The Demise of the Deseret Iron Company: Failure of the Brick Furnace Lining Technology

The Demise of the Deseret Iron Company: Failure of the Brick Furnace Lining Technology

BY MORRIS A. SHIRTS AND WILLIAM T. PARRY

IN 1851-52 THE MORMON CHURCH BEGAN a systematic plan of industrial development. Sermons were delivered in church meetings, editorials were published in the Deseret News, individuals were called to establish various home industries encouraged by the legislature, and emigrating European members were directed to bring designs and tools.

A colony was established at Parowan in 1850-51 to serve as a supply base on the Salt Lake to California route and to initiate an iron industry. This colony was composed of farmers, frontiersmen, and a cadre (primarily from England, Scotland, Wales, and Ireland) experienced in coal mining and iron working. After the first harvest had been completed some of them were sent to establish a pioneer iron company at Cedar City, twenty miles to the south of Parowan. This was later reorganized as the Deseret Iron Company and provided the organizational structure to implement the objectives of the Iron Mission. The first iron sample was not produced until September 1852. The project was officially terminated in October 1858.

Careful sifting and interpretation of information from numerous sources, a partial excavation of the iron works site, and an examination of furnace technology reveal at least a dozen reasons for the demise of the Deseret Iron Company, among them, a poor choice of original location of the iron works, unsuitable materials used in the construction of the furnace lining, erratic power supply, inadequate fuel supply, inadequate financing, erratic climate, lack of suitable technology for local ore, management flaws, disunity of personnel, Indian problems, and the Utah War. The focus of this essay is on materials used in construction of the lining of the furnace.

DESIGN OF A NINETEENTH-CENTURY BLAST FURNACE

A typical 1850 iron blast furnace consisted of an outside wall or stack of dressed stone blocks and an inside wall or lining of refractory brick or stone. The size varied with the type of fuel and ore used. Generally, the furnace was about 25 feet square at the base and 50 feet high. The foundation on which the stack stood had to support the weight of the stack, lining, and burden of fuel, limestone, and iron ore.

The furnace lining consisted of the hearth, the bosh (or bosch), and the upper lining. The hearth was a square masonry box at the bottom of the furnace designed to contain the liquid iron and slag. The bosh was a masonry, funnel-shaped section that capped the hearth and flared upward and outward to reach a diameter of approximately six feet and served to support the furnace burden, keeping it from entering the hearth. The lining proper (funnel or tunnel) sloped inward and upward, slightly resembling a tall, inverted funnel which extended to the top of the furnace, or the mouth, and was approximately three feet in diameter at that point. The furnace was charged (or burdened) through the mouth (figure 2).

An arch built into one side of the furnace stack at ground level gave the iron workers access to the furnace lining through which liquid iron and slag were drawn. This was referred to as the working, front, or tymp (delivery point) arch. Smaller arches (torino or tuyere arches) built into the two opposite sides were fitted with pipes with adjustable nozzles (tuyeres) by which a blast of air was directed to increase the combustion efficiency of the fuel.

The Deseret Iron Company constructed at least three blast furnaces in 1852, 1853, and 1854. The 1854 furnace was the largest and followed this general design (figure 1). It measured 21 feet at the base and stood 35 feet high. The hearth measured 23 inches square and the diameter of the bosh was 6 feet, 6 inches. The mouth of the furnace was 3 feet, 6 inches in diameter. It closely resembled the restored Maramec Spring furnace in southern Missouri, except for a side delivery charging arrangement near the top (figure 3). Being burdened (or charged) from the top, most furnaces were built at the base of a small hill with a bridge connecting the top of the furnace with the top of the hill. This was covered to keep the ore, limestone, and coke dry and was called the bridge house. The Deseret Iron Company utilized an endless chain and a winching system that lifted the charges from the ground to the side delivery door and into the furnace mouth (figure 1), although one reference mentions a bridge house.

THE TECHNOLOGY OF THE SMELTING PROCESS

The separation of iron from iron ore involved more than just melting the iron ore. The smelting process took place inside the blast furnace in a series of complex chemical and physical reactions that could not be observed directly for obvious reasons. Our understanding of them has been gained empirically and through theoretical considerations that give us a great technological advantage over the early iron workers who had no such thing as a complete periodical table of the elements. They had to rely on a basic recipe that was constantly adjusted—as grandmother did with her chocolate cake recipe.

At the risk of oversimplification, the iron smelting process is explained essentially as follows. The high temperature needed in the blast furnace began with the combustion of the fuel (usually coke or charcoal). This was aided by a blast of air injected by nozzles (or tuyeres) through the furnace lining near the junction of the hearth and the bosh. In 1829 it was discovered that the efficiency of the blast could be improved by preheating the blast. The combustion of fuel gave off carbon monoxide, a powerful reducing agent, that, combining with the oxygen of the iron oxide (iron ore), reduced it. The reaction (plus other concurrent ones) generated more heat, raising the furnace temperature to over 2800 °F or near the melting point of iron. The iron was freed from the iron ore in a liquid state and collected in the hearth. Many other chemical reactions were taking place (including those involving the limestone), producing gases that were driven off through the mouth of the furnace. Other molten compounds were produced by the fusion of the limestone, which absorbed unwanted elements in the form of a hot, thick liquid called slag or cinder. In addition, the slag floated on top of the liquid iron in the hearth, keeping it from cooling until the iron could be trapped or drawn off and cast into molds as pig iron. The cinder was dumped into lagoons or onto cinder piles for disposal.

THE ROLE OF REFRACTORY MATERIALS IN THE FURNACE LINING

The lining of the furnace, including the hearth, the bosh, and the lining proper, served as a "holding pot" to contain the furnace burden while it was being smelted. In order to successfully do this, materials used in the furnace lining needed to meet very stringent requirements:

1. Withstand all temperatures up to the melting point of iron. 2. Resist thermal shock and sudden changes in temperature. 3. Resist the actions of hot liquids—slag and iron. 4. Resist the impact and abrasiveness of the furnace burden as it moved down through the furnace. 5. Resist the compression stresses at all temperatures. 6. Resist the actions of gases, oxides, and salts that penetrate lining materials.

To fulfill all these requirements the brick of the hearth, the bosh, and the upper lining should have contained 40 to 45 percent dumina and been low in iron content. The bosh brick, especially, had to be highly refractory.

Modern manufacturers produce a wide variety of refractories to meet a wide range of needs. For simplicity these are classified into four general groups (with a number of subgroups):

High Alumina Brick. These brick may contain as much as 90 percent alumina (aluminum oxide.) Other varieties contain around 60 percent alumina plus silica and minor quantities of other elements. These brick provide maximum resistance to abrasion, high temperature, and slag and metal penetration.

Basic Brick. The chief constituent is magnesium oxide (around 70-90 percent) with varying amounts of other elements, including approximately 9 percent chromium oxide. In some varieties the chromium oxide reaches 23 percent with the magnesium oxide dropping to around 34 percent. These brick are very resistive to spalling, high temperature, and structural distortion. The raw materials are imported chiefly from the Philippines and South Africa.

Fire Clay Brick. Because of its relatively low cost and availability this is the most useful of all refractories. It contains approximately 60 percent silica and 35 percent aluminum oxide with varying amounts of other elements depending upon the thermal and mechanical needs. They can be mixed specifically for abrasive resistance, spalling, or thermal resistance or a general compromise for general application.

Silica Brick. These brick contain as much as 95 percent silica but are not recommended for iron blast furnaces. This material has excellent resistance to abrasion and therefore is used extensively in coke ovens.

The Deseret Iron Company had no detailed specifications or technology such as given above. They could not mix constituents scientifically and were limited to what nature provided locally.

Failure of the brick to meet the requirements doomed the furnace lining in any sustained operation, requiring its replacement and probably the complete reconstruction of the entire furnace. Such failure would be extremely costly in terms of time, energy, and production—to say nothing of the despair and discontent of those having to do the work.

Resistance to high temperature is particularly important in the hearth and bosh where the highest temperatures are developed. This is especially true in cases where coke is used as the fuel and where the blast is preheated. The hot slag and the molten iron are exceedingly active chemically and physically and, depending on the acid balance of the system and the individual constituents, can work havoc as they come into contact with the furnace lining. Gases produced through chemical and physical reactions can and do create disintegration, sometimes with explosive force. For example, too much moisture contained in any furnace lining or burden constituent may develop pockets of trapped steam that could rip the furnace lining apart. Sudden changes in temperature may also cause the lining to spall (breaking away or peeling off the surface of the refractory).

The fusing (melting) and vitrification (turning into glass) of the lining materials make the refractories soft, weak, and unfit. The furnace burden, containing extremely hard bits of iron ore, as well as limestone and coke, is very abrasive and literally wears out a soft furnace lining. The materials of a furnace lining, therefore, had to be selected with great care. Sandstone was traditionally used, but the development of coke as a furnace fuel and the hot blast predestined the use of higher refractory materials in the furnace lining. According to some experts, the use of sandstone was superseded somewhere around 1846 by fire brick, quartzite, and mica schist. Although some of these materials had been discovered in the United States, they were not widely known. Fire brick containing alumina (known as Stourbridge brick) made in England was exported to the eastern United States and Canada, but, of course, none was transported to Utah.

Iron workers of the 1850 era who had received their training and experience in England or in the eastern United States would have been familiar with the mica schist, quartzite, and Stourbridge brick materials available for construction of furnaces there, but deposits of these are very rare in Utah and were undiscovered at that time. Even if they had been known, shipping by ox-drawn wagons over non-existent roads from sites discovered later in Wah Wah and Bull valleys and from west of Utah Lake to Cedar City would have been prohibitive.

BRICK SAMPLES

In the fall of 1982 construction crews of the Cedar City Corporation were updating the underground utilities and the curbs and gutters at the 100 East and 400 North intersection in Cedar City. Quantities of coke, coal, charcoal, cinder (slag), and furnace rubble were exposed (figure 4). Morris A. Shirts, knowing that this location had been previously documented as the site of the 1854 blast furnace of the Deseret Iron Company, collected and catalogued numerous samples of these exposed materials. Much of the collection consisted of blackened, fragmented, and distorted brick and sandstone specimens. A number of these were sent to William T. Parry at the University of Utah for analysis to determine the extent to which the brick samples met the above described requirements and the role they might have played in the failure of the Deseret Iron Company to produce large quantities of pig iron.

SOME ESSENTIAL CHEMISTRY

The chemical and physical reactions that take place inside a blast furnace are too complex to explain here. However, the following relate specifically to the function of the furnace lining.

Eutectic Temperature. The lowering of the melting point of a mixture can be explained using silica and lime, two of the constituents found in the brick lining, as an example. The addition of lime to silica will lower the melting point of the mixture below the melting point of silica and likewise the addition of silica to lime will lower the melting point of the mixture below the melting point of lime. The lowest melting point obtained in the mixture of lime and silica is called the eutectic at 2617 °F, and any mixture of lime and silica will begin to melt or fuse at the eutectic temperature. Some melting points and eutectic temperatures for components likely to have been used in early brick manufacture are:

From this data, it can be seen that resistance to the molten iron in the blast furnace required bricks of silica and alumina: other mixtures would partially melt at their eutectic temperatures before the melting point of iron was reached. The quartzite refractory used in the eastern United States corresponded to relatively pure silica with a melting temperature of 1610 °C (2950 °F) which is higher than the melting point of iron, enabling it to remain stable while the iron ore was smelted.

Phase Changes. Some of the chemical compounds used in bricks or formed in bricks during chemical reactions change their crystal structure at elevated temperatures. One of these is quartz, the most common form of silica, and a common constituent of sandstone. This form of silica undergoes a structural change and becomes beta quartz at 573 °C (1063 °F) with a volume increase of 20 percent. Beta quartz then changes to tridymite at 867 °C (1593 °F) but, if a flux such as lime is present, a different substance is formed called cristobalite. Quartz melts at 1610°C (2678°F) and recrystallizes to cristobalite. The low temperature form of calcium silicate forms at 500 °C (932 °F) and changes to a different structure at 1125°C (2057 °F) called alpha calcium silicate.

Two other chemical reactions should also be understood. First, silica reacts with any lime present in the brick to produce a compound known as calcium silicate plus carbon dioxide gas at temperatures above about 500°C (932 °F), producing softened and bloated brick. Second, reducing gases generated in the furnace, which are responsible for reducing iron oxide in the iron ore to molten iron, may also reduce any iron present in the brick lining (usually red brick) to molten iron, causing the brick to collapse or deteriorate.

EXAMINATION OF BLAST FURNACE BRICKS

Samples of brick collected during excavation of the blast furnace site were examined in detail. The techniques used in examining the bricks included simple chemical analysis for the presence of carbonate rock constituents in the bricks, microscopic examination to identify chemical compounds in the bricks, and x-ray diffraction analysis to identify the structural state of the chemical compounds. An analysis of brick samples from the Deseret Iron Company blast furnace site reveals:

1. Little alumina is present—a constituent necessary for the production of high refractory brick.

2. The presence of large amounts of quartz (silica oxide), iron oxide (in the red variety), and calcium carbonate.

3. Physical and chemical reactions with these brick constituents are listed below and shown in figures 5 through 8. a. The bricks melted below the melting point of iron (figure 5).

b. Reaction of quartz and calcium carbonate produced calcium silicate and carbon dioxide gas which produced large bubbles within the partially melted brick (figures 5 and 6).

c. Much of the brick was essentially transformed into cinder (slag) due to the high calcium carbonate (limestone) present as happened in the furnace proper.

d. Reaction between carbon monoxide produced in the furnace and the brick reduced iron oxide in the brick to metallic iron, thus weakening the brick.

4. Bricks spalled or fractured from volume expansion during heating and cooling (figures 7a and 7b).

CONCLUSIONS

The brick lining failed to meet the requirements imposed for successful blast furnace operation. The only available local materials made a brick that was not mechanically strong enough to support the furnace burden to begin the furnace operation. The bricks then failed to withstand the high temperatures in the blast furnace. Due to the composition of the brick, essentially silica and lime, the bricks melted at temperatures as low as 1400 °C (2552 °F). Lime and silica reacted to produce calcium silicate and carbon dioxide gas that, upon expansion, produced large gas bubbles in the brick, distorting and fracturing them. The silica component of the bricks underwent phase changes to the beta form and to cristobalite that involved large volume changes and resultant weakening of the bricks. The iron oxide coloring matter in the bricks was reduced to molten iron in the furnace lining, resulting in their deterioration. Some of the bricks revealed serious spalling. The net effect of all these brick problems could have been disastrous for any single run of the furnace. The hearth lining could have been breached, permitting premature escape of iron, slag, or furnace gases. The bosh could have collapsed, allowing brick lining and the charge to fall into the hearth (figure 8). The tuyeres, through which the air was blown to enhance the combustion of the fuel, could have collapsed, shutting off the air and prematurely plugging the furnace; or the entire stack lining could have collapsed, as is indicated in many of the journals and minutes of the Deseret Iron Company. Any or all of these effects could have contributed substantially to the failure of the iron-making operation. This probably influenced the decision to revert back to the use of sandstone for the lining of the 1854 furnace and continued experimentation with lining material. Since the sandstone deposits near Cedar City were the chief sources of the material from which the bricks were made, similar results were probably obtained. Most of the sandstone lining may have endured long enough for furnace runs of one or two days; but, like the brick, it would have disintegrated before much iron was produced. Specimens of muscovite quartz sandstone found at the furnace site and not yet analyzed may have served much better as furnace lining, perhaps making longer furnace runs possible near the end of the project; but the determination and tenacity of these early iron workers were evidently exceeded by the refractory problems they encountered early in the project.

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