JP2012511692A - High-efficiency large-volume heavy ash extraction and cooling system - Google Patents

Abstract

  The present invention is a system for extracting and recovering energy from a large amount of heavy ash stream produced by a solid fuel boiler, typically fixed at a value of about 1.5% of the total combustion air by the boiler designer. And a system that can reduce the final temperature of the extracted ash without increasing the air flow entering the boiler flue. When the airflow required for cooling exceeds the maximum amount available in the boiler, the system will remove excess air and possibly steam, air / smoke exchanger air, due to the separation of the cooling environment produced by the ash itself. Enter the side, can be sent to the air injection duct. Separation of the cooling system environment is performed automatically based on the ash temperature signal from the system to the discharge. If the cooling air is not sufficient to cool the ash, cooling efficiency can be improved by adding atomized water.

Description

The present invention relates to a plant and method for extracting, cooling, and recovering the thermal energy of a large amount of heavy ash stream produced by a solid fuel boiler.

BACKGROUND OF THE INVENTION With the ever increasing demand for solid fossil fuels to generate electrical energy, the burning of high ash coal or lignite has become increasingly frequent. When burning coal or lignite in a high-power boiler, a large amount of heavy ash of up to 100 tons per hour, which often has a high proportion of unburned material, is generated. Such an amount of dry cooling, or mainly dry cooling, requires a large amount of cooling air flow that is twice or three times that of fossil fuels with high heat generation output.

  As shown in EP 0 470 155 B1, in some known ash extractions and dry cooling, cooling air is introduced into the boiler from its bottom when heated under the influence of heat exchange with the ash. Thus, in principle, the greater the amount of ash produced, the greater the recovery of heat supplied to the boiler by cooling air, as described above, for both heat exchange with air and combustion of unburned material.

However, combustion efficiency is not adversely affected by air introduced into the combustion chamber from the bottom rather than a burner or other predetermined air inlet, and / or similar undesirable for the production of nitrogen oxides (NO _x ) In order to be unaffected, boiler designers prefer to limit this amount to a maximum of 1.5% of the total combustion air.

  In connection with what has been said above, known refrigeration systems are particularly suitable for dry cooling of heavy ash, or primarily dry cooling, and associated cooling air disposal, especially when the ash is in a large stream and has an unburned material content. It is not successful to perform effectively and efficiently when it is high and therefore at high temperatures. In particular, even if the cooling, thermal energy recovery and disposal are successful, the plant becomes extremely complex in achieving them, resulting in very high implementation and processing costs.

  WO 2008/023393 (the disclosure of which is hereby incorporated by reference) exceeds the maximum flow rate that the air flow necessary to cool the extracted heavy ash is acceptable to the combustion chamber. Excess air can be sent to the fume duct due to the pressure separation of the cooling environment made by the ash itself. Further, in WO 2008/023393, the location where the excess air is introduced is optionally located upstream or downstream of the air / smoke exchanger of the duct described above.

  The potential system limitations of WO 2008/023393 are the loss of heat content associated with the cooling air used downstream of the pressure separation system and the smoke that must be handled by the device downstream of the air introduction point. The overall flow is increasing.

  In practice, when hot air is injected downstream of the air / smoke exchanger, the heat content of the cooling air is completely lost, and in addition to the increased power absorbed by the equipment required for the smoke process, The overall temperature of the smoke will rise.

  When hot air is injected into the fume duct upstream of the exchanger, the cooling air is at a lower temperature than the combustion smoke stream, thus increasing the hot air flow + smoke flow entering the exchanger, thereby increasing the environmental air / smoke of the device. Heat exchange efficiency deteriorates.

  In particular, the cooling air described above can reach a temperature of about 200 ° C., and therefore, as described above, by injecting the cooling air into smoke having a temperature of about 400 ° C., eventually the air / smoke This may be impractical in the exchanger and, in fact, even if the heat content of the flow entering the smoke side is increased based on the operating principle of the air / smoke exchanger, Unless it is in the case of a critical part, it is not transmitted well to the air.

  Furthermore, hot air entering the fume duct (generated upstream or downstream of the exchanger) is placed downstream of the air / smoke exchanger in addition to the overall increase in temperature of the smoke stream to be treated. The electrostatic precipitator will receive an overall flow higher than the design data. These situations dictate the deterioration in the efficiency of electrostatic sorters caused by increased injection rates, particularly by increasing ash resistivity.

BRIEF DESCRIPTION OF THE INVENTION Based on what has been presented in the previous section, the technical problem raised and solved by the present invention is an apparatus and method which makes it possible to eliminate the drawbacks mentioned above in relation to known techniques. Is to provide.

  These problems are solved by the plant according to claim 1 and by the method according to claim 22.

  Preferred features of the invention reside in the claims subordinate to the above claims.

  The present invention provides significant advantages that will be fully understood in view of the detailed description set forth below.

  The main advantage resides in the fact that the invention makes it possible to maximize the recovery of sensible heat contained in excess cooling air used in the second plant part downstream of the pressure shut-off.

  The structure proposed in the present invention actually allows cooling air to be injected into the ambient air stream sent to the air / smoke exchanger before entering the combustion chamber. The ambient air that is mixed with the hot cooling air before entering the exchanger rises in temperature and is effectively preheated. This structure allows the efficiency of the air / smoke heater to remain substantially unchanged and allows the sensible heat of the cooling air to be recovered. In practice, the present invention enables the total recovery of sensible heat obtained by cooling air in the plant portion downstream of the pressure separation, and at the same time, the electrostatic precipitator so as not to lower the separation efficiency of the electrostatic precipitator. The smoke flow across and the temperature remains unchanged.

  The present invention also maintains the advantages already present in the system of WO2008 / 023393, i.e. without exceeding the 1.5% limit mentioned above for the cooling air introduced into the combustion chamber from the bottom. It is also possible to obtain efficient dry cooling of ash or mainly dry cooling.

  The present invention is actually heat recovery of the systems described in EP 0 471 555 B1 and WO 2008/023393 when applied to large amounts of heavy ash from high ash coal or lignite. By optimizing the possibility of such systems, it is possible to optimize such systems.

  By integrating the detailed description of the embodiments shown below, the present invention provides an air flow that enters the boiler flue, which is typically fixed at a value of about 1.5% of the total combustion air by the boiler designer. For large heavy ash streams produced by solid fuel boilers that can reduce the final temperature of the extracted ash without increasing it, pneumatic or dual, ie air / water extraction and cooling About the system. When the air flow required for cooling exceeds the maximum amount allowable in the boiler, the system preferably removes excess air to the combustion air suction duct, preferably to the secondary air duct, due to the separation of the cooling environment made by the ash itself. Can send.

  Due to the concentrated and distributed load losses of the plant structure, and thus the cooling air connection line, it may be useful to provide a fan that interrupts in series to provide the correct push into the intubated fluid.

  Due to the overall increase in ambient air temperature entering the exchanger, the reduction in temperature difference between smoke and ambient air is negligible and the overall performance of the air / smoke heater is negligible. .

  Separation of the environment of the cooling system is handled automatically based on temperature and / or ash flow signals at the exhaust from the system.

  If the cooling air is not sufficient to cool the ash, cooling efficiency can be improved by adding mist water. The amount of water normally added should, if necessary, ensure complete evaporation of the injected water in order to obtain dry ash suitable for pneumatic pulverization and transport at the discharge. Injected based on flow rate and ash temperature.

Based on the preferred structure, the proposed system to use is mainly:
1. A transition hopper between the boiler and the extractor of the type of interest described in the above-mentioned patent, EP 0471555B1,
2. The extractor described above;
3. An ash crusher,
4). A transition reservoir between the grinder and the conveyor-cooler, for example in the form of a hopper;
5. In some cases, the conveyor-cooler described above, with a suitable plow blade provided with the function of remixing the ash on the conveyor itself, and a nozzle for jetting water;
6). A boiler comprising a conveyor-cooler (preferably in the area of the discharge casing of the conveyor-cooler) and possibly a cyclone separator and regulating valve for removing fine ash contained in the cooling air stream. A pipe or duct connecting between the most suitable points of the system, injecting ambient air into the air / smoke exchanger to remove cooling air that exceeds the maximum allowable cooling air;
7). A fan present in some cases in series with the above-mentioned pipe when the absolute value of the concentrated load dispersion of the line is higher than the negative pressure value present at the cooling air inflow point;
8). A discharge end device (eg, a valve or vibration extractor, or simply another transport or storage closure device that can allow ash discharge by simultaneously preventing uncontrolled air from entering the system. Closed connection)
9. An alternative to the discharge end device in step 8 above, when the system is unable to ensure proper ash cooling due to abnormal ash conditions (high flow and / or high temperature) An optionally present ash-water mixer activated as an object,
A connecting pipe or duct that discharges humid air to the pipe of step 6;
A discharge end device equivalent to that described in step 8, which allows ash discharge from the system by simultaneously preventing return of external air;
An ash-water mixer comprising:
10. An adjustment and control system that can ensure that the operation is performed as described in the operation description section below;
Consists of.

  Other advantages, features and applications of the present invention will become apparent from the following detailed description of several preferred embodiments, given by way of example and not limitation. Reference is made to the figures of the accompanying drawings.

Schematic illustrating a preferred embodiment of the plant of the present invention in a mode of operation that provides pressure separation between the two cooling environments and connection to the ambient air injection line to the air / smoke heater of the second plant part. The figure is shown. Fig. 2 shows a schematic diagram in longitudinal section of a separation region of two cooling environments of the plant of Fig. 1; FIG. 3 shows a cross-sectional view along line AA in FIG. 2. FIG. 2 shows a schematic diagram illustrating the plant of FIG. 1 in different operating modes that do not provide the separation for two cooling environments. Fig. 5 shows a cross-sectional view of a double shaft continuous mixer with nozzles for the cooling air of the plant of Fig. 1 according to the line BB of Fig. 4; FIG. 6 shows a schematic diagram illustrating the plant of FIG. 1 in an operational mode for sending still hot ash to the mixer of FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS With reference to the above-mentioned figures, a plant for extracting and cooling combustion residues according to a preferred embodiment of the invention, for example of the type used in solid fossil fuel thermoelectric plants, is indicated generally at 1. ing. As will be better understood in the following description, the plant 1 is particularly suitable for treating large amounts of heavy ash streams, for example produced by the combustion of high ash coal or lignite.

  For clarity of explanation, the various components of the plant 1 follow the path that the combustion residue follows, such as extraction from the bottom of the combustion chamber (or boiler), indicated by 100 of combustion residue, to disposal. The description will be made as follows.

  Immediately downstream of the combustion chamber 100, or better still immediately downstream of the transition hopper 105 of the fuel chamber 100, the plant 1 is a dry extraction realized by a first extraction and transfer unit, in particular mainly high heat resistant steel. A machine 9 is provided. Said extractor 9 is of the type described in European Patent No. 0522967, which is known and for example incorporated herein by reference. The extractor 9 collects heavy ash that sinks downward in the combustion chamber 100 through the transition hopper 105 described above.

  The extractor 9 has a plurality of holes in the side wall of its own casing for external cooling air inlets, which are substantially uniformly distributed along the deployment of the extractor 9 itself, Each is indicated by 10. Said inlet 10 can be provided with means for regulating the flow, or the inlet 10 can be activated or deactivated. The extractor 9 can further have an additional external cooling air inlet 19 which is preferably regulated by an automatic valve or equivalent flow control means as well and is arranged substantially at the end of the extractor 9 itself. .

  Cooling air is drawn countercurrently into the extractor 9 via inlets 10 and 19 under the influence of the negative pressure present in the combustion chamber 100. More specifically, air enters due to the negative pressure present in the transition hopper 105, and a negative pressure (generally about 300 to 500 Pa lower than atmospheric pressure) adjusted by the control system of the combustion chamber 100 on the bottom surface of the transition hopper. is there.

  Downstream of the extractor 9, the ash is fed to the crusher 3, which crushes the coarsest fragments of ash so as to increase the heat exchange surface and thereby improve the efficiency of such exchange and thus cooling. Crush.

  An additional external cooling air inlet is provided downstream of the pulverizer 3, which is indicated at 17 and, in some cases, is also provided with flow control means such as those described above. In this case as well, the air entering from the inlet 17 is supplied countercurrently in the pulverizer 3 itself along the first extractor 9 under the influence of the negative pressure present in the combustion chamber 100. The cooling air is useful not only for cooling the ash but also for cooling the machine.

  As shown in more detail in FIGS. 2 and 3, the ash is conveyed by the hopper / reservoir 8 to the second steel belt conveyor-cooler 6 downstream of the grinder 3. As will be explained in more detail below, the hopper 8 operates like a reservoir and ensures separation of the two atmospheres of the extractor 9 and the conveyor / cooler 6 under defined conditions and with the plant structure described above. As it can accumulate ash. In particular, in the presence of the accumulation, the conveyor 6 ensures a separation between the extractor environment associated with the pressure rate of the combustion chamber 100 and the conveyor / cooler environment associated with the different pressure rates in the communicating area. By operating continuously under the head of the material, it operates accurately as a second extractor.

  Coupled to the hopper 8 are maximum and minimum level sensors, indicated at 7, and a layer leveler 18 disposed in the initial portion entering the conveyor 6.

  The position indication of the layer adjuster 18 in relation to the belt speed indication of the conveyor cooler 6 provides information regarding the ash volume flow that is useful in conjunction with the temperature indication for adjusting the cooling fluid.

  On the conveyor 6, as already described for the first extractor 9, the ash is cooled by air drawn from the outside through an additional inlet 11 located on the side wall of the extractor 6 itself. Continuing, as well, it can have an additional external cooling air inlet corresponding to 19, which is also preferably regulated by an automatic valve or equivalent flow regulating means, in a substantially initial part of the conveyor 6 itself. Be placed.

  If necessary, the cooling on the conveyor 6 can be effected by water that has been elaborated by the discharge nozzles 12 arranged inside the cover of the conveyor 6.

  At this point, it will be appreciated that the plant 1 can be equipped with a double or air / water cooling system, in particular realized by the air inlets 10, 11, 17 and 19 and by the water discharge nozzle 12.

  The plant 1 further provides a means for supplying a portion of the cooled air heated after heat exchange with the combustion residue into an ambient air exhaust duct 50 coupled to the air / ash exchanger 102. In this embodiment, the supply means comprises a duct 51, which is suitably insulated to avoid condensate and traced with respect to heat and can be selectively adjusted, but arranged along its deployment. Can be interrupted / enabled by an automated valve 150 (or equivalent means).

  More particularly, the duct 51 connects the discharge area of the conveyor 6 (FIG. 1) and / or possibly the mixer 2 (FIG. 6) to the suction area of the secondary environment air to the air / smoke exchanger. Or better can be connected. Thus, preferably, duct 51 exits upstream of a line coupled to secondary air fan 54 that injects ambient air into air / smoke exchanger 102 (air side), and air / smoke exchanger 102 is combusted. The air can be preheated and is generally provided in the combustion plant associated with the present invention. As is known, negative pressure is provided to these injection regions by the air fan 54 described above or equivalent pressure control means.

  Switch 102 may be of the type commonly referred to as Jungstrom.

  A cyclone separator 55 or equivalent device capable of collecting the fine ash that may be present in the cooling air stream exiting the conveyor 6 and / or the mixer 2 and suitable regulating valves 150, 59 are connected to the duct 51. Can be combined into a line.

  Furthermore, if the concentrated and distributed load loss of cooling air is higher than the negative pressure provided at the inlet of the duct upstream of the fan 54, or the effective head at the fan 54, the fan 56 is in series with the duct 51. May be.

  In general, the optimal injection point for cooling air is represented by a suction duct of a combustion air fan that draws air from the environment, which delivers air to the air / smoke exchanger. As shown in FIG. 1, the switch is of the trisector type, i.e. two inlets 61 and 62 respectively dedicated to combustion air (divided into primary and secondary) and a dedicated inlet for smoke As described above, the preferential place where the cooling air is injected is detected by the secondary air suction duct. The location is preferably related to the suction line of the primary air fan 58 because, in practice, the pressure level of the primary fan 58 is much higher than the secondary fan and thus the energy loss in pumping is higher.

  If the plant structure does not allow connection of the secondary air to the suction line, the primary air line can be selected, which provides an advantage to a lesser extent with respect to heat recovery.

  The advantage of injecting cooling air upstream of the fan (primary fan 58 or secondary fan 54) also ensures that the fan always handles the same amount of infused air and therefore no operational fluctuations.

  In an alternative embodiment, the cooling air can be routed to enter the direct air side of the air / smoke exchanger 102.

  Since there is a substantially wedge-shaped member 14 which is fixed with respect to the predetermined remixing means, in particular the conveyor belt 6 itself, and in this example is shaped like a scraper, ash cooling on the conveyor 6 is made more effective. can do. The plow blade-shaped member 14 is substantially uniformly distributed along the developed portion of the conveyor 6 and is disposed in the ash conveying portion. As mentioned above, the blade-like member 14 is continuously remixed during transport on the belt and exposed so that the maximum surface is available for heat exchange with air and / or cooling water. To scoop out the ash.

  An automatic diverter valve 16 (or an equivalent means for selectively diverting the ash stream) is provided downstream of the conveyor 6, which can either supply the cooled ash to the outward discharge means 13 or in this example. It can be selectively supplied to a continuous mixer 2 which communicates with the outside and is shown in more detail in FIG.

  The discharge conveyor 13 is controlled to prevent incoming air from entering uncontrolled (or, in a variant of the embodiment, the system is connected to other transport or storage enclosures). ) Device (not shown).

  Cooling of the ash by means of a mixer 2 containing water, if necessary, to reach a temperature value compatible with the downstream process or to humidify the ash to reduce powder emissions under certain transport and disposal conditions. Can be completed. The mixer 2 is provided with a discharge casing 21 provided with means that allow the discharge of ash from the system by preventing the outside air from returning to uncontrolled at the same time. Such a device can be constituted, for example, by a double clapet valve or rubber plate, which can discharge the ash to the minimum passage part required when deformed by the weight of the ash.

  According to a variant of the preferred embodiment, a pipe 66 is provided that connects the mixer 2 to the duct 51 so that air and steam are discharged into the duct 51 by means of a valve 59 or equivalent in the line means.

  And the plant 1 is in this example an ash temperature sensor and / or arranged at the end or discharge part of the conveyor 6 and / or at the main extractor 9 or more preferably at the ash discharge part of the conveyor 13. Volume and / or weight flow sensors are provided. Advantageously, a sensor of the type described above is also provided in the hopper / reservoir 8.

  Furthermore, the hopper 8 can be provided with a load cell or equivalent means for controlling the level of ash in the hopper / reservoir.

  Furthermore, temperature sensor means arranged in the duct 51 can be provided.

  The plant 1 comprises a control system in communication with the sensor means, which can control the operating mode of the plant 1 related to the amount and temperature of ash.

  Here, the operation mode of the plant 1, in particular, the operation mode of the cooling system of the plant 1 controlled by the control means described above will be described in more detail.

  First, the ash temperature and / or flow values provided by the sensor means are compared with values preset and stored by the control system, and based on the results of such comparison, are most suitable for the operation of the plant 1. Correct operating mode is established. With respect to the need to make temperature and / or flow measurements, it should be noted that the increase in ash temperature is usually associated with an increase in ash flow in the plant 1 considered here.

  The start-up plant is configured in the mode shown in FIG. 4 by adjusting all the air inlet valves 10, 11, 17 and 19 and closing the automatic valve 150 so that 1.5% of the combustion air Can be drawn from the hopper 105 of the boiler 100 through the bottom flue by crossing the ash in countercurrent in both the extractor 9 and the conveyor 6.

Such an operation mode is performed until the temperature of the ash in the discharge part of the conveyor 6 reaches a predetermined temperature T _minimum .

  In such an operation mode, the control means makes the belt of the extractor 9 substantially by making the flow rate of ash on the conveyor 6 larger than that of the extractor 9 so that no substance head is formed in the hopper 8. And acts on the relative speed of the belt 6.

_{Beyond the} value T _minimum , the system reduces the speed of the conveyor 6 and adjusts the conveyor 6 so as to perform, among other things, the accumulation of ash in the hopper 8 and thus the formation of a continuous ash plug. The valve 150 of the duct 51 is opened so as to affect the speed and further generate two different atmospheres for each of the extractor 9 and the conveyor 6, the first atmosphere is connected to the pressure present in the boiler, the second The atmosphere is connected to the pressure present in the ambient air supply duct 51.

  In said mode of operation, the air inlet valves 10, 19 and 17 of the extractor 9 and hopper 8 first add air to a calculated rate so as not to affect the operation of the downstream air / smoke exchanger, Thereafter, if necessary, only 1.5% of the total cooling air that can enter the boiler and valve 11 and possibly the nozzle 12 of the conveyor 6 later by adding water to reach the desired cooling. Is automatically adjusted to concentrate on the extractor. In this regard, in order to select where the cooling air is injected, the fan 54 always processes the same amount of air as the cooling air through the duct 51 increases, reducing the air drawn from the environment. It should be.

  In the environment separation structure, the cooling air acting on the main extractor 9 introduced by the inlets 10, 17 and 19 crosses these countercurrent extractors and enters the combustion chamber 100 within a limit of 1.5%. . Cooling air exceeding 1.5% is taken from the outside through the inlet 11 of the conveyor 6 and 19 equivalents if present and crosses the conveyor 6 in equicurrent and is blown by an air fan 54 and possibly a duct. The negative pressure generated by the auxiliary fan 56 placed in a line to 51 is sucked through the duct 51, possibly with steam caused by local cooling of the water.

  In this way, by returning the associated energy to the boiler, the maximum possible combustion is possible, possibly in the case of unburned material on the belt of the extractor 9, and the intervention of cooling water is reduced to a minimum. As a result, maximum cooling on the belt of the conveyor 6 is obtained.

  Such an operation mode is illustrated in FIG.

  When the ash head described above is present, the speed of the conveyor 6 is controlled in accordance with the detection of the maximum and minimum level sensors 7 to avoid the load hopper 8 being empty. In particular, when the level reaches a minimum value, the speed is reduced until the conveyor 6 stops, whereas when the minimum level is exceeded, the conveyor 6 is restarted, and when the maximum level is reached, the speed, and therefore the belt of the conveyor 6 belt. The flow increases.

  In the structure considered here, the control means can have additional information available to be detected by predetermined sensor means, in particular related to the temperature of the ash in the hopper 8 and the advance speed of the conveyor 6. The advance speed of the conveyor, along with the (fixed) value of the extraction part, accurately defines the ash volume flow. It must be clarified that the extraction level must be higher than a suitable margin of the size of the ash pieces leaving the grinder 3 in order to avoid possible obstacles in the extraction section itself.

In addition, in the further mode of operation illustrated in FIG. 6, the plant 1 is subjected to a very large amount of ash flow / temperature (higher than the design value), for example depending on the type of fuel or by cleaning the combustion chamber 100. Can also be handled. In this case, it is assumed that the ash temperature is higher than the value T _{very high} , and the plant 1 provides the mode of operation as described last, with the diverter valve 16 feeding still hot ash to the mixer 2 instead of the conveyor 13. Discharge.

  Mixer 2 introduces an additional amount of water so that the ash is at a provided final temperature (generally around 80 ° C.) with a suitable humidity content (preferably about 10%), so that the powder is transferred to the subsequent transfer operation. You can be sure that there is no.

  In order to avoid that the steam generated by such cooling in the mixer 2 rises again toward the conveyor 6 (there is a risk that condensate is generated), directly between the conveyor 6, the mixer 2 and the duct 51. An opposite “Y” connection can be provided. With such a construction, the air coming from the conveyor / cooler 6 and possibly the steam is added to the steam generated in the mixer 2, so that it goes to the duct connecting the fume lines. This connection duct (between the mixer 2 and the main duct 51), which can be suitably heated if the design conditions should be aware of the condensate formation and the associated risk of ash deposition, The danger still remains.

  It will be appreciated that the operator of the plant 1 can selectively set the pre-fixed value of the temperature and / or flow rate or quantity of a predetermined combustion air.

  It will be further understood that the operating mode described above constitutes just one of the possibilities of handling the plant 1. For example, a simpler mode of operation produces an ash head when a pre-fixed temperature value is reached, and if necessary manipulates the rest by adjusting the flow of cooling air and water appropriately Can be done.

  A series of operating modes, such as those considered so far, can be set manually or automatically by the operation / control system, which is based on the ash temperature / flow rate value. By acting on the formation, the air flow entering the extractor 9 and the conveyor 6, possibly injecting mist-like water, and activation of the diverter valve, the cooling mode of the ash itself is determined.

  In general, at this point, the plant 1 has general operational versatility, so that any ash flow can actually occur without problems associated with introducing an excessive amount of cooling air from the bottom of the boiler 100. It will be understood that it can be handled in an automated manner. As mentioned above, by introducing a very high cooling air flow and supplying the air / smoke exchanger with an additional air flow that is not suitable for introduction into the ambient air injection duct from the bottom of the boiler and This versatility is achieved by the possibility of adding additional cooling water.

  As far as this last aspect is concerned, preferably the plant 1 appropriately injects the amount of water used through its control means, so that the water is completely vaporized during the cooling process and at the outlet of the conveyor 6, A substantially dry ash suitable for being automatically crushed and transported can be obtained. This can be obtained by maintaining the final temperature of the ash above about 100 ° C. The flow of water that is atomized and injected is on the one hand the heat removed from the ash (generated from the flow for a given enthalpy variation required between the temperature in the hopper 8 and the final discharge temperature) and on the other hand Controlled by a thermal balance means that equalizes the sum of the heat of vaporization of the water and the enthalpy variation in the cooling air.

  Also, by sending a portion of the cooling air in the ambient air injection duct to the air / smoke exchanger, maximum heat recovery associated with the cooling air is possible and is described in the above-mentioned European Patent No. 0471105B1. It will also be appreciated that the performance benefits already associated with the dry extractor described in can be enhanced.

  It will also be appreciated that the presence of a scalloped member or equivalent means allows the water cooling to be selectively actuated by the nozzle 12 as well as making the ash temperature uniform.

Furthermore, the temperature sensor arranged in the duct 51 not only enables more complete control of the plant parameters, but also verifies possible condensate formation points in the entire duct 51 due to steam generated from the cooling water. It will be understood that it can be done. In fact, by knowing the temperature of the air itself and the amount of mist water, you can easily calculate the relative humidity of the cooling air,
On the other hand, the humidity itself falls below 100% with an appropriate significant margin,
On the other hand, the moisture content in the air is a problem for good system operation, even in cold locations, which may be present in the path (ie mainly on the cover of the conveyor 6 and on the surface of the connection duct 51). That does not lead to the start of condensate,
This can be verified.

  In order to avoid any danger of the formation of condensate in the system, additional connecting ducts (or equivalent means) are selectively moved to the external air inlets on these ducts to cool the hot air coming from the transition hopper 105 and cold By providing a valve that regulates both the flow of ambient air, it can be provided between the transition hopper 105 and the conveyor 6 near the hopper 8. As a result, the temperature of the air in the system can be raised to a level that eliminates the risk of condensate formation. Based on the detection of the above-described temperature sensor arranged on the duct 51, the above-described adjustment of the incoming hot air and cold air flow can be performed.

  Finally, it will be included that the separation into the two environments described above can be obtained by a device different from the one described above. For example, an additional device, such as a crappet valve or equivalent device, can be provided between the extractor 9 and the conveyor 6, and the separation of the two environments can be carried out under the hopper / reservoir 8. It can be obtained by applying a second grinding stage of variable flow rate with respect to the grinder 3 so that the necessary ash heads that can be separated can be produced in the hopper.

  By sending the maximum ambient air flow over the extractor 9 according to the present invention, the amount of air on the second extractor 6 (to add water) and thus the energy required for the treatment of smoke is greatly reduced. It will be appreciated that efficient energy recovery is possible.

  The object of the present invention is also a method for extracting, cooling and recovering heavy ash energy as described so far with respect to plant 1.

  So far, the present invention has been described with reference to preferred embodiments. There may be other embodiments that are at the heart of the same invention, and all are intended to be within the scope of the following claims.

Claims (41)

In particular, heavy ash extraction and cooling, with the recovery of the type of thermal energy that can be used in connection with the combustion chamber, for large quantities of heavy ash streams, for example from solid fossil fuels, in energy generation plants A plant (1) that
(A) extraction and conveying means (9, 6) for extracting and conveying heavy ash coming from the combustion chamber (100);
(B) a cooling system (10, for cooling the heavy ash) arranged in the extraction and transport means (9, 6) and capable of supplying cooling air in the extraction and transport means (9, 6) 11, 19, 17, 12), wherein the overall arrangement is such that at least a part of the cooling air can be introduced into the combustion chamber (100) from its bottom. 10, 11, 19, 17, 12),
(C) pressure shut-off means (8) capable of performing an atmosphere separation between the first environment (9) and the second environment (6) of the extraction and transport means (9, 6), The first environment (9) is connected to the atmosphere of the combustion chamber (100), and the second environment (6) is connected to an air / smoke exchanger (102) or its air inlet by an air injection duct (50; 57). Pressure shut-off means (8), which can be connected to
(D) supplying a portion of the cooling air into the air injection duct (50; 57) to the air / smoke exchanger (102) or into the inlet of the air / smoke exchanger (102); Means (51);
(E) control means capable of executing activation of pressure shutoff of the environment according to the temperature and / or flow rate of the ash;
A plant (1) comprising:   The cooling system (10, 11, 17, 19, 12) is air / water dual type, and the control means performs water cooling activation according to the temperature and / or flow rate of the heavy ash. The plant (1) according to claim 1, which is capable.   The overall arrangement is such that under the pressure separation conditions of the environment (9, 6), the cooling system (10, 11, 17, 19, 12) has a heavy ash flow in the first environment (9). The cooling air supply according to claim 1 or 2, wherein the cooling air supply can be carried out countercurrently with respect to each other and in parallel flow with respect to the heavy ash flow in the second environment (6). Plant (1).   The said control means comprises a temperature and / or flow rate sensor of said heavy ash arranged in said extraction and conveying means (9, 6, 13) and / or in said pressure shut-off area (8). The plant (1) according to any one of 3 above.   The plant (1) according to claim 4, wherein the temperature and / or flow rate sensor of the heavy ash is arranged in a terminal area of the extraction and conveying means (6, 13).   The plant (1) according to claim 5, wherein the temperature and / or flow sensor is arranged in the heavy ash discharge.   The plant (1) according to any one of claims 1 to 6, wherein the control means comprises a load sensor arranged in the pressure shut-off region (8).   The control means is adapted so that the cooling air flow entering the combustion chamber (100) from the bottom does not exceed a predetermined total amount of combustion air, preferably equal to about 1.0-1.5%. 9. Plant (1) according to any one of claims 1 to 7, wherein a separation of 9, 6) can be carried out.   The said supply means (51) can connect the air injection duct (50; 57) to the second environment (6) substantially downstream of the cooling process. Plant (1) according to one paragraph.   10. The supply means (51) according to any one of the preceding claims, wherein the supply means (51) flows into the air injection duct (50; 57) upstream of a fan (54, 58) for increasing the air head. Plant (1).   The plant (1) according to claim 10, wherein the supply means (51) flows into the air injection duct (50) upstream of a secondary air fan (54).   The means (150) for adjusting the flow of air introduced into the air injection duct (50; 57) from the supply means (51), arranged in the supply means (51). The plant (1) according to any one of 11 above.   The pressure shut-off means comprises means (150) for interrupting / enabling the supply means (51) controlled by the control means to perform the environmental separation (9, 6) when necessary. The plant (1) according to any one of claims 1 to 12.   The plant (1) according to any one of the preceding claims, wherein the control means comprises one or more temperature sensors arranged in the supply means (51).   A first extraction unit (9) in which the extraction and conveyance means is arranged or can be arranged immediately downstream of the combustion chamber (100), and a second conveyance arranged downstream of the first unit (9) A unit (6), wherein the pressure shut-off means (8) can provide a pressure separation between the first extraction unit (9) and the second transport unit (6). The plant (1) according to any one of 14 above.   The plant (1) according to claim 14 or 15, wherein the control means can control the speed of at least one of the extraction and transport units (9, 6).   The pressure shut-off means (8) comprises means capable of generating a heavy ash head between the two environments (9, 6) and capable of performing the pressure separation of the environments. Item (1) according to any one of Items 1 to 16.   18. Plant (1) according to claim 17, wherein the pressure shut-off means comprises storage means (8) capable of accommodating heavy ash that produces the head.   19. Plant (1) according to claim 18, wherein the pressure shut-off means comprises a hopper (8) capable of accommodating heavy ash that produces the head.   The plant (1) according to any one of claims 17 to 19, wherein the control means comprises one or more level sensors (7) arranged on the head.   Means for mixing heavy ash (2), arranged in the heavy ash discharge and capable of completing the heavy ash cooling process, and supplying cooling air and optionally steam from said mixing means (2) 21. The plant (1) according to any one of claims 1 to 20, comprising means for feeding to the means (51). In particular, a method for extracting and cooling heavy ash from a combustion chamber for a large amount of heavy ash generated from, for example, fossil fuel in an energy generation plant,
(A) extracting the heavy ash from the combustion chamber (100, 105);
(B) Supply cooling air along the extraction and transfer path (9, 6, 13) and introduce at least a portion of the cooling air into the combustion chamber (100, 105) from its bottom downstream of the cooling process Cooling the heavy ash along the extraction and transport path (9, 6, 13),
(C) Depending on the temperature and / or flow rate of the heavy ash, the pressure cutoff between the first environment (9) and the second environment (6) arranged along the extraction and transport path is selectively performed. A step of starting, wherein the first environment (9) is arranged immediately downstream of the combustion chamber (9) and the second environment (6) is arranged downstream of the first environment (6); An air inlet duct (50; 57) of the air / smoke exchanger (102) or an air inlet of the air / smoke exchanger (102);
(D) Depending on the temperature and / or flow rate of the heavy ash, a portion of the cooling air is passed into the air inlet duct (50; 57) of the air / smoke exchanger (102) or to the air / Supplying to the air inlet of the smoke exchanger (102);
Including methods.   The method according to claim 22, wherein the cooling step (b) is a double air / water type, and the water cooling is started according to the temperature and / or flow rate of the heavy ash.   24. A method according to claim 22 or 23, wherein step (b) performs an activation of water cooling in the second environment (6).   The cooling step (b) is countercurrent to heavy ash flow in the first environment (9) under the pressure separation conditions of the environment (9, 6) and in the second environment (6). The method according to any one of claims 22 to 24, wherein the supply of cooling air is carried out in parallel to the heavy ash flow.   26. The temperature and / or flow rate detection of the heavy ash performed in the extraction and transport path (9, 6, 13) and / or in the pressure shut-off region (8). The method according to one item.   27. The method according to claim 26, wherein the detection of the temperature and / or flow rate of the heavy ash is carried out in the terminal area of the extraction and transport path (6, 13).   28. The method of claim 27, wherein the detection of temperature and / or flow rate is performed at the heavy ash outlet.   29. A method according to any one of claims 22 to 28, wherein load detection performed in the pressure shut-off region (8) is performed.   In step (c), the cooling airflow cooling air entering the combustion chamber (100) from the bottom does not exceed a predetermined total amount of combustion air, preferably equal to about 1.0-1.5%. 30. A method according to any one of claims 22 to 29, wherein the environmental separation (9, 6) is performed.   23. The supply of the air / smoke exchanger (102) to the air injection duct (50) takes place starting from the second environment (6) substantially downstream of the cooling process. The method according to any one of -30.   The supply of the air / smoke exchanger (102) to the air injection duct (50; 57) causes the outflow to the duct (50; 57) upstream of the fan (54, 58) which increases the air head. 32. A method according to any one of claims 22 to 31 provided.   33. The supply of the air / smoke exchanger (102) to the air injection duct (50) provides an outflow to the duct (50) upstream of a secondary air fan (54). the method of.   The adjustment of the air flow supplied to the air inlet duct (50; 57) in the air / smoke exchanger (102) or to the air inlet of the air / smoke exchanger (102) is performed. The method according to any one of 22 to 33.   In step (c), the pressure shut-off is to the air injection duct (50; 57) in the air / smoke exchanger (102) or to the air inlet of the air / smoke exchanger (102). 35. A method according to any one of claims 22 to 34, obtained by means for interrupting / enabling the supply of cooling air.   Means (51) capable of performing the supply to the air inlet duct (50; 57) in the air / smoke exchanger (102) or to the air inlet of the air / smoke exchanger (102). 36. The method according to any one of claims 22 to 35, wherein the temperature detection performed in is performed.   A first extraction section (9) disposed immediately downstream of the combustion chamber (100) and a second conveyance section (6) disposed downstream of the first section (9); In the step (c), the pressure interruption is obtained between the first extraction unit (9) and the second transport unit (6). The method described.   38. A method according to claim 36 or 37, wherein step (c) performs control of the ash extraction and / or transport speed along the path.   The step (c) performs the generation of heavy ash head between the two environments (9, 6), capable of performing the pressure separation of the two environments (9, 6); 39. A method according to any one of claims 22 to 38.   40. The method of claim 39, wherein step (c) performs level detection of the head.   Adopted by the mixing in heavy ash mixing and cooling air, and possibly in the air injection duct (50; 57), which takes place in the heavy ash discharge and can complete the heavy ash cooling process 41. The method according to any one of claims 22 to 40, wherein the method comprises performing a supply of steam generated or generated.

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