Ammonia (Ammonia, i.e., ammonia), nitrogen and hydrogen in the compound, of the formula NH₃, is a colorless gas with a strong irritating odor. Very soluble in water, 1 volume of water can dissolve 700 times volume of ammonia at normal temperature and pressure, an aqueous solution is also called ammonia.
The cooling and pressurizing can become a liquid, and the liquid ammonia is a refrigerant. Ammonia is also an important raw material for the manufacture of nitric acid, fertilizers, and explosives.
Ammonia is very important to living things on Earth, and it is an important component of many foods and fertilizers. Ammonia is also a direct or indirect component of all drugs. Ammonia has a wide range of uses, and it also has hazardous properties such as corrosiveness.
Because ammonia has a wide range of uses, ammonia is one of the most abundant inorganic compounds in the world, and more than 80% of ammonia is used to make fertilizers. Since ammonia can provide a lone pair of electrons, it is also a Lewis base.
Chemical properties (ammonia formula)
Reaction with oxygen
Ammonia gas can be burned in pure oxygen. The product is a component of the air and does not pollute the environment. Therefore, it has certain prospects for use:
The catalytic oxidation of ammonia is an exothermic reaction, and the product is NO. It is an important reaction for the industrial production of nitric acid, provided that the catalyst is at a high temperature:
In addition to this, it can also exhibit reducibility in the following reactions:
Reaction with water(ammonia formula)
Ammonia is very soluble in water. When dissolved in water, it reacts with water to form ammonia monohydrate. It is commonly called ammonia water. The concentration of commercially available ammonia water is 25% to 28%. Ammonia is weakly alkaline because of the presence of such ionization in water:
Ammonia water turns the phenolphthalein solution red, turning the wet red litmus paper blue.
Reaction with metal
NH 3 can also complex with metal ions such as Ag, Cu, etc. to form a complex:
Ammonia can react with acids to form ammonium salts, such as:
Ammonia reacts with volatile acids (nitric acid, hydrochloric acid) to emit white smoke, and these reactions can be used to check the presence of ammonia. ammonia formula
(1) Gases that are colorless and have a pungent odor
Ammonia has a stimulating effect on the eyes, nose, and throat of the human body. Inhalation of a large amount of ammonia gas can cause short-term nasal congestion and cause suffocation, and eye contact is easy to cause tearing, and care should be taken when contacting. If you accidentally come into contact with too much ammonia, you should inhale fresh air and water in time, and rinse your eyes with plenty of water.
(2) Density is smaller than air
The density of ammonia is 0.771g/L (under standard conditions)
(3) Lower boiling point
Ammonia is easily liquefied, cooled to -33.5°C under normal pressure or pressurized to 700 KPa to 800 KPa at normal temperature, and gaseous ammonia is liquefied into a colorless liquid while releasing a large amount of heat. When liquid ammonia vaporizes, it absorbs a large amount of heat, causing the temperature of the surrounding material to drop sharply, so ammonia is often used as a refrigerant. Some old-fashioned popsicles used to be made of ammonia.
(4) Soluble in water
Ammonia is very soluble in water, and at room temperature and pressure, 1 volume of water can dissolve about 700 volumes of ammonia.
Ammonia fountain experiment
The 250 ml flask was filled with ammonia and poured into a phenolphthalein solution tank, and a red fountain phenomenon was observed
The main uses of ammonia are nitrogen fertilizers, refrigerants, and chemical raw materials.
Organic aspects are widely used in synthetic fibers, plastics, dyes, urea, etc.
Process classification of ammonia: low-pressure method, medium pressure method, high-pressure method.
Several synthetic ammonia processes:
American KBR Process
The KBR process is generally used in large-scale ammonia plants using natural gas as raw materials. It is also widely used in the coal chemical industry. It uses horizontal radial flow ammonia synthesis tower internals and combined ammonia refrigeration system refrigeration.
The hydrogen at the outlet of the purification device is mixed with the high-purity nitrogen molar ratio obtained from the air separation by 3:1, and the mixed synthesis gas is compressed to 15.5 MPa in the syngas compressor, and the feed and the product are heat-heated and then reheated. Enter the synthesis reactor.
The reaction gas temperature of the ammonia synthesis tower is about 441.5 ° C, and the ammonia content volume fraction is about 20.3%.
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The heat at the outlet of the tower is used for by-product steam or preheating boiler feed water. The heat-recovered gas enters the heat exchanger to preheat the outlet gas of the syngas compressor, and then finally cools to 0 °C through a water cooler and a combined ammonia cooler.
The ammonia separator separates the condensed liquid ammonia. The circulating gas after ammonia separation is recovered by the combined ammonia cooler, and then enters the compressor cycle section to join the fresh gas, and the above cycle is repeated.
The liquid ammonia separated by the ammonia separator enters the flash tank, and the dissolved gas is flashed off by depressurization. The flashed liquid ammonia is sent to the freezing section, and the flashed gas is sent to the fuel gas pipe network.
Danish Topsøe Process (Processes | Haldor Topsoe)
Topsoe is a leader in the patented synthetic ammonia process technology, with a market share of 50% of the total capacity of all newly constructed ammonia plants built after 1990.
This position is based on Topsoe’s decades of continuous efforts and experience in all important disciplines in ammonia production and ammonia plant design.
In addition, Topsøe’s researchers are dedicated to the research of all relevant catalysts for the production of synthetic ammonia, ranging from basic research in thermodynamics and surface science of catalysts to applied research and development of catalysts and catalytic processes, and therefore Topsøe ammonia synthesis.
The catalyst for the technology can only be used with the KM type catalyst it developed.
The syngas from the gas purification unit is compressed to 17.8 MPa by a centrifugal syngas compressor, mixed with the recycle gas in a cylinder of the syngas compressor cycle to a synthesis pressure of 18.5 MPa and then enters the heat exchanger. ammonia formula
In the heat exchanger, the syngas is heated by the outlet gas from the synthesis column to a temperature of the synthesis column inlet of 126 °C.
After the synthesis gas reaction in the ammonia synthesis tower, the ammonia concentration at the outlet of the synthesis tower was 22.39%, and the outlet temperature of the reaction gas was 441 °C.
Most of the heat from the reactor outlet gas is recovered in turn in the boiler feed water preheater. The gas is then cooled by a heat exchanger, a water cooler, a cold exchanger, a first ammonia cooler, and a second ammonia cooler.
At this point, most of the ammonia produced by the reaction has been condensed and separated in a high-pressure ammonia separator. The gas from the high-pressure ammonia separator contains 3.84% ammonia, the temperature is 0°C and is heated by a cold exchanger to enter the synthesis gas compressor cycle.
The section is mixed with fresh air and then the above cycle is repeated. The ammonia of the high-pressure ammonia separator outlet is sent to the medium-pressure separator for decompression to 2.8 MPa, and the gas phase is sent to the fresh section of the syngas compressor. The liquid product ammonia is sent downstream.
Swiss Casali Process
The ammonia synthesis process of the Swiss company Casali is one of the most advanced ammonia synthesis technologies in China.
Casali internals is flexible in design and in various forms, usually in the form of a three-bed, one-cooled-heat exchange structure. ammonia formula
The process has many application examples in the domestic Kellogg process large-scale synthetic ammonia plant synthesis tower transformation, and also participates in the renovation project of the superheated wall tower and the ruthenium catalyst synthesis tower, and has accumulated rich experience in design and production operation.
The fresh syngas from the purification unit and the gas from the medium pressure ammonia separator are sent to the syngas compressor, and after being compressed and cooled in the fresh section, the recycle gas is compressed to 14.07 MPa (absolute) in the syngas compressor cycle section, and then feed into the heat exchanger.
The gas fed to the heat exchanger exchanges heat with the outlet reaction gas from the feed water preheater of the loop boiler, and the temperature is raised to 199.5 ° C and sent to the synthesis tower.
The temperature of the incoming gas is controlled by the bypass line on this side and simultaneously controls the inlet temperature of the third bed.
The incoming gas is sent to the ammonia synthesis tower to produce an ammonia synthesis reaction under the action of a suitable ammonia synthesis catalyst so that the ammonia content of the outlet rises to 19.75%.
The inlet temperatures of the first and second bed layers are controlled by the bypass gas of the internal heat exchanger. The synthesis tower reaction gas enters the boiler feed water preheater to recover heat.
The cooled reaction gas is then sent to a heat exchanger, a water cooler, a cold exchanger, and the liquid ammonia in the reaction gas is further condensed in a cold exchanger using a cold recycle gas from a high-pressure ammonia separator.
The outlet gas of the cold exchanger is connected to the two ammonia coolers to continue cooling, the condensation is completed and the liquid ammonia is separated in the high-pressure ammonia separator, and the flashed recycle gas is sent to the cold exchanger to cool the reaction gas, and then sent to the compressor for circulation segment.
The liquid ammonia of the high-pressure ammonia separator is depressurized in the intermediate pressure separator to about 2.81 MPa (absolute) flashing, and the flash vapor is recovered to the fresh section inlet of the compressor to complete the above cycle.
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In the production, transportation, storage and use of ammonia, if the pipeline, valves, storage tanks, etc. are damaged, leakage of ammonia gas may cause poisoning. Ammonia has a stimulating and corrosive effect on the skin mucosa.
High concentrations can cause serious consequences, such as chemical pharyngitis and chemical pneumonia. Inhalation of very high concentrations can cause reflex apnea and cardiac arrest.
Ammonia poisoning mechanism
Ammonia absorbs water in human tissue to form ammonia water, which can dissolve tissue proteins and saponify with fat.
Ammonia can destroy the activity of various enzymes in the body and affect tissue metabolism. Ammonia has a strong stimulating effect on the central nervous system.
- Ammonia is strongly irritating, inhaling high concentrations of ammonia. Ammonia poisoning mainly inhibits the central nervous system. Under normal circumstances, the central nervous system can inhibit the peripheral low-level center, and the central nervous system is inhibited, which inhibits its peripheral low-level center. The effect is weakened or even disappeared so that the peripheral low-level center is excited. Causes convulsions, convulsions, lethargy, and coma. Inhalation of very high concentrations of ammonia can cause cardiac arrest and respiratory arrest.
- Ammonia is a basic substance, and ammonia has a strong corrosive effect. Alkaline burns are more serious than acid burns, because the penetration of alkaline substances is strong, and the skin’s ammonia water burns deep, easy to infect, and difficult to heal, similar to 2-degree burns.
- Ammonia gas is inhaled into the respiratory tract to form ammonia water. Ammonia can penetrate the mucosa, alveolar epithelium into the submucosa, pulmonary interstitial, and capillaries, causing:
(1) Vocal cord paralysis, edema of the throat, tissue necrosis. Shedding of necrotic material can cause asphyxia. The damaged mucosa is susceptible to a secondary infection.
(2) Trachea, bronchial mucosal damage, edema, hemorrhage, spasm, etc. Affects the bronchial ventilation function.
(3) Alveolar epithelial cells, pulmonary interstitial, pulmonary capillary endothelial cells are damaged, permeability is enhanced, and pulmonary interstitial edema. Ammonia stimulates sympathetic excitation, causing lymphatic general palsy, blocked lymphatic drainage, and increased capillary pressure. Ammonia destroys alveolar surfactants. These effects ultimately lead to pulmonary edema. ammonia formula
(4) Mucosal edema increased inflammatory secretion, pulmonary edema, decreased alveolar surfactant, tracheal and bronchial stenosis and other factors seriously affect lung ventilation, ventilation function, resulting in systemic hypoxia.
Clinical manifestations of ammonia poisoning
Mild poisoning: irritations in the eyes, nose and throat, tearing, coughing, sneezing, coughing, hemoptysis, chest tightness, headache, dizziness, fatigue (liquid ammonia splashed into the eyes, should immediately open the eyelids to make the ammonia flow out, And timely cleaned with water) clinical examination of conjunctival, nasal and pharyngeal mucosa congestion, lungs can be heard and dry voice.
Severe poisoning: pulmonary edema, cerebral edema, edema of the throat, throat, suffocation, life-threatening if not rescued (compressed artificial respiration is strictly prohibited during the rescue).
Conventional treatment hazard treatment
- Get out of the poisoning scene quickly and breathe in fresh air or oxygen. Breathing stimulants may be used as appropriate when breathing is shallow or slow. Respiratory or cardiac arrest should be performed immediately. Should not give up easily. Throat fistula, vocal cord edema should be quickly intubated or tracheotomy.
- Remove clothing and thoroughly wash the skin exposed to ammonia with water or 1% to 3% boric acid water. Rinse the eyes with 1% to 3% boric acid water, then apply antibiotics and cortisone eye drops.
- Intravenous drops of 10% glucose solution, calcium gluconate, adrenocortical hormone, antibiotics, prevention of infection and laryngeal edema. ammonia formula
- Inhalation of dexamethasone and antibiotic solution.
- The comatose patient was treated with 20% mannitol 250ml intravenously every 6-8 hours to reduce intracranial pressure.
Leakage emergency measures
(1) A small amount of leakage.
Retreat all personnel in the area. Prevent inhalation of vapors and contact with liquids or gases. Disposers should use a respirator. It is forbidden to enter the confined space where ammonia gas may be collected and to enhance ventilation. It can only be blocked if it is safe.
Leaked containers should be transferred to a safe location and the valve relief should only be opened if safety is ensured. ammonia formula
The leakage material can be collected and adsorbed by inert absorbent materials such as sand and vermiculite. The collected spillage should be placed in a closed container with the appropriate label for disposal.
(2) A large number of leaks.
Dislocate all unprotected personnel in the site and transfer them upwards. The leaking personnel should wear a fully enclosed heavy chemical protective suit and wear an air breathing apparatus.
After personal protective measures are taken, the leaking area is diluted with a spray water flow. Through the dilution of the water gun, the ammonia gas on the site is gradually dispersed, and the leak point is blocked by the non-sparking tool.
Report to the local government and the “119” and local environmental protection departments and public security traffic police departments.
The content of the alarm should include the accident unit; the time and place of the accident, the name of the chemical and the amount of leakage, the degree of danger; the presence or absence of casualties and the name of the alarm person, phone. ammonia formula
It is forbidden to contact or cross the leaked liquid ammonia to prevent leakage into the gutters and drains and enhance ventilation. No smoking or open flames are allowed in the premises.
In the case of safety, it is necessary to plug or flip the leaking container to avoid liquid ammonia leakage. Spray water to suppress steam or change the flow of the vapor cloud, but it is forbidden to directly impact the leaked liquid ammonia or leak source with water.
Prevent spills from entering water bodies, sewers, basements, or confined spaces. It is forbidden to enter a confined space where ammonia gas may collect. After cleaning, all protective clothing and equipment should be removed before storage and reuse.
Fire emergency measures
In the process of storage and transportation, if there is a fire, the following measures should be taken:
(1) Alarm: promptly report to the local 119 fire and government. The content of the alarm shall include the unit of the accident; the time, place, name of the chemical, the degree of danger; the presence or absence of casualties and the name and telephone number of the alarm person.
(2) Isolation, evacuation, transfer of people in distress to safe areas, the establishment of a warning zone of about 500m, and traffic control on the main road leading to the accident site. Except for firefighting and emergency personnel, other personnel is forbidden to enter the warning zone and evacuate quickly. Unrelated persons.
(3) Before entering the fire, firefighters should wear chemical protective suits and wear a positive pressure breathing apparatus. Ammonia gas easily penetrates the clothes and is easily soluble in water. Firefighters should pay attention to the protection of parts with large amounts of perspiration, such as reproductive organs, underarms, and anus.
(4) Use dry powder or CO2 fire extinguisher in small fires, water curtain, misty water or conventional foam in case of fire.
(5) When the tank is flooded, extinguish the fire as far as possible or use a remote water gun or water cannon to save.
(6) Do not spray water directly on the leak or safety valve to prevent freezing.
(7) When the safety valve makes a sound or discoloration, it should be evacuated as soon as possible. Do not stay at the ends of the tank. ammonia formula.
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Ammonia occupational hazard prevention measures
(1) Ammonia workers should undergo a pre-work physical examination. Those with severe chronic bronchitis, bronchiectasis, asthma, and coronary heart disease should not engage in ammonia work.
(2) Work should use corrosion-resistant overalls, alkali-resistant gloves, glasses, rubber shoes, copper sulfate or zinc sulfate respirator, anti-virus masks should be checked regularly to prevent failure.
(3) When using ammonia water, put a basin of clean water beside the operator, just in case; in the process of ammonia transportation, carry 2 to 3 kettles filled with 3% boric acid solution for emergency treatment; When preparing a certain concentration of ammonia water, the goggles should be worn; when using ammonia water, the operator should be in the upwind to prevent ammonia from irritating the face; it is strictly forbidden to rub the eyes with your hands during operation, and wash your hands after operation. ammonia formula
(4) To prevent skin contamination, use 5% boric acid ointment.
(5) Equipped with good ventilation and exhaust facilities, suitable explosion-proof and fire-fighting devices.
(6) Eating, smoking, and open flames and sparks are prohibited in the workplace.
(7) Air respirators must be worn during the emergency rescue.
(8) When a leak occurs, the leaking part of the leaking cylinder is directed upward to prevent liquid ammonia from overflowing.
(9) Strengthen the sealing and automation of the production process to prevent running, running, dripping and leaking.
(10) Safety should be used during use, transportation, and storage to prevent container rupture and gas.
(11) On-site installation of ammonia gas monitor and timely alarm discovery.