Chemical Engineering Science 63 (2008) 1741 – 1760 www.elsevier.com/locate/ces Horizontal pneumatic conveying from a fluidized bed J.A. Woods, R.B. Thorpe ∗ , S.E. Johnson Chemical Engineering, FEPS (J2), University of Surrey, Guildford, Surrey, GU2 7XH, UK Received 15 August 2007; received in revised form 12 November 2007; accepted 28 November 2007 Available online 11 February 2008 Abstract In this paper the feasibility of feeding a horizontal pneumatic conveying line directly from a fluidized bed is explored by investigating the relationships governing the solids mass flow rate in such a pipe as a function of both pressure drop and pipe length. Three different materials were fluidized by air and discharged though a 25 mm internal diameter pipe. Materials used were turnip seeds of mean diameter 1.5 mm, carbon steel shot of mean diameter 0.73 mm and plastic pellets of mean diameter 3.76 mm. Several pipe lengths were used, from 0.75 to 1.77 m. The experiments showed that it is feasible to feed directly from a fluidized bed to a horizontal pneumatic conveying line. The flow regime in the pipe was that of dense phase conveying also called slug flow. The data collected show that there is a clear relationship between the pressure drop down the conveying line and the discharge rate of solids from the line. The discharge rate is also dependent on the pipe length. In previous studies of pneumatic conveying, the solids and gas mass flow rates have been independently set, which cannot be done if the conveying line is fed from a fluidized bed. For a pipe fed from a fluidized bed, the solid and gas mass ratio are coupled and this was modelled using the theory for air-augmented granular discharge through an orifice in a hopper or silo of Nedderman et al. [1983. The effect of interstitial air pressure gradients on the discharge from bins. Powder Technology 35, 69–81], but as modified by Thorpe [1984. Air-augmented flow of granular materials through orifices. Ph.D. Thesis, University of Cambridge] for horizontal discharge. This was then combined with a modification of the theory of Konrad [1981. Ph.D. Dissertation, University of Cambridge] to give a prediction of the total pressure drop and the gas and solid mass flow rates. This combined model for dense-phase conveying from a fluidized bed was found to give an excellent fit to the data using the standard values for the constants in every equation. The predictions of the combined model also agree well with the experiments of Konrad [1981. Ph.D. Dissertation, University of Cambridge] for discharge from a hopper into a horizontal conveying line.  2007 Elsevier Ltd. All rights reserved. Keywords: Pneumatic conveying; Dense phase; Slug flow; Fluidized bed; Jet 1. Introduction This paper examines a low pressure drop method of launch- ing pneumatic conveying from a fluidized bed. This method presents several advantages in that it contains no moving parts and naturally conveys as dense phase slug flow, which is good for reducing attrition of the particles. In cases where particles are either fragile or going to be re-used many times, e.g. peb- bles for a curtain diverter system for a fusion power plant (Voss et al., 2000, 2002), attrition will be an issue. In pneumatic conveying both the solids and gas mass flow rates are usually independently set, which is not the case if the conveying line is fed from a fluidized bed. Therefore a method is required to predict the pressure drop directly from ∗ Corresponding author. Tel.: +44 1483 689 270; fax: +44 1483 686 581. E-mail address: Rex.Thorpe@surrey.ac.uk (R.B. Thorpe). 0009-2509/$ - see front matter  2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.ces.2007.11.040 the solids mass flow rate (or vice versa), with the gas flow rate a consequence. The approach that will be taken is to analyse the problem into two parts. The first part is the flow solids from the fluidized bed into the pipe; by analogy with fluid flow, this is like the flow through an orifice. The second part is the dense phase pneumatic conveying of solids down the horizontal pipe. The hypothesis is that the total pressure drop across the bed and pipe is simply the summation of the orifice and pipeline pressure drops: P total = P O + P P , (1) where P O is the pressure drop through the orifice and P P is the pressure drop down the pipe. The orifice pressure drop and the pipeline pressure drop must be related by the mass flow rates of gas and solids since these must be conserved as they flow down the pipe.