New catalyst-based technology removes contaminants from produced fluids

June 5, 2000
A new catalytic oxidation technology developed by the Saltanat Scientific Research Center removes sulfur compounds from oil and gas better than existing technologies in Kazakhstan.
The Kalamkas field, Kazakhstan, is one site (above photo) with a demercapanization unit (below photo) that uses the G1Z-1 catalyst (Fig. 2).
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A new catalytic oxidation technology developed by the Saltanat Scientific Research Center removes sulfur compounds from oil and gas better than existing technologies in Kazakhstan.

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Kazakhstan's producing facilities stand to gain at least $150 million/year in improved product quality and quantity by revamping existing gas plants with this technology.

One main problem with Kazakhstan crudes is the presence of mercaptans, hydrogen sulfide (H2S), and carbonyl sulfide (COS). The Tengiz field flares about 2.0 billion cu m/year of gas, and the Prorva field burns about 0.5 billion cu m/year of gas.

The new technology uses GIZ-1, which is both a catalyst and a reagent. After being spent, GIZ-1 easily regenerates with air intake. The technology uses GIZ-1 in place of monoethanolamine (MEA) and eliminates the need for dehydration with diethylene glycol (DEG).

The introduction of GIZ-1-based technology allows increased quality and quantity of exported gas to Russia and Central Asia.

Existing technology

Kazakhstan has been using MEA technology to reduce mercaptans and H2S from gas for 50 years. The process initially adds 8.0% water to the gas, then passes it through a mixture of 15% MEA and 85% water. DEG helps remove water from the product.

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After this, the processed gas still has a high H2S, mercaptan, and moisture content with a low dewpoint. Combustion of the resulting gas yields undesirable gases such as SO2, NOx, and COS, which can damage both the population's health and the environment.

Thus, one disadvantage of MEA is that about 1.0 billion cu m/year/plant of gas is flared. With the new GIZ-1 technology, the gas could supply consumer needs instead.

Before the gas enters the MEA absorption plant, its moisture content is 0.02 mg/l. and dew point is -38 degrees C. The MEA absorption process removes 5.5 tonnes of water/day (dew point +35 degrees C.).

GIZ-1 advantages

The main advantages of the new GIZ-1-based technology are simplicity and cost effectiveness.

The technology costs less than MEA absorption because it requires fewer materials, such as equipment and reagents. The technology also requires less thermal energy to eliminate mercaptans and H2S.

GIZ-1 offers several other advantages, as follows:

  • Lower cost of a domestic catalyst.
  • Catalyst regeneration with air.
  • Elimination of mercaptans from the processed gas.

The process runs at 10-20 degrees C. and 0.1-2.0 MPa using standard industrial equipment (columns and separators).

The new process also eliminates the need for downstream gas dehydration because no liquids are in the processed gas. Ecological advantages include quadrupling the available gas for consumers and eliminating the low-pressure, high-pressure, and sour-gas flares.

Preliminary tests in June-August 1997 in the Atyrau, Kazakhstan, production facility show that the new catalyst can reduce the mercaptan content in diesel fuel by 50%.

The new catalyst eliminated H2S and mercaptans in the distillate and reduced the amount of COS by 72.4% from the distillate provided by Tengizchevroil (TCO), a Chevron Corp. joint venture established to produce and sell oil from the Tengiz field in western Kazakhstan.

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Table 1 shows the effect of GIZ-1 on other contaminants in the distillate.

The Shymkent refinery, in Kazakhstan, also conducted a test with GIZ-1 in 1996. In this test, the new catalyst replaced MEA in reducing LPG contaminants.

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Table 2 shows the results of the Shymkent test. After 2 days with the new catalyst, the mercaptan content in the LPG was 0.0008 vol %. MEA usually lowered mercaptan content to about 0.013 vol %.

New process

Fig. 1 shows the new catalytic process scheme for removing mercaptans, H2S, and COS from oil and gas.

The contaminated oil and gas mixture flows through Reactor 1 at a temperature of 10-20 degrees C. and a pressure of 1.0-10.0 atm. In Reactor 1, the oil and gas contacts the GIZ-1.

Sulfur-free gas moves from an upper opening in Reactor 1 to Compressor Station 4. The sulfur-free oil moves separately through an overflow opening.

The spent-water solution of catalyst GIZ-1 from the reactor goes through a drain hole to Regenerator 2.

The bottom of Regenerator 2 contains a manifold through which air is blown in to regenerate the catalyst. After regeneration, excess air exits through a pipe connection on top of the regenerator. Pump 3 returns the regenerated catalyst to Reactor 1.

Economics

With GIZ-1-based technology, Kazakhstan plants can export to Russia and Central Asia about 8.0 billion cu m/year at $35/1,000 cu m.

Plants can easily adapt GIZ-1-based technology to existing manufacturing schemes, using some existing equipment.

Construction of a new GIZ-1-based unit costs about $500,000. With $15-20,000/year catalyst costs, the new process will save more than $5 million in the first year.

Acknowledgment

The authors thank Tengizchevroil's administration for supporting scientific developments in Kazakhstan and for allowing the GIZ-1 tests.

The Authors

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E. Z. Aibasov is director of the Saltanat Scientific Research Center in Almaty, Kazakhstan. Previously, he worked for the Institute of Organic Catalysis and Electrochemistry in Almaty. Aibasov holds a PhD in chemistry science and in chemical engineering from the Institute of Organic Catalysis and Electrochemistry, Almaty.

G. E. Aibasov works at the Saltanat Scientific Research Center in Almaty, Kazakhstan.