WO2010057554A2

WO2010057554A2 - Method for operating a system for producing bioethanol

Info

Publication number: WO2010057554A2
Application number: PCT/EP2009/007466
Authority: WO
Inventors: Kersten Link; Uwe Neumann
Original assignee: Eisenmann Anlagenbau Gmbh & Co. Kg
Priority date: 2008-11-21
Filing date: 2009-10-17
Publication date: 2010-05-27
Also published as: RU2011124511A; US20110219993A1; WO2010057554A3; DE102008058501A1; BRPI0921003A2; DE102008058501B4; RU2508503C2; CN102216686A; EP2347182A2

Abstract

The invention relates to a method for operating a system (1) for producing bioethanol, wherein organic waste products of the production process, particularly DGS and DDGS, are combusted and the useful heat is fed back into the system (1) itself. The combustion process takes place in a fluidized bed oven (2). All areas (9, 11) in which the combustion process takes place have sufficient heat removed that the melting point of the ash of the waste product, particularly 70°C, is not exceeded at any point. In this manner, a fine-grained ash forms and largely mixes into the fluidized bed (9) and is easily disposed of. The useful heat is obtained partially from the flue gas arising from the combustion, and partially from the heat extracted from the combustion process for maintaining the maximum temperature.

Description

Process for operating a bioethanol production facility ================================

The invention relates to a method for operating a plant for the production of bioethanol, burned in the organic waste products of the manufacturing process, in particular DGS and DDGS, and the useful heat thus obtained the plant itself is fed back.

It is known in plants for the production of bioethanol, the organic waste products, which are produced in the form of vinasses but also in the form of dried granular products and are known in particular under the names DGS and DDGS, and burn the useful heat obtained in the plant to use again. This can be found, for example, the Internet lexicon WIKIPEDIA, as of October 2008, keyword "bioethanol". About the type of combustion process and the temperatures occurring in this reference is not found.

The currently most common types of disposal of DGS or DDGS are as animal feed, as fertilizer, as a substrate in biogas plants and combustion in biomass cogeneration plants. With these types of disposal, the organic waste products are transported from the site of the bioethanol plant to the disposal site.

The object of the present invention is to design a method of the type mentioned at the outset in such a way that, overall, a more rational operation of the would be possible for the production of bioethanol and a cost-saving disposal of organic waste products.

This object is achieved in that

a) the waste products are burned in a fluidized bed furnace and all rooms in which the combustion process takes place, so much heat is removed that at no point the melting temperature of the ash of the waste products, in particular 700 ⁰ C is exceeded;

b) the useful heat is recovered in part from the flue gases produced during combustion and partly from the heat extracted from the combustion process to maintain the maximum temperature.

The invention is based on that in the o. G. The "WIKIPEDIA" reference to finding the organic waste products from the bioethanol production process in another location instead of incinerating them on site and consuming the useful heat that has been generated in the plant itself. In a bioethanol manufacturing plant, there are many ways to use heat, either to produce steam or to heat plant parts or materials directly.

The invention goes beyond this known basic idea and proposes to carry out the combustion process in a fluidized bed furnace. If the combustion process is carried out in such a way that at no point does the melting temperature of the ashes of the waste products exceed th, falls to a fine-grained solid ash, which mixes into the fluidized bed and can be disposed of without problems. If heat were not removed from the combustion process as proposed by the invention, the temperature would rise to a value at which the resulting ash melts. However, liquid ash is much more difficult to dispose of than solid, fine-grained, as it arises in the process according to the invention.

The inventively proposed cooling of the combustion chamber to a temperature below the melting temperature of the ashes of the waste products is also associated with no significant loss of thermal efficiency, since the extracted heat is used as well as the heat contained in the flue gases themselves.

Due to the relatively low temperatures that prevail in the inventive method in the fluidized bed furnace, it is possible to dispense with a refractory lining of the housing of the fluidized bed furnace. This not only has significant cost advantages; due to the lower masses, the start-up and cooling of the fluidized bed furnace can be done much faster than existing brick lining.

As already indicated above, an advantageous embodiment of the method according to the invention is that the useful heat is used at least partially for the generation of steam.

To remove the heat from the combustion process, at least one heat exchanger can be used, which is flowed through by a heat transfer medium. The geometry and location of the heat exchanger or heat exchanger is selected according to the local conditions so that the goal of maintaining a maximum temperature in the combustion process is achieved.

The heat transfer medium can be water. This variant is particularly advantageous where a direct steam generation is desired.

Alternatively, the heat transfer medium may be a thermal oil. The heat is first removed from the combustion process via this thermal oil; the further utilization of this heat is then arbitrary.

For energetic reasons, it may be expedient if the air which is used to produce the fluidized bed, is preheated by the emerging from the fluidized bed furnace flue gases.

Waste products that would ignite when introduced above the fluidized bed, should in principle be introduced directly into the fluidized bed, so that they are distributed as evenly as possible and completely burned.

For waste products that do not ignite when placed above the fluidized bed, a case distinction is required: if they are designed to rise in the gas stream above the fluidized bed, they should also be placed directly into the fluidized bed. But are they such that they are in the

Gas stream fall above the fluidized bed, they should be introduced above the fluidized bed. In this choice of the place where the waste products are introduced, the best possible mixing and combustion of the waste products takes place. An embodiment of the invention will be explained in more detail with reference to the drawing; the single figure shows schematically a plant for carrying out the method according to the invention.

The plant designated overall by the reference numeral 1 comprises as the main component a fluidized-bed furnace 2, which is known in its basic structure. Its housing 3 is composed of three coaxial sections 3a, 3b, 3c, which are all rotationally symmetrical. The lowermost portion 3a is cylindrical; this is followed at the top by a conically widening section 3b, above which a re-cylindrical section 3c is finally mounted. The housing 3 is made of a high-temperature steel with a wall thickness of about 10 to 15 mm and is not provided with a refractory lining, as is generally the case with known fluidized bed furnaces of this type.

The lowermost portion 3a of the housing 3 is divided by a horizontal nozzle bottom 4 into two chambers. The lower chamber 4a serves as an air chamber. A fan 5 sucks for reasons explained below, either directly via a line 25 or via a heat exchanger

13 air from the outside atmosphere and introduces this in the air chamber 4a. A connected to the air chamber 4a burner 6 natural gas is supplied as combustion gas via a schematically indicated line 7 and combustion air 8.

In the upper chamber 4b and projecting into the section 3b of the housing 3, a fluidized bed 9 is provided, which consists of a granular, inert and temperature-resistant material, in particular sand. stands. Above the upper level of the fluidized bed 9, the waste product to be incinerated from bioethanol production, which may be DGS or DDGS, can be introduced into the interior of the housing 3 via a schematically represented line 10. This place of introduction is, according to the above, particularly suitable for those waste products which are comparatively moist and heavy and not easily flammable.

The lying above the fluidized bed 9 interior 11 of the housing 3 serves as a calming space. From it, the hot flue gases can be removed via a line 12 and fed via the heat exchanger 13 to a steam generator 14. The steam generator 14 may have any known construction, which need not be described in detail. In the steam generator 14 enters via a line 26 water; the desired end product of the process in the present case, namely hot steam, passes through a conduit

16 and via a line 16, the cooled flue gas, which can then be fed to a fireplace.

Both in the fluidized bed 9 and in the lying above the fluidized bed 9 free space 11 of the housing 3, heat exchangers 17, 18 are mounted. The heat exchangers 17, 18 may be of any shape, provided that they only do: they must be able to cover the entire combustion space of the housing 3, i. both from the

Fluidized bed 9 occupied space as well as the overlying free space 11, to cool during the combustion of the waste products to a temperature which is below the melting point of the ash of these waste products. This temperature must be reliably as constant as possible in the entire interior of the furnace 3 below. In the contemplated herein combustion of DGS or DDGS, this means that a temperature of about 650 ° to 700 ⁰ C at any point may be exceeded. The manner in which the heat exchangers 17, 18 must be designed for this purpose can be determined by simple experiments for the respective geometry of the fluidized bed furnace 2 and the respective waste products to be incinerated.

The heat exchangers 17, 18 are located in a heat transfer circuit, in which a thermal oil is kept in circulation by means of a pump 19. A circulation line 20 leads to this, starting from the pressure side of the pump 19, first via the heat exchanger 18 and then to the lower heat exchanger 17. From there, the thermal oil is further brought via the line 20 to a heat exchanger 21, which is housed within the steam generator 14 itself , there extracts heat from the thermal oil and this gives off to support the steam generation. Then the cooled thermal oil returns to the pump 19.

The plant 1 described above is operated as follows:

When starting the system 1, the first air chamber 4a is supplied with the aid of the fan 5 air, which is sucked in via the line 22 and either via the line 25 or via the heat exchanger 13 from the ambient air. Since at this time the heat exchanger 13 is still cold, the sucked air initially has ambient temperature in both cases.

The air blown into the air chamber 4 flows through the nozzle plate 4 and fluidizes the overlying bed of sand, so that the actual Fluidized bed 9 is formed.

With the help of the burner 6, via the lines 7 and

8 natural gas or combustion air is supplied, which is injected into the combustion chamber of the furnace 3 via the nozzle plate 4 air and thus the fluidized bed

9 heated to a temperature at which the now introduced via the line 10 waste product from bioethanol production begins to burn. If this waste product is sufficiently rich in energy, the operation of the burner 6 can be reduced or completely adjusted after this starting phase.

With the help of the heat exchanger 17, 18, through which the pump 19 pumps thermal oil, a temperature is maintained within the fluidized bed 9 and the overlying free space 11 in the manner already described above, which is below the melting temperature of the ash of the waste product.

This means that solid, fine-grained and free-flowing ash in the fluidized bed 9 accumulates over time. The height of the fluidized bed 9 therefore increases during operation. By measuring the pressure drop at the fluidized bed 9 by means of suitable sensors, it is determined when the fluidized bed 9 has reached a certain height, which should not be exceeded. Then 9 material discharged from the fluidized bed 9, which consists of a mixture of ash and sand by a suitable discharge mechanism, not shown via the line 27. If desired, this mixture can be separated again in a manner not described in more detail here, so that the ash can be disposed of and, if necessary, the sand can be returned to the fluidized bed 9. The fluidized bed furnace 2 leaving via the line 12 flue gases can still lead to ash particles in relatively small proportions. These may possibly be removed by a lying in the line 12, but not shown in the drawing cyclone from the hot flue gases. The latter pass through the heat exchanger 13 and now preheat the air, which is sucked via the line 22 from the fan 5 and into the air chamber 4a of the

Fluidized bed furnace 2 is blown. On the way forward, the flue gases reach the steam generator 14, where they are cooled to produce steam, which exits via the line 15, so that they can be discharged as a relatively cool flue gases via the line 16 into the outside atmosphere.

The heat which originates from the combustion process and is removed from the fluidized-bed furnace 2 by the heat exchangers 17, 18 is brought via the circulation line 20 into the heat exchanger 21 within the steam generator 14. There she contributes to steam generation.

Claims

Claims ==============

1. A method for operating a plant for producing bioethanol, in which organic waste products of the production process, in particular DGS and DDGS, are burned and the useful heat thus obtained is returned to the plant itself,

characterized in that

a) the waste products in a fluidized bed furnace (2) are burned and all rooms (9, 11), in which the combustion process takes place, so much heat is removed that at any point the melting temperature of the ash of the waste products, in particular 700 ⁰ C. , is exceeded;

b) the useful heat is recovered in part from the flue gases produced during combustion and partly from the heat withdrawn from the combustion process to maintain the maximum temperature.

2. The method according to claim 1, characterized in that the useful heat is used at least partially for the production of steam.

3. The method according to claim 1 or 2, characterized in that for removing the heat from the combustion process at least one heat exchanger (17, 18) is used, which is flowed through by a heat transfer medium.

4. The method according to claim 3, characterized in that the heat transfer medium is water.

5. The method according to claim 3, characterized in that the heat transfer medium is a thermal oil.

6. The method according to any one of the preceding claims, characterized in that the air, which for

Production of the fluidized bed (9) is used, is preheated by the emerging from the fluidized bed furnace (2) flue gases.

7. The method according to any one of the preceding claims, characterized gekennnzeichnet that waste products that would ignite during introduction above the fluidized bed (9), are introduced directly into the fluidized bed (9).

8. The method according to any one of claims 1 to 6, characterized in that waste products that would not ignite when ^• introducing above the fluidized bed (9) and which are such that they would ascend in the gas stream above the fluidized bed (9), be introduced directly into the fluidized bed (9).

9. The method according to any one of claims 1 to 6, characterized in that waste products which do not ignite when introduced above the fluidized bed (9) and which are such that they descend in the gas stream above the fluidized bed (9), above the fluidized bed (9).