JPH02261597A - Method for continuously converting sludge into oil - Google Patents

Abstract

PURPOSE:To increase the rate of recovery and to prevent the lowering of the efficiency of heat transmission and the occurrence of trouble such as blocking by moving a reaction product of org. sludge to the top of a reaction tower at a specified linear velocity of rising. CONSTITUTION:When raw material to be treated is continuously fed into a vertical reaction tower 2 from the bottom and brought into a reaction in the tower 2 and the resulting reaction product is drawn out of the top, the linear velocity of rising of the reaction product is kept at >=0.4mm/sec and the precipitation of solid matter is prevented. Dehydrated sludge in the tower 2 is heated, subjected to reactive treatment and converted into oily matter. The rate of conversion into the oily matter is very high. Since no solid matter precipitates in the tower 2, a high rate of recovery can be maintained and the lowering in the efficiency of heat transmission and the occurrence of trouble such as blocking can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for thermochemically reacting organic sludge such as surplus sludge generated from organic wastewater biological treatment equipment under high temperature and high pressure conditions. This paper relates to a method for continuously converting sludge into oil.

[Prior art]

Sewage sludge, a typical type of organic sludge, is produced at a rate of approximately 5% per year nationwide.
It is a huge amount of 0 million bottles (moisture content 98%) and is increasing year by year. Conventionally, around 80% of the processing of sewage sludge is done after dewatering.

However, in this case, there is the problem of securing a landfill site, and with the development of urbanization, it is becoming more difficult to secure a landfill site 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 in terms of volume reduction. However, this method has the problem that it requires a large amount of thermal energy to evaporate water in the sewage sludge, resulting in high running costs and being uneconomical. In response to this current situation, the present inventors have proposed a method for liquefying sewage sludge, for example, in Japanese Patent Application Laid-open No. 136299/1983. This method involves reacting organic matter in sewage sludge under alkaline conditions at an elevated reaction temperature under pressure higher than the saturated water vapor pressure at the reaction temperature, and then cooling the resulting reaction product. It is.

The reaction product obtained by this method has good separability between the aqueous phase and the solid phase, and the solids tend to precipitate. According to the research of the present inventors, when the raw material to be treated is continuously supplied from the lower part of a vertical reaction tower, reacted within the reaction tower, and one reaction product is taken out from the upper part. ,
It has been found that solids in the reaction product with a high sedimentation rate precipitate inside the reaction tower, which not only reduces the recovery rate, but also causes problems such as a decrease in heat transfer efficiency and an increase in pressure due to blockage. did.

[Problem to be solved by the invention]

An object of the present invention is to solve the above-mentioned problems encountered in conventional treatment of organic sludge such as sewage sludge.

[Means to solve the problem]

According to the present invention, while organic sludge is continuously supplied from the lower part of the vertical reaction tower and moved from the lower part to the upper part of the reaction tower, the inside of the reaction tower is maintained at high temperature and high pressure. In a continuous sludge oil conversion method in which organic sludge is changed into an oily substance and the oily substance is taken out from the upper part of a reaction tower, the organic sludge reaction product is
Provided is a continuous method for converting sludge into oil, characterized in that the sludge is moved upward through the reaction tower at an upward linear flow rate of c or more.

The organic sludge used as the raw material to be treated in the present invention 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.

To carry out the method of the invention, organic sludge is maintained at high temperature and pressure. In this case, if the organic sludge contains too much water, it will consume a large amount of thermal energy to reach the temperature required for the thermochemical reaction, so it is necessary to dehydrate the organic sludge to a water content of 85% or less. In addition, it is possible to subject the organic sludge to alkaline conditions in order to accelerate thermochemical reactions if necessary, but this is not essential. An alkaline substance is used, and examples of the alkaline substance include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and sodium formate.

Examples include alkali metal compounds such as potassium formate, and alkaline earth metal compounds such as calcium oxide, 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 to 350°C, preferably 300 to 320°C, and the reaction pressure is 1.

More than the saturated water vapor pressure at the reaction humidity, for example, 25
At 0℃, 40kg/cd or more, at 300℃, 9
It is sufficient if it is 0 kg/d or more. At this time, the holding time for one reaction temperature 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 aqueous phase, the temperature should be as high as possible. It is desirable to react for a long time, however, raising the reaction temperature or
Since increasing the holding time increases the initial cost, the reaction temperature should be 300°C or less and the holding time should be 6.
0 minutes or less is appropriate.

In the present invention, self-generated pressure due to water vapor from sewage sludge can be used as the pressure.

If necessary, for example, nitrogen gas, carbon dioxide gas, argon gas, etc. can be used for pressurization.

In the reaction according to the present invention, the reaction product exhibits good separability between the aqueous phase and the solid phase, making it easier for the solids to precipitate.

The raw material to be treated is continuously supplied from the lower part of the vertical reaction tower and reacted within the reaction tower.

When the reaction product is taken out from the upper part, under the condition that the upward linear flow velocity of the reaction product in the reaction column is small, 1
There is a problem in that solids in the reaction product that have a high sedimentation rate precipitate inside the reaction column.

In order to deal with this problem, the present invention aims at continuously supplying the raw material to be treated from the lower part of a vertical reaction tower, allowing it to react in the reaction tower, and then taking out the reaction product from the upper part for one reaction. Maintaining the upward linear flow rate of the product at 0.4 mm/ssc or higher,
Prevents precipitation of solids. Regarding the set value of the ascending linear flow velocity, as shown in the reference example below, in experiments conducted at 0.3 m/sec or less, all solids could not be recovered, and as shown in the example, the set value was 0.4 rntm/sec. In the experiment conducted at sec, all the solids were recovered, so 0.4
A value of mm/sec or more is appropriate.

The upward linear flow rate of the reaction product can be adjusted by adjusting the amount of raw material to be treated that is fed under pressure into one reaction column. Furthermore, in actual equipment design, the upward linear flow velocity of the reaction product is 0.4 mm/sec depending on the processing amount of the raw material to be treated.
The cross-sectional area inside the reaction tower can be set so as to be as above.

〔Effect of the invention〕

According to the present invention, organic sludge, which has conventionally been treated as industrial waste, can be converted into an oily substance useful as liquid fuel. In this case, the conversion rate to oily substances is very high at approximately 40 to 50% on a dry organic matter basis.Moreover, since precipitation of solids does not occur in the reaction tower, not only can a high recovery rate be maintained, but also a high recovery rate can be maintained. It is also possible to prevent problems such as a decrease in heat transfer efficiency and blockage. Therefore, the present invention is an economical and safe method for treating organic sludge.

〔Example〕

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

Reference Example 1 Sewage sludge was selected as the organic sludge, and dehydrated sludge A of mixed raw sludge discharged from a treatment plant using the standard activated sludge method was used in the experiment. This sludge was dehydrated using a belt press after adding a polymer flocculant, and its typical properties were a water content of 80.0% and an organic matter ratio of 81.8%. The flow sheet of the sludge continuous oil conversion experimental device is shown in Fig. 1. In Fig. 1, 1 is the sludge injection device, 2 is the reaction device,
3 is a cooling device, 4 is a pressure reducing device, and 5 is an electric boiler. After filling the sludge injection device 1 with the dehydrated sludge, the sludge injection device 1 was used to pressurize the sludge into the reaction device 2 via the line 6 at a pressure of 120 kg/cd.The reaction device 2 is a heat exchange type reaction device. The heat medium heated by the electric boiler is introduced from line 7 and discharged from line 8 to return to the electric boiler, while the dehydrated sludge in the reactor 2 is
It was heated to 0°C and underwent one reaction process, converting it into an oil. At that time, the upward linear flow rate of the reaction product in the reaction device 2 is adjusted to 0 by adjusting the amount of dehydrated sludge A supplied to the reaction table W2.
．． 2+am/sec. The reaction product taken out through line 9 is cooled to below 100°C in cooling device 3, and further introduced into pressure reducing device 4 through line 10, where the reaction gas is separated. The pressure was then reduced to atmospheric pressure. After depressurization, the reaction product was removed via line 12 and separated into three phases: an oil, a residual solid, and an aqueous phase by extraction with dichloromethane.

In addition, as a control experiment, a batch experiment using an autoclave was conducted. Specifically, the dehydrated sludge A was filled into an autoclave (capacity: 300 ml).

It was heated to 300°C in an electric furnace and held at that temperature for 60 minutes. At that time, the pressure was set to 120 kg with nitrogen gas in advance.
The pressure was increased to 120 kg/cd using a pressure regulating valve to control the pressure increase due to temperature rise to 120 kg/cd.

After maintaining the temperature, it was rapidly cooled to around room temperature using a blower, and the reaction gas and products were collected. The obtained product was separated into three phases: an oily substance, a residual solid substance, and an aqueous phase by an extraction method using dichloromethane.

Table 1 shows the organic matter recovery rate for each phase of the product in each experiment, and Table 2 shows the inorganic matter recovery rate.

From Table 1, there is a difference in the recovery rate between continuous experiments and batch experiments, and especially for residual solids, the recovery rate in continuous experiments (
3.2%) was about 173 for batch experiments (9.9%). Additionally, from Table 2, almost 100% of inorganic substances were recovered in the batch experiment, and most of them were recovered as residual solids, whereas in the continuous experiment, the total recovery rate of inorganic substances was 46.6%. . It was speculated that this was caused by solid matter (mainly residual solid matter) having a high sedimentation rate settling in the apparatus.

Table-I Organic matter recovery rate Table-2 Inorganic matter recovery rate Reference example 2 Dehydrated sludge B was collected from the same sewage treatment plant as in Reference example 1.
Used for experiments. Typical properties of this dehydrated sludge B were a water content of 78.1% and an organic matter ratio of 72.2%.

The experimental method was almost the same as in Reference Example 1.

However, in the continuous experiment, the upward linear flow velocity of the reaction product in the reactor 2 was set to 0.3 m+m/sec by adjusting the amount of dehydrated sludge B supplied to the reactor 2. Further, in the batch experiment, the holding time was set to 30 minutes.

Table 3 shows the organic matter recovery rate of each phase of the product for each experiment, and Table 4 shows the inorganic matter recovery rate.

From Tables 3 and 4, although the recovery rate of residual solids in continuous experiments improved, it was still low, and it was assumed that precipitation of solids still occurred within the apparatus.

Table-3 Organic matter recovery rate Table-4 Inorganic matter recovery rate Example 1 Dehydrated sludge C was collected from the same sewage treatment plant as in Reference Example 1.
Used for experiments. Typical properties of this dehydrated sludge C were a water content of 80.3% and an organic matter ratio of 79.5%.

The experimental method was almost the same as in Reference Example 1.

However, the upward linear flow rate of the reaction product in the reactor 2 is
0.4 m by adjusting the amount of dehydrated sludge C supplied to the reaction device 2.
m/sec. Further, in the batch experiment, the holding time was set to 0 minutes.

Table 5 shows the organic matter recovery rate for each phase of the product for each experiment, and Table 6 shows the inorganic matter recovery rate.

From Table 5, in the continuous experiment, almost the same organic matter recovery rate as in the batch experiment was obtained, and at this time, the recovery rate of organic matter was 5% on a dry organic matter basis.
1.6% oil was recovered. Also.

From Table 6, the total recovery rate of inorganic substances in continuous experiments is 116.
3%, and the total recovery of inorganics for the batch experiment was 114.
Inorganics as high as 5% were recovered. Therefore, it was determined that the continuous sludge conversion equipment could be operated without precipitating solid matter within the equipment.

Table-5 Organic matter recovery rate Table-6 Inorganic recovery rate

[Brief explanation of drawings]

Figure 1 shows the flow sheet of the sludge continuous oil conversion experimental equipment. 1... Sludge injection device, 2... Reaction device, 3... Cooling device. 4...Pressure reducing device, 5...Electric boiler Sub-agent Patent attorney Toshiaki Ikeura

Claims (1)

[Claims] (1) While organic sludge is continuously supplied from the lower part of the vertical reaction tower and moved from the lower part to the upper part of the reaction tower,
In a continuous method for turning sludge into oil, the organic sludge is changed into an oily substance by maintaining the inside of the reaction tower at high temperature and pressure, and the oily substance is taken out from the upper part of the reaction tower,
A method for continuously converting sludge into oil, characterized in that the organic sludge reaction product is moved above the reaction tower at an upward linear flow rate of 0.4 mm/sec or more.