For ammonia converters

Ammonia Casale SA Ammonia Natural gas (NG) Process produces anhydrous ammonia from natural gas by applying Casale s high-efficiency secondary reformer design, axial-radial technology for shift conversion, ejector ammonia wash system, axial-radical technology for ammonia converter and advanced waste-heat boiler design in the synthesis loop. 5 2010... 

As mentioned above, Haldor Topsoe A/S, KBR, and Uhde GmbH share the major part of the market for new ammonia synthesis technology. For plant retrofits also others are active and especially for ammonia converter revamps, Ammonia Casale offer their ammonia synthesis technology. The main feature of the Casale technology is the so-called axial-radial flow synthesis converter (55, 56), and (57). 

Benefit of energy saving (reduce pressure). According to the balance of mass and energy for ammonia converter ... 

Reforming is completed in a secondary reformer, where air is added both to elevate the temperature by partial combustion of the gas stream and to produce the 3 1 H2 N2 ratio downstream of the shift converter as is required for ammonia synthesis. The water gas shift converter then produces more H2 from carbon monoxide and water. A low temperature shift process using a zinc—chromium—copper oxide catalyst has replaced the earlier iron oxide-catalyzed high temperature system. The majority of the CO2 is then removed. 

These gases are then fed to the water gas converter as in the steam-reforming process, after which they are compressed to ca 20.3 MPa (ca 200 atm) for processing in the catalytic ammonia converter. 

Fig. 1. MoUier diagram for ammonia. Numbers on dashed lines represent specific volume values ia m /kg. To convert from kPa to psi, multiply by 0.145.

Hydroisoquinolines. In addition to the ring-closure reactions previously cited, a variety of reduction methods are available for the synthesis of these important ring systems. Lithium aluminum hydride or sodium in Hquid ammonia convert isoquinoline to 1,2-dihydroisoquinoline (175). Further reduction of this intermediate or reduction of isoquinoline with tin and hydrochloric acid, sodium and alcohol, or catalyticaHy using platinum produces... 

After removal of the unreacted ammonia and recovery of hydrogen cyanide, the waste gas is essentially all hydrogen suitable for other chemical use. The advantages of the BMA process are the high ammonia and natural gas yields and the usehil hydrogen waste gas, but the high investment and maintenance for the converter is a decided disadvantage. 

These enable temperature control with built-in exchangers between the beds or with pumparound exchangers. Converters for ammonia, 80.3, cumene, and other processes may employ as many as five or six beds in series. The Sohio process for vapor-phase oxidation of propylene to acrylic acid uses hvo beds of bismuth molybdate at 20 to 30 atm (294 to 441 psi) and 290 to 400°C (554 to 752°F). Oxidation of ethylene to ethylene oxide also is done in two stages with supported... 

As a constituent of synthesis gas, hydrogen is a precursor for ammonia, methanol, Oxo alcohols, and hydrocarbons from Fischer Tropsch processes. The direct use of hydrogen as a clean fuel for automobiles and buses is currently being evaluated compared to fuel cell vehicles that use hydrocarbon fuels which are converted through on-board reformers to a hydrogen-rich gas. Direct use of H2 provides greater efficiency and environmental benefits. ... 

Cations of these metals invariably exist in aqueous solution as complex ions. Consider, for example, the zinc(II) cation. In a water solution ofZn(N03)2, the Zn(H20)42+ ion is present. Treatment with ammonia converts this to Zn(NH3)42+ addition of sodium hydroxide forms Zn(OH)42-. 

By far the most important use of the platinum metals is for catalysis. The largest single use is in automobile catalytic converters. Platinum is the principal catalyst, but catalytic converters also contain rhodium and palladium. These elements also catalyze a wide variety of reactions in the chemical and petroleum industry. For example, platinum metal is the catalyst for ammonia oxidation in the production of nitric acid, as described in Pt gauze, 1200 K... 

Oxygen-containing molecules cannot be tolerated in the ammonia synthesis, primarily because they form iron oxide that blocks the active surface. First the CO2 is removed, through a scrubber, by reaction with a strong base. The remaining CO (and CO2) is then removed by the methanation reaction, converting the CO into methane and water. Finally the water is removed by, for example, molecular sieves. Methane does not present problems because it interacts weakly with the catalyst surface. The gas mixture (Tab. 8.6) is compressed to the roughly 200 bar needed for ammonia synthesis and admitted to the reactor. 

Figure 40.6. Selectivity to A -containing products (full symbols, calculated with respect to n-hexane converted) and to N2 (open symbols, calculated with respect to ammonia converted) as a function of temperature for catalysts with composition Sn/V/Nb/Sb x/0.2/1/3. Symbols as in Figure 40.5.

Willason and Johnson [53] have described a modified flow-injection analysis procedure for ammonia in seawater. Ammonium ions in the sample were converted to ammonia which diffused across a hydrophobic membrane and reacted with an acid-based indicator. Change in light transmittance of the acceptor steam produced by the ammonia was measured by a light emitting diode photometer. The automated method had a detection limit of 0.05 xmol/l and a sampling rate of 60 or more measurement per hour. 

A methanator converts the last traces of carbon dioxide to methane, a less interfering contaminant in hydrogen used for ammonia manufacture. 

Kjaer (K9) gives a very comprehensive study of concentration and temperature profiles in fixed-bed catalytic reactors. Both theoretical and experimental work is reported for a phthallic anhydride reactor and various types of ammonia converters. Fair agreement was obtained, but due to the lack of sufficiently accurate thermodynamic and kinetic data, definite conclusions as to the suitability of the dispersed plug flow model could not be reached. However, the results seemed to indicate that the... 

Methanators are usually used in the ammonia production line to guard the catalyst of the ammonia converters from the ill effect of carbon monoxide and carbon dioxide. This section includes precise models for different types of methanators using the dusty gas model with reliable kinetic expression and the results are compared with those of the simplified models (A) and (B). 

Industrial fixed-bed catalytic reactors have a wide range of different configurations. The configuration of the reactor itself may give rise to multiplicity of the steady states when other sources alone are not sufficient to produce the phenomenon. Most well known is the case of catalytic reactors where the gas phase is in plug flow and all diffusional resistances are negligible, while the reaction is exothermic and is countercurrently cooled. One typical example for this is the TVA type ammonia converter [38-40]. 

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