AMMONIA DISSOCIATORS
Dissociated Ammonia is a dry, reducing, oxygen-free gas mixture with a composition of 75% Hydrogen and 25% Nitrogen, by volume. It is a gas with considerable reducing constituents, low dewpoint, virtually no impurities and thus capable of preventing oxidation of the most vulnerable materials at elevated temperatures, such as stainless steel. It is obtained by cracking anhydrous ammonia vapor in a catalyst filled vessel maintained at a temperature of 1700°F to 1850°F. The reactant ammonia is stored as a pressurized liquid in a tank or cylinder. It is drawn from the tank above the liquid-vapor interface to assure that anhydrous ammonia vapor is supplied to the dissociator.
The dissociator is provided with catalyst filled heat resisting alloy retorts. The retorts are mounted within the insulated dissociator heating chamber. Incoming ammonia pressure is reduced to 8 to 10 psig before retort entry. At the outlet of the retort the hot dissociated ammonia passes through a dry cooler where the gas is cooled to near room temperature. It then passes through a flowmeter and on to the consuming device.
The dissociator can be ordered with an electrically heated or gas-fired heating chamber. A chromel-alumel thermocouple will be provided to sense chamber temperature. The thermocouple signal will be wired to the input connections of a three term digital temperature controller which will regulate the thermal input delivered to the dissociator directly to maintain the heating chamber control temperature.
High limit and low limit temperature controllers will be provided for the dissociator. The high limit temperature control will terminate thermal input to protect the dissociator from damage caused by an overtemperature condition if the chamber temperature exceeds the limit setpoint. The low limit temperature controller will prevent inlet ammonia flow from entering the retort until the limit setpoint has been exceeded. A pressure reducing regulator will be provided in the ammonia vapor delivery line along with overpressure relief controls. A backpressure control regulator will be provided in the dissociated ammonia outlet line.
Sargeant & Wilbur Ammonia Dissociators are available in standard sizes ranging in capacity from 150 cubic foot/hour to 20,000 cubic foot/hour. Special designs larger or smaller than standard capacity are available at the customer's request. Any of the dissociators can be supplied with an integral ammonia vaporizer if the user operates from a liquid ammonia supply or if you wish to protect the process from liquid entrainment in the ammonia vapor inlet line.