TW201544766A - Fluidized bed boiler and method for enhancing operational efficiency of the same - Google Patents

Abstract

A method is used for enhancing the operational efficiency of a fluidized bed boiler. The fluidized bed boiler includes boiler body performing therein a burning operation in a fluidized bed; a fluidizing gas inlet for inputting therethrough an oxygen-containing fluidizing gas into the boiler body so as to fluidize the boiler bed and facilitate burning of fuel; a steam outlet for outputting therethrough steam resulting from the burning of the fuel from the boiler body; and a flue gas outlet for exhausting the flue gas resulting from the burning of the fuel from the boiler body. The method for enhancing the operational efficiency of the fluidized bed boiler includes: detecting an oxygen concentration in the flue gas; feeding a part of the flue gas outputted through the flue gas outlet to the fluidizing gas inlet as the oxygen-containing fluidizing gas together with a primary fluidizing gas; and automatically performing a mathematic operation based on the oxygen concentration in the flue gas and an oxygen concentration in the primary fluidizing gas so as to automatically control the dynamic adjustment of the amount of the primary fluidizing gas.

Description

Fluidized bed boiler and method for improving its operation efficiency

This case relates to a boiler equipment, especially a fluidized bed boiler equipment. The present invention is also directed to a method of improving the operational efficiency of fluidized bed boiler equipment.

A boiler is a device that uses heat released by fuel combustion to heat water through a metal wall to generate steam, thereby converting the chemical energy of the fuel into heat. In general, the combustion efficiency may depend on the three-T theory, the so-called three T, ie, temperature, time, and Turbulent. In other words, the combustion effect depends on the temperature in the furnace, the stagnation time, and the turbulence. For fluidized bed boilers, the biggest advantage is high turbulence.

Today's fluidized bed boilers are mainly divided into bubble fluidized bed boilers and circulating fluidized bed boilers. The air of the bubble fluidized bed boiler is injected from the bottom, the sand bed has a heat transfer tube, and the circulating fluidized bed pot In the furnace, the sand and fuel rise from the bottom of the hearth with the airflow, enter the cyclone and return to the bottom of the hearth, and circulate repeatedly. Regardless of the fluidized bed boiler, the gas passes through the layer of solid particles from bottom to top, and the target of sufficient mixing is achieved by the force of the fluid to achieve high turbulence.

However, in the derate operation, the fuel intake is reduced but the empty bed gas velocity remains unchanged, which causes an increase in the residual oxygen in the flue gas discharged from the boiler stack, in other words, the energy efficiency is lowered. In addition, nitrogen oxides (NOx) such as nitrogen oxides or nitrogen dioxide contained in the flue gas after combustion are emitted to the atmosphere, which is harmful to human nerves and damages the central nervous system of the human body. Long-term inhalation may cause brain damage. Paralysis, hand and foot atrophy and other injuries, so it is one of the targets of air quality monitoring.

In order to improve the above problems, it is urgent to reduce the amount of residual oxygen in the flue gas and reduce the emission of nitrogen oxides.

The invention provides a fluidized bed boiler, wherein the amount of residual oxygen in the flue gas discharged during the load reduction operation is still lower than the regulatory standard of 7.2% or lower, which is superior to the general level.

The invention provides a method for improving the operating efficiency of a fluidized bed boiler, which utilizes flue gas reflux to achieve the purpose of reducing the residual oxygen in the flue gas and reducing the emission of nitrogen oxides.

In one embodiment, the present invention provides a fluidization enhancement The method for operating efficiency of a bed boiler is applied to a fluidized bed boiler, wherein: the fluidized bed boiler comprises: a boiler body for fluidized bed combustion; and a fluidized gas inlet for transporting an oxygenated fluidized gas into the bed The boiler body is configured to perform fluidization of the hearth and combustion of the fuel; a steam outlet for outputting steam generated after combustion from the boiler body; and a flue gas outlet for discharging the flue gas generated after combustion from the boiler body The method for improving the operating efficiency includes: detecting an oxygen concentration in the flue gas; and returning a portion of the flue gas from the flue gas outlet to the fluidizing gas inlet to make the recirculated flue gas together with a feed fluidizing gas The oxygen-containing fluidizing gas; and an automatic calculation using the oxygen concentration in the reflux flue gas and the oxygen concentration in the feed fluidizing gas to automatically control the dynamic adjustment of the intake air amount of the feed fluidizing gas .

In one embodiment, the present invention provides a fluidized bed boiler comprising: a boiler body for causing a fuel to be fluidized bed combustion therein; a fluidized gas inlet device communicating with the boiler body for Delivering a feed fluidizing gas into the boiler body for fluidization of the hearth and combustion of the fuel; a steam output device communicating with the boiler body for outputting steam generated after combustion from the boiler body; a flue gas discharge device communicating with the boiler body for discharging smoke generated after combustion from the boiler body a flue gas reflux device connected between the flue gas discharge device and the boiler body for returning a portion of the exhausted flue gas to the boiler body to provide a fluidizing gas together with the feed fluidizing gas And the detector body is connected to the flue gas discharge device for detecting the concentration of oxygen in the flue gas discharged, and dynamically adjusting the intake air amount of the feed fluidizing gas.

1‧‧‧Boiler body

2‧‧‧ Fluidized gas inlet

3‧‧‧Steam export

4‧‧‧Smoke gas export

5A‧‧‧Return line

5B‧‧‧Return line

6‧‧‧Detector

7‧‧‧ Controller

10‧‧‧Fluidized bed boiler

11‧‧‧ Controller

12‧‧‧Detector

13 , 14‧‧‧ pipeline

100‧‧‧Boiler body

101‧‧‧ Fluidized bed

102‧‧‧Steam output device

103‧‧‧ chimney

T1‧‧‧fuel feed trough

T2‧‧‧ lime feed trough

E1‧‧‧ evaporator

E2‧‧ ‧ economizer

E3‧‧‧Air preheater

E4‧‧‧Outboard heat pipe

E5‧‧‧In-bed heat transfer tube

P1‧‧‧Boiler feed pump

B1‧‧‧ Fluidized gas inlet device

B2‧‧‧Fume emission device

B3‧‧‧Fume gas reflux device

C1‧‧‧ control signal

C3‧‧‧ control signal

D‧‧‧Detection result signal

Qair‧‧‧air intake

Qflue‧‧‧ return air volume

BFW‧‧‧ boiler water

1A is a schematic block diagram of an embodiment of a method of improving the operational efficiency of a fluidized bed boiler in accordance with the present invention.

1B is a schematic block diagram of another embodiment of a method of increasing the operational efficiency of a fluidized bed boiler in accordance with the present invention.

2A is a schematic block diagram of an embodiment of a dynamic control method for improving the operational efficiency of a fluidized bed boiler in accordance with the present invention.

2B is a schematic block diagram of another embodiment of a dynamic control method for improving the operational efficiency of a fluidized bed boiler in accordance with the present invention.

3 is a schematic view of a fluidized bed boiler in accordance with an embodiment of the present invention.

In order to improve the residual oxygen in the flue gas encountered in traditional boilers High and nitrogen oxide emission problems, the present invention uses a part of the flue gas reflux as a fluidizing gas, maintaining the air bed speed unchanged, but the oxygen supply is reduced, and the residual oxygen amount at the furnace outlet can be greatly improved. In addition, due to the partial reflux of flue gas, it also reduces the emission of nitrogen oxides.

Specifically, the method for improving the operating efficiency of the fluidized bed boiler of the present invention replaces a portion of the primary air with the returning flue gas, and controls the ratio of the returning flue gas to the primary intake air with an automatic control system to ensure the amount of air entering the bed and The oxygen supply is a fixed value. The method details will be described below in conjunction with the block diagrams of FIGS. 1A and 1B.

Taking a general fluidized bed boiler as an example, the method mainly comprises: a boiler body 1 for fluidized bed combustion; a fluidized gas inlet 2 for transporting an oxygen-containing fluidized gas into the boiler body 1 for performing a hearth Fluidization and combustion of fuel; a steam outlet 3 that outputs steam generated after combustion from the boiler body 1; and a flue gas outlet 4 from which the flue gas generated after combustion is discharged. The present invention returns a portion of the flue gas discharged from the flue gas outlet 4 to the boiler body 1, for example, another return line 5A to the boiler body 1 (Fig. 1A), or another return line 5B to the fluidizing gas inlet. 2 (Fig. 1B), the oxygen-containing reflux flue gas can be supplied as a part of the oxygen-containing fluidizing gas, together with the feed fluidizing gas, into the boiler body 1 for fluidization of the hearth and combustion of the fuel. In this way, the amount of the fluidizing gas to be fed can be reduced, and the amount of oxygen and nitrogen oxides in the final exhaust gas can be reduced, and the desired amount of steam can be produced, so that the overall operating efficiency can be improved. .

Please refer to FIG. 2A, which is a schematic diagram of an embodiment of further dynamically controlling flue gas recirculation and fluidizing gas intake according to the method of FIG. 1A, wherein the two-line arrow in the figure represents the traveling direction of the pipeline and the pipeline contents. The single-line arrow represents the detection or control signal and its direction. In the present embodiment, in addition to the return line 5A, a detector 6 and a controller 7 are additionally provided. The detector 6 is located between the flue gas outlet 4 and the boiler body 1 for detecting the concentration of oxygen in the flue gas discharged. The controller 7 dynamically adjusts the intake fluid amount of the feed fluidizing gas that is input into the boiler body 1 through the fluidizing gas inlet 2 according to the oxygen concentration in the flue gas measured by the detector 6, and additionally inputs the boiler. The amount of reflux gas of the body 1. Wherein, the feed fluidizing gas and the reflux flue gas comply with the relationship of the following formulas (1) and (2): QT=Qa+Qf (1)

QO=Qa x Ca+Qf x Cf (2) where QT is the total air volume of the fluidizing gas, Qa is the intake air amount of the fluidizing gas of the feed, Qf is the amount of the returning flue gas, and QO is the fluidizing gas. The total oxygen content, Ca is the oxygen concentration of the feed fluidizing gas, and Cf is the oxygen concentration of the reflux flue gas.

In this embodiment, the feed fluidizing gas is air, so Ca is constant, about 0.21. It is of course also possible to use other gases containing different oxygen concentrations, such as negative pressure oxygen, where Ca is 1. In addition, the total air volume QT of the fluidizing gas and the total oxygen content QO of the fluidizing gas are preset values, and therefore, the fluidizing gas intake amount Qa of the feed fluid can be obtained by the uncoupling equations (1) and (2). With the amount of returning smoke Qf.

Please refer to FIG. 2B, which is a schematic diagram of an embodiment of further dynamically controlling flue gas recirculation and fluidizing gas intake according to the method of FIG. 1B. In the present embodiment, in addition to the return line 5B, a detector 6 and a controller 7 similar to those described in the embodiment of Fig. 2A are additionally provided. The intake air amount and the return smoke amount of the feed fluidizing gas of the fluidizing gas inlet 2 are dynamically adjusted in accordance with the oxygen concentration of the reflux flue gas as described above.

The method of improving the operational efficiency of the present invention is further illustrated below using a fluidized bed boiler embodiment in accordance with the present invention. As shown in FIG. 3, the fluidized bed boiler 10 includes a boiler body 100 for causing a fuel therein to perform a combustion reaction in the fluidized bed 101. A fluidized gas inlet device B1 is communicated with the boiler body 100. For conveying a feed fluidizing gas into the boiler body 100 for fluidization of the hearth 101 and combustion of the fuel; a steam output device 102 communicating with the boiler body 100 through the pipeline for extracting from the boiler body 100 is output steam generated after combustion; a flue gas discharge device B2 is communicated with the boiler body through a pipeline 13 for discharging flue gas generated after combustion from the boiler body to a chimney 103; and a flue gas reflux device B3 is connected between the flue gas discharge device B2 and the boiler body 100 through a pipeline 14 for returning a part of the exhausted flue gas to the boiler body 100 to provide a fluidized gas together with the feed fluidizing gas. The boiler body 100 is given. Other non-reflux flue gases are discharged from a chimney 103.

In this embodiment, the boiler body 100 can include, but is not limited to, a fuel feed tank T1, an evaporator E1, a heater E2, an air preheater E3, an outboard heat pipe E4, and a bed heat. The tube E5, and a boiler feed water pump P1, as shown in Fig. 3, are not described herein because they are fluidized bed boiler elements well known to those skilled in the art. In addition, a lime feed tank T2 may also be included as needed to perform desulfurization in the fluidized bed.

The fluidized bed boiler of the embodiment further includes a controller 11 and a detector 12, wherein the controller 11 is signally connected to the detector 12, the flue gas reflux device B3, and the fluidized gas inlet device B1. Between the detector 12 and the smoke exhaust device B2 and the smoke Between the chimneys 103 for gas discharge. The detector 12 detects the oxygen concentration Cf contained in the flue gas, and transmits the detection result signal D to the controller 11, and the controller 11 according to the detection result of the detector 12 (1) And (2) calculating a preferred feed fluidizing gas intake amount Qa and a returning flue gas amount Qf, respectively controlling the fluidizing gas inlet device B1 and the flue gas reflux device B3 with control signals C1 and C3, The desired feed fluidizing gas intake amount Qa and the return flue gas amount Qf are supplied to the boiler body 100.

The detector 12 in this embodiment is disposed between the flue gas exhaust device B2 and the flue gas exhausting chimney 103, but the detector 12 may also be disposed in the pipeline and circuit configuration. The oxygen concentration Cf contained in the flue gas can also be obtained downstream of the flue gas emission chimney 103. In addition, the controller 11 in this embodiment is connected between the detector 12, the flue gas reflux device B3, and the fluidizing gas inlet device B1, and the total air volume QT of the fluidizing gas and the The feed fluidizing gas intake amount Qa and the return flue gas amount Qf are dynamically adjusted before the total oxygen content QO of the fluidizing gas is a preset value. Of course, if different designs are made according to actual needs, different control can be performed under the conditions of equations (1) and (2). For example, if the design is to make the proportion of the return smoke constant, the controller is not connected to control the smoke. Return device B3.

For example, the detector 11 can be an oxygen analyzer; the controller can be a computer system or a microcontroller; the fluidized gas inlet device B1 is a blower having a variable frequency motor that changes the speed. Adjusting the air volume; the feed fluidizing gas is air; the steam output device is a steam drum; the flue gas discharging device B2 is an induced draft fan; the flue gas return device B3 is a blower, which has a variable frequency motor, and is changed by Speed adjustment air volume.

The invention can reduce the residual oxygen content in the flue gas and reduce the emission of nitrogen oxides by using the flue gas reflux, in particular, by using the fluidized bed boiler of the invention, the residual oxygen in the flue gas discharged during the load reduction operation can be lower than The regulatory standard is 7.2%, or lower than the general level. In addition, the method for improving the operating efficiency of a fluidized bed boiler according to the present invention can be dynamically adjusted through a fully automatic control system by modifying the backflow of the existing factory pipeline and installing a detector at a suitable location. Flue gas recirculation and primary air input make it easy to increase the efficiency of fluidized bed boilers.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

1‧‧‧Boiler body

2‧‧‧ Fluidized gas inlet

3‧‧‧Steam export

4‧‧‧Smoke gas export

5B‧‧‧Return line

6‧‧‧Detector

7‧‧‧ Controller

Claims (13)

A method for improving the operating efficiency of a fluidized bed boiler is applied to a fluidized bed boiler, wherein: the fluidized bed boiler comprises: a boiler body for fluidized bed combustion; a fluidized gas inlet for transporting an oxygenated a fluidizing gas enters the boiler body to perform fluidization of the hearth and combustion of the fuel; a steam outlet that outputs steam generated after combustion from the boiler body; and a flue gas outlet that is discharged from the boiler body The generated flue gas; the method for improving the operating efficiency comprises: detecting the oxygen concentration in the flue gas; and returning a part of the flue gas from the flue gas outlet to the fluidizing gas inlet to make the return flue gas and a feed fluid The gas is used together as the oxygen-containing fluidizing gas; and an automatic calculation is performed by using the oxygen concentration in the reflux flue gas and the oxygen concentration in the feed fluidizing gas to automatically control the intake air of the feed fluidizing gas Dynamic adjustment of quantity. The method of improving the operating efficiency of a fluidized bed boiler according to claim 1, wherein the automatic calculation further automatically controls the dynamic adjustment of the amount of returning flue gas. The method of improving the operating efficiency of a fluidized bed boiler according to claim 1, wherein the concentration of oxygen in the fluidizing gas of the feed is a predetermined value. A method of improving the operating efficiency of a fluidized bed boiler according to claim 3, wherein the feed fluidizing gas is air. The method for improving the operating efficiency of a fluidized bed boiler according to claim 1, wherein the oxygen-containing fluidizing gas amount is a predetermined value. The method for improving the operating efficiency of a fluidized bed boiler according to claim 1, wherein the intake air amount of the feed fluidizing gas is obtained by a simultaneous operation according to the following formulas (1) and (2): QT= Qa+Qf (1) QO=Qa x Ca+Qf x Cf (2) where QT is the total air volume of the predetermined fluidizing gas, Qa is the intake air amount of the fluidizing gas of the feed, and Qf is the returning flue gas. The amount, QO is the total oxygen content of the predetermined fluidizing gas, Ca is the oxygen concentration of the fluidizing gas of the feed, and Cf is the oxygen concentration of the reflux flue gas. A fluidized bed boiler comprising: a boiler body for causing a fuel to be fluidized bed combustion therein; a fluidized gas inlet device communicating with the boiler body for conveying a feed fluidizing gas into the a boiler body for performing fluidization of the hearth and combustion of the fuel; a steam output device communicating with the boiler body for outputting steam generated after combustion from the boiler body; a flue gas discharge device, and the boiler body The same is used to discharge the flue gas generated after combustion from the boiler body; a flue gas reflux device is connected between the flue gas discharge device and the boiler body for returning a part of the discharged flue gas to the boiler a body for supplying a fluidizing gas to the boiler body together with the feed fluidizing gas; A detector is connected to the flue gas discharge device for detecting the concentration of oxygen in the flue gas discharged, and dynamically adjusting the intake air amount of the feed fluidizing gas. The fluidized bed boiler of claim 7, wherein the detector is an oxygen analyzer. The fluidized bed boiler of claim 7, further comprising a controller coupled to the detector and the fluidizing gas inlet device for dynamically adjusting the oxygen concentration of the recirculated flue gas The amount of intake air of the feed fluidizing gas. The fluidized bed boiler of claim 9, wherein the controller is further signaled to the flue gas reflux device for dynamically adjusting the flue gas return flow according to the oxygen concentration of the return flue gas. The fluidized bed boiler of claim 9 or 10, wherein the controller is a computer system. The fluidized bed boiler according to claim 9, wherein the fluidizing gas inlet device comprises a blower having a variable frequency motor, and the rotation speed is adjusted according to the control of the controller to change the flow of the fluidizing gas. Gas volume. The fluidized bed boiler according to claim 10, wherein the flue gas reflux device comprises a blower having a variable frequency motor, and the rotation speed is adjusted according to the control of the controller to change the flue gas return flow.