JPS63129209A - Utilization of ash of fluidized-bed boiler - Google Patents

Abstract

PURPOSE:To reduce the amount of limestone, used in a boiler, as well as the amount of throw-away ash, by a method wherein ash, generated by the fluidized- bed boiler, in which solid fuel is mixed with limestone to effect fluidized bed combustion, is retrieved, the ash is granulated by binder, and thereafter, the granulated ash is thrown into a fluidized bed again. CONSTITUTION:Ash, generated in a fluidized-bed boiler which effects the mixing and fluidized bed combustion of solid fuel such as coal, coke or the like and limestone, is retrieved and the retrieved ash is granulated into the grains of 1-5mmphi by binder, thereafter, the granulated ash is thrown into a fluidized bed again to burn it. The binder for granulating the ash is preferable to be the series of liquid fuel, such as heavy oil, coal tar, kerosene, mixture of kerosene and pitch, waste oil of machine oil, spindle oil or the like. The granulated ash is thrown into the fluidized bed through a lime throwing device 15, a limestone throwing device 16 or a newly provided granulated ash throwing device 20. In this case, the throwing amount of the granulated ash is preferable to be 80% or less of the total throwing amount of limestone, for example.

Description

[Detailed description of the invention] [Ti, field of application for business owners] The present invention is a method for collecting ash generated in a fluidized bed boiler that performs mixed fluidized combustion of solid fuel such as coal or coke and limestone, and reusing the ash. Concerning the use of fluidized boiler ash.

(Prior Art) Firstly, a fluidized bed boiler is constructed as shown in FIG. In Fig. 1, the boiler main body (1) is divided into a lower wind chamber a) and an upper flow chamber vg (41) by a partition plate (■). The temperature of the sent calcining air is raised by the heat exchanger (6) and then blown through the air conduit (2). For example, granular coal and limestone are put into the fluidized bed (4), and burned while forming a flow with the combustion air from the wind chamber (3). get steam,
The exhaust gas is passed through a flue (8) connected to one side of the fluidized bed (4).
), and sequentially passes through the coarse dust collector (9), energy saver (ID), heat exchanger (6), haiku fan 0δ, and collector 03 to the chimney (
141 and is emitted into the atmosphere. Note that 09 indicates a coal charging device, and 09 indicates a limestone charging device.

The reason why limestone is charged into the fluidized bed (4) at the same time as coal is to improve the capture of harmful SOx produced by combustion of coal and the formation of a fluidized bed, as shown in the following formula.

CacOs −Cao + Cow ・−= (
ItCaO+ SOt + 40* →Ca5O<
・－・－ ■The ash produced in such a fluidized bed boiler (dust collected from the coarse collector (9) and dust collector OJ, ash collected from the bottom of the fluidized bed 14) can be reused in the cement industry, etc. It costs too much money to do so, and the only effective use is to throw the cane teeth in a landfill.

[Problem that the invention seeks to solve]

However, the limestone captures SOx and converts it into CaSO4.
Ca COs is crushed in a fluidized bed (4) before
It was carried out together with the exhaust gas to the coarse dust collector (9) and dust collector 03 in the form of CaCO and CaO, or was discharged from the fluidized bed (4) in the form of CaCO5. Of the limestone that is introduced, only a few percent of the limestone reacts effectively, and the majority is unreacted limestone or quicklime.
The fluidized bed (4) must be replenished one after another with limestone that is decondensed.
4, and the operating costs of fluidized bed boilers were increasing.

An object of the present invention is to effectively utilize fluidized bed boiler ash containing a large amount of active ingredients, and to reduce the amount of limestone used in the boiler and the amount of ash discarded.

[Means to solve the problem]

The feature of the present invention is that the ash generated in a fluidized bed boiler that mixes solid fuel such as coal and Fuchs with limestone is collected, and the collected ash is granulated with a binder to 1 to 5 grains. The purpose is to re-inject it into the flow a layer and burn it.

As mentioned above, the collected ash contains active ingredients, but in its current state, it is difficult to wash it as it contains a very large amount of fine powder.
It will be carried out again by the exhaust gas without staying in the 17th layer. In order to prevent this, in the present invention,
The collected ash is granulated into 1 to 5 axes using a binder. During granulation, if it is less than 11, it will not stay in the fluidized bed like fine powder, and if it is more than 5-1, the particles will be too large and will pile up on the partition plate, making it impossible to obtain a proper fluidized bed. For this reason, 1~
It was decided to granulate to 51-. The granulation shape is 1, spherical,
Alternatively, the extruded orthopedic bag may have any shape, such as a cylindrical shape or a prismatic shape, which is sheared to an appropriate length.

Next, as a binder for granulating the ash, commercial oil,
Liquid fuels such as coal tar, kerosene, a mixture of kerosene and pitch, used oil such as Masi/Ura spindle oil, and so-called waste oil are preferred. This is because it is viscous and the binder itself can become a fuel. For example, it is undesirable to use water as a binder. C for ashes
It contains an aO component, and when granulated with water, the following reaction (3) occurs.

C, aO+11. O→Ca(OH)s --------
(3) Equation (3) is an exothermic reaction, which is dangerous because it generates heat when water is added, and the CaO that has been produced will disappear, meaning that the desulfurization effect of the exhaust gas will not be achieved.

If the strength of the granulated ash cannot be obtained by granulating only the binder, add 2 to 10 wt% of dry clay powder as a granulation aid.
It is good to add it.

The granulated ash obtained in this way may be charged into the fluidized bed together with coal from a coal charging device (or may be charged together with limestone from a limestone charging device, or by a newly installed charging device). Figure 1 shows a structure in which a new granulated ash official device (2) is installed and a limestone inlet is used for charging into the fluidized bed. If it is less than 80% of the input gutter, no problem will occur.

In addition, as shown in the above equation 0, the ash contains SO in the exhaust gas.
Since it contains CaSO4 that has reacted with
If the O degree increases and this is granulated and reused, the desulfurization effect of the exhaust gas will decrease. Therefore, we measure SOx 66 in the exhaust gas periodically or continuously, and if the concentration becomes high, we either dispose of some of the ash or dispose of fine ash with a relatively high CaSO41O content. It is necessary to manage the waste by partially dumping the waste (collected by dust collectors).

[For production]

In this civilization, the ash generated in the fluidized bed boiler is granulated with a binder for 1 to 5 times, and then it is put into the a bed and burned, so it does not settle in the a bed. The CaO component, which is a non-burning decoy and is not released by exhaust gas (always forms a stable flow 0, and contains large amounts of L and Th in the ash, is the main component of limestone, CaCOs).
Because it is produced by an endothermic reaction, it absorbs less a than limestone and contributes to the desulfurization reaction of exhaust gas.
When a liquid fuel such as heavy oil is used as a binder, the granulated ash acts as a fuel as well as a desulfurizing agent for exhaust gas, which also reduces the amount of coal input.

〔Example〕

As for the specifications of the boiler, the amount of evaporation is G OT/llr 1
The experiment was carried out with a steam pressure of 90 kg/c+L, a steam temperature of 515° C., and a coal combustion amount of 7 to 8 T/llr.

Table 1 shows a comparison of the amount of coal supplied, the amount of limestone supplied, the amount of ash used, etc. between the conventional example and the method of the present invention.

Table 1 In addition, the components and particle size of the ash generated in the boiler are as shown in Table 2. In the present invention, the entire amount of ash recovered from the bottom of the fluidized bed is recycled, and a portion of the dust recovered from the dust collector is recycled. were disposed of and some were reused. The granulation conditions are shown in Table 3. The granulator used was a horizontal extrusion granulator with a disk type die.

The method of the present invention shown in Table 1 is the average value used for the various granulated ash shown in Table 3. Comparing this method of the invention with the conventional method, the chemical components shown in Table 2 are The amount of CaO (including CaCOs) and the amount of C have been effectively utilized, resulting in a reduction of several % in coal.
It can be seen that a reduction of about 60% with limestone and a reduction of about 40% with waste ash is possible, and the SOx content in the exhaust gas is almost the same, indicating that the desulfurization property is not impaired.

In addition, in the method of the present invention, it is not necessarily necessary to use the entire amount of ash generated in order to maintain desulfurization of exhaust gas, and it is preferable to discard a portion of the ash generated and use it in combination with new limescale.

〔Effect of the invention〕

The method of the present invention collects and granulates the ash generated in the flow*a boiler, and reuses it in the fluidized bed boiler.
It is possible to reduce the amount of limestone and waste ash, and moreover, the SOx in the exhaust gas is desulfurized to the same extent as the conventional method, so it has great effects.

[Brief explanation of the drawing]

Figure 1 is an old schematic diagram of a flow VI layer boiler.

Claims (1)

[Claims] A fluidized bed boiler that collects ash generated in a fluidized bed boiler that performs mixed fluidized combustion of solid fuel and limestone, granulates the collected ash with a binder to a size of 1 to 5 mm, and then feeds it back into the fluidized bed for combustion. How to use bed boiler ash.