November 17, 2021

It was a year ago that we tried a very unusual application. Screw presses are almost always used to separate liquid from organic material. In this case, however, the goal was to separate gas from rigid plastic foam.

We ended up with a remarkable technical success. You can see it in this video:
FOAM DEGASSING Video link https://youtu.be/7JPBNjqvrVo

Since we haven’t sold anything yet, it counts as a commercial failure.

The project arose from the fact that hazardous gases, pentanes, are used as blowing agents in the production of rigid foam board. Our goal was to crush scrap pieces in a screw press so that the gasses would be released. This was to be done in a press made in vapor-tight configuration so the gasses released would be collected.

The pentane being expelled is a flammable gas, which is why the vapor-tight (VT) configuration was selected. The fumes drawn from the press were to go to a thermal oxidizer for destruction.

We ran sample material in a CP-4 press and medium crushing resulted with 15 psi air pressure on the discharge cone. The next day severe crushing was achieved at 60 psi in a CP-6 press. Both presses were run at 120 Hertz, 40 rpm.

We measured as-received bulk density twice: 0.75 ppcf (pounds per cubic foot) and 0.9 ppcf. The CP-4 press cake had 4.4 ppcf, while the CP-6 cake was 13 ppcf.

Throughput capacity was very low: 10 pounds per hour (pph) for the CP-4 and 30 pph for the CP-6. We recommended a Model KP-16 VT for a 1,000 pph application.

We were told that the board density is normally between 2.45 ppcf and 8.5 ppcf, and thickness between 2-1/2″ and 4-1/2″. There are various facing materials that range from foil to paper to fiberglass. We also found the following data about this type of product:
– Pentane in Foam: 7% by weight
– Density of Pentane Vapor: 0.19 pounds per cubic foot
– Pentane LEL (Lower Explosive Limit): 1.4%

In running the trials, we learned that pentanes are some of the primary blowing agents used in the production of polystyrene foam and other foams. Usually, a mixture of containing isopentane, and increasingly cyclopentane, is used for this purpose.

On the internet we found:
As one of North America’s most widely used, most readily available, and most cost-effective insulation products, Polyiso has been cited by the U.S. Environmental Protection Agency for its responsible impact on the environment.

Polyisocyanurate (Polyiso) is a closed-cell, rigid foam board insulation that is bonded to facers on both sides, which are composed of various organic and inorganic materials. Polyiso is used in roof, wall, ceiling and specialty applications within commercial and residential buildings of all types. Because of its high thermal performance, it is the product of choice for energy-aware architects, specifiers, builders, building owners, contractors and consumers.

Because of their low boiling points, low cost, and relative safety, pentanes are used as a working medium in geothermal power stations and in some blended refrigerants. It is also used as a working medium in organic rankine cycles.

Pentanes are components of some fuels and are employed as specialty solvents in the laboratory. Their properties are very similar to those of butanes and hexanes. Pentanes are solvents in many ordinary products, e.g. in some pesticides.

Acid-catalyzed isomerization gives isopentane, which is used in producing high-octane fuels.

ISSUE #338