Chemical resistant brick

Refractory industry production of thermally and chemically resistant bricks and lining materials... 

The installation of a brick lining in a process vessel is a common design technique for protecting the vessel jacket from corrosive environments. A variety of highly chemically resistant bricks and mortars are available. 

The furan polymers are used as binders in mortars and grouts to achieve chemically resistant brick floors (e.g., carbon brick and red shale brick) and linings. In addition to exhibiting superior chemical resistance, these floors have excellent resistance to elevated temperatures and extreme thermal shock [2,6,7],... 

Refractory bricks and other materials are used, both with and without a lining between the steel and bricks, to enclose reaction chambers. Depending on the conditions to be withstood, the products used include basic and neutral materials with high silicon carbide bricks. The structure of a chemically resistant brick lining is shown schematically in Figure 20.80. 

FIGURE 20.79 Schematic of chemically resistant brick lining. 

Porcelain is one of the hardest and densist of chemical resistant bricks. It is resistant to a wide range of chemicals up to 1500°F/815°C and is composed of 85% alumina. Outstanding features are its ease of cleaning and nil absorption. 

Lining vessels and equipment using this type of construction consists of a membrane, acid-resistant bricks or tiles, and chemical-resistant mortar for joining the bricks (tiles) together. 

Red and blue acid-resistant bricks are resistant to all inorganic and organic chemicals, except for hydrofluoric acid and hot concentrated caustic alkalis. Acid-resistant fireclay bricks are used for conditions involving elevating temperatures and corrosive condensates. Highly vitrified materials such as chemical stoneware, porcelain and basalts are used for extremely severe duties or where contamination of the process liquors is undesirable. 

Other types of refractory that find use are forsterite, zirconia, and zircon. Acid-resisting bricks consisting of a dense body like stoneware are used for lining tanks and conduits in the chemical industry. Carbon blocks are used as linings for the crucibles of blast furnaces, very extensively in a number of countries and to a limited extent in the United States. Fusion-cast bricks of mullite or alumina are largely used to line glass tanks. 

Aspbalt Asphalt is used as a flexible protective coating, as a brick-lining membrane, and as a chemical-resisting floor covering and road surface. Resistant to acids and bases, alphalt is soluble in organic solvents such as ketones, most chlorinated hydrocarbons, and aromatic hydrocarbons. 

Sulfur Mortars Hot melt-and-pour sulfur mortars are ancient, doubtless one of the oldest of all chemical resistant materials still used today. They are very resistant to non-oxidizing acids and weak alkalies below 200°F over a pH range of 0-12. Three types of sulfur mortars are typically employed (1) One containing an all-silica filler with minimum plasticizer, used to bond acid brick (2) A mortar with an all-carbon filler and minimum plasticizer, used primarily to lay carbon brick for nitric-hydrofluoric acid pickling tanks (to clean stainless steels) and the underlying floors and (3) A much more flexible all-silica filled product with double the amount of plasticizer of the other two mortars, used to join vitrified clay (terra cotta) pipe conveying waste acids and other effluent chemicals, and to assemble "pole line hardware" for the power industry. 

Note In brick lining vessels, it is not a matter of particular concern that vessels be perfectly plumb. If the vessels have floating heads, then the piumbness does become very important. It is more critical for out work that we have the center line established, and then our other criteria, namely, out-of-roundness will tell us if the steel is acceptable for receiving a chemically-resistant masonry lining. 

Red shale and fireclay acid brick are probably the most widely used masonry materials in chemically-resistant systems. Many scrubbers, trenches, floors. 

The use of silica brick in chemical-resistant masonry is limited, because of high cost, to applications requiring a high degree of chemical resistance where traditional acid brick cannot be used, such as concentrated phosphoric acid free of fluorine. Silica brick, however, cannot be used in strong alkaline exposures or any concentrations of hydrofluoric acid. As with acid brick, its main function is to provide a barrier to abrasion and to protect other membranes or structures from chemical attack. Because brick porosity may be as high as 16%, silica brick is backed by an impermeable material and a support structure. 

Early chemical-resistant masonry usage of silica bricks employed them as refractories for steel furnace or coke oven applications. Typically these bricks had up to 3.5% flux additions (usually CaO), promoting bond formation at lower firing temperatures. 

Although published tests such as ASTM C-279 may be used to determine an acid brick s chemical resistance, no standard test exists to predict silica brick behavior. It is necessary to rely on personal experience or to evaluate a brick s performance in a simulated test environment. 

Chemical Resistance For acid proof construction, silica brick with an Si02 content below 98% should not be used. Materials that contain lower amounts of silica usually have a concentration of alkaline earth oxides (e.g., CaO, MgO) in the glassy bond phase. As a result, the bond phase will have poor resistance to acid which can lead to failure of the brick in service. 

Chimney Lining Brick. C-980-82 in 1984 Annual Book of ASTM Standards Section 4, Construction Vol. 4.05, Chemical-Resistant Materials Vitrified Clay, Concrete, Fiber-Cement Products Mortars, Masonry, pp 743-745 (1984). 

Carbon bricks are used in chemical-resistant construction in exposures which cannot readily be handled by other kinds of brick. Inasmuch as their cost is nearly 10 times that of shale or fireclay, and they provide not nearly as much insulation nor resistance to mechanical abuse, their selection is dictated by only the most compelling reasons. These reasons may be divided into four categories ... 

The block takes the place of additional courses of brick in further reducing the temperature at the hot face of the membrane to an acceptable level. The result is a thinner overall lining with added chemical resistance because of the closed-cell nature of the block. 

The insulating power and chemical resistance of the glass block allows for a thinner lining and better membrane protection for pickle tanks where stability is not a concern. The tank is first lined with the rubber membrane, the block is bonded over that with its urethane asphalt adhesive/membrane and finally a course of acid-resistant brick laid in acid-resistant mortar is placed over the block for mechanical protection. 

Porcelain brick are used as linings very occasionally where the need is primarily for (1) ease of cleaning, (2) product purity, (3) high wear resistance, and (4) high strength, all in combination with (5) best chemical resistance. In the dye industry, in particular, there is concern about inter-batch contamination and purity of colors. Porcelain brick are white, so that residues from earlier batches are easily visible. They have zero porosity, and the surfaces are glass smooth, so they may be easily cleaned. 

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