JP2971187B2 - Combustion gas desulfurization unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for desulfurizing combustion gas in a combustion furnace such as a commercial or industrial boiler.

[0002]

FIG. 6 shows a conventional combustion gas desulfurization apparatus for a combustion furnace. Limestone (CaCO ₃ ) 12 is supplied to a combustion furnace 10 in which pulverized coal 11 is supplied and burns, and the combustion gas is desulfurized in the furnace. The SO _x content in the exhaust gas discharged from the combustion furnace 10 is further desulfurized by a flue gas desulfurization device 20 that sprays a slurry 21 described later. The slurry 21 is obtained by mixing a part 32 of ash contained in exhaust gas and water 32 in an exhaust gas collected by an electrostatic precipitator (hereinafter referred to as EP) 30 disposed downstream of the flue gas desulfurizer 20 by a mixer 40. Quicklime that has been made and remains in the ash (CaO)
The desulfurization is performed by the slurry.

Here, in order to operate the EP 30 stably, the gas temperature at the inlet and the outlet of the flue gas desulfurization device 20 is set at a temperature sufficiently higher than the saturation temperature.

The remaining portion 33 of the collected ash in the EP 30 is subjected to a predetermined process as EP ash. The gas from which dust has been removed in EP 30 is discharged from the chimney 50 to the atmosphere.

[0005]

In the above-mentioned prior art, the desulfurization rate in the flue gas desulfurization unit was poor for the following reasons.

(1) Quicklime (C) in a flue gas desulfurization unit
The desulfurization shown in the following equation using the slurry of aO) is more effective as the exhaust gas temperature is lower. However, considering the stable operation by EP in the next process, in order to prevent the occurrence of problems such as stickiness due to moisture, the exhaust gas temperature is reduced. Cannot be greatly reduced. CaO + H ₂ O → Ca (OH) ₂ Ca (OH) ₂ + SO ₂ +1/2 O ₂ → CaSO ₄ + H ₂ O (2) In the flue gas desulfurization device, unreacted quicklime after once desulfurization in the combustion furnace (CaO) is used to slurry it and perform desulfurization by gas-liquid reaction. In the quicklime to be slurried, its particles are in a state where pure CaO is surrounded by CaSO ₄ which is a reaction product. Therefore, the reactivity of desulfurization as CaO is very poor.

[0007] The present invention is to solve the above problems of the conventional desulfurization apparatus.

[0008]

SUMMARY OF THE INVENTION According to the present invention, unreacted lime contained in exhaust gas from a combustion furnace collected by an electrostatic precipitator is subjected to desulfurization of a combustion gas using limestone as a desulfurizing agent. In the flue gas desulfurization device for desulfurizing the exhaust gas with the flue gas desulfurization device upstream of the electrostatic precipitator by the slurry, the flue gas desulfurization device is used to remove unreacted lime collected by the electric precipitator. It is composed of a rotary desulfurization unit having a wet crushing unit that crushes into quick lime slurry and a gas-liquid desulfurization unit using the quick lime slurry, and the flue gas supplied from the flue gas desulfurization device to the electric dust collector and the combustion furnace An exhaust gas to be supplied to the flue gas desulfurization apparatus was introduced, and a gas / gas heater for exchanging heat between both exhaust gases was provided.

[0009]

According to the present invention, the flue gas from the combustion furnace supplied to the flue gas desulfurization unit is subjected to heat exchange with flue gas, which has been treated by quick lime slurry and reduced in temperature, in a flue gas desulfurization unit in a gas heater. To lower
The efficiency of desulfurization by quick lime slurry in the flue gas desulfurization unit is improved.

On the other hand, the flue gas discharged from the flue gas desulfurization device heat-exchanges with the high-temperature flue gas discharged from the combustion furnace in the gas / gas heater to raise the temperature, and the temperature of the flue gas is reduced by an electric precipitator (hereinafter referred to as EP).
), The EP is stably operated without generating stickiness or the like due to moisture.

In addition, when unreacted quicklime in the exhaust gas collected by the EP is crushed and slurried by a wet crusher of a rotary flue gas desulfurizer, CaSO ₄ surrounding the surface of the quicklime particles is used. Is crushed and removed from the surface of the quicklime particles, and the desulfurization reaction by the quicklime is improved.

Further, in the gas-liquid desulfurization section of the rotary flue gas desulfurization device, the rotation of the gas-liquid desulfurization device increases the gas-liquid contact efficiency between the limestone slurry and the exhaust gas, thereby improving the desulfurization efficiency.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. This embodiment is obtained by adding an apparatus described below to the conventional desulfurization apparatus for a combustion furnace shown in FIG.
The same reference numerals as in FIG. 6 denote the corresponding parts in FIGS.

In this embodiment, as shown in FIG. 1, the flue gas desulfurization apparatus 60 to which the exhaust gas 13 from the combustion furnace 10 is supplied is a rotary type, and the exhaust gas 13 from the combustion furnace 10 is supplied to a gas / gas heater 70. Then, it is supplied to the upper flue gas desulfurization unit 60. The flue gas 61 discharged from the flue gas desulfurization device 60 passes through the gas / gas heater 70, exchanges heat with the flue gas 13 from the combustion furnace 10, and is supplied to the EP 30 via the flue evaporator 20. It has become so.

As shown in FIGS. 2 and 3, the rotary type flue gas desulfurization apparatus 60 is formed in a cylindrical shape, and shafts 1 at both ends thereof are provided.
11 is rotatably supported by a gantry 109, and one shaft 111 is connected to and rotated by a motor 110.

The interior of the flue gas desulfurization unit 60 is partitioned by a ring-shaped partition plate 104 into a desulfurization chamber 102 which makes gas-liquid contact with the crushing chamber 101. A large number of balls 103 for crushing limestone are accommodated in the crushing chamber 101. Also,
A plurality of bar-shaped lattices 105 extending in the axial direction of the flue gas desulfurization device 60 are provided in the desulfurization chamber 102.
Are provided with a plurality of lifting plates 106 on the inner periphery thereof.
The plurality of lattices 105 are connected to each other by a plurality of connection rods 105a orthogonal to the lattices 105.

As shown in FIG. 4, the flue gas desulfurization unit 60
At the end on the side of the desulfurization chamber 102, a pair of disks 108a and 108b that rotate together with the flue gas desulfurization device 60 are attached so as to be rotatable around the axis 111 of the flue gas desulfurization device 60 at intervals. An annular guide cylinder 110 is provided between the two disks 108a and 108b so as to be in contact with the two disks 108a and 108b, and is provided concentrically with the two disks 108a and 108b. An annular opening 102a of the flue gas desulfurization device 60 is slidably inserted into the guide tube 110, and an exhaust gas discharge hole 1 is provided above the guide tube 110.
12 has a slurry discharge hole 113 at the bottom.

The exhaust hole 112 for the exhaust gas is
Connected to the gas heater 70, and
Numeral 3 is connected to a pump 120, and a part of the slurry from the slurry discharge hole 13 is sprayed into the flue evaporator 20 by the pump 120, and the rest of the slurry is
As No. 2, as described later, it is supplied to a pulverizing chamber 101 of a flue gas desulfurization device 60.

An annular inlet opening 101a is provided at the end of the flue gas desulfurization unit 60 on the side of the pulverizing chamber 101, and a pipe 107 for introducing the exhaust gas 13 from the gas heater 70 so as to surround the inlet opening 101a. Is arranged.
Part of the dust collected in EP 30, water 32, and circulating slurry 62 from the slurry discharge hole 113 are supplied to the pipe 107.

In this embodiment, the exhaust gas 13 desulfurized in the furnace by the pulverized coal 11 and the limestone 12 supplied to the combustion furnace 10 is exhausted by a gas / gas heater 70 to the exhaust gas leaving a rotary flue desulfurization unit 60 described later. The gas 61 is cooled to a temperature close to the saturation temperature, and the cooled gas 71 is led to the rotary flue gas desulfurization unit 60. Rotary flue gas desulfurization unit 60
Along with this gas 71, water 32 for slurrying,
A part 31 of the dust from the EP 30 and a circulation slurry 62 are supplied. The exhaust gas 61 desulfurized by the rotary flue gas desulfurization apparatus 60 as described later is supplied to the gas / gas heater 70 described above.
And is led to the flue evaporator 20. The slurry 21 from the rotary flue gas desulfurization device 60 is sprayed and evaporated on the flue evaporator 20. On top of that, the exhaust gas is E
Dust is introduced into P30, and dust is collected in EP30.
3 is discharged out of the system.

The rotary flue gas desulfurization device 60 is largely divided into a dust slurry crushing chamber 101 containing quick lime (CaO) and a desulfurization chamber 102 as described above. In the crushing chamber 101,
A large number of balls 103 for crushing are housed therein, and the water 32, the dust 31 from the EP 30 and the circulating slurry 6 are contained therein.
2 is supplied to the grinding chamber 101. These water 32, dust 31, and circulation slurry 62 are supplied to a rotary flue gas desulfurization unit 60.
The balls 103 are slurried by the rolling of the balls 103 due to the rotation of CaO, and CaSO ₄ is removed from the surface of the CaO particles,
It becomes a quicklime slurry that can efficiently perform a desulfurization reaction.

Only the slurry overflowing the partition plate 104 enters the desulfurization chamber 102 in the next step. In the desulfurization chamber 102, the lower slurry is scraped up by the grid 105 as the rotary flue gas desulfurization device 60 rotates,
The slurry carried to the upper part by the scraping plate 106 is the grid 1
05 and adhere to the grid 105. In such a situation, the exhaust gas 13 containing SO _x passes therethrough, so that the gas / liquid contact efficiency is improved, and CaSO ₄ is removed from the surface of the particles of quicklime in the slurry as described above. As described above, since the exhaust gas 13 is cooled by the gas heater 70 and its temperature is lowered, the desulfurization rate of the exhaust gas is improved.

As described above, the exhaust gas 13 is supplied to the desulfurization chamber 1.
02, the temperature is lowered by contact with the slurry, and the exhaust gas 61 is supplied to the opening 102a at the end of the desulfurization chamber 102, the guide tube 110, and the guide tube 110.
The gas enters the gas / gas heater 70 through the exhaust hole 112, and exchanges heat with the exhaust gas 13 from the combustion furnace to lower the temperature of the exhaust gas 13 and increase its temperature.

On the other hand, the slurry that has reacted with the exhaust gas 13 in the desulfurization chamber 102 is supplied to the opening 102 at the end of the desulfurization chamber 102, the guide cylinder 110, and the slurry discharge hole 113 of the guide cylinder 110.
, A part of the slurry 21 is sprayed into the flue evaporator 20 by the pump 120 as described above, and the remaining slurry is circulated to the grinding chamber 101 as a circulation slurry 62.

As described above, the exhaust gas 61 heated in the gas heater 70 evaporates the part of the slurry 21 sprayed into the flue evaporator 20 and then introduces it into the EP 30 at a high temperature. Is done. Thereby, the EP 30 can be operated stably without generating stickiness or the like due to moisture.

FIG. 5 shows the relationship between the desulfurization efficiency of the limestone slurry of the flue gas desulfurization device, the outlet temperature of the exhaust gas from the flue gas desulfurization device, and the difference between the saturation temperature at that time. By making the exhaust gas temperature close to the saturation temperature as in the present embodiment, as shown in the figure, the desulfurization efficiency in the flue gas desulfurization device can be significantly increased. Line A in the figure is line B
2 shows a case where a slurry containing a large amount of unreacted CaO is used.

As described above, in this embodiment, the exhaust gas 13 exiting the combustion furnace 10 whose temperature has been lowered by the gas / gas heater 70 is supplied to the rotary flue gas desulfurization unit 70,
Within 0, efficient desulfurization can be performed by quick lime slurry.

The grinding chamber 1 of the rotary flue gas desulfurization unit 70
In 01, CaSO _{4 on the} surface is removed by crushing quicklime particles contained in the ash collected in EP30, and efficient exhaust gas is obtained by gas-liquid contact between the limestone slurry in the desulfurization chamber 102 and the exhaust gas. Thirteen desulfurizations are performed.

Further, the flue gas 61 whose temperature has been lowered by desulfurization in the rotary flue gas desulfurization apparatus 70 as described above is
Since the temperature is increased by the exhaust gas 13 exiting the combustion furnace 10 by the gas heater 70 and is supplied to the EP 30 through the flue evaporator 20, the EP 30 can be operated stably without generating stickiness or the like. it can.

[0030]

Since the present invention has the structure described in claim 1, the following effects can be obtained.

(1) Since the exhaust gas from the combustion furnace is supplied to the rotary flue desulfurization device whose temperature has been reduced in the gas / gas heater, efficient desulfurization can be performed by quick lime slurry.

(2) Exhaust gas exiting the rotary flue gas desulfurization unit is exchanged with exhaust gas from a combustion furnace in a gas / gas heater and supplied to the electric precipitator in a state where the temperature is increased, thereby causing stickiness and the like. The electric precipitator can be operated stably without the need.

(3) The quicklime particles in the ash collected by the electrostatic precipitator are crushed in a wet crusher of a rotary flue gas desulfurizer to remove CaSO _{4 on} the surface thereof, thereby improving desulfurization performance. The obtained quicklime slurry can be obtained.

(4) In the gas-liquid desulfurization section of the rotary flue gas desulfurization unit, efficient gas-liquid contact is performed between the quick lime slurry and the exhaust gas, and the quick lime slurry has an improved desulfurization performance as described above. Therefore, efficient desulfurization of exhaust gas can be performed.

[Brief description of the drawings]

FIG. 1 is a system diagram of one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of the rotary flue gas desulfurization apparatus of the embodiment.

FIG. 3 is a sectional view taken along the line III-III in FIG. 2;

FIG. 4 is an explanatory diagram of an outlet of a desulfurization chamber of the rotary flue gas desulfurization apparatus of the embodiment.

FIG. 5 is a graph showing the effect of the present invention.

FIG. 6 is a system diagram of a conventional combustion gas desulfurization apparatus for a combustion furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Combustion furnace 11 Pulverized coal 12 Limestone 13 Exhaust gas 20 Flue gas evaporator 21 Partial slurry 30 EP (Electric dust collection device) 31 Part of dust 32 Water 60 Rotary desulfurization flue device 61 Exhaust gas 62 Circulating slurry 70 Gas / Gas heater 101 Crushing chamber 102 Desulfurization chamber 103 Ball 104 Partition plate 105 Grid 106 Raising plate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // B02C 17/04 B03C 3/01 Z B03C 3/01

Claims (1)

(57) [Claims] A combustion furnace desulfurizes combustion gas using limestone as a desulfurizing agent, and a slurry of unreacted quicklime contained in flue gas from the combustion furnace collected by the electrostatic precipitator is used in the electric precipitator. In a flue gas desulfurization device for desulfurizing the exhaust gas in the flue gas desulfurization device on the upstream side, the flue gas desulfurization device is a wet type in which unreacted quick lime collected by an electrostatic precipitator is crushed to produce quick lime slurry. A flue gas supplied from the flue gas desulfurization device to the electrostatic precipitator and an exhaust gas supplied from the combustion furnace to the flue gas desulfurization device are constituted by a rotary desulfurization device having a crushing unit and a gas-liquid desulfurization unit using the quick lime slurry. A desulfurization device for combustion gas, comprising a gas heater for introducing exhaust gas and performing heat exchange between the two exhaust gases.