Ammonia carriers

Ammonia, when released is a toxic gas with little flammability. It is imported by sea into the 14,(XX) tonnes capacity tank at Shell UK Oil where the refrigeration maintains the temperature below the boiling point of the gas (33° C). Three ways were identified whereby several hundred tonnes of liquid ammonia could be released into the river to vaporize and disperse. The worst accident would have an accompanying explosion or fire on an ammonia carrier berthed at the unloading jetty. Next in order of severity is a ship collision and spillage into the river near the unloading jetty. The consequences of a collision between ships occurring within the area but not near the jetty were also calculated. 

While the practical implementation of the SCR deNOx technology for vehicles relies on using an urea aqueous solution as ammonia carrier, NH3 being generated by decomposition and hydrolysis of urea, the present investigation has been focused on the reactivity of ammonia only it is believed in fact that decoupling urea decomposition from NH3-NOx reactions is quite helpful in effectively elucidating SCR chemistry and kinetics. 

The importance of such a source of hydrogen for ammonia production lies in the value of phosphoric acid, a plant food, as an ammonia carrier. A plant for the production of phosphorus according to this process is in operation at the cyanamide plant at Piesteritz, Germany. The phosphorus produced is shipped to the Badlsche Anilin und Soda Fabrik at Merseburg, where it is oxidized with steam to phosphoric acid and hydrogen. 

The advantage of ammonium phosphate over the sulphate salt for instance is in the fact that the add ammonia carrier is In itself a plant food. 

Reagent Dilution/Cairier Gas Requirements Diluted with water to 5-25% concentration. Air is the carrier gas. (Steam is no longer used.) Typically, 4 scfm of plant air per injector is currently used for atomization and for injector cooling. Not diluted with water. Air or steam at 1-2% of the flue gas flow rate is the carrier gas. This gas requirement is reduced by the amount of water vaporized if aqueous ammonia is vaporized. Not diluted with water. Carrier gas is air, flue gas, or possibly steam at about 2 psig. Ammonia/carrier gas volumetric ratio is a minimum of about 1 to 20 for anhydrous ammonia to keep the ammonia concentration in the air below the lower explosive limit. Lower concenuations may be used based on injection diffusion patterns, the ammonia vaporization heat requirement, minimum flow control ranges, and other factors. 

Deaminating enzymes occur in kidney cortex and, to a lesser extent, in liver. Vertebrate intestinal mucosa and cardiac muscle of pigeons and frogs have a slight and restricted capacity for deamination. Other vertebrate tissues (brain, retina, spleen, bone-marrow, pancreas, salivary gland and mammalian heart) appear to be incapable of deaminating amino acids. The ammonia released in deamination is either transformed locally in the liver into urea, or is transported to the liver by an ammonia carrier for conversion into mea. A small part of the renal ammonia escapes into the urine, and serves to regulate its H-ion concentration. 

Ammonia Carriers.— Although ammonia appears as an end-product of general deamination, it is too toxic and reactive a metabolite to remain in the tissues in a free form, and is taken up by appropriate carriers, such as glutamic acid, aspartic acid, adenylic acid and adenosine, or may be removed by an amino-pherase system. These, or other carriers, transport ammonia to the liver for detoxication by conversion to urea. 

Ammonia is usually transported for long distances by barge, pipeline, and rail, and for short distances by tmck Eactors that govern the type of carrier used in anhydrous ammonia transportation systems are distance, location of plant site in relation to consuming area, availabihty of transportation equipment, and relative cost of available carriers. Typical costs (83) of pipeline, barge, and rail modes for long distance transport are 0.0153, 0.0161, and 0.0215 per ton per kilometer, respectively, for distances of about 1600 km. Short distance tmck transportation costs (83) are much higher. Costs are typically 0.0365/(t km) for distances on the order of 160 km. 

Metal teUurides for semiconductors are made by direct melting, melting with excess teUurium and volatilizing the excess under reduced pressure, passing teUurium vapor in an inert gas carrier over a heated metal, and high temperature reduction of oxy compounds with hydrogen or ammonia. 

The hot ammonia used as carrier gas serves simultaneously as fluidising agent and inhibits deammonisation. 

One principal use of cyclohexanol has been in the manufacture of esters for use as plasticizers (qv), ie, cyclohexyl and dicyclohexyl phthalates. In the finishes industry, cyclohexanol is used as a solvent for lacquers, shellacs, and varnishes. Its low volatiUty helps to improve secondary flow and to prevent blushing. It also improves the miscibility of cellulose nitrate and resin solutions and helps maintain homogeneity during drying of lacquers. Reaction of cyclohexanol with ammonia produces cyclohexylamine [108-91-8], a corrosion inhibitor. Cyclohexanol is used as a stabilizer and homogenizer for soaps and synthetic detergent emulsions. It is used also by the textile industry as a dye solvent and kier-boiling assistant (see Dye carriers). 

Usually they are employed as porous pellets in a packed bed. Some exceptions are platinum for the oxidation of ammonia, which is in the form of several layers of fine-mesh wire gauze, and catalysts deposited on membranes. Pore surfaces can be several hundred mVg and pore diameters of the order of 100 A. The entire structure may be or catalytic material (silica or alumina, for instance, sometimes exert catalytic properties) or an active ingredient may be deposited on a porous refractory carrier as a thin film. In such cases the mass of expensive catalytic material, such as Pt or Pd, may be only a fraction of 1 percent. 

Selective Catalytic Reduction (SCR) SCE is a process to reduce NO, to nitrogen and water with ammonia in the presence of a catalyst between 540-840 F (282-449 C). Ammonia is usually injected at a 1 1 molar ratio with the NOx contaminants. Ammonia is used due to its tendency to react only with the contaminants and not with the oxygen in the gas stream. Ammonia is injected by means of compressed gas or steam carriers. Efficiencies near 90% have been reported with SCR. See Exxon Thermal DeNO. ... 

Many other cyclic and noncyclic organic carriers with remarkable ion selectivities have been used successfiilly as active hosts of various liquid membrane electrodes. These include the 14-crown-4-ether for lithium (30) 16-crown-5 derivatives for sodium bis-benzo-18-crown-6 ether for cesium the ionophore ETH 1001 [(R,R)-AA -bisd l-ethoxycarbonyl)undecyl-A,yVl-4,5-tctramcthyl-3,6-dioxaoctancdiamide] for calcium the natural macrocyclics nonactin and monensin for ammonia and sodium (31), respectively the ionophore ETH 1117 for magnesium calixarene derivatives for sodium (32) and macrocyclic thioethers for mercury and silver (33). 

A corrosion inhibitor with excellent film-forming and film-persistency characteristics is produced by first reacting Cig unsaturated fatty acids with maleic anhydride or fumaiic acid to produce the fatty acid Diels-Alder adduct or the fatty acid-ene reaction product [31]. This reaction product is further reacted in a condensation or hydrolyzation reaction with a polyalcohol to form an acid-anhydride ester corrosion inhibitor. The ester may be reacted with amines, metal hydroxides, metal oxides, ammonia, and combinations thereof to neutralize the ester. Surfactants may be added to tailor the inhibitor formulation to meet the specific needs of the user, that is, the corrosion inhibitor may be formulated to produce an oil-soluble, highly water-dispersible corrosion inhibitor or an oil-dispersible, water-soluble corrosion inhibitor. Suitable carrier solvents may be used as needed to disperse the corrosion inhibitor formulation. 

Thus, the technique can become counterproductive. A typical arrangement for selective non-catalytic reduction is shown in Figure 25.30. Aqueous ammonia is vaporized and mixed with a carrier gas (low-pressure steam or compressed air) and injected into nozzles located in the combustion device for optimum temperature and residence time10. NO, reduction of up to 75% can be achieved. However, slippage of excess ammonia must be controlled carefully. 

---