• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    An apparatus for cooling condensate in a boiler plant comprises a condenser (1), which is connected to a condensate cooler (3), through which a duct (4) branching off from a combustion air duct of the boiler is introduced in the boiler. The condensate cooler has a direct heat and mass transfer connection between combustion air and condensate, for cooling the condensate and for heating and moistening the combustion air. A discharge duct (5) for the condensate extends from the condensate cooler (3) for discharging the cooled condensate from the boiler plant.Fig. 1
    公开号:SE1550342A1
    申请号:SE1550342
    申请日:2015-03-23
    公开日:2015-09-29
    发明作者:Joonas Arola；Seppo Tuominiemi
    申请人:Valmet Technologies Oy；
    IPC主号:
    专利说明:

    Summary of the invention lt is an aim of the invention to present an efficient way of cooling condensate to a required level, whereby it is simuitaneousiy possible to recover heat contained in the condensate. To achieve this aim, the method according to the invention is primarily characterized in that part of the combustion air entering the boiler is brought into direct contact with a hot condensate, from which heat and humidity is transferred in direct contact with the combustion air, whereby the condensate is cooled. The condensate can be cooled down to the required level, and it can be discharged. The temperature of the cooled condensate to be discharged is monitored by a temperature sensor, and the cooling power is adjusted, if necessary.
    Only a part of the total amount of air entering the boiler is used in the above mentioned way for cooling hot condensate, not more than 25 vol.% Of the total amount of combustion air. For cooling condensate amounts, 10 vol.% Of the total amount of the combustion air, or less, is normally sufficient. For example, in boilers with secondary air supply in addition to primary air supply, the condensate can be introduced into a cooler-humidifier, through which part of the secondary air of the boiler is passed.
    The discharge temperature level, to which the condensate is cooled and at which it is drained into a water system or a sewage system, is 30 to 40 ° C, but the temperature range between 20 and 30 ° C can also be achieved by the method .
    Advantageously, all the condensate formed from the flue gases of the boiler in the condensation after the separation of solids (electrostatic precipitator, bag filter) and having a temperature of at least 40 ° C is cooled by part of the combustion air in the above described way, and the condensate cooled to the discharge temperature and meeting the requirements for an environmental license is then discharged from the boiler plant. The temperature of the hot condensate to be cooled is 40 ° C or higher, normally from 40 to 75 ° C or from 50 to 75 ° C, depending on the condensing method. The condenser can also be connected to the circulation of district heating water, for transfer of condensing heat to return water of the district heating system.
    The apparatus comprises a condensate cooler, to which the condenser is connected and through which a duct branching off from the combustion air duct of the boiler is introduced in the boiler, where the condensate cooler has a direct heat and mass transfer connection between the combustion air and the condensate, for cooling the condensate and for heating and humidi- fying the combustion air. The humidifier has a discharge duct into a sewage system or a water system.
    Description of the drawinqs ln the following, the method will be described in more detail with reference to the appended drawings, in which Fig. 1 shows the method of the invention in a schematic view.
    Detailed description of preferred embodiments Figure 1 shows an apparatus for condensing flue gases and for cooling condensate in a boiler plant. The apparatus comprises a flue gas condenser 1 where flue gases produced by combustion of fuel in a boiler are condensed.
    A flue gas duct F extends from the boiler through the condenser 1. The flue gas duct F is introduced in the lower part of the condenser. The flue gas is condensed as it is cooled by circulating water which is colder than the dew point temperature and which is flowed through a packed layer 1c in the upper part of the condenser, countercurrently to the flue gases. The dew point temperature of the flue gases is normally 60 to 70 ° C. As the steam contained in the flue gases condenses into liquid in the condenser 1, hot condensate is formed which cannot be discharged as such into a water system or a sewage system. The temperature of the condensate produced by the condenser is normally about 50 to 75 ° C, and it has to be cooled down to a level required for an environmental license. ln the figure, the condenser 1 is a so-called condenser-scrubber, in which previously cleaned flue gases are scrubbed countercurrently, wherein the steam contained in them is condensed. Condensate is formed in the upper part of the condenser 1 when the flue gases are cooled in direct contact with circulating water flowing countercurrently. Condensate from the upper part accumulates on a baffle plate of the condenser, from where it flows along an overflow pipe or the like into the lower part of the condenser. Part of the water accumulated on the baffle plate is circulated as circulating water through a heat exchanger 6, in which it is cooled to cooling water which is colder than the dew point and which can be used for condensing the flue gases again. At equilibrium, the condensate flowing into the lower part of the condenser corresponds to the amount of condensate formed from flue gases in the upper part.
    The condensate flows along the over Ow pipe or the like over Ow system (not shown) onto the bottom of the lower part of the condenser. ln the lower part of the condenser, water, in practice hot condensate, is circulated by a pump P1 from the bottom to a dispenser lb of washing liquid of the scrubber, such as nozzles or the like, for cooling the flue gases. A portion that corre- sponds to the amount of condensate formed in the condenser 1 is conveyed from the washing liquid circulation la along a line 2 to a cooler 3 for the con- densate. From the lower part of the condenser 1, the flue gases flow to the upper part, to the above described condensing and heat recovery step, where they flow upwards through the packed layer 1c and countercurrently with respect to the circulating water which is injected to the packed layer 1c from above. Steam is condensed from the flue gases, and at the same time, heat is transferred from them to the circulating water. Water is accumulated on the bottom of the condensing step (on the baffle plate of the condenser), part of the water being conveyed to the lower part of the condenser and fur- ther away from the condenser to cooling the condensate, as described above , and part being pumped by a pump P2 back to the water circulation 1d through the heat exchanger 6. ln the heat exchanger 6, the water of the water circulation is cooled, and it can be used for heating return water 7 from a district heating system.
    Another alternative for carrying out the condensing in a single step is a so-called tubular condenser, in which flue gases are condensed by indirect heat exchange by applying a cooling liquid. The condensate is conveyed from the tubular condenser to the cooler 3 for the condensate. In the tubular condenser, the flue gases are conveyed through tubes, and return water from the district heating system circulates as the cooling liquid on the jacket side (around the tubes) of the condenser. Water is injected to the flue gases before they are conveyed into the tubes, in order to reach the dew point temperature and to intensify the heat transfer. In both cases, the flue gases are purified from dust before condensing; in other words, the condensate is, in practice, free from solids and does not require clarification. An electrostatic precipitator or a bag filter can be used for cleaning the flue gases. In addition, the flue gases can be purified by sup- plying the boiler with chemicais (for example, sulfur dioxide emissions are controlled by supplying the boiler with lime), or a bag filter can be supplied with an additive.
    The conveying of the condensate from the circulation 1a to the cooler 3 for the condensate can be controlled by means of a sensor L for monitoring the level in the lower part of the condenser 1 and controlling a shut-off valve V in the line 2.
    The cooler 3 for the condensate is a so-called cooler-humidifier, through which a duct 4 of combustion air entering the boiler is passed. Only a part of the combustion air of the boiler is conveyed via the cooler-humidifier, for example not more than 25 vol.% Of the total air amount, normally only vol.% Or less. In Fig. 1, the duct 4 for combustion air is a duct branching off from the duct for secondary air in the boiler. ln the cooler-humidifier, the combustion air and the hot condensate are brought into direct contact. Heat is transferred from the liquid into the com- bustion air, the combustion air entering the boi | er is heated, and the conden- sate is cooled. The condensate is preferably cooled to a temperature of 30 to 40 ° C, at which it can be discharged into a sewage system or a water system.
    Humidity is also transferred from the condensate into the air combustion, which enhances the cooling of the condensate as water is evaporated from the condensate. At the same time, the air combustion is moistened to the dew point. ln this way, the cooler 3 for the condensate can also be used for humidifying the combustion air entering the boiler.
    Structurally, the cooler-humidifier is a tower-like container to whose upper part is brought a hot condensate line 2 above a packed layer 3a in the con- tainer. At the end of line 2, the condensate is sprayed to the packed layer 3a. ln the lower part of the container, below the packed layer 3a, the duct 4 of combustion air is introduced, having a blower B for adjusting the rate of air that flows through the cooler 3 for condensate. The duct 4 of combustion air branches off from the duct of secondary air (not shown) in the boiler, from the pressure side of its main blower, from where the blower B can take the amount of air required for cooling the condensate. The condensate will run through the packed layer 3a, countercurrently with respect to the combustion air which will flow through the packed layer 3a up to the upper part of the container. The duct 4 for combustion air continues from the upper part of the container to the boiler. Having passed through the packed layer and having been heated and moistened by the condensate, the combustion air will flow further from the the cooler-humidifier along the duct 4 to the boiler. The com- bustion air coming from the cooler is pre-heated further in a heat exchanger, by either steam or hot water 11.
    The condensate, having run through the packed layer 3a, has cooled to a temperature close to the dew point of incoming air. The cooled condensate accumulates on the bottom of the container, from where it exits via a dis- charge duct 5. The temperature of the exiting condensate is monitored by a temperature sensor T placed in the discharge duct 5. A signal transmission line S extends from the temperature sensor to a controller C arranged for adjusting an actuator A effective on the temperature, in this case the motor of the blower B for blowing air into the cooler 3. ln this way, an automatic closed (feedback) control loop is provided, by which the temperature of the exiting condensate can be kept within desired limits. By changing the rate of air flowing through the cooler 3, it is possible to adjust the temperature of the exiting condensate. Moreover, the control does not affect the total amount of secondary air entering the boiler, because only a part of the secondary air enters the boiler through the cooler 3 for the condensate.
    The condensate which has cooled down to a temperature in accordance with the environmental license can be discharged from the boiler plant through a discharge duct 5 to a sewer system or a water system, which are indicated by the reference numeral 8. ln the following, we will present examples of some possible values of dimen- sions and balances which should not be understood as limiting the invention: Packed layer in the spray cooler, diameter 1.6 m, height 2.7 m quantity of condensate in 7 kg / s out 6.53 kg / s temperature of condensate in 70 ° C, out 27.5 ° C combustion air rate in 4.78 m3n / s out 5.37 m3n / s temperature of combustion air in 40 ° C out 50.8 ° C humidity of combustion air in 14 g / kg out 93 g / kg The dew point temperature of incoming combustion air used for cooling is 19.2 ° C. The combustion air is taken from the upper part of the boiler house.
    The example shows that hot condensate can be cooled to a temperature even lower than the temperature of incoming air. By the method, it is also possible to cool the condensate to a discharge temperature lower than 30 ° C, for example to the temperature range between 20 and 30 ° C.
    The dimensions and the amounts will depend, among other things, on the size of the boiler, so that the above example should not be considered limiting even in that respect.
    The function of the cooler-humidifier is primarily to treat the hot condensate, but in the same process the combustion air is also heated and moistened.
    Thus, the liquid to be treated in the cooler-humidifier consists solely of water obtained in the condensation of steam from flue gases. However, it is also possible to introduce other hot (at least 50 ° C or higher) water fractions to be treated, which fractions originate from condensed steam, and these can be either cooled separately or mixed with the fraction obtained from the condenser. of flue gas. These other condensates introduced in the cooler-humidifier are indicated with the reference numeral 9. Other such water fractions include, in particular, other condensates of the boiler plant, for example con- densates from a steam turbine, condensates produced in an industrial pro- cess, such as secondary condensates from a pulp mi |, among which condensates obtained from a black Iiquor evaporator form a significant portion.
    Secondary condensates from a pulp mill can be cooied by, for example, combustion air of a bark boiler of a pulp mi | or a corresponding boiler for burning wood based biofuel, by conveying part of the combustion air entering the boiler in contact with the hot condensate.
    A boiler where part of the combustion air is used for cooling the condensate produced by the flue gases of the same boiler is a boiler which burns such solid fuels that produce moist flue gases. Such fuels include biofuels, for example wood chips, peat, bark, and various recycled fuels, as well as coal.
    Also, flue gases produced by a natural gas boiler can be condensed, and the condensate obtained can be treated in the above presented way. The boiler can be a heating boiler, for example a boiler in a district heating plant, or a boilerfor producing heat and electricity.
    The boiler can be of conventional general construction, comprising a furnace arranged to burn the fuel (like some of the solid fuels mentioned above) and arranged to transfer the heat produced by the combustion to heat transfer medium, usually water and / or steam, to boiler tubes in heat transfer contact with the furnace, usually in the form of tube walls around the furnace.
    权利要求:
    Claims (15)
    [1] 1. A method for cooling condensate and for recovering heat from it in a boilerplant, wherein heat is transferred to a flow of a medium from hot liquid con-densed from steam, characterized in that part of the combustion air enteringthe boiler is brought into direct contact with a hot condensate, from whichheat and humidity is transferred in direct contact to the combustion air,whereby the condensate is cooled, and the cooled condensate is discharged.
    [2] 2. The method according to c|aim 1, characterized in that the condensate iscooled by allowing it to flow countercurrently with respect to the combustionair.
    [3] 3. The method according to c|aim 1, characterized in that the condensate isconveyed through a packed layer countercurrently with respect to the com-bustion air.
    [4] 4. The method according to any of the preceding claims, characterized inthat the temperature of the condensate to be discharged is measured, andthe cooling power is adjusted on the basis of the measurement.
    [5] 5. The method according to c|aim 4, characterized in that the cooling poweris adjusted by changing the flow rate of combustion air brought in contactwith the hot condensate.
    [6] 6. The method according to any of the preceding claims, characterized inthat the condensate is cooled to a discharge temperature between 30 and40°C.
    [7] 7. The method according to any of the preceding claims 1 to 5, character-ized in that the condensate is cooled to a discharge temperature between 20and 30°C.
    [8] 8. The method according to any of the preceding claims, characterized inthat the part brought in contact with the hot condensate is at the most25 vol.% of the total amount of combustion air entering the boiler.
    [9] 9. The method according to any of the preceding claims, characterized inthat the condensate is condensate obtained by condensing flue gas.
    [10] 10. The method according to claim 9, characterized in that all the hot con-densate obtained by condensing flue gases of the boiler is cooled by part ofthe combustion air entering the boiler.
    [11] 11. An apparatus for cooling condensate in a boiler plant, comprising a con-denser (1) and a cooler connected to the condenser, for cooling hot conden-sate coming from the condenser and for transferring its heat to a flow of amedium passing through the cooler, characterized in that the condenser isconnected to a condensate cooler (3), through which a duct (4) branching offfrom a combustion air duct of the boiler is introduced in the boiler, whereinthe condensate cooler has a direct heat and mass transfer connectionbetween combustion air and condensate, and a discharge duct (5) for thecondensate extends from the condensate cooler (3) for discharging thecooled condensate from the boiler plant.
    [12] 12. The apparatus according to claim 11, characterized in that the conden-sate cooler (3) comprises a packed layer (3a), a line (2) connecting the con-denser (1) and the condensate cooler (3) ends above the packed layer (3a),a duct (4) branching off from the combustion air duct is introduced below thepacked layer (3a) in the cooler (3), and the duct (4) extends to the boiler fromabove the packed layer (3a).
    [13] 13. The apparatus according to claim 11 or 12, characterized in that thecombustion air duct (4) branches off from the duct for secondary air of theboiler to the cooler (3).
    [14] 14. The apparatus according to any of the preceding claims, characterizedin that the apparatus comprises a closed control loop with a temperaturesensor (T) in measuring connection with the cooled condensate to be dis-charged, and a controller (C) connected to the temperature sensor (T). 11
    [15] 15. The apparatus according to any of the preceding claims, characterizedin that the condenser (1) is a flue gas condenser, through which a flue gasduct (F) of the boiler is passed, for example a condenser-scrubber or a tubu-Iar condenser.
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    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    FI20145295A|FI125778B|2014-03-28|2014-03-28|Method and apparatus for cooling condensate and recovering its heat in a boiler plant|
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