JPS58123017A - Incinerating treatment of sewage sludge - Google Patents

Abstract

PURPOSE:To increase the amount of generation of digested gas to be supplied to a power generation plant, etc., by a method in which dehydrated cake of digested sludge is further dewatered by a given drier and burned in a fluidized bed incinerator, and waste heat generated during the dewatering process is used in the heating of raw sludge in a degestion tank. CONSTITUTION:Raw sludge supplied through a heat exchanger 22 is digested in a digestion tank 11 and then dewatered through a dehydrator 12 and an indirect heating type drier 13, whereby increasing the low-calorific heat amount of the cake. Then, the cake is sent to a fluidized bed incinerator 14 where it is burned by self-combustion. The combustion gas generated in the burning period is utilized as heat source for a boiler 15 and then discharged through an electric dust collector 16 and an air blower 17 from a stack 18. The steam generated in the dehydration of the cake in the drier 13 is sent to a condenser 20 by a circulating blower 19 where it is condensed into warm water. In this case, part of the warm water is utilized to heat raw sludge through heat exchangers 21 and 22 in which heat medium is circulated.

Description

[Detailed description of the invention] The present invention relates to a joint treatment method for sewage sludge.

In the conventional method of this kind, as shown in Figure 1, a cake obtained by dewatering digested sludge in a dehydrator is incinerated in a fluidized bed furnace 1 while continuously supplying auxiliary fuel. The combustion gas generated during incineration is supplied to the fluidized bed furnace 1 by a forced winding blower, and a heat exchanger 2 for preheating the combustion air is used to limit the temperature of the combustion gas to a certain value or less. Heat exchanger 3 for
, an electric precipitator 4, and an exhaust fan 5, and then the chimney 6.
The water that had been neutralized and released into the atmosphere was heated in the heat exchanger 3, collected into hot water, stored in the hot water tank, and then released. However, the hot water is in the digestion tank (omitted from the diagram).
It was not used as a heat source to heat the raw sludge that was fed into K.

Therefore, the conventional method had the disadvantage of continuously requiring auxiliary fuel to incinerate the dehydrated cake in a fluidized bed furnace. Even though the amount of digestion gas generated in the digestion tank could be increased, the raw sludge was not heated.
This has the disadvantage that the amount of digestion gas generated is limited, which in turn reduces the efficiency of power generation devices that utilize digestion gas.

The present invention eliminates the drawbacks of the conventional methods as described above, does not require auxiliary fuel when incinerating the dehydrated cake in a fluidized bed furnace, and also heats the raw sludge introduced into the digester. Therefore, it is an object of the present invention to provide a sewage sludge combustion treatment method that can increase the amount of digestion gas generated and improve the efficiency of a power generation device using digestion gas.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 2 shows the 70-sheet of the present invention, with digester 1
The sludge digested in step 1 is turned into a dehydrated cake in dehydrator 12. Since the moisture content in this dehydrated cake is about 70-, it is further dehydrated in the indirect heating type drying device 13 to reduce the moisture content in the dehydrated cake to about 48- and increase the lower calorific value of the cake.

The cake, which has been dehydrated in the indirect heating dryer 13 and has an increased lower calorific value, is sent to a fluidized bed furnace 14K, where it is self-combusted and incinerated. The combustion gas produced during incineration is a boiler! 5
After being used as a heat source, it passes through an electrostatic precipitator 17 and an exhaust fan, and is released into the atmosphere from a smoke center I8. The steam generated in the boiler 1s is transferred to the indirect heating type drying device 1.
It is used as a heat source for 3. The indirect heating type drying device i
When the cake is dehydrated at tg, steam generated from the cake is sucked together with air by a circulation blower 19 and sent to a condenser, where it condenses to become hot water. A portion of the hot water is sent from the condenser to the heat exchanger 211C, where it radiates heat and then returns to the condenser 2IC. Heat exchanger 21 and heat exchanger 22
A heating medium is circulated between the heating medium and the heat exchanger 22 to radiate heat, thereby warming the raw sludge that is input into the digestion tank 11jC. (Omitted from the figure) K is supplied.

Incidentally, Table 1 shows an example of operating conditions when implementing the method of the present invention.

Table 1 Table 2 shows the properties of the concentrated raw sludge before dehydration in the dehydrator 12 and the dehydrated digested sludge cake after dehydration.

Table 2 This organic content low fever child = 5500 kaa44VS Table 3
shows the properties of the dehydrated cake before dehydration and the dried cake after dehydration in the indirect heating drying device 13.Indirect heating drying device! The performance of No. 3 is as follows.

■Amount of moisture evaporated from cake...740 ■Amount of heating steam consumed...1070 ■Heating steam pressure...6 ke/j Performance of G saturated fluidized bed furnace 14 is as follows.

■Combustion air temperature: 20℃■Combustion gas furnace outlet temperature: 900℃■Combustion air amount: 1780 Nd/h■ Combustion gas amount ・・・・・・・・・2490 Nl/
■ Air ratio ・・・・・・・・・1.30 Heat loss ・・・・・・・・・81 Total human heat) ■ Auxiliary fuel ・・・・・・・・・None The performance of boiler 15 is It is as follows.

■Combustion gas inlet temperature ・・・・・・900℃ ■Combustion gas outlet temperature -・・・・250℃ ■Combustion gas amount ・・・・・・・・・2490 Nd/■ Evaporation Amount: 110 ■ Steam pressure: 6 approximately 4 G saturation ■ Feed water temperature: - 80°C The present invention has the above-mentioned configuration. Therefore, the moisture content of the cake dehydrated in the indirect heating dryer decreases, the lower heating value of the cake is no longer high, and the cake self-combusts in the fluidized bed furnace. There is no need to supply it to the bed furnace, and the waste heat of the combustion gas generated in the fluidized bed furnace is recovered in the boiler, and the recovered heat is ultimately used to heat the raw sludge that is fed into the digester. This has the effect of increasing the amount of digestion gas generated and improving the efficiency of power generation devices and the like that utilize digestion gas.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of a conventional method, and FIG. 2 is a flow sheet of a method according to the present invention. 11...Digestion tank, 1! ! ...Indirect heating type drying device, 14...Fluidized bed furnace. Agent Patent Attorney Masatoshi Sato

Claims (1)

[Claims] The dehydrated cake of digested sludge is further dehydrated in an indirect heating dryer, then incinerated in a fluidized bed furnace, and the waste heat generated during further dewatering of the dehydrated cake in the indirect heating dryer is used to digest the raw sludge that is input into ImK. 1. A method for incinerating sewage sludge, which is used for heating water and increasing the amount of digestive gas generated to be supplied to power generation equipment, etc.