DE2936888A1 - METHOD FOR DESULFURING FOSSILEM FUEL - Google Patents

Description

Incon Anlagentechnik GmbH ^{September 12} , 1979

Eisenbahnstrasse 47

6650 Homburg / Saar B 1614 D / ra

description

Process for the desulfurization of fossil fuel 15

An important characteristic in the production of energy from fossil fuels, especially petroleum and coal, is the sulfur content of the fuel. In this fuel, sulfur is in a very different form from hydrogen sulfide up to very complex molecular structures. The combustion always produces S0_, which is easy is further oxidized to sulfuric acid. Sulfur dioxide and sulfuric acid pollute the air and are corrosive.

For crude oil increases with increasing boiling range of petroleum fractions _ ₀ tion of sulfur content. While middle oils generally contain about 1% sulfur, atmospheric residue from middle eastern oils can contain 2.5 to 4% sulfur. When burned as a fuel oil as much SO ₂ is produced that very high and costly chimneys are built müsoc sen to distribute the sulfur dioxide at high altitude.

In addition to environmental protection, there is another important issue

1300U / 0223

Point of view in the better use of the increasingly scarce energy sources. The optimization of the boiler operation of hot water and steam generators, a limit is drawn by the dew point of the sulfur dioxide in the flue gas or, in other words, a reduction in the sulfur content in the fuel enables the sulfur content to be reduced Flue gas temperature and thus a better utilization of the fuel.

If you consider that 85% of the oil production is used for energy production (Römpp's Chemie Lexikon, 7th edition (1973), 1939; in the case of coal, the percentage is likely to be even higher) one can appreciate the importance the sulfur content in these fuels.

Because of the importance of the sulfur content in petroleum, coal and other fuels set out above various processes for desulfurizing these fuels have long been developed.

The mercaptans can be removed from liquid gas and light petrol by washing with alkali. With increasing boiling range however, the solubility of the mercaptides decreases sharply in the fraction. In the so-called Merox process, therefore the mercaptans in the presence of caustic soda with oxygen using a special Merox catalyst to disulfides oxidized. This (and other processes in which the mercaptans are converted into disulfides) is carried out referred to as sweetening or sweetening.

As the boiling range of the petroleum fraction increases, not only does the sulfur content increase, but also the sulfur can then it can no longer be removed by sweetening processes, because it is built into more complex compounds that can only be broken under more severe conditions.

1300U / 0223

In these processes, known as hydrotreating, hydrofining or hydrodesulfurization, the petroleum fraction is passed together with hydrogen at temperatures of 320 to 420 ^° C. and pressures of 15 to 100 bar over special catalysts containing cobalt / molybdenum or nickel / molybdenum on alumina carriers.

The sulfur content of coal also fluctuates depending on the occurrence. ? ·. B. the sulfur content of German lignite is 1 to 2%, sometimes up to 5% or even more, while Ruhr coal contains 0.5 to 2.5% sulfur. In USA coal, the sulfur content can be considerably higher.

Except for dejj cases where the coal is larger in quantity Contains pyrites (marcasite), most of the sulfur in coal is organic, this sulfur only after breaking up of the more or less complex organic sulfur compounds can be removed.

For the desulfurization of coal, methods are known in which The inorganically bound sulfur (pyrite) is mechanically separated from the dry or wet, finely ground coal is, or the organically bound sulfur is reduced with hydrogen under pressure to hydrogen sulfide and separated becomes (SRC process). The inorganically bound sulfur (pyrite) can also be removed by the Meyers process be that one with iron (III) sulfate and atmospheric oxygen elemental sulfur oxidized.

The invention now relates to a method for the desulfurization of fossil fuels such as petroleum, coal and the like Treating the particulate, dis-

Pergierten fuel with a reducing agent at increased Te.nperatur, which is characterized in that one a metal with a negative redox potential is used as the reducing agent, which reacts with water under the reaction conditions

1300U / 0223

conditions did not develop gaseous hydrogen to a significant extent.

The method of the invention allows very good desulfurization of fuels with a wide variety of sulfur contents, with very low sulfur contents can be largely removed. The process of the invention avoids the use of hydrogen and is very economical, since all reactants can be regenerated in a simple manner. Another special one The advantage is that only the sulfur is removed while the other energy-carrying values of the fuel are removed remain. In contrast, most desulphurisation processes involve removal or removal. Destruction of the entire sulfur-containing molecule, so that up to 10% of the total energy content of the fuel is lost can go.

Finally, according to the invention, the desulfurization of oil with high Metal contents, especially nickel and / or vanadium, well through ™ feasible, which is either not possible at all or only very poorly according to the previous methods.

According to the invention, all metals are included as reducing metals negative redox potential, i.e. metals that are more negative than hydrogen, provided these metals do not develop gaseous hydrogen to a significant extent with water under the reaction conditions. On the In practice, this means that the limit is around -2 volts, with aluminum (-1.67 volts) being used on an industrial scale useful end link of the chain, which extends to the more positive side via manganese, zinc, chromium, iron, cadmium, Cobalt, nickel and tin extends to lead. In addition to the redox potential, play for the technical implementation But other aspects also play a role, e.g. the ability of the metal sulfide to be regenerated during the reaction and, last but not least, the price of the metal. Iron meets all of the above requirements best, which is why Iron is particularly preferred.

1 300U / 0223

- 6 1

The reducing metals are used in finely divided form. These It is used either as a fixed bed, optionally mixed with sand, or preferably as a fluidized bed. For this application is technical iron powder in the trade, and suitable fluidized bed grains are also available for the other metals.

^The process of the invention is carried out in an aqueous dispersion, the water having the following three functions:

1.) The water supplies the hydrogen required for the reaction, for the case of the reduction of disulfides the reaction equation I.

RSR ¹ +2 Fe + 2H ₂ O- * RH + R ¹ H + FeS + Fe (OH) ₂ (I)

In the case of mercaptans, the Re ^ ^- -ior * can also take place without the participation of water, at least in the balance, according to reaction equation II

RSH + Fe - »RH + FeS (II)

2.) The water serves as a contact mediator or reaction mediator between fuel and reducing metal, and

3.) the water serves as a dispersant for the fuel and in the preferred embodiment as a fluid for the fluid bed.

Since the amount of water required for the reduction according to 1.) is relatively small, the water requirement is primarily determined Line after functions 2.) and 3.). In practice, the desulphurisation of heating oil has water: oil volume ratios of about 1: 1 proved to be very beneficial. You can, however, both with a much larger one and with

1300U / 0223 ORIGINAL IMSPECTEO

work with a much lower water content.

c The oil droplet size of the oil emulsion is chosen so that that, depending on the reaction conditions, the desired degree of desulfurization is achieved. In the case of solid fuel, such as coal, the fuel grain size is also chosen so that the fuel flows into the fluidized bed with the IQ desired speed flows through. If necessary, one works with the addition of dispersing aids.

The process of the invention is carried out without the addition of alkali, that is to say at a neutral pH. Sometimes the sulfur content of the fuel (H ₂ S) leads to a certain pH shift towards acidity. However, this does not play a special role, in particular the addition of lye is not necessary.

The temperatures used in carrying out the process of the invention are not particularly limited as long as the liquid phase (dispersion) is maintained. In general, temperatures of 80 to 140 ^° C., preferably 90 to 110 ^° C., are used in an environmentally closed system.

On the one hand, the temperatures used should be as high as possible in order to achieve short reaction times; on the other hand, energy-consuming heating of the reaction mixture is to be avoided. Without direct further use of the desulphurized fuel, lower temperatures of up to about 90 ^° C. are therefore preferably used. On the other hand, when heavy fuel oil is burned in power stations, the fuel oil must be heated to around 120 ^° C. anyway because of the atomization properties in the burner systems. In this case, the desulfurization process will preferably be ^{carried out at 120 °} C. and then the desulfurized heating oil will be fed directly into the burner.

1300U / 0223

In the desulfurization of coal or other non-liquid fuels according to the method of the invention a certain difference to crude oil desulphurization as, after wet grinding or wet grinding of the solid Fuel, inorganic sulfur compounds, such as pyrites, which may be contained in larger quantities, preferably be removed beforehand by lye extraction. This also applies to soluble sulfates. As far as poorly alkali-soluble Sulfur compounds cannot already be separated by flotation, this sulfur is together with the insoluble sulphate sulfur is reduced to sulphide sulfur by reaction with the reducing metal.

After the reaction has ended, an oil / water phase separation takes place in the case of petroleum. Generally one gets one easy emulsion separation in common separators. In some cases, especially when emulsifiers (surface-active Substances) have been used, however, the use of emulsion breakers is advantageous. Suitable substances for this and the amounts to be used are known to the person skilled in the art.

In the case of solid fuels, such as coal, the Desulfurization is a sedimentation of the solid fuel. In some cases it is advantageous to use anti-wetting agents to add for faster sedimentation, especially if beforehand for better dispersion of the fuel particles Dispersing aids (surface-active substances) are used became. Suitable anti-wetting agents and the amounts to be used are known to the person skilled in the art.

After separation from the aqueous phase, the desulphurized fuel still contains a certain amount of water, im Case of heating oil about 2 to 3%. However, this has no disruptive influence and, in particular, does not have a disadvantageous effect on the energy balance.

1 300U / 0223

The metal sulfide formed by reducing the sulfur compounds is converted into metal oxide by the usual roasting and sulfur dioxide transferred. In the case of using iron as the reducing metal, iron sulfide is obtained when roasting iron oxide and sulfur dioxide results. The sulfur dioxide is processed to sulfur or sulfuric acid. The iron oxide can be reduced to iron and fed back into the process.

The use of sulfur represents a further advantage of the process of the invention. Conventional flue gas desulphurization takes place exclusively through the absorption of sulfur dioxide by means of milk of lime, which is initially hydrogen sulfite formed by oxidation in sulfate (gypsum) is convicted that is not accessible for reuse.

in a preferred embodiment of the method of In the invention, the reducing metal is used in conjunction with an activator. Substances come along as activators a redox potential in question, which is more positive than that of the reducing metal. Preferably it is

^{£ Ό} with the activator around a metal. A particularly preferred activator metal is copper, in particular also in combination with iron as a reducing metal.

The activator is preferably applied to the reducing metal

applied, e.g. by treating the reducing metal powder with an activator solution or dispersion, e.g. with a Solution of the activator metal salt, preferably a copper salt solution, soaks.

The amount of activator is not critical. Even very small amounts are sufficient, e.g. 0.01 to 2%, based on Reducing metal. The upper limit is determined by the amount of activator that does not require any further procedural

1300U / 0223

293688a

brings improvement.

c To achieve better wetting or a better one Contacts between the reducing metal and the liquid or solid fuel in the dispersion are preferred small amounts of wetting agents (surface-active substances) used. Suitable wetting agents are known to those skilled in the art IQ known. Usually very small amounts of e.g. only 2 to 10 ppm is sufficient.

The invention is explained below with reference to the drawing.

The single figure shows in a schematic representation a preferred embodiment of the method of the invention for desulphurisation of heating oil.

Sulfur-containing heating oil, circulating ^{water, v} ~ ' water and dispersing agents are fed in via lines 1, 2, 3 and 4, respectively. ^{After heating to approximately 100 °} C. in a heat exchanger 5, an emulsion is produced in a mixer 6, which is then fed into a first reaction column 7 from below. The reduction reaction of the iron powder with the sulfur compounds of the heating oil takes place in an iron powder fluidized bed 8. The iron powder used in the fluidized bed 8 has been produced in such a way that technical iron powder has been impregnated with a copper chloride solution, so that 2% by weight of copper, based on iron powder, is present. An overflow 9 at the upper end of the reaction column 7 serves as a separator for the separation of the oil-water-iron sulfide mixture from the unreacted iron powder. The overflow from the first reaction column is pumped through a second reaction column 11, which is an exact duplicate of the first reaction column. The overflow from this second reaction column 11 is passed into a first separator 13 via a line 12

1300U / 0223 ORIGINAL IWSPECTED BAD ORIGINAL

- 11 1

fed in. The iron sulphide formed is drawn off at the bottom of this first separator, which is then removed in the usual way c is roasted and further processed via a line 14 is then fed into a second separator 15, where the phase separation of the oil-water emulsion, if necessary with the addition of small amounts of anti-wetting agent. The desulphurized oil is then discharged via a line 16 and fed directly to the burner of a thermal power station. The water is discharged via line 2 and fed back into the process.

Both reaction columns 7 and 11 are thermally insulated and windows (not shown) through which the reaction can be observed. Electric heaters (not shown) make it possible to maintain a constant reaction temperature or to change the reaction temperature. A line 17 is fresh, activated Iron powder supplied in accordance with the iron consumption. The method described enables a Heating oil with a sulfur content of 3.5% by weight reduces the sulfur content to <0.1% by weight under the following conditions:

Water / oil ratio 1: 1

Reaction temperature 90 to 100 ^{0 C}

Average residence time 5 minutes per reaction column

3 2
Flow rate 0.4 m / m / h oil / water mixture Wetting agent and anti-wetting agent additive

on 1 to 5g / h

iron sulfide formed 95 kg / h
Heating oil throughput 1 t / h.

1300U / 0223

-41-

Blank page

Claims (4)

PATENT- AND LAWYERS LAWYER PATENTT ANWÄLTEJOCHEN PAGENBERG or jur. u. μ harvard WOLFGANG A. DOST dr.dipi UDO W. ALTENBURG D, PL -PH GALILEIPLATZ 1, 8000 MUNICH 80 TELEPHONE (0 89) 98 66 64 TELEX: (05) 22 791 pad d CABLE: PADBÜRO MUNICH date 12 September 1979 B 1614 D / ra claims 1. Process for the desulfurization of fossil fuels, such as petroleum, coal and the like, by treating the particulate, dispersed in an aqueous medium fuel with a reducing agent at elevated temperature, characterized in that as Reducing agent a metal with a negative redox potential 'used that with water under the reaction conditions does not develop gaseous hydrogen to any significant extent. 2. The method according to claim 1, characterized in that one iron is used as a reducing metal. 3. The method according to any one of claims 1 or 2, characterized in that that one uses a reducing metal with added activator. 4. The method according to claim 3, characterized in that one copper is used as an activator additive. 1 300U / 0223 "APPROVED REPRESENTATIVES AT THE EUROPEAN PATENT OFFICE PROFESSIONAL REPRESENTATIVES BEFORE THE EUROPEAN PATENT MANDATAIRES AGREES PRtS L 'OFFICE EUROPEEN DES BRf VETS ORIGINAL INSPECTED