TECHNICAL FIELD

The invention relates to a device for removing undesirable compounds from mineral oil, wherein a dispersion containing an alkali metal is added to the mineral oil and the undesirable compound is destroyed, and a product of the alkali metal is removed with the undesirable compound from the mineral oil. The invention further relates to such a device for carrying out the method for removing undesirable compounds from mineral oil with a reactor for receiving the mineral oil to be treated.

The term "mineral oil" includes the following possibilities: crude oil, used engine oil, white oil as well as products from the catalytic pressureless depolymerisation process, thermo- catalytic low temperature conversion, pyrolysis or a different technical depolymerisation method, and also diesel, petrol and aviation fuel.

The undesirable compounds in the mineral oil are frequently sulphur-containing compounds, silicon compounds and aromatic compounds.

A dispersion is to be understood to be a disperse phase in a dispersion medium, whereby it can be a molecularly, colloidally or coarsely dispersed solution, in particular an emulsion.

PRIOR ART

A desulphurisation method for fuels such as diesel, petrol or aviation fuel is known for example from WO 2006/039125 Al . In this desulphurisation method, a dispersion with free sodium is used in order to convert sulphur compounds .

DE 23 26 696 discloses a method for desulphurisation of oil with alkali metal and a hydrogen-containing gas flow. Disadvantages of this method are the use of hydrogen as an additional auxiliary reactant and the need to apply a high pressure. Processing of reaction residues requires very great resources and is thus cost-intensive.

DE 11 30 544 discloses a method for desulphurisation, wherein, besides sodium, additionally sodium-organic compounds are used. The method has a high number of method steps and therefore also requires great resources and is cost-intensive .

THE INVENTION

The problem forming the basis for the invention is to create a method for breaking down undesirable compounds in the mineral oil which has a particularly simple structure and significantly reduces the content of undesirable compounds in the mineral oil. Furthermore a particularly simply structured device is to be created for carrying out the method.

The first problem mentioned is solved according to the invention by the dispersion consisting of mineral oil and alkali metal and the proportion of the alkali metal being 1 to 40 wt. % and the dispersion being added to the mineral oil to be treated. It proves surprising with this design that the sulphur content in the mineral oil can fall to below 10 ppm. Silicon compounds and aromatic compounds are likewise considerably reduced. The method according to the invention is thus suited for the processing of mineral oil, loaded with undesirable compounds, for diesel oil, petrol or aviation fuel. Owing to the invention, further catalysts, auxiliary reagents such as hydrogen or increased pressures are not required. Already de-sulphurised mineral oil or (paraffinic) white oil is preferably used for the dispersion. Sodium is preferably used as alkali metal which is easier to handle than other alkali metals such as potassium. The treatment temperature, the dwell time, the exact content of the alkali metal in the dispersion must be adapted to the composition of the mineral oil to be treated.

A particularly high degree of removal of sulphur, possibly silicon compounds and aromatic compounds, can be easily achieved according to another advantageous development of the invention if the temperature of the mineral oil to be de-sulphurised and the dispersion is 100 to 360°C, preferably 220 to 310°C.

A particularly high degree of desulphurisation and degree of breakdown of further undesirable compounds can be easily achieved according to a further advantageous development of the invention if the proportion of the alkali metal is 10 - 33 wt %. in the dispersion. A reaction of the alkali metal with acidic components of the mineral oil to be treated can be easily avoided according to another advantageous further development of the invention if the mineral oil to be treated is mixed with a caustic solution before addition of the dispersion, and subsequently an aqueous phase and contaminations are separated from the mineral oil. Undesirable reaction products are hereby avoided and in addition the consumption of alkali metal is kept particularly low. The second problem mentioned, namely the creation of a particularly simply structured device for carrying out the method, is solved according to the invention in that the reactor has a feeder for feeding the dispersion of mineral oil and alkali metal into the mineral oil to be treated. The feeder feeds the dispersion to the mineral oil to be treated with the provided pressure and the desired atomisation of the alkali metal.

The reactor can for example be any heated container. The resources for additional method steps or separate containers can, however, be kept particularly low according another advantageous development of the invention if a distillation plant for distillation of the mineral oil is designed as a reactor. Through this design the undesirable compounds can also be reduced in the same work step, in which the mineral oil is distilled. In the simplest case, the device according to the invention with the feed means and a storage container requires no further components. As the mineral oil to be distilled must anyway be heated in the distillation plant the method according to the invention does not lead to an increase in the energy consumption through further heating.

A particularly long dwell time of the mineral oil to be treated can be easily ensured according to another advantageous development of the invention if the reactor is formed as a tubular reactor. Through this design, a great breakdown of the sulphur content in the mineral oil and other undesirable compounds in the mineral oil can be achieved also with inert undesirable compounds.

An even mixing of the dispersion with the mineral oil to be treated can easily be ensured according to another advantageous development of the invention if the reactor has an agitator. The effectiveness of the process can be increased through this design.

Undesirable reactions can be easily avoided according to another advantageous development of the invention if a mixer with a separator of an aqueous phase is provided upstream of the reactor and the mixer is designed to mix the mineral oil to be treated with a caustic solution.

A contribution to the further reduction of the structural resources of the device is achieved according to another advantageous development if the reactor has a device for separating reaction products in the treated mineral oil. Disposal of the separated reaction products can then be carried out.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention allows numerous embodiments. One of these is shown in the drawing and described below by way of further clarification of the operating principle of the invention.

Fig. 1 - shows a method according to the invention for removing undesirable compounds from mineral oil, Fig. 2- shows, schematically, a device for carrying out the method.

BEST WAY OF IMPLEMENTING THE INVENTION

Fig. 1 shows a flowchart of a method according to the invention for desulphurisation and possibly the reduction of silicon compounds and aromatic compounds of a mineral oil 1. In a first step SI, a caustic solution is added to the mineral oil in order to remove acidic components. In a second step S2, the mineral oil is drained and the constituent parts removed are separated together with the excess caustic solution. In a step S3, a dispersion 11 of paraffinic white oil and alkali metal is added to the drained mineral oil. It can be added for example by means of a suitable injector or by other methods of mixing with a dosing pump. Undesirable compounds in the drained mineral oil are thereby destroyed in a reactor or a distillation plant. The sulphur connects to the alkali metal and precipitates. Subsequently in a step S4 , the compound of alkali metal and sulphur as well as possible residue of the alkali metal can be separated. De- sulphurised mineral oil 2 is produced as a product of the method, wherein possibly contained silicon compounds and aromatic compounds are considerably reduced. Fig. 2 shows schematically a device for carrying out the method according to claim 1. The device has a reactor 3 with a feeder 4 which is connected to a storage container 5. A static mixing device or an agitator 6 is arranged in the reactor 3. A mixer 7 with a separator 8 is arranged upstream of the reactor 3.

Mineral oil 1 to be de-sulphurised and a caustic solution 9 are fed to the mixer 7. Phases 10 thereby produced with impurities are separated by the separator 8 from the mineral oil and removed from the device. The mineral oil pre-treated in this way passes into the reactor 3, in which, in the case of a temperature mostly between 100 and 360°C, a dispersion with maximum 40 wt. % alkali metal is fed from the storage container 5. The agitator 6 ensures a sufficient mixing of the alkali metal and the mineral oil . The treated mineral oil 2 can subsequently be removed from the device. The reactor 3 additionally has a device 12 to separate and remove different reaction products and foreign substances 16 from the treated mineral oil 2.

The reactor 3 can be a distillation plant (not shown in further detail) for distilling the mineral oil.

Alternatively, the reactor 3 can also be designed as a tubular reactor.