Hydrodesulfurization

Hydrodesulfurization (abbreviated " HDS " ), the desulfurization of petroleum products by hydrogenation ( reaction of the compounds of sulfur with hydrogen). The method has considerable importance in the petroleum industry. There are hydrogenated components for the production of gas oil ( diesel fuel, heating oil ), but there are also intermediate products ( naphtha ) for further processing ( catalytic reforming, isomerization ) in order to protect sensitive catalysts before sulfur contamination. During this process, in addition to sulfur compounds and olefins, nitrogen and oxygen compounds are hydrogenated.

Application

Due to the strict environmental regulations are almost all important mineral fuels and fuels derived from hydrogenated components nowadays.

Motor gasoline specification of 10 mg / kg of sulfur can be obtained by hydrogenation of all the components. This low value is necessary in order to protect the sulfur-sensitive platinum catalyst doped vehicle.

A significant proportion of the kerosene is hydrogenated. This does not happen to the sulfur to remove (Jet A1 may have a sulfur content of 3000 mg / kg have ), but to hydrogenate other harmful compounds ( naphthenic acids, measured by the so-called Total Acid Number = TAN ).

The preparation of diesel fuel with 10 mg / kg of sulfur requires hydrogenation of all the components ( kerosene, gas oil). The engine burns the proportion of sulfur to SO2, or SO3. Finest SO3 droplets provide condensation nuclei is for carbon particles, high concentrations of sulfur thus lead to increased formation of fine dust.

Fuel oil will soon have a sulfur content <50 mg / kg have and thus also only consist of hydrogenated components.

In some refineries with a Cat Cracker unit ( FCC), the vacuum gas oil is hydrogenated to reduce the sulfur content of the FCC finished products.

In the manufacture of medical white oils and petrolatum base oils from crude oil processing hydrodesulfurization comes to industrial applications.

As use products either naphtha, kerosene and gas oils of different origin can be used in the process according to requirements. The catalysts used are nickel - molybdenum or cobalt -molybdenum catalysts. The liquid feedstock will (together with hydrogen-rich gas ) preheated by means of heat exchanger, brought to the required reaction temperature of about 320 to 360 ° C in a furnace and then to the reactor. The feed is at the reactor inlet then - depending on conditions - gas ( naphtha, kerosene ) or is in the 2- phase state ( gaseous / liquid, such as gas oils). Under pressures of 20 to 80 bar, depending on the design of the facility and the specific use of the product, the mixture reacts at the catalyst ( is the feed in a two - phase state, defined as the system catalyst - gaseous hydrocarbons, liquid hydrocarbons as a trickle phase System). The ending on catalyst hydrogenation reaction (see picture) ultimately leads to H2S and the hydrogenated hydrocarbon radical. In the reactor outlet, the sulfur- reduced product, unconsumed hydrogen and small amounts is formed by cracking light hydrocarbons (C1 - C4), and hydrogen sulfide.

In a first stage, the mixture is cooled and led a hydrogen-rich gas in the circuit back to use (so-called recycle ). Sometimes is located in a Recycle ( high pressure) to the amine scrubbing H2S from the recycle stream to remove (increase of the hydrogen partial pressure ). In a next step, the product mixture to remove the H2S and the light components is stripped ( stripping: Pull ). The stripped gas ( H2S, C1-C4) is freed in a so-called amine scrubbing of H2S and used as refinery fuel gas. The bound on the amine H2S is in a regenerator ( " stripping " of amine solution) from the solution again released and driven to the so-called Claus plant. There, the reaction is carried out with pure sulfur. The sulfur from desulphurization plants now contributes significantly to the global sulfur recovery. As a finished product of the HDS plant produced low-sulfur naphtha, kerosene, gas oil and vacuum gas oil.

Terms

Other names for this process are hydrofinished Hydrofining, hydrotreating.

Others

If there was a process by which ( " HFO " ) could be desulfurized heavy oil, then you could avoid the installation of flue gas desulfurization systems on large ocean-going vessels. A company called Alternative Petroleum Technologies (APT ) is said to have developed such a method; it should be cheap. According to APT, several large well-known institutions have conducted extensive tests.