JPS6113125B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel boiler combustion ash treatment method.

Conventionally, in heavy crude oil combustion boilers, unburned components (dust) generated as a result of combustion are collected in a dust collector, and the concentration of soot and dust in the exhaust gas is kept below the regulatory value. The ash collected by this dust collector contains ash from the fuel, unburned carbon, etc., but since unburned carbon normally accounts for 30 to 90% of the ash, it is easy to dispose of this ash. It was customary to install an ash incinerator to do so. However, this ash incinerator has the following drawbacks.

(b) Along with the increase in unit capacity, the equipment costs for incinerators for a 600,000 KW boiler have also increased to over 1 billion yen.

(b) Light oil is required to supplement the combustion of the collected ash, and the fuel consumption is also large (approximately 200/h for a 600,000 KW boiler), and the heat generated by this combustion is not utilized. is being released into the atmosphere.

An object of the present invention is to provide a novel boiler combustion ash treatment method that fundamentally solves the drawbacks of such conventional methods.

That is, in the present invention, boiler combustion ash collected by a dust collector is separated into unburned carbon and heavy metal components by a separator, the separated unburned carbon is mixed into a part of the main fuel, and this mixture is sent to the furnace. This boiler combustion ash treatment method is characterized by charging the ash into the furnace from the upper part to carry out the denitrification reaction and to complete the combustion.

According to the present invention, the ash incinerator, which conventionally required a large amount of equipment and operating costs and the energy was wasted, is abolished, and the unburned carbon in the collected ash is burned in the furnace, thereby saving energy. can be measured.

Furthermore, according to the present invention, recovered unburned carbon is fed into a boiler furnace, and due to this denitrification effect, approximately 50% of the recovered unburned carbon is
Complete combustion can be carried out after the denitrification reaction.

Furthermore, according to the present invention, since the collected ash is separated into unburned carbon and ash, it is possible to selectively recover the heavy metals in the ash and make effective use of resources.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to preferred embodiments illustrated in the accompanying drawings.

Main burners 2 are arranged in a combustion chamber 1 of the boiler shown in FIG. 1, and a main burner wind box 3 is provided surrounding these main burners 2. Main burner 2
Above is a top burner, which is shown as consisting of a top burner fuel injection nozzle 5 and a top burner wind box 4. Reference number 6 indicates an air box for completing combustion. There is a boiler convection heat transfer section 7 in the upper part of the boiler. The exhaust gas from the boiler passes through a denitrification device 40, an air preheater 8, a dust collector 9, and a flue gas desulfurization device 10, and is discharged to the atmosphere from a chimney 11.

Reference number 12 is a forced draft fan, and 13 is a recirculating gas draft fan. 20 is the main fuel pump, 21 is the main fuel flow rate adjustment valve, 22 is the fuel branch valve for the upper burner,
23 is a mixing tank, 24 is an agitator, 26 is a fuel pump for the upper burner, and 27 is a fuel flow rate regulating valve for the upper burner. 30 is a dust collector collection ash transfer line;
31 is an unburned carbon recovery device, and 33 is a heavy metal recovery device.

The air pressurized by the forced draft fan 12 is preheated by the air preheater 8, and then enters the main burner wind box 3, where it is vigorously stirred and mixed with the fuel injected from the main burner 2, and then combusted to form a flame. do.

Normally, this flame burns in the furnace combustion chamber 1, becomes high-temperature gas, transfers heat to steam and water in the convection heat transfer section 7, and then reaches the dust collector 9 via the denitrification device 40 and air preheater 8. . Most of the ash (including unburned carbon and heavy metal components) in the exhaust gas is collected by the dust collector 9 . According to the present invention, this ash is collected in the ash transfer line 3.
0 and then sent to the ash processing equipment. FIG. 2 shows a flow sheet for wet processing of heavy oil combustion ash as an example of an ash processing device. As is clear from this flow sheet, in this case, the unburned carbon content of the collected ash is sorted out by the unburned carbon recovery device 31 mainly using the difference in specific gravity. This unburned carbon is sent to the mixing tank 23 via the unburned carbon transfer line 32. The heavy metals in the remaining ash are collected by a heavy metal recovery device 33.
A cake is separated and extracted using a solvent. This heavy metal cake (containing large amounts of vanadium, etc.) can be used as an effective industrial raw material.

Furthermore, when ammonia is used as a denitrifying agent or a dust collection improving agent in the denitrifying device 40, dust collector 9, etc.,
The collected ash contains ammonia, which is recovered as a gas by the ammonia recovery device 35.
This recovered ammonia is effectively reused in the denitrification device 40 and dust collector 9. A part of the main fuel is stored in the mixing tank 23, and the recovered unburned carbon is put into this and stirred and mixed by the stirrer 24 to form a slurry. This slurry is injected into the furnace through the upper burner fuel injection nozzle 5 while its flow rate is controlled by the upper burner fuel flow rate regulating valve 27. In order to diffuse and permeate this upper burner fuel into the exhaust gas, an inert gas is used which is pressurized from the boiler outlet exhaust gas by a recirculation gas ventilator 13, and is injected into the furnace together with the upper burner fuel. Then, the upper burner fuel is vigorously stirred and mixed with the combustion exhaust gas from the main burner, and NOx is reduced by the denitrification effect of hydrocarbons. In order to completely burn this upper burner fuel, an air box 6 for completing combustion is provided.

The results of testing the method of the present invention using experimental equipment are shown in FIG. 3, and the test conditions in this case are as follows.

Fuel used: C heavy oil (N content 0.20%) Ex.O ₂ : 2% Unburned carbon amount: 0.67Kg/H Total fuel flow rate: 800Kg/H Combustion air temperature: 250℃ 7% of total fuel for upper burner A high denitrification efficiency of over 50% is obtained when the above is added.
There was also no generation of CO in the exhaust gas.

In this way, the method of the present invention effectively recovers the thermal energy of unburned carbon that was wasted in conventional ash incinerators, does not require the use of light oil for auxiliary combustion in the incinerator, and It has a high denitrification effect of over 50%. There are also secondary benefits due to the effective use of recovered heavy metals.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a boiler facility that implements the method of the present invention, Figure 2 is a flow sheet of the ash separation equipment with data added for the case of 100 kg/m of heavy oil ash, and Figure 3 is a diagram of the method of the present invention. 3 is a graph showing test results of the method. 1... Furnace combustion chamber, 2... Main burner, 3... Main burner air box, 4... Upper burner air box, 5... Upper burner fuel injection nozzle, 6... Air air box for completing combustion, 7... ... Boiler convection heat transfer section, 8 ... Air preheater, 9 ... Dust collector, 10 ... Flue gas desulfurization device, 11
... Chimney, 12 ... Forced draft fan, 13 ... Recirculation gas fan, 20 ... Main fuel pump, 21 ... Main fuel flow rate adjustment valve, 22 ... Fuel branch valve for upper burner, 23 ... Mixing Tank, 24... Stirrer, 26
... Fuel pump for upper burner, 27 ... Fuel flow rate adjustment valve for upper burner, 30 ... Dust collector collection ash transfer line, 31 ... Unburned carbon recovery device, 32 ... Unburned carbon transfer line, 33 ...Heavy metal recovery equipment, 3
5...Ammonia recovery device, 40...Denitration device.

Claims (1)

[Claims] 1 The boiler combustion ash collected by the dust collector is separated into unburned carbon and heavy metal components by a separator, the separated unburnt carbon is mixed into a part of the main fuel, and this mixture is poured into the furnace from the upper part of the furnace. A method for treating boiler combustion ash, which is characterized by charging ash into a boiler to carry out a denitrification reaction and complete combustion.