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LECTURE (11) AMMONIUM NITRATE PRODUCTION Introduction:

Pharos University جامعه فاروس Faculty of Engineering كلية الهندسة Petrochemical Department قسم البتروكيماويات. LECTURE (11) AMMONIUM NITRATE PRODUCTION Introduction:

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LECTURE (11) AMMONIUM NITRATE PRODUCTION Introduction:

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  1. Pharos University جامعه فاروس Faculty of Engineering كلية الهندسة Petrochemical Department قسم البتروكيماويات LECTURE (11) AMMONIUM NITRATE PRODUCTION Introduction: • Ammonium nitrate is a fertilizer which has 35% content of nitrogen and can therfore be used with advantage on soils of all types and for all kind of crops. • It is cheap in production • It has unfavorable physical properties. • Its crystals melt when exposed to air (or cake) into large aggregates due to the hygroscopicity, high solubility in water and large temperature coefficient of solubility of the material.

  2. Temperature changes during storage results in a changeover from one crystalline form to another, re-crystallization, and this also tends to caking. • To decrease caking, ammonium nitrate particles are powdered using finely ground low hygroscopicity substances as limestone, phosphate rock, kaolin or are granulated with admixtures of nitrates of calcium and magnesium, or calcium phosphates. • For use as a fertilizer, it is manufactured in the form of granules. • Another use of it is in making explosives.

  3. Production: • It is made by neutralizing weak nitric acid with gaseous ammonia, evaporating the solution obtained and granulating the ammonium nitrate. • The neutralization stage is based on the following reaction: NH3 + HNO3→ NH4NO3 (ΔH = -20.6 Kcal) • This reaction is chemi-sorption in which the absorption of the gas by the liquid is accompanied by a rapid chemical reaction. • The reaction is diffusion controlled and highly exothermic.

  4. The heat of neutralization is utilized by evaporating water from the ammonium nitrate solution. • By using high strength nitric acid and heating the starting reagents, molten ammonium nitrate (concentration higher than 95 -96%) can be obtained.

  5. The reactor consists of a cylindrical vessel made of stainless steel with a second cylinder inside it (UHN reactor). • The inner space is for neutralization and the annular space is for evaporation. • The ammonium nitrate solution (60-80%), depending on the nitric acid concentration, flows to a vessel with an agitator (final neutralizer) and then to a multi stage vacuum evaporation unit.

  6. Two or three stages of evaporation are used. • The ammonium nitrate concentration is brought to 99% and transferred to a separator and then to prilling or granulating tower. • The granules are screened, cooled by air, drop onto a conveyor belt, which transport the product for dying ,coating and packing systems. Fines and oversized material are re-dissolved and sent to the neutralizing for recycle.

  7. Corrosion • Carbon steel can only be used in the NH3 storage and feed system. • Up to about 120ºC, Type 304, extra-low carbon (ELC) stainless steel is used for aqueous or 100 % HNO3. • where it is necessary to preheat 60% HNO3 to 170ºC, expensive tantalum metal is needed for this heat exchanger.

  8. Safety • The extreme reactivity of NH4NO3 with combustible materials and its sensitivity to explosive requiring safety precautions. • Any air used in drying must be free oil and other combustibles. • Safety in its design depends on that the equipment is designed for short residence times and low hold-up.

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