JPS5837417A - Purification of combustion exhaust smoke - Google Patents

Abstract

PURPOSE:To burn the smoke completely and consequently remove soot and carbon monoxide by a structure wherein combustion improver, which mainly consists of two constituents of CaO and Fe2O3 or three or four constituents of above-mentioned two constituents and MgO or/and Al2O3, is arranged in the neighborhood of the outlet of the combustion chamber of a furnace as smoke removal layers. CONSTITUTION:CaO type raw material such as limestone, dolomite or the like is blended with Fe2O3 type raw material such as limonite, magnetite of the like and, after being mixed and kneaded, molded and baked into clinker, which is milled again, molded again into the predetermined form and baked again in order to get combustion improver. In this case, when heat resisting property is required, MgO is added. Al2O3 is added for stabilizing CaO and at the same time for improving heat resisting property. By piling up said combustion improver in layers in the neighborhood of the outlet of the combustion chamber of the combustion furnace as smoke removal layers, the smoke is completely burnt, resulting in enabling to remove soot and carbon monoxide.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly uses CaO in the vicinity of the combustion chamber outlet of a furnace that burns inferior fuel such as stone legs and residual oil, or flame-retardant garbage such as synthetic resin scraps and old tires.

Two components of Fe2O3 or MgO or/and A
A 5-component or 4-component combustion accelerator with hO5 added,
Furthermore, if necessary, a combustion accelerator consisting of at least one metal oxide effective as a combustion catalyst, such as steel oxide, chromium oxide, and cobalt oxide, is added to the combustion accelerator. The agent is installed as a soot removal layer, and the soot and smoke are completely combusted in this layer to remove soot and hypoxic oxide. Furthermore, ammonia is injected in front of the keratin layer to remove nitrogen oxides in the soot and smoke into this layer. Recently, since the successive oil crises, the promotion of energy conservation has been called for, and coal has been reconsidered as an alternative energy source to replace petroleum, and coal has already been used for thermal power generation. The fuel for boilers in industrial plants is gradually replacing petroleum with lime, and as imported crude oil becomes heavier, the fuel for industrial furnaces has to change from light, good fuel to heavy, inferior fuel. However, these inferior fuels such as lime and heavy oil, as well as flame-retardant garbage such as synthetic resin waste and old tires incinerated in garbage incinerators, must be used when burning. For complete combustion, 1
A high temperature of about 500°C is required, and combustion efficiency is low in low temperature conditions such as when the temperature rises, and the generation of soot cannot be avoided, so soot gets mixed into the flue gas and causes pollution. In severe cases, the flue becomes clogged with soot, which obstructs the flow of smoke and further reduces combustion efficiency, and also increases the content of electrolyte oxides, which cause pollution. ing.

The present inventors focused on the above-mentioned problems, and as a result of conducting various researches to solve these problems, the inventors found that two components, CaO and Fe2O3 as main components, or MgO or These problems can be completely resolved by installing a combustion accelerator consisting of 3 or 4 components containing 2 and AlhOs as an fX smoke removal layer, and by injecting ammonia in front of this layer. The present invention has been completed based on this discovery.

CaO, MgO minerals with Fe2O5 added,
One of the inventors, Morita et al., reported that it is effective as a combustion accelerator for residual oil and as a catalyst for reducing NoX using ammonia.
As reported on page 1, this is already known, but this combustion accelerator is used as a fluidized material in fluidized bed combustion, and as in the present invention, the combustion accelerator is formed into a molded body and stacked at the outlet of the combustion chamber. It is not used as a soot removal layer. Therefore, this method cannot be applied to furnaces other than fluidized bed furnaces, but if a combustion accelerator is used as in the present invention,
It is not only an extremely effective way to purify flue gas, but it can also be applied directly to existing furnaces other than fluidized bed furnaces without requiring special furnace design changes, making it extremely easy to apply to all types of furnaces. This has advantages, and there is still no method for purifying flue gas using such a method.

The combustion accelerator used in the present invention is a CaO-based raw material such as limestone or dolomite ore, and a combination of magnetite, magnetite, etc.
205-based raw materials are blended in a predetermined ratio, mixed, kneaded, molded, and fired to 1000 to 1300 tons to form clinker, which is then ground again and molded into a predetermined shape to produce clinker at a temperature similar to that of the clinker firing temperature. Low temperature -r: Obtained by re-firing. At this time, if the OaO in the baked product comes into direct contact with the atmosphere in a free state, it will react with water vapor and uric acid gas in the atmosphere and turn into water. C
It is necessary to bind aOId, iron, alumina, etc., or to coat the surface with these or magnesia, so that free CaO does not come into direct contact with the atmosphere.

Therefore, when the amount of Fe2O3 blended is small, Ca
It is necessary to manufacture clinker by sprinkling the surface of O particles with pe2o5 powder and then molding the product and firing it. In addition, when blending a large amount of CaO203, add Fe to the CaO raw material pre-calcined at around 900°C.
It may also be produced by adding 2O3, adding a liquid other than water such as terμ, kneading, molding into a predetermined shape, and directly firing at a predetermined temperature without passing through a clinker. Glossy, CaO
i''-e205 is added to the raw material and calcined to form μsium aluminate, which is then impregnated with an aqueous solution of iron inorganic and organic acid salts such as an aqueous iron nitrate solution, calcined, and then calcined at a specified base. It may also be produced by supporting iron.

(The blending ratio of e205 to lao is 6
0-97:5-40, preferably 70-95:5-5
It is 0. If the amount of Fe2O3 is less than 3 ca, sufficient combustion efficiency cannot be obtained, and CaO is completely reduced to 2 ca.

・Since it cannot be coated with Fe2O3, a stable combustion accelerator cannot be obtained. Further, even if the amount of Fe2O3 exceeds 40%, there is no difference in combustion efficiency, and not only no improvement is observed, but also the heat resistance of the combustion accelerator is impaired, which is not preferable.

In addition to the above-mentioned limestone and dolomite ore, nitrate lime, quicklime, etc. can be used as CaO raw materials, and it can also be supplied from alumina cement.

In addition to the above-mentioned limonite and magnetite, iron oxides or hydroxides such as hematite are suitable as Fe2O3 raw materials,
Furthermore, aqueous solutions of inorganic and organic acid salts of iron are used as raw materials for impregnation.

MgO is added when heat resistance is particularly required for the combustion accelerator, and its blending amount accounts for 50% of the total combustion accelerator.
wt% or less. If the blending amount exceeds 50, the combustion efficiency will be extremely reduced, which is not preferable. As a raw material, C
When dolomite ore is used as the aO raw material, MgO
is necessarily supplied from dolomite ore, but in the case of other raw materials, magnesite, seawater magnesia, magnesium hydroxide, etc. are used.

Al2O3 is used to stabilize CaO and improve heat resistance, and its content is equal to or less than the CaO content, that is, k120. is less than 1:1. If this ratio exceeds 1:1, it is not preferable because it reduces combustion efficiency. As raw materials, when alumina cement is used as a CaO raw material, 120g of A is inevitably supplied in the alumina cement, but other materials such as bauxite, payer alumina, aluminum oxide, aluminum hydroxide, and fused corundum are also available. used.

Combustion catalytic metal oxides such as steel oxide, chromium oxide, cobalt oxide, nickel oxide, and vanadium oxide are added when a combustion promoter with particularly high combustion efficiency is required, and is used for flame-retardant fuels such as old tires. It is effective if used in a furnace that burns. The amount of this added is 2
-10% range, less effective, less than 10%
The effect does not change even if more than 100% is added. Inorganic or organic acid salts of these metals can be used as raw materials, and are effective when supported by an impregnation method.

The shape of the combustion accelerator is brick-like, gitsu-like,
Any shape such as a checker, honeycomb, Raschig ring, or spherical shape, or one made porous by mixing a pore agent can be used as appropriate.

If the combustion accelerator produced as described above is stacked in layers near the outlet of the combustion chamber of a combustion furnace and installed as a soot removal layer, the combustion efficiency will be 98-98 compared to 95-96 when not installed. Even when the soot removal layer is at a low temperature of around 700℃, the combustion efficiency shows a value of 97 degrees or higher, so even at low temperatures during temperature rise, almost no soot is left in the flue gas or flue. It will no longer be recognized. Furthermore, by injecting annealing into the vicinity of the soot removal layer in the furnace, it was possible to reduce the concentration of nitrogen oxides at the flue outlet by about 50%.

The optimum operating temperature range for this combustion accelerator is 800-1050.
C. If the improvement in combustion efficiency is taken into consideration, a higher operating temperature is preferable, but if the heat resistance of the combustion promoter is considered, it is appropriate to keep the temperature within this range. In addition, an excess air ratio of around 20% during combustion is optimal for improving combustion efficiency, but the denitrification rate tends to decrease as the excess air increases, so an appropriate excess air ratio is 10 to 10%.
A range of about 25 attacks is appropriate.

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

Example 1 Limestone and limonite were crushed and blended, calculated so that aO: Fe2O3 = 7:2, and after kneading, the mixture was molded into the size of a regular brick and fired at 1200°C to produce Talin force. . This Talinker is re-pulverized and formed into a Rashitz ring shape with an outer diameter of 50M, an inner diameter of 10B, and a height of 30fi.
It was fired to 150 tons to produce a combustion accelerator. This combustion accelerator was placed in front of the exhaust heat boiler at the exit of the combustion chamber of the combustion furnace, with the Raschig ring holes parallel to the exhaust smoke flow direction, stacked side by side, and a soot removal layer was installed, and used for the test. did.

The fuel used was Arabian Light vacuum residue having the following properties.

Fuel properties: Specific gravity to11s 15/4℃, C85.5
wt%, u10.6wtchi, S3.87wt%, CCR
17.67wt poly, saturates 28.3wt%, H/C1
, 49 ammonia was subjected to a denitration test by inserting a nozzle into the furnace from outside the furnace in front of the combustion chamber outlet and blowing a specified amount of ammonia into the furnace.

As shown in Table 1, good results were obtained in both combustion efficiency and denitrification rate. The combustion efficiency and NOx reduction rate were calculated using the following formula.

However, (A): N at the outlet when NH3 is not added
Ox concentration (B): NO at the outlet when adding NHs
x Concentration Example 2 70 parts of the clinker of Example 1 was mixed with 30 parts of seawater magnesia clinker, treated in the same manner as in Example 1, and fired at 1350°C to produce a combustion accelerator. Using this combustion accelerator, a soot removal layer was installed at the outlet of the combustion chamber of the furnace in the same manner as in Example 1, and a test was conducted using the same fuel as in Example 1 (this fuel was used in all examples below). did. However, in this case, the temperature of the soot removal layer was raised to 900°C. As shown in Table 1, the combustion efficiency was 99 cm, and the denitrification rate was even better.

Example 3 Limestone, 60 parts and paya! 40 parts of mina was mixed, molded into the size of a sub-mold brick, and fired at 1650°C.
A clinker made of μsium chloride was installed. This clinker was re-pulverized and formed into the Rashitz ring shape of Example 1, and the sintered body was fired to 1300 tU. The sintered body was impregnated with an aqueous iron nitrate solution to support 811I iron, and calcined at 900°C to promote combustion. The drug was manufactured. This combustion accelerator was used, a soot removal layer was installed in the same manner as in Example 1, and the test was conducted. As shown in Table 1, good results were obtained.

Examples 4 to 6 In Example 4, 75 parts of the aluminic acid clinker of Example 3 was mixed with 25 parts of seawater magnesia clinker and fired at 1600°C. A soot removal layer was formed by impregnating and supporting about 6 volumes of Fe2O2 in the same manner as above.

In Example 5, a soot removal layer was used in which the combustion accelerator of Example 1 was impregnated with an aqueous copper nitrate solution and CuO was supported for about 6 hours to improve combustion efficiency and denitrification rate.

In Example 6, kudzu-produced dolomite ore was used as the CaO raw material, 13 parts of magnetite was blended with 87 parts of the crushed product, and after molding, the clinker was fired at 1200°C to produce clinker. As shown in Table 1, all of the combustion promoters of Examples 4 to 6 showed good results in both combustion efficiency and denitrification rate.
In particular, excellent results were obtained in Example 5, in which CwO was supported.

Comparative Example In the comparative example, a test was conducted using the fuels of Example and 14 in a furnace made of silica Gitzter bricks and equipped with a soot removal layer.The results are shown in Table 1. In addition, both the combustion rate and the denitrification rate were low, demonstrating the effectiveness of the method of the present invention.

The following is a written amendment to the proposed procedure (self-insurance) dated October 6, 1980 Kazuo Wakasugi, Commissioner of the Patent Office, 1. Indication of the case, 1988 Patent Application No. 1306'1 No. 3, Relationship with the person making the amendment Patent Applicant 4, Agent Address: 14 (1) 505 Oshima, Kurashiki City, 710 Column 8 of Detailed explanation of the invention as revised by the Meiji provisions, Attachment 1) Specification letter page 8, line 8 Insert ``potassium oxide, sodium oxide'' between ``cobalt oxide'' and ``chive oxide.''

2) Insert "85-90% when using especially poor quality fuel" between "95-96%" and "degree" on page 9, line 5.

that's all

Claims (1)

[Claims] 1. Mainly OaO near the exit of the combustion chamber of the furnace. Two components of Fe2O3 or MgO or/and 1
! A method for purifying combustion exhaust smoke, which comprises installing a soot removal layer made of a three-component or four-component combustion accelerator with 20s added thereto, and burning and purifying the soot and smoke through the soot removal layer. 2 Mainly OaO near the exit of the combustion chamber of the furnace. Two components of Fe 205 or this with Mgo or/
A soot removal layer consisting of a five-component or four-component combustion accelerator containing AlhOs and a combustion catalyst such as a metal oxide such as copper oxide, chromium oxide, or cobalt oxide is installed, and the soot and smoke are removed. A method for purifying combustion exhaust smoke characterized by burning and purifying soot and smoke in a removal layer. 3 Mainly CaO near the exit of the combustion chamber of the furnace. Two components of Fe2O3 or MgO or/and k
A soot removal layer consisting of a three-component or four-component combustion accelerator, or a combustion accelerator and a combustion catalyst such as a metal oxide such as oxidized steel, chromium oxide, or cobalt oxide. A method for purifying combustion flue gas, characterized in that ammonia is blown in from before the soot removal layer to burn and purify the soot and reduce and remove nitrogen oxides in the flue gas.