Rock Wool

General Definition

Mineral Wool: An inorganic fibrous substance outwardly resembling wool, presenting a mass of fine interlaced filaments. It is produced by steam blasting and cooling molten glass or a similar substance and is used as an insulator and a filtering material. Also called rock wool. It is both insect proof and fireproof, forms a desirable insulation and has many uses.

Uses of Mineral Wool

By industry figures from 1992, it is estimated that the potential use for mineral wool per year, (which includes rockwool), is approximately 938 million pounds or 469,000 tons.

Insulation - The major use of mineral wool is in insulation. It is non combustible and is widely used in high temperature applications and soundproofing. It is required to be used as a fire-stop in various wall applications by many fire codes. There are some applications where the mineral wool is actually made into fabric by conventional textile methods.

(See photos at http://www.inspect-ny.com/interiors/Rock_Wool_Insulation.htm)

Hydroponics - This is farming without the use of soil. Plant nutrients and water are added to plants that are supported in a matrix of mineral wool. Plant diseases and insect damage are evidently much less than in conventional farming. This technology is rapidly increasing in greenhouse applications around the world. Hydroponics is done on a large scale in many places.

(See photos and more information at: http://www.hydroponics101.com/sw63706.asp).

Manufacture

Mineral wool would be made in the AJT process by melting the material, drawing off the molten glass and subjecting it, while molten, to the disintegrating effect of steam or air under high pressure. The steam or air jet breaks or shears the molten slag stream into tiny globules and propels than through the air at high speed. In their flight, they are drawn into minute fibers.

Some material would be processed as loose wool. Other material is processed as batts, or other products. After being sprayed with a suitable bonding agent, the fibers for these products are drawn by suction onto a horizontally moving conveyor positioned below the process. The mat of tangled fibers formed on the conveyor is carried through an oven which cures the bonding agent, then to trimmers and guillotines which cut the product to size. The mat may be further processed into rigid sections for pipe insulation or insulation batts. The mats are made into many products for heat and sound insulation in buildings, transport vehicles and domestic appliances.

Economics of the Process

Evidently, the major expense in making commercial mineral wool is the high energy cost operation to melt the original glass material. In the AJT process, the large quantity of molten glass is a by-product of the ash waste treatment process and can almost be considered “free”. This should be a considerable economic advantage of making mineral wool by the AJT process.

It is estimated that in one year of operation that a normal AJT facility, two 7.5 MW furnaces, would process power plant or incinerator waste ash to produce 80,000 plus tons of mineral wool with an estimated retail value of at least $80,000,000. This is an amazing figure. It has the following implications:

(1) The payback time to recoup the initial cost of building the facility (approximately $10,000,00) and the cost of operating the facility for the first year (approximately $11,000,000), a total of $21,000,000, would be less than four months.
(2) The profit for the first year would be about $63,000,000.

The above figures assume that a charge of $46 per ton would be charged to the producers of the power plant or incinerator ash. This was a figure taken from a industry source and produces a net income of about $3,750,000 per year. It does not include any income from treating general hazardous waste material that runs about $200 per ton for disposal. Any income from this would add to the profits shown.

(THE ABOVE PROFIT FIGURES ARE HYPOTHETICAL BASED ON THE THEORETICAL OPERATION OF THE AJT PROCESS AND ARE IN NO WAY A GUARANTEE OF ACTUAL RESULTS.)