Notes on Differences in Collection Operations in the Mineral Wool Industry

23 June 2011 Steve Edris, Thermafiber

The VERTICAL COLLECTION design.

The collection chamber at Thermafiber is 10-15 feet long, about 6 feet wide.

At the end of the chamber is a vertical perforated belt moving belt, running at about 300 feet per minute (this is the 

fastest in the bonded lines)

The cupola produces at the same steady rate, pouring a thin stream of molten rock onto the spinners. Binder is sprayed 

onto the fibers through ports on the circumference edge of the spinners. Air flow comes from behind (and under 

cupola) to blow the fibers away from the spinners as they are formed. 

A stronger air flow pulls negative on the screen, sucking the now cooled, binder sprayed fibers against the moving 

vertical screen, forming a mat that is about 1-1.5 inches. This screen moves much faster than any other in the industry 

because it is vertical. Otherwise, you’d have the fiber mat slumping along the bottom curve. 

This design makes a cleaner product that is low in ‘shot’. Shot is ok for some products, but can’t be present in 

horticultural applications (tomatoes need a uniform density product without ‘shot’, as do other vegetables). The CHOH 

is not trapped. 

The HORIZONTAL COLLECTION design.

Everything is pretty much the same right up to the collection process. In the horizontal collection, the horizontal mat is 

much thicker. That belt moves at about 50 feet per minute, and CHOH is trapped in a thicker mat. The belt doesn’t have 

to move fast because you are not working against gravity as you are in the vertical design. However, there are some 

products you can’t make on a horizontal design. First, the shot remains in the bonded product. That’s okay for the 

products they make at that company, because that’s mostly insulation products where some amount of shot does not 

affect the final application. But you couldn’t sell to the horticultural markets with that product.

The DRUM COLLECTION design.

Again, it’s pretty much the same right up to the collection process. But then this is basically a totally different approach. 

Instead of spinners and a moving belt, imagine a piece of equipment that looks like your washing machine, except 

turned. The molten rock is poured from the cupola into this big spinning drum, like the inside of your washer. And the 

little holes in the inside where the water empties out of the washing machine....that’s where the air flows out of the 

spinning drum carrying with it the threads of mineral wool. Unlike the other two designs, the air flow is already 

contained within the drum, and it can be directed as an air stream that lends itself well to controls. Out of the holes 

flow the forming fibers coming out as a loose long flow of fibers that is pulled from the spinning drum. The air stream 

from the collection process can then be directed to either the hottest part of the cupola stack or to the RTO on the 

curing oven. Either way, you achieve really low emissions of the organics in the binder. 
Notes on the Origins and Cause of COS Emissions in Mineral Wool Industry

Chris Bullock, IIG 28 June 2011

IIG is not ‘afraid’ of adding pollution controls. They do NOT support NAIMA’s approach on the SBAR panel. They said 

the industry group will look stupid and ineffectual going forward with the proposed limits. They do not think industry 

should get a pass just because they claim to be small. IIG can meet the limits EPA will be proposing.

They wouldn’t have to install a new RTO. They route their collection emissions to the hottest part of their cupola stack. 

This causes the formaldehyde, MeOH and phenol to incinerate in the stack before being emitted to the atmosphere. 

IIG has done research to show the source of sulfur is the SLAG....COKE is the source of CO. Coke is not so much a 

contributor to formation of COS and SO2. They purchase low-sulfur slag locally so their costs are still low.

Chris Bullock, IIG 28 June 2011

We mine and melt our own rock so we have better control of our inputs. We can melt at higher temperatures. But we 

have a 50% cost increase to us on our raw materials.

Low sulfur slag is not an option (?)

Oxygen injection will increase the COS because it burns hotter (?)

We don’t have a sulfur compounds being emitted from our raw materials, because we don’t put sulfur containing raw 

materials in to start with. In order to have a problem with SO2 or COS, you have to have sulfur in your raw materials. 

We know exactly what we are melting. All the other companies do too, or they ought to. Everybody keeps records of 

their raw material inputs because you have to do that to keep a consistent and reliable end product. 

Where is the leveling of the playing field? We are good environmental stewards. Again, we don’t think industry should 

get a pass on regulation just because this industry is full of companies that say they are small.