Method for controlling an installation for producing mechanical work

Abstract

The invention relates to a method for controlling an installation (1) for producing mechanical work, wherein the installation (1) has an internal combustion engine (2), an exhaust-gas cleaning device (3) comprising a gas washer (4) and a washing-water cleaning installation comprising a first cleaning stage with a centrifugal separator (8), said method comprising the following steps: i) cleaning exhaust gas (X1) produced by the internal combustion engine (2), thereby providing contaminated washing water (X2); ii) cleaning the washing water (X2) using the centrifugal separator (8), thereby providing several phases (X4, X5, X6), wherein one of these phases (X4, X5, X6) comprises a cleaned washing water (X2) with a lower particle content compared to that of the supplied contaminated washing water (X2); iii) determining at least one measurement value (T1, T2, T3) which is dependent on the composition of at least one of the phases (X4, X5, X6) iv) setting the operation of the internal combustion engine (2) based on this determined measurement value (T1, T2, T3).

Description

[0001] METHOD FOR CONTROLLING A PLANT FOR GENERATING MECHANICAL WORK

[0002] The present invention relates to a method for controlling a plant for generating mechanical energy by analyzing a centrifugally separated fraction of contaminated wash water from an exhaust gas purification device. The method is particularly applicable on ships.

[0003] In shipping, the importance of exhaust gas purification systems with so-called wet scrubbers is increasing. Due to limited storage capacity, the resulting scrubber fluids must be cleaned and / or reused multiple times.

[0004] There are known processes in which scrubber fluids are fed into an open loop within an exhaust gas purification system. Measuring the PAH (polyaromatic hydrocarbon) content is used to determine whether the treated scrubber water can be disposed of overboard. In the open loop, pH, turbidity, and temperature are also monitored.

[0005] Closed circuits are also known in which the oil-in-water content and turbidity are measured. To date, no conclusions have been drawn from such measurements regarding the combustion efficiency of the internal combustion engine.

[0006] Based on this approach, measurements were initially conducted to determine the optimal operating point for combustion directly in the exhaust gas. While these are technically feasible, they are very complex. For example, sophisticated measurement systems exist for SOx and NOx. The levels of unburned fuel, lubricating oil, soot, and / or ash are not monitored or determined.

[0007] Based on the aforementioned prior art, the object of the present invention is to provide a method that allows for the reliable setting of an optimal operating point for combustion. This operating point can change, among other things, due to increased fuel consumption and a change in fuel type.

[0008] The present invention solves this problem by providing a method having the features of claim 1. A method according to the invention serves to control a system for generating mechanical energy. The mechanical energy can be used, for example, to operate a ship's propulsion system, e.g., a propeller.

[0009] The system comprises an internal combustion engine, e.g., an internal combustion engine, and an exhaust gas purification device comprising a gas scrubber and a scrubbing water purification system for purifying the contaminated scrubbing water produced by the gas scrubber. The scrubbing water purification system comprises a first purification stage with a centrifugal separator. The gas scrubber can also be located within an exhaust gas recirculation system.

[0010] The process is characterized by the following steps:

[0011] In a first step i), the exhaust gas generated by the internal combustion engine is cleaned by providing contaminated scrubbing water. This takes place in the exhaust gas cleaning device, in particular in the gas scrubber designed as a wet scrubber. Scrub water is used as the gas scrubbing medium.

[0012] In a second step ii), the contaminated wash water is purified by the centrifugal separator, providing several phases, one of which is purified wash water with a lower particle content than the contaminated wash water supplied.

[0013] This means that the purified wash water is less contaminated than the incoming wash water. However, it is not pure. In particular, small particles below a certain size cannot be completely removed by the centrifugal separator.

[0014] This aspect, i.e. the remaining particles and their concentration, are used in a particularly advantageous embodiment of the invention to control the internal combustion engine

[0015] In a further step iii), at least one measured value is determined which depends on the composition of one of the phases, in particular the purified wash water.

[0016] Preferably, several time-delayed measurements of a phase are taken. This allows an increase in the concentration of a component to be determined. The phase is a volume flowing out of the centrifugal separator. Typically, the centrifugal separator operates continuously, so the phase also flows in a continuous flow, possibly with fluctuating flow values.

[0017] However, information can also be obtained from the sludge phase or an optional oil phase.

[0018] Finally, the operation of the internal combustion engine is controlled based on the measured value.

[0019] Thus, the measured value is not used solely to determine the quality of the washer fluid cleaning system, as was previously the case, but rather to set an optimal operating point on the combustion engine's characteristic curve. The process can include both active intervention in the engine control system and the generation of detailed instructions for an operator. Such instructions could, for example, involve checking the fuel quality.

[0020] Advantageous embodiments of the invention are the subject of the subclaims.

[0021] It is advantageous if at least one measured value or preferably a plurality of measured values ​​are determined, on the basis of which a material property of one of the phases and / or a concentration of a component of one of the phases is determined, and wherein the operation of the internal combustion engine is controlled on the basis of the determined material property and / or concentration.

[0022] The material property can be a physical material property, which is preferably dependent on the composition of the phase and is particularly preferably selected from one of the following material properties:

[0023] • Viscosity

[0024] • Density

[0025] • Thermal conductivity

[0026] • Electrical conductivity

[0027] Such quantities can be determined online. These are established measurement methods that exhibit comparatively low interference. It is also advantageous if step iii) involves determining a material property and / or the concentration of at least one component of a purified scrubber liquid, the scrubber liquid being essentially water. The scrubber liquid contains only minor components that interfere with the measurement. Therefore, this measurement exhibits a particularly low susceptibility to interference.

[0028] Alternatively or additionally, in step iii) the determination of a material property and / or the concentration of at least one component of a sludge phase can be carried out.

[0029] Alternatively or additionally, step iii) may also comprise the determination of a material property and / or the concentration of at least one component of an oil phase.

[0030] For analysis of the oil phase, the centrifugal separator can be designed as a three-phase separator.

[0031] The centrifugal separator can advantageously have a plate pack which improves the separation and which is arranged within a rotatably mounted drum of the centrifugal separator.

[0032] The method may further comprise a step v.) in which the turbidity of the purified scrubber liquid is reduced in at least a second purification stage to below 25 NTU, depending on the maximum limit value for overboard discharge.

[0033] The cleaned scrubber liquid can advantageously be discharged overboard a ship on which the plant is located.

[0034] Further advantageously, the determined concentration of a component of the purified scrubbing water can be a particle concentration in the purified scrubbing liquid.

[0035] The centrifugal separator can preferably be adjusted such that particles below a certain size limit are incompletely separated, wherein the size limit is less than 500 nm, preferably less than 300 nm. Furthermore, the system can comprise a measuring and evaluation unit for processing the measured values ​​and for outputting a control command for regulating the operation, in particular the operating point, of the internal combustion engine.

[0036] Finally, the measured value can be determined as part of an online measurement, with operation controlled continuously throughout the entire operating time of the internal combustion engine. When the internal combustion engine, e.g., a ship's engine in a harbor, stops running, operation ends and with it the operating time of the internal combustion engine. Continuous control of operation allows for dynamic adjustment of the internal combustion engine's operation to changing circumstances, e.g., increased power requirements in heavy seas, etc., and thus to changing fuel requirements or other circumstances.

[0037] Further advantages, features, and details of the invention will become apparent from the following description, in which several embodiments of the invention are explained in more detail with reference to the accompanying figures. Those skilled in the art will expediently consider the features disclosed in the figures, the description, and the claims individually and combine them into useful further combinations. They show:

[0038] Fig. 1 schematic representation of a process diagram of an embodiment variant of a method according to the invention; and

[0039] Fig. 2 Diagram of particle concentrations for different combustion behaviors in an internal combustion engine.

[0040] A method for controlling an internal combustion engine 2 in a system 1 for generating mechanical work. The system can advantageously be used on a ship. The internal combustion engine can be a marine engine.

[0041] An exhaust gas stream X1 generated by the internal combustion engine 2 is fed to a gas scrubber 4 of an exhaust gas purification system 3. The exhaust gas purification system 3 can optionally include a buffer tank 5 for temporarily storing contaminated scrubbing water X2.

[0042] The scrubbing water X2 is produced during the cleaning of the exhaust stream X1 by injecting scrubbing water into the exhaust stream X1. A cleaned exhaust stream X3 leaves the gas scrubber 4. In addition to or as an alternative to the injection, the gas scrubber 4 can also be designed as or comprise another type of wet scrubber.

[0043] The gas scrubber 4 also has a fresh water inlet. The inlet can be provided via a reservoir 6 and adjusted by a control device 7.

[0044] Numerous components in the exhaust gas (soot, ash, unburned fuel, lubricating oil, etc.) are transferred into the scrubbing water, which is discharged from the gas scrubber 4 as contaminated scrubbing water X2.

[0045] The contaminated wash water X2 can then be fed to a buffer tank 5 as an optional component of the exhaust gas purification system 3, which is also designed to receive purified wash water.

[0046] A wash water purification system is connected to the exhaust gas purification system 3. The wash water purification system can have several purification stages for cleaning the contaminated wash water X2.

[0047] In addition to particles, the contaminated wash water also contains oil, particularly in the form of dispersed oil droplets.

[0048] A first cleaning stage comprises a centrifugal separator 8, preferably a disc separator. The discs are preferably arranged as a disc stack 12 with several conical discs arranged parallel to one another.

[0049] EP 2 364 760 B1 describes the positive effect of a disc separator to separate oil and particles as a common phase. However, this oil separation, if present at all, is demonstrably not complete, but merely an observed side effect.

[0050] For quantitative separation of oil as a separate phase from the wash water, a three-phase separator is recommended. This allows for separate analysis of the oil as a separate phase.

[0051] The three-phase separator separates the contaminated wash water X2 into a light liquid phase, preferably an oil phase, X4, a flowable solids-containing sludge phase X5, and a purified wash water phase X6. The particular advantage of using a disc separator as a three-phase separator, in contrast to EP 2 364 760 B1 in the present inventive process, is that the use of a disc stack allows for a comparatively clear and therefore easily assayable oil phase and quantitative separation of particles down to a predetermined size range, preferably smaller than 500 nm.

[0052] The centrifugal separator 8 further preferably has a rotatably mounted drum and a non-rotatable outer hood with a discharge line for the sludge phase X5.

[0053] The particle size distribution between the separated sludge phase X5 and the wash water X6 can be adjusted by selecting the rotation speed of the drum and, if necessary, by adjusting the distance between the plates in the plate pack.

[0054] The particle size distribution in the respective phases after the first purification stage can be measured by video analysis of a sample irradiated with laser light. A small volume of sample water is passed through a measuring chamber and irradiated with laser light in the chamber. The measurement conditions are atmospheric pressure and room temperature. The diffraction pattern and movement can be evaluated for each particle.

[0055] The particle concentration can be determined by a turbidity meter after sampling at normal pressure and temperature, taking into account the usual fluctuation range for this measurement method.

[0056] The individual phases separated by the disc separator, especially the purified water phase X6, are easier to examine and, in particular, have a lower outlier rate.

[0057] Furthermore, the contaminated wash water X2 is transferred from the exhaust gas purification system 3 to the centrifugal separator 8 without the addition of additional flocculants. While in a number of separation processes, such as in EP 3 640 444 A1, flocculants are preferably added to enlarge the particles for more effective centrifugal cleaning, the present process is based precisely on the goal of not separating particularly small particles in the first cleaning stage, but rather using them for analysis and adjustment of the underlying engine operation. Flocculants or flocculation agents are substances that promote particle aggregation through deposition and thus increase the size and weight of the individual particles, which leads to better separation in the separator.

[0058] Furthermore, the system for generating mechanical work can have a sampling unit for laboratory analysis of the oil quality of the separated light liquid phase X4 and / or a sensor 9 for online determination, preferably for real-time analysis, of the oil quality of the separated light liquid phase X4. This can be a turbidity sensor for determining the concentration of ultrafine particles such as soot particles in oil. Alternatively or additionally, it can be, for example, a viscosity sensor, such as a Coriolis flowmeter. The viscosity provides information about the lubricating oil content in the separated oil.

[0059] The system for generating mechanical energy can alternatively or additionally comprise a sampling unit for laboratory analysis to monitor the composition of the separated sludge phase X5 and / or a sensor 10 for online monitoring, preferably for real-time monitoring, of the composition of the sludge phase X5. The monitoring can be performed, for example, using a viscosity or density sensor. A change in these sludge phase variables indicates a change in separation efficiency. For example, if the separation performance remains constant, this change can be attributed to a change in the operation of the internal combustion engine 2.

[0060] The separation performance does not have to be constant. This makes it possible to learn multiple operating modes while maintaining constant operation of combustion engine 2. This allows for extrapolation of the measurements when the separation performance changes. The same applies to the evaluation of the other separated phases X4 and X6.

[0061] Furthermore, the system for generating mechanical work can have a sampling unit for laboratory analysis of the water quality of the separated heavy liquid phase X6 and / or a sensor 11 for online determination, preferably for real-time analysis, of the water quality of the separated heavy liquid phase X6. This can be a turbidity sensor for determining the concentration of particles in water. Alternatively or additionally, a sensor for determining the laser diffraction of the particles can be used to determine the particle size distribution of the particles in the heavy liquid phase. Alternatively or additionally, this can be, for example, a viscosity sensor, e.g., a Coriolis flowmeter.

[0062] Alternatively or additionally, the PAH content in the heavy liquid phase can also be determined using sensor 11. This is preferably done through online measurement. Suitable sensors are commercially available, for example, the Memosens CFS51 from Endress + Hauser or the PAH500 from Hach and Lange.

[0063] Furthermore, the plant has a control element 13 for feeding the purified heavy liquid phase X6 to a second purification stage 14.

[0064] The second purification stage 14 can comprise another centrifugal separator, a membrane filter, an absorption filter with a suitable filter medium, a precoat filter, or the like. Unlike other separation variants, the use of an absorption filter with an activated carbon medium not only further reduces the NTU limit but also completely decolorizes the otherwise yellowish wash water. A precoat filter can also reduce the turbidity in the heavy liquid phase to 1-35 NTU.

[0065] From a threshold of 25 NTU, the doubly purified liquid phase X7 can be disposed of, e.g., overboard a ship. If the first purification stage already achieves sufficient purification, the heavy liquid phase X6 can also be discharged directly overboard the ship, bypassing the second purification stage 14.

[0066] Before discharging, the water quality of the discharged water phase can be checked, e.g. based on the PAH content of the residual oil, the NTU content, the pH value and / or the temperature.

[0067] If the purity is not sufficient, the water phase can be returned via a control device to the buffer tank 5, e.g. together with a contaminant phase X8 of the second purification stage 14.

[0068] The wash water purification system thus ensures that the quality criteria / limits specified by the IMG are met before the wash water is discharged into marine waters. Until now, the focus has been exclusively on purifying this water using a variety of processes (centrifuges, filters, membranes, etc.). The pollutants produced by combustion in the engine can have different causes in terms of their severity and their proportion in the exhaust gas.

[0069] The approach of the present invention is to use the analysis of the washing water to obtain additional information about the combustion process in the engine and to give the operator indications of malfunctions, wear or even inferior fuel.

[0070] Depending on the cleaning variant, an impurity fraction from the second cleaning stage 14 can be returned to the buffer tank 5 via a return line of an impurity phase X8, which is more contaminated than the supplied heavy liquid phase X6.

[0071] A further purification stage 15, e.g., a membrane filter or particle filter with an exchange medium, can be arranged on the recirculation line. This removes the ultrafine particles enriched in the impurity phase X8 from the impurity phase X8 and / or the heavy liquid phase X6. This again changes the composition of this recirculated phase. In the context of the present invention, the person skilled in the art knows that additional control elements are usually provided at intersection points in Fig. 1. A further impurity phase X9 can be removed from the purification stage 5 only optionally.

[0072] From the buffer tank 5, liquid can be recirculated to the gas scrubber 4 for injection or other use. The recirculation rate depends primarily on the degree of contamination of the liquid.

[0073] After determining and / or monitoring individual variables T1, T2 and / or T3 which depend on the composition of the respective phase X4, X5 or X6, such as viscosity, particle concentration and / or PAH value (polycyclic aromatic hydrocarbons), these variables are used to control the operation of the internal combustion engine 2.

[0074] The determined variable or variables T1, T2 and / or T3 are transmitted to a measuring and / or evaluation unit 16, which, based on the determined variable and / or variables, issues a control command S1 to adjust the operation of the internal combustion engine 2. This allows, among other things, combustion to be optimized in a preferred low-emission operating mode or, for example, combustion to be adapted to the fuel during a fuel change.

[0075] This takes advantage of the fact that the first cleaning by the centrifugal separator is incomplete, so that in particular the measured values ​​of the heavy liquid phase X6 can be used to control the operation of the internal combustion engine 2.

[0076] If, for example, the concentration of particles in this heavy liquid phase increases, this is significant for incomplete combustion of fuels in the internal combustion engine.

[0077] The following analyses can be traced back to the following qualitative characteristics of the operation of the internal combustion engine: a) Determination of the particle concentration => increase of particles < limit, e.g. 300 nm = deterioration of the combustion in the engine, inferior fuel b) Oil-in-water content

[0078] I. Increase above limit indicates deterioration of combustion in the engine

[0079] II. Detection of lubricating oil => excessive lubricating oil input, wear

[0080] III. Fuel detection => insufficient fresh air supply, insufficient atomization of fuel c) PAH content => increase => sign of incomplete combustion, low-quality fuel, insufficient fresh air supply

[0081] With regard to the detection of lubricating oil or fuel, it should be noted that there are commercially available oil-in-water sensors that can be calibrated for various oils, including fuel and lubricating oil. Therefore, the detection of these substances is possible.

[0082] In contrast to other cleaning technologies, in centrifugal separator 8 the separation efficiency decreases with smaller particles.

[0083] Thus, measurements can be taken after the centrifugal separator 8 and before the second purification stage 14. The purification in the second purification stage can be carried out in various ways, e.g. by filtration using membranes, by other filters, by adding flocculant and subsequent centrifugal separation.

[0084] In the second purification step, the wash water is completely purified. Centrifugal separator 8, on the other hand, allows through precisely those particles that need to be monitored. Particle measurement upstream of the purification system (in the raw water) is technically almost impossible due to the high level of contamination.

[0085] As a three-phase separator, the centrifuge also offers the possibility of more detailed analysis of the separated light phase (e.g., oil and fuel). The pollutants are significantly more concentrated and are easier to detect, both quantitatively and qualitatively.

[0086] However, in a less preferred variant, the invention can also be carried out in a two-phase separator.

[0087] The process is applicable to wash water in SOx scrubbers (desulfurization) and NOx scrubbers (reduction of nitrogen oxides by exhaust gas recirculation).

[0088] In the course of extensive investigations, it was surprisingly found that the small particles that cannot be separated out with the centrifugal separator, with average particle sizes of preferably less than 500 nm, particularly preferably less than 300 nm, become more concentrated when the engine is operated at a non-optimal operating point.

[0089] This is explained in more detail in Fig. 2.

[0090] The diagram shows engine operation with heavy fuel oil. The heavy fuel oil contains 1.34 wt.% sulfur. The load points are 20 and 60 kW with the same operating time.

[0091] Curve A shows the change in particle concentration under optimal combustion conditions.

[0092] Curve B shows the change in particle concentration during incomplete combustion. Curve C shows the increase in particles in relation to the average particle diameter between curves A and B. It can be seen that a change in particle concentration occurs primarily for small particles, from 10 to 200 nm, while for larger particles, there is no significant increase in the concentration in the wash water during suboptimal combustion.

[0093] As can be seen from Fig. 2, the particle concentration increases significantly during non-optimal operation of the internal combustion engine.

[0094] If such an increase is registered, according to the present invention the operating point of the internal combustion engine can be readjusted until the increase decreases or levels off.

[0095] Reference symbol

[0096] 1 . Plant for generating mechanical work

[0097] 2. Internal combustion engine

[0098] 3. Exhaust gas purification system

[0099] 4. Gas scrubber

[0100] 5. Buffer tank

[0101] 6. Reservoir

[0102] 7. Regulatory organ

[0103] 8. Centrifugal separator

[0104] 9. Sensor

[0105] 10. Sensor

[0106] 11 . Sensor

[0107] 12. Plate package

[0108] 13. Regulatory organ

[0109] 14. second cleaning stage

[0110] 15. further cleaning stage

[0111] 16. Measuring and evaluation unit

[0112] X1 exhaust gas flow

[0113] X2 Washing water

[0114] X3 purified exhaust gas stream

[0115] X4 Oil phase

[0116] X5 Sludge phase

[0117] X6 purified wash water phase

[0118] X8 Contamination phase

[0119] X9 Contamination phase

[0120] T1 measurement signal

[0121] T2 measurement signal

[0122] T3 measurement signal

[0123] S1 control command

Claims

Patent claims 1 . Method for controlling a plant (1) for generating mechanical work, wherein the plant (1) has an internal combustion engine (2), an exhaust gas purification device (3) comprising a gas scrubber (4) and a scrubbing water purification plant comprising a first purification stage with a centrifugal separator (8), characterized by the following steps: i) purification of the exhaust gas (X1) generated by the internal combustion engine (2) to provide contaminated scrubbing water (X2); ii) purification of the scrubbing water (X2) by the centrifugal separator (8) to provide several phases (X4, X5, X6), wherein one of these phases (X4, X5, X6) comprises purified scrubbing water (X2) with a lower particle content compared to the supplied contaminated scrubbing water (X2);iii) determining at least one measured value (T1, T2, T3) which is dependent on the composition of at least one of the phases (X4, X5, X6); iv) adjusting the operation of the internal combustion engine (2) on the basis of the determined measured value (T1, T2, T3); 2. Method according to claim 1, characterized in that the at least one measured value or preferably a plurality of measured values are determined, on the basis of which a material property of one of the phases (X4, X5, X6) and / or a concentration of a component of one of the phases (X4, X5, X6) is determined, and wherein the control of the operation of the internal combustion engine (2) takes place on the basis of the determined material property and / or concentration.

3. The method according to claim 2, characterized in that the material property is a physical material property, which is preferably dependent on the composition of the phase (X4, X5, X6) and is particularly preferably selected from, for example, one of the following material properties: • Viscosity • Density • Thermal conductivity • Electrical conductivity 4. Method according to one of the preceding claims, characterized in that in step iii) the determination of a material property and / or the concentration of at least one component of a purified wash water (X6) takes place.

5. Method according to one of the preceding claims, characterized in that in step iii) the determination of a material property and / or the concentration of at least one component of a sludge phase (X5) takes place.

6. Method according to one of the preceding claims, characterized in that in step iii) the determination of a material property and / or the concentration of at least one component of an oil phase (X4) takes place.

7. Method according to one of the preceding claims, characterized in that the centrifugal separator (8) is designed as a three-phase separator.

8. Method according to one of the preceding claims, characterized in that the centrifugal separator (8) has a plate pack (12) which is arranged within a rotatably mounted drum of the centrifugal separator (8).

9. Method according to one of the preceding claims, characterized in that the method comprises a step v.) in which the purified wash water (X6) is reduced in at least one second purification stage (14) to a particle content of less than 25 NTU.

10. Method according to one of the preceding claims, characterized in that the purified washing water (X6) is passed overboard a ship on which the system (1) is arranged.

11. Method according to one of the preceding claims, characterized in that the concentration is a particle concentration in the purified wash water (X6) after the centrifugal separator (8) and before the second purification stage (14).

12. Method according to one of the preceding claims, characterized in that the centrifugal separator (8) is set such that particles below a limit size are incompletely separated, wherein the limit size is less than 500 nm, preferably less than 300 nm.

13. Method according to one of the preceding claims, characterized in that a system (1) has a measuring and evaluation unit (16) for processing the measured values (T1, T2, T3) and for outputting a control command (S1) for regulating the operation, in particular the operating point, of the internal combustion engine (2).

14. Method according to one of the preceding claims, characterized in that the determination of the measured value (T1, T2, T3) takes place within the framework of an online measurement, the control of the operation taking place continuously over the entire operating time of the internal combustion engine (2).

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