JPH0463200A - Method for recovering oily matter from reaction product produced by converting sludge into oil - Google Patents

Abstract

PURPOSE:To efficiently separate and recover oily matter from a reaction product produced by converting sludge into oil by bringing watercontg. org. sludge into a thermochemical reaction at high temp. and pressure and subjecting the resulting reaction product to separation according to density difference while keeping the high temp. and pressure. CONSTITUTION:Org. sludge dehydrated to <=85%, usually 70-80% water content is introduced into the preheating section 1 of a reaction apparatus through a line 12, preheated, introduced into the reaction section 2 through a line 13 and heated to produce oily matter by a thermochemical reaction. At this time, the reaction temp. is 250-350 deg.C, preferably 300-320 deg.C, the reaction pressure is the pressure of satd. steam at the reaction temp. or above and the reaction time is usually 5-180min. The resulting reaction product is introduced into a high temp. and pressure separator 3 through a line 14 and a heavy liq. as a mixture of oily matter having higher density than water with residual solid and water is separated from a light liq. as a mixture of oily matter having lower density than water with water.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a sludge oil obtained by thermochemically reacting organic sludge such as surplus sludge generated from a biological treatment device for organic wastewater under high temperature and high pressure conditions. The present invention relates to a method for separating and recovering oily substances from chemical reaction products.

[Prior art and its problems] Sewage sludge, a typical organic sludge,
It is a huge amount of 0 million ms (98% water content),
The number is increasing year by year. Conventionally, around 80% of such sewage sludge is dehydrated and then disposed of in a landfill.However, in this case, there is a problem in securing a landfill, and with the development of urbanization, the landfill is becoming more and more Securing it is becoming more difficult every year. In addition, sewage sludge can also be incinerated, and in this method, the treated product is incinerated ash whose volume is significantly reduced compared to the amount of sewage sludge that is the raw material to be treated. This is a very effective method from the point of view of reducing the volume of raw materials. However, this method has the problem that it requires a large amount of thermal energy to evaporate water in the sewage sludge, resulting in a high running cost and is not economical. In response to this current situation, the present inventors
Japanese Patent Laid-Open No. 136299/1983 proposes a method for liquefying sewage sludge. In this method, organic matter in sewage sludge is subjected to a reaction treatment under alkaline conditions at a reaction temperature of 250 to 350°C under pressure higher than the saturated water vapor pressure of the reaction temperature, and then the obtained reaction treatment product is cooled. , the reaction product is first separated into an aqueous phase and a slurry phase, and then the separated slurry phase is further separated into an oily substance and a residual solid. However, with this method, it is very difficult to mechanically extract only the oily substance from the separated slurry phase, and for this purpose,
Additional extraction and distillation operations are required. Therefore, the overall oil conversion process is still not efficient and has many practical problems.

[Problems to be solved by the invention] The present invention aims to solve the above-mentioned problems encountered in the conventional treatment of organic sludge such as sewage sludge, and to provide a method for efficiently separating and recovering oily substances from sludge oil conversion reaction products. Take it as a challenge.

[Means for Solving the Invention] As a result of intensive research to solve the above problems, the present inventors have completed the present invention.

That is, according to the present invention, in a method for thermochemically reacting water-containing organic sludge under high temperature and high pressure conditions to obtain an oily substance from the reactant, after the reaction, the reactant is
A method for recovering oily substances from a sludge-oiling reaction product is provided, which is characterized in that the oily substances are separated as a light liquid by performing density difference separation while maintaining a high temperature and high pressure state of 0.degree. C. or higher.

In the present invention, the organic sludge used as the raw material to be treated includes sewage sludge discharged from ordinary sewage treatment plants, surplus sludge discharged from various organic wastewater biological treatment equipment, etc. There are no particular restrictions as long as it is sludge. However, if organic sludge contains too much water, it will consume a large amount of thermal energy to reach the temperature required for thermochemical reactions, so it is desirable to dehydrate the organic sludge to a water content of 85% or less. .

To carry out the method of the present invention, organic sludge is held at high temperature and pressure to perform a thermochemical reaction, and then density difference separation is simply performed at a temperature of 250° C. or higher. If necessary, it is also possible to bring the organic sludge under alkaline conditions in order to accelerate the reaction. In this case, alkaline substances are usually used to form alkaline conditions, examples of which include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium formate. , alkali metal compounds such as potassium formate, calcium oxide,
Examples include alkaline earth metal compounds such as calcium hydroxide and magnesium hydroxide.

Although the reaction treatment in the present invention is carried out at high temperature and high pressure,
In this case, the reaction temperature is generally 250-350°C, preferably 300-320°C, and the reaction pressure is equal to or higher than the saturated water vapor pressure at the reaction temperature, for example, 41 kg/cm"abs at 250°C, 300°C In the case of 88k
g/cm"abs or more. At this time, the holding time at the reaction temperature (reaction time) may be at least 60 minutes at 250°C and at least 5 minutes at 300°C, but In order to reduce the amount of organic matter transferred to the phase, it is desirable to carry out the reaction at as high a temperature as possible for a long time.

However, increasing the reaction temperature or conducting the reaction for a long time will increase the initial cost, so it is appropriate to set the reaction temperature to 300°C or less and the holding time to 60 minutes or less.

In the present invention, after the oil conversion reaction, the reactants are separated by density difference at a temperature of 250° C. or higher, preferably around 300° C., but the method may be based on gravity sedimentation or centrifugal sedimentation, Not particularly limited. As typical methods, a static separation method can be used for gravity sedimentation, and a hydrocyclone or the like can be used for centrifugal sedimentation. The light liquid thus separated is obtained in a mixed state of an oily substance and an aqueous phase, and ordinary oil-water separation means are applied to separate the oily substance from this mixture.

In general, separation means that utilize the density difference between the oily substance phase and the aqueous phase, such as gravity separation or centrifugal separation by standing still, or separation means that utilizes the coreless effect, etc. can be adopted. .

Further, in the present invention, the pressure can be generated by using self-generated pressure due to water vapor from sewage sludge, but if necessary, it can also be pressurized using, for example, nitrogen gas, carbon dioxide gas, argon gas, etc.

In the present invention, the oily substance obtained is only a low-density component of the oily substance produced in a thermochemical reaction, has a high calorific value, and has a low viscosity, so it can be used satisfactorily as a fuel oil.

Next, FIG. 1 shows a flow sheet of a preferred embodiment of the present invention. In FIG. 1, l is a reactor preheating section, 2 is a reactor reaction section, 3 is a high temperature and high pressure separation device,
4 is a first cooler, 5 is a first pressure reducing device, 6 is a solid-liquid separator, 7 is an incinerator, 8 is a waste heat boiler, 9 is a second cooler, I
O indicates a second pressure reducing device, and II indicates an oil-water separator.

Organic sludge dehydrated to a water content of 85% or less, usually 70 to 80%, is introduced into the reactor preheating section 1 through a line 12. This reactor preheating section is a heat exchange type reactor,
A heating medium is introduced through line 24 to preheat the organic sludge within the reactor. The heating medium used here is desirably the amount of heat recovered by the first cooler 4 in the latter stage. The preheated sludge is introduced into the reaction section 2 through the line 13, heated, and produces an oily substance through a thermochemical reaction. The conditions at this time are that the reaction temperature is 250 to 350'C1, preferably 300 to 320C, and the reaction pressure is equal to or higher than the saturated water vapor pressure at the reaction temperature. The reaction time is usually 5 to 1
It is 80 minutes.

The type of reactor employed here is preferably a surface heat exchanger, but is not particularly limited. In FIG. 1, the preheating section 1 and the reaction section 2 may be separated, or they may be an integrated reactor. The reactants pass through line 14,
The heavy liquid (a mixture of oily substances with a density higher than that of water, residual solids, and water) is introduced into the high temperature and high pressure separation device 3, and the light liquid is separated
, (a mixture of an oily substance with a density lower than that of water) and water.

The temperature during separation may be 250° C. or higher. The separation device here is preferably a gravity settling tank or a hydrocyclone that does not require a drive unit, but is not particularly limited.

The heavy liquid is introduced into the first cooler 4 through the line 15 and is cooled down to 100° C. or lower by applying heat to the heat medium, and the heat medium passes through the line 24 and heats the preheating section 1 . The type of cooler is preferably a thin film falling heat exchanger, but is not particularly limited. The cooled heavy liquid passes through line 1G and is reduced in pressure to atmospheric pressure by first pressure reducing device 5, and then introduced into solid-liquid separation device 6 through line 17. Here, the heavy liquid is dehydrated to become a residue cake with a low moisture content, and is fed into the incinerator 7 via a line 19. Meanwhile, the separated water is returned to the water treatment system through line 18.31. In the incinerator 7, the leftover pickle cake and combustion air introduced from the line 20 are mixed and incinerated without adding auxiliary fuel. After incineration, the generated ash is discharged from the system through line 21, and high-temperature combustion exhaust gas is introduced into waste heat boiler 8 through line 22. Here, the exhaust gas imparts its retained heat to the heat medium and is dissipated into the atmosphere through the line 23.

At this time, waste gas processing equipment such as dust collection and smoke cleaning may be installed as necessary. The heat medium heated by the waste heat boiler is used as a heat source for the reaction section 2.

On the other hand, the light liquid separated by the high-temperature and high-pressure separator 3 is transferred to the line 2.
6 and is introduced into the second cooler 9 and cooled down to 100°C or less, then passed through the line 27 to the second pressure reducing device 10.
The pressure is reduced to atmospheric pressure. Again, as a cooler,
It is preferable to use a thin film falling heat exchanger. Thereafter, the light liquid is introduced into the oil/water separator 11 via line 28 and separated into an aqueous phase and an oily substance. As this oil/water separator, it is possible to adopt a separation means that utilizes a density difference, such as gravity separation or centrifugal separation by standing still, or a separation means that utilizes a coreless effect. The aqueous phase separated in the oil-water separator is returned to the water treatment system through line 29.31. The oily material is recovered through line 30 and used as excess oil.

[Effects of the Invention] As explained above, according to the present invention, sewage sludge, which has conventionally been treated as industrial waste, can be treated with a high calorific value (8500
kcal/kg) and low viscosity (200 cP or less at 50°C), it can be converted into an oily substance useful as a liquid fuel. In this case, the yield of oily substances is about 10-20% based on dry organic matter, which corresponds to 20-40% of the total amount of oily substances produced in the thermochemical reaction.

However, more than 50% of the total oil produced is
Considering that the oil is consumed for the reaction, the method of the present invention is very advantageous because it allows a high-grade oily substance to be obtained as a surplus without performing any special extraction process or distillation operation. Therefore, the method for treating organic sludge into oil according to the present invention can be said to be a technically and economically very advantageous method.

[Example] Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Sewage sludge was selected as the organic sludge, and a dehydrated cake of mixed raw sludge discharged from a treatment plant using the standard activated sludge method was used in the test. This sludge was dehydrated using a belt press after adding a polymer flocculant. Its typical properties are shown in Table-1.

Table-1 A high-pressure autoclave-type device was used as the experimental device.

This equipment consists of an autoclave (inner volume: 300 d) installed in an electric heating furnace, and a sealed separation tube (inner volume: 1000 m, 100 d) installed separately in the autoclave.
It consists of Inside the autoclave is a stirrer,
A thin tube with a U-shaped tip is arranged vertically. The opening at the tip of this capillary is bent into a U-shape and is held at a height of a certain distance from the bottom of the autoclave, so that the contents of the autoclave above a certain level can be discharged to the outside through the capillary. There is. The other end of this thin tube is led out through the lid of the autoclave and connected to a connecting tube, and this connecting tube is connected to a separation tube via a cooler and a valve.

After pre-pressurizing the pressure inside the separation tube to 90 kg/cnJG with nitrogen gas, 170 g of the dehydrated sludge was transferred to a container with an internal volume of 30 kg/cnJG.
The autoclave was filled and sealed, thoroughly purged with nitrogen gas, and pressurized to 30 kg/cm'G.

Next, stirring was started and heating was started at the same time. Immediately after the temperature inside the autoclave reached 300°C, stirring was stopped, and the contents were allowed to stand at 300°C for 120 minutes. At this time, the pressure inside the autoclave was 132 kg/cm"
It rose to G. Now, when the valve located between the autoclave and the separation tube is gradually opened, the upper light liquid of the product in the autoclave is pushed out through the thin tube due to the pressure difference between the autoclave and the separation tube, and the cooler The mixture was cooled and transferred to a separation tube. Approximately 40g obtained here
When the light liquid is left standing for a day and night, a gray oily substance at the top and
It was separated into a dark brown transparent aqueous phase at the bottom. The heavy liquid remaining in the autoclave and the light liquid transferred to the separation tube were collected, and each was separated into three phases, an oily substance, a residual solid substance, and an aqueous phase, by a solvent extraction method using methylene chloride. 2
The separation results shown in are obtained.

Table 2 As is clear from Table 2, the amount of oily substances that migrated into the separation tube was approximately 17% on a dry organic matter basis and 32% of the total produced oily substances, but both in calorific value and fluidity. This was a better result than the oily substance that remained inside.

Furthermore, the separation index expressed as the ratio of residual solids to oily substances (a numerical value indicating how much residual solids is attached to oily substances per unit weight) is 0.
78, whereas it was as low as 0.09 on the separation tube side, and very good separation results were obtained, with almost no residual solid matter accompanying the light liquid on the separation tube side.

Example 2 An experiment was conducted using the same sludge and oiling conditions as in Example 1. However, after reaching 300'C, the temperature was maintained for 60 minutes while stirring. After that, stop heating and use the fan for 2
The temperature was rapidly cooled to below 50°C, heating was started again, and the temperature was controlled at 250°C. After the temperature stabilized, stirring was stopped and the contents were allowed to stand at that temperature for 120 minutes. The subsequent operations are the same as in Example 1. The experimental results are shown in Table 3.

The amount of oily substances transferred into the separation tube was approximately 15.0% on a dry organic basis and 28.6% of the total produced oily substances, which was lower than in Example 1, but the separation index was side is 0.77, while on the separation tube side it is approximately 0.77.
1, which was good. Both the calorific value and fluidity were better than the oily substance remaining in the autoclave.

Table 3 Comparative Example 1 An experiment was conducted using the same sludge and oiling conditions as in Example 1. However, after reaching 300℃, the temperature should be increased to 60℃ while stirring.
Hold for minutes. After that, stop heating and turn on the fan to 200
The temperature was rapidly cooled to below .degree. C., and heating was started again to control the temperature to 200.degree. After the temperature stabilized, the stirring was stopped and the temperature was increased to 120°C.
The contents were allowed to stand still. The subsequent operations are the same as in Example 1. The experimental results are shown in Table 4.

Table 4 The amount of oily substances that migrated into the separation tube was approximately 14.3% on a dry organic matter basis, which was 26.8% of the total produced oily substances, which did not change much compared to Examples 1 and 2. Regarding the separation index, since the separation temperature is as low as 200°C, the value on the separation tube side is 0.72, whereas the value on the autoclave side is 0.72.
25) is approaching, and the separation of oily substances and residual solids cannot be said to be very good.

Comparative example 2 The experiment was conducted using the same sludge and oiling conditions as in the example.

However, after reaching 300°C, the temperature was maintained for 60 minutes while stirring, then heating was stopped and the mixture was rapidly cooled to room temperature using a fan. After the pressure was reduced, the liquid in the autoclave was collected and allowed to stand for a day and night, separating it into a dark brown transparent aqueous phase in the upper part and a black precipitate in the lower part. On the upper surface of the aqueous phase,
No oily substance was observed, and solvent extraction with methylene chloride revealed that almost all of the oily substance was contained in the lower precipitate.

[Brief explanation of drawings]

FIG. 1 shows a flow sheet for a preferred embodiment of the invention. l... Reactor preheating section, 2... Reactor reaction section, 3
... High temperature and high pressure separation device, 4... First cooler, 5...
・First pressure reducing device, 6... Solid-liquid separation device, 7... Incinerator, 8... Waste heat boiler, 9... Second cooler, lO
...Second pressure reducing device, 11...Oil-water separation device. Figure 1 Patent applicant: Director of the Agency of Industrial Science and Technology Ken Sugiura (and one other person) Sub-agent: Patent attorney Toshiaki Ikeura 16-3 Onogawa, Tsukuba City, Ibaraki Prefecture 16-3 Onogawa, Tsukuba City, Ibaraki Prefecture National Institute of Industrial Science and Technology Pollution Resources Research Institute of Pollution Resources, Agency of Industrial Science and Technology 4-5-39 Shibasakidai, Abiko City, Chiba Prefecture

Claims (2)

[Claims] (1) In a method of thermochemically reacting water-containing organic sludge under high temperature and high pressure conditions and obtaining an oily substance from the resulting reaction product, after the reaction, the reaction product is heated to 250°C or higher under high temperature and high pressure. A method for recovering oily substances from a sludge-oiling reaction product, characterized by separating the oily substances as a light liquid by performing density difference separation in the same state. (2) The method according to claim 1, wherein gravity sedimentation is performed as the density difference separation method to separate the oily substance as a floating phase.