Process technologies

The main route to ACRN is the one-step propylene ammoxidation process. In this process propylene, ammonia and air reacted in a fluidized bed reactor to produce ACRN with acetonitrile and hydrogen cyanide as by-products. New technology based on propane ammoxidation has been developed by BP, Mitsubishi (in conjunction with BOC) and Asahi Kasei with claims of a 30% production cost advantage over the propylene route276. However no plans have been announced to build a propane-based plant as of first quarter 2004 297. 

Demand in the United States was flat in 2000 and 2001 at about 1.68 billion pounds per year. Demand is expected to grow to 1.8 billion pounds per year by 2005277. 

Worldwide demand is expected to grow at 2% to 3% per year from 2002 through 2008 with higher growth in China. New capacity that came onstream in 2000 had not been fully absorbed by 2002. Therefore more rationalization was expected with possible plant closures of uncompetitive plants in Europe and Asia276. Global ACRN capacity was 5.9 million tonnes per year in 2002. World ACRN demand is shown in Table 22.2 and shows that capacity utilization is 80% to 85%278. 

Region Capacity (kt/vr) Output (kt) Consumption (kt) Rate (%) Exports (kt) 

China s ACRN capacity is growing rapidly. It has grown from 422,000 tonnes per year in 2001, to 487,000 tonnes per year in 2002, to 571,000 tonnes per year in 2003. And it is expected to reach 900,000 tonnes per year by 2005 -an increase of over 115% in five years. However Chinese demand is expected to reach 1,100,000 tonnes per year by 2005. Therefore imports of at least 200 tonnes per year will still be needed292,293. 

Gregory (Ref. G6) is a very comprehensive source specific to the industrial and commercial applications of chemicals. It includes a three page list of the uses of nitric acid. Similar information is presented for many other chemicals in this book. The one fault of this source is that it is 50 years old In that period many process technologies have changed and the applications list, whilst very comprehensive, tends to be dated. 

Reference G7 provides an excellent coverage of the materials of construction used in nitric acid manufacture and storage. Reference G8 is a Firth-Vickers catalogue, used to obtain the physical properties and corrosion resistance data for stainless steel 304L. 

The final reference in this category is the Australian Government Gazette (Ref. G9) which includes information regarding industrial effluent limits, as demanded by the Environmental Protection Authority (in Australia). These data are quoted in the Environmental Impact Analysis (Section 5.4.7). 

This category contains those references specifying process innovation, operating conditions, utility requirements, catalyst information, etc. All information relates directly to the process requirements. 

Harvin, Leray and Roudier (Ref. PTI ) and Chilton (Ref. PT2) were the two main references used to determine the process selection for this project. Reference PTI contains an objective comparison between the dual and single-pressure processes. It compares them on nearly all aspects, including capital and operating costs, process 

The commercial development of PPO started in the 1960s, and the first priority was to find an efficient and low-cost procedure to produce the monomer, namely, DMP. Thus, DMP is obtained from cyclohexanone hence, the reaction of cyclohexanone with formaldehyde at 350 °C in the presence of tricalcium phosphate generates DMP with a reasonable yield [33]. DMP can also be produced by the reaction of phenol with methanol at 350 °C, with magnesium oxide as catalyst [34]. The latter method rendered the manufacture of the polymer economically attractive accordingly, from 1964, its commerciaUzation accelerated. 

As already mentioned earher (see Section 7.1.1), because of its high glass-transition temperature, that is, T = 208°C, PPO has to be melt-processed at elevated temperatures. As a result, degradation of the polymer may occur at such temperatures (particularly through oxidation reactions at the methyl substituents), furthermore, upon cooling from the liquid to the rubber state, two unwanted events can take place (i) the polymer crystallizes and (ii) the molecular motions are frozen and the rubbery polymer turns to a glass. As a consequence, the material becomes brittle and cannot be used for practical applications. Fortunately, PPO exhibits unusual and remarkable blending properties [36]. 

A limitation is, however, encountered with Noryl resins indeed, because PS is a very brittle material, their impact strength decreases when the percentage of PS is raised [37]. To circumvent this problem, rubbers are added to Noryl resins to increase the toughness [39]. Thanks to the exceptional blending properties of PPO , numerous mixed materials have been developed, for instance, with diallyl phthalates, polysulfone, acrylates, coumarone-indene, or polyvinyl chloride (PVC) [39]. It has also been shown that PPO could be blended with styrene-butadiene block copolymers, hence allowing to expand the temperature of use of the resulting materials [40]. Accordingly, the combination of various 

PPO -PS levels with other additives provides a myriad of resins that cover a very wide range of physical and thermomechanical properties. Their general characteristics include high heat resistance, excellent electrical properties over a wide range of temperatures and frequencies, low density, high hydrolytic stability, chemical resistance to most acids, dimensional stability, low mold shrinkage, and very low creep behavior at elevated temperatures. 

Since the discovery of PPO by Allan S. Hay ofthe General Electric Company in the 1960s [3,41], over 1500 patents have been issued in the field of oxidative coupling polymerization, and the total sales worldwide of engineering plastics based on PPO to date represent about US 1 billion per year. In fact, Noryl -modrfied PPO resins have become the world s most successful and best-known polymer blends and alloys. 

The fabrication technique of redispersible polymer powder-modified mortar and concrete is about the same as that for latex-modified mortar and concrete. The materials and mix prc rtions used in this nnodified mortar and concrete are the same as those used in the latex-modified systems except that the addition of the redispersible polymer powders is involved. At present, commercially available redispersible polymer powders as cement modifiers are classified in Fig. 5.2. Table 5.2 gives the properties of typical redispersible polymer powders. The rediqretsible polymer powders are usually free-flowing powders, and have ash contents of 5 to 15%, whidi primarily come from the anti-blockirig aids. When the polymer powders are placed in water under agitation, they redtsperse or re-emulsify easily, and provide the polymer latexes with polymer particle sizes of 1 to 10 pm. 

Appearance White Powder White Powder White Powder White Powder 

American Concrete Institute, reprinted with permission.)  

Similar to latex-modified systems, the properties of redispersible polymer powder-modified systems are improved in comparison with ordinary cement mortar and concrete, and these depend on the nature of polymer and polymer-cement ratio. Figs. 5.3 to 5.5i l represent the strengths, adhesion to cement mortar, water resistance, and water absorption of the redispersible polymer powder-modified mortars. The properties are improved with an increase in the polymer-cement ratio. This tendency is very similar to that of the latex-modified systems. In general, the redispersible polymer powder-modified mortars are inferior to SBR-modified mortar (control) in certain properties. VAA eoVa powder-modified mortars show tetter properties than EVA powder-modified mortars as seen in Fig. 5.5. The film formation characteristics of recent redispersible polymer powders for cement modifiers are improved, and continuous polymer films can be found in the redispersible polymer powder-modified systems as seen in Fig. 5.6. This contributes greatly to improvements in their properties. 

l It l reported that repair mortars using redispersible polymer powders for concrete structures show high resistance to the diffusion of chloride ions, oxygen and carbon dioxide, and also low shrinkage. 

The basic steps in COM preparation are (1) fine grinding of the coal, (2) mixing the pulverized coal with oil, and (3) stabilizing the mixture by addition of various chemical additives. An additional step of beneflciating the coal to remove sulfur and ash is also typically required. Beneficiation 

Major emphasis on eastern, medium- to high-volatile bituminous coal Typically 200 mesh (74 pm or finer) bimodal distributions are under study for CWMs Aiming for 15,000 Btu/lb, 0.9% sulfur, 4.0% ash 

Additives minimize viscosity, increase solids loading capacity, and enhance mixture stability CLMs are highly viscous, non-Newtonian fluids and must be stable with respect to sedimentation and subsidence Fuel parameters abrasiveness (nozzle and pump wear) atomizabiUty carbon conversion flame stability 

Prt jrietary preparation processes involving additives, grinding, and mixing 

Burner modification boiler modifications to prevent fouling, reduce derating, and collect ash 

IRgwre 5. C nnK rcialiy av il ye tSispc siWe polymer povwteis for eeawnt ntodifieits. 

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Rousseau, R. W., Handbook of Separation Process Technology, Wiley, New York, 1987. 

There can be an element of maintenance costs that is fixed and an element which is variable. Fixed maintenance costs cover routine maintenance such as regular maintenance on safety valves which must be carried out irrespective of the rate of production. There also can be an element of maintenance costs which is variable. This arises from the fact that certain items of equipment can need more maintenance as the production rate increases. Also, royalties which cover the cost of purchasing another company s process technology may have different bases. Royalties may be a variable cost, since they can sometimes be paid in proportion to the rate of production. Alternatively, the royalty might be a single-sum payment at the beginning of the project. In this case, the single-sum payment will become part of the project s capital investment. As such, it will be included in the annual capital repayment, and this becomes part of the fixed cost. 

A yield of about 95% of theoretical is achieved using this process (1.09 units of isopropyl alcohol per unit of acetone produced). Depending on the process technology and catalyst system, such coproducts as methyl isobutyl ketone and diisobutyl ketone can be produced with acetone (30). 

These processes use expensive C2 hydrocarbons as feedstocks and thus have higher overall acrylonitrile production costs compared to the propylene-based process technology. The last commercial plants using these process technologies were shut down by 1970. 

The propylene-based process developed by Sohio was able to displace all other commercial production technologies because of its substantial advantage in overall production costs, primarily due to lower raw material costs. Raw material costs less by-product credits account for about 60% of the total acrylonitrile production cost for a world-scale plant. The process has remained economically advantaged over other process technologies since the first commercial plant in 1960 because of the higher acrylonitrile yields resulting from the introduction of improved commercial catalysts. Reported per-pass conversions of propylene to acrylonitrile have increased from about 65% to over 80% (28,68—70). 

Process Technology. In a typical oxo process, primary alcohols are produced from monoolefins in two steps. In the first stage, the olefin, hydrogen, and carbon monoxide [630-08-0] react in the presence of a cobalt or rhodium catalyst to form aldehydes, which are hydrogenated in the second step to the alcohols. 

Staple is produced by cutting a crimped tow into short lengths (usually 4—5 cm) resembling short, natural fibers. Acetate and triacetate staple are shipped in 180—366 kg bales, but production is quite limited. Conventional staple-processing technology appHed to natural fibers is used to process acetate and triacetate staple into spun yam. 

Particular food products have weU-developed technologies associated with their preparation, processing, and packaging. Detailed discussions of processing technologies can be found in the general references. 

V. D. Allred, ed., 0/7Shale Processing Technology, Center for Professional Advancement, East Bmnswick, N.J., 1982. 

J. E. Duddy, S. B. Panvelker, and G. A. Popper, "Commercial Economics of HRI Coal/Oil Co-Processing Technology," paper presented at 1990 SummerAIChE National Meeting, San Diego, Ca., 1990. 

E. Doetsch and H. DoHwa, "Economical and Process Technology Aspects of Cast Iron Melting," Electrowarmeint. 37(B3), B157 (1979), contains an economic comparison fuel-fired and electric iron foundry melting furnaces. 

Diesel Fuel. Eederal diesel specifications were changed to specify a maximum of 0.05% sulfur and a minimum cetane index of 40 or a maximum aromatics content of 35 vol % for on-road diesel. Eor off-road diesel, higher sulfur is allowed. CARB specifications require 0.05% sulfur on or off road and 10% aromatics maximum or passage of a qualification test. Process technologies chosen to meet these specifications include hydrotreating, hydrocracking, and aromatics saturation. 

This electrolytic process technology is no longer used because of the extensive and continuous electrolyte purification needs, the high capital and power requirements, and economic inabiHty to compete with large-scale anthrahydroquinone autoxidation processes. 

Russian Process Technology. Magnesium production ia the former Soviet Union is apparently done via molten chloride electrolysis (29,30). The basic process uses camaOite [1318-27-0], MgCl2 KCl 6H20, either from natural deposits or as a by-product of processiag natural salt deposits, as its... 

Process Technology Evolution. Maleic anhydride was first commercially produced in the early 1930s by the vapor-phase oxidation of benzene [71-43-2]. The use of benzene as a feedstock for the production of maleic anhydride was dominant in the world market well into the 1980s. Several processes have been used for the production of maleic anhydride from benzene with the most common one from Scientific Design. Small amounts of maleic acid are produced as a by-product in production of phthaHc anhydride [85-44-9]. This can be converted to either maleic anhydride or fumaric acid. Benzene, although easily oxidized to maleic anhydride with high selectivity, is an inherently inefficient feedstock since two excess carbon atoms are present in the raw material. Various compounds have been evaluated as raw material substitutes for benzene in production of maleic anhydride. Fixed- and fluid-bed processes for production of maleic anhydride from the butenes present in mixed streams have been practiced commercially. None of these... 

Butane-Based Fixed-Bed Process Technology. Maleic anhydride is produced by reaction of butane with oxygen using the vanadium phosphoms oxide heterogeneous catalyst discussed earlier. The butane oxidation reaction to produce maleic anhydride is very exothermic. The main reaction by-products are carbon monoxide and carbon dioxide. Stoichiometries and heats of reaction for the three principal reactions are as follows ... 

Butane-Based Transport-Bed Process Technology. Du Pont aimounced the commercialization of a moving-bed recycle-based technology for the oxidation of butane to maleic anhydride (109,149). Athough maleic anhydride is produced in the reaction section of the process and could be recovered, it is not a direct product of the process. Maleic anhydride is recovered as aqueous maleic acid for hydrogenation to tetrahydrofuran [109-99-9] (THF). 

An important future use for maleic anhydride is beUeved to be the production of products in the 1,4-butanediol—y-butyrolactone—tetrahydrofuran family. Davy Process Technology has commercialized a process (93) for producing 1,4-butanediol from maleic anhydride. This technology can be used to produce the product mix of the three molecules as needed by the producer. Another significant effort in this area is the tetrahydrofuran plant under constmction in Spain by Du Pont in which butane is oxidized and recovered as maleic acid and the maleic acid is then reduced to tetrahydrofuran (109). 

The minerals processing industry has made contributions to all areas of technology, both in terms of products and processing. Technologies developed in the mineral industry are used extensively in the chemicals industry as well as in municipal and industrial waste treatment and recycling industry, eg, scrap recycling, processing of domestic refuse, automobiles, electronic scrap, battery scrap, and decontamination of soils. 

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