JPS63143409A - Fluidized bed boiler of circulation type - Google Patents

Abstract

PURPOSE:To make an equipment compact, and to largely decrease its manufacturing cost, by providing a cooling passage, a non-cooling passage, and a particle distribution damper in a particle circulating passage, and by feeding particles, which are caught by a particle separator and of which temperature is controlled in the particle circulating passage, into a combustion furnace. CONSTITUTION:A combustion gas is fed into a rear flue 32 after particles are separated from the gas by a particle separator 10. Heat transfer pipes of boiler 14 are provided in the rear flue 32, and the combustion gas is cooled by those heat transfer pipes of boiler 14, flowing down to a combustion exhaust gas pipeline 21. Part of small volume of fine particles contained in the combustion gas is collected in a rear flue hopper 17 provided in the lower part of a rear flue 32, and the remaining particles are conveyed to the combustion exhaust gas pipeline 21 together with the combustion gas. The particles collected in the rear flue hopper 17 pass through a rotary valve 18 provided under the rear flue hopper, and are returned to a combustion furnace 8 from the outlet 34 of a gas recirculating pipeline via a gas recirculating draft fan 33 and gas recirculating pipeline inlet 35.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the configuration of each device in a circulating fluidized bed boiler.

[Conventional technology]

Conventionally, in a circulating fluidized bed boiler, a cyclone is installed at the combustor outlet to capture circulating particles. The particles collected in the separator are cooled down to the required temperature in a separate cooler, if necessary. Also, the cooler is
Usually, it consists of a bubble-type fluidized bed.

[Problem that the invention seeks to solve]

In conventional technology, each component of a circulating fluidized bed boiler (especially the combustor, separator (cyclone), cooler, etc.) is configured separately, making the entire device complex and requiring a large space. , which necessitated a significant increase in costs.

Regarding particle circulation, according to conventional technology, the circulation ratio has been determined as a balance of natural circulation based on the relationship between superficial velocity, particle size, and resistance of the circulation system, but it is necessary to actively improve this ratio. It is difficult to control, and therefore there are problems such as an increase in auxiliary machine power.

[Means for solving problems]

In order to configure the combustor, cyclone, particle cooler, and boiler heat exchanger tubes in an integrated form, the following methods are used: (g) The cyclone is made into a horizontally halved structure rather than the usual vertical shape, and is integrated at the combustor outlet. Install it as a shape.

(b) Each of the simple separators is constructed integrally with a rear flue connected to the separator outlet and a particle recirculation line.

(c) A particle cooler for circulating particle cooling is arranged in the recirculation line, and these particle coolers are usually composed of evaporator tubes, superheater tubes, economizer tubes, etc. .

In the particle circulation system, the particles are recycled to the furnace using mechanical means such as a screw feeder.

2) In order to accelerate the cooling of particles, a gas recirculation system is installed to introduce a part of the combustion gas into the particle recirculation system and return it to the furnace.

(Function) By the above h), (b), and (c), the combustor, cyclone particle cooler, and boiler heat exchanger tube are integrally and compactly constructed.

Particle cooling in a particle cooler utilizes heat transfer due to solid collisions between particles and cooling pipes as the particles naturally fall.

Due to the above (c), the ventilation power of the primary and secondary air systems is reduced.

(above) promotes heat transfer through solid collisions between particles and heat transfer tubes.

〔Example〕

In Figures 1 and 2, 1 is a forced draft fan, 2 is an air preheater, 3 is a combustion air supply duct, 4 is a primary air system, and 5
is the secondary air system, 6 is the primary air inlet, 7 is the secondary air inlet, 8 is the combustor (furnace), 9 is the fuel supply system, 1
0 is a particle separator, such as a horizontal half-cyclone, 11
12 is a particle distribution damper, 12 is a particle distribution damper drive motor,
13 is a particle cooler (heat exchanger tube), 14 is a boiler heat exchanger tube, 1
5 is a feeder for particle recycling, 16 is a motor for driving the feeder for particle recycling, 17 is a rear flue hopper, 18 is a rotary pulp under the rear flue hopper, 19
is a rear flue hopper bottom ash recycling system, 20 is an ash removal system, 21 is a combustion exhaust gas system, 22 is a nitrogen preheater outlet exhaust gas duct, 23 is a dust collector, 24 is an induced draft fan,
25 is a flue, 26 is a flow agent and desulfurization agent inlet, 27 is a recirculation particle passage, 28 is a particle backflow prevention weir, 29 is a primary air ventilator, 30 is a particle cooling passage, and 31 is a particle non-cooling passage. , 32 is a rear flue, 33 is a gas recirculation ventilator, 34 is a gas recirculation outlet, and 35 is a gas recirculation inlet.

In such a device, air supplied from a forced draft fan 1 passes through an air preheater 2, exchanges heat with the boiler combustion exhaust gas, passes through a combustion air supply duct 3, and is connected to primary air systems 4 and 2. It is divided into 5 air systems. The primary air is boosted to the required pressure by the primary air ventilator 29 and then passed through the primary air port 6.
The air is then introduced into the combustor (furnace) 8 from the bottom as fluidizing air. On the other hand, the secondary air passes through the secondary air system 5 and is a certain distance (5 to 10 m) from the bottom of the combustor 8.
The air is then put into the combustor 8 from the installed secondary air blowing lower.

The purpose of this two-stage combustion is to reduce the amount of NOx generated. In addition, coal particles, sludge, etc., of appropriate size are supplied to the lower part of the combustor 8 from the fuel supply system 9, and desulfurizing agents, etc. are also supplied to the lower part of the combustor 8 from the flow agent and the desulfurizing agent inlet 26. Supplied. The fuel, air, and desulfurizing agent supplied to the combustor 8 undergo a combustion reaction, a desulfurization reaction, and a denitrification reaction in a high-speed flow state (superficial velocity of 5rrL/B to 15m/ill) to reduce NOx.
, enter the particle separator 10 in low SOx conditions. At this time, the flow rate of the combustion gas is gradually increased from the outlet of the combustor 8, and the structure is such that the required flow rate can be secured at the particle separator 10. Particles subjected to swirling force in the particle separator 10 are carried downward along the interior of the particle separator 100 by centrifugal force and reach the entrance of the recirculation particle passage 270.

Further, the particle distribution damper 11 distributes particles to the particle cooling passage 30 and the non-cooling passage 31 in order to control the combustion gas temperature within the combustor 8 to approximately 850°C. The distributed particles are divided into particles that are cooled by the heat exchanger tube of the particle cooler 13 and particles that fall without being cooled, but both are collected by the particle recycling feeder 15 provided under the recirculation particle passage 27. , are recycled to the lower part of the combustor 8. The amount recycled at this time is NOz, S
Ox.

While looking at combustion efficiency, etc., the ventilation machine power will be reduced as much as possible in order to reduce it to zero.

On the other hand, the combustion gas enters the rear flue 32 after its particles are separated in the particle separator 10 . Boiler heat exchanger tubes 14 are disposed in the rear flue 32, and the combustion gas is cooled by these boiler heat exchanger tubes 14, and then transferred to the combustion exhaust gas system 2.
It reaches 1. In the rear flue hopper 17 provided below the rear flue 32, part of a small amount of particulates contained in the combustion gas is stored, and the rest is stored in the flue gas system 21 along with the combustion gas.
be carried to. The particles accumulated in the rear flue hotspots 17 are
Via the rear flue hopper lower rotary bals 18, it passes through the rear flue ash recycle system 19 and returns to the recirculation particle passageway 27 as appropriate.

In addition, the mass balance (flow rate balance) of the particle circulation system,
In order to maintain this, an amount of ash commensurate with the amount of fuel and desulfurization agent input is discharged from the ash removal system 20 to the outside of the system.

In addition, the combustion exhaust gas passes through the air preheater 2 and passes through the air preheater outlet exhaust gas duct 22 to the dust collector 23 and the visiting ventilation fan 2.
4, it reaches the chimney 25.

By the above method, the performance as a fluidized bed boiler is achieved as follows.

Combustion efficiency 98-99% NOx 100p￥1m or less Desulfurization rate 90p or more (Ca/s = 2.5
) Also, in order to promote the cooling of the recirculated particles, a part of the combustion gas passes through the recirculated particle passage 27 as a recirculated gas, accelerates the cooling of the particles, and then returns the gas from the gas recirculation outlet 34. The gas passes through the circulation fan 33 and the gas recirculation inlet 35 and is returned to the combustor 8 . The amount of recirculated gas should be kept sufficiently small and the flow rate should be kept low in order to minimize wear due to particles colliding with the heat transfer tubes.

〔Effect of the invention〕

(IJ piping system is greatly simplified.

(2) The device can be made more compact, resulting in significant cost reductions.

(3) The cooling of the particles does not depend on the bubble-type fluidized bed boiler, but instead relies on collisional heat transfer between the particles and heat transfer tubes as the particles naturally fall, eliminating the need for high-pressure fluidized air (or gas) for the cooler, and improving the structure. is simplified and the power of auxiliary equipment is reduced.

+47 By controlling the flow rate of circulating particles using mechanical means (such as a screw feeder), the amount of circulation can be controlled and the power required for ventilation in the primary and secondary air systems can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a circulating fluidized bed boiler as an embodiment of the present invention, and FIG. 2 is a view taken along the line A-A of the first factor. 8... Combustor (furnace) 10... Particle separator 11... Particle distribution damper 13... Particle cooler (heat transfer tube) 14... Boiler heat transfer tube 15... Particle recycling feeder 21. ... Combustion exhaust gas system 27 ... Recirculation particle passage 28 ... Particle backflow prevention weir 30 ...
Particle cooling passage 31... Particle non-cooling passage 32... Rear flue Sub-agent Patent attorney Shige Okamoto 2 other persons

Claims (1)

[Claims] A vertical combustor, a rear flue arranged in parallel with the combustor, an integrated particle separator provided in the upper part of the rear flue, and a circulation particle passage arranged in parallel with the rear flue. a boiler heat exchanger tube is installed inside the rear flue, the upper part of the particle separator is connected to the combustor, the central part is connected to the rear flue, and the lower part is connected to the circulation particle passage; A circulating flow characterized in that the particle passage is provided with a cooling passage, a non-cooling passage, and a particle distribution damper, and particles captured in the particle separator and whose temperature has been adjusted in the circulation particle passage are supplied to the combustor again. Layer boiler.