Storage ammonia

Even when all of the ammonia is used at the plant site where it is produced, it is common practice to have facilities for storage of 3 to 15 days production so that interruptions in operation of downstream facilities will not require intenruption of the ammonia plant operation, In an ammonia-urea complex, for example, when the urea plant must be shut down for repairs, the ammonia plant can continue to operate with the ammonia going to storage. 

Following are two preferred methods for storing liquid ammonia. One is the pressure storage at ambient temperature in spherical or cylindrical vessels up to a capacity of about 1,500 tonnes. The other method is atmospheric pressure storage at -33 C in insulated cylindrical tanks up to about 50,000-tonne capacity. Additionally, reduced pressure storage at about 0°C in an insulated, usuaQy spherical vessel for a capacity up to about 2,500 tonnes per vessel is also used [4]. The suitability of storage depends on the required temperature and flow quantity of ammonia into and out of the storage. 

The pressurized tanks are suitable for storing small quantities of ammonia from pipeline systems, tank cars, and barges carrying pressurized ammonia. Usually, lindrical vessels are designed for 2-5 MPa. The larger 

The low-temperature storage tanks are best suited for the storage of ammonia from the synthesis loop at a low temperature and for the shipping terminals handling a large capacity. The tanks operate at atmospheric pressure, and they are well insulated to minimize the 

T-1 Double i rvtegr -ty storage tank P-2. P—3 Loading punps E-4 NH3 preheater 

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Fig. 38. Caustic purification system a, 50% caustic feed tank b, 50% caustic feed pumps c, caustic feed preheater d, amonia feed pumps e, ammonia feed preheater f, extractor g, trim heater h, ammonia subcooler i, stripper condenser j, anhydrous ammonia storage tank k, primary flash tank 1, evaporator reboiler m, evaporator n, caustic product transfer pumps o, purified caustic product cooler p, purified caustic storage tank q, ammonia stripper r, purified caustic transfer pumps t, overheads condenser u, evaporator v, evaporator vacuum pump w, aqueous storage ammonia tank x, ammonia scmbber y, scmbber condenser 2, ammonia recirculating pump aa, ammonia recycle pump. CW stands for chilled water.

The reactor effluent, containing 1—2% hydrazine, ammonia, sodium chloride, and water, is preheated and sent to the ammonia recovery system, which consists of two columns. In the first column, ammonia goes overhead under pressure and recycles to the anhydrous ammonia storage tank. In the second column, some water and final traces of ammonia are removed overhead. The bottoms from this column, consisting of water, sodium chloride, and hydrazine, are sent to an evaporating crystallizer where sodium chloride (and the slight excess of sodium hydroxide) is removed from the system as a soHd. Vapors from the crystallizer flow to the hydrate column where water is removed overhead. The bottom stream from this column is close to the hydrazine—water azeotrope composition. Standard materials of constmction may be used for handling chlorine, caustic, and sodium hypochlorite. For all surfaces in contact with hydrazine, however, the preferred material of constmction is 304 L stainless steel. 

Ammonia is corrosive to akoys of copper and zinc and these materials must not be used in ammonia service. Iron or steel should usuaky be the only metal in ammonia storage tanks, piping, and fittings. It is recommended that ammonia should contain at least 0.2% water to prevent steel stress corrosion. Mercury thermometers should be avoided. 

Fixed investment includes cooling tower, boiler feedwater treatment, raw water ammonia storage as minimum off-sites requirement. 

To reduce storage costs involved in such a cycHc consumption pattern, there has been substantial growth in the erection of large refrigerated anhydrous ammonia storage terminals at key points within large marketing areas. Terminal cost (84) is reported to add typically about 11.00/t. 

Determine whether a catastrophic failure of the ammonia storage tank could cause irreversible health impacts in a nearby neighborhood. 

Selective catalytic reduction (SCR) is cmrently the most developed and widely applied FGT technology. In the SCR process, ammonia is used as a reducing agent to convert NO, to nitrogen in the presence of a catalyst in a converter upstream of the air heater. The catalyst is usually a mixture of titanium dioxide, vanadium pentoxide, and hmgsten trioxide. SCR can remove 60-90% of NO, from flue gases. Unfortunately, the process is very expensive (US 40- 80/kilowatt), and the associated ammonia injection results in an ammonia slip stream in the exhaust. In addition, there are safety and environmental concerns associated with anhydrous ammonia storage. 

Particulate matter is the principal air pollutant emitted from ammonium sulfate plants. Most of the particulates are found in the gaseous exhaust of the dryers. Uncontrolled discharges of particulates may be of the order of 23 kg/t from rotary dryers and 109 kg/t from fluidized bed dryers. Ammonia storage tanks can release ammonia, and there may be fugitive losses of ammonia from process equipment. 

Gauges used for measuring the liquid level in vessels may be of semitransparent and even nontransparent materials. Figure 3.2 illustrates a simple level gauge on a steel vessel used for liquid ammonia storage. As shown, a narrow strip of insulation is taken away from the vessel s shell to expose the bare metal. Consequently, the heat transfer coefficient from the... 

A rrobabftistic Safety Analysis of an Ammonia Storage Plant... 

The following PSA of a refrigerated ammonia storage facility is from Papazoglou (1990a, 1990b). An obje ve of the work was to test PSA as it had been applied to nuclear power... 

Piping between the ship and the tank during loading phase (3.8E-3/y),. A.inmonia storage tank from ammonia overpressure (l,lE-3/y), Ammonia storage tank from an earthquake (1.3E-3/y),... 

Paptizoglou, I.A., et al, 1990a, Probabilistic Safety Analysis of an Ammonia Storage Plant," PSAM-I, Beverly Hills California, February 4-7. 

If the possibility of reverse flow had been foreseen, then a slip-plate could have been inserted in the line leading to the ammonia storage vessel, as described in Section 1.1. 

When the ammonia storage capacities of Fe-ZSM5 and V205/W03-Ti02 are compared (not shown here), the much higher amount of ammonia desorbed from Fe-ZSM5... 

For some models adsorption or storage is important. For example, oxygen storage is important in a 3-way catalysis, a catalyst may contain a hydrocarbon storage component for improved low-temperature performance, and ammonia storage is important for ammonia SCR (selective catalytic reduction). Clearly, this sort of behaviour needs to be included in the final model. The nature of the measurements depends on the exact system being studied and will be discussed in more detail later. Suffice to say, from measurements at steady state, the heats of adsorption and coefficients of... 

HS(G)30 Storage of anhydrous ammonia under pressure in the UK spherical and cylindrical vessels, HSE, 1986 (Not in current HSE list).Gives advice for the appropriate materials of construction for ammonia storage vessels. 

Ammonia storage vessel 500m3 for one week supply of feed... 

Carbon steels such as BS1515, BS15110213 and ASTM A516 are the conventional materials used in the construction of ammonia storage units. For refrigerated (atmospheric) storage, low-temperature carbon steel is used88. 

Some of the steps that can be taken to help minimize the impact of SCC in ammonia storage are Complete stress relief, operation without air contact and the addition of small amounts of water (0.2%) as an inhibitor. Low-temperature carbon steels have considerably more resistance to SCC than normal carbon steels. This makes them the preferred material of construction for large atmospheric liquid ammonia storage tanks that operate at -33°C88. 

Figure 7.12. Anhydrous ammonia storage tank system.

The results for the warm and pressurized ammonia storage (unmitigated) and the refrigerated ammonia storage (mitigated) are summarized in Table 7.4. 

In this scenario, a dike 8.4 m by 8.4 m having a height of 1.5 m is placed around the refrigerated ammonia storage tank. The accidental failure of the 37.5-mm line occurs inside the diked area. All of the liquid ammonia released from the tank is contained inside the dike. The rate of flow of the liquid ammonia into the dike is the same as for the refrigerated example (Section 7.7.2). 

Working capital = 1 month feedstock supply < cost, except gaseous feed 2 months ammonia storage S100/ST. 

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