Construction of material

Resistance of molten black liquor slats containing NaC03, Na2S, and NaOH 

Resistance to gaseous reaction products such as Na and NaOH vapors as well as gasihcation syngas 

Resistance to thermal shock from temperature and gas pressure variations 

7 Anode Metal anodes consisting of noncorrosive stainless steel mesh can be utilized [76], but copper is not useful due to the toxicity of even trace copper ions to bacteria. The most versatile electrode material is carbon, available as compact graphite plates, rods, or granules, as fibrous material (felt, cloth, paper, fibers, and 

The materials of construction of the vessel or pipe and all internals (impeller or mixers, shaft, baffles, bearings, seals, and lid) must be compatible with the fluids and any solids that are to be mixed. For most mixing experiments the ability to see clearly what is happening inside the mixer is exfiemely useful, if not essential. Vessels or pipes made of a transparent material such as polymethylmethacrylate (PMMA Perspex or Lucite) or glass are ideal, provided that measurements are to be made at temperatures and pressures within the modest limits allowed by such materials (the glue used to seal PMMA vessels tends to fail at about 50°C). PMMA vessels up to about 1 m in diameter can be manufactured relatively simply. 

At larger scales, or in situations where elevated or reduced pressures or temperatures are required, the use of completely transparent mixing vessels is unlikely or impossible. For such situations metals such as steel or other metaUic alloys or plastics such as polythene can be used. In these situations the addition of windows in the side of the vessel can be extremely usefiil. 

The wet deck or surface, is the heart of most cooling towers. Generally, it takes the form of PVC (polyvinyl chloride) plastic film type surface. Water is made to spread out on this surface maximizing it s contact area with air to encourage evaporation. It consists of individual vacuum formed sheets with proprietary patterns of ridges. 

The Spray tree is used to distribute water over the wet deck in counterflow cooling towers. It can consist of a single header fitted with spray nozzles or, it can utilize spray branches with nozzles for wider coverage. Spray nozzle designers seek minimal pressure requirements and uniform coverage over wide flow ranges. 

Hot water basins are used to distribute water in crossflow towers. Here, water is pumped to an open pan over the wet deck fill. The bottom of the pan has holes through which water is distributed. Manufacturers will fit specially shaped plastic drip orifices into the holes to give the water an umbrella shape for more uniform distribution. Different size orifices are used for different flow rates. Ideally, the basin will be almost full at maximum flow. This way, sufficient depth is retained for good water distribution as turn down occurs. The turn down ratio can be extended by the addition of hot water basin weirs- a pattern of baffles perhaps 2 

System designers often think dampers bloek airflow and are suitable to prevent baek drafts in idle towers. This is not the ease. Airfoil dampers simply hamper fan housing efficiency- they do not block airflow. Air Inlet Screens are always part of blow through, counterflow towers to protect people from rotating equipment. Some designs can be a hazard when accessible from the underside and require the specifier to call out additional screening. They can be a worthwhile accessory when there are nearby trees even when not required for safety reasons. Air inlet screens should be eliminated on towers utilizing inlet ductwork. Inlet ductwork may also make it necessary to block extraneous air entry such as from the underside when towers are elevated. 

An engineer has a wide choiee of materials of eonstruetion for eorrosion control. There are three broad categories of materials, used either individually or in combination with each other metals, polymers, and ceramics. This chapter describes the differences between them and explains the phenomenology of applications of polymer-based materials. It also places fluoropolymer materials in their appropriate contexts. Polymer-based materials are also known as polymeries, polymeric materials, or simply plastics, which is often not accurate and can lead to confusion. 

If metal is chosen as the material of construction, the next choice is whether to make the construction bolted or welded. The primary factors to consider here are ease of fabrication, transportation and installation. Generally, a welded structure is best if it is of a size that can be shop fabricated and then lifted into place with a crane. For larger vessels that must be field welded, bolted construction is generally less expensive than welded, although it is usually not as robust because stress concentrations of bolted joints tend to weaken the structure, and there is the possibility of leakage whenever gaskets are used. 

Sometimes liners or coatings are chosen to provide good abrasive wear or impact resistance, and other times chemical resistance is a factor. Whatever liner or coating is chosen, it is important to consider the ability to repair and/or replace it. This usually has to be done in the field unless the vessel is quite small and can be taken out of service for several days or longer. 

Attachment of a liner must be considered in terms of both being strong enough to hold the liner in place and also not creating flow problems. The latter are due primarily to protrusions or joints that in most cases are detrimental to achieving mass flow. As to the 

Before a liner or coating is selected for a given application, it is important to test it with the actual bulk solid to be stored in the bin. Not only should flow tests be run to measure wall friction, but abrasive wear tests in order to estimate the wear life of the liner and changes in wall friction with wear should also be performed. 

The thickness of some liners can affect their frictional properties. For example, 2B finish is quite different in sheet thickness material as opposed to plate thickness. 

Plant safety depends on proper selection of materials for process piping and equipment. Misapplication of a material or poor design of components can cause such problems as  

Problems can arise from the mismatch of different matericils that would not fail had they not been joined together. Failure is often caused by galvanic corrosion, which is discussed in Section 3.2. 

Familiarity with the mechanical properties of materials is essential to their proper selection. Some important properties and their impact on process safety cire  

FIGURE 1.7 Comparison of the embodied energy (J/kg) and COj footprint for different materials. Source Reprinted with permission from Ghenai (2012). 

TABLE 1.1 Approximate Global Use of Selected Builfling Materials (2011 Data) 

Region Cement Roundwood Steel Plastic Aluminum 

The table is based on data from Materials and the Environment (wwwTorestinfo.oig) 

This chapter covers the selection of materials of construction for process equipment and piping. 

A detailed discussion of the theoretical aspects of corrosion is not given in this chapter, as this subject is covered comprehensively in several books Revie (2002), Fontana (1986), Dillon (1986) and Schweitzer (1989). 

Corrosion and corrosion prevention are also the subject of one of the design guides published by the Design Council, Ross (1977). 

Amine systems are extremely corrosive due to the acid-gas concentrations and the high temperatures. It is important that all carbon steel expo.sed to the amine be stress-relieved after the completion of welding on the particular piece. A system fabricated from stress-relieved carbon steel for DEA solutions, as recommended, will not suffer excessive corrosion. For MEA systems, corrosion-resistant metals (304 SS) should be used in the following areas  

Any part of the reboiler tube bundle that may be exposed to the vapor phase 

Pressure-reduction valve and pipe leading to the flash tank 

Pipe from the rich/lean exchange to the stripper inlet 

Pif iblem Design an Iron-Sponge Unit Solution  

For reasons described in the previous chapter, the discussions emphasize sieve and valve trays and exclude considerations unique to bubble-cap trays. Those unique considerations are detailed elsewhere (48, 86, 257). Nevertheless, several of the considerations discussed here also apply to several other tray t5q es, including bubble-cap trays. 

The main factors affecting the choice of construction materials of tray parts are  

Various materials are available as with all process equipment, ranging from carbon steel coated with rubber, Halar or Kynar, to stainless steel 304, 316 and higher grades, or more expensive alloys such as titanium, Hastelloy C-22, C276, or C4. These grades of Hastelloy will, however, double the capital outlays. 

Coatings should be avoided if possible as product A can diffuse into the surface and potentially reverse its path. It therefore has the potential to contaminate product B. Being permeable, they are also subject to peeling. Coatings can be used most effectively on stationary parts dedicated to liquid use that are, therefore, not exposed to maintenance tools, etc. 

The bowl in a modern decanter is a cylindrical tube with a flange at either end, on which are bolted at one end the liquid discharge bowl hub. and. on the other end. the cake discharge hub, or the beach followed by the cake discharge hub. The first cylindrical bowls used a filler piece in the end of the bowl to form the beach. On modern bowls, particularly the larger ones, the beach is bolted to a flange at one end of the cylindrical section, although with some overlap to provide mechanical location. 

The thickness of the bowl wall is dictated by the material of construction used, the maximum speed at which the bowl will be rotated, and the maximum weight of process material, feed, centrate or cake, likely to be held in the bowl. Thus the density of the process materials in use can have a major effect on the safe working speed of the bowl. 

The inside surface of the bowl can be plain machined. However, some effort is often made to encourage cake to stick to the bowl, to aid scrolling instead of slipping round with the conveyor. The means of doing this could be by knurling the inside of the bowl for instance. This can wear smooth relatively quickly. More often longitudinal ribs are welded, or a liner with similar ribs is fitted (see Section 2.2.4.3). 

The isomerization processes created unusual corrosion problems. Aluminum chloride-bearing catalyst proved to be extremely corrosive to steel and other common structural metals. Corrosion resulted in leaks in the reactor, connecting piping, and heat exchangers downstream from the reactor and in failure of block and control valves to function properly. The amount of corrosion depended on the type of aluminum chloride catalyst used and varied from point to point in a plant. In cases where corrosion was severe, Hastelloy B was found to be the only satisfactory resistant metal. 

The vapor-phase processes gave the least trouble (3). All maj or equipment in vapor-phase plants was made of carbon steel. Alloys were used only in such applications as trim on pumps and valves. 

The most serious corrosion problem arose in those processes using aluminum chloride complex as the catalyst (10). Of the many factors that tended to increase corrosion, the most important were turbulence, high concentrations of hydrogen chloride, and high concentrations of free aluminum chloride. Besides welding strains, high temperature also increases corrosion, and galvanic action apparently contributes where nickel or carbon steel is welded to Hastelloy B. 

Carbon steel corrodes 1 to 20 in. per year, the rate depending on the 

Catalyst lines between the reactor and the stripper had to be lined with Hastelloy B, and Hastelloy B valves had to be used. All nozzles in the reactor were similarly protected. Double extra-heavy 4-in. carbon-steel pipes were used in the reactor after cooler and replaced periodically. 

The most common material of construction is PFA Teflon . This high-purity material has become the material of choice due to its universal chemical resistance, nonstick surface properties, availability and compatibility of parts, and general historical and emotional acceptance. Other materials, such as polyethylene and polypropylene, are becoming more widely 

Equipment is varied in cleanrooms. It is impractical to try to highlight even the most common. Each piece of equipment needs to be specifically reviewed for generic hazards. This would involve the materials of construction being handled, electrical hazard and interconnections. 

The equipment should meet the criteria outlined in the materials electric code NFPA 70. Faulty electrics would be an unwanted ignition source. There have been occasions where operators were so against shutting down processes that they would modify the circuit breakers to a point where they would not deactivate the equipment even under the most hazardous conditions. De-energizing process equipment could fully destroy a multimillion dollar machine. Many of these machines could take years to replace. If all product needs to pass through this equipment, operations could cease until this equipment can finally be replaced. 

When reviewing equipment or machinery, it is necessary to consider its sequence of operation. When de-energized, the equipment should be in a safe condition. Before installed, a determination needs to be made on whether emergency power for operations or ventilations are necessary to prevent the hazardous condition. 

The chemicals used in cleanrooms might require special materials be used in construction. Whenever possible, noncombustible materials should be used. Only materials that come in direct contact with corrosive chemicals should be made of plastic. In the past, we have seen work stations handling flammable liquids constructed of polypropylene with stainless steel liners. The flammable liquids do not adversely affect the stainless steel, so they should be built entirely of this material. The Factory Mutual protocol for 

First stage suction piping and vessels can be constructed from carbon steel since it is the same design pressure and conditions as amine regeneration reflux vessel. All other downstream piping, vessels, coolers, and equipment should be constructed from stainless steel. 

Ring joint flanges seem to provide better seals than raised face flanges but getting valves and flanges apart can be difficult. 

In addition, the use of stainless steel for valves, thermowells, instrument lines, manifolds, etc. is recommended. The cooler headers, bundles, tubes, connections etc., should also be constructed from stainless steel. 

Corrosion resistance at conditions against chemicals handled MOC should not be adversely affected dming fabrication, cutting/welding High-impact resistance, especially for vessels in low temperatures Pressure vessels should be fabricated from standard-sized sheets available in market as virgin material. They should not be fabricated from recovered material (used for some other vessels earlier or obtained from ship-breaking yards) Purchaser should specify MOC for reactants and products under maximum pressure and temperature 

MOC Ordinary mild steel (e.g. 1.S.2062 or its international equivalent) should not be allowed. Certification for MOC mnst be obtained. Samples of MOC must be tested in approved laboratories. 

Carbon steel IS 2002 Grade A, ASTM A 560, SA-516, A-179 Carbon-manganese steel Carbon-molybdennm steel Chromium-molybdenum steel Chromium-molybdenum-vanadium steel Chromium-nickel stainless steel Duplex steel, super duplex steel Non-ferrous alloys of Ni, Cu, Al, Ti 

Stainless steel (18-25% Cr 8-20% Ni 0.05-0.2% C) corrosive conditions, up to 650 °C. Also, 0.03 % low carbon stainless steel Clad steel (carbon steel with cladding of stainless steel) 

MOC that can be used after test of corrosion resistance 

Acid flow rates also have to be kept at carefully prescribed velocities to prevent excessive corrosion. 

Alloys currently used in heat-from-acid energy recovery systems are material 1.4575 Superferrite or Sandvik HT 9067 (Louie, 2008) and ZeCor 310M alloy (Viergutz, 2009). 

Outotec also builds a sensible heat-from-acid recovery system. It uses a venturi absorber in place of Fig. 24.8 s bottom-packed bed (Gehrke and Kemmerich, 2010 Outotec, 2008). It has not been as widely adopted as the Fig. 24.8 HRS. 

H2S04( ) is made by the reaction of SO3 with the H20(f) in strong sulfuric acid. 

Heat is released by the reaction, so that H2SO4 making s output sulfuric acid is 25 K warmer than its input acid. 

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The choice of reactor temperature depends on many factors. Generally, the higher the rate of reaction, the smaller the reactor volume. Practical upper limits are set by safety considerations, materials-of-construction limitations, or maximum operating temperature for the catalyst. Whether the reaction system involves single or multiple reactions, and whether the reactions are reversible, also affects the choice of reactor temperature, as we shall now discuss. 

If Ail increases faster than k, operate at high temperature (but beware of safety and materials-of-construction constraints). 

The reactor products are so hot or corrosive that if passed directly to a heat exchanger, special materials-of-construction or an expensive mechanical design would be required. 

Raw materials efficiency. In choosing the reactor, the overriding consideration is usually raw materials efficiency (bearing in mind materials of construction, safety, etc.). Raw material costs are usually the most important costs in the whole process. Also, any inefficiency in raw materials use is likely to create waste streams that become an environmental problem. The reactor creates inefficiency in the use of raw materials in the following ways ... 

Reactors in the overall process. It should be emphasized that many considerations other than those represented in Figs. 2.9, 2.10, and 2.11 also influence the decision on the choice of reactor. Safety considerations, operating pressure, materials of construction, etc. have a considerable effect on the outcome. 

Corrosion problems often dictate that a particularly corrosive component be removed early to minimize the use of expensive materials of construction. 

If the problem is dominated by equipment with a single specification (i.e., a single material of construction, equipment type, and pressure rating), then the capital cost target can be calculated from Eq. (7.21) with the appropriate cost coefficients. However, if there is a mix of specifications, such as different streams requiring different materials of construction, then the approach must be modified. 

Thus the weighted network area AJ itwork is 9546 m. Now calculate the network capital cost for mixed materials of construction by using AI t ork... 

Hall, S. G., Ahmad, S., and Smith, R., Capital Cost Target for Heat Exchanger Networks Comprising Mixed Materials of Construction, Pressure Ratings and Exchanger Types, Computers Chem. Eng., 14 319, 1990. 

When synthesizing a fiowsheet, the designer should consider carefully the problems associated with operation under extreme conditions. Attenuation will result in a safer plant, providing the attenuation does not increase the inventory of hazardous materials. If the inventory does not increase, then attenuation not only will make the process safer but also will make it cheaper, since cheaper materials of construction and thinner vessel walls can be used and it is not necessary to add on so much protective equipment. 

Reaction temperature. For endothermic reactions. Fig. 2.9c shows that the temperature should be set as high as possible consistent with materials-of-construction limitations, catalyst life, and safety. For exothermic reactions, the ideal temperature is continuously decreasing as conversion increases (see Fig. 2.9c). 

Factors should be included to allow for variations in design pressure and material of construction ... 

Equation (F.l) shows that each stream makes a contribution to total heat transfer area defined only by its duty, position in the composite curves, and its h value. This contribution to area means also a contribution to capital cost. If, for example, a corrosive stream requires special materials of construction, it will have a greater contribution to capital cost than a similar noncorrosive stream. If only one cost law is to be used for a network comprising mixed materials of construction, the area contribution of streams requiring special materials must somehow increase. One way this may be done is by weighting the heat transfer coefficients to reflect the cost of the material the stream requires. 

In order to maintain high energy efficiency and ensure a long service life of the materials of construction in the combustion chamber, turbine and jet nozzle, a clean burning flame must be obtained that minimizes the heat exchange by radiation and limits the formation of carbon deposits. These qualities are determined by two procedures that determine respectively the smoke point and the luminometer index. 

The non-hydrocarbon components of crude oil may be small in volume percent, typically less than 1 %, but their influence on the product quality and the processing requirements can be considerable. It is therefore important to identify the presence of these components as early as possible, and certainly before the field development planning stage, to enable the appropriate choice of processing facilities and materials of construction to be made. 

While the principal value of the book is for the professional chemist or student of chemistry, it should also be of value to many people not especially educated as chemists. Workers in the natural sciences—physicists, mineralogists, biologists, pharmacists, engineers, patent attorneys, and librarians—are often called upon to solve problems dealing with the properties of chemical products or materials of construction. Eor such needs this compilation supplies helpful information and will serve not only as an economical substitute for the costly accumulation of a large library of monographs on specialized subjects, but also as a means of conserving the time required to search for... 

Materials of Construction Suitable materials of constmction are steel, stainless steel, and aluminum 3003. Galvanized steel should not be used. Plastic tanks and lines are not recommended. 

Table 2. Stability of Sulfur Hexafluoride in Various Materials of Construction ...

Materials of Construction. In choosing the proper materials of constmction for storing and using hydrazine, it is necessary to consider both the effects of the material on the stabiUty and quaUty of the hydrazine as well as the effect of the hydrazine on the material of constmction. Hydrazine is thermally stable, storable for years without adverse effects either to the product or the storage container provided the recommended materials are used, all systems are clean, and an inert gas, ie, nitrogen, is maintained over the system at all times. Table 10 is a brief listing of materials compatibiUty (125). 

Materials of Construction. High sihcon iron. Stellite 6, HasteUoy C, and stainless steels types 304, 309, 316, and 317, have low corrosion... 

R. D. Cooks, Materials of Construction for Nitric Mcid, Process Industries Corrosion, National Association of Corrosion Engineers, 1986, pp. 259—263. 

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