JPS6354969B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves supplying sludge whose moisture content has been adjusted to a high-temperature hearth made of carbon-based combustible material, burning and melting it, and directing combustion exhaust gas from above the high-temperature hearth to a post-combustion section. oxidizes CO in combustion exhaust gas to CO ₂ .

The above method reduces the volume of various types of sludge, which have been generated in extremely large quantities in recent years, to a tenth of a tenth, making it advantageous for use in landfill sites, etc., and in a safe state where no harmful heavy metals are eluted. This is an extremely useful sludge treatment method that can be treated with almost no need for petroleum-based fuels, which have recently been problematic in terms of cost and resource conservation.

However, in the conventional method described above, a burner was always used to combust in the after-combustion section in order to prevent air pollution by oxidizing 5% to 10% of CO contained in the combustion exhaust gas into _CO2 .

Therefore, the consumption of petroleum-based fuel in the auxiliary burner becomes quite large, and the operating costs become expensive.
Furthermore, there was a great risk that the combustion exhaust gas from the post-combustion section would reach an extremely high temperature, causing loss of thermal energy and damage to the refractories, leaving room for further improvement.

The purpose of the present invention is to reduce the oxidation of CO in combustion exhaust gas,
The aim is to ensure that combustion can be carried out without requiring auxiliary combustion using an auxiliary burner, and with thermal energy loss and damage to refractories suppressed as much as possible.

The characteristic means of the present invention is to reduce the water content of sludge to 40% or more by adjusting the water content of the sludge before supplying it to the high-temperature hearth.
65%, the temperature of the flue gas supplied from the high-temperature hearth to the after-combustion section is maintained at 800°C to 1100°C, and the oxidation of CO in the after-combustion section is controlled by self-combustion of CO by supplying air without an auxiliary burner. The functions and effects are as follows.

In other words, as a result of various experiments, when sludge is burnt and dissolved in a high-temperature hearth made of carbon-based combustible materials such as coke, the consumption of carbon-based combustible materials can be minimized by adjusting the moisture content of the sludge to 40% to 65%. They discovered that it is possible to maintain the temperature of the flue gas supplied from the high-temperature hearth to the after-combustion section at 800°C or higher, which is necessary for the self-combustion of CO, while reducing the temperature.

Based on this new knowledge, by simply supplying the amount of air necessary for CO oxidation to the after-combustion section,
This makes it possible to reliably oxidize CO to CO ₂ without the need for auxiliary combustion using an auxiliary burner.

In addition, the temperature of the flue gas supplied to the after-combustion section is
By keeping the temperature below 1100℃, problems such as thermal energy loss and damage to refractories due to unnecessary temperature rise can be sufficiently prevented.

As a result, the oxidation of CO in flue gas to prevent air pollution can be achieved without increasing operating costs due to post-combustion burners, and while sufficiently suppressing heat loss and damage to refractories due to flue gas. It can be done reliably and is not only effective in preventing exhaust pollution but also in terms of operating costs.
It has become possible to melt and process sludge even more advantageously in terms of maintenance costs.

Next, an example will be shown with reference to FIGS. 1 and 2.

Various types of sludge, such as sewage sludge, night soil sludge, factory wastewater treatment sludge, water treatment plant sludge, and activated sludge, which have been concentrated or dehydrated using water treatment equipment or pre-treatment equipment, are supplied to the rotary kiln type dryer 1. The moisture content is adjusted to 40% to 65%, preferably 50% to 60%, and the particle size is 2 mm.
The granulated sludge is granulated to a size of 10 mm to 10 mm, and the granular sludge is continuously or intermittently taken out from the dryer 1 and supplied to an input hopper 4 of a cupola type melting furnace 3 by a conveyor 2 as appropriate.

Then, the sludge from hopper 4 is transferred to damper 6.
A and 6b are alternately opened and closed to open and close the high-temperature hearth 5 made of carbon-based combustible material filled in the melting furnace 3.
The sludge is supplied in a mixed state or alternately with a carbon-based combustible substance, and the sludge is burned and melted in the high-temperature hearth 5, and the molten material is recovered from the take-out passage 7 connected near the bottom of the melting furnace 3. At the same time, the combustion exhaust gas from the top of the melting furnace 3 is transferred to an exhaust duct 8, a dust removal cyclone 9, and an after-combustion section 10.
released into the atmosphere through etc. In the after-combustion section 10, carbon monoxide in the high-temperature exhaust gas is caused to self-combust simply by simply supplying air into the high-temperature exhaust gas through the introduction passage 10a.

That is, as mentioned above, by reducing the water content of the sludge to 40% to 65% before supplying it to the high-temperature hearth 5, many of the problems associated with the temperature drop and rise of the combustion exhaust gas mentioned above can be reliably prevented. Through various research and experiments, we discovered that this is possible.

To explain in more detail, the ash content and calorific value of sludge vary depending on the region and time of occurrence, but the calorific value of standard sludge, that is, 50% ash and dry standard, is
2300Kcal/Kg is burned and melted in the high-temperature coke hearth 5 of a standard cupola type melting furnace 3 at an air ratio of 1.0, and the water content of the sludge supplied to the hearth 5 is varied to adjust the flue gas temperature. When we checked the changes, we obtained the results shown by the solid line in Figure 2.Also, based on actual changes in the ash content and calorific value of sludge, even if there are changes in the properties of sludge, the results shown by the solid line in Figure 2 above are Range of approximately ±100℃ (between chain lines)
They found that the combustion exhaust gas temperature was within the range of .

Based on the above new findings, we simply developed a high-temperature hearth 5
By simply adding a simple means to adjust the water content of the sludge before supplying it to the furnace, the temperature of the flue gas from the high-temperature hearth 5 can be adjusted to a suitable range that does not cause the various problems mentioned above, that is, 800°C. to about 1100℃,
They established an effective sludge melting treatment technology that can be reliably maintained.

Furthermore, if the water content of the sludge is adjusted using a rotary kiln type dryer as described above, the particle size will be 2 mm to 10 mm, which has a high drying and combustion rate and can effectively suppress dust scattering. , there is an advantage that the sludge can be granulated, but a granulation step may be added separately from the moisture adjustment step, or the granulation step may be omitted.

Further, the specific configuration of the melting furnace 3 to be used can be changed in various ways, and the carbon-based combustible material forming the high-temperature hearth 5 may be, for example, coke, coal,
Various materials such as graphite electrode scraps can be used.

[Brief explanation of drawings]

The drawings show an embodiment of the sludge melting method according to the present invention, and FIG. 1 is a schematic explanatory diagram of the apparatus used, and FIG.
The figure is a graph showing the correlation between sludge moisture and combustion exhaust gas temperature. 5...High-temperature hearth, 10...After-combustion section.

Claims (1)

[Scope of Claims] 1. Water-adjusted sludge is supplied to a high-temperature hearth 5 made of a carbon-based combustible material, where it is burned and melted, and the combustion exhaust gas from above the high-temperature hearth 5 is sent to the after-combustion section 1.
A method for melting sludge in which CO in combustion exhaust gas is oxidized to CO ₂ by supplying CO 2 to CO 2 , the method comprising adjusting the water content of the sludge to make the water content of the sludge 40% to 65%,
The temperature of the combustion exhaust gas supplied to the after-combustion section 10 is
The temperature is maintained at 800°C to 1100°C, and the after-burning section 10
A sludge melting method in which CO oxidation is carried out by self-combustion of CO by supplying air without an auxiliary burner. 2 Adjust the water content of the sludge to reduce the water content to 50% or
60% method according to claim 1.