Acid brick lining

In sulfuric acid production, acid brick lining of membrane coated mild steel tanks and reaction vessels is considered the most durable and versatile construction material for the sulfuric acid plant. Such linings wiil reduce the steel shell temperature and prevent erosion of the normally protective iron sulfate film that forms in stagnant, concentrated (oxidizing) sulfuric acid. Dilute (red uC ing) sulfuric acid solutions are very corrosive to carbon steel, which must be protected by impermeable (e.g., elastomeric) membranes and acid brick lining systems. Such acid brick linings often employ membranes comprising a thin film of Teflon or Kynar sandwiched between layers of asphalt mastic. 

The designer may note that if he requires the most cleanable surface, yet the least expensive lining, it is entirely feasible to mate porcelain brick as a facing with an acid brick lining, since their coefficients of thermal expansion are quite similar. 

The relatively severe conditions in an acid sulfite digester dictate the use of a multiple layer acid brick lining. The lining must be carefully selected and specified since these units operate at elevated temperatures and pressures with very acidic chemicals. Improper selection, design, specification, or installation can result in an unacceptably short lining life, lining failure, or vessel failure. 

These vessels are operated under extreme chemical and high temperature conditions. They are, therefore, usually brick lined. The lining consists of a polyvinyl chloride sheet membrane applied to the steel shell with an acid brick lining set in furan mortar installed over the membrane. The vessel is occasionally exposed to a caustic solution for cleaning and, therefore, a partial carbon brick lining may be installed in the lower wall area and floor. These lower areas of the vessel are normally where the most maintenance is required. Eroded mortar joints may need repointing and softened and eroded brick may need to be replaced. 

I— Leaks through acid brick lining or floor. (Detected by holing of steel tank, or wet spots, discoloration, or collapse of concrete.)... 

Figure 52-1 Acid brick lining in throat of a scrubber in a large power plant. Smeared surface is an immediate indication to the inspector that the mason has covered up voids and pinholes in the joints.

Open-end drain hubs should be located at all tanks, towers, exchangers and associated equipment for fast drainage. Large drains at towers or tanks may be more conveniently handled by an acid-proof concrete or acid-brick-lined sewer box rather than an open-end drain hub. 

These materials are also used extensively as membranes in acid-brick-lined vessels to protect the steel shell from corrosive attack. The add-brick lining, in turn, protects the elastomer from abrasion and excessive temperature. Another major use is as an impermeable lining for settling ponds and basins. These materials are employed to prevent pond contaminants from seeping into the soil and causing pollution of groundwater and contamination of the soil. 

Elastomers are also used extensively as membrane linings in acid-brick lined vessels to protect the steel shell from corrosive attack, while the acid-brick lining in turn protects the elastomer from abrasion and excessive temperature. 

Absorption and Drying Towers. Towers are typically carbon steel vessels lined with acid proof brick and mortar and packed with ceramic saddles (see Absorption). More recently, all metal towers having no brick lining have been built from high siHcon stainless steel alloys such as Sandvik SX or Saramet. 

Acid-Proof Vessel Ccvtisrrucfkin with Membrane and Brick Linings, N.-5CI Committee Report, Co.w.s/on i 95l-204t (March 1957),... 

The shell may be of metal (steel, alloy, or non-ferrous), plastic, wood or some combination which may require the addition of liners or inner layers of rubber, plastic or brick. The mechanical problems of attaching inner nozzles, supports and brick require considerable attention that is not an integral part of sizing the equipment. Figures 9-2A-C show a typical large steel brick-lined-membrane lined tower with corbeled brick support locations. In these towers, temperature and/or corrosive conditions usually dictate the internal lining, and the selection of the proper acid- (or alkali-) proof cements. 

Brick Construction Brick-lined construction can be used for many severely corrosive conditions under which high alloys would fail. Brick linings can be installed over metal, concrete, and fiberglass structures. Acid-resistant bricks are made from carbon, red shale, or acid-resistant refractory materials. Red-shale brick is not used above 175°C (350°F) because of spalling. Acid-resistant refractories can be used up to 870°C (1600°F). See Table 25-10. 

The hrst production step involves recovery of the metal from spodumene. The naturahy occurring ore, alpha-spodumene is heated in a brick-lined rotary kiln at a temperature between 1,075 to 1,100°C. This converts the alpha form to a more reactive form, beta-spodumene. The beta form is heated in a rotary kiln at 250°C with an excess of 93% sulfuric acid. The metal reacts with acid forming hthium sulfate. The kiln discharge is leached with water to separate water-soluble hthium sulfate from several impurity metals. Aqueous solution containing excess sulfuric acid is then neutrahzed by treatment with an excess of ground calcium carbonate (limestone). The solution is fdtered to... 

Illmenite sand with steam and hydrochloric acid was handled in the spherical digesters. The temperature in the digesting process was ambient to more than 130°C. Therefore brick lining was applied on a butyl rubber lining 5 mm thick with hardness of 55°A. The rubber serves as a cushioning medium beneath the brick lining, as well as resisting the temperature at the brick rubber interface of about 100°C. 

Fig. 5.2. Spent acid decomposition furnace. It is brick lined steel 4 m diameter and 20 m long. The energy for decomposing H2S04(< ) into S02(g), 02(g) and H20(g) and for evaporating water is provided by burning molten sulfur and natural gas with hot air. Industrial details are given in Table 5.2.

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. 

Thermal insulation effects by limiting the substrate and membrane temperature to prevent thermal damage and (3) Reduce permeation of corrosive fluid to the substrate, thus minimizing its corrosion rate. CRM linings, such as acid brick and monolithic cements, also prevent "wash", which is the removal of the membrane or substrate corrosion products by the circulating medium. Even when the fluid eventually reaches the membrane or substrate surface, the amount is relatively small, thus limiting chemical attack, and any corrosion products are trapped beneath the masonry shield. 

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