JP3225372B2 - Sludge dehydration drying incineration system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dewatering / drying / incineration system for sewage sludge and sludge generated from general industrial wastewater treatment.

[Prior art]

[0002] Sewage sludge or sludge generated from general industrial wastewater treatment (hereinafter simply referred to as sludge) is added with an inorganic or organic dehydration aid, and a centrifugal dehydrator, vacuum dehydrator, filter press, belt press, screw press, etc. Dewatered mechanically to form a sludge cake with about 60-80% moisture and no fluidity at all. The cake is then processed by the following method.

[0003] There is a method in which a fermentation aid such as peach and sawdust is added to sewage sludge to ferment the sludge to make compost (compost). This compost is used for farmland, but its consumption is limited, and there is a problem that a large amount of compost cannot be consumed and returned.
There is a method in which sewage sludge is directly sprayed on farmland to expect a fertilizer effect. However, this method cannot treat a large amount of sludge.

[0004] In a large-scale treatment plant, the sludge cake is incinerated by a method described later, but in a small-scale treatment plant, the sludge cake contains moisture due to the fact that the operation of the drying equipment and the incinerator is not advantageous in terms of energy. It has been landfilled. In this case, there are many problems such as generation of secondary pollution such as scattering of sludge and emission of bad smell during transport of cakes, generation of water source and marine pollution due to leachate at the landfill, generation of secondary pollution, reduction of landfill suitable land. . In addition, there is a method in which sewage sludge is directly dumped into the sea, but legal regulations are gradually becoming stricter, and above all, it is not a preferable method from the viewpoint of environmental protection.

[0005] As a method of solving this, it has been practiced to add quicklime to sludge to dehydrate it and dry it to use it as a fertilizer or a raw material for cement. However, in this case, the dewatered cake, which is 60 to 80% water, is transported to a cement plant near the limestone mine or sludge is removed from the quick lime plant near the limestone mine in a method that may cause secondary pollution. The sludge that has been transported to the dehydration treatment plant, mixed, dehydrated and dried, and increased in volume must be transported to a cement factory. If the cement plant is suspended for regular inspections or the like, the storage of a large amount of the mixed solid becomes a problem.

When a chlorine-based dehydration aid is used for dewatering sludge, or when a sewage treatment plant is located close to the ocean, the sludge contains a large amount of chlorine, and it is difficult to remove quicklime. Chlorine cannot be removed just because it is mixed, and it is very difficult to use it as a raw material for cement.
In addition, there is a limit in quantity even when used as fertilizer. Above all, using quick lime in a single pass requires a large amount of quick lime, which is a waste of resources.At the same time, there is a concern that a large amount of carbon dioxide gas is released into the atmosphere during quick lime firing, which is a major problem in preventing global warming. ing.

On the other hand, the incineration of the dewatered cake is mainly
It is performed in fluidized bed type, multi-stage furnace type, stair type incinerator,
In order to increase the heat efficiency at the time of incineration and to facilitate the handling of sludge, the heat generated at the time of incineration is recovered and the dewatered cake is dried. The heat recovery medium is steam,
Heat medium oil and hot air are used.

When recovering heat with steam, a waste heat boiler is installed at the gas outlet of the incinerator. However, a boiler water supply facility including a pure water production facility is required, and a qualified boiler engineer is required. Operators are required, and long-term equipment shutdown including incinerators is required for periodic boiler inspections. In addition, since it is a steam generating facility, the facility becomes complicated, the facility cost increases, and a large installation area is required.

[0009] Since the drying equipment is an indirect heating type dryer, the scale of the equipment is large in consideration of the fact that the scale adheres to the heat transfer surface and the heat transfer effect is reduced. Therefore, it takes a complicated method such as returning a part of the dehydrated cake once dried to the dryer entrance, and the material of the heat transfer surface must also be made of stainless steel,
When steam from the exhaust heat boiler is used, it becomes a second-class pressure vessel, and the equipment cost is high.

As a method for compensating for the drawbacks of the steam boiler, a method using a heat transfer oil is partially used. However, the heat transfer oil is inferior in heat transfer efficiency to steam, and furthermore, heat recovery equipment and drying equipment are required. In addition to the drawback that the dryer becomes large, the type of the dryer is similar to the case of the steam, so that the trouble caused by this type has not been eliminated at all. Further, at the time of exchanging the heat transfer oil, disposal of the used oil is a problem.

As a method of compensating for these drawbacks, a method of drying a dewatered cake using hot air has been adopted. However, in this method, the drying equipment and the processing equipment for drying exhaust gas become large, and the thermal efficiency is lower than in the case of using steam. Large exhaust gas treatment equipment is also required. In addition, even if it is said that heat is recovered from the steam incinerator and dried, the water content is about 50%, which means that the handling is not completely easy, and that the positional relationship between the drying equipment and the incinerator is inconvenient. is there.

[0012] In the operation of the drying equipment by the above method, only continuous operation was considered in terms of energy because heat loss at the time of starting and stopping and the required time are long.
In these methods, the recovered thermal energy is steam,
Since it is a heating medium or hot air, it cannot be stored or transported, and the locations of the drying equipment and the incineration equipment are limited to the same place. Therefore, it was not possible to install a drying facility where the operation of the incineration facility is problematic in terms of energy due to its small scale.

In many cases, a fluidized bed system is used as an incineration facility. In this case, silica sand is used for fluidization and as a heat transfer medium. However, since this silica sand has a large specific gravity, there is a problem that the pressure of the flowing air must be increased, and replenishment of the flowing silica sand is also a problem.

When sewage sludge is incinerated, sulfur oxides generated from the sludge itself and from auxiliary fuel must be removed. In many cases, the generated exhaust gas is brought into contact with caustic soda to absorb the sulfur oxides. It is converted to sodium sulfite or bow nitrate and discharged as wastewater. this is,
It is not an effective pollution control measure because it only converts air pollution into water pollution. As a countermeasure, it is necessary to install wet flue gas desulfurization equipment.

In most cases, the above-mentioned flue gas desulfurization is carried out by a wet method, so that the water vapor contained in the gas discharged from the chimney is condensed to generate white smoke, especially in the winter season. Equipment is installed. In this equipment, an exhaust gas cooling device that once lowers the temperature of the flue gas to reduce the amount of water vapor, and a device that raises the temperature of the cooled exhaust gas to a temperature at which white smoke does not occur again are installed, The equipment is complicated, and kerosene is sometimes burned to raise the temperature, which is completely contrary to energy saving.

In view of such circumstances, an object of the present invention is to economically dry and incinerate a large amount of dewatered sludge cake. In addition, the dewatered sludge cake that is dispersed and generated on a small scale is dehydrated and dried without using a heat source such as steam that cannot be stored and transported, and transported and aggregated economically without incurring secondary pollution. The goal is to be able to. Still another object of the present invention is to provide a system in which quicklime regenerated by incineration is reused for the dehydration and drying, and can be used as a cement raw material or a soil conditioner.

The present invention provides a dewatering and drying step of mixing sludge and quicklime to dewater and dry the sludge; heating the solid matter produced in the step to incinerate organic matter and heat the combustion of the organic matter. Incineration and regeneration process in which slaked lime is calcined to regenerate into quick lime by means of dewatering and drying incineration of sludge
In the system, in the incineration regeneration process, by chlorine bypass
The above object is achieved by a sludge dehydration drying incineration system characterized in that dechlorination is performed . .

[0018]

[Action]

"Dewatering / drying step" The water content of the sludge referred to in the present invention is generally 60% or more. The quicklime mixed with sludge in the present invention refers to one containing CaO as a main component and reacting with water in sludge to generate slaked lime and the like. Specifically,
Examples include quick lime, calcined dolomite, slag, blast furnace slag, and the like. The quicklime contains CaO in an amount of 30% or more, preferably 70% or more, and may have a particle size of 70 mm or less, preferably 30 mm or less.

In the present invention, the mixing ratio of sludge and quicklime is not particularly limited, but generally, quicklime / sludge is 1.5%.
0.5, preferably 1-0.7. This mixing is preferably performed by mechanical stirring using a paddle mixer, a pagmill or the like. When sludge and quicklime are mixed in this way,
Slaked lime is produced by the reaction of moisture in sludge and quicklime.
Therefore, the solid content generated in the dehydration step is composed of slaked lime and solid components in sludge.

This step is an exothermic reaction, and the amount of generated heat is directly transmitted to the water in the sludge, so that this step also functions as an efficient drying step. That is, the device also functions as a simple heat source-free dryer as described above. Since the heat source is unnecessary, it does not take long time to start and stop the dryer and auxiliary equipment.
No heat loss. In addition, the temperature rises to 100 ° C. or higher at the time of drying, and the fungus in the sludge is sterilized by the high PH of the generated slaked lime to form a sanitary and easily handled powder. Therefore, since the vehicle can be transported by a closed vehicle such as a tank truck, there is no adverse effect on the environment such as no occurrence of secondary pollution during transportation.

Since the equipment is simple as described above, this equipment can be installed in a business site where sludge is generated on a small scale without considering the increase in the number of operators. Further, since there is no possibility of secondary pollution caused by transportation, the generated solid can be easily transported and concentrated for incineration.

"Incineration and regeneration process" Sludge generally contains a large amount of organic matter, which is used as a fuel to incinerate the above-mentioned solids, and at the same time, calcine the slaked lime produced to regenerate it into quicklime. . As a method of this incineration regeneration, a fluidized-bed or airflow-type incineration calcination facility (insulator / calcina) is preferable. If the organic matter is low, use the auxiliary fuel to secure the necessary heat. Incineration calcination temperature is 600-10
00 ° C, preferably 650-800 ° C. Since the amount of heat required to dehydrate slaked lime is collected and stored in the form of quicklime, another heat recovery facility such as a waste heat boiler is not required.

If the sludge has a high chlorine content and the recycled quicklime is to be used as a raw material for cement, the chlorine bypass which is widely used in cement production during the incineration process is used.
(See, for example, JP-A-63-166741,
3-210049, JP-A-2-116649,
Perform dechlorination by placing a reference), a high chlorine content sludge can also be used as a cement raw material. As in the case of burning lime in a pulverized coal boiler and mixing calcined lime to perform simultaneous desulfurization of exhaust gas, the sludge incineration is performed with quick lime, so the sulfur oxides generated are absorbed and fixed by the lime and the gypsum Becomes Therefore, it is not necessary to install a separate flue gas desulfurization facility in this incinerator, and it is necessary to provide a facility that supplies a sulfur oxide absorbent such as caustic soda, a facility that treats generated wastewater, and a facility that prevents white smoke from flue gas. There is no.

"Drying and cooling step" If the dewatered and dried sludge introduced into the incineration and regeneration step still contains moisture, it can be dried by the exhaust gas from the incineration and regeneration step, and the temperature can be raised to a required temperature. can do. Although the temperature of the incinerated and regenerated quicklime is high, it can exchange heat with air for flowing or combustion.

[Recycling / Utilization] The quicklime containing incinerated ash regenerated in the above step can be recycled again in the above-mentioned sludge dewatering and drying step. In this case, since the inorganic matter (ash) contained in the sludge accumulates in the system, the regenerated quicklimes including incinerated ash or the solids before incineration can be used as a cement raw material or a soil conditioner. . The shortage will be supplemented with new quicklime.

By recycling quicklime in this way, it is not necessary to transport a large amount of quicklime from a quicklime calcination furnace located near a quicklime mine, and even when used as a raw material for cement, transport of a mixture of sludge and quicklime. The amount can be greatly reduced. That is, since the amount of limestone used by recycling is reduced, precious calcareous resources can be protected. Rather, the amount of carbon dioxide gas generated when calcining limestone into quick lime can be reduced, and global warming can be prevented.

[0027]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows sludge dewatering and drying facilities A and B and sludge incineration facility C. Sludge dewatering and drying equipment A is sludge incineration equipment C
And the sludge dewatering and drying facility B was located at a different business location. Sewage sludge hopper 1a, 1b
Was supplied with sewage sludge DM and temporarily stored. In the quicklime hopper 3a, quicklime regenerated in the sludge incineration facility C, that is, regenerated quicklime SS is directly stored, and new quicklime S for replenishment is also received from the tank truck TC. I have. On the other hand, the quicklime hopper 3b is adapted to receive fresh or regenerated quicklime S, SS from the tank truck TC.

The sewage sludge DM is supplied to sludge supply pumps 2a and 2b.
By the quick lime S, SS is quick lime supply conveyor 4a,
4b, each of which is a paddle mixer 5a,
5b and reacted. The solid content K generated by dehydration and drying is further subjected to dehydration and drying by the aging machines 6a and 6b. The generated dry powder DK is carried by the dry powder conveyors 9a and 9b and stored in the dry powder hoppers 10a and 10b.
In the sludge dewatering / drying facility B, the dried powder DK stored in the dry powder hopper 10b was transported to the sludge dewatering / drying equipment A by the tank lorry T and stored in the dry powder hopper 10a.

In the sludge dewatering and drying equipment B, the ripening machine 6b
Is passed through the bag filter 7b, thereby collecting dust such as slaked lime, and then the remaining steam is introduced into the absorption tower 11b by the ripening machine exhaust fan 8b. In the absorption tower 11b, the malodorous components such as water vapor and ammonia are simultaneously removed. Sulfuric acid R is added to improve the absorptivity of the malodorous components such as ammonia and to neutralize the PH of the liquid absorbing these components. The pH-adjusted absorbent is discharged as wastewater or, if necessary, returned to the original wastewater (sewage) treatment facility.

In the sludge dewatering / drying facility A, the steam generated from the ripening machine 6a is passed through the bag filter 7 in the same manner as in the facility B.
a, thereby collecting dust such as slaked lime. The remaining steam is sent to the sludge incinerator C by the ripening machine exhaust fan 8a, where the odorous components such as ammonia gas are burned and made harmless. .

In the sludge incineration plant C, the dry powder D stored in the dry powder hopper 10a from the sludge dewatering and drying plants A and B
The temperature of K is increased while being pneumatically transported by the exhaust gas from the incinerator / regeneration furnace 24, and is collected by the dry cyclone 21. The outlet gas of the dry cyclone 21 is absorbed by the exhaust fan 22, the fine powder is removed by the dry bag filter 23, and then released to the atmosphere. The fine powder MK collected by the dry powder bag filter 23 was supplied to the upper stage of the incineration regeneration furnace 24 together with the dry powder DK collected by the dry powder cyclone 21.

The incineration regeneration furnace 24 is a three-stage fluidized bed type,
The fluidizing air is blown into the lowermost stage of the furnace by the fan 27, the powder is supplied to the uppermost stage T, dried and dehydrated, falls naturally, is incinerated and regenerated in the middle stage M, and is cooled and discharged in the lower stage L. At this time, the sulfur oxides generated from the hot-air generating furnace react with the lime to form gypsum. When the amount of heat is insufficient in the middle stage M, hot air is supplied from the hot air generating furnace 25 to promote incineration regeneration. Fuel oil in a fuel tank 33 is supplied to the hot-air generating furnace 25 by a fuel pump 32, and combustion air is supplied by a primary air fan 26.

The quicklime containing the incinerated ash containing the incinerated ash was conveyed by an air conveyor, stored in the quicklime hopper 3a together with the fine powder of the quicklime cyclone, and then reused again in the sludge dewatering and drying facility A. The air for the air conveyor was absorbed by the quicklime fan 29 and passed through the quicklime bag filter 30 to be used as the secondary air of the hot air generator 25. or,
These were also stored in the quicklime hopper 31 and reused in the sludge dewatering and drying facility B by the tank truck TC, and were also used as a cement raw material and a soil conditioner.

The advantages of this embodiment are as follows. (1) Since quick lime is used as a heat medium, a: no heat source is necessary and simple in the drying equipment; b: no heat transfer surface in the drying equipment;
The material of the drying equipment does not need to be high-grade stainless steel. or,
d; Simple and easy even at business sites where sludge is generated on a small scale
E. Dewatering and drying can be efficiently performed; e; Dewatered and dried solids can be transported without fear of secondary pollution. f; Qualified because dewatered and dried solids can be combined with those at other business sites to efficiently incinerate and regenerate with large-scale equipment, and g; waste heat recovery boiler is not required for incineration and regeneration equipment Is unnecessary, and there is no operation stop due to periodic inspection.

(2) Since incineration is performed at the same time as lime, flue gas desulfurization equipment and white smoke prevention equipment are not required. Regenerated quicklime can be reused for dehydration and drying, and quicklime is transported over long distances. No need. (3) Even when used as a raw material for cement, a: the amount transported over long distances to the cement factory decreases, and b: the amount stored during the suspension of the cement factory decreases. Furthermore,
c; Sludge having a high chlorine content can also be used as a raw material for cement by providing a chlorine bypass in the incineration process. (4) Since quicklime is used for recycling, calcareous resources can be protected. Therefore, the amount of generated carbon dioxide is reduced, and global warming can be prevented.

[0036]

According to the present invention, the dewatering and drying step and the incineration regeneration step as described above are provided, so that the sludge is mixed with quicklime and dewatered and dried to form a solid content. It is incinerated by heating and regenerated into quicklime by the heat of combustion of the organic matter. Therefore, sludge can be efficiently treated, and the regenerated quicklime can be used as quicklime in the dehydration / drying step, or can be used as a soil conditioner or the like, which is economical. Furthermore,
Regeneration because chlorine is discharged out of the system by chlorine bypass
Since the lime is free of chlorine,
It is suitable as a raw material for

[Brief description of the drawings]

FIG. 1 is a flowchart showing an embodiment of the present invention.

[Explanation of symbols]

 DM Sludge S Quicklime SS Regenerated quicklime

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C04B 7/34 C04B 7/34 (72) Inventor Hiroshi Yasuda 2-7-5 Minamisuna, Koto-ku, Tokyo Inside Onoda Engineering Co., Ltd. (56) References JP-A-53-42452 (JP, A) JP-A-2-265700 (JP, A) JP-A-3-207497 (JP, A) JP-A-3-98700 (JP, A) Kohei 2-53119 (JP, B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) C02F 11/00-11/20

Claims (1)

(57) [Claims] A dewatering and drying step of mixing sludge and quicklime to dewater and dry the sludge; heating the solid matter produced in the step to incinerate organic substances and slaked lime by heat of combustion of the organic substances. dehydrating and drying incineration system odor consisting sludge; incineration regeneration step and which was calcined to play quicklime to
Te; in the incineration regeneration step, dechlorination is performed by chlorine bypass
Dehydrating and drying incineration systems sludge, characterized in that.