JPS58136911A - Flue gas recirculation system of refuse incinerator - Google Patents

Abstract

PURPOSE:To prevent the low temperature corrosion of a circulating duct, through which flue gas flows, from occurring and at the same time suppress the generation of NOX in the refuse incinerator by a method wherein the flue gas is circulated to the refuse incinerator by sending it back at this side of an electric dust collector. CONSTITUTION:The flue gas generated at the refuse incinerator 11 is successively past through a waste heat recovery apparatus 12 and the electric dust collector 13 and, after that, the greater part of the flue gas is discharged from a stack into the atmosphere, while one small part of the flue gas is absorbed by means of a circulating blower 14 and, after being discharged from the circulating blower 14, divided into two gas lines or circulated to the refuse incinerator 11 while being regulated its flow rate by a damper 15 arranged in a gas line BC on one side and sent back at this side of the electric dust collector 13 or at the downstream of the waste heat recovery apparatus 12 while being regulated its flow rate by a damper 16 arranged in a by-pass line BD. In this case, the flue gas sent back at this side of the electric dust collector 13 is controlled so as to be flowed the quantity exceeding the heat retaining capacity of the duct of the by-pass line BD for preventing the low temperature corrosion from occurring in said duct.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas circulation system for a waste incinerator.

Conventionally, in this type of system, as shown in Fig. 1, the exhaust gas generated when garbage is incinerated in a garbage incinerator 1 flows out from the garbage incinerator 1 and then passes through a heat recovery device 2 and an electric dust collector 5.
A part of the exhaust gas that has passed is sucked by a circulation blower while the flow rate is controlled by a damper 4 to be used as a drying gas for garbage to be input into the garbage incinerator 1. It was being circulated to Furnace 1. Also garbage incinerator 1
Furnace cooling air was supplied to the waste incinerator 1 in order to reduce the heat load on the furnace body and to maintain the function of the electrostatic precipitator 30.

Therefore, in the conventional system, when the gas for drying food waste becomes unnecessary or becomes small due to a change in the type of food waste input into the waste incinerator 1, the circulation blower 5 is used. Since the flow rate of the exhaust gas that is circulated to the waste incinerator 1 is lower than the duct's heat retention capacity, the circulation duct through which the exhaust gas flows must be kept at a low temperature.
However, it has the disadvantage that the components condense on the surface and corrode. Further, since the conventional system supplies furnace cooling air to the waste incinerator 1, a supply facility for this purpose is required, and the facility has the disadvantage of being expensive.

The present invention eliminates the drawbacks of the conventional ones as described above, prevents low-temperature corrosion of the circulation duct for circulating exhaust gas, and does not require air supply equipment for furnace cooling, reducing equipment costs. The purpose of this product is to provide an exhaust gas circulation system for waste incinerators that can be used for various purposes.

The present invention will be explained below based on the drawings.

FIG. 2 shows an example of the present invention in the form of a flow sheet.
The exhaust gas generated when garbage is incinerated in the garbage incinerator 11 flows out from the garbage incinerator 11 and is then transferred to the exhaust heat recovery equipment 12.
and an electrostatic precipitator 15 in sequence. Most of the exhaust gas that has passed through is released into the atmosphere from a chimney (not shown) via a harmful gas removal device (not shown), but a portion of the exhaust gas is absorbed by the circulation blower 14. The exhaust gas is discharged from the circulation blower 14 and then divided,
One of them is used as furnace cooling gas for the waste incinerator 11 and is circulated to the waste incinerator 11 while the flow rate is adjusted by a damper 15 in the gas line BC, and the other is used as a gas for cooling the waste incinerator 11. The waste heat is returned to the position before the electrostatic precipitator 15, that is, downstream of the exhaust heat recovery equipment 12. The damper 15 adjusts the flow rate by receiving signals of the incinerator temperature T and the furnace outlet temperature T of the waste incinerator 11, and the damper 16 adjusts the flow rate by adjusting the absorption exhaust gas flow rate of the circulation blower 14 ( This is done by receiving signals of Fl + Fl) and the exhaust gas flow rate F returned before the electrostatic precipitator 15.

By the way, the exhaust heat recovery equipment 12 includes a boiler.

A gas cooler, a gas air heater, etc. are used, and the dampers 15 and 16 can also be used to adjust the flow rate manually. Furthermore, the length of the gas line BC is shortened as much as possible to prevent low-temperature corrosion of the duct.

Next, a method of controlling the flow rate of exhaust gas sucked by the circulation blower 14 will be explained.

When the internal temperature of the waste incinerator 11 is high and a large amount of exhaust gas for furnace cooling is required, the opening degree of the damper 15 is increased,
The amount of exhaust gas that is circulated to the garbage incinerator 11 is increased, but the opening degree of the damper 16 is made small, and the amount of exhaust gas that is returned to the front of the electrostatic precipitator 15 is decreased.

On the other hand, if the internal temperature of the waste incinerator 11 is low and a small amount of exhaust gas for cooling the furnace is required, the degree of opening of the damper 15 is reduced and the amount of exhaust gas circulated to the waste incinerator 11 is reduced. The opening degree of the damper 16 is increased to increase the amount of exhaust gas returned to the front of the electrostatic precipitator 13.

Although the flow rate of exhaust gas is controlled in this way, the exhaust gas returned before the electrostatic precipitator 15 always flows at a rate higher than the duct heat retention capacity in order to prevent low-temperature corrosion of the duct of the pipeline BD through which this exhaust gas flows. It is controlled as follows. Therefore, the exhaust gas sucked by the circulating gas blower 14, which is the sum of the exhaust gas returned before the electrostatic precipitator 15 and the exhaust gas circulated to the waste incinerator 11, is less than the heat retention capacity of the duct of the gas line AB through which the exhaust gas flows. Therefore, the duct of the gas line AB can avoid low-temperature corrosion.

Note that the effect of the present invention does not change even if the exhaust gas circulating through the damper 16 is returned not only before the electrostatic precipitator 15 but also after the electrostatic precipitator 15 as long as it is downstream of the heat recovery device 12.

The present invention has the above-mentioned configuration, and the exhaust gas is circulated to the garbage incinerator and returned before the electrostatic precipitator, so that low-temperature corrosion of the circulation duct through which the exhaust gas flows can be prevented, and NOx in the garbage incinerator can be prevented. This has the effect of suppressing the occurrence of nitrification and eliminating the need for denitrification equipment.

Furthermore, in the present invention, by circulating exhaust gas to the waste incinerator as a furnace cooling gas, the amount of exhaust gas passing through the waste heat recovery equipment increases, so the heat recovery rate of the waste heat recovery equipment increases. It has an increasing effect. Furthermore, since the present invention does not require the supply of furnace cooling air, there is no need for furnace cooling air supply equipment, and the amount of harmful gas removal equipment is reduced by the fact that the furnace cooling air is no longer included in the exhaust gas. This has the effect of reducing the size of chimneys, etc., and lowering equipment costs.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of a conventional exhaust gas circulation system, and FIG. 2 is a flow sheet of an exhaust gas circulation system according to the present invention. 11... Garbage incinerator 12... Heat recovery equipment 16... Electrostatic precipitator 14... Circulating blower 15... Damper 16... Damper agent Masatoshi Sato, patent attorney

Claims (1)

[Claims] The exhaust gas generated in the incinerator is passed sequentially through a heat recovery device and an electrostatic precipitator, a part of which is absorbed by a circulation blower, and the sucked exhaust gas is discharged from the circulation blower and then divided. One of the gases is circulated to the incinerator via a damper for use as a furnace cooling gas for the incinerator, and the other is returned to a position downstream of the heat recovery equipment via another damper. Waste incinerator exhaust gas circulation system.