JP4787966B2 - Method for dry treatment of nitrogen-containing waste and apparatus therefor - Google Patents

Description

  The present invention relates to a dry treatment method for nitrogen-containing waste such as livestock waste and sewage sludge and an apparatus therefor.

  Most of the current processing of livestock waste is compost, but the overproduction and application of compost results in pollution of rivers and groundwater and eutrophication of the sea area, and also causes bad odor problems.

Under such circumstances, utilization and treatment methods other than compost of livestock waste are desired. For example, as a treatment method of slurry livestock excrement, there is a technology for generating energy by generating methane by fermentation. Are known. On the other hand, since compost has a low water content, there is an expectation for a method using pyrolysis and gasification (see Patent Document 1 and the like) as a treatment method for obtaining clean energy.
JP 2005-013964 A

However, when examining the treatment by pyrolysis and gasification of compost, there is a problem that the nitrogen content of the compost is high, and harmful nitrogen compounds such as NH ₃ and HCN are generated when pyrolysis and gasification. Table 1 shows elemental analysis values of various wastes, biomass, and coal.

As shown in Table 1, it can be seen that the nitrogen content is particularly high in livestock waste such as compost. In addition, sewage sludge is one of wastes with high nitrogen content. For example, when a nitrogen-containing fuel is pyrolyzed, a part of the nitrogen content is sooted from tar, but most of the rest is directly or as a decomposed product from tar or char, NH ₃ , HCN, N A gas component such as ₂ is generated. Of these, NH ₃ is a malodorous substance and HCN is extremely toxic, NH ₃ is subject to regulation by the Malodor Control Law, and HCN requires very low emission standards as water quality environmental standards and other legal regulations . For this reason, it is necessary to remove these using a scrubber or the like. However, when a scrubber is used, a waste disposal problem occurs.

  The present invention eliminates such conventional problems, and decomposes volatile nitrogen compounds into nitrogen gas at as low a temperature as possible to efficiently detoxify the nitrogen-containing waste, and an apparatus therefor It is an issue to provide.

  The present invention is characterized by the following in order to solve the above problems.

<1> Ni for containing nitrogen-containing waste containing 2% by mass or more of at least one kind of nitrogen selected from compost and sewage sludge upstream, and contacting gas components generated by thermal decomposition of nitrogen-containing waste A reactor in which a catalyst layer made of at least one catalyst selected from supported carbon, Ni-supported alumina, and limonite is disposed downstream; a sample heating device for heating nitrogen-containing waste to a pyrolysis temperature; and a catalyst Of nitrogen-containing waste comprising a catalyst layer heating device for heating the layer, and a water vapor supply device for supplying water vapor into the reactor from a water vapor supply port provided between the nitrogen-containing waste and the catalyst layer Using a dry treatment apparatus, the nitrogen-containing waste disposed in the reactor is pyrolyzed, and the gas component generated by the pyrolysis has a temperature of 550 to 550 in the presence of steam supplied from the steam supply port into the reactor. 7 Dry processing method of a nitrogen-containing waste comprising contacting the catalyst layer is in the range of 0 ° C..

<2> A dry treatment apparatus for dry treatment of nitrogen-containing waste containing 2% by mass or more of at least one kind of nitrogen selected from compost and sewage sludge, the nitrogen-containing waste being disposed upstream, A reactor in which a catalyst layer made of at least one catalyst selected from Ni-supporting carbon, Ni-supporting alumina, and limonite for contacting a gas component generated by thermal decomposition of nitrogen waste is disposed downstream; A sample heating device for heating the waste to the pyrolysis temperature, a catalyst layer heating device for heating the catalyst layer, and a steam supply port provided between the nitrogen-containing waste and the catalyst layer in the reactor. A dry treatment apparatus for nitrogen-containing waste, comprising: a water vapor supply device for supplying water vapor to the water.

According to the present invention as described above, since the gas component generated by the thermal decomposition of the nitrogen-containing waste is brought into contact with a specific catalyst for reforming, in a condition where the thermal decomposition temperature is relatively low, A catalyst can decompose a volatile nitrogen compound to nitrogen gas, and can make the gas harmless efficiently. That is, the reformed gas treated with the catalyst is detoxified by decomposing HCN into N ₂ , the nitrogen-containing liquid product is also decomposed into N ₂ , and further, NH ₃ is decomposed into N ₂ , so that bad odor is also generated Is prevented.

  The present invention has the features as described above, and an embodiment thereof will be described below.

  In the present invention, specific examples of the nitrogen-containing waste to be dry-treated include those having a relatively high nitrogen content and a relatively low moisture content, such as compost and sewage sludge. The compost is not particularly limited as long as it is obtained by fermenting pig dung compost, chicken dung compost, and other livestock dung, etc., but those containing a relatively large amount of nitrogen, for example, containing 2% by mass or more. Is preferred.

  In the present invention, the nitrogen-containing waste is heated and pyrolyzed, and the gas component generated by the pyrolysis is brought into contact with at least one catalyst selected from Ni-supporting carbon, Ni-supporting alumina, and limonite. Although the thermal decomposition temperature of a nitrogen-containing waste is based also on the kind, it is the range of 300-900 degreeC, for example.

  As the Ni-supporting charcoal of the catalyst, for example, those obtained by a method of impregnating low-grade coal particles having ion exchange ability with an aqueous nickel salt solution can be used. Especially, it is preferable to use Ni carrying | support lignite which has Ni / C (mass ratio) in the range of 0.1-1 and a particle size in the range of 0.5-10 mm.

As the Ni-supported alumina for the catalyst, those obtained by impregnating a porous alumina carrier such as γ-alumina with a nickel salt aqueous solution can be used. Among them, there Ni / _Al 2 _{O 3} (mass ratio) is within the range of 0.1 to 0.5, it is preferable to use a particle size in the range of 0.5 to 10 mm.

  Limonite as a catalyst is a loess in which water containing a lot of iron such as swamps and shallow seas is precipitated by exposure to the air. Thing, aged thing, etc. can be used.

The nitrogen-containing gas produced by thermal decomposition of nitrogenous wastes, other N _2, NH 3, _HCN, but are like tar-N, by contacting it with the catalyst, mostly N ₂ Is converted to The temperature of the catalyst at the time of contact with the gas component produced by pyrolysis is, for example, 500 to 900 ° C, preferably 550 ° C to 750 ° C, more preferably 650 ° C to 700 ° C. If the temperature of the catalyst is too high, the operating efficiency for the dry process is reduced. If the temperature of the catalyst is too low, volatile nitrogen compounds such as NH ₃ and HCN cannot be sufficiently converted to N ₂ .

When the gas component generated by thermal decomposition of the nitrogen-containing waste is brought into contact with the catalyst, this may be performed in the presence of water vapor. Thus, the water vapor acts as a gasifying agent, increase the conversion rate to N _2, it is possible to reduce the proportion of nitrogen-containing compounds other than N _2. The amount of water vapor supplied to the catalyst is preferably 0 to 30 kPa at 25 ° C.

  FIG. 1 is a diagram schematically showing a dry treatment apparatus for nitrogen-containing waste in one embodiment of the present invention. In the same figure, the code | symbol 1 has shown the dry processing apparatus of this embodiment as a whole. The dry processing apparatus 1 includes a reactor 2, and a nitrogen-containing waste sample 20 and a catalyst layer 30 are arranged in two upper and lower stages in a reaction chamber 3 in the reactor 2. .

  The sample 20 is arranged in the upper sample arrangement portion 4 in the reaction chamber 3, and the catalyst such as the Ni-supporting charcoal is arranged as a catalyst layer 30 in the lower catalyst layer arrangement portion 5 in the reaction chamber 3.

  A sample heating device 10 for heating and thermally decomposing the sample 20 is provided on the outer peripheral portion of the reactor 2 at the height position of the sample placement unit 4. A catalyst layer heating device 11 for heating the catalyst layer 30 is provided on the outer peripheral portion of the reactor 2 at the height position of the catalyst layer arrangement portion 5.

Furthermore, the dry processing apparatus 1 includes an inert gas supply device 12 that supplies an inert gas such as Ar and N ₂ as a carrier gas into the reaction chamber 3 from an inert gas supply port 6 upstream of the sample 20; In the reaction chamber 3, a water vapor supply device 13 that supplies water vapor from the water vapor supply port 7 located between the sample 20 and the catalyst layer 30 is provided.

  Downstream of the catalyst layer 30 in the reactor 2, a gas outlet 8 through which the gas component generated by thermal decomposition of the sample 20 passes through the catalyst layer 30 and the reformed gas component is discharged out of the reactor 2. Is provided. A purification / analysis device 14 for purifying and analyzing the reformed gas component discharged from the gas discharge port 8 is installed downstream of the gas discharge port 8 if necessary.

By the dry processing apparatus 1 of the present embodiment having the above-described configuration, the reformed gas of the nitrogen-containing waste sample 20 is performed as follows. First, a catalyst for gas reforming such as Ni-supporting charcoal is fixed to the catalyst layer arranging portion 5 in the reactor 2 in a layered manner to form a catalyst layer 30. The catalyst layer 30 is laid without a gap so that all the pyrolysis gas components of the sample 20 pass through the catalyst layer 30, and the thickness and density of the catalyst layer 30 are such as HCN and NH ₃ generated by the pyrolysis of the sample 20. While being sufficiently reformed to N ₂ , it is determined appropriately in consideration of not excessively preventing the gas component from passing through the catalyst layer 30.

  Then, the nitrogen-containing waste sample 20 is placed in the sample placement portion 4 provided upstream of the catalyst layer 30 in the reactor 2.

  After the sample 20 is arranged in the upper stage in the reactor 2 and the catalyst layer 30 is fixed in the lower stage in this way, the reactor is passed from the inert gas supply port 6 upstream of the sample 20 by the inert gas supply device 12. An inert gas is supplied into 2 and circulated to the gas discharge port 8 to create an inert gas atmosphere in the reaction chamber 3.

  And the catalyst layer 30 is heated to required temperature with the catalyst layer heating apparatus 11 installed in the outer peripheral part of the reactor 2. FIG. Next, the sample 20 is heated to a required temperature by the sample heating device 10 to start thermal decomposition of the sample 20.

The gasification component produced by the thermal decomposition of the sample 20 flows to the downstream catalyst layer 30 together with the carrier gas supplied from the upstream. Then, the gas component that has reached the catalyst layer 30, by contacting the catalyst layer 30 which is heated to a predetermined temperature, HCN, harmful components such as NH ₃ is modified to reduce gas.

  If necessary, the steam supply device 13 further supplies heated steam into the reaction chamber 3 from the steam supply port 7 provided between the sample 20 and the catalyst layer 30, and the sample 20 is present in the presence of steam. May be brought into contact with the catalyst layer 30.

The reformed gas component that has been reformed in contact with the catalyst layer 30 and then passed downstream through the catalyst layer 30 is discharged out of the reactor 2 through the gas outlet 8 of the reactor 2. If necessary, a purifying / analyzing device 14 is installed downstream of the gas outlet 8 to further refine the reformed gas component by adsorption, filtration, separation, etc., HCN, NH ₃ in the reformed gas component, etc. You may make it monitor the harmful component of.

After the nitrogen-containing waste sample 20 is converted into a clean gas component in this way, this gas component may be reused as an energy source or the like, or may be released into the atmosphere. For example, since HCN, NH _{3 and the} like in the pyrolysis gas component are decomposed by the catalyst layer 30 to generate hydrogen, it is also possible to recover hydrogen from the reformed gas component.

  In the above, the material of the reactor 2 is not particularly limited as long as it has heat resistance at the thermal decomposition temperature of the sample 20 or the temperature of the catalyst layer 30, but quartz, a metal material having a melting point exceeding 1000 ° C., or the like. Is considered. The scale of the reactor 2 is appropriately determined according to the purpose. The sample placement unit 4 and the catalyst layer placement unit 5 may have any structure as long as they can fix the sample 20 and the catalyst layer 30 and do not hinder the flow of the gas component. As the material for the sample placement portion 4 and the catalyst layer placement portion 5 and the inner surface of the reactor 2, those that can easily remove the solid carbon component remaining after the treatment are used.

  Therefore, an example will be shown below and will be described in more detail. Of course, the invention is not limited by the following examples.

<Examples 1-3, Comparative Example 1>
As a sample, about 1 g of pig dung compost dried at a temperature of 107 ° C. for 1 hour was used. Table 2 shows the analytical values of the samples.

  Using the two-stage fixed-bed two-stage reactor 52 shown in FIG. 2, the sample was catalytically decomposed using Ni-supported charcoal as a catalyst. Ni-supporting charcoal (brown coal: about 7 g, particle size: 0.5-1.0 mm, Ni content: 10 wt%) was fixed to the catalyst layer arrangement portion 55 in the reaction chamber 53 and fixed as a catalyst layer 30 having a layer thickness of 2 cm.

Then, about 1 g of swine manure compost was placed as the sample 20 in the sample placement portion 54 provided upstream of the catalyst layer 30 in the reaction chamber 53. Thereafter, 70 kPa of Ar or N ₂ was supplied from the inert gas supply port 56 upstream of the sample 20 into the reaction chamber 53 and circulated to the gas discharge port 58, thereby forming an inert gas atmosphere in the reaction chamber 53.

  And the catalyst layer 30 was heated at 650 degreeC with the electric furnace 61 installed in the outer peripheral part of the fixed bed two-stage reactor 52 in the height position of the catalyst layer 30. FIG. Next, the temperature of the sample 20 was increased from room temperature to 900 ° C. at a rate of 10 ° C./min by an electric furnace 60 installed on the outer periphery of the fixed bed two-stage reactor 52 at the height position of the sample 20. Thereby, thermal decomposition of the sample 20 was performed. In addition, the temperature of the sample 20 and the catalyst layer 30 was measured with the thermocouple.

  The gas component generated by thermal decomposition of the sample 20 was circulated to the downstream catalyst layer 30 together with the carrier gas supplied from the upstream side, and the gas component was brought into contact with the catalyst layer 30.

Then, the gas component which has passed through the catalyst layer 30 to the downstream together with discharged from the gas discharge port 58, which is then introduced into the trap 72 in an ice bath 71 for recovering NH ₃ and HCN with deionized water, downstream thereof N ₂ was recovered in a certain gas bag 73. NH ₃ and HCN collected in the trap 72 were analyzed by ion chromatography, and N ₂ collected in the gas bag 73 was analyzed by gas chromatography (TCD). Further, nitrogen in the char remaining in the reaction chamber 53 after pyrolysis was quantified by elemental analysis.

Further, as a catalyst, Ni / Al ₂ O ₃ (Example 2: a commercially available product previously reduced by hydrogen, about 5 g, particle size 0.5-1.0 mm, Ni content 20 wt%, layer thickness 2 cm of catalyst layer 30), Limonite (Example 3: about 7 g, particle size 0.5 to 1.0 mm (though pelletized and then pulverized) catalyst layer 30 layer thickness 2 cm), river sand (Comparative Example 1: about 10 g catalyst layer 30 layer) Sample 20 was dry-treated under the same conditions as in Example 1 except that 2 cm in thickness was used.

The analysis result of the nitrogen distribution of the recovered material in Examples 1 to 3 and Comparative Example 1 is shown in FIG. In Example 1 using Ni on charcoal as catalyst, most of the volatile nitrogen-containing component modified in N _2. NH ₃ was hardly detected, and HCN was below the lower limit of detection.

Similarly in Example 2 using Ni / Al ₂ O ₃ as a catalyst, most of the volatile nitrogen-containing component was reformed to N ₂ . NH ₃ was hardly detected, and HCN was below the lower limit of detection.

Limonite Example 3 similarly using as the catalyst, most of the volatile nitrogen-containing component modified in N _2. NH ₃ was hardly detected, and HCN was below the lower limit of detection. Some other nitrogen-containing volatile components were produced, but this is because tar does not exist due to the carbon balance and is unlikely to be combined with Fe in the catalyst (Naoto Tsubouchi, Catalysis Letters Vol. 105, Nos. 3-4, December 2005), presumed to be either or both of N in soot and other gaseous nitrogen compounds.

In Comparative Example 1 using river sand, there was little conversion to N ₂ , much NH ₃ was detected, and HCN was also detected. Many other nitrogen compounds were also detected.
<Example 4>
The sample was dry-treated under the same conditions as in Example 2 (Catalyst: Ni / Al ₂ O ₃ ) except that the temperature of the catalyst layer was 550 ° C. FIG. 4 shows the analysis result of the nitrogen distribution of the recovered material.

As shown in FIG. 4, compared with Example 2 in which the temperature of the catalyst layer 30 was 650 ° C., the ratio of N ₂ was slightly reduced in Example 4, but almost no NH ₃ and HCN were detected. .
<Example 5>
The sample was dry-treated under the same conditions as in Example 2 (catalyst: Ni / Al ₂ O ₃ ), and further, between the sample 20 and the catalyst layer 30 from the water vapor supply port 57 using the microfeeder 70. Further, 30 kPa of water vapor was supplied into the reaction chamber 53, and the gas component generated by thermal decomposition of the sample 20 was brought into contact with the catalyst layer 30 in the presence of water vapor. The analysis result of the nitrogen distribution of the recovered material is shown in FIG.

As shown in FIG. 5, in Example 5 to which water vapor was added, the conversion rate to N ₂ further increased compared to Example 2, and almost all of the volatile nitrogen compounds were converted to N ₂ . Also, NH ₃ and HCN were hardly detected.

It is the figure which showed schematically the dry processing apparatus of the nitrogen-containing waste in one Embodiment of this invention. It is the figure which showed the outline of the apparatus used for the test of an Example and a comparative example. It is a graph which shows the analysis result of the nitrogen distribution of the recovered material after the dry processing of Examples 1-3 and Comparative Example 1. It is a graph which shows the analysis result of the nitrogen distribution of the recovery after the dry processing of Example 4. It is a graph which shows the analysis result of the nitrogen distribution of the recovery after the dry processing of Example 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dry processing apparatus of nitrogen-containing waste 2 Reactor 3 Reaction chamber 4 Sample arrangement | positioning part 5 Catalyst arrangement | positioning part 6 Inert gas supply port 7 Water vapor supply port 8 Gas discharge port 10 Sample heating apparatus 11 Catalyst layer heating apparatus 12 Inert gas Supply device 13 Steam supply device 14 Purification / analysis device 20 Sample 30 Catalyst layer 52 Fixed layer two-stage reactor 53 Reaction chamber 54 Sample placement portion 55 Catalyst placement portion 56 Inert gas supply port 57 Steam supply port 58 Gas discharge port 60 Electricity Furnace 61 Electric furnace 70 Microfeeder 71 Ice bath 72 Trap 73 Gas bag

Claims (2)

Ni-containing charcoal for contacting a gas component generated by thermal decomposition of nitrogen-containing waste, wherein nitrogen-containing waste containing 2% by mass or more of at least one kind of nitrogen selected from compost and sewage sludge is disposed upstream. A reactor in which a catalyst layer composed of at least one catalyst selected from Ni-supported alumina and limonite is disposed downstream, a sample heating device for heating nitrogen-containing waste to a thermal decomposition temperature, and heating the catalyst layer A dry treatment apparatus for nitrogen-containing waste, comprising: a catalyst layer heating device for water vapor; and a water vapor supply device for supplying water vapor into a reactor from a water vapor supply port provided between the nitrogen-containing waste and the catalyst layer Is used to thermally decompose the nitrogen-containing waste disposed in the reactor, and the temperature is 550 to 750 ° C. in the presence of steam supplied from the steam supply port to the gas component generated by the thermal decomposition into the reactor. Dry processing method of a nitrogen-containing waste comprising contacting the catalyst layer in the range. A dry treatment apparatus for dry-treating nitrogen-containing waste containing 2% by mass or more of at least one kind of nitrogen selected from compost and sewage sludge, the nitrogen-containing waste being disposed upstream, and nitrogen-containing waste A reactor in which a catalyst layer made of at least one catalyst selected from Ni-supported charcoal, Ni-supported alumina, and limonite for contacting a gas component generated by thermal decomposition is disposed downstream, and nitrogen-containing waste. The sample heating device for heating to the pyrolysis temperature, the catalyst layer heating device for heating the catalyst layer, and steam from the steam supply port provided between the nitrogen-containing waste and the catalyst layer into the reactor. A dry treatment apparatus for nitrogen-containing waste, comprising a water vapor supply apparatus for supplying the nitrogen-containing waste.