#SCALING UP IN SPLITPRINT SERIES#

Sometimes a particular scale cannot be achieved for a pilot plant at all. When the variables and the constants collide, severe processing problems such as plugging, inadequate gas contact time, or excessive heat loss, can result. For example, residence time and solid feed particle size are generally kept constant with scale, but the volume and linear dimensions of reactor vessels, the area of settlers and heat exchangers, and the sizes of piping/tubing and throttling valve orifices vary with scale, and to different powers of the scale factor.

Haiser was trying to get across to us with his lesson: that some factors change with scale, and others don’t. Within a process, there may be intermixing of factors that scale with those that will not. The pilot plant designer’s key problem is exactly what Mr. The Brobdingnag would be in serious trouble unless his physical form changed as he was scaled up… This of course puts some interesting limits on the size and shape of land animals, and goes some distance toward explaining why we find the largest animals in the sea. He then had us consider the Brobdingnags, who were 12 times as large in all dimensions as a regular human. Here, the problem was that the volume and hence mass was 12^3 as high, and yet the strength of the bones varied as their cross-sectional area, which would only increase by 12^2. (Scene from Gulliver's Travels, painting by Richard Redgrave, permanent collection, Victoria and Albert Museum, UK)

the area through which he would lose heat to the surroundings) was 1/12th that of a regular human- and hence his food intake would need to be 12 times as high, in relative terms. It is therefore no surprise that mice and small birds have to eat a large fraction of their body mass in food each day to stay alive. the number of cells available for heat generation) to surface area (i.e. He had us consider the Lilliputian- a person 1/12th the scale of a regular human. The Lilliputian’s volume, and hence mass, scaled with the cube of the scale dimension, whereas its surface area scaled with the square of the scale dimension. I don’t know what inspired this lesson, because it seems somewhat beyond the normal high school physics curriculum of the day- but it was obviously effective for me, as it got me thinking about scale, which is the stuff and trade of the pilot plant business. He did this by comparing a few factors associated with the scale of the Lilliputians’ and Brobdingnags in Swift’s Gulliver’s Travels, to show how the physics of scale affect the living things around us. (photograph of a mural of Gulliver with the Lilliputians on a toy shop in Bremen, painter unknown, photo by Javier Carro c/o Wikipedia) I had a memorable lesson in grade 13 physics- one which would be strangely prophetic of what I would do for the rest of my career. Our physics teacher, Richard Haiser, started the lesson in his deliciously Hungarian-spiced baritone: “Consider the Lilliputians…” Careful and creative design is necessary to ensure that the equipment will continue to work reliably for the duration of a campaign while maintaining sufficient process similarity to give reliable pilot-scale experimental data and observations. SPECIAL DESIGN CONSIDERATIONS FOR PILOT PLANTS: Article 6Ī good pilot-plant design must balance the need for physical and equipment similarity to the commercial process with the other goals of the pilot-plant program.

I hope it will serve as a guide for potential owners and operators of new pilot-plant equipment and facilities to help process developers identify common mistakes, strengthening their chance of success.

#SCALING UP IN SPLITPRINT SERIES#

In this series of articles, I’ll present a number of considerations and suggestions for both the project execution approach and the process engineering design of pilot-plant facilities from the perspective of someone who has designed, built, and operated these plants throughout my career.

Scaling up in splitprint