JPS60179491A - Conversion of organic sludge to energy - Google Patents

Abstract

PURPOSE:To utilize ash as catalyst for thermal cracking and produce oil with good yield, by adding ash of burned char and performing thermal cracking at a relatively low temp. CONSTITUTION:Dehydrated organic sludge is sent from a dehydrated sludge storage tank 11 into a drier 12 for thorough drying and is led into a thermal cracking oven 13 kept at about 150-450 deg.C for thermal cracking to produce a small amt. of incombustible gas and large amts. of oil and char. The incombustible gas is passed through a waste gas disposal process 14, the oil is stored in an oil storage tank 15 for recovery of energy and the char is burned in an incinerator 16 for utilization as heat source for the drier 12 and the thermal cracking oven 13. Produced ash is sent to an ash storage tank 17 and a part of it is mixed with dehydrated sludge and is sent to the drier 12 together with sludge. Metal oxides and inorg. salts condensed in the ash act effectively as catalyst for thermal cracking reaction, leading to an increased oil recovery rate.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to biological treatment sludge discharged from sewage treatment plants, human waste treatment plants, industrial wastewater treatment plants, etc., or organic sludge such as livestock waste. It concerns methods of converting matter into energy.

[Technical background of the invention]

Conventionally, in order to recover energy from organic sludge-like substances such as surplus activity and sludge (hereinafter referred to as sludge) generated in sewage treatment plants, dehydrated sludge is stored in a dehydrated sludge storage tank as shown in Figure 1. After being sent from (1) to a dryer (2) and sufficiently dried, it is introduced into a pyrolysis furnace (3) whose reaction temperature is adjusted to about 600-1000℃, where it is thermally decomposed to produce flammable gas and a small amount of oil. The flammable gas is stored in a gas storage tank (4) and recovered as energy, and the oil and char are used as a heat source for the dryer (2) and pyrolysis furnace (3). In order to do so, it is introduced into an incinerator (5) and burned.

"Concession of Background Art" In the case of this conventional method, since the form of energy recovery is flammable gas, there was a problem in that it was difficult to handle in terms of storage, capacity, safety, etc.

[Purpose of the invention]

The present invention was made in view of the above-mentioned points, and aims to facilitate the handling of energy recovered from sludge as oil, and to recover energy in a form with high added value. .

[Summary of the invention]

Therefore, the inventors attempted to improve the thermal decomposition method of sludge for the purpose of converting it into oil, and found that when the thermal decomposition temperature was set to a relatively low temperature range, a small amount of nonflammable gas and a large amount of nonflammable gas were extracted from the sludge. It was found that oil and char (residual decomposition) were generated, and that metal oxides and char were found in the char incineration ash.
Focusing on the fact that inorganic salts are concentrated,
The method of converting organic sludge-like material into energy according to the present invention comprises converting organic sludge-like material into energy from 150 to 450
It is thermally decomposed at a relatively low temperature of ℃, and the incinerated ash of the char (residual decomposition) after thermal decomposition is added to the organic sludge-like material to be thermally decomposed to remove the metal oxides and inorganic salts contained in the ash. It is characterized by the fact that it uses oil as a catalyst to produce a large amount of oil with high efficiency.

[Embodiments of the invention]

The method of the present invention will be explained in detail based on embodiments shown in the drawings.

As shown in Figure 2, the dehydrated sludge is transferred to the dehydrated sludge storage tank 0.
After being sent to the dryer θ and sufficiently dried, it is introduced into a pyrolysis furnace (to) whose reaction temperature is adjusted to about 150 to 450℃ and is thermally decomposed, resulting in a small amount of nonflammable gas and a large amount of oil and oil. Char (decomposition residue) is generated.

Then, the nonflammable gas is sent to the waste gas treatment process α◆, the oil is stored in the oil storage tank αυ and recovered as energy, and the char is sent to the incinerator to be used as a heat source for dryer 0 and pyrolysis furnace 01. The incinerated ash is sent to the ash storage tank αη.
+7) is sent to the dehydrated sludge, mixed, and sent together with the sludge to the dryer a■.

Next, regarding the thermal decomposition temperature of sludge, which is one element of the present invention, the results of a comparative example in which surplus activated sludge generated at a sewage treatment plant was subjected to thermal decomposition treatment at a temperature of 350 ° C. Shown in the table.

From this result, pyrolysis at a relatively low temperature results in an oil yield 3 times higher than that of conventional heat treatment at a relatively high temperature.

■Gas yield is less than half, and it is nonflammable.

I understand that. This will increase the thermal decomposition temperature of sludge to that of the present invention. , which clearly shows that oil is preferentially obtained.

Furthermore, regarding the temperature effect of heat treatment in the low temperature range of 150 to 450 °C specified in the present invention, we investigated the batch method (batch tests).
) This will be explained using the results of a thermal decomposition experiment using K.

Figure 3 shows the relationship between the temperature and the amount of oil produced when the reaction was carried out at various thermal decomposition temperatures.
The broken line shows the relationship between the reaction temperature and the amount of oil produced.
The solid line shows the differential type.

The broken line in Figure 3 is centered at 300°C,
It is clearly shown that the amount of oil produced is large in the temperature range of 50°C.

Next, regarding the addition of char incineration ash, which is another element of the present invention, using food wastewater treatment sludge as a sample, according to the process shown in Figure 2, ash was added to the dry sludge at a weight ratio of 5%. Table 2 shows the test results of experimental examples in which ash was added, 10%, and 20f, and comparative examples in which ash was not added.

The values in Table 2* (Char amount/Dried sludge amount) do not include added ash.

This result shows that when a certain amount or more of ash is added, the oil yield increases.

This is because the addition of ash increases the concentration of metal oxides and inorganic salts such as Na in Ca, A/, and Fe+, which act extremely effectively as catalysts.

It shall be determined as appropriate depending on various conditions such as the amount of ash added and the properties of sludge.

Further, although the basic steps of the present invention are shown in FIG. 2, this step can be varied in various ways, and other steps may be added, such as a combination of heat recovery processes,
Alternatively, dehydrated sludge to which ash has been added can be formed into predetermined granules to speed up the transfer of heat during pyrolysis, shortening the pyrolysis reaction time and increasing the efficiency of oil production. In addition, it is possible to prevent impurities from sludge powder from being mixed in, and to shorten the pyrolysis reaction time by adding a predetermined amount of oil produced by pyrolysis to the dried sludge and using the oil as a heat transfer medium. In addition, the sludge to be applied is also
Not only sewage treatment sludge and food wastewater treatment sludge, but also biological treatment sludge from human waste treatment plants, industrial wastewater treatment plants, etc., or livestock waste.

There is no particular limitation as long as it is an organic sludge-like substance.

〔Effect of the invention〕

As described above, according to the present invention, organic sludge-like substances are thermally decomposed at a relatively low temperature range of 150 to 450°C, so that energy can be easily handled and the organic sludge is converted into oil in the form of high value-added oil. Furthermore, since the processing temperature is low, it can be inexpensively packaged, and the incineration ash of the char (decomposition residue) after thermal decomposition can be added to the organic sludge-like material to be thermally decomposed. So the concentrated metals in the ash can act and increase the oil recovery rate.

[Brief explanation of drawings]

Fig. 1 is a process diagram showing the conventional method, Fig. 2 is a process diagram showing the method of the present invention, and Fig. 3 is a diagram showing the relationship between pyrolysis temperature and oil generation wind.

Claims (1)

[Claims] (1) Organic sludge-like material is thermally decomposed at a temperature of 150 to 450°C to produce oil, and incineration ash of char (decomposition residue) is added to the organic sludge-like material to be thermally decomposed. A method for converting sludge-like materials into energy.