METHOD FOR ANALYSIS OF THE OPERATION AND OPTIMIZATION OF WASTE INCINERATION PLANTS

Description

[0001] The invention relates to a method for analyzing the operation and optimizing the operation of waste incineration plants according to the preambles of claims 1 and 2.

[0002] From EP 1 698 827 it is known to determine the CO 2 content of the exhaust gas of, for example, a waste incineration plant in order to infer the "combustion intensity" and, if a certain level is exceeded, to regulate the ratio of the oxygen mass flows of primary combustion gas and secondary combustion gas so that it falls below this level again.

[0003] From EP 1 715 339 of the applicant, it is known that, in order to determine the proportions of biogenic and fossil energy carriers in a waste incineration plant, the comparison of at least three balances, selected from eight balances, is mandatory. This method is very accurate, but requires a certain amount of equipment and procedural effort.

[0004] As the name suggests, waste incineration plants burn waste, producing a fuel with a very heterogeneous composition, particularly a fluctuating ratio of biogenic waste components to fossil waste components, which also include all types of plastics. Each waste incineration plant is designed for a ratio of these two components predicted through analysis and achieves its best operating results when this ratio is maintained.Due to the completely erratic feed of waste, even when, based on experience, the aim is to achieve the most uniform mixing possible during the filling and circulation of the waste in the bunker from which the combustion chamber of the waste incineration plant receives its fuel, undesirable changes in the fuel composition in the combustion chamber occur over time. These changes affect the combustion process, the energy gained (converted), and also the exhaust gas properties, where these changes can best be manifested.

[0005] It should also be noted that there is no precisely defined ratio of biogenic to fossil carbon as a design parameter for waste incineration plants. Operating the plant with a constant, different ratio of biogenic to fossil is also not a problem from an operational perspective. What is problematic are short-term changes in the fuel composition.

[0006] For almost all types of fossil fuels, based on stoichiometric air supply (i.e., 0% oxygen by volume in the exhaust gas), the resulting CO₂ content is between 15 and 17.6% by volume, if natural gas and methane, which are hardly present in waste incineration (with the exception of auxiliary fuels), are disregarded. In comparison, typical biogenic fuels yield a CO₂ content in the exhaust gas (with stoichiometric air supply) between 19.1% (kitchen waste) and 21% by volume (cellulose), as can be seen in Table 1 below.

[0007] Differences in waste composition and the resulting fluctuations over time due to random feeding are therefore undesirable because waste incineration plants are also typically used for energy generation (actually conversion), and for this purpose, a consistent amount of steam (with constant temperature and pressure) per hour should be produced. In current technology, this is partially achieved through automated or manually controlled mixing of the delivered waste in the waste bunker using the bunker crane (see Fig. 3 - left illustration), in extreme cases by supplying heating oil or natural gas to maintain sufficient energy conversion or by accepting losses through partial utilization of the plant.

[0008] Existing measurements and studies at various plants show that, in a waste incineration plant with an annual capacity of 200,000 tons, particularly short-term fluctuations in the composition of the fuel supplied result in losses of between €200,000 and €500,000, or must be incurred due to the additional fuels (usually natural gas or heating oil). This not only represents a significant amount per plant, but also becomes a considerable economic factor due to the fact that there are approximately 400 waste incineration plants of this size in Europe.

[0009] The aim and purpose of the invention is to provide a method of the type mentioned above with which variations in operation can be reduced.

[0010] According to the invention, this is done alternatively or cumulatively by: A method for analyzing the operation of waste incineration plants, wherein the CO₂ content in the exhaust gas is measured and, after conversion to the CO₂ reference value, the ratio of biogenic to fossil carbon in the incinerated waste is determined, and the variability of CO₂ reference value or the ratio of biogenic to fossil carbon in the incinerated waste is determined and recorded with respect to magnitude and duration. A method for optimizing the operation of waste incineration plants, wherein the CO₂ content in the exhaust gas is measured and, after conversion to the CO₂ reference value, the ratio of biogenic to fossil carbon in the incinerated waste is determined, and the variability of CO₂ reference value or the ratio of biogenic to fossil carbon in the incinerated waste is determined with respect to magnitude and duration and used to select the waste to be incinerated.A method for optimizing the operation of waste incineration plants, wherein the CO2 content in the exhaust gas is measured and, after conversion to the CO2 reference value, the ratio of biogenic to fossil carbon in the incinerated waste is determined, and the variability of the CO2 reference value or the ratio of biogenic to fossil carbon in the incinerated waste is determined with respect to magnitude and duration and used for mixing the waste stored in the receiving bunker.

[0011] The invention is described in more detail below with reference to the drawing. The drawing(s) show(s). the Fig. 1 the relationship between exhaust gas composition and fuel composition with regard to biogenic and fossil material, the Fig. 2 An example of a real-time analysis of the composition of the waste input, which Fig. 3 The effect of the mixing optimized according to the invention is shown in two schematic representations. Fig. 4a and Fig. 4ban analysis of the variability of the fuel composition of two waste incineration plants, which Fig. 5a and Fig. 5b the average consumption of additional fuel (using heating oil as an example) and the average steam production of a waste incineration plant, each depending on the variability of the fuel composition Fig. 6a and Fig. 6b the average waste throughput and the average O2 concentration in the exhaust gas of a waste incineration plant, each depending on the variability of the fuel composition.

[0012] Before discussing the individual illustrations in the drawing in more detail, the theoretical basis of the invention will be explained: The combustion of different fuels is associated with a characteristic exhaust gas composition (the O₂ and CO₂ content in the dry exhaust gas, which can be calculated from the measured content in the wet exhaust gas, but unlike the latter, is directly comparable and meaningful). This composition depends not only on the chemical composition of the fuel (content of water, C, H, O, N, S, F, Cl, etc.) but also on the amount of combustion air. For example, a higher amount of combustion air with a particular fuel leads to a higher O₂ concentration and a lower CO₂ concentration in the exhaust gas.

[0013] By computationally normalizing the exhaust gas composition to a constant oxygen content in the exhaust gas (e.g. residual oxygen content of 0% at stoichiometric air requirement or constant air ratio), changes in the exhaust gas composition depend exclusively on the fuel or its chemical composition.

[0014] This standardization of the exhaust gas composition (to any oxygen content in the exhaust gas) O 2 Relation ) is done by the following well-known equation, which allows the dry exhaust gas composition to be calculated approximately for a constant oxygen content in the exhaust gas. CO 2 Bezug = CO 2 gemessen ⋅ 21 − O 2 Bezug 21 − O 2 gemessen CO 2 Relation CO 2 Concentration in dry exhaust gas at a constant (arbitrarily definable) air-fuel ratio or at O 2 Reference [Vol.-%] CO 2 measured measured CO 2 Concentration in the dry exhaust gas of the combustion plant [Vol.-%] O 2 measured Measured O2 concentration in the dry exhaust gas of the combustion plant [Vol.-%] O 2 Relation Arbitrarily definable (constant) oxygen content in the dry exhaust gas of the combustion plant (preferably a value of 0 vol.-% is chosen) [vol.-%] 21 stands for O2atm, the oxygen content of the atmosphere [Vol.-%]

[0015] For an exact calculation (taking into account the existing CO2 content in the combustion air or in the atmosphere) of the standardized CO2 concentration CO 2 Relation in dry exhaust gas at a constant (arbitrarily definable) air-fuel ratio or at O 2 Relation- The following formula should be used, whereby significant differences between the results of the approximate formula and the exact formula only occur at higher air-fuel ratios. CO 2 Bezug = CO 2 gemessen − CO 2 atm ⋅ 100 % − CO 2 gemesen − O 2 gemesen 100 % − O 2 atm − CO 2 atm ⋅ O 2 atm − O 2 Bezug O 2 atm − O 2 gemessen + CO 2 atm ⋅ ⋅ 100 % − CO 2 gemessen − CO 2 atm ⋅ 100 % − CO 2 gemesen − O 2 gemesen 100 % − O 2 atm − CO 2 atm ⋅ ⋅ O 2 atm − O 2 Bezug O 2 atm − O 2 gemessen O 2 ATM O2 concentration in the combustion air or in the atmosphere [vol.%], typically this is around 20.94 vol.% CO 2 ATM CO 2 Concentration in the combustion air or in the atmosphere [vol.%], typically this is around 0.04 vol.%

[0016] The dry exhaust gas composition CO2 reference and O2 reference, normalized to a constant oxygen content in the exhaust gas, depends, as mentioned above, exclusively on the fuel or its chemical composition.

[0017] Temporal variations in the (normalized) dry exhaust gas composition (CO2 content) based on a constant oxygen content O2Reference are therefore the result of a fuel that has changed in composition over time.

[0018] Therefore, in waste incineration plants, the temporal variation of CO₂ reference can be used to infer the homogeneity or mixing of the waste input. A nearly constant CO₂ reference value indicates good mixing and a constant composition of the waste input, while (short-term) changes in CO₂ reference indicate a fluctuating waste composition (and thus insufficient mixing).

[0019] The temporal variation of CO2 intake allows for monitoring and thus control of the bunker waste mixing.

[0020] The aim of the waste incineration plant operator is to ensure the most constant possible (low fluctuations) composition of the waste input, as this is the only way to guarantee optimal (energy-efficient) operation.

[0021] The following Table 1, already mentioned at the beginning, shows examples of normalized (referenced to 0 vol.-% oxygen) exhaust gas composition of different fuels, expressed by CO2 reference. Table 1: Fuel or waste O 2 reference [Vol.-%] CO2 reference [Vol.-%] Fossil fuels or waste natural gas 0 12 methane 0 11,8 Polyethylene 0 15,1 Polypropylen 0 15,1 PVC 0 17,2 polystyrene 0 17,6 Heating oil EL 0 15,6 Biogenic fuels or waste cellulose 0 21 Wood 0 20,5 Paper & Cardboard 0 20,1 Garden waste 0 19,6 Kitchen waste 0 19,1

[0022] Table 1 above shows that biogenic fuels / waste have a higher CO₂ reference value compared to fossil fuels. This means that, in simplified terms, the standardized exhaust gas composition (expressed by CO₂ reference) can also be used to determine the proportion of biogenic or fossil materials in the input to waste incineration plants.

[0023] Use of the invention for evaluating plant operation taking into account waste mixing: The method according to the invention allows not only the current mixing / homogenization of the bunker waste to be monitored and controlled based on this (see Figs. 2 and 3 ), but the method is also suitable for retrospectively analyzing plant operation (with reference to the mixing / homogenization of the bunker waste) and quantifying the influence of insufficient mixing / homogenization of the waste on the operation.

[0024] For example, the proportion of operating hours with very good or poor mixing / homogenization of the bunker waste can be determined (see Fig. 4 By statistically evaluating (e.g., averaging) operationally relevant parameters of the waste incineration plant (e.g., steam production, waste throughput, oxygen content in the exhaust gas, consumption of additional fuels) for the respective different time periods (operating hours with very good, good, ... poor mixing / homogenization of the bunker waste), statements can then be made about the influence of the bunker waste mixing on the operation (see Figs. 5 and 6 This provides the plant operator with valuable information about the potential for optimizing their plant through better mixing / homogenization of the bunker waste.

[0025] The analyses for two waste incineration plants (plant A and B) show, for example, that better homogenization of the bunker waste is achieved at plant B, as the number of operating hours with low variability of the waste input (expressed by the standard deviation of the proportion of biogenic carbon over 4 h) is significantly higher (see Fig. 4 ).

[0026] The evaluations of the influence of the temporal variability of the bunker waste composition (expressed by the standard deviation of the biogenic carbon content over 4 hours) on plant operation show that for waste incineration plant A, with higher temporal variability of the waste composition (standard deviation of >5% of the biogenic carbon content: low mixing / homogenization of the bunker waste), the average consumption of heating oil increases (from approximately 0 to 220 kg / h), the average steam production of the plant decreases (from 106.2 t / h to 102 t / h), the average waste throughput decreases (from 29 t / h to 27.6 t / h), and at the same time the average oxygen concentration in the exhaust gas increases (from 7.5 vol.% to 8.05 vol.%). Figs. 5 and 6 All observed effects result in financial losses for the plant operator.

[0027] Using the method according to the invention, these losses can be quantified for the first time and specifically explained by the temporal variability of the composition of the waste input (mixing / homogenization of the bunker waste), and this practically in real time, which was not possible until now.

[0028] Use of the invention for determining biogenic and fossil energy carrier proportions as well as fossil and biogenic carbon dioxide emissions from the combustion plant: The method according to the invention is not only suitable for operational optimization but can also be used approximately for determining biogenic and fossil energy carrier proportions as well as fossil and biogenic carbon dioxide emissions from the combustion plant, for example using the Fig. 1 depicted context.

[0029] The Fig. 1The graph shows, as a dotted line and, taking possible deviations into account, as a gray stripe, the exhaust gas composition (expressed as the CO₂ reference concentration at stoichiometric air demand) versus the biomass content of the incinerated waste (carbon-related in g C bio / g C total); in mixtures with various fossil fuels. The following information is also provided: On the left edge, from top to bottom, some fossil fuels in BLACK: Circle: polystyrene, square: polyvinyl chloride, outlined square: typical mix of plastics in combustible waste (plastics mix), rectangle: heating oil, rhombus: polyamide, triangle: polyethylene and polypropylene; and on the right edge, from top to bottom, some biogenic fuels, in GREY: rhombus: cellulose, circle: wood, rectangle: paper & cardboard, outlined rhombus: typical mix of biogenic materials in combustible waste (biogenic mix), triangle: garden waste, square: kitchen waste, each at stoichiometric air demand.

[0030] The figures on the chemical composition of plastic mix or bio-mix originate from work carried out in connection with or following the aforementioned EP 1 715 339: "Method for determining the proportions of biogenic and fossil energy carriers".

[0031] This in Fig. 1 The presented direct correlation (inference) between CO₂ reference and biomass content is proposed, in particular, for the clearer communication of the results obtained (regarding the mixing and control of the waste in the incineration plant). It is easier for users of the invention, the operators of waste incineration plants, to visualize the temporal variability of the biomass content in the waste input than the fact that the variability of CO₂ reference already provides a direct indication of the variability of the waste composition.

[0032] The Fig. 2This shows an example of a high-resolution temporal analysis of the variability of the composition of the waste input (here measured by the standard deviation of the biomass content (carbon-related) including indication of those time periods (gray marked areas) in which the variability exceeds a defined measure (here the standard deviation of the biomass content over 40 min of 0.015 g C bio / C total) and thus leaves the range of optimal operation for the plant in question.

[0033] In these cases, a more intensive or targeted mixing of the bunker waste is required to ensure optimal operation (max. energy efficiency, max. waste throughput and max. steam production of the waste incineration plant).

[0034] Legend: Dashed line: measured O₂ concentration in dry exhaust gas; dotted line: measured CO₂ concentration in dry exhaust gas; black line: calculated CO₂ concentration in dry exhaust gas at a reference oxygen content of 0 vol.%; grey line with dot markings: calculated biomass content of the fuel (carbon-related) C bio / C total; grey line: calculated standard deviation of the biomass content (carbon-related and exaggerated by a factor of 10).

[0035] The Fig. 3On the one hand, the current state of the art for the random mixing of bunker waste or the fed-in fuel without knowledge of the spatial distribution of the waste composition in the bunker (left figure) and on the other hand, the targeted and controlled mixing of bunker waste or the fed-in fuel made possible by the present invention with knowledge of the spatial distribution of the waste composition in the bunker (right figure), whereby the targeted and controlled mixing leads to a lower temporal variability of the fuel composition.

[0036] The Fig. 4 The figure shows in two representations an analysis of the short-term variability of the waste composition for 2 waste incineration plants (plant A and plant B), expressed by the standard deviation of the proportion of biogenic carbon over 4 h [in %] and the respective number of operating hours for which this variability in the composition was observed.

[0037] Legend: A standard deviation of the proportion of biogenic carbon of <0.5% (rightmost column) represents very good mixing of the bunker waste (low temporal variability), while a standard deviation of >5% (leftmost column) indicates poor mixing of the bunker waste (high temporal variability of the waste composition).

[0038] The Fig. 5 shows in two illustrations for the waste incineration plant A in Fig. 5a the average consumption of the additional fuel heating oil and in Fig. 5b The mean steam production as a function of the short-term variability (fluctuations) of the waste composition (expressed by the standard deviation of the proportion of biogenic carbon over 4 h).

[0039] Legend: A standard deviation of the proportion of biogenic carbon of <0.5% (rightmost column) represents very good mixing of the bunker waste (low temporal variability), while a standard deviation of >5% (leftmost column) indicates poor mixing of the bunker waste (high temporal variability of the waste composition).

[0040] The Fig. 6 shows, also in two representations for the waste incineration plant A in Fig. 6a the average waste throughput and in Fig. 6b the average oxygen concentration in the exhaust gas, again depending on the short-term variability (fluctuations) of the waste composition (expressed by the standard deviation of the proportion of biogenic carbon over 4 h).

[0041] Legend: A standard deviation of the proportion of biogenic carbon of <0.5% (rightmost column) represents very good mixing of the bunker waste (low temporal variability), while a standard deviation of >5% (leftmost column) indicates poor mixing of the bunker waste (high temporal variability of the waste composition).

[0042] In one embodiment of the invention, the point of extraction in the bunker for each scoop of material (quantity introduced into the combustion chamber) is recorded, which is made possible by the crane's control system. After a short time, characteristic of each system, the waste composition of the scoop in question affects the composition of the exhaust gases, thus quickly providing sufficiently accurate knowledge of the composition of the waste stored at the respective locations in the bunker. This knowledge is continuously updated by the temporal sequence of extractions and the geometric relationships, and quickly takes into account changes caused by newly introduced waste into the bunker.Therefore, unlike in the prior art, it is not necessary to make assumptions about the composition of the bunker waste when feeding it into the combustion chamber, but rather statistically reliable and constantly updated data on the distribution of the waste in the bunker and its composition is available, which can be used both for fuel feeding and for mixing the bunker waste.

[0043] This measure not only makes it possible to keep the fluctuations lower than in the state of the art, but also to compensate for them more quickly than is possible in the state of the art.

[0044] In summary, the invention relates to a method for analyzing the operation of waste incineration plants according to claim 1.

[0045] The invention also relates to a method for optimizing the operation of waste incineration plants according to claim 2.

[0046] Any combination of these methods is of course possible.

[0047] One design of these, possibly combined, procedures provides for: a) that in a preparation phase, the time from the introduction of a quantity of waste into the combustion chamber until its capture in the exhaust gas is determined; b) during operation, the location for the extraction of each quantity in the bunker is determined and stored; c) the effect of each quantity on the exhaust gas, and thus the ratio of biogenic to fossil carbon at that location in the bunker, is determined, taking into account the time determined in step a); d) taking into account the results from steps b) and c), the location in the bunker for the next extraction of a quantity is selected; e) taking into account the results from steps b) and c), the locations in the bunker for the mixing of the waste (capture of a quantity at one location and its dispersal at another location in the bunker) are selected.

[0048] In a further training course, it is planned that when new waste is introduced into the bunker, the location of the introduction is determined and stored, and until the first extraction of a quantity from this location, the ratio of biogenic to fossil carbon at this location in the bunker is stored as unknown.

[0049] In the description and claims, "essentially" means a deviation of up to 10% of the specified value, if physically possible, both downwards and upwards; otherwise, only in the sensible direction. For degree specifications (angle and temperature), this means ± 10°.

[0050] All quantities and proportions, especially those defining the scope of the invention, insofar as they do not relate to specific examples, are to be understood with a tolerance of ± 10%, thus, for example: 11% means: from 9.9% to 12.1%. In designations such as: "a solvent", the word "a" is not to be regarded as a numeral, but as an indefinite article or pronoun, unless the context indicates otherwise.

[0051] Unless otherwise specified, the term "combination" or "combinations" refers to all types of combinations, from two of the components in question to a multitude or all such components; the term "containing" also refers to "consisting of".

[0052] The features and variants specified in the individual designs and examples can be freely combined with those of the other examples and designs and used without necessarily including the other details of the respective design or example.

Claims

1. Method for analysing the operation of waste incineration plants, wherein the CO2 content in the exhaust gas is measured and, after conversion to the CO2reference the ratio of biogenic to fossil carbon in the incinerated waste is determined from it, and the variability of CO2reference or the ratio of biogenic to fossil carbon in the incinerated waste is determined and recorded according to magnitude and duration.

2. Method for optimising the operation of waste incineration plants, whereby the CO2 content in the exhaust gas is measured and, after conversion to the CO2Reference the ratio of biogenic to fossil carbon in the incinerated waste is determined from this, and the variability of CO2reference or the ratio of biogenic to fossil carbon in the incinerated waste is determined according to magnitude and duration and is used to select the waste to be fed into the incinerator and / or to mix the waste stored a the receiving bunker.

3. Method according to claim 2, wherein a) in a preparation phase, the time from the introduction of a quantity of waste into the combustion chamber to its detection in the exhaust gas is determined, b) during operation, the location of the removal of each quantity in the bunker is determined and stored, c) CO2reference or the ratio of biogenic to fossil carbon at this location in the bunker is determined by the effect of the quantity on the exhaust gas and stored, taking into account the time determined in step a), and d) considering steps b) and c) above, the location in the bunker for the next removal of a quantity is selected, and e) considering the locations in the bunker for mixing the waste by steps b) and c) (taking a quantum at one location and scattering it at another location in the bunker) are selected.

4. Method according to claim 3, wherein when new waste is introduced into the bunker, the location of introduction is determined and stored, that until the first removal of a quantity from this location, CO2reference or the ratio of biogenic to fossil carbon at this location in the bunker is stored as unknown, and that after the first removal of a quantity from this location, the ratio determined according to step c) is stored.