EP1950273A1 - Use of glycerol, glycerol-ethanol or glycerol-methanol blends as a fuel for furnaces - Google Patents

Abstract

Use of glycerin (I) as fuel additives or fuel substitutes in combustion plants, is claimed.

Description

Technical area

The present invention relates to the use of glycerol as an additive or substitute fuel in combustion plants.

Background of the invention

Glycerin is a colorless and odorless, viscous (viscous) and hygroscopic liquid at room temperature. Glycerin is a very versatile substance. Among other things, it is contained in cosmetics as a moisturizer because of its water-binding properties, it can be used as antifreeze, lubricant or plasticizer and is needed in the production of plastics, microchips, dyes and toothpaste. Furthermore, glycerol is used in medicine as a drug for the treatment of kidney edema or serves in the form of glycerol-containing suppositories as osmotic laxity in the rectum. Furthermore, the reaction with concentrated nitric acid and concentrated sulfuric acid produces nitroglycerin, a highly explosive that can be further processed into dynamite.

The material use of glycerine is currently limited to about 100,000 tons per year in Germany.

Due to political guidelines of the European Union and thus also of the German Federal Government, the use of biogenic fuels is promoted in Germany. According to the EU Biofuels Directive 2003/30 / EC, the share of biofuels in total fuel requirements (petrol and diesel fuel) is to be increased to 5.75% by the year 2010.

The current market situation for biofuels in Germany showed a biodiesel production of about 2 million tonnes by 2005. For 2006, an increase in capacity to about 3.2 million tonnes is planned. In biodiesel production, about 10% of glycerol accumulates, which must be recycled. The glycerol obtained in the production of biodiesel is obtained as a by-product according to the following formula scheme:

As mentioned above, the material use of glycerine in Germany is limited to about 100,000 tonnes / year and it is expected that the surplus of glycerine from biodiesel production can increase to up to 700,000 tonnes by the year 2010 The question is how this excess amount can be recycled.

It is therefore the task of exploiting the large surplus of glycerol arising from the production of biodiesel as efficiently as possible from an economic and ecological point of view.

Description of the invention

The stated object is achieved by using the glycerine obtained in the production of biodiesel as an additive or substitute fuel in combustion plants. The object is achieved in particular by the fact that glycerol as additive or substitute fuel in coal power plants, oil power plants, gas power plants or is burned in lignite-fired power plants, coal-fired power plants or gas / coal combined cycle power plants and thus used for energy production (eg heating or process heat, steam, electricity).

It is also conceivable, however, that the glycerol is burned in furnaces of cement plants, iron or steel works, waste or pollutant combustion plants or other industrial plants as additional or substitute fuel.

Furnace plants in which glycerol can be burned for energy production are e.g. the following burners or boiler / burner units: coal burners, oil burners, fluidized bed boiler burners, water tube boiler burners, shell boiler burners, rust-fired boiler burners, low-gas burners, duct burners and surface burners, and other similar types of burners.

It is conceivable that the abovementioned burners or boiler / burner units are used as so-called start-up burners or pilot burners, auxiliary burners or as power burners.

The use of glycerine as a fuel for energy production has several cost advantages, with several advantages resulting from energy policy or ecopolitical EU or country-specific legislation.

Incidentally, in the context of the present invention, the term "glycerol" is used synonymously for the terms glycerol, crude glycerol or biogenic glycerol or biogenic crude glycerol. Of course, this general definition does not apply if the term "glycerol" used here is specified in more detail in the respective context.

The term "oil" means both mineral oils and vegetable oils. Mineral oils included in the term "oil" are, for example, heavy heating oil, light heating oil and so-called middle oils. The term "oil burner" or "oil combustion system" accordingly all burners or furnaces, for which are provided as a rule fuel the above mineral oils or vegetable oils.

The term "substitute fuel" is to be understood as meaning all fuels which do not represent standard fuels for which the respective system is actually designed. Substitute fuels are e.g. also combustible waste, or processed high calorific waste fractions, in which the term secondary fuel has become established. If the glycerol is used in the context of the present invention as a mixture with one or more other fuels, is also used as a substitute fuel.

"Additional fuel" means all fuels that are burned together in a mixture with the so-called standard fuels for which the system is actually designed, wherein the additional fuel is mixed either with the standard fuels before being fed into the combustion chamber or with the additional fuel a combustion chamber, in which regular fuel is burned, is supplied. The additional fuel can be in the context of the present invention glycerol or a mixture of glycerol and one or more other fuels.

In this context, it should also be noted that, in the field of waste treatment, it is only known to date that waste, which may consist of paper, plastics, wood, textiles, meat-and-bone meal, animal fats or sewage sludge, can be treated as a substitute fuel in order to incinerate it for energy production. Since the expected due to the increasing production of biodiesel amount of the by-product glycerol so far was not a disposal problem, glycerine in the field of waste treatment or disposal has not yet been an issue. However, if biodiesel production increases strongly in the future as indicated above, this problem could become an issue. The present invention therefore has the further advantage that a solution is shown here, such as the expected future surplus production glycerol can be counteracted in an economically and ecologically sensible way by the by-product.

However, one problem with the burning of glycerin is that glycerin has a very high vapor pressure and, concomitantly, a very high flashpoint. Pure glycerol and crude glycerol, which contains about 80% by weight of glycerol, 14% by weight of water, 5% by weight of salts from the biodiesel production process and less than 0.1% by weight of methanol, can also be obtained by vigorous preheating , eg to 120 ° C, difficult to ignite, since the vapor pressure of glycerol in this preheating is about an order of magnitude smaller than HEL at ambient temperature (T = 20 ° C).

Another problem with pure glycerol or Rohglycerin is that for these glycerols no cold pumpability with standard heavy oil pumps (75 mm / s ² ) is possible, so that a reservoir heating is necessary.

In a particular embodiment of the invention, the problem of the serious flammability of glycerol is solved in that the glycerol is used in the form of mixtures with one or more other fuels, wherein the one or more other fuels, a flash point of less than 100 ° C, preferably from below 60 ° C, more preferably below 40 ° C, and more preferably below 20 ° C.

Since pure glycerin has a flash point of T = 177 ° C and crude glycerol due to a flash point depression by traces of methanol contained therein and due to the formation of azeotropic water / glycerol mixtures has a flash point of about 170 ° C, the mixture with one or more Fuels, which have a significantly lower flash point, in total to a flash point depression of the glycerol fuel mixture.

Depending on the nature of the selected further fuels and the proportion of these fuels in the glycerol fuel mixture, a flash point of the Mixture of below 80 ° C, preferably below 50 ° C, more preferably below 40 ° C, particularly preferably below 30 ° C can be achieved.

In order to solve the cold pumping problems of pure glycerol or crude glycerol, in another aspect of the invention, the glycerol is mixed with such another fuel or fuels that the resulting mixture at 20 ° C has a viscosity of less than 200 mm / s ² , preferably less than 150 mm / s ² , more preferably less than 100 mm / s ² and most preferably less than 75 mm / s ² . Depending on the choice of the other fuels used in the glycerol fuel mixture both the above-mentioned objectives, namely lowering the flash point and lowering the viscosity of the glycerol fuel mixture can be achieved.

In a preferred embodiment of the invention, therefore, glycerol is used as an additive or substitute fuel in combustion plants, as glycerolmethanol or glycerol-ethanol mixture with a content of methanol or ethanol of 3 to 40 wt.%, Preferably from 5 to 30 % By weight and more preferably from 10 to 20% by weight.

Since the ethanol costs are much higher compared to the cost of the biogenic glycerol, it is desirable to mix the glycerol as low as possible, for example, ethanol or methanol. On the other hand, a higher proportion of methanol or ethanol lowers the flash point significantly further, so that a lighter flammability can be achieved. Furthermore, a higher proportion of methanol or ethanol also leads to a reduction in the viscosity of the mixture, which leads to an improved cold pumpability of the glycerol fuel mixture. A consideration of the respective advantages and disadvantages of a high or low proportion of admixed methanol or ethanol, it has been found that a proportion of 10 to 20 wt.% Methanol or ethanol is a good compromise to meet both the technical requirements, which are to be placed on an additional or substitute fuel, as well as cost to obtain an additional or substitute fuel, the cost advantage of Glycerine is not consumed by the higher cost of further fuel.

In a particularly preferred embodiment of the invention, a mixture of 10 to 20 wt.% Ethanol and crude glycerol is used as a substitute fuel for light fuel oil as a so-called ignition oil in lignite power plants.

In a further particularly preferred embodiment, a mixture of glycerol with 5 to 15 wt.% Ethanol is used as a substitute fuel in heavy oil burners. According to this embodiment, the regular fuel in said heavy oil burners may e.g. also a renewable fuel, e.g. Be palm oil.

In a further particular embodiment, the glycerol or crude glycerol without ethanol or other fuel additive or, alternatively, the mixture of glycerol and the other fuel (s) via an injection pipe or a burner in the hot flame area of the combustion chamber of combustion plants and power plants for the Use of liquid, solid and gaseous fuels and thus be used as additional fuel. In this case, the flame region into which the crude glycerol is injected, must have a temperature of the ignition temperature of the glycerol (400 ° C), so that an ignition of the glycerol takes place.

In yet another particular embodiment, the glycerol or the crude glycerol can be used as additional fuel in oil firing systems. In this case, for example, a mixture of glycerol and heavy oil is burned in a heavy oil combustion plants and used to generate energy. An alternative embodiment may also provide that a mixture of glycerine, another fuel and, for example, heavy fuel oil is used in an oil-fired plant to generate energy. In this case, the further fuel, for example methanol and / or ethanol, serves to adjust the flash point and / or the viscosity of the glycerol / heavy oil mixture.

In a further embodiment of the invention, the injection of the crude glycerol can also take place temporarily in a coal boiler in order to be able to quickly achieve an increase in output at peak load times.

Examples viscosity

The viscosity of the crude glycerol (80% glycerol, 14% water) is 152 mm / s ² at 20 ° C and is thus about 8 times lower than that of pure glycerol with 1176 mm / s ² . The high viscosity reduction is produced by the 14%, low-viscosity water content. Thus, the crude glycerine already generally shows a much better opportunity to use this in a fuel oil burner. The cold pumpability of the crude glycerin is still limited, as some HEL oil burner pumps can only deliver up to a viscosity range of 75 mm / s ² . By changing to a light / medium oil pump (maximum 200 mm / s ² ) this problem can be solved. The addition of 20% by weight of low-viscosity ethanol to the crude glycerol leads to a further significant reduction in the viscosity for the blend GE20 (crude glycerol with a 20% strength by weight ethanol). Here the cold pumpability for the blend is achieved with a HEL oil burner pump ( illustration 1 ), wherein the viscosity at 20 ° C by the 20% addition of ethanol is reduced by about 50%.

vapor pressure

The vapor pressure of the crude glycerine (G0) in the lower temperature range (T = 20 ° C) is approximately at the same level as that of HEL. It is almost entirely due to the water contained. With increasing temperature (T = 50 ° C) this is already significantly higher, namely by a factor of 2, than that of HEL. The reason for this will be the approximately 14% water in the crude glycerol, which accounts for a significant proportion of the total vapor pressure at these temperatures is. The vapor pressure of pure glycerol is so minimal that it plays no role in the evaporation of crude glycerol (G0) up to 100 ° C.

It can be seen that the intermolecular forces between the water and the glycerine lead to a reduction of the water vapor pressure in the crude glycerine, since it is significantly lower than that of pure water ( Figure 2 ).

The evaporation of pure glycerol shows at maximum oil preheating temperature of T = 125 ° C a vapor pressure P of only 0.13 kPa. This is even more than an order of magnitude lower than the vapor pressure for HEL (P = 1.9 kPa) at a temperature of 30 ° C. This shows that even with a strong oil preheating a very small proportion of glycerine fuel vapor is generated. Thus, under these conditions, the pure glycerol can be ignited only badly in the burner. Further heating of the fuel is not possible, since the chemical decomposition of glycerol begins at a temperature of 130 ° C. ( Figure 3 ).

The comparison of the vapor pressure of glycerin (pure) to crude glycerine (G0) shows that the water content of about 14% contributes to the strong increase in vapor pressure. The water vapor content can only be seen as an inert mass.

The comparison of crude glycerol (G0) to the crude glycerol-ethanol blend GE20 shows at low temperature (T = 20 ° C) an increase in the vapor pressure by about P = 3.8 kPa. Thus, the increase in vapor pressure is approximately twice the vapor pressure (P = 1.8 kPa) of HEL at T = 20 ° C. Thus, the addition of 20% ethanol produces a sufficient fuel vapor fraction which allows ignition of the GE20 blend without preheating. The increase in vapor pressure is significantly increased with increasing temperature. Thus, with a preheating of T = 30 to 40 ° C or higher in any case an ignitable fuel vapor can be formed, since the total vapor pressure of HEL at T = 50 ° C (P HEL = 2.5 kPa) and at T = 100 ° C (P HEL = 7.2 kPa) is significantly lower than the increase in vapor pressure due to the 20% addition of ethanol to the crude glycerin.

Flash point

The flash point of pure glycerol is T = 177 ° C. The crude glycerine has a flashpoint T = 170 ° C ( Figure 4 ). The low flash point depression is produced by traces of ethanol (<0.1%) and the formation of azeotropic mixtures of water / glycerol. The water lowers the boiling point of the mixture.

The addition of 20% ethanol lowers the flash point of the blend GE20 up to 31 ° C. This is consistent with the high vapor pressure values found for the GE20 blend. Due to the admixture, the flashpoint is lowered to the hazard class All to VbF and is well below the flashpoint of HEL, so that for all blends a good cold start behavior can be achieved in the burner.

A balance sheet analysis ( Figure 5 ) for the blend GE20 shows that starting from a preheat temperature of 100 ° C for steam heating (0.052 MJ / kg), glycerine heating (0.904 MJ / kg) and glycerol evaporation (0.668 MJ / kg) to 290 ° C an energy of 1 , 62 MJ / kg is consumed.

To the blend GE20 is provided a more than sufficient amount of energy (5.53 MJ / kg) for the evaporation zone at 100 ° C preheat temperature, so that a burner can safely run stationary.

Claims (14)

Use of glycerine as additive or substitute fuel in combustion plants. Use according to claim 1, wherein the furnaces are operated in coal power plants, oil power plants, gas power plants, cement plants, iron and steel works, waste incineration plants or other industrial plants or for the production of heating or process heat. Use according to claim 2, wherein the furnaces are operated in particular in lignite power plants, hard coal power plants, gas / coal combined cycle power plants or heavy oil power plants. Use according to any one of the preceding claims, wherein the furnace is a burner / boiler unit selected from the group consisting of coal burners, oil burners, fluidized bed boiler burners, water tube burners, shell fired boiler burners, burners fired by a furnace, low pressure burners, duct burners, surface burners includes. Use according to claim 4, wherein the burner or the boiler / burner unit is used as a starter burner, auxiliary burner or as a power burner. Use according to one of the preceding claims, wherein the glycerol is used alone or in the form of mixtures with one or more other fuels, wherein the fuel (s) further below a flashpoint of below 100 ° C, preferably below 60 ° C, more preferably below 40 ° C and more preferably below 20 ° C. Use according to claim 6, wherein the mixture of glycerol and the one or more other fuels has a flash point of less than 80 ° C, preferably less than 50 ° C, more preferably less than 40 ° C and most preferably less than 30 ° C. Use according to claim 6 or 7, wherein the viscosity of the mixture of glycerol and the one or more other fuels at 20 ° C below 200 mm / s ² , preferably below 150 mm / s ² , more preferably below 100 mm / s ² and most preferably less than 75 mm / s ² . Use according to one of claims 6 to 8, wherein the glycerol / fuel mixture comprises a glycerol / methanol or glycerol / ethanol mixture with a proportion of methanol or ethanol of from 3 to 40% by weight, preferably from 5 to 30% by weight .-% and particularly preferably from 10 to 20 wt .-% is. Use according to claim 9, wherein the glycerine / fuel mixture is used as ignition oil in coal combustion plants. Use according to claim 9, wherein the glycerin / fuel mixture is used as a substitute fuel in oil firing installations, especially in heavy oil burners, for power generation. Use according to any one of claims 1 to 9, wherein the glycerol is used as an additive fuel in oil firing systems, in particular in heavy oil firing systems. Use according to claim 12, wherein additionally another fuel, in particular methanol and / or ethanol, is contained in the mixture for controlling the flash point and / or the viscosity in the glycerol / fuel mixture. Use according to one of claims 1 to 9, wherein the glycerol or the mixture of glycerol and the one or more other fuels is used as additional fuel and is injected via an injection pipe or a burner in the hot flame region of the combustion chamber of the furnace.

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