JPS6146813A - Temperature controlling method in fluidized bed incinerator facility - Google Patents

Abstract

PURPOSE:To reduce a volume of auxiliary fuel in respect to sludge of which nature is gradually varied by a method wherein a ratio between a supplying amount from an indirect supplying system and another supplying volume from a direct supplying system is adjusted in response to a sensed temperature at the fluidized bed and a free board part. CONSTITUTION:Cakes from an indirect feeder 9A are fed by a conveyor 10A to an indirect heating and drying machine 11, thereafter the dried cakes are fed into a furnace by the conveyor 12A and the indirect supplying system is constructed as above. In turn, cakes from the direct feeder 9B pass through the conveyors 10B and 12B as they are and fed into the furnace, thereby a direct supplying system is made. In case that a temperature of the fluidized bed is near an ignition temperature of the cakes, a rate of indirect supplying volume is increased, and in case that a temperature of the fluidized bed is increased higher than 850 deg.C, it is adjusted to increase the direct supplying volume. With this arrangement, it is possible to make a proper control over the temperature in the furnace and then a generation of clinker and a damage of the furnace material is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a temperature control method in a fluidized bed incinerator.

[Technical background of the invention and its problems]

Since fluidized bed incinerators have various advantages, they have been widely used in recent years and many proposals have been made.

Prior to incineration of municipal waste, etc., it is filtered and dehydrated, then dried if necessary, and then placed in an incinerator.

The moisture content and combustion temperature of this type of cake have the relationship shown in FIG. That is, when the moisture content is low, the combustion temperature tends to increase. Therefore, excessive drying
The temperature inside the furnace becomes too high, leading to the formation of clinker and damage to the furnace materials.

On the other hand, if the degree of dryness is low, a large amount of auxiliary fuel must be used, and there is a risk that the fluidized bed temperature will drop to a temperature lower than the ignition temperature of the cake due to the moisture load, and the fluidized bed will no longer function. have sex.

Conventionally, in order to achieve optimal combustion and internal temperature control in an incinerator, the degree of drying is reduced, the incinerator is operated in the auxiliary combustion range, and the amount of auxiliary fuel used is adjusted. However, in order to incinerate materials such as sewage sludge whose properties change from moment to moment, it is necessary to use a large amount of auxiliary fuel to reduce the changing properties of the sludge, for example, to reduce the excess moisture content of the sludge, or There are problems such as the incineration capacity of the furnace being low in response to the fluctuating amount of sludge supplied.

[Purpose of the invention]

An object of the present invention is to solve the above-mentioned conventional problems.

The amount of auxiliary fuel used can be minimized even for water sludge, etc., where properties such as moisture content change from moment to moment, and clinker generation and damage to furnace materials due to excessive rise in furnace temperature can be prevented. Needless to say, the object of the present invention is to provide a temperature control method that can optimally control the temperature of each of the fluidized bed section and freeboard section in the furnace.

[Summary of the Invention] To achieve this object, the first invention provides an indirect supply system for cake that goes through a dryer to a fluidized bed incinerator, and a direct supply system for cake that goes directly to the incinerator without going through a dryer. and a supply system, and adjust the ratio of the supply amount from the indirect supply system and the supply amount from the direct supply system based on the detected temperatures of the fluidized bed part and the freeboard part in the fluidized bed incinerator. It is characterized by:

In addition, the second invention provides a fluidized bed incinerator that uses auxiliary fuel and is equipped with an exhaust gas waste heat recovery boiler; A direct supply system for cake that reaches the incinerator without passing through the incinerator is installed, and the supply amount from the indirect supply system and the direct supply are determined based on the detected temperatures of the fluidized bed section and the freeboard section in the fluidized bed incinerator. In addition to adjusting the proportion of the amount supplied from the system, when using auxiliary fuel, the amount of drying steam supplied from the waste heat recovery boiler to the dryer and the amount of cake passing through the dryer are proportionally adjusted, and the amount of cake passing through the dryer is proportionally adjusted. It is characterized in that the amount of supply from the direct supply system is adjusted so that the O2 concentration in the exhaust gas is at an appropriate value within a range that can maintain the fluidized bed temperature above the ignition temperature of the cake.

The first main point of the present invention is that an indirect supply system that passes through the dryer and a direct supply system that does not pass through the dryer are provided together.

Previously, only one system was available.

The second key point is to detect the temperatures of the fluidized bed section and the freeboard section, respectively, and adjust the proportion of the supply amount from the indirect supply system and the direct supply system based on this, resulting in The point is that the temperature is controlled.

Mainly, if the moisture content of the dried cake is always constant, the temperature inside the furnace can be easily controlled. However, as shown in Figure 3, due to the characteristics of the dryer, the drying speed changes depending on the moisture content of the raw cake, and there is a time lag in the change in dryness. It is extremely difficult to keep constant.

Furthermore, even if we were to continuously measure the moisture content of the cake at the dryer outlet and feed this result back to the dryer to adjust the moisture content, it would be practically impossible as there is no suitable moisture meter. Therefore, by adjusting the ratio of the feed amounts from the direct and indirect feed systems, the aim is to always burn a cake with a constant moisture content in the furnace.

On the other hand, the present inventors have found that when drying is insufficient, the temperature of the fluidized bed section decreases, and when drying is excessive, the temperatures of the fluidized bed section and freeboard section tend to rise. Therefore, it is of great significance to adjust the ratio according to the temperatures of the fluidized bed section and the freeboard section. Also, if there is less dryness,
If too much auxiliary fuel is used and the drying is excessive, there is no need to use auxiliary fuel, but the temperature inside the furnace will rise excessively. in general,
The inventors' calculations and experiments have revealed that if the degree of drying is adjusted to the extent that it self-combusts at around 800°C, the amount of auxiliary fuel used will be minimized and the furnace temperature will not rise too much. . Therefore, by adjusting the degree of dryness, the amount of auxiliary fuel used can be minimized.

On the other hand, regarding the third main point, when the degree of drying is low and auxiliary fuel is used, control tends to increase the amount of cake passed through the dryer.

However, if more than a certain amount of cake is fed to the dryer,
The moisture content at the outlet of the dryer increases, causing problems such as clogging at the outlet of the dryer. Therefore, based on the knowledge that the amount of moisture that can be dried with an indirect heating dryer is proportional to the amount of steam consumed by the dryer, the amount of drying steam supplied and the amount of cake passing through the dryer are adjusted within the drying capacity. It will be adjusted proportionally.

Also, when increasing the amount of cake fed to the dryer,
If the dryer has sufficient capacity, it is possible to increase the amount of steam supplied to increase the amount of dry moisture and steam consumption, but if the drying function is overloaded, the amount of cake supplied to the dryer can be increased. Even if it is increased, the dry moisture content will not increase, and the steam consumption will reach saturation and will no longer increase. Since this state is the operating state in which the amount of cake that passes through the dryer is the maximum amount, the total amount of cake input is determined by the amount of directly fed cake that does not pass through the dryer.

In this state, if the amount of directly fed cake is increased, its high water content will lower the fluidized bed temperature and increase the amount of auxiliary fuel used, which will increase the amount of oxygen consumed in combustion and increase the concentration of 02 in the exhaust gas. decreases. Therefore, in order to operate with the maximum amount of cake input, which is the highest efficiency of the furnace, the amount of directly fed cake should be adjusted so that the 02 concentration in the exhaust gas is around 3 to 8%, especially around 5 to 6%. In particular, the fourth
There are main points. At this time, the amount of flowing air supplied to the furnace is fixed at around the maximum value determined from the furnace capacity. If the temperature of the fluidized bed falls too low, problems such as unburned loss will occur, so if the temperature of the fluidized bed falls below 650°C, the amount of directly fed cake should be reduced.

[Specific Examples of the Invention] The present invention will be described below with reference to an example of fluidized bed incineration equipment shown in FIG.

1 is a fluidized bed incinerator, in which a fluidized medium such as sand is fluidized together with the material to be incinerated by fluidizing air Ai. As a result, a fluidized bed section 2 is formed in the lower part of the furnace, and a freeboard section 3 is formed in the upper part. The auxiliary fuel Oi is blown into the fluidized bed section 2 by the pump 4 through the control valve 5.

On the other hand, the dehydrated cake is fed into the furnace through two systems. That is, the dehydrated cake hopper 6A.

6B, a screw conveyor 8A driven by motors 7A and 7B, and an indirect feeder 9A equipped with a cutting device having 8B, and a direct feeder 9B. After being supplied to the oven, the dried cake is fed into the oven by a conveyor 12A, thus forming an indirect supply system.

On the other hand, a direct supply system is constructed in which the cake from the direct feeder 9B is directly fed into the furnace through the conveyors IOB and 12B.

These feeding amounts are determined by feeding amount controllers 15A and 15B based on signals from feeding amount detectors 13A and 13B such as conveyor scales installed on conveyors IOA and IOB and signals from multi-function controller 14. It is controlled by adjusting the rotation speed of motors 7A and 7B.

On the other hand, a waste heat recovery boiler 17 is provided in the exhaust gas passage 16 to recover heat in the exhaust gas, and the heat recovered as steam is
It is used as a heat source for drying the dryer 11 via the steam supply path 18. In order to control the amount of steam, a steam flow meter 19 and a steam amount control valve 2 are provided in the supply path 18.
0 is set. 21 is a 02 concentration meter in exhaust gas provided in the exhaust gas path 16.

Additionally, thermometers 22 are installed in the fluidized bed section 2 and the freeboard section 3.
．． 23 is installed. The multifunction controller 14 is used for illustration and the following adjustment/control.

During operation, the following controls are performed.

First, the fluidized bed temperature is about 65°C, which is around the ignition temperature of the cake.
If the temperature drops below 0°C and the temperature of the freeboard section exceeds around 800°C, it means that a cake with a high moisture content is being fed into the furnace, and a large amount of auxiliary fuel is used accordingly. Adjust to increase the ratio of indirect supply to supply.

On the other hand, the temperature difference between the fluidized bed section and the freeboard section is approximately 1
If the temperature of the fluidized bed exceeds 850°C within 00°C, the ratio is decreased and the amount of direct feed is adjusted to increase.

In any of the above cases, the amount of auxiliary fuel supplied to the furnace is increased or decreased so that the highest temperature part in the furnace is approximately 800°C.

On the other hand, in order to prevent clogging of the outlet of the dryer, especially when the amount of indirect supply is large, in the range where the amount of steam increases as the amount of indirect supply increases, the increase or decrease of the amount of indirect supply is automatically adjusted according to the temperature inside the furnace. Do not increase the amount of indirect input any further within the range where the amount of steam no longer increases. Furthermore, when the dryer capacity is slightly overloaded, the fluidized bed temperature may reach the ignition temperature (approximately 650°C).
The direct supply amount is controlled so that the 02 concentration in the exhaust gas is about 5 to 6%, while adjusting the direct supply amount so that it does not become below.

On the other hand, when auxiliary fuel is not used, the amount of directly supplied cake tends to increase. However, if the direct supply becomes too large, the dry moisture content becomes too small, resulting in inefficient operation that uses a large amount of auxiliary fuel. It should not be too expensive. At this time, the total cake amount, which is near the maximum capacity of the furnace, has a concentration of 02 in the exhaust gas of 5 to 5.
Since it is approximately 6%, the most efficient operation can be achieved by increasing the total cake supply amount when the O2 concentration increases, and decreasing it when the O2 concentration decreases. .

[Effects of the Invention] As described above, according to the present invention, the temperature inside the furnace can be optimally controlled, and the generation of clinker and damage to the furnace material due to an excessive rise in the furnace temperature can be prevented. Furthermore, the amount of auxiliary fuel used can be minimized, and a decrease in the total input amount due to a decrease in fluidized bed temperature can also be prevented.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of incineration equipment for carrying out the method of the present invention;
FIGS. 2 and 3 are correlation diagrams between the moisture content of the cake, the combustion temperature, and the drying rate. 1. Incinerator 2. Fluidized bed section 3. φ freeboard section 11. Dryer 17. Waste heat recovery boiler 22. 23. Thermometer Ai. Fluidizing air Oi. Auxiliary fuel Patent applicant Yoshi Matsuki Masami AmanoTsukishima Kikai Co., Ltd.

Claims (2)

[Claims] (1) An indirect cake supply system leading to the fluidized bed incinerator via the dryer and a direct cake supply system leading directly to the incinerator without passing through the dryer are installed together, and the fluidized bed in the fluidized bed incinerator is 1. A method for controlling temperature in a fluidized bed incineration facility, characterized in that the ratio between the amount of supply from the indirect supply system and the amount of supply from the direct supply system is adjusted based on the detected temperatures of the freeboard section and the freeboard section. (2) In addition to using auxiliary fuel, for a fluidized bed incinerator equipped with an exhaust gas waste heat recovery boiler, there is an indirect supply system for cake that passes through a dryer to the fluidized bed incinerator, and then passes through the dryer. A direct supply system for cake to the incinerator is installed, and the supply amount from the indirect supply system and the amount from the direct supply system are determined based on the detected temperatures of the fluidized bed section and the freeboard section of the fluidized bed incinerator. In addition to adjusting the proportion of the supply amount, when using auxiliary fuel, the amount of drying steam supplied from the waste heat recovery boiler to the dryer and the amount of cake passing through the dryer are proportionally adjusted, and the direct supply system A temperature control method in a fluidized bed incineration facility, comprising adjusting the amount of O_2 in the exhaust gas to an appropriate value within a range that maintains the temperature of the fluidized bed above the ignition temperature of the cake.