WO2018099888A1

WO2018099888A1 - Use of glycerine produced in particular during the production of bio-diesel

Info

Publication number: WO2018099888A1
Application number: PCT/EP2017/080605
Authority: WO
Inventors: Matthias ÜBLER
Original assignee: Siemens Aktiengesellschaft
Priority date: 2016-11-29
Filing date: 2017-11-28
Publication date: 2018-06-07
Also published as: DE102016223694A1

Abstract

The invention relates to the use of glycerine produced in particular during the production of bio-diesel in a bio-diesel refinery, as an energy storage material for storing heat and/or for providing electricity.

Description

description

Use of glycerol produced, in particular in the production of biodiesel

The invention relates to a use of an energy storage material. Due to its high specific heat capacity of more than 4J / gK in the liquid state, its low dynamic viscosity, its almost unlimited availability, its toxicological safety and non-flammability, water is the most widely used sensitive storage medium, both for private use and in the power plant and water industry District heating ^¬ technology.

Particularly in urban environments, the provision of sensible heat by means of hot water from the power plant complex to the consumers is realized almost exclusively by district heating. In this case, water, ideally heated to just below 100 ° C, the boiling point at ambient pressure in large-volume district heating tanks on the power plant side and kept for later use. It is also possible to store excess electricity from wind and photovoltaic systems or cheap night-time electricity there. About leads and local heat exchangers, the hot water is supplied to the consumer ^¬ chern under pressure and there unloaded, if necessary for a fee, for example for heating felt. In order to be able to store higher temperatures in the same tank geometry, district heating tanks with operating temperatures above 100 ° C. are also in use. Among other things, pressure tanks are used, which - as it were a pressure cooker - hold the internal pressure above the actual vapor pressure of the water. So the water remains above 100 ° C single-phase liquid. It is therefore particularly desirable that

To increase storage tank temperature in such storage tanks significantly, without having to change to the costly, pressure-designed tank designs. Recently, ThermoCline-related types have been used in which hot water with temperatures above 100 ° C is covered with water well below 100 ° C.

In this way, a pressureless design is possible, although the hot water with temperatures above 100 ° C at 1 bar pressure strives to go into the gaseous state. Due to the hydrostatic pressure of the layered, colder water column, the superheated water is kept as single-phase liquid and allows higher Einspeicheremperaturen than the unpressurized Speicherichert types with a maximum allowed 95-97 ° C water temperature, so-called two-zone storage tanks. An example of such a new gen- eration of storage tanks, for example, the established supply company from the local energy in Nuremberg and with 70m highest district heating storage Germany (March 2016) with a Fas ^¬ sungsvermögen of about 33,000 m ^ water in which net 1500 MW can be thermally injected and buffered. The hot water is heated to 113 ° C and prevented from evaporating with a 60-90 ° C cold water layer. Two electric heaters with a total output of 50 MW _e] _ _e ^ - | - _r i _s ch can surplus green electricity or available, renewable provided, electric power housed temporarily also be stored and so the power plant Release part ^¬ th This layering measure allowed. Accordingly, an increase of the Einspeicheremperatur by about 18-20 ° C compared to a conventional, pressureless district heating storage concept. At 113 ° C, water has a vapor pressure of about 1.25 bar, so the overcoated, colder water column must maintain this back pressure to prevent the hot water from evaporating. With this additional temperature delta of 20 Kelvin (from assumed 95 ° C to now 113 ° C final temperature), a still constant at about 4.2 J / gK assumed specific heat capacity and 33.000m3 water volume, this corresponds to about an additional storable energy of 75 MJ / m3 (approx. 21 kWh / m ^) and thus a total of approx. 700 MWh in terms of arithmetic Another solution, of course, is the use of pressure tanks that allow higher feed temperatures. However, pressure tanks are expensive to buy and the risk of hull failure, especially over long periods of operation, has led to an early departure from this type of district heating tank, so that practically only pressureless versions in the zone layer concept are built. The simplest solution for increasing the storage capacity is the construction of several pressureless storage tanks. Here it should be noted that, especially in urban environments, there is often a shortage of space, especially when cities have grown, but power plants are usually located on an area for a long time. The construction costs for the above district heating memory of the local energy provider in Nuremberg amounted, including the electric heater to approximately 16 million euros, with 1,200 tons of steel WUR installed ^¬. The storage capex is therefore about 10500

EUR / MWh _thermal .

Water is the medium of choice when it comes to the budget Spei ^¬ insurance and later providing heat at low temperatures. Since water but from 100 ° C a

Vapor pressure of one bar assumes, without technical measures, a significant increase in the storage temperature far above 100 ° C is not possible without finally having to use a pressure tank concept. Although the specific heat capacity of liquid water is one of the highest and technically exploitable on leichtesten property for a SpeI ^¬ cheranwendung, the specific gravity is relatively low at about 1000 kg / m ^3, so that the volumetric heat capacity of about 4.18 MJ / m ³ -K or about 1.2 kWh / m ³ -K. It is the object of the invention to provide a storage medium with an energy quantity which can be stored in comparison to water, which can be stored at the same volume and temperature with low spontaneous ignition, flammability, self-storage. tender combustibility, dynamic viscosity and ^{insbesonde ¬} re good heat transfer coefficient provide. The storage medium should be easily and inexpensively manufactured.

It is proposed to use glycerin simply and effectively as an intermediate energy store for subsequent heat and / or power generation. [1] discloses a process for producing biodiesel.

With glycerol a liquid storage material is used that has, compared to similar water volumetric Wärmekapa ^¬ capacity and almost comparable Eigenschaftskennwerte- portfolio such as water.

Glycerin is particularly advantageous in terms of

low dynamic viscosity,

- High specific gravity, high specific heat capacity or a large amount of specific product

Density and specific heat capacity,

high boiling point, much higher than 100 ° C or a low vapor pressure,

- good to very good availability with low, at best no or even negative price,

- Non-combustibility or flame retardancy and

Non-toxicity,

- No or low corrosivity compared to conventional

Steels as well

- thermal stability at high temperatures.

All unite these requirements in a material that seemed nearly impossible, especially in terms of volu ^¬ metric heat capacity, price, and thermal maximum temperature. However, it turns out that especially glycerol comes very close to these requirements. According to one aspect of the invention, the use of glycerol produced in particular in a biodiesel production of a biodiesel refinery as energy storage material for subsequent heat supply and / or current provision position is proposed.

Glycerin is a very long time known, well-studied material, so that all the thermo-physical characteristics ^¬ values are well known as a function of temperature. Thus, pure glycerol has a boiling point at ambient pressure of 290 ° C and a melting point of 18 ° C, with glycerol tends to be rather undercooled, than solidifies. The specific heat capacity in the temperature range of 20-200 ° C is 2.40-2.86 J / gK, with a specific gravity of 1.26-1.13 g / cm ^. Thus, the product of specific gravity and specific heat capacity of the glycerol of 20-200 ° C Tempe ^¬ raturabhängig 3.03-3.24 J / cm ^ -K and is, compared with that of water, in the temperature range of 20-99, 5 ° C with 4.18-4.04 J / cm ^ -K, although about 25% lower, but allows an increase in the storage temperature by up to 150 Kelvin, with continued pressureless operation. Glycerine is a biocompatible and regenerative source of organic liquid sugar, non-toxic and has a flashpoint of 177-190 ° C - the lowest temperature at which outgassing volatiles can be ignited by an external flame without inflammation Removal of self burns - a focal point of 204 ° C (lowest temperature at which a single, external inflammation on ^¬ independently burns) and an autoignition temperature of 430-530 ° C, depending on the substrate, or 412 ° C in pure oxygen at 1 bar. Glycerin is therefore considered non-combustible. The dynamic visco ^¬ sity pure glycerol is similar to water below 110 ° C in the setting information ^¬ gen mPa.s area and thus by definition. Crude glycerol from the global biodiesel production is a very affordable, often free waste product, try to give the Bio ^¬ diesel manufacturers. As biodiesel production will increase worldwide and over the long term and Making ne vast number of companies B biodiesel from under ^¬ schiedlichsten natural oil sources, it makes sense under consideration of the purity of the crude glycerol and Prei ^¬ ses or even negative price strategically promising swell and to be selected. In this case, the provision of particularly clean raw glycerine by the biodiesel manufacturer is a classic win-win situation.

Crude glycerol is per se a toxicologically harmless and available in large quantities, liquid at room temperature

Material. It shows a higher dynami ^¬ specific viscosity compared to water, but it allows you to start from be ^¬ pointing higher Einspeichertemperaturen up to 200-250 ° C in an unpressurized tank design with prevailing viscosities digit mPa.s area; I behave like water there. Although the mathematical product of temperaturabhängi ^¬ ger, specific heat capacity and specific gravity, called the volumetric heat capacity is approximately 25% as compared to water less, but this is more than compensated by the GroE ßere temperature delta.

Further advantageous embodiments are claimed with the subclaims. According to an advantageous embodiment, the glycerol can be heated by means of an electrical heater operated with regenerative electrical, in particular excess, power and used, in particular, as a heat storage fluid or as a heat transfer fluid for heat storage.

The use of this especially abundant Rohglycerins from biodiesel production as a cheap or free and highly heatable, thermal Energiespei ^¬ chermaterial - in English Thermal Energy Storage - TES - in the sense of "Power-2-Heat" for a later Wärmeverfügbar ^¬ speed ( Dispatchability), for example as Fernwärmeüberträ- gerfluid, is an application scenario of this invention. Analogous to water in district heating stores, surplus eco- Ström by means of electric heater energetic entry into the storage material possible. This concerns the concept Power-2-Heat. According to a further advantageous embodiment, for

Provision of electricity, the stored heat of the heated glycerol, in particular by means of an organic Rankine cycle, back-converted. Thus it is equally mög ^¬ Lich, instead of heat supply alone as the eingespei--assured heat rückzuverstromen again. This concerns the so-called Power-2-Heat-2-Power concept.

Thus, the concept of Power-2-Heat-2-Power, that is, the eventual subsequent reconversion of heat, in particular excess green power capacities, is another application scenario of this invention.

According to a further advantageous embodiment, the glycerol can be heated and / or cooled in combination with phase change materials in order to provide heat. Thus, a further possibility for significantly increasing the storable energy is a combination of the sensitive, thermal loading and unloading of the glycerol with phase change materials, so-called PCMs. In this case, materials that perform a phase change at a defined temperature, for example, when melting or solidification, encapsulated, in particular in the configuration of balls, tubes, cartridges, barrels, are in contact with the glycerol. If the glycerol in the storage tank is heated steadily during charging and passes through the melting temperature of the PCM material in contact therewith, the temperature remains constant until all PCM material has liquefied. When Entla ^¬ the is when passing through the solidification temperature of the PCM material, which preferably solidifies without significant supercooling in relation to the melting temperature, as well as kept the tempera ^¬ temperature and delivered the stored enthalpy of fusion to the glycerol in contact. In this way, not only one or more distinct ^ones can Constant temperature phases in the tank during charging and discharging realized, but the stored total energy are also significantly increased. Usually another to ^¬ wax to 100-200 kJ / kg PCM material is possible.

That this is tech ^¬ cally easy to carry out as well for relatively low temperature levels, for example, show

Geothermal power plants with energy recovery using ORC turbines in France. There, water is extracted from a depth of almost 5 km at a temperature of 175 ° C and emitted by isobutane as a working medium in an ORC cycle. By such low-temperature ORC systems and with glycerol as a thermal energy storage material, it is possible surplus ^¬ stream that can not otherwise be fed into the power grid or in weddings no electrical consumers, as heat to store between and back later when needed again. Disadvantages are the low efficiencies, so that such a storage chain can only be used for buffering non-storable, green energy surpluses and / or energy peaks.

According to a further advantageous embodiment, the phase change material used may be an organic material, in particular paraffin, wax, dimensionally stable HDPE, trans polybutadiene and / or inorganic material, in particular salt hydrates, anhydrous salt, a salt mixture.

According to a further advantageous embodiment, the glycerol may have been prepared in a phase-catalytic transesterification of fats and / or oils by means of methanol to Festsäuremethylestern as Rohglycerin.

The worldwide rapidly increasing and politically deliberate production of so-called biofuels for the extraction of fuels derived from fossil fuels is largely based on this base catalytic

Transesterification of fats and oils by means of methanol to solid acid ^¬ methylestern that are abbreviated in English with FAME or just be referred to as "biodiesel", and the side ^¬ product glycerol. This creates per ton biodiesel 100kg crude glycerol, for which there is no use and inevitably ^¬ fig other material cycles must be supplied. In 2012, around 20 million tonnes of biodiesel were produced worldwide, which corresponds to approximately two million tonnes of additional crude glycerine as a by-product. Due to the urgency of the disposal problem or due to the accompanying rapid decline in price of this additionally on the world market urgent glycerine several routes of re-use have emerged. Thus, a part of glycerol as a feed admixture, in particular for fattening pigs ^¬ used. Similarly, Escherichia coli bacteria are genetically engineered that metabolize the crude glycerol in other chemical see products, such as 1, 2-propanediol. Likewise, as additional fuel raw glycerol is burned in Kraftwerksan ^¬ plants and boilers. Ultimately, however, the world's increased production of biodiesel will lead to an enor ^¬ men oversupply of crude glycerol. Already in 2006, the raw glycerine from the biodiesel production in the US was traded at 0-70 US dollars, with a negative price outlook for the future, ie that producers of raw glycerine have to pay for the decrease of their glycerine. This results in an economic benefit for the proposed use of glycerol according to the invention.

According to a further advantageous embodiment, a proportion of water may have been removed from the crude glycerol. Mainly should be removed for proper use as a thermal energy storage of existing residual water content.

This can happen on the one hand in purification plants, but also once in the form of a pressure relief valve on the egg ^¬ tual storage tank by the storage tank contents including crude glycerol during commissioning once heated to 150-200 ° C and the residual water is expelled.

According to a further advantageous embodiment, the water content by heating to a temperature in a Temperature range of about 150 ° C to about 200 ° C are driven out of a storage tank via a pressure relief valve.

According to a further advantageous embodiment, the methanol and / or free fatty acids may have been removed from the crude glycerol. In the base catalyzed transesterification, the crude glycerol can be acidified and the resulting free fatty acids can be separated from the glycerol phase so that about 85% glycerol can be obtained, with trace element impurities, for example by phosphorus, sulfur and the like, depending on the oil, can be present in the double-digit ppm range, which, however, do not interfere with a thermal energy storage use. This unique and dehydrated crude glycerol from the Biodieselherstel- lung is the target material for the inventive USAGE ^¬ dung.

According to a further advantageous embodiment, alkali salts may have been removed from the crude glycerol. Since, due to the base-catalytic transesterification by means of alkali metal methoxides, for example potassium hydroxide dissolved in methanol, or the subsequent acidification for the separation of free fatty acids also alkali salts, they may be present in the crude glycerol to a small extent. The content of such in-situ prepared base catalyst is below 2

Wt .-% and thus extremely low in the crude glycerol present. However, separation is useful, although it is known from the scientific literature that with inorganic salts, such as potassium carbonate, enriched glycerol rin, and that goes hand in hand as a solid-free solution, not just a raised stabili ^¬ hung the specific density, but also the solidification temperature to well can be lowered below 18 ° C. These impurities therefore have a certain positive effect on the volumetric

Storage capability. However, alkali metal salts, insbesonde ^¬ re halides are preferred abge ^¬ separates in the context of corrosion tendency or sufficient corrosion resistant steels ver ^¬ turns should be. According to a further advantageous embodiment, the glycerol can be stored as a heat storage fluid in a pressureless 2-zone storage tank.

The invention will be described in more detail with reference to figures.

FIGS. 1 to 5 show comparisons of important physical parameters between water and glycerol.

FIG. 1 shows the specific gravity of glycerol and ^water as a function of temperature.

FIG. 2 shows a representation of the specific heat capacity of glycerol and water as a function of temperature.

FIG. 3 shows a representation of the dynamic viscosity of glycerol and water as a function of the temperature. shows a representation of the volumetric heat capacities of glycerol and water as a function of temperature. shows a representation of the vapor pressure of Glyce ^¬ rin and water as a function of temperature.

To take advantage of high Endspeichertemperaturen between water and glycerol at vapor pressures below a bar to verglei ^¬ chen (this corresponds to a conventional, pressureless tank design), serving a hypothetical, thermal loading of 60- 95 ° C for water, and a successive increase of Endtempe ^¬ temperature for glycerol up to 150 ° C, 200 ° C and 250 ° C, also starting at 60 ° C. The results are shown in the following Table 1. Storage capacity of water and glycerol at differing ^¬ chen Endspeichertemperaturen

As can be seen from Table 1, when glycerine is used as the thermal energy storage material with respect to water, with an increase in the final storage temperature of 9 Kelvin, an equivalent total energy of almost 1300 MW is thermal

storable: at 95 ° C, the vapor pressure of water is 0.84 bar, that of glycerol at 104 ° C only 0.0003 bar. With an increase in the final storage temperature to 150 ° C, 206% of energy can be stored with glycerin in an identical volume with respect to water, corresponding to 324% at 200 ° C. Up to this temperature, glycerin is certainly neither self-igniting, flammable nor self-sustaining flammable and the dynamic viscosity of 1-2 mPa-s is as low as water at 23 ° C. This allows excellent heat transfer, easy pumpability and thus rapid, thermal loading and unloading.

bibliography

[1] A. Singh, B. B. He, J.C. Thomson, J.H. van Gerpen, "Process Optimization of Biodiesel Production using Alkaline Catalysts"; Applied Engineering in Agriculture; Volume 22 (4): 597-600; 2006 American Society of Agriculture and Biological Engineers, ISN 0883-8542.

Claims

claims

1. Use of, in particular in a Biodieselherstel ^¬ ment produced a biodiesel ^refinery , glycerol as energy storage material for heat storage and / or StrombestStellung.

2. Use according to claim 1,

characterized in that

for heat storage, the glycerol is heated by a ^¬ with regenera tive electrical, in particular excess, power-driven electric heater and in particular as heat storage fluid, or as district heat carrier fluid is USAGE ^¬ det.

3. Use according to claim 2,

characterized in that

for the supply of electricity, the stored heat of the heated glycerol, in particular by means of an organic Rankine cycle, is reconverted.

4. Use according to claim 2,

characterized in that

for heating the glycerol is heated together with at least one phase change material and / or cooled.

5. Use according to claim 4,

characterized in that

As phase change materials organic materials, in particular paraffins, waxes, dimensionally stable HDPE, trans polybutadiene and / or inorganic materials, in particular salt hydrates, anhydrous salts, salt mixtures are used.

6. Use according to one of the preceding claims, characterized in that

the glycerol was prepared in a base-catalyzed transesterification of fats and / or oils by means of methanol to fatty acid methyl esters as Rohglycerin.

7. Use according to claim 6,

characterized in that

a proportion of water is removed from the crude glycerine.

8. Use according to claim 7,

characterized in that

the proportion of water is driven out of a storage tank by heating to a temperature in egg ^¬ nem temperature range of about 150 ° C to about 200 ° C via a pressure relief valve.

9. Use according to claim 6, 7 or 8,

characterized in that

were removed from the crude glycerol, the methanol and / or free fatty acids / was.

10. Use according to claim 6, 7, 8 or 9,

characterized in that

were removed from the crude glycerol alkali salts.

11. Use according to one of the preceding claims 2 to 10,

characterized in that

the glycerol is stored as a heat storage fluid in a pressureless two-zone storage tank.