[Basic Chemicals] Detailed guide to hazardous chemical processes, the most complete ever!
- Fluorination process
Reaction type: exothermic reaction. Key monitoring unit: fluorinating agent storage and transport unit.
Process overview:
Fluorination is the reaction that introduces fluorine atoms into the molecules of a compound; the process involving fluorination reactions is the fluorination process. The reaction of fluorine with organic compounds is strongly exothermic, and the large amount of heat released can destroy the molecular structure of the reactants and even cause ignition or explosion. Fluorinating agents are usually fluorine gas, halogen fluorides, noble gas fluorides, high-valent metal fluorides, hydrogen fluoride, potassium fluoride, etc.
Process hazards:
(1) The reaction materials have flammability and explosion hazards; (2) the fluorination reaction is strongly exothermic, and if the reaction heat is not removed in time, it easily leads to over-temperature and over-pressure, causing equipment explosion accidents; (3) most fluorinating agents are strongly corrosive and highly toxic, and during production, storage, transportation, and use, they can easily cause danger due to leakage, improper operation, accidental contact, and other accidents.
Typical processes:
(1) Direct fluorination: fluorination of yellow phosphorus to produce phosphorus pentafluoride, etc. (2) Fluorination with metal fluorides or hydrogen fluoride gas: reaction of metal fluorides such as SbF3, AgF2, and CoF3 with hydrocarbons to produce fluorinated hydrocarbons; reaction of hydrogen fluoride gas with aluminum hydroxide to produce aluminum fluoride, etc. (3) Displacement fluorination: fluorination of chloroform to produce difluorochloromethane; reaction of 2,4,5,6-tetrachloropyrimidine with sodium fluoride to produce 2,4,6-trifluoro-5-fluoropyrimidine, etc. (4) Preparation of other fluorides: preparation of anhydrous hydrogen fluoride from concentrated sulfuric acid and calcium fluoride (fluorspar), etc.
Key monitored process parameters:
Temperature and pressure in the fluorination reactor; stirring rate in the fluorination reactor; flow rate of fluoride; flow rate of additives; ratio of reactants; concentration of fluoride.
Basic safety control requirements:
Alarm and interlock of reactor temperature and pressure with reaction feed and emergency cooling system; stable control system for stirring; safety relief system; combustible and toxic gas detection and alarm devices, etc.
Recommended control methods:
During fluorination operation, strictly control fluoride concentration, feed ratio, feed rate, and reaction temperature. When necessary, automatic proportional control devices and automatic interlock control devices should be installed. Form interlock control among the temperature and pressure in the fluorination reactor, the stirring in the reactor, the fluoride flow rate, and the cooling water inlet valve of the fluorination reactor jacket; set up an emergency shutdown system at the fluorination reactor, which automatically stops feeding and shuts down urgently when the temperature or pressure in the fluorination reactor exceeds the limit or the stirring system fails. Safety relief system.
The diagram is for reference only!
- Hydrogenation process
Reaction type: exothermic reaction. Key monitoring unit: hydrogenation reactor, hydrogen compressor.
Process overview:
Hydrogenation is the reaction that adds hydrogen atoms to the molecules of organic compounds; the process involving hydrogenation reactions is the hydrogenation process, mainly including hydrogenation of unsaturated bonds, hydrogenation of aromatic ring compounds, hydrogenation of nitrogen-containing compounds, hydrogenation of oxygen-containing compounds, hydrogenolysis, etc.
Process hazards:
(1) The reaction materials have flammability and explosion hazards; the explosion limit of hydrogen is 4%–75%, with high flammability and explosion characteristics; (2) hydrogenation is a strongly exothermic reaction. Under high temperature and high pressure, hydrogen contacts steel, and carbon molecules in the steel easily react with hydrogen to form hydrocarbons, reducing the strength of steel equipment and causing hydrogen embrittlement; (3) explosions are easily triggered during catalyst regeneration and activation; (4) unreacted hydrogen and other impurities in the hydrogenation reaction tail gas can easily cause ignition or explosion when discharged.
Typical processes:
(1) Hydrogenation of triple and double bonds of unsaturated alkynes and alkenes: hydrogenation of cyclopentadiene to produce cyclopentene, etc. (2) Hydrogenation of aromatics: hydrogenation of benzene to produce cyclohexane; hydrogenation of phenol to produce cyclohexanol, etc. (3) Hydrogenation of oxygen-containing compounds: hydrogenation of carbon monoxide to produce methanol; hydrogenation of butyraldehyde to produce butanol; hydrogenation of octenal to produce octanol, etc. (4) Hydrogenation of nitrogen-containing compounds: hydrogenation of adiponitrile to produce hexamethylenediamine; catalytic hydrogenation of nitrobenzene to produce aniline, etc. (5) Hydrogenation of oils: hydrocracking of distillate oil to produce naphtha, diesel, and tail oil; hydro-upgrading of residue; hydro-upgrading of vacuum distillate; catalytic (isomerization) dewaxing to produce low-pour-point diesel, lubricant base oil, etc.
Key monitored process parameters:
Temperature and pressure of the hydrogenation reactor or catalyst bed; stirring rate in the hydrogenation reactor; hydrogen flow rate; ratio of reaction materials; system oxygen content; cooling water flow rate; operating parameters of the hydrogen compressor; composition of hydrogenation reaction tail gas, etc.
Basic safety control requirements:
Alarm and interlock for temperature and pressure; ratio control and interlock system for reaction materials; emergency cooling system; stable control system for stirring; emergency hydrogen shutoff system; installation of safety valves, rupture discs, and other safety facilities; alarm and interlock for shutdown of the circulating hydrogen compressor; hydrogen detection and alarm devices, etc.
Recommended control methods:
Form interlock relationships among the temperature and pressure in the hydrogenation reactor, the stirring current in the reactor, the hydrogen flow rate, and the cooling water inlet valve of the hydrogenation reactor jacket, and set up an emergency shutdown system. Add a system for emergency cooling nitrogen or hydrogen. When the temperature or pressure in the hydrogenation reactor exceeds the limit or the stirring system fails, automatically stop hydrogenation, release pressure, and enter an emergency state. Safety relief system.
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