Purpose of Sulphur Measurement
- Corrosion protection of pipe lines.
- Catalyst protection in refinery/polymer reactor operations.
- Environmental protection agency compliance.
- Gas detection for personnel safety.
Common Sulphur Compounds
Sulphides Mercaptans
1. Hydrogen Sulphide H2S Methyl Mercaptan MeSH
2. Carbonyl Sulphide COS Ethyl Mercaptan EtSH
3. Dimethyl sulphide DMS Propyl Mercaptan PrSH
4. Methylethyl Sulphide MES Iso-Propyl Mercaptan i - PrSH
5. Diethyl Sulphide DES N-Butyl Mercaptan n-BuSH
6. Diallyl Sulphide DAS I-Butyl Mercaptan i-BuSH
7. Dipropyl Sulphide DPS
8. Dibutyl Sulphide DBS
Common Sulphur Compounds
Disulphides
1. Carbon Disulphide CS2
2. Dimethyl Disulphide DMDS
3. Methylethyl Disulphide MEDS
4. Diethyl Disulphide DEDS
5. Dipropyl Disulphide DPDS
6. Tetrahydro Thiophene THT
Methods of Measurement
Lead Acetate Tape type analysers
Chemiluminescence analysers
Ultraviolet radiation absorption spectrometers
Gas Chromatograph with FPD
Electrochemical cells for gas detection
X’ray Flourescence for % level detection.
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April 16th, 2007 at 10:40 pm
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January 6th, 2008 at 8:14 pm
The sulfiding process is a major operation. As the world leader in thio-chemicals, Arkema manufactures dimethyl disulfide (DMDS), an effective product with a high sulfur content. When used as a sulfiding agent, it can be combined with a personalized service called Carelflex® which offers users on-site technical assistance.
DMDS is used in a wide variety of applications, including:
* Oil refining: optimal maintenance of production units. DMDS is used in oil refineries as a sulfiding / presulfiding agent to activate the catalysts of hydrotreating units. This is an indispensable but delicate operation. That is why Arkema offers its clients , an on-site sulfiding service carried out by highly qualified technicians. Arkema has also developed an improved, lower odor version of DMDS called DMDS Evolution™.
* Petrochemicals: to reduce the number of decoking operations. Operators in the petrochemicals industry must protect their steamcracking coils against the formation of coke and carbon monoxide. DMDS by Arkema is the ideal sulfurous product for them. DMDS can be added continuously to the raw materials to maintain an optimal sulfur level, making it possible to reduce the number of decoking operations. The secondary reactions to these operations are easier to control and the production cycles are lengthened.
DMDS is also used in various other sectors, including:
* Fine chemicals, as chemical intermediate
* Metallurgy for its anti-corrosion properties.
January 6th, 2008 at 8:15 pm
HOW PERCHLOROETHYLENE
ENTERS AND AFFECTS YOUR BODY
Perc enters your body when you breathe its vapors in the air. Liquid perc can be absorbed through your skin, to a limited extent. The most common effects of overexposure to perchloroethylene are irritation of the eyes, nose, throat, or skin, and effects on the nervous system, as described below.
Skin: Lengthy or repeated skin contact with liquid perc removes the natural protective oils from your skin. This can cause irritation, dryness, cracking, and dermatitis (skin rash).
Eyes, Nose, and Throat: Perc vapors in the air at levels above 75 parts per million (see “Legal Exposure Limits”) may irritate your eyes, nose, and throat, causing burning and coughing. Perc does not have any long-term effects on the eyes, nose, throat, or lungs.
Nervous System: Perc, like most organic solvents, affects your brain the same way drinking alcohol does. Drinking alcohol within a few hours of exposure increases these effects, because the effects of perc and alcohol add together. The symptoms of short-term overexposure usually clear up within hours after exposure stops. The mildest effects listed below may start occurring at exposure levels of about 100 ppm. Effects occur more quickly and become more noticeable and serious as the exposure level increases. These effects may increase your chances of having accidents.
January 6th, 2008 at 8:16 pm
At very high exposure levels (above about 5,000 to 10,000 ppm) such as might occur in a tank or other enclosed space, perc and other solvents can cause loss of consciousness and even death.
If you are repeatedly overexposed for several days, you may be less affected as you develop a tolerance for overexposure. If a day or two then passes with no exposure, you may feel withdrawal symptoms such as nervousness, anxiety, and shakiness.
Some studies suggest that repeated, frequent overexposure to some organic solvents over months or years may have long-lasting and possibly permanent effects on the nervous system. The exposure levels at which these effects occur are not known, and the effects have not been studied in workers exposed only to perc.
The symptoms of these long-term effects include fatigue, poor muscle coordination, difficulty in concentrating, loss of short-term memory, and personality changes such as increased anxiety, nervousness and irritability.
Liver and Kidney: Exposure to high levels of perc - such as might occur in an enclosed space or during a spill - can damage the liver or kidneys. Unless you experience some of the more severe symptoms described above under “Nervous System,” your exposure probably is not high enough to cause liver or kidney damage.
Cancer: Perc causes cancer in laboratory animals at exposure levels close to the level legally allowed in the workplace. The animals were exposed to only twice the current legal exposure limit for California workers.
Although perc has been widely used in the dry-cleaning industry for the past 20 years, studies of dry-cleaners have not been adequately designed to show whether perc causes cancer in humans. Based on the animal tests, you should consider perc to be a potential cancer-causing substance (carcinogen).
Exposure to a carcinogen does not necessarily mean that you will get cancer. In general, the greater the exposure, the greater the risk of developing cancer. The best way to protect your health is to keep your exposure as low as possible.
Reproductive System: Perc does not appear to cause birth defects in lab animals. However, like other organic solvents, perc can harm a developing fetus if the mother is frequently overexposed. Perc inhaled by a pregnant woman can reach a developing fetus. Perc can also contaminate breast milk. Therefore, pregnant or nursing women should avoid overexposure, just as they should avoid exposure to alcohol, tobacco, and other drugs.
TESTS FOR EXPOSURE
AND MEDICAL EFFECTS
Perc does not remain in your body very long after exposure. Routine testing for the amount of perc in your body or for effects it may have caused is not recommended.
However, it is generally recommended that workers who are frequently exposed to hazardous substances receive a complete physical examination, including an occupational and medical history, at the beginning of their employment. They should also have regular periodic follow-up examinations.
A physician or other health care provider should choose specific tests on a case-by-case basis to evaluate effects of chemical exposure. HESIS physicians can provide advice for such medical evaluations.
LEGAL EXPOSURE LIMITS
California’s Division of Occupational Safety and Health (Cal/OSHA) sets and enforces workplace chemical exposure limits. Cal/OSHA has adopted a Permissible Exposure Limit (PEL) for the amount of perchloroethylene in your breathing zone. The PEL for perc is 50 parts of perc per million parts of air (50 “parts per million,” or 50 “ppm”). This is sometimes stated as 335 milligrams of perc per cubic meter of air (335 “mg/m3″).
The PEL for perc is based on preventing eye, nose, and throat irritation and nervous system effects. Because of the recent cancer findings in animals, HESIS has recommended that Cal/OSHA review and consider lowering the PEL.
Federal OSHA has reduced its 8-hour average PEL for perc to 25 ppm. Cal/OSHA will probably soon reduce its PEL accordingly.
Legally, your exposure may be above the PEL at times, but only if it is below the PEL at other times, so that your average exposure for any 8-hour workshift is 50 ppm or less. There is also an “excursion” limit of 200 ppm which can be exceeded for no more than 5 minutes every 3 hours, and a “ceiling” limit of 300 ppm which must never be exceeded for any period of time.
You should not rely on your sense of smell to warn you that you are being overexposed to perc. Some people can smell perc when the concentration in the air is well below the PEL, but others may not smell it even at much higher levels. Moreover, your sense of smell can become dulled after being around an odor for awhile. Measuring the amount of a substance in the air is the only reliable way to determine the exposure level.
If you work with perchloroethylene and think you may be overexposed, talk to your supervisor and/or your union. If any worker might be exposed to a substance at more than the legal exposure limit, the employer must measure the amount of the chemical in the air in the work area (Cal/OSHA regulation GISO 5155). You have the right to see the results of such monitoring relevant to your work (GISO 3204).
You also have the right to see and copy your own medical records and records of your exposure to toxic substances. These records are important in determining whether your health has been affected by your work. If your employers have such records, they must keep them and make them available to you for at least 30 years after the end of your employment.
January 6th, 2008 at 8:17 pm
The emulsion polymerization at 40°C. of mixtures of oxidized ethyl linoleate and styrene with potassium persulfate as catalyst yielded copolymers containing a maximum of one mole of ester per thirteen moles of styrene. A product of similar composition was obtained by bulk polymerization at 80°C.
When the amount of ester in the monomer mixture was increased to 50 per cent in the emulsion polymerization, the ester content of the polymer was increased and the molecular weight and yield were decreased.
From the Master’s Thesis of Jane Maxwell, University of Delaware, 1947; Armstrong Cork Company Research Fellow, 1945–1947.