JPS61213406A - Steam boiler - Google Patents

Abstract

PURPOSE:To enable to make complete burning and reduce heat loss by supplying only coarsely crushed coals and combining a boiler having a combustion chamber with a semiburning gasification furnace which burns a part of coals and thereby, gasifies the other part of coals and is connected directly to the combustion chamber of the boiler. CONSTITUTION:A semiburning gasification furnace 3 shaped like a funnel keeps necessary temp. for gasification by burning a part of coarse coals supplied by a coal supply feeder 2 and generates dust having fixed carbon as main component and gas by decomposing thermally the other part of supplied coals. Air nozzles 4 eject necessary amount of air for fluidization and thermal decomposition of coals in the semiburning gasification furnace 3 and are installed at the bottom and the upper side above the bottom of the furnace 3. In a combustion chamber 7 of a boiler 5 which is directly connected to a semiburning gasification furnace 3, dust and gas from the furnace 3 are burnt together in gaseous condition. Secondary air nozzles 6 eject necessary amount air for gaseous burning in the combustion chamber 7 of the boiler 5 and are installed at a connecting part between the combustion chamber 7 and a gas duct 12 and also at the combustion chamber 7 below the former ones respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement of a steam boiler using coal as fuel,
In particular, it relates to a steam boiler in which a semi-combustion gasifier and a combustion chamber of the boiler are directly connected.

(Prior Art) Recently, due to the problem of soaring oil prices and price instability, coal, which is available in an inexhaustible and stable supply and is inexpensive, has been reconsidered as a fuel.

Therefore, among steam boilers, the pulverized coal-fired boilers, stoker-fired boilers, and fluidized bed boilers that have been used in the past are being revived.

In particular, fluidized bed boilers are attracting more attention than other types of boilers because they are capable of reducing NOx through low-temperature combustion and desulfurization through the inclusion of lime.

However, in practice, fluidized bed boilers have the following drawbacks.

(1) Because it relies on low-temperature combustion, there is a lot of unburned coal scattering, resulting in low combustion efficiency.

Scattered unburnt coal is made up of fixed carbon and ash left after the volatile matter has been burned, so it is difficult to reburn it as it is.
A separate high-temperature fluidized bed exclusively for this purpose is required.

(2) There are two methods for feeding coal: one is to spread the coal from above using a spreader, and the other is to push it in from the hearth using air transport. However, the former requires uniform spreading, and uneven distribution can cause combustion. In addition to causing problems, the latter causes severe wear on the air transport pipe and has a complicated structure.

(3) When large pieces of solid coal are introduced, they accumulate at the bottom of the furnace, making complete combustion difficult and difficult to remove.

(4) Inside, an interlayer heat exchanger tube is provided to lower the temperature, but this easily wears out, and it is difficult to take countermeasures against this.

(5) Since the flowing air must be at high pressure, the power consumption of the high-pressure blower is large.

(6) The interior must be partitioned to accommodate partial loads, and the larger the size, the more complex the structure.

Therefore, in order to solve the problems of the fluidized bed boiler as described above, the present inventor manufactured a test device 50 shown in FIG. 2 and conducted an experiment.

In Fig. 2, 51 is a coal feeder, 52 is a road semi-combustion gasifier, 53 is an air nozzle, 54 is a high-pressure blower, 55 is a flue, 56 is a cyclone, 57 is a box, and 58 is a combustion 59 is a forced draft fan, 60 is a secondary air nozzle, and 61 is a chimney.

Coal crushed to about 7 fi or less is supplied to the semi-combustion gasifier 52 by the coal supply feeder 51, and air is supplied to the bottom of the semi-combustion gasifier 52 by the high-pressure blower 54. Blows in from the nozzle 53 in a centripetal direction.

At first, heavy oil is burned by a starting heavy oil burner (not shown) installed in the semi-combustion gasifier 52, and then a part of the coal and heavy oil are co-fired, so that a part of the coal is heated to about 900 ml. When it starts to burn at ℃, turn off the heavy oil burner.

Since the semi-combustion gasifier 52 is supplied with less air than the total amount of air required for burning the coal, the remaining part of the coal is thermally decomposed due to the combustion of a part of the coal in the furnace, and this causes the generation of Gas passes through the flue 56, passes through the cyclone 56, and enters the combustion chamber 5.
Here, the secondary air from the forced draft fan 59 is applied through the secondary air nozzle 60 to combust the gas, and the gas is discharged from the chimney 61. The soot and dust collected by the cyclone 56 accumulates in a box 57 below it.

As a result of experiments, it has been found that such a test device 5o can be used in the following ways.

(1) Although the particle size of the supplied coal is quite large, approximately 7 m or less, the soot and dust collected by the cyclone is mostly of fine particle size called submicron.

This is because, unlike pulverized coal, it is not pulverized in a mill, but is automatically pulverized into very fine particles during thermal decomposition in a semi-combustion gasifier.

In other words, the semi-combustion gasifier plays the role of a mill, and
It does not require large power and complicated accessory equipment systems like a mill.

(2) There is no need to uniformly spread the coal feed or push in the hearth shell.

In other words, since the semi-combustion gasifier is in the form of a load, it is sufficient to simply supply coal using the coal supply feeder.

(3) Temperature control inside the semi-combustion gasifier is approximately 90%
It is only necessary to adjust the amount of air from the air nozzle so as to maintain the temperature at 0°C, and there is no need for complicated heat exchanger tubes in the station.

(4) Since it is sufficient to supply the air required for partial combustion without supplying the entire amount of air required for coal combustion, the capacity of the high-pressure blower can be small, and the power consumption can be reduced.

(5) There is no need to partition the interior or create a complicated structure for partial loads, and it is only necessary to adjust the amounts of coal and air supplied.

(6) The gas generated by thermal decomposition belongs to the low calorie gas category, and has a concentration of about 1000 to 120 QKcal/N-
It is completely natural and can be combusted.

(7) In the semi-combustion gasifier, a complete reduction reaction takes place, so no NOx is generated, and since gas combustion is used during reburning in the combustion chamber, low NOx operation can be easily performed.

Although the test device was found to have the above-mentioned advantages over the conventional fluidized bed boiler, it had the following problems when actually applied.

(1) The soot and dust collected by the cyclone of the test equipment is
The particles are extremely fine and will scatter freely if left in the air.

Therefore, it is difficult to handle when disposing of it, and since it consists of fixed carbon and ash with almost no volatile matter, it is difficult to regasify it as it is.

For this reason, it is problematic to use a cyclone as a test device.

(2) On the other hand, in a typical gasification furnace, the gas generated by thermal decomposition is cleaned to remove soot and dust, resulting in clean gas, which is used as fuel.

However, cleaning removes soot dust with a relatively high calorific value, and also considerably reduces the amount of heat held by the generated gas itself, resulting in a large loss of heat. The problem was that equipment and operation costs were high.

(Problems to be solved by the invention) The present invention was devised in order to solve the above-mentioned problems, and its purpose is to simply crush and supply coal. The object of the present invention is to provide a steam boiler that can completely combust this material and have extremely low heat loss.

(Means for Solving the Problems) The steam boiler of the present invention includes a coal supply feeder that supplies coarsely crushed coal, and a part of the coal from the coal supply feeder that is kept at a temperature necessary for gasification by combustion. A road-shaped semi-combustion gasifier that generates soot and gas mainly composed of fixed carbon by thermally decomposing the remainder of the coal, and air necessary for the flow and thermal decomposition of coal in the semi-combustion gasifier. An air nozzle to blow out, a boiler whose combustion chamber is directly connected to a semi-combustion gasifier, where the soot and gas from the semi-combustion gasifier are simultaneously combusted, and a boiler necessary for gas combustion in the combustion chamber of the boiler. The feature lies in that it is composed of a secondary air nozzle that blows out secondary air.

In other words, a semi-combustion gasifier that burns part of the coal and thermally decomposes the remainder of the coal through the combustion, and a boiler equipped with a combustion chamber are combined, and in particular, the semi-combustion gasifier and the combustion chamber are combined. It is directly connected.

(Function) Coarsely crushed coal is supplied into the semi-combustion gasifier by a coal supply feeder, and air is jetted out by an air nozzle.

Inside the semi-combustion gasifier, the coal is moved by the air ejected from the air nozzle, and a part of the coal is burned to maintain the temperature required for gasification, which allows the remaining coal to burn. is thermally decomposed.

When thermally decomposed, soot and gas mainly composed of fixed carbon are generated, and these are sent to the combustion chamber of the boiler.

In the combustion chamber of the boiler, the soot and dust are simultaneously burned by secondary air sent from a secondary air nozzle.

Steam is generated in the boiler by the combustion gas generated by the gas combustion.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic diagram showing the general structure of a steam boiler according to an embodiment of the present invention.

The main parts of the steam boiler 1 include a coal supply feeder 2, a semi-combustion gasifier 3, an air nozzle 4, a boiler 5, and a secondary air nozzle 6.

The coal supply feeder 2 supplies coarsely crushed coal, and is provided at the middle side of the semi-combustion gasifier 3.

The semi-combustion gasifier 3 burns a part of the coal from the coal supply feeder 2, maintains the temperature required for gasification, and thermally decomposes the remainder of the coal to produce soot and gas mainly composed of fixed carbon. The furnace temperature is maintained at about 900°C.

The air nozzle 4 blows out the air necessary for the flow and thermal decomposition of coal in the semi-combustion gasifier 3, and is provided at the lower part of the semi-combustion gasifier 3 and the side part above this. There is.

The boiler 5 has a combustion chamber 7 directly connected to the semi-combustion gasifier 3, and burns soot and gas from the semi-combustion gasifier 3 at the same time. The combustion chamber 7 and the upper part of the semi-combustion gasifier 3 are connected to a flue 12.

The secondary air nozzle 6 blows out the secondary air necessary for gas combustion in the combustion chamber 7 of the boiler 5, and is used at the joint between the combustion chamber 7 and the flue 12, and at the combustion chamber 7 below. They are provided on each side.

13 is a dust collector, 14 is an induced draft fan, 15 is a chimney, 16 is a forced draft fan, 17 is a high pressure blower, 18 is a gas recirculation draft fan, and 19 to 25 are piping.

Coal is crushed to about 7+a+ or less and is fed into a semi-combustion gasifier 3 by a coal supply feeder 2.

On the other hand, the air from the forced draft fan 16 is converted into hot air by the air heater 11 and then pressurized by the high-pressure blower 17 and is ejected from the air nozzle 4 to the lower part of the semi-combustion gasifier 3.

First, heavy oil is burned in a starting heavy oil burner (not shown) installed in the semi-combustion gasifier 3, and then part of the coal and heavy oil are co-fired, so that part of the coal reaches a temperature of approximately 900°C. When it starts to burn, turn off the heavy oil burner.

Since the air from the air nozzle 4 is less than the total amount of air required for burning the coal, a portion of the coal is burned in the semi-combustion gasifier 3 and the temperature is maintained at about 900°C. This causes the remainder of the coal to be thermally decomposed.

During thermal decomposition, large-particle coal flows up and down many times due to the air ejected from the air nozzle 4 and is automatically pulverized to become soot and gas mainly composed of fixed carbon.

The soot and gas generated in the semi-combustion gasifier 3 are the flue 1
2 and is ejected into the combustion chamber 7 of the boiler 5.

At this time, secondary air supplied from the forced draft fan 16 is ejected from the secondary air nozzle 6 and comes into contact with the secondary air nozzle 6, so that gas combustion occurs.

The burned combustion gas is transferred to the superheater 8 of the boiler 5 → the boiler body 9 → the economizer 10 → the air heater 11 → the dust collector 1
3 → induced draft fan 14 → exhaust through chimney 15.

On the other hand, part of the gas from the outlet of the dust collector 13 is transferred to the pipe 23.
→Gas recirculation fan 18→Piping 24→High pressure blower 17→
It is supplied to the air nozzle 4 via the piping 21, and is also supplied from the gas recirculation fan 18 to the secondary air nozzle 6 via the piping 24→piping 25, thereby reducing NOx.

(Effects of the Invention) As described above, according to the present invention, the following excellent effects can be achieved.

(1) Since the semi-combustion gasifier is directly connected to the combustion chamber of the boiler, the heat capacity of the generated gas can be directly carried into the boiler, and there is no heat loss.

(2) Dust consists of fixed carbon and ash, but it is easily completely combusted in the flame of gas combustion, and there is almost no loss due to scattering of unburned coal.

In other words, when comparing this combustion process with pulverized coal combustion, in the case of pulverized coal combustion, when the coal particles are blown into the furnace from the burner, a gasification reaction occurs first due to the high radiant heat of the coal particles, and then the gas is ignited. The remaining 9 fixed carbon particles glow and burn at high temperatures.

On the other hand, in the case of the present invention, the gas and fixed carbon are already separated in the semi-combustion gasifier9, and the pulverized coal is released into the combustion chamber of the boiler after the first stage of pulverized coal combustion has been completed. Since the gas is ejected, ignition combustion of this gas and fixed carbon can be carried out very easily, and pulverized coal combustion does not require any residence time and can be handled in a small combustion chamber.

(3) Since gas combustion is the main combustion chamber in the boiler, combustion can be performed with a small excess air ratio, and the combustion can be easily controlled by using secondary air, while reducing NOx. I can do it. Of course, NOx is not generated from inside the semi-combustion gasifier.

(4) Desulfurization can be achieved by introducing calcium carbonate into a semi-combustion gasifier or by blowing it into the combustion chamber of a boiler.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the general structure of a steam boiler according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the general structure of a test device previously manufactured and tested by the present inventor. l...Steam boiler 2...Coal supply feeder 3...Semi-combustion gasifier 4...Air nozzle 5...Boiler 6... Secondary air nozzle 7... Combustion chamber application agent Patent attorney Shigeo Iwakoshi and one other procedural amendment (voluntary) May 15, 1985 1, Indication of the case Patent Application No. 60-55513 2 Title of the invention Steam boiler a Relationship to the case of the person making the amendment Patent applicant address 1-3-23 Dojimahama, Kita-ku, Osaka Name Tarima Co., Ltd. Representative Fuku 1) Order Yoshitun Agent 5, Subject of amendment (1) “Claims” column a of the specification Contents of amendment (1) Amend the scope of claims as shown in the attached sheet 0 (2) Specification, page 6 Correct "natural" in line 18 to "self-combustion." (3) Add the following sentence between the first and second lines of page 14 of the specification. "In addition, in the case of a large-sized boiler, there is a risk that it will be difficult to integrate the load-type semi-combustion gasifier 3 and the boiler 5 due to balance. Therefore, in such a case, the third As shown in the figure, it is desirable to integrate the rectangular fluidized bed and the boiler 5 into a compact design.
7 is a coal supply feeder consisting of a screw feeder 28 and a coal projection device 29; 3 is a rectangular fluidized bed type semi-combustion gasifier; and 4 is a fluidizing air nozzle equipped with a header 30. 31 is a sand and ash discharge device, 32 is a sieve device, 33 is a water-sealed conveyor for taking out solids, 34 is a sand re-feeding device, 35 is a water-sealed conveyor for ash discharge, and the other parts are the same as those in FIG. The principle and merits of such a steam boiler 1 are no different from the load method described above. (4) The following sentence is added between lines 17 and 18 on page 15 of the specification. "FIG. 3 is a schematic diagram showing the general structure of a steam boiler according to another embodiment of the present invention." (5) Add FIG. 3 as attached. Claims (1) A coal supply feeder that supplies coarsely crushed coal, and a part of the coal from the coal supply feeder that is combusted and maintained at a temperature necessary for gasification while the remainder of the coal is fixed by pyrolysis. A road-shaped semi-combustion gasifier or fluidized bed that generates soot and gas mainly composed of carbon, and an air nozzle that blows out the air necessary for the flow and thermal decomposition of coal in the semi-combustion gasifier,
A boiler whose combustion chamber is directly connected to a semi-combustion gasifier, where it burns the soot and gas from the semi-combustion gasifier at the same time, and the secondary air necessary for gas combustion in the combustion chamber of the boiler is ejected. A steam boiler characterized in that it is composed of a secondary air nozzle and a secondary air nozzle.

Claims (1)

[Claims] A coal supply feeder supplies coarsely crushed coal, and a part of the coal from the coal supply feeder is combusted to maintain the temperature required for gasification, while the rest of the coal is pyrolyzed to produce soot and dust mainly composed of fixed carbon. A road-shaped semi-combustion gasifier that generates gas, an air nozzle that blows out the air necessary for the flow and thermal decomposition of coal in the semi-combustion gasifier, and its combustion chamber is directly connected to the semi-combustion gasifier. Here, we developed a system consisting of a boiler that simultaneously burns soot and gas from a semi-combustion gasifier, and a secondary air nozzle that blows out the secondary air necessary for gas combustion in the combustion chamber of the boiler. Features a steam boiler.