Iran Sulfur Exporter, Iran Sulfur, Sulfur Producer, Sulfur supplier, Sulfur producer

Sulfur



Sulfur

Sulfur or sulphur which is an abundant, multivalent nonmetal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. At room temperature, elemental sulfur is shining yellow, crystalline, and solid. Chemically, sulfur could react with all elements except gold, platinum, iridium, tellurium and the noble gases.

 

Elemental sulfur predominantly occurs naturally as the element (native sulfur), but it most commonly occurs in combined forms as sulfide and sulfate minerals. Being abundant in native form, sulfur was known in ancient era, as it has been mentioned for its applications in ancient Greece, ancient India, Egypt, and China. In the Bible, sulfur is called brimstone. Nowadays, almost all elemental sulfur is produced as a byproduct of removing sulfur-containing contaminants from natural gas and petroleum. The most prominent commercial application of the element is to produce sulfuric acid for sulfate and phosphate fertilizers, and other chemical procedures. The element sulfur is used in matches, fungicides, and insecticides. Many sulfur compounds are odoriferous, and the smells of odorized natural gas, grapefruit, garlic, and skunk scent are due to organosulfur compounds. Hydrogen sulfide emits rotting eggs odor.

 

Oil & Gas Sulfur

This useful material could be produced in the middle of distillation procedure, while Sulfur content of sour oil is separating as a high-demanding by-product. Of all the hetero-elements in crude oil, sulfur has the most important effects on refining.

  • Sufficiently high sulfur levels in refinery streams can (1) deactivate (“poison”) the catalysts that promote desired chemical reactions in certain refining processes, (2) cause corrosion in refinery equipment, and (3) lead to air emissions of sulfur compounds, which are undesirable and may be subject to stringent regulatory controls.
  • Sulfur in vehicle fuels leads to undesirable vehicle emissions of sulfur compounds and interferes with vehicle emission control systems that are directed at regulated emissions such as volatile organic compounds, nitrogen oxides, and particulates.

 

Fig 1. 2012 Sulphur Production

 

Consequently, refineries must have the capability to remove sulfur from crude oil and refinery streams to the extent needed to mitigate these unwanted effects. The higher the sulfur content of the crude, the greater the required degree of sulfur control and the higher the associated cost.

The sulfur content of crude oil and refinery streams is usually expressed in weight percent (wt%) or parts per million by weight (ppmw). In the refining industry, crude oil is called sweet (low sulfur) if its sulfur level is less than a threshold value (e.g., 0.5 wt% (5,000 ppmw)) and sour (high sulfur) if its sulfur level is above a higher threshold. Most sour crudes have sulfur levels in the range of 1.0–2.0 wt%, but some have sulfur levels > 4 wt%.

Within any given crude oil, sulfur concentration tends to increase progressively with increasing carbon number. Thus, crude fractions in the fuel oil and asphalt boiling range have higher sulfur content than those in the jet and diesel boiling range, which in turn have higher sulfur content than those in the gasoline boiling range. Similarly, the heavier components in, say, the gasoline boiling range have higher sulfur content than the lighter components in that boiling range.

 

Depending on the amount of sulfur the crude oil can be sweet or sour. When the total sulfur level in the oil is less than 0.5 % the oil is called sweet and if it is more than that the oil is called sour. Sweet crude oil is more preferred by refineries as it contains valuable chemicals which is needed to produce the light distillates and high quality feed stocks.

Historically, early prospectors tasted the crude oil to determine its quality. Crude petroleum had a sweet taste and pleasant smell if the content of sulfur was low. For this reason, sweet crude is a low sulfur crude oil (FSU, 2010).

Sweet crude is easier to refine and safer to extract and transport than sour crude. Because sulfur is corrosive, light crude also causes less damage to refineries and thus results in lower maintenance costs over time.

Major locations where sweet crude is found include the Appalachian Basin in Eastern North America, Western Texas, the Bakken Formation of North Dakota and Saskatchewan, the North Sea of Europe, North Africa, Australia, and the Far East including Indonesia.

 

Table 1. Quality levels - API gravity and sulfur content (Eni, 2012)

  Crude Oil Class

Property Range

Gravity (API)

Sulfur (wt. %)

Ultra-Light

>50

<0.1

Light & Sweet

35-50

<0.5

Light & Medium Sour

35-50

0.5-1

Light & Sour

35-50

>1

Medium & Sweet

26-35

<0.5

Medium & Medium Sour

26-35

0.5-1

Medium & Sour

26-35

>1

Heavy & Sweet

10-26

<0.5

Heavy & Medium Sour

10-26

0.5-1

Heavy & Sour

10-26

>1

 

 

As opposed to sweet crude sour crude is sold at a discount to lighter sweeter grades. Because the sulfur compounds in the crude oils are generally harmful impurities, they are toxic, have an unpleasant odor, contribute to the deposition of resin and in combination with water causes intense corrosion (K-Oil, 2012). Even though it does not restrain the production of inconvenient crude and the data shows that from 1995 to 2011 medium sour and sour crude has been the major hydrocarbon produced in the world taking about 55 to 60% of whole crude production, which is shown in Table 2.

Major regions with vast sour crude reserves: North America (Alberta (Canada), United States' portion of the Gulf of Mexico, and Mexico), South America (Venezuela, Colombia, and Ecuador), Middle East (Saudi Arabia, Iraq, Kuwait, Iran, Syria, and Egypt).

 

Table 2. Crude production by sulfur content (thousand barrels/day) (Eni, 2012)

 

1995

2000

2005

2008

2009

2010

2011

World

62759

68008

73862

74673

73062

74091

74700

Sweet

20395

22334

23325

23252

22892

23637

22539

Medium Sour

4946

6042

6593

8225

8477

8681

8757

Sour

31288

33821

38653

38010

36080

36036

37386

Unassigned Production

6130

5811

5292

5185

5613

5736

6018

(Percentage)

Sweet

32.5

32.8

31.6

31.1

31.3

31.9

30.2

Medium Sour

7.9

8.9

8.9

11.0

11.6

11.7

11.7

Sour

49.9

49.7

52.3

50.9

49.4

48.6

50.0

Unassigned Production

9.8

8.5

7.2

6.9

7.7

7.7

8.1

 

 

 

Fig 2. Global Sulphur Demand

 

 

Fig 3. Global incremental changes to supply by source, 2012 - 2017

 

Sources of Sulfur

Sources of elemental sulfur in natural gas streams include:

  • Elemental sulfur in the hydrocarbon-bearing reservoir
  • Sulfate reduction in the reservoir due to production fluid chemistry
  • Microbial action in the reservoir or at the surface
  • Thermal decomposition of sulfur compounds during compression or other processing steps
  • Catalytic decomposition in surface equipment, and
  • Catalytic oxidation of H2S due to oxygen ingress.

Eliminating the source of the problem is always the best solution from a technical standpoint. It is readily seen that some of these sources are relatively easy to eliminate, such as putting a nitrogen blanket on the tanks of surface chemicals to prevent dissolved oxygen from entering the wellbore or surface piping. That oxygen can then react with any H2S present to form elemental sulfur. Recall that dissolved oxygen is typically in the single digit ppm range while ESD can occur with sulfur in the ppb range. Thus, eliminating the oxygen eliminates one source of the problem. Similarly, changing production fluids can have an analogous effect.

Most sources are not so easy to eliminate. If elemental sulfur exists in the reservoir it cannot be separated from the production process. Microbes are notoriously difficult to eliminate – mitigation of that problem is normally the best one can hope for. In theory, thermal decomposition can be controlled or mitigated by selection of compression ratios, but it is difficult to accomplish in practice considering economics. Because the catalyst mentioned in two of the items above is iron, it is difficult if not impossible to remove the catalyst from the design of production equipment.

 

Sulfur Production

TECHNOLOGIES

 

Different methods of sulfur recovery and tail gas cleanup are mentioned below:

  • Straight-Through Claus
  • Split-Flow Claus
  • Direct Oxidation
  • Acid Gas Enrichment
  • Oxygen Enrichment
  • Cold Bed Adsorption
  • Shell Claus Off-Gas Treating (SCOT)

 

Catalytic Reaction Completes the Process

Any further conversion of the sulfur gases must be done by catalytic reaction. The gas is reheated by one of several means and is then introduced to the catalyst bed. The catalytic Claus reaction releases more energy and converts more than half of the remaining sulfur gases to sulfur vapor.

This vapor is condensed by generating low-pressure steam and is removed from the gas stream. The remaining gases are reheated and enter the next catalytic bed.

This cycle of reheating, catalytic conversion and sulfur condensation is repeated in two to four catalytic steps. A typical SRU has one free-flame reaction and three catalytic reaction stages. Each reaction step converts a smaller fraction of the remaining sulfur gases to sulfur vapor, but the combined effect of the entire unit is to reduce the hydrogen sulfide content to an acceptable level.

High Yields Plus Energy Claus sulfur plants can normally achieve high sulfur recovery efficiencies.

For lean acid gas streams, the recovery typically ranges from 93% for two-stage units (two catalytic reactor beds) up to 96% for three-stage units.

For richer acid gas streams, the recovery typically ranges from 95% for two-stage units up to 97% for three-stage units. Since the Claus reaction is an equilibrium reaction, complete H2S and SO2 conversion is not practical in a conventional Claus plant. The concentration of contaminants in the acid gas can also limit recovery. For facilities where higher sulfur recovery levels are required, the Claus plant is usually equipped with a tail gas cleanup unit to either extend the Claus reaction or capture the unconverted sulfur compounds and recycle them to the Claus plant.

All Claus SRU’s produce more heat energy as steam than they consume. This is particularly true for those plants equipped with waste heat boilers on the incinerator. The steam produced can be used for driving blowers or pumps, reboiler heat in the gas treating or sour water stripping (SWS) plants, heat tracing, or any of a number of other plant energy requirements.

Figure 4. Typical strait through sulfur plant

 

 

 


Contact Us

Phone:+98 21 88 63 5592
Fax: +98 21 88 63 5568
Email: Info@mgtpetroil.com