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The application of double phase stainless steel in the oil refining industry

2.The stainless steel for petrochemical industry
Regarding the waste gas of the petroleum refining factory, natural gas or naphtha as the raw material, through a series of chemistry reaction, it can produce ethylene, propylene, ethyne, etc., a further synthesizing can produce polythene, polystyrene, acetone, butadiene, etc. The machining process after the synthesizing is similar to the chemical industry, and will contact various acidity mediums, the serving environment is very severe, and the variation scale for the medium condition is large, and the materials in use are wide, they involve stainless steel, iron-nickel base anti-corrosion alloy, and nickel base anti-corrosion alloy.

(1) Ethylene production.
0Cr25Ni20 or high carbon 0Cr25Ni20 centrifugal casting pipe is used in the furnace tube of the thermal decomposition furnace, which is a choice made according to the high temperature and high creep rupture strength. Incolog800 alloy is adopted in the pipeline. Under the low temperature condition, low temperature steel should be used, and the 0Cr18Ni9 is used only under the condition of -100--175℃.

(1) Ethyne 
In the production of ethyne, as the decomposing temperature is above 1100℃, the alloy brand in use is higher than the one used in producing ethylene.

(3) Other treating process
Other treating processes including oxidation, hydration, dehydrogenation, dehydration, alkylation, anisotropisation ect. The equipments will contact the relevant acidity mediums, and the materials in use are mainly 0Cr17Ni14Mo2 and 00Cr17Ni14Mo2，Inconel600、Incoloy800，No.20 alloy and Hastelloy B、C、D, etc. The process conditions of work are shown in the table below. In the process of petroleum chemical engineering, sulfuric acid, hydrofluoric acid, phosphoric acid, hydrochloric acid and other corrosive mediums need to be used in some processes. According to the acid concentration, different corrosion resistant materials are used with the different temperature.

The working condition of the processes in petrochemical industry

Sulfuric acid The variation scale for the concentration of the sulfuric acid in the petrochemical industry is very large, and the temperature can be up to around 100℃, the sulfuric acid concentration and temperature condition during some technique processes are shown in the following table. You can choose according to the material application principle of sulfuric acid industry in the mechanical industry.

The H₂SO₄ used in petrochemical industry

Phosphoric acid Used to make alcohol, synthesized detergent and interfacial active agent; for the various concentration H₃PO₄ with the concentration lower than 30% and a boiling temperature lower than 60℃, use 0Cr18Ni9, and for the high temperature and high concentration H₃PO₄, use 00Cr17Ni14Mo2.

Hydrochloric acid In petrochemical industry, hydrochloric acid is used in the production including the liquid-phase oxidation of ethylene to aldehyde, acetone production, anisotropisation, the halogenation technique for producing chlorinated ethenoid resin, under such environment, the common stainless steel is not corrosion resistant. Ni-Mo and Ni-Cu alloy are often used or nonmetallic material liner is used. And only for the diluted hydrochloric acid that contains air, use 0Cr17Ni12Mo steel.

The double phase stainless steel has been successfully used in petrochemical industry, shown in the following table:

The typical application of double phase stainless steel in petrochemical industry