skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Phase shift method to estimate solids circulation rate in circulating fluidized beds

Abstract

While solids circulation rate is a critical design and control parameter in circulating fluidized bed (CFB) reactor systems, there are no available techniques to measure it directly at conditions of industrial interest. Cold flow tests have been conducted at NETL in an industrial scale CFB unit where the solids flow has been the topic of research in order to develop an independent method which could be applied to CFBs operating under the erosive and corrosive high temperatures and pressures of a coal fired boiler or gasifier. The dynamic responses of the CFB loop to modest modulated aeration flows in the return leg or standpipe were imposed to establish a periodic response in the unit without causing upset in the process performance. The resulting periodic behavior could then be analyzed with a dynamic model and the average solids circulation rate could be established. This method was applied to the CFB unit operated under a wide range of operating conditions including fast fluidization, core annular flow, dilute and dense transport, and dense suspension upflow. In addition, the system was operated in both low and high total solids inventories to explore the influence of inventory limiting cases on the estimated results. The techniquemore » was able to estimate the solids circulation rate for all transport circulating fluidized beds when operating above upper transport velocity, U{sub tr2}. For CFB operating in the fast fluidized bed regime (i.e., U{sub g}< U{sub tr2}), the phase shift technique was not successful. The riser pressure drop becomes independent of the solids circulation rate and the mass flow rate out of the riser does not show modulated behavior even when the riser pressure drop does.« less

Authors:
 [1];  [2];  [3]
  1. U.S. DOE (retired)
  2. REM
  3. U.S. DOE
Publication Date:
Research Org.:
National Energy Technology Lab. (NETL), Pittsburgh, PA, and Morgantown, WV (United States). In-house Research; National Energy Technology Lab. (NETL), Pittsburgh, PA, and Morgantown, WV (United States)
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
OSTI Identifier:
1129744
Report Number(s):
NETL-PUB-414
Journal ID: ISSN 0888--5885
Resource Type:
Journal Article
Resource Relation:
Journal Name: Ind. Eng.Chem. Res.; Journal Volume: 52; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING

Citation Formats

Ludlow, James Christopher, Panday, Rupen, and Shadle, Lawrence J. Phase shift method to estimate solids circulation rate in circulating fluidized beds. United States: N. p., 2013. Web. doi:10.1021/ie301275c.
Ludlow, James Christopher, Panday, Rupen, & Shadle, Lawrence J. Phase shift method to estimate solids circulation rate in circulating fluidized beds. United States. doi:10.1021/ie301275c.
Ludlow, James Christopher, Panday, Rupen, and Shadle, Lawrence J. 2013. "Phase shift method to estimate solids circulation rate in circulating fluidized beds". United States. doi:10.1021/ie301275c.
@article{osti_1129744,
title = {Phase shift method to estimate solids circulation rate in circulating fluidized beds},
author = {Ludlow, James Christopher and Panday, Rupen and Shadle, Lawrence J.},
abstractNote = {While solids circulation rate is a critical design and control parameter in circulating fluidized bed (CFB) reactor systems, there are no available techniques to measure it directly at conditions of industrial interest. Cold flow tests have been conducted at NETL in an industrial scale CFB unit where the solids flow has been the topic of research in order to develop an independent method which could be applied to CFBs operating under the erosive and corrosive high temperatures and pressures of a coal fired boiler or gasifier. The dynamic responses of the CFB loop to modest modulated aeration flows in the return leg or standpipe were imposed to establish a periodic response in the unit without causing upset in the process performance. The resulting periodic behavior could then be analyzed with a dynamic model and the average solids circulation rate could be established. This method was applied to the CFB unit operated under a wide range of operating conditions including fast fluidization, core annular flow, dilute and dense transport, and dense suspension upflow. In addition, the system was operated in both low and high total solids inventories to explore the influence of inventory limiting cases on the estimated results. The technique was able to estimate the solids circulation rate for all transport circulating fluidized beds when operating above upper transport velocity, U{sub tr2}. For CFB operating in the fast fluidized bed regime (i.e., U{sub g}< U{sub tr2}), the phase shift technique was not successful. The riser pressure drop becomes independent of the solids circulation rate and the mass flow rate out of the riser does not show modulated behavior even when the riser pressure drop does.},
doi = {10.1021/ie301275c},
journal = {Ind. Eng.Chem. Res.},
number = 5,
volume = 52,
place = {United States},
year = 2013,
month = 1
}
  • Circulating fluidized beds (CFB) are currently used in many industrial processes for noncatalytic and catalytic because its effective control is the key to smooth operation of a CFB system. This paper presents a method for solids flow metering from pressure drop measurements in the standpipe dense phase. A model based on the Ergun equation is developed to predict the solids flow rate and voidage in the dense phase of the standpipe. The profile of the solids flow rate under unsteady state is also presented. With the use of this method, the dynamic response time at different locations along the standpipemore » of a pilot-scale fluidized bed operating at ambient conditions with 812 mu m cork particles is estimated successfully. Through the use of a pressure balance analysis, solids flow models for the standpipe, riser, and other sections of the flow loop are combined to give an integrated CFB model.« less
  • A method is described to independently estimate the solids velocity and voidage in the moving bed portion of the NETL circulating fluidized bed (CFB). These quantities are used by a device that continuously measures the solids circulation rate. The device is based on the use of a rotating Spiral vane installed in the standpipe of a circulating fluid bed (CFB). Correlations were developed from transient experiments and steady state mass balance data to correct the solids velocity and solids fraction in the standpipe as a function of standpipe aeration rate. A set of statisticallydesigned experiments was used to establish themore » need for these corrections and to verify the accuracy of solid circulation rate measurements after correction. The differences between the original and corrected measurements were quantitatively compared.« less
  • A new experimental technique has been developed to measure time-averaged volume fractions of particles and of the gas in fluidized beds involving particles of two sizes, such as glass beads and leaded glass beads, using two radiation densitometers. In such fluidized beds, the coarse and the fine particles segregate. The boundary line of segregation was found as a function of jet velocity and grid flow rate. This experimental technique was then applied to the removal of pyrites from a coal-pyrite mixture in a fluidized bed with a jet.
  • We describe an innovative method for measuring particle motion inside spouted fluidized beds. The method uses a magnetic tracer particle, which follows the bulk particle flow and is continuously tracked by multiple magnetic field detectors located outside the bed. We analyze signals from the detectors to determine the tracer position at each instant in time. From statistical analysis of the tracer trajectory, characteristic measures of the bulk particle flow, such as the average recirculation frequency, can be determined as a function of operating conditions. For experiments with a range of particle sizes and densities in a 3.9-cm-diameter spouted bed, wemore » find that average solids recirculation rates correlate with excess velocity (superficial minus minimum spouting velocity), particle density, and bed depth.« less