimental data and theoretical derivation.

Section: Transportation Resistance As Influenced By the Concentrationmentioning

confidence: 99%

Pressure loss characteristics and calculation model of calcium carbide sludge flow in a pipe

Advances in Mechanical Engineering

Zhang

et al. 2019

Self Cite

“…Dense pastes are produced in industry or municipal sewage treatment progresses and the annual outputs are enormous around the world. 1 Taking coal slime as an example, its production will exceed 300 million tons until 2020 in China. 2 In order to make full use of them most dense pastes have been sent to CFB (Circulating Fluidized Bed) to be burned for power generation.…”

Section: Introductionmentioning

confidence: 99%

Developments in how the boundary layer lower the pipe drag reduction in transport of dense paste

Zhang

Jiang

et al. 2020

Lubrication Science

Wall slip phenomenon occurs near the inner wall of pipe when dense paste is transported, and it reduces the frictional resistance loss and saves energy. To determine how the boundary layer influences the flowing law, more pipe transporting tests have been performed. Taking coal slime as test material, water and PEO (plasma electrolytic oxidation) were injected into the boundary layer part. Many factors, such as mass concentration, pipe diameter, flow velocity, boundary layer thickness, were systematically studied on their changes influencing pressure loss. The pressure loss decreases exponentially with the increase of boundary layer thickness. Drag reduction effect of PEO as the injecting liquid is better than water, and the pressure loss declines about 20%. The smaller the pipe diameter, lower flow rate, and the more obvious the drag reduction effect will be.

“…The most recommended resolution is to use those materials as thermal source in power generation after being simply processed. In China, approximately 63.9 million tons of coal slime had been sent to circulating fluidized bed boilers as a partial substitution of coal fuel from 2002 to 2008, resulting in an economic benefit of about 10.1 billion CNY . Recycling of dense paste requires pipeline transportation from the producer to circulating fluidized bed, which across several hundreds of meters in distance and several tens of meters in height usually .…”

Section: Introductionmentioning

confidence: 99%

“…1,2 After processed by filter pressure, solid wastes are much higher solids content than were previously deemed acceptable and their apparent viscosity ranges from tens to hundreds of Pa s À1 with a state of somehow between solid and fluid. 2 Paste refers to 'fine-particle high-concentration slurry', 3 so we call these tailings and other similar wastes or byproducts in industry 'dense paste'.…”

Section: Introductionmentioning

confidence: 99%

“…In China, approximately 63.9 million tons of coal slime had been sent to circulating fluidized bed boilers as a partial substitution of coal fuel from 2002 to 2008, resulting in an economic benefit of about 10.1 billion CNY. 2 Recycling of dense paste requires pipeline transportation from the producer to circulating fluidized bed, which across several hundreds of meters in distance and several tens of meters in height usually. 4 When the pumped stress is smaller than yield stress of the dense paste, it stays, which limit the long-distance transport of it.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Experimental research of how the boundary layer lower the pipe drag reduction in transport of dense paste

Chunhui

et al. 2017

Lubrication Science

A thin boundary layer formed on inner‐pipe wall and brought out wall slip phenomenon when dense pastes were transported in pipe as plug flow. The boundary layer is called slip layer as well, which reduced frictional pressure loss, increased the conveying distance and saved energy consequently. In order to find out the relationship between the properties of boundary layer and the pressure loss, the design of the liquid injection equipment was detailed in this paper. The liquid (such as water, oil or polymer solution) is injected from the pump into the pipe downstream at comparatively small flowrates and formed a lubricating annulus adjacent on the pipe inner wall. By taking coal slime as an example, the test studied pressure loss result from the change of pipeline features and the thickness of boundary layer systematically. Results show that the pressure loss reduced exponentially with the increase of the boundary layer thickness, and the greater the diameter, the smaller the pressure loss. When the shear rate of the boundary layer was getting higher, the lubrication layer played more efficiency on the reduction of the shear stress. Furthermore, these results provide preview for our understanding of the fundamental processes of slime pipe flow and how such flows can be better modelled, optimised and controlled. Copyright © 2017 John Wiley & Sons, Ltd.