JPS6053807B2 - Solid circulation type fluidized combustion equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for combustion treatment of solutions containing organic and inorganic substances.

In processing such solutions, it has already been carried out industrially in many ways to recover energy by burning organic substances, and to chemically change inorganic substances through high-temperature reactions and recover them as useful substances. has been done.

A typical example of such equipment is a recovery boiler used in alkaline pulp manufacturing equipment.

In this device, black liquor, which is a mixture of lignin derivatives, soda sulfide, and caustic soda, is concentrated and sprayed into a hardstone furnace with a built-in heat recovery section, and the resulting droplets are combusted in a high-temperature atmosphere. The remaining ash (inorganic matter) is subjected to a reduction reaction together with unburned organic matter and is discharged outside the furnace in a molten state. On the other hand, in the semi-chemical pulp manufacturing industry, a mixture of lignin and sodium sulfite in the cooking liquor is sprayed into a reducing atmosphere to form high-calorie gas and solid soda carbonate, the former is heat recovered in a waste heat boiler, and the latter is A method is used in which the waste is collected and circulated to the chemical liquid recovery process.

There is also a method of burning the chemical pulp black liquor on a conventional fluidized bed. In other words, black liquor is sprayed from the upper part of a high-temperature, dense fluidized bed flowing at a constant height, and organic matter is white-burned by air supplied from the lower part. In this method, it is important that the flowing particles have a certain size. Among the above methods, the method called spray combustion generally involves a process in which a solution is atomized in a high-temperature gas, the droplets are evaporated to dryness by the high-temperature gas, and the temperature further increases to burn the organic matter. .

The basic step of this method is that the droplets and their product solids are brought into contact with a hot gas and heat transfer takes place. This heat transfer is slow and the residence times of gas and solids are approximately the same. Therefore, the size of the combustion chamber becomes significantly larger than the throughput. On the other hand, in the conventional fluidized bed method, it is necessary to form particles of a certain size as a condition for fluidization, and the average particle size of the particles is usually 0.5~
It is about 5 cm.

Particles smaller than this will fly out of the fluidized bed without forming a fluidized bed. In other words, when performing combustion using a fluidized bed, it is an important condition that the solution is granulated to a constant particle size, and finding and maintaining this condition is an important operational factor. Become. Generally, there are few solutions with good granulation properties, and it is difficult to determine the granulation conditions. The feature of the present invention is basically that, unlike the above-mentioned spray type or conventional fluidized bed type combustion apparatus, a group of particles diffuses and rises to fill the furnace at a relatively low concentration (50 to 250 k9/po). The purpose is to burn organic matter by spraying a solution onto a large amount of solid matter contained in the gas rising at high speed and burning the organic matter. Suitable for handling solutions containing harmful substances.

The object of the present invention is to provide a combustion device with a large fuel load. below,
The invention will be explained by way of example with reference to the accompanying drawings.

In the illustrated embodiment, the combustion device according to the invention has a fluidized column 1 consisting of a substantially cylindrical body 2 and a high-velocity gas duct 3 formed by constricting the lower end of this body.

A hot air box 5 having a combustion furnace 4 is connected to this duct portion 3 . The fluidized column 1 has a gas outlet 6 at its top,
A cyclone 7 is connected to this gas outlet.

The cyclone 7 has a solids hopper 8 at its lower part and a gas outlet 9 at its upper part. Hopper 8 is overflow pipe 1
0, and a discharger 11 is provided in the overflow pipe.
The hopper 8 is also connected to the lower part of the fluidized column 1 by a solids circulation vibrator 12, and is configured to circulate the solids separated by the cyclone 7 into the fluidized column 1, as will be described later. . There is a throttle valve 1 inside the circulation vibrator to prevent backflow.
3 is provided. A spray nozzle 15 is installed in the fluidizer 1 at a level above the opening of the circulation vibrator 12 in the fluidizer 1.
is installed, and this spray nozzle sprays the solution to be treated, which is supplied through the supply vibrator 16, downward within the fluidized column 1. In operation, the solution to be treated is sprayed from the spray nozzle 15 via the supply vibrator 16.

On the other hand, a large amount of solids is supplied from the solids hopper 8 via the circulation vibrator 12, and the solids are dispersed and raised by the combustion air rising from the duct section 3 of the fluidized column 1. Contact with droplets from spray nozzle 15. In other words, the droplets directly contact the surface of the solid material, which is kept at a high temperature, and rapidly transfer heat, resulting in rapid evaporation and decomposition of organic matter, which reacts with the oxygen in the air supplied from the duct section 3. Combustion takes place. At this time, depending on the size of the generated droplets, some droplets descend while others rise.
However, even though the particles moving in the fluidized tower have a terminal velocity that is slower than the average rising speed of the fluidized tower, they do not necessarily move with the rising gas flow and are relatively concentrated. A group of groups (clusters) are continuously formed, which flow downward against the rising gas flow, are diffused, and are carried upward again to form clusters, and the cycle continues. In this way, the particles flow upward through the fluidized column at a much slower rate than the gas flow rate, increasing the velocity difference between the gas and the particles and concomitantly reducing contact with irregularly oriented droplets. This results in good heat exchange and high mass exchange. In this way, residual ash (inorganic matter) accumulates on the surface of the solid particles from which the organic matter has been burned, increasing the particle size.

The solids concentration inside the fluidized column is usually 50-250k9/
The concentration is approximately 7T1, and although it varies depending on the calorific value of the organic matter or the reaction temperature, this concentration is determined by the amount of solid matter circulated and the rate of gas rise in the furnace. The rising gas velocity in the furnace is determined by the particle size of the solid particles and the amount of solution supplied into the furnace (turndown ratio), but is usually 3 to 10 TTI.
．． /second. The diameter of the circulating solid particles is determined by the concentration of solids in the solution and the diameter of the sprayed droplets, but is usually 50~
It is in the range of 800μ. In this way, the granulated particles are led to the cyclone 7 via the gas outlet 6, where the particles and gas are separated.The gas is discharged outside the machine from the outlet 9, and the particles, that is, the solids, are transferred to the hopper. Fall to 8.

A portion of the solids is removed via an overflow pipe 10 from a discharger 11 as product or ash. The remainder of the solids is returned to the fluidized column 1 through the circulation vibrator 12. At this time, the valve 13 prevents backflow. According to the experience of industrial operation, at the start-up of the system of the present invention, hot air is sent while operating the combustion furnace, and a certain amount of solids is introduced to increase the temperature of the circulating solids. is important.

Thus, when the combustion temperature is reached, atomization of the solution is started and combustion air is supplied. This air accelerates and fluidizes the circulating solids. If large droplets form,
It may fall below the opening of the circulation vibrator, but in this case, if an air distribution plate or the like is provided at the bottom of the furnace, it may evaporate to dryness on the top surface.

Therefore, in the present invention, basically, a large-diameter gas ascending duct is provided and a dispersion plate is not used, but it may be used when treating substances that are not likely to adhere to the dispersion plate. In a pilot plant in which the present invention is applied to the treatment of semi-chemical valve waste liquid, the fluidization column 1 has a diameter of 250 cm,
The height is 6 meters (height excluding the duct part), and using a cyclone with an inner diameter of 300 cm, the inner diameter is 400 cm,
A combustion furnace with a length of 600 cm was used. A spray nozzle is installed 4.5 meters from the top of this fluidized column, and a liquid with a total solid content of 55%, an organic content of 45%, an inorganic content of 55%, and a solid calorific value of 3200 Kca1/K9 is sprayed at a rate of 60 liters per hour. It was supplied by The throughput per column volume obtained at this time was 60 kg/77 t'/Hr. This is much larger than the capacity coefficient of conventional spray towers, which is 15 to 20 kg/d/Hr. The composition of the gas generated at this time was 28% H, 6% CO, 42% CH, and CO2l2.
%, H2S3%, while solids include Na2C
The content was 55% O, 43% Na2SO, and 42% carbon, which was the same as in the spray tower. As described above, according to the present invention, it is possible to obtain a large capacity coefficient that could not be obtained with a spray tower, and in addition to making granulation easier, it is also possible to obtain particles with relatively small dimensions and a wide distribution width. Able to drive.

Note that air may be blown into the circulation vibrator within the scope of the present invention.

[Brief explanation of drawings]

The figure is a schematic diagram of a combustion device according to the invention. 1...Fluidization tower, 3...Duct section, 5.
...Hot air box, 7...Cyclone, 8...
...Solid hopper, 12...Circulation vibe, 1
5...Spray nozzle.

Claims (1)

[Claims] 1. A rigid fluidizer, a high-speed rising gas supply device installed at the bottom of the fluidizer, a cyclone device connected to the top of the fluidizer, and a solid material separated by the cyclone device near the bottom of the fluidizer. A solids circulation type comprising a circulation pipe for circulating, and a spray nozzle provided in the fluidizer at a level above the opening of the circulation pipe in the fluidizer to spray the liquid to be combusted. Fluidized combustion equipment.