JP2011038667A - Oxygen combustion plant and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten a starting time and to reduce an amount of carbon dioxide released to the outside of a plant in starting the oxygen combustion plant. <P>SOLUTION: In this oxygen combustion plant having a combustion device constituted by disposing a pipe for guiding carbon dioxide from a pipeline to the oxygen combustion plant in the oxygen combustion plant, and burning oxygen supplied from an oxygen manufacturing device, a combustion exhaust gas and a fuel, a carbon dioxide recovering device for recovering carbon dioxide from the produced combustion exhaust gas, the pipeline for transferring carbon dioxide to an another place, and a pipe connected to the pipeline, a carbon dioxide pushing-out line for distributing carbon dioxide to the pipeline, and a carbon dioxide taking-in line for guiding carbon dioxide from the pipeline to the oxygen combustion plant, are further disposed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an oxyfuel combustion plant used in a thermal power plant or the like, and an operation method thereof.

  A boiler device, which is a combustion plant provided in a power plant or the like, generates water by heating water with heat generated by burning fuel and air and driving a steam turbine to generate electricity. The boiler device can use many kinds of fuels, but it is less efficient than the gas turbine combined cycle power generation device and emits a large amount of carbon dioxide. Carbon dioxide is considered to be a cause of global warming, and it is required to separate and collect the carbon dioxide generated by the combustion of the boiler and store it so as not to diffuse into the atmosphere.

  In boiler apparatus for separating and recovering carbon dioxide, and air combustion system for burning fuel and air and oxygen combustion method for burning oxygen separated from the fuel and the air. In the air combustion method, the main components of the exhaust gas after combustion are nitrogen and carbon dioxide, and high energy is required to separate carbon dioxide therefrom. On the other hand, in the oxyfuel combustion method, most of the product gas generated by combustion is carbon dioxide, so that the energy for separating carbon dioxide from the exhaust gas is low.

  Further, the oxyfuel combustion method has an advantage that thermal NOx generated by oxidation of nitrogen in a high temperature field is not generated because nitrogen is separated from the air. On the other hand, when pure oxygen is used in the oxyfuel combustion method, the flame temperature becomes high and there is a possibility of damaging the boiler furnace water wall. For this reason, a method of mixing carbon dioxide or moisture with oxygen has been proposed.

  In addition, as described in Patent Document 1, at the time of startup is combusted with air, the combustion method to shift to oxygen combustion is generally used thereafter.

JP 2001-336736 A

  In an oxyfuel combustion plant, air may enter a duct, a furnace, an exhaust gas purification device, or the like in the plant at the time of new installation or startup after a maintenance suspension, or the concentration of carbon dioxide in the plant may be low. In this case, it is inefficient to separate carbon dioxide with much nitrogen in the exhaust gas. In addition, in the combustion system that switches the combustion state from air combustion to oxyfuel combustion, the start-up time becomes longer when shifting to oxyfuel combustion after increasing the carbon dioxide concentration in the plant, and much carbon dioxide is required before switching to oxyfuel combustion. Could not be recovered and was discharged outside the plant.

  The object of the present invention is to shorten the start-up time and reduce the amount of carbon dioxide released outside the plant in starting up an oxyfuel combustion plant.

  The present invention includes a combustion device that burns fuel from oxygen supplied from an oxygen production device and combustion exhaust gas, a carbon dioxide recovery device that recovers carbon dioxide from combustion exhaust gas generated by combustion, and a carbon dioxide recovery device that recovers carbon dioxide. In an oxyfuel combustion plant having a pipeline for transferring carbon dioxide to the outside of the oxyfuel combustion plant, and a pipe connecting the combustion device and the pipeline, the carbon dioxide is interposed between the carbon dioxide recovery device and the pipeline. A carbon dioxide extrusion line for sending from the oxyfuel combustion plant to the pipeline is provided, and a carbon dioxide intake line for returning a part of the carbon dioxide from the pipeline to the oxyfuel combustion plant is provided.

  Further, the combustion apparatus is characterized by being in a state filled with a mixed gas of carbon dioxide supplied from the carbon dioxide intake line and oxygen supplied from the oxygen production apparatus at the time of startup.

  In addition, a gas concentration measuring device for measuring the gas concentration of the mixed gas is installed in the combustion device.

  In addition, an exhaust gas purification device that purifies the exhaust gas of the combustion device and an exhaust gas circulation line that circulates the gas processed by the exhaust gas purification device to the combustion device are provided, and the exhaust gas circulation line is connected to the carbon dioxide intake line It is characterized by doing.

  In addition, an on-off valve is installed in the carbon dioxide intake line, and a pressure measuring device for measuring the pipeline pressure in the carbon dioxide intake line between the on-off valve and the pipeline is provided.

  The carbon dioxide intake line between the on-off valve and the combustion device is provided with a pressure measuring device.

  Moreover, an on-off valve is installed in the carbon dioxide intake line, and a gas concentration measuring device is provided in the carbon dioxide intake line between the on-off valve and the pipeline.

  The oxygen production apparatus has a compressor that compresses air during oxygen production, and a decompression device is installed in a carbon dioxide intake line connected to the pipeline, and the decompressed carbon dioxide supplied from the pipeline The heat exchange is performed between the carbon dioxide intake line that circulates through the compressor and the compressor of the oxygen production apparatus.

  Further, the carbon dioxide recovery device has a compressor for compressing carbon dioxide, and an on-off valve is installed in the carbon dioxide extrusion line between the pipeline and the compressor, and the carbon dioxide extrusion line downstream of the on-off valve And a heat exchange means for exchanging heat between the compressor of the carbon dioxide recovery device.

  Further, the compressor of the carbon dioxide recovery device is configured to generate power by reversely rotating with the carbon dioxide of the pipeline.

  In addition, an expansion turbine that generates power by being driven by carbon dioxide in the pipeline is installed in the carbon dioxide intake line.

Furthermore, a combustion device that burns fuel from oxygen supplied from the oxygen production device and combustion exhaust gas, a carbon dioxide recovery device that recovers carbon dioxide from the combustion exhaust gas generated by combustion, and transports the recovered carbon dioxide to the outside of the plant Exhaust gas for purifying exhaust gas from the combustion device, including a pipeline that performs carbon dioxide, a carbon dioxide extrusion line that sends carbon dioxide to the pipeline, and a carbon dioxide intake line that guides carbon dioxide from the pipeline to the oxyfuel combustion plant In the operation method of the oxyfuel combustion plant in which the purification device and the exhaust gas circulation line for circulating the gas processed in the exhaust gas purification device to the combustion device are provided, and the exhaust gas circulation line is connected to the carbon dioxide intake line,
A gas branch is provided upstream of the connection point of the carbon dioxide intake line downstream of the exhaust gas purification device, a circulation gas flow rate adjustment device, a chimney and a chimney flow rate adjustment device are provided downstream of the gas branch, and the exhaust gas purification device A carbon dioxide concentration measuring device downstream of
If the measured value of the carbon dioxide concentration measuring device is lower than the reference value, the circulating gas flow rate adjusting device and the chimney flow rate adjusting device are adjusted so that the circulating gas flow rate is small and the chimney flow rate is large, and the carbon dioxide concentration measurement is performed. If the measured value of the apparatus is higher than the reference value, the circulating gas flow rate adjusting device and the chimney flow rate adjusting device are adjusted so that the exhaust gas circulation flow rate is large and the chimney flow rate is small.

  According to the present invention, in the oxyfuel combustion plant, by installing the carbon dioxide intake line for taking in carbon dioxide from the pipeline at the time of startup, the startup time of the oxygen combustion plant can be shortened, and further the amount of carbon dioxide emission can be reduced. It has an unprecedented effect.

It is a block diagram which shows the structure of the oxyfuel combustion plant which concerns on Example 1 of this invention. It is a graph which shows the gas concentration change at the time of starting of the conventional oxygen combustion plant. It is a graph which shows the gas concentration change at the time of starting of the conventional oxygen combustion plant. It is a graph which shows the gas concentration change at the time of starting of the oxyfuel combustion plant of this invention. It is a graph which shows the gas concentration change at the time of starting of the oxyfuel combustion plant of this invention. It is a block diagram which shows the structure of the oxyfuel combustion electric power generating apparatus of Example 2 of this invention. It is a block diagram which shows the structure of the oxyfuel combustion plant of Example 3 of this invention. It is a block diagram which shows the structure of the carbon dioxide collection apparatus of this invention Examples 4 and 5. FIG. It is a block diagram which shows the structure of the oxyfuel combustion plant of Example 6 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, piping or a line represents piping in the plant, and a pipeline represents a large-capacity pipe communicating between the inside and outside of the plant. Further, the upstream of the piping means the high pressure side or the gas supply side of the piping system, and the downstream means the low pressure side or the supplied side of the piping system.

  FIG. 1 shows an embodiment 1 of an oxyfuel combustion plant in which the present invention is applied to a power plant. In the oxyfuel power generation plant 18, fuel is supplied from the fuel supply device 5 to the oxyfuel power generation device 1, and oxygen is supplied from the oxygen production device 2. Although there is no restriction | limiting in particular in the fuel used with the power plant of this invention, Coal, oil, gas, biomass fuel, etc. can be used. For the combustion of fuel, oxygen produced by the oxygen production apparatus 2 is mainly used, and air is also used supplementarily.

  If only oxygen is burned as fuel and oxidant, the combustion temperature can be very high and damage the furnace water wall. Therefore, in oxyfuel combustion, another medium such as carbon dioxide or water is mixed. In this embodiment, carbon dioxide is supplied from the mixed gas line 27 to the oxyfuel combustion power generation apparatus 1. A gas concentration measuring device 45 that measures the concentration of oxygen and carbon dioxide is provided inside the oxyfuel combustion power generation apparatus 1.

  In the oxyfuel combustion power generation apparatus 1, steam is generated from thermal energy obtained by combustion, and electric energy is obtained by driving a steam turbine and a generator (not shown). Exhaust gas generated by combustion in the oxyfuel combustion power generation apparatus 1 is discharged through the exhaust gas line 31 by the fan 6. The main components of the exhaust gas are carbon dioxide, oxygen, nitrogen, water, nitrogen oxide, sulfur oxide and the like.

  The flow of the exhaust gas is branched into the exhaust gas purification device 3 and the bypass circulation line 28. Gas flow into the bypass circulation line 28 is adjusted by dampers 29 (flow regulating valve), the gas flow rate to the exhaust gas purifying device 3 is adjusted by the damper 30. When the exhaust gas is clean, the damper 29 is opened, the output of the fan 32 is increased, and the flow rate of the bypass circulation line 28 is increased. Thus, large separate system path is long pressure loss (exhaust gas purifying apparatus 3, the gas circulation line 26, mixed gas line 27) it is possible efficient to reduce the flow rate of.

  The exhaust gas purification device 3 removes and separates harmful substances contained in the gas, such as sulfur oxides, nitrogen oxides, and ash. Further, the moisture concentration in the exhaust gas is adjusted to a value required by downstream equipment (the carbon dioxide recovery device 4, the gas circulation line 26, and the mixed gas line 27). Here, a system is used in which the water temperature is reduced by condensing and removing moisture by setting the gas temperature to 100 ° C. or lower.

  The exhaust gas purified by the exhaust gas purification device 3 is adjusted by the dampers 9 and 10 via the gas branch to adjust the distribution to the carbon dioxide recovery device 4 and the gas circulation line 26, and is required by the oxyfuel combustion power generation device 1. A gas amount is supplied to the gas circulation line 26. The exhaust gas that has not been supplied to the carbon dioxide recovery device 4 is supplied to the mixed gas line 27 through the gas circulation line 26, and circulated and supplied to the oxyfuel power generation device 1 through the fan 11.

  A carbon dioxide concentration measuring device 49 is provided between the gas branch and the damper 10. Here, the carbon dioxide concentration measuring device 49 is provided between the gas branch and the damper 10, but may be provided between the gas branch and the damper 44 or between the gas branch and the damper 9. Is lower than the measured value is a reference value of the carbon dioxide concentration measuring device 49, reducing the flow rate to the carbon dioxide recovery unit 4, increases in the opposite case. Circulation gas flow rate, since it is adjusted to a flow rate required by the oxygen combustion power generator, if the surplus gas is discharged from the chimney 7 by opening a damper 8.

  The exhaust gas whose main component is supplied to the carbon dioxide recovery device 4 is compressed by the carbon dioxide recovery device 4 having a compressor, and the carbon dioxide is sent to the pipeline 15 through the CO2 extrusion line 22. . In the carbon dioxide recovery device 4, oxygen, nitrogen and the like are mainly separated during the compression process, and other than carbon dioxide is released to the atmosphere. The final pressure and temperature of carbon dioxide are adjusted to values designated by the pipeline 15 by the carbon dioxide recovery device 4. Since the volume decreases when the pressure in the pipeline 15 is increased, the diameter of the pipe can be reduced if the flow velocity flowing through the pipeline 15 is the same. The pipeline 15 is a large-diameter pipe that conveys gas inside and outside the plant and has a diameter of 1 to several meters depending on the scale of the plant.

  Various devices are connected to the pipeline 15. The CO2 source, and the like of a similar type oxygen combustion power plant 18, CO2 recovery function with the combustion device 16, CO2 recovery function IGCC 17. Various devices can be connected to the pipeline 15 as long as they have a CO2 recovery function. A part of the carbon dioxide supplied to the pipeline 15 is stored by the CO 2 storage device 19. The storage location can be underground. Further, when there is a storage place far from the pipeline 15, the carbon dioxide is charged into the CO 2 transport device 21 via the CO 2 filling device 20. Carbon dioxide is transported by the CO2 transport device 21 and stored in a suitable place.

  Normally, when the oxyfuel combustion power plant 18 is started, air is mixed in the oxyfuel combustion power generator 1, the exhaust gas line 31, the exhaust gas purification device 3, the gas circulation line 26, the bypass circulation line 28, and the mixed gas line 27. This means that the nitrogen concentration is high. Since the oxyfuel combustion power generation apparatus 1 burns oxygen and fuel, the concentration of nitrogen decreases and the concentration of CO2 increases with time after the plant is started.

  Nitrogen contained in the exhaust gas at the time of startup is discharged from the chimney 7 of the exhaust gas purification device 3 or removed by the carbon dioxide recovery device 4 and discharged from the chimney 33. Nitrogen when discharged from the exhaust gas purifying apparatus 3, since carbon dioxide is released discarded with nitrogen, carbon dioxide recovery rate decreases. Moreover, when nitrogen is discharged | emitted from the carbon dioxide recovery apparatus 4, even unnecessary nitrogen will be compressed and the energy efficiency of a plant will fall.

  In the conventional oxyfuel combustion plant, it takes time until the CO2 concentration becomes constant in order to circulate exhaust gas containing CO2 in order to prevent overcombustion while burning with oxygen after burning with air. A feature of the present invention is that the CO2 intake line 23 is installed to quickly take in carbon dioxide from the pipeline at the time of start-up, thereby shortening the start-up time of the combustion plant.

There are the following two types of combustion start methods for the oxyfuel power plant 18 of the present invention, each of which will be described below.
(1) Gas replacement activation method Before combustion, the gas in the plant is replaced with carbon dioxide and oxygen in advance. The on-off valve 12 of the CO2 intake line 23 is opened, and CO2 is caused to flow to the oxyfuel combustion power plant 18. Oxygen concentration in the plant, the optimum value varies by fuel type and temperature is set between the degree of 0% to 30%. By setting this concentration, prevent or misfire, or explosion that when the fuel such as coal is turned. For example, in the case of oil or lignite that is easy to burn, the oxygen concentration is lowered, and in the case of anthracite that is difficult to burn, the oxygen concentration is raised.

  Setting the oxygen concentration to 0% means replacing all with carbon dioxide. In this case, it is important to note that when the fuel is supplied because the oxygen concentration is low, there is a high possibility that the flame will misfire in the burner. It is necessary to improve flame holding by installing it. Oxygen, nitrogen, and CO2 concentrations are measured at the inlet and outlet of each device, and the start-up procedure is entered when gas replacement is complete.

In order to minimize the amount of carbon dioxide and oxygen used for substitution, it is effective to use the following method.
(Method 1): The damper 24 and the dampers 10 and 8 of the air intake line 25 are closed, and the dampers 35, 29, 30, 9, and 34 are opened. The on-off valve 12 is opened to guide carbon dioxide into the plant. The oxygen supply amount is controlled so that the oxygen concentration at the specified location becomes the specified value.

Alternatively, when it is difficult to measure the average concentration, the flow rate of carbon dioxide is measured from the pressure difference between the pressure measuring devices 14a and 14b, and the oxygen flow rate is determined from the set values of the flow rate of carbon dioxide and the oxygen concentration. All the gas in the plant is discharged from the chimney 33 of the carbon dioxide recovery device 4. The fan 32 is operated to replace the gas in the exhaust gas circulation line 28. The gas flow of the fan 32 may be in the forward direction, but can be replaced in a short time the gas in the exhaust gas circulation line 28 when the reverse direction. In order to replace the gas in the plant in a short time, it is preferable that there is no circulation line and one-through is performed.
(Method 2): In (Method 1), the gas in the gas circulation line 26 cannot be replaced. Therefore, first, the dampers 35 and 9 are closed, and the dampers 10, 34 and 44 are opened. Then, the on-off valve 12 is opened, and the gas circulation line 26 and the inside of the carbon dioxide recovery device 4 are replaced with CO2. Thereafter, by moving to (Method 1), the gas in the gas circulation line 26 can also be replaced. When the volume of the gas circulation line 26 is large, (Method 2) may be selected.
(Method 3): In this method, since the CO2 intake line 23 is also used as the CO2 extrusion line 22, the CO2 intake line 23 and the on-off valve 12 are not necessary. The dampers 34 and 9 are closed, and the dampers 44, 10, 35, 29, 30 and 8 are opened. The on-off valve 36 of the CO2 extrusion line 22 is opened to allow the carbon dioxide to flow backward. At this time, equipment can be simplified if the inside of the carbon dioxide recovery device 4 can flow backward. When the internal pressure loss of the carbon dioxide recovery device 4 is large and backflow is difficult, a backflow line may be provided inside the carbon dioxide recovery device 4. In this case, unreplaced gas remains in the carbon dioxide recovery device 4.
(Method 4): In this method, close the damper 9,34, open the damper 44,10,35,29,30,8. Next, the on-off valve 36 installed on the downstream side of the carbon dioxide recovery device 4 and the on-off valve 12 installed on the CO 2 intake line 23 are opened to cause the carbon dioxide to flow backward. Carbon dioxide flows through the mixed gas line 27, the oxyfuel combustion power generator 1, the exhaust gas line 31, the exhaust gas purification device 3, and the chimney 7. Since carbon dioxide is taken in through the two routes of the CO2 extrusion line 22 and the CO2 intake line 23, the inside of the plant can be replaced with carbon dioxide in a short time.

Gas replacement by methods 1 to 4 may be performed after the plant startup command is issued, but the gas may be replaced prior to plant startup. Startup time can be shortened. However, if the power plant is not started, there is a possibility that the filled carbon dioxide is wasted leaking outside the plant.
(2) Air Combustion Start-up Method When it is necessary to start power generation in a shorter time than the start-up time of the oxygen production apparatus 2, it is preferable to use air for combustion at start-up. In this case, the dampers 24, 30, and 8 are opened, and the dampers 9 and 35 are closed. Carbon dioxide is discharged from the chimney 7 of the exhaust gas purification device 3 without being recovered.

  If recovery efficiency may be low, close the damper 8, open the damper 9, the gas supply to the carbon dioxide recovery device 4, to recover carbon dioxide. Although it can be operated up to a load of 100% by air combustion, it is preferable to use it at a low load because carbon dioxide cannot be efficiently recovered. In low load, keep warm oxyfuel power generator 1 and an exhaust gas purifying apparatus 3, air separation unit 2 can increase the load was started.

  When the oxygen production apparatus 2 is activated and the oxygen flow rate increases, switching to oxyfuel combustion is performed by the following method. The amount of oxygen input from the oxygen production apparatus 2 and the amount of oxygen contained in the air input from the air intake line 25 are determined from the amount of fuel supplied and the amount of oxygen required by the fuel (stoichiometric ratio). That is, when the oxygen flow rate is increased, the air flow rate is decreased.

  In order to switch from air combustion to oxyfuel combustion in a short time (that is, to lower the nitrogen concentration in the plant), the gas flow is controlled as follows. Close the dampers 9 and 10 and open the damper 35. The on-off valve 12 is opened and carbon dioxide is taken into the plant. The amount of carbon dioxide is adjusted so that the oxygen concentration falls within a predetermined range. When the oxygen flow rate increases, the air flow rate decreases, and there is a condition for burning only with oxygen. After such a condition is reached, nitrogen does not enter the plant, so the nitrogen concentration decreases and the carbon dioxide concentration in the exhaust gas line 31 increases.

  After the carbon dioxide concentration reaches a specified value, the damper 8 is closed and the dampers 9 and 10 are opened. Since a gas containing high-concentration carbon dioxide flows through the gas circulation line 26, the flow rate of carbon dioxide entering from the CO2 intake line 23 is reduced. Finally, the carbon dioxide entering from the CO2 intake line 23 becomes 0, and the operation is performed independently from the pipeline 15.

  It is considered that the pipeline 15 is connected to various devices and is not in an optimum state for the oxyfuel power plant. If the gas temperature, pressure, composition, etc. in the pipeline 15 exceed the range assumed for the oxyfuel power plant, the power plant may fail. In such a case, carbon dioxide is not taken in from the CO2 intake line. For this purpose, the gas measuring device 13 may be provided in the CO 2 intake line 23. The gas measuring device 13 has a function of detecting the temperature, concentration, component, ash concentration, etc. of the gas taken in from the pipeline.

  If the gas temperature is high, the equipment may become hot and fail. If the temperature is low, the on-off valve or damper may freeze and freeze.

  Although carbon dioxide should have flowed through the pipeline 15, there is a possibility that another gas flows by mistake, and it is necessary to close the on-off valve 12 at this time as well. For example, when a gas having a high oxygen concentration flows, the combustion temperature rises and the combustion apparatus may be burned. Further, when a gas having a high concentration of sulfur oxide flows, the possibility of corrosion increases. By measuring the gas composition, these problems can be avoided.

  Also, if it contains such ash into the gas in the pipeline 15, the pipe needs to close the opening and closing valve 12 for preventing clogging.

  When the pressure in the pipeline 15 is low, there is a possibility that the gas of the oxyfuel power generation apparatus flows backward into the pipeline 15. In order to prevent this, the pressure measuring devices 14 a and 14 b may be attached to the CO 2 intake line 23. When the pressure of the pressure measuring device 14a is lower than that of the pressure measuring device 14b, control is performed so that the on-off valve 12 is not opened. Further, when the pressure difference is low, the supply flow rate of carbon dioxide decreases, so it is better to respond by increasing the output of the fan 11.

  In FIG. 1, pressure measuring devices 14 a and 14 b and a temperature / concentration measuring device 13 are installed only in the CO 2 intake line 23, but in the case where carbon dioxide is caused to flow backward in the CO 2 extrusion line 22, a similar measuring device is used. It is good to install.

  2A and 2B are graphs showing a conventional gas composition simulation. FIG. 2A shows the numerical calculation result of the gas composition at the outlet of the exhaust gas purification device 3 when fuel and oxygen corresponding to a 10% load are supplied and burned from a state where the plant is filled with air. 2B also shows the numerical calculation result of the gas composition at the outlet of the mixed gas line 27 immediately before the oxyfuel power generation apparatus 1.

  In the calculation, each device (gas circulation line 26, mixed gas line 27, oxyfuel combustion power generation device 1, exhaust gas line 31, exhaust gas purification device 3) was simulated with a one-dimensional model, and the concentration was calculated unsteadyly. Each device was divided into 3-5 calculation cells. In the oxyfuel combustion power generation apparatus 1, it is assumed that the fuel and the oxidant burn instantaneously. The output of the boiler that is the object of calculation is 1000 MW. The volume and cross-sectional area of each device were set assuming an actual boiler. The gas temperature of each device is fixed, and is set to 1500 ° C., 300 ° C., 27 ° C., and 27 ° C. in the oxyfuel combustion power generation device, the exhaust gas purification device, the gas circulation line, and the mixed gas line, respectively. Over time, the nitrogen and oxygen concentrations decrease and the carbon dioxide concentration increases. The time required for the nitrogen concentration indicated by the bold line (collection of circles) to be not more than 0.01 (1%) by mass was 1580 seconds. FIG. 2B was almost identical to FIG. 2A.

  3A and 3B are graphs showing a gas composition simulation of the embodiment of the present invention. FIG. 3A shows the calculation result of the gas composition at the outlet of the exhaust gas purification device 3 when carbon dioxide and air used at a 10% load are supplied from a state where the plant is filled with air. This result corresponds to (Method 1) of the present invention. The calculation method is the same as that shown in FIG. The time for the nitrogen concentration to be 1% or less was 810 seconds, and it was confirmed from the numerical calculation that the gas could be replaced in a short time. Being able to start in a short time means reducing the emission of carbon dioxide from the chimney 7. FIG. 3B shows the numerical calculation result of the gas composition at the outlet of the mixed gas line. Oxygen and nitrogen are almost zero, indicating that CO2 in the oxyfuel power plant 18 has been quickly replaced.

  FIG. 4 shows a second embodiment of the present invention when coal is used as fuel. A mixture of circulating gas, air and carbon dioxide flows from the mixed gas line 27. The oxygen supplied from the oxygen production apparatus 2 is mixed with this. The mixing ratio is adjusted by the damper 107. The oxygen concentration after mixing was measured, when I out of the range of concentrations specified, may either stop the oxyfuel power plant 18, or to adjust the flow rate. For example, if the oxygen concentration is too high, the water wall is damaged due to an explosion or an increase in the combustion temperature. Therefore, an operation for decreasing the oxygen concentration is performed. Moreover, since there is a possibility of misfire if the oxygen concentration is too low, an operation for increasing the oxygen concentration is performed to stabilize the flame.

  Coal 100 (100a to 100d) and primary air 108 are supplied to the fuel supply device 5. In the fuel supply device 5, the coal is finely pulverized and conveyed along with the primary air 108. High oxygen concentrations can cause coal to burn during grinding. Therefore, the oxygen concentration is measured, and the oxygen combustion damper 107b is controlled so that the concentration becomes 20 to 30% or less.

  The burner 102 is supplied with primary air 108 and secondary air 109 containing coal supplied from a fuel supply device. In order to reduce NOx discharged from the furnace 110, the burner 102 supplies an amount of oxygen smaller than that required for complete combustion of the fuel, and adds air from the OFA 103 (overfired air port) installed downstream. A two-stage combustion method is used. A damper 105 and a damper 106 are used to adjust the burner secondary air and OFA air flow rate. 101 is a heat exchanger.

  Next, a mechanism for generating steam from heat generated by combustion will be described. The water supplied from the pump 209 passes through the economizer 200 and is supplied to the furnace bottom A of the furnace. Water absorbs heat while flowing through the furnace water wall 201. Only steam is supplied to the primary superheater 202 after reaching the ceiling of the furnace. Thereafter, the steam is heated by the secondary superheater 203 and the tertiary superheater 204 and supplied to the high-pressure steam turbine 205. Further, the steam exiting the high pressure steam turbine, is heated in the reheater 206 to flow a predetermined temperature, it is supplied to the medium-pressure turbine 207. Steam exiting the medium / low pressure turbine is returned to water by a condenser 208.

  In order to replace nitrogen in the plant with carbon dioxide in a short time, it is important to supply gas to all the supply ducts through which air mixed with carbon dioxide and oxygen flows. That is, in a starting method (Method 1) to (method 4), open the damper 104, 105, 106, may be so gas flowing through each duct.

  FIG. 5 shows an example of a method for recovering the energy of carbon dioxide introduced from the CO 2 intake line 23 and improving the energy efficiency of the plant, which is Embodiment 3 of the present invention. The carbon dioxide in the pipeline 15 is high in pressure, and is decompressed by the decompression device 46 when taken into the oxyfuel power plant 18. The gas temperature decreases due to adiabatic expansion during decompression. In the third embodiment, this low temperature is used for cooling the compressor 37 of the oxygen production apparatus 2. 38 is a condenser and 39 is a heat exchanger. Since the efficiency of the compressor 37 increases as the temperature decreases, the efficiency of the entire plant can be increased.

  FIG. 6 shows an energy recovery method in the carbon dioxide recovery device 4 that is Embodiment 4 of the present invention. If carbon dioxide pipeline 15 leads through the carbon dioxide recovery apparatus 4, it opens the on-off valve 36, the on-off valve 40 and close the damper 34. In this case, the compressor 41 is reversely rotated, and a compressor motor (not shown) is reversely rotated to generate power.

  The fifth embodiment of the present invention shows another method of energy recovery in the carbon dioxide recovery device 4 in FIG. The on-off valve 36 is closed, the on-off valve 40 is opened, and the high-pressure carbon dioxide in the pipeline 15 is taken in and expanded. At this time, the CO2 extrusion line 22 also operates as a CO2 intake line. The heat exchanger 42, which also serves as a heat storage device, is kept at a low temperature by carbon dioxide whose temperature has been lowered by adiabatic expansion, and when the carbon dioxide is compressed, a low-temperature heat source is used to increase the efficiency of the compressor.

  FIG. 7 shows a sixth embodiment of the present invention. In order to recover the energy of the high-pressure carbon dioxide in the pipeline 15, an expansion turbine 43 is attached downstream of the on-off valve 12. The expansion turbine 43 is rotated by carbon dioxide gas, thereby generating electric power and recovering energy.

DESCRIPTION OF SYMBOLS 1 ... Oxygen combustion power generation device 2 ... Oxygen production device 3 ... Exhaust gas purification device 4 ... Carbon dioxide recovery device 5 ... Fuel supply device 6 ... Fan 7 ... Chimney 8 ... Damper 9 ... Damper 10 ... Damper 11 ... Fan 12 ... On-off valve 13 ... Temperature / concentration measuring device 14 ... Pressure measuring device 15 ... Pipeline 22 ... CO2 Extrusion line 23 ... CO2 intake line 24 ... Damper 25 ... Air intake line 26 ... Gas circulation line 27 ... Mixed gas line 28 ... Exhaust gas circulation line 29 ... Damper 30 ... Damper 31 ... Exhaust gas line 32 ... Fan 33 ... Chimney 34 ... Damper 35 ... Damper 36 ... Open / close valve 37 ... Compressor 38 ... Condenser 39 .. Heat Exchanger 40 ... off valve 41 ... compressor 42 ... heat exchanger 43 ... expansion turbine 45 ... gas concentration measuring device 46 ... decompressor 49 ... carbon dioxide concentration measuring device

Claims (12)

Combustion device for burning fuel with oxygen and combustion exhaust gas supplied from oxygen production device, carbon dioxide recovery device for recovering carbon dioxide from combustion exhaust gas generated by combustion, and carbon dioxide recovered by the carbon dioxide recovery device In an oxyfuel combustion plant having a pipeline that transfers to the outside of the oxyfuel combustion plant, and a pipe that connects the combustion device and the pipeline,
A carbon dioxide extrusion line for sending carbon dioxide from the oxyfuel combustion plant to the pipeline is provided between the carbon dioxide recovery device and the pipeline, and a part of the carbon dioxide is refluxed from the pipeline to the oxyfuel combustion plant. An oxygen combustion plant characterized by providing a carbon dioxide intake line.   2. The oxyfuel combustion plant according to claim 1, wherein the combustion device is in a state filled with a mixed gas of carbon dioxide supplied from the carbon dioxide intake line at startup and oxygen supplied from the oxygen production device. Oxyfuel combustion plant that features.   3. The oxygen combustion plant according to claim 2, wherein a gas concentration measuring device for measuring the gas concentration of the mixed gas is installed in the combustion device.   2. The oxyfuel combustion plant according to claim 1, further comprising: an exhaust gas purification device that purifies the exhaust gas of the combustion device; and an exhaust gas circulation line that circulates the gas treated by the exhaust gas purification device to the combustion device; An oxyfuel combustion plant, wherein the exhaust gas circulation line is connected to an intake line.   2. The pressure measuring apparatus according to claim 1, wherein an on-off valve is installed in the carbon dioxide intake line, and a pipeline pressure is measured on the carbon dioxide intake line between the on-off valve and the pipeline. An oxyfuel combustion plant comprising:   In oxyfuel combustion plant according to claim 5, the oxygen combustion plants, characterized in that it comprises a pressure measuring device in the carbon dioxide intake line between the combustion device and the on-off valve.   The oxyfuel combustion plant according to claim 1, wherein an on-off valve is installed in the carbon dioxide intake line, and a gas concentration measuring device is provided on the carbon dioxide intake line between the on-off valve and the pipeline. Oxycombustion plant.   2. The oxyfuel combustion plant according to claim 1, wherein the oxygen production apparatus includes a compressor that compresses air during oxygen production, a decompression device is installed in a carbon dioxide intake line connected to the pipeline, and the pipe An oxygen combustion plant, wherein heat exchange is performed between the carbon dioxide intake line that distributes the decompressed carbon dioxide supplied from the line and a compressor of the oxygen production apparatus.   The oxyfuel combustion plant according to claim 1, wherein the carbon dioxide recovery device includes a compressor that compresses carbon dioxide, and an open / close valve is installed in the carbon dioxide extrusion line between the pipeline and the compressor, An oxygen combustion plant comprising heat exchange means for exchanging heat between the carbon dioxide extrusion line downstream of the on-off valve and a compressor of the carbon dioxide recovery device.   The oxyfuel combustion plant according to claim 9, wherein power generation is performed by reversely rotating a compressor of the carbon dioxide recovery device with carbon dioxide in the pipeline.   2. The oxyfuel combustion plant according to claim 1, wherein an expansion turbine that generates electric power by being driven by carbon dioxide in the pipeline is installed in the carbon dioxide intake line. Combustion device that burns fuel with oxygen and combustion exhaust gas supplied from an oxygen production device, a carbon dioxide recovery device that recovers carbon dioxide from combustion exhaust gas generated by combustion, and a pipe that transfers the recovered carbon dioxide to the outside of the plant An exhaust gas purifying apparatus for purifying exhaust gas of the combustion apparatus, comprising a line, a carbon dioxide extrusion line for sending carbon dioxide to the pipeline, and a carbon dioxide intake line for introducing carbon dioxide from the pipeline to the oxyfuel combustion plant And an operation method of the oxyfuel combustion plant in which an exhaust gas circulation line for circulating the gas treated by the exhaust gas purification device to the combustion device is provided, and the exhaust gas circulation line is connected to the carbon dioxide intake line.
A gas branch is provided upstream of the connection point of the carbon dioxide intake line downstream of the exhaust gas purification device, a circulation gas flow rate adjustment device, a chimney and a chimney flow rate adjustment device are provided downstream of the gas branch, and the exhaust gas purification device A carbon dioxide concentration measuring device downstream of
If the measured value of the carbon dioxide concentration measuring device is lower than the reference value, the circulating gas flow rate adjusting device and the chimney flow rate adjusting device are adjusted so that the circulating gas flow rate is small and the chimney flow rate is large, and the carbon dioxide concentration measurement is performed. If the measured value of the apparatus is higher than the reference value, the circulating gas flow rate adjusting device and the chimney flow rate adjusting device are adjusted so that the exhaust gas circulation flow rate is large and the chimney flow rate is low. .

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