JPH07305823A - Treating method for liquidlike organic sludge - Google Patents

Abstract

PURPOSE:To eliminate public pollution of dilute liquid of by-product produced when liquidlike organic sludge is concentrated by burning concentrated material concentrated from concentrated liquid containing a predetermined quantity of solid content in a burning furnace, atomizing the dilute liquid containing substantially no solid content into the furnace, and decomposing organic material in the dilute liquid. CONSTITUTION:Concentrated liquid (the concentration of its solid content is 10-50wt.% or particularly 30-50wt.%) recovered to a concentrated liquid tank 105 is introduced to a burner 113. Further, oxygen or oxygen-containing gas is introduced as combustion support gas to the burner 113. The concentrated liquid and the oxygen gas or the oxygen-containing gas introduced to the burner 113 are sprayed from the burner 113 into a burning furnace 114 to form a burning flame 115 in the furnace 114. On the other hand, dilute liquid recovered to a dilute liquid tank 104 is introduced into a sprayer 116, and sprayed into the furnace 114. The dilute liquid sprayed into the furnace 114 is instantaneously heated to the temperature in the furnace 114 by the flame 115, and organic material contained in the dilute liquid is decomposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating organic sludge such as surplus sludge generated from a biological treatment apparatus for organic wastewater represented by sewage.

[0002]

2. Description of the Related Art Sewage sludge, which is a typical organic sludge,
Approximately 50 million m ³ nationwide (concentrated sludge standard: water content 9
It is an enormous amount (8%), and it is increasing year by year.
Generally, since organic sludge such as sewage sludge contains a large amount of organic substances such as proteins, fats and carbohydrates along with water, it easily rots, and it is necessary to stabilize, detoxify, and reduce the volume from the viewpoint of foul odor prevention and public health. It is said that. In many sewage treatment plants in large cities, combustion treatment of sludge is performed from the viewpoint of difficulty in securing landfill sites. According to Japanese Patent Laid-Open No. 5-337497, there is proposed a method in which, when burning an organic sludge, the organic sludge is subjected to a high temperature and high pressure treatment in advance to obtain a liquefied substance, and then the liquefied substance is subjected to a combustion treatment. According to this method, since the organic sludge is supplied to the combustion furnace as a liquefied material with good fluidity,
In the combustion process, a spray combustion method with good combustion efficiency can be adopted, and there are advantages that the combustion furnace can be downsized and operation control becomes easy.

However, when the water content of the liquid organic sludge is high, the lower calorific value based on water content is low and the flame temperature at the time of combustion is low, which makes it difficult to form a flame and is contained in the sludge. There is a problem that the melting of the existing inorganic material does not occur or is insufficient. When the melting of the inorganic substances contained in the organic sludge is insufficient, the ash obtained will be bulky and the heavy metals contained in it will easily elute, and the ash will be landfilled. When treated, the heavy metal content may elute and cause environmental pollution.

The inventors of the present invention have previously conducted a burning treatment of liquid organic sludge by keeping at least a part of the burning flame at a temperature equal to or higher than the melting temperature of the inorganic substance contained in the sludge. A method for melting an inorganic substance has been proposed (Japanese Patent Application No. 5-202089). In this way,
A method of concentrating liquid organic sludge and burning the concentrate is included to increase the flame temperature. When the liquid organic sludge is concentrated, a dilute liquid containing organic substances is by-produced, but since this dilute liquid has a high concentration of organic substances and produces a foul odor, it cannot be discharged as it is to the river and its pollution-free treatment is performed. Needed.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a method of concentrating liquid organic sludge and subjecting the concentrated liquid to combustion treatment, whereby a dilute liquid produced as a by-product in concentrating the liquid organic sludge is treated to be pollution-free. The task is to provide a method of doing so.

[0006]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, according to the present invention, a concentrated liquid having a solid content concentration of 10 to 50% by weight and a dilute liquid having a solid content concentration of less than 10% by weight or substantially no solid content are obtained from liquid organic sludge. A step of burning the concentrate obtained in the concentrating step in a combustion furnace, and spraying the dilute solution obtained in the concentrating step into the combustion furnace to decompose organic matter in the dilute solution There is provided a method for treating a liquid organic sludge, which is characterized by comprising steps.

The organic sludge used as a raw material in the present invention includes sewage sludge discharged from a normal sewage treatment plant, surplus sludge discharged from various organic wastewater biological treatment apparatuses, and the like. As the liquid organic sludge in the present invention, an organic sludge having a relatively large water content before dehydration is also an object to be treated, but a dehydrated sludge obtained by temporarily dehydrating the organic sludge having a high water content. At 150 ° C
The liquid organic sludge obtained by maintaining the above temperature and the pressure of the saturated steam pressure of the temperature or more becomes a preferable object. Mechanical dehydration (vacuum dehydration, pressure dehydration, belt press dehydration and centrifugal dehydration) is usually used for dehydration of the above-mentioned organic sludge, but is not particularly limited. However, it is desirable to add a sludge conditioning chemical to the organic sludge before dehydration, and it is particularly advantageous to add a polymer flocculant. Therefore, regarding the dehydration method as well, it is desirable to use belt press dehydration or centrifugal dehydration, which is suitable for adding the polymer flocculant. The dehydration of this organic sludge has a water content of 60-9.
It is advisable to carry out the treatment so as to be 0% by weight, preferably 65 to 75% by weight.

In order to convert the dehydrated sludge into a liquefied product, the dehydrated sludge has a reaction temperature of 150 ° C. or higher, preferably 200 to 250 ° C. and a pressure higher than the saturated steam pressure at the reaction temperature, for example, a reaction temperature of 200 ° C. In case of, 16kg /
It may be maintained under a reaction pressure of not less than cm ² (absolute pressure). The dehydrated sludge can be liquefied in the presence of an alkaline substance as a liquefaction promoter, if necessary.
This alkaline substance, with respect to the solid content in the dehydrated sludge,
It is advisable to add it in a proportion of 0 to 20% by weight, preferably 0 to 5% by weight. Examples of the alkaline substance include alkali metal compounds such as sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium formate, potassium formate, calcium oxide, calcium hydroxide, and hydroxide. Examples thereof include alkaline earth metal compounds such as magnesium. The time for holding the dehydrated sludge under the reaction conditions varies depending on the type of the target sludge, but is generally within 120 minutes, usually
0 to 60 minutes. The liquefaction device may be an indirect heating type heat exchanger, but since it handles sludge in a solid state, it has a scraper type heat exchanger with a scraper inside or a screw type heat exchanger with a helical blade. Use is desirable. As the pressure in the liquefaction reaction, the self-generated pressure of water vapor from the sewage sludge can be used, but if necessary, for example, nitrogen gas, carbon dioxide gas, argon gas or the like can be used for pressurization. The sludge liquefied material thus obtained has excellent fluidity and can be sufficiently pumped.

In the present invention, the liquid organic sludge obtained as described above is concentrated, and the concentrated liquid is ejected from the burner of the combustion furnace together with the oxygen-containing gas for combustion in the form of fine particles for combustion. The diluted liquid obtained during the concentration is sprayed into a combustion furnace to decompose organic substances contained in the diluted liquid. Air, oxygen-enriched air, or oxygen gas is used as the oxygen-containing gas for combustion. The ejected particles of the concentrated liquid ejected from the burner are 300 μm or less, preferably 30 to 150 μm. The burner type is not particularly limited, but it is preferable to use an external or internal mixed two-fluid atomization burner, a low pressure air atomization burner, or the like.

FIG. 1 shows an example of the structure of the burner section of the combustion furnace used in the present invention. FIG. 2 shows an enlarged view of the atomizer tip. 1 and 2, the burner portion is composed of an atomizer body 1 and an air register 6, and the atomizer body 1
Is composed of an inner pipe 2 to which a concentrated liquid of liquid organic sludge (hereinafter, also simply referred to as a concentrated liquid) is supplied and an outer pipe 3 forming a passage for a spray medium, and is attached to the air register 6. A concentrated liquid supply line 4 is connected to the inner pipe 2, a spray medium supply line 5 is connected to the outer pipe 3, and a combustion oxygen-containing gas supply line 7 is connected to the air register 6. Further, 8 is a burner tile, 9 is a flame holding chamber, 1
Reference numeral 0 indicates a combustion furnace, 11 indicates a combustion furnace wall, and 12 indicates a combustion chamber. The furnace wall 11 is made of a heat insulating material that can withstand a temperature of 800 to 1200 ° C. In the combustion furnace 10 of FIG. 1, the concentrated liquid supplied from the concentrated liquid supply line 4 is atomized by the spray medium supplied from the spray medium supply line 5, and is jetted from the tip of the atomizer body 1. Air, oxygen-enriched air, oxygen gas or the like is used as the atomizing medium.
On the other hand, from the oxygen-containing gas supply line for combustion 7, a predetermined amount of oxygen-containing gas for combustion is supplied from around the atomizer body 1. The atomized concentrated liquid ejected from the burner and the oxygen-containing gas for combustion are mixed and ignited in the flame holding chamber 9 and burned in the combustion chamber 12.

In the present invention, at the time of burning the concentrated liquid, the temperature of at least a part of the combustion flame is maintained at the melting temperature of the inorganic substances contained in the sludge or higher. The melting temperature of the inorganic substance in the sludge varies depending on the type of sludge, but generally, the inorganic substance can be melted by heating at 1200 ° C. or higher. Therefore, in order to perform the melting of the inorganic substance in the combustion flame, the temperature of at least a part of the flame is set to 1200 ° C.
As described above, the temperature may preferably be maintained at 1400 to 1500 ° C.

FIG. 3 shows an example of a flow sheet for carrying out the present invention. In FIG. 3, 101 is a liquid organic sludge storage tank, 102 is a liquid organic sludge supply pump, 1
Reference numeral 03 is a concentrator, 104 is a diluted liquid tank, 105 is a concentrated liquid tank, 106 is a diluted liquid supply pump, 107 is a concentrated liquid supply pump, 113 is a combustion burner, 114 is a combustion furnace,
Reference numeral 115 is a combustion flame, and 116 is a diluting liquid spraying device. In order to carry out the present invention according to the flow sheet shown in FIG. 3, the liquid organic sludge is concentrated from the storage tank 101 by the liquid organic sludge supply pump 102.
3 and is separated into a concentrated liquid and a dilute liquid.
The concentrated liquid is collected in the tank 105, and the diluted liquid is stored in the tank 10.
Recovered in 4. As the concentrating device 103, various conventionally known devices utilizing a specific gravity difference separation method such as static separation or centrifugal separation or an evaporative concentration method can be used. The solid content concentration in the concentrated liquid is 10 to 50% by weight, and particularly 30 to 50% by weight. On the other hand, the solid content concentration in the dilute liquid is less than 10% by weight, and particularly 0 to 5% by weight. The concentrated liquid collected in the concentrated liquid tank 105 is supplied to the concentrated liquid supply pump 10
7, burner 113 through valve 108, line 109
Will be introduced to. Further, oxygen or oxygen-containing gas as a combustion supporting gas is introduced into the burner 113 through the line 120. The concentrate and oxygen or oxygen-containing gas introduced into the burner 113 are spray-combusted from the burner tip into the combustion furnace 114, and a combustion flame 115 is formed in the furnace.

On the other hand, the diluted liquid collected in the diluted liquid tank 104 is introduced into the spraying device 116 through the diluted liquid supply pump 106, the line 111 and the valve 112, and is sprayed from there into the furnace. The diluted liquid sprayed in the furnace is instantly heated to the temperature in the furnace, and the organic substances contained in the diluted liquid are decomposed. The number of the spraying devices 116 is not limited to one and may be plural. Further, the dilute liquid can be sprayed toward the central portion in the combustion furnace by a spraying device, but it is preferably sprayed toward the furnace wall surface. When spraying toward the furnace wall surface, the temperature of the furnace wall can be lowered and the durability of the furnace wall can be improved. The combustion gas generated by the combustion of the concentrated liquid in the furnace and the decomposition gas generated by the decomposition of the organic substances in the diluted liquid are discharged to the outside of the furnace through the line 117. The high-temperature exhaust gas discharged outside the furnace is subjected to heat recovery from the exhaust gas through a heat exchanger and then sent to the exhaust gas treatment facility in the subsequent stage where the harmful gas contained in the exhaust gas is removed and then released to the atmosphere. Is released.

In the present invention, the concentrated liquid is combusted in the burner, and at least a part of the combustion flame is maintained at a temperature equal to or higher than the melting temperature of the inorganic substance contained in the sludge. Therefore, the inorganic substances in the sludge are melted in the flame and become molten slag. This molten slag is extremely fine, and 50% or more of the particles have a particle size of 5 μm or less. Further, the molten slag exhibits a spherical shape due to the effect of surface tension when the inorganic substance is melted. The molten slag flows out of the furnace together with the combustion gas, but is separated and recovered from the combustion gas by a filter installed outside the furnace.

In the present invention, the temperature of at least a part of the combustion flame needs to be maintained at a high temperature as described above, but the temperature of the entire furnace does not need to be at such a high temperature.
In the case of the present invention, the temperature of the inner surface of the furnace wall is 500 to 1000 ° C.
It is not necessary to use a special furnace wall material, and by keeping the surface temperature inside the furnace wall at such a low temperature, the loss of heat escaping from the inside of the furnace to the outside of the furnace Is also suppressed.

In the case of the present invention, at least a part of the flame 115 is maintained at the melting temperature or higher of the inorganic substance contained in the sludge, and the inorganic substance is melted when the concentrated liquid is burned. Since an inorganic substance usually melts at a temperature of about 1200 ° C., a flame having a temperature of 1200 ° C. or higher may be formed. Further, in the combustion of such a concentrated liquid, the temperature range of 700 to 800 ° C. is set for the entire furnace. Therefore, the organic matter in the dilute liquid ejected into the furnace is easily decomposed in the furnace.

When the concentrated liquid is burned, the temperature of the combustion flame changes depending on the heat value of the concentrated liquid, and the combustion flame temperature can be raised by increasing the heat value. For example, when the concentrated liquid is burnt by air, the lower heating value of the concentrated liquid is 1260 kcal / kg, 2150
At kcal / kg and 3050 kcal / kg, the maximum temperature of the combustion flame is 1170, respectively.
℃, 1520 ℃ and 1740 ℃. Also, the lower heating value of the concentrated liquid changes depending on the water content of the concentrated liquid, and for example, the lower heating value in the anhydrous state is 3970 kcal.
The water content of the concentrated liquid is 20% by weight, 40%
At the weight% and 60 weight%, the lower heating value is
3050 kcal / kg and 2150 kcal, respectively
/ Kg and 1260 kcal / kg. The lower heating value of the concentrated liquid is expressed by the following equation. H (L) = H (U) −600 × W In the above formula, H (L) represents the lower heating value (kcal / kg). H (U) indicates a higher calorific value (kcal / kg), which is a calorific value measured by a calorimeter and is a calorific value including latent heat when water vapor is condensed. W represents the amount of water vapor (kg) generated during combustion. The flame temperature can also be adjusted by controlling the preheating temperature of the oxygen-containing gas for combustion, the oxygen concentration in the oxygen-containing gas for combustion, and the addition amount of the combustible substance. Therefore, the flame temperature can be adjusted to an arbitrary range by combining these methods. Hereinafter, the method for adjusting the flame temperature will be described in detail.

(Control Method for Preheating Temperature of Oxygen-Containing Gas for Combustion) The combustion flame temperature changes with the preheating temperature of the oxygen-containing gas for combustion, and the flame temperature can be raised by increasing the preheating temperature. For example, when burning a concentrated liquid having a water content of 60% by weight, the preheating temperature of the combustion air is set to 20.
When the temperature is raised to 0 ° C, 400 ° C and 600 ° C, the maximum combustion flame temperatures are 1250 ° C, 1350 ° C and 1 ° C, respectively.
It will be about 450 ° C.

(Method of Controlling Oxygen Concentration in Oxygen-Containing Gas for Combustion) The combustion flame temperature changes depending on the oxygen concentration in the oxygen-containing gas for combustion, and the combustion flame temperature can be raised by increasing the oxygen concentration. it can. For example, the water content is 6
When burning 0% by weight of concentrated liquid, when the oxygen concentration in the oxygen-containing gas for combustion is 21%, 40% and 60%, the maximum combustion flame temperature is 1200 ° C.,
It becomes about 1550 and 1750 ° C. Furthermore, when a concentrated liquid having a water content of 50% by weight is burned, when the oxygen concentration in the oxygen-containing gas for combustion is 21% and 40%, the temperatures are about 1300 ° C. and 1850 ° C., respectively.

(Method of controlling the amount of combustible substance added) The temperature of the combustion flame can be adjusted by the amount of combustible substance added to the concentrate. The concentrated liquid containing the combustible substance has an increased apparent calorific value, and the flame temperature rises corresponding to the added amount of the combustible substance. Examples of combustible substances include hydrocarbon oils such as heavy oil and kerosene, various waste oils, various organic wastes, and pulverized coal.

[0021]

EXAMPLES Next, the present invention will be described in more detail by way of examples.

Example 1 Sewage sludge was selected as the organic sludge, and a dehydrated cake of mixed raw sludge discharged from the treatment plant of the standard activated sludge method was used for the test. This sludge is dehydrated by a belt press after adding a polymer flocculant. Its typical properties are
The water content is 79% by weight, the organic matter ratio is 78% by weight, and the lower heating value is 3940 kcal / kg.

The dehydrated sludge was liquefied using a continuous sludge liquefaction device (processing capacity: 200 kg / hr). This equipment is composed of a press-in pump (snake pump), a reactor (scraping surface heat exchanger), a cooler (thin film downflow heat exchanger), a decompression valve and a heat medium boiler. Was supplied by a heat medium boiler. The dehydrated sludge was introduced into the reactor by a press-fitting pump, and heated to about 265 ° C while scraping was performed to prevent clogging and promote heat transfer. The residence time at the reaction temperature was about 60 minutes. Since the dehydrated sludge was sufficiently liquid at the outlet of the reactor, it was made to flow down while forming a thin film on the inner tube of the double tube, and cooled to 100 ° C. or lower with the cooling water supplied to the outer tube. Then, the pressure was reduced to atmospheric pressure with a pressure reducing valve and stored in a drum. Liquefaction operation,
It was carried out for about 10 hours, and about 400 kg (two drums) was used as a stationary sample to make a sludge liquefied material for experiments. Next, 100 parts by weight of the sludge liquefied material having a solid content concentration of 21% by weight obtained as described above was treated with a centrifuge to obtain 48 parts by weight of a concentrate having a solid content concentration of 35% by weight, and a solid content concentration of 48% by weight. 52 parts by weight of a dilute solution giving an offensive odor of 7.5% by weight was obtained.

The concentrated liquid thus obtained was sent to an external mixing type high-pressure two-fluid spray burner at a flow rate of 150 kg / h by using a snake pump, sprayed in a combustion furnace and burned. At this time, oxygen-enriched air containing 55 vol% oxygen was used as the oxygen-containing gas for combustion. Under this condition, the liquefied material formed a flame and burned, and the burning was continued. Flame combustion was continued for 1 hour or more, and the combustion flame temperature at this time was 1,200 ° C. or higher. Next, when the combustion became stable, the diluted liquid obtained above was sprayed into the combustion furnace at a flow rate of 150 kg / h to decompose organic substances in the diluted liquid. Further, a sampling probe was inserted into the exhaust gas duct outlet and connected to a bag filter to collect the molten slag. Microscopic examination of the molten slag showed it to be a very small sphere.
This means that the inorganic component melted in the combustion flame and became spherical due to surface tension. Next, Table 1 shows the analysis results of the component composition of this molten slag.

[0025]

[Table 1] Table 2 shows the results of measuring the particle size distribution of the molten slag.

[0026]

[Table 2]

[0027]

According to the present invention, since the liquid organic sludge is once concentrated and is spray-burned in the state of a concentrated liquid, the combustion furnace of the combustion furnace is compared with the case where the liquid organic sludge is directly spray-burned. In addition to being small, it has the advantage that it can be burned stably and the flame temperature rises. Therefore, in the case of the present invention, the liquid organic sludge can be burned efficiently and economically, and the inorganic substances contained in the sludge can be efficiently melted into slag. Further, according to the present invention, the dilute liquid containing the malodorous organic matter produced as a by-product during the concentration of the liquid organic sludge is sprayed into the combustion furnace to decompose the organic matter contained in the dilute liquid. There is no problem of environmental pollution due to the liquid.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of the vicinity of a burner of a combustion furnace.

FIG. 2 shows an enlarged view of the atomizer tip.

FIG. 3 shows an example of a flow sheet for carrying out the present invention.

[Explanation of symbols]

 1 atomizer body 2 inner pipe 3 outer pipe 4 concentrated liquid supply line 5 atomizing medium supply line 6 air register 7 oxygen-containing gas supply line for combustion 8 burner tile 9 flame holding chamber 10 combustion furnace 11 combustion furnace wall 12 combustion chamber 101 liquid organic Sludge storage tank 102 Liquid organic sludge supply pump 103 Concentrator 104 Diluted liquid tank 105 Concentrated liquid tank 106 Diluted liquid supply pump 107 Condensed liquid supply pump 108, 112 Valve 113 Burner 114 Combustion furnace 115 Combustion flame 116 Spraying device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical display location F23G 7/04 ZAB C (72) Inventor Chisato Tomizawa 2-8-1, Nishishinjuku, Shinjuku-ku, Tokyo Tokyo Metropolitan Sewerage Bureau (72) Inventor Koji Ogata 2-8-1, Nishishinjuku, Shinjuku-ku, Tokyo Tokyo Metropolitan Sewer Bureau (72) Inventor Akira Suzuki 1-4-9 Kawagishi, Toda City, Saitama Organo Corporation (72) Inventor Shinji Ito 5-5-16 Hongo, Bunkyo-ku, Tokyo Organo Corporation (72) Inventor Nobuyuki Kojima 5-5-16 Hongo, Bunkyo-ku, Tokyo Organo Corporation ( 72) Inventor Shinji Asada 2-4-7 Kyomachibori, Nishi-ku, Osaka City, Osaka Prefecture Chugai Furnace Industry Co., Ltd. (72) Makoto Inoue 2-chome, Kyomachibori, Nishi-ku, Osaka City, Osaka Prefecture 4-7 Chugai Furnace Industry Co., Ltd. (72) Inventor Masao Nonohiro 2-4-7 Kyomachibori, Nishi-ku, Osaka City, Osaka Prefecture Chugai Furnace Industry Co., Ltd.

Claims (2)

[Claims] 1. A liquid organic sludge having a solid content of 10
˜50 wt% concentrate, a concentration step to obtain a dilute solution having a solid content concentration of less than 10 wt% or substantially no solid content, and a combustion treatment of the concentrate obtained in the concentration step in a combustion furnace. And a decomposition step of decomposing organic matter in the diluted liquid by spraying the diluted liquid obtained in the concentration step into the combustion furnace, and a method for treating liquid organic sludge. 2. The method according to claim 1, wherein the liquid organic sludge is obtained by dehydrating the organic sludge and subjecting the dehydrated sludge to high temperature and high pressure treatment.