Claus treatment

It is therefore related to such processes as the Alkazid (25) which involve preliminary hydrogen reduction to H2S before Claus treatment. 

Although H2S is at present a by-product of the desulfurization of fossil fuels on a large scale, only the recovery of free sulfur is carried out by the Claus treatment. On the other hand, the application of H2S decomposition as an H2 evolution method is proposed for use in the thermochemical process undertaken for water splitting. Thus, the thermochemical decomposition of H2S has wide-spread applications in various field. 

One of the principal aspects of refinery gas cleanup is the removal of acid gas constituents, ie, carbon dioxide, CO2, and hydrogen sulfide, H2S. Treatment of natural gas to remove the acid gas constituents is most often accompHshed by contacting the natural gas with an alkaline solution. The most commonly used treating solutions are aqueous solutions of the ethanolamines or alkah carbonates. There are several hydrogen sulfide removal processes (29), most of which are followed by a Claus plant that produces elemental sulfur from the hydrogen sulfide. 

An electrostatic precipitator is used to remove more tar from coke oven gas. The tar is then sent to storage. Ammonia liquor is also separated from the tar decanter and sent to wastewater treatment after ammonia recovery. Coke oven gas is further cooled in a final cooler. Naphthalene is removed in a separator on the final cooler. Light oil is then removed from the coke oven gas and is fractionated to recover benzene, toluene, and xylene. Some facilities may include an onsite tar distillation unit. The Claus process is normally used to recover sulfur from coke oven gas. During the coke quenching, handling, and screening operation, coke breeze is produced. The breeze is either reused on site (e.g., in the sinter plant) or sold offsite as a by-product. 

Currently, sulfur is mainly produced by the partial oxidation of hydrogen sulfide through the Claus process. The major sources of hydrogen sulfide are natural gas and petroleum refinery streams treatment operations. It has been estimated that 90-95% of the world s recovered sulfur is produced through the Claus process. Typical sulfur recovery ranges from 90% for a lean acid gas feed to 97% for a rich acid gas feed. ... 

This Standard was prepared specifically to cover medical laboratories. These laboratories carry out testing or examination of materials derived from the human body. Such studies are carried out for the purpose of providing information for the diagnosis, prevention and treatment of disease or assessment of the health of an individual. ISO 15189 covers a whole range of tests relating to clinical measurements, e.g. chemical and microbiological. This Standard is based on ISO 9001 and ISO/IEC 17025 and contains a correlation between the clauses and those in ISO 9001 and ISO/IEC 17025. 

Chance Also called Chance-Claus. A process for recovering sulfur from the calcium sulfide residues from the Leblanc process. Treatment of a suspension of the residues with carbon dioxide generates hydrogen sulfide, which is converted to sulfur dioxide by the Claus proces. The sulfur dioxide is converted to sulfuric acid. Developed by A. M. and J. F. Chance 1882 to 1887 and widely used until the Leblanc process was superseded by the Solvay process. 

A) articles recognized in the official United States Pharmacopeia, official Homeopathic Pharmacopeia of the United States, or official National Formulary, or any supplement to any of them and (B) Articles intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease in man or other animals and (C) Articles (other than food) intended to affect the structure of any function of the body of man or other animals and (D) Articles intended for use as a component of any articles specified in clause (A), (B), or (C). 

Cruzan v. Director, Missouri Dept of Health, 110 S. Ct. 2841 (1990) See also, Washington v. Harper, 494 U.S. 210, 221-22(1990) (recognizing a significant liberty interest in avoiding the unwanted administration of antipsychotic drugs under the Due Process Clause of the Fourteenth Amendment ) Vitek v. Jones, 445 U.S. 480,494 (1980) (forced admission to mental hospital and behavior modification treatment implicate liberty interests). 

A small sample which is provided only for identification or similar purposes and which is not intended to be used in treatment may be provided to any health professional but is otherwise subject to the requirements of Clause 17. 

Other items which may he made available to patients, for example by completing a request card enclosed with a medicine, should meet the relevant principles set out in Clause 18.2, that is they should be inexpensive and related to either the condition under treatment or general health. Care must be taken that any such activity meets all the requirements of the Code and in particular Clause 20. 

Recent development highlighted a shift in FDA position and interpretation of the market exclusivity clause. Under the orphan designation, three interferon products, Betaseron (IFN-pib), Avonex (IFN-pia) and Rebif (IFN-pia) are currently approved for treatment of multiple sclerosis (MS). The interplay in drug safety and efficacy consideration, business strategies, and regulatory rationale permitting approval of the three drugs for MS treatment is discussed in Box 3.5. 

Reductive Tail Gas Treatments. It was largely as a result of the effort to achieve better than 99% recovery that the reductive tail gas desulfurization processes (46) were developed in the 1970 s. The two main methods are the Beavon Sulfur Removal (BSR) (47) and the Shell Claus Off-Gas Treatment (SCOT) (48) processes. Both of these processes are now widely used as tail gas desulfurization units on sulfur recovery plants and can readily achieve point source emission levels below 250 ppm and below 100 ppm if necessary to meet regulatory standards. 

If sulfur capture must be greater than 95 percent, then treatment of Claus or Selectox tail gas will be required. 

Environmental regulations may force the "Claus" sulfur recovery to exceed 99%, requiring tail gas treatment. High CO2 in the original Claus feed, hence in the Claus tail gas, works strongly against the tail gas processes which use amine solution to extract H2S, and subsequently require incineration of residual H2S in a large volume of CO2. 

Choice b has a misplaced modifier—many people are not the fringe treatment. It is also wordy. The second clause in choice c is untrue. Choice d is unnecessarily wordy, and choice e is a sentence fragment. 

After the absorber/stripper unit, in conventional operations the pure H2S is fed to a Claus unit where the H2S is converted to elemental sulphur and H2O. The Claus unit can be equipped with an after-treatment to enhance conversions. Another method to decompose H2S to less harmful compounds is the thermal dehydrogenation of H2S to hydrogen and sulphur. Both processes will be treated in detail in the remainder of this chapter. 

The H2S concentration in the tail gas of a conventional Claus plant is still some 5%. This H2S is normally incinerated to S02 and released to the atmosphere. Due to stricter environmental regulations a large number of new technologies based on Claus tail gas treatment have been developed to minimise the S02 exhaust from sulphur recovery units. The Superclaus process and the Shell Claus Off-Gas Treating (SCOT) process are treated below. For descriptions of other tail-gas processes, the reader is referred to [2],... 

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