Composition cycling

Briggs, J. P., Kane, D. M., Hudgins, R. R., and Silveston, P. L., Reduction of S02 emissions from an S02 converter by means of feed composition cycling to the final stage, in Proc. 

Forced Composition Cycling Experiments in a Fixed-Bed Ammonia Synthesis Reactor... 

The effect of feed composition cycling on the time-average rate and temperature profile was explored in the region of integral conversion in a laboratory fixed bed ammonia synthesis reactor. Experiments were carried out at 400°C and 2.38 MPa over 40/50 US mesh catalyst particles. The effect of various cycling parameters, such as cycle-period, cycle-split, and the mean composition, on the improvement in time-average rate over the steady state were investigated. 

Figure 2. Detail of the feed composition cycling and flow control equipment.

Equipment limitations dictated operating both reactors at 2.38 MPa, more than an order of magnitude below pressures encountered in commercial units. A few experiments performed at a total pressure 50% greater confirmed the results which now will be reported. These experiments suggest composition cycling will improve performance at pressures found in commercial units. 

Our demonstration that forced composition cycling of NHj synthesis over an iron catalyst dramatically increases catalyst activity and smooths the temperature profile in fixed catalyst beds seems to call for an examination of the application of the approach to full-scale reactors. There is a major process design hurdle which must be overcome, however. Industrial reactors give relatively low conversions of NH3 per pass, so... 

W.R.C. Graham and D.T. Lynch. CO oxidation on Pt Variable phasing of inputs during forced composition cycling. AlChEJ. 36 1796 (1990). 

A.K. Jain. P.L. Silveston. and R.R. Hudgins, Forced composition cycling experiments in a fixed-bed ammonia synthesis reactor. Chem. Reaction. Eng. 9 97 (1982). 

A. Nappi, L. Fabbricino, R.R. Hudgins, and P.L. Silveston. Influence of forced feed composition cycling on catalytic methanol synthesis. Can. J. Chem. Eng. 63 963 (1985). 

H.A. El Masry. The claus reaction Effects of forced feed composition cycling, Appl. Catal. 76 301 (1985). 

A CD modified by 6-naphthalene monosulfonic add and chain polyethers form rotaxane, further generating polyrotaxane where compositional cycles can move cyclically or linearly along with the main frame. This property sets it apart from traditional copolymers or quasi-mixtures. It allows this material to apply in the improvement of binding ability, handling characteristics, thermal properties, the control of viscosity and molecular arrangement. 

Fry M.R., Watson H., and Hatchman J.C. (1997) Design of a prototype fuel cell/composite cycle power station . Proceedings of the Institution of Mechanical Engineers (London), 211, Part A, 171-180. 

---