JPS5812927A - Method for incinerating sludge - Google Patents

Abstract

PURPOSE:To promote desulfurizing and desalting actions in a process of incinerating sludge, by separately storing lime cakes which are dehydrated using slaked lime, and by mixing a specific amount of stored lime cakes to the other cakes. CONSTITUTION:A lime cake 1 containing slaked lime and a non-lime cake other than the cake 1 are thrown into hoppers 4 and 5, to which quantitative feeders 6 and 7 are arranged, after they are thrown into sludge pits 1a and 2a. A predetermined quantity of cakes 1 and 2 are extracted by a command from a controlling box 15, kneaded in a kneader 8, passing through pipelines 13 and 14, and then, fed into a fluidized bed furance 10 to be incinerated. A control box 15 controls the motors M1 and M2 of feeders 6 and 7, receiving the signals from flow detectors 16 and 17, which are provided to detectors 18 and 19 to detect the densities of SOx and HC1, respectively, and also to the pipelines 13 and 14. With such an arrangement, the sulfur content and the salt content can be changed into calcium sulfate and calcium chloride.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for incinerating a dehydrated cake of one-year-old sludge, and particularly to a method that can significantly reduce the amount of public substances produced during incineration.

In large cities, it is common to install sewage treatment plants in multiple locations to treat domestic wastewater, etc., and there are many types of dewatered cakes discharged from each treatment plant. The term "dehydrated cake" as used herein refers to sludge generated at a sewage treatment plant, from which a considerable amount of moisture has been removed using various methods. Types of dehydrated cakes include those that have been vacuum dehydrated with a flocculant consisting of slaked lime (AA (Oyu 2) and iron salts, those that have been centrifugally dehydrated or belt press dehydrated with a polymer flocculant, and those that have been pressure dehydrated with slaked lime and iron salts. There are things etc.

Normally, when these dehydrated cakes are incinerated, the dehydrated cakes are collected in one place and put into an incinerator as is. In this case, there is a problem in that the exhaust gas (combustion gas) contains a considerable amount of sulfur oxide (SOX), which is one of the air pollutants, and in some cases also contains hydrogen chloride (Hal). These are produced by the oxidation of sulfur or chlorine contained in the flammable components of sludge, and some are also produced from the combustion of heavy oil used as auxiliary fuel. For this reason, these harmful gases must be removed by washing with a device such as a scrubber using an aqueous solution of caustic soda, resulting in a problem of high equipment costs. Furthermore, since the scrubber effluent itself contains a large amount of pollutants, it is also necessary to reprocess this effluent.

The purpose of this invention is to eliminate the above-mentioned problems, remove pollutants during the incineration process of dehydrated cake, and significantly reduce the amount of pollutants discharged without using special equipment such as souffrane. The goal is to provide a way to do so.

In short, this invention focuses on the fact that in a dehydrated cake dehydrated with slaked lime, this slaked lime performs a desulfurization or desalination effect during the combustion process, and the dehydrated cake containing slaked lime is stored separately from other dehydrated cakes. However, in this method, a predetermined amount of dehydrated cake containing slaked lime is mixed with other dehydrated cake to efficiently carry out the desulfurization and desalination effects during the combustion process.

The method according to the present invention will be explained below with reference to the drawings.

In FIG. 1, the dewatered cake produced at each sewage treatment plant is transported to a sludge pit of a sludge incinerator by means of transportation such as a truck. In this case, a dehydrated cake containing slaked lime (hereinafter referred to as "lime cake") 1 is distinguished from other dehydrated cakes and is thrown into a sludge pit (la). Another dehydrated cake (11), that is, a dehydrated cake that has been dehydrated by a polymer flocculant or heat treatment and does not contain lime (hereinafter referred to as "lime-free cake") 2, is placed in a separate pit 2a. The dewatered cakes loaded into each bit are loaded into hoppers 4 and 5 by packet cranes 3 and 3'. Quantitative feeders 6 and 7 are arranged at the bottom of each hopper, and the lime cakes 1 and 2 are quantitatively taken out according to the ratio described later.
The lime is supplied to the sludge and kneaded so that it is evenly dispersed in the sludge. The kneaded sludge is fed into the fluidized bed 11 of the fluidized bed furnace 10 through the pipe 9 and incinerated.

In the combustion process in the fluidized bed furnace 10, the slaked lime (
qa (01() 2 ) reacts with sulfur (S) or chlorine (C1) to form calcium sulfate (OaSO4), respectively.
), , calcium chloride (Oak!12), S and C
1 from dissipating into the atmosphere together with exhaust gas as SOx or HOI.

15 is a control box that emits memory and command signals, and motors M and - of quantitative feeders 6 and 7 are connected to this control box 15.
is connected by a command signal circuit. Next, 16 and 17 are flow rate detectors 1 provided in the pipe line 13 supplying the lime cake 1 and the pipe line 14 supplying the non-lime cake, respectively.
8 is an SOx installed in the exhaust gas pipe connected to the fluidized bed furnace 10
Concentration detector.

Similarly, 19 is an HCI concentration detector. These 16゜1
? , 18 and 19 are connected to the control box 15 by a detection signal circuit.

The control box 15 constantly detects the So, x and HC1 concentrations in the exhaust gas using the SOx concentration detector 18 and the HCI concentration detector 19, and controls the SOX concentration and the HOI concentration so that they are always within set values.

That is, when the SOx concentration and the HOI concentration are on the rise, a command signal is issued to the motor to increase the supply amount of lime cake 1, thereby activating the production reaction of calcium sulfate and calcium chloride in the furnace. In this case, control box 1
5, the load of the fluidized bed furnace 10 is input as a signal so that the total supply amount of dehydrated cake does not exceed the load of the fluidized bed furnace 1o. In other words, in the above case, lime cake 1
If an overload occurs due to an increase in the supply amount of lime cake 2, a command signal is issued to the motor M to reduce the supply amount of lime cake 2 and relatively increase the mixing ratio of lime cake 1. Make it. Note that the supply amount of each dehydrated cake can be indirectly detected by detecting the rotation speed of the motor M and MP, but the actual flow rate is detected by the flow rate detector 16.1'7, and this is detected by the control box. 15 as a correction value, more precise control can be performed.

By implementing this invention, the amount of pollutants such as SOx and HOI produced by the combustion of dehydrated cake can be significantly reduced, so there is no need to install a pollutant removal device such as a scrubber. There is no risk of secondary pollution.

Furthermore, it is economical because there is no need to add special chemicals such as desulfurization agents to prevent SOX and HOI.

[Brief explanation of drawings]

FIG. 1 is a dehydrated cake combustion system diagram for carrying out the method according to the present invention. l... Lime cake 2... Lime-free cake 6.7... Quantitative feeder 10... Fluidized bed furnace 15... Control box 16 , l'7...Flow rate detector

Claims (1)

[Claims] 1. In a method for incinerating dehydrated cakes of sludge produced in different dehydration processes, a lime cake dehydrated using slaked lime and a non-lime cake dehydrated in other processes are separated, respectively. The supply ratio of lime cake and lime-free cake to the incinerator is changed according to the sulfur oxide concentration and hydrogen chloride concentration in the exhaust gas discharged from the incinerator, and the sulfur oxide and chloride in the exhaust gas are changed. A sludge incineration method characterized by reducing hydrogen concentration. 2. A metering feeder for supplying lime cake and a metering feeder for supplying lime-free cake are each connected in circuit to a control box that emits memory and command signals, and a detector detects the flow rate of lime cake, and a detector detects the flow rate of lime-free cake. , a detector that detects the concentration of sulfur oxides in exhaust gas, and a detector that detects the concentration of hydrogen chloride in the exhaust gas are connected to the control box, respectively, to detect the concentration of sulfur oxides and hydrogen chloride in the exhaust gas, and to detect these concentrations. 2. The sludge incineration method according to claim 1, wherein the feed ratio of lime cake and lime-free cake is automatically adjusted by a control box.