JPH1190168A - Desulfurizing agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively desulfurize by using an alkali metallic compd. as a desulfurizing agent which forms a harmless sulfite by reaction with a harmful component such as SOx generated by thermal treatment of waste, etc. SOLUTION: When a material to be treated such as sulfide-contg. waste is incinerated, a large amt. of gaseous SOx is generated. In order to treat the harmful gaseous SOx, a desulfurizing agent made of an alkali metallic compd. which forms a harmless sulfite by catalytic reaction with SOx is used. The alkali metallic compd. is a hydroxide or carbonate and the alkali metal is preferably sodium or potassium. A simple substance or a mixture of plural substances selected from among sodium hydrogencarbonate, sodium carbonate, sodium sesquicarbonate, potassium hydrogencarbonate, etc., is preferably used. A thermal decomposition atmosphere, a dry distillation atmosphere or a low oxygen atmosphere is used as a heated atmosphere in which the desulfurizing agent and gaseous SOx react catalytically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of harmless sulphite by reacting an object to be treated such as waste with a harmful component such as SOx generated when a thermal treatment such as thermal decomposition is performed. It relates to a desulfurizing agent.

[0002]

2. Description of the Related Art Incineration of wastes such as old tires and sulfide-containing wastes such as styrofoam has been performed. However, waste rubber contains 5 to 10% by weight of a sulfide component.
Since it contains it, a large amount of sulfur oxidizing gas (SOx) is generated when it is burned, so that it is necessary to treat it.

As a means for removing SOx, a calcium-based alkaline substance such as lime (CaCO ₃ ) slaked lime (Ca) is used.
(OH) ₂ ) or the like, or incineration, or the removal of these substances by loading them into a filter and passing SOx gas through them, is disclosed in JP-B-2-10341, JP-A-1-296007, This is known from JP-A-59-12733.

This lime (CaCO ₃ ), slaked lime ((Ca
The reaction equation when (OH) ₂ ) is added and incinerated is as follows, and CaSO ₄ (calcium sulfate) is produced.

[0005]

[0006]

When a calcium-based alkali substance is added and incinerated, a certain amount of SOx components can be removed, but it is not sufficient.

Further, CaO or the like reacted with SOx gas is C
aSO ₄ (calcium sulfate), which is commonly known as gypsum, solidifies when it absorbs moisture, making post-treatment extremely difficult. The present invention has been made to solve such a conventional problem.

[0008]

According to experiments by the inventors, in the case of a calcium-based desulfurizing agent such as calcium carbonate, although a certain effect can be expected as compared with no addition, it is not sufficient, and It has been found that desulfurization can be effectively performed by using a potassium-based alkali metal compound as a desulfurizing agent.

Accordingly, the present invention provides a desulfurizing agent based on an alkali metal compound which reacts with harmful SOx gas decomposed and generated from an object to be treated in a heated atmosphere to form harmless sulfite.

That is, when treating waste such as old tires and styrofoam containing sulfide, a desulfurizing agent composed of an alkali metal compound is added to cause a contact reaction with SOx gas, so that the decomposed gas is removed. Harmful SOx components are removed and replaced with harmless sulfites to produce harmless exhaust gas, which can be used effectively as fuel.

Further, this sulfite can be directly dissolved in a solution such as water, and if there is a metal component in the treated product, a harmless residue is obtained. Can be collected and reused.

The catalytic reaction in the present invention is basically
The SOx is not removed in a post-process after the SOx is generated, but is not generated, that is, the SOx is trapped and rendered harmless when it becomes a decomposition gas and precipitates.

Of course, the present desulfurizing agent can also be used as a treating agent in a conventional post-process.

The alkali metal compound as a desulfurizing agent is as follows: (1) A simple substance of the alkali metal compound or a mixture of plural kinds.

(2) The alkali metal compound is a hydroxide,
Carbonate substance.

(3) Hydroxides and carbonates are sodium-based and potassium-based substances.

(4) The desulfurizing agent is (a) sodium bicarbonate, also known as acidic sodium carbonate, sodium bicarbonate, and sodium bicarbonate.

(B) Sodium carbonate, also called sodium carbonate, soda, soda ash, washing soda, and crystal soda.

(C) Sodium sesquicarbonate, also known as sodium hydrogen dicarbonate, sodium tricarbonate, sodium sesquicarbonate, (d) natural soda, also known as trona, (e) potassium carbonate, (f) potassium hydrogen carbonate ( g) Sodium potassium carbonate (h) Sodium hydroxide (i) Potassium hydroxide A simple substance selected from the group consisting of two or more kinds are used in combination.

The heated atmosphere in which the desulfurizing agent and the SOx gas come into contact with each other is an atmosphere in which a pyrolysis gas is generated, for example, a pyrolysis atmosphere, which is intended for a heat treatment furnace and includes combustion and dry distillation. Not specified). Any of a dry distillation atmosphere (intentional to steaming in a dry distillation furnace and oxygen concentration is not specified) or a low oxygen atmosphere (not only a reaction in the furnace but also a reaction in an exhaust gas path) may be used.

The desulfurizing agent is mixed with the object to be treated and heat-treated.

The desulfurizing agent is brought into contact with the SOx gas in the decomposition gas generated from the object to be treated. This reaction is more suitable in the exhaust gas path than in the furnace.

Further, the heated atmosphere in which the desulfurizing agent reacts with SOx is preferably 200 ° C. to 1000 ° C., and the shape, operating conditions (treatment amount, treatment time, etc.) of the heating furnace, and the state and location where the desulfurizing agent is added Determined by

The form of the desulfurizing agent may be any of a lump, a plate, a porous, a powder, a solution, and a suspension, or a combination thereof, depending on conditions such as a treatment amount and a state of a facility. decide.

Under the above conditions, when the sulfide contained is desulfurized with a desulfurizing agent, harmful SOx is obtained as shown in the following reaction formula.
Reacts with gas to produce harmless sulfite. For example, in the case of sodium hydrogen carbonate, (NaHCO ₃ ) → (NaOH) + (CO ₂ ) (2NaOH) + (SO ₂ ) → (Na ₂ SO ₃ ) + (H
₂ O) In the case of potassium hydrogen carbonate (KHCO ₃ ) → (KOH) + (CO ₂ ) (2KOH) + (SO ₂ ) → (K ₂ CO ₃ ) + (H ₂ O) In the case of sodium hydroxide (2NaOH) + (SO ₂ ) → (Na ₂ SO ₃ ) + (2H ₂
O) In the case of potassium hydroxide (2KOH) + (SO ₂ ) → (K ₂ SO ₃ ) + (H ₂ O) In the case of potassium sodium carbonate (Na ₂ CO ₃ + K ₂ CO ₃ ) + (2SO ₂ ) → (2SO ₂ ) Na ₂ SO
₃ ) + (K ₂ SO ₃ ) + (2CO ₂ ), and the harmful SOx gas is replaced with harmless sulfite to generate SOx gas harmless treatment.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory view showing a desulfurization treatment using the desulfurizing agent of the present invention. In FIG.
An object to be treated such as crushed waste is mixed with a desulfurizing agent (for example, sodium hydrogen carbonate). Alternatively, a mixture obtained by other mixing means is charged.

Reference numeral 2 denotes a heat treatment furnace which has a rotating cylindrical shape and is provided with a rotary feeding means for transferring the mixture while stirring it, and heat-treats the mixture of the object to be treated and the desulfurizing agent mixed by the mixing means 1. Reference numeral 3 denotes a heating coil as heating means of the heat treatment furnace 2.

Numeral 4 denotes a residue treatment means, which takes out and puts the residue (processed ash) heated in the heat treatment furnace 2 and performs solid-liquid separation. In solid-liquid separation, the residue is washed with a solution such as water,
The generated sulfite is separated and removed from the residue, taken out together with the solution into the solution discharge section 4a, and the remaining metal, carbide, etc. are taken out into the solid matter take-out section 4b.

Reference numeral 5 denotes an exhaust gas treatment means, which introduces a gas which is generated in the heat treatment furnace 2 and which has been rendered harmless by reacting with the desulfurizing agent, performs necessary processing other than desulfurization, and recovers the gas by the gas recovery means 6; Alternatively, it is discharged after being processed by the secondary combustion means 7.

In a series of processes, as an object to be processed, for example,
Waste rubber and sodium bicarbonate (NaHC
O ₃ ) is charged into the mixing means 1 to mix the two, and after sufficient mixing, is charged into the heat treatment furnace 2.

At this time, the object to be treated is crushed to be fined or crushed while mixing. The addition amount of the desulfurizing agent is 5 to 30% by weight based on the material to be treated.

In the heat treatment in the heat treatment furnace 2, the temperature and time at which SOx gas is deposited from the object to be treated are investigated in advance,
Understand the properties of the object to be processed, and process at a temperature and time that can sufficiently cover the results of this investigation. (For example, 1
time).

Since the time and temperature are related to the state of the heating furnace (conditions depending on the furnace such as the size and heating means), the processing amount, the processing time, the processing temperature, etc. It needs to be done well, and it is necessary to collect and store data.

If the heat treatment is not "combustion and incineration" but "steaming and pyrolysis", the harmful SOx gas deposited can be effectively contacted with the desulfurizing agent, Harmful SOx gas can be replaced with harmless sulfite and generated.

Therefore, in order to maintain the reaction environment, (1) one is that the entire environment is in a stable state necessary for maintaining the reaction, for example, a stable state in a low oxygen atmosphere. That

(For example, it is necessary that a new amount of air does not enter only around the processing object during the processing, and in this case, the combustion starts around the processing object and the reaction becomes unstable. (2) Alternatively, it was found that the reaction could be maintained even by blowing fresh air so that air could be distributed throughout the inside of the pulverized processed material under the condition that the unburned state could be maintained. The result is known.

Decomposition gas containing SOx gas is generated in the heat treatment furnace 2, but the SOx gas immediately reacts with the added sodium hydrogen carbonate to form harmless sulfite, and harmful SOx is generated from the decomposition gas. Separate the gas. This makes the SOx component in the cracked gas harmless and the residual SOx
The x component can be rendered harmless at the same time.

The residue is taken out to the residue treatment means 4 and washed with a solution such as water to separate and remove the sulfite from the residue. As a result, some of the remaining residue has valuable metals,
It contains carbide and the like, and can be effectively reused.

The removal of harmful substances other than the SOx component is carried out by generally known means.

The decomposed gas from which the SOx gas has been removed is discharged or recovered through the exhaust gas treatment means 5 and reused.

The following experimental investigation revealed that the desulfurizing agent of the present invention was made harmless by reacting with SOx gas.

In the experiment, a solidified fuel (hereinafter, referred to as RDF) was used as a sample to be treated.

The RDF is a product which is solidified so as to be combustible. In a broad sense, (1) kitchen wastes (remaining items such as meat, fish head, bones, eggshells, vegetables, fruits, etc., are referred to as "compost") (2) Plastics (polyethylene, polypropylene, polystyrene, polyvinylidene chloride, etc.) (3) Papers (tissue paper, newspaper, advertising paper, bags, boxes, beverage packs, etc.) (4) ) In addition, a solidified mixture of combustible materials (fibers such as cloth, wood chips, rubber, leather, etc.).

In a narrow sense, (2), (3) and (4) which do not include the compost of (1) are referred to.

The RDF of such a sample is crushed, and several kinds of substances are used from among the alkali metal compounds according to the present invention.
In addition, a comparative experiment was performed using a generally known treated RDF (a sulfur component contained about 1.0% by weight).

In the experiment, a low-oxygen atmosphere was created in a closed vessel having an exhaust pipe and an open / close door, a sample was placed in this closed vessel, heated in an electric furnace, and heated from 250 ° C. to 600 ° C. for 5 hours.
The temperature was kept at 0 ° C. for 5 minutes at each temperature, and the exhaust pipe was opened to measure the sulfide gas (SO ₂ ) concentration (ppm) when the temperature was raised and when the temperature was kept.

The gas concentration was measured using a detector tube specified in JIS-KO804.

Table 1 shows the measurement results. The SO ₂ gas concentration is a measured value in 10 experiments, and shows the highest value in Examples 1 to 7 and the lowest value in Comparative Examples 1 to 4.

Note that "ND" represents "not detected",
It shows that none was detected in 10 experiments.

First, 40 g of the conventional crushed RDF and 20 g of the treated RDF are referred to as Comparative Examples 1 and 2, respectively. The lump as it is without crushing the RDF is used. Comparative Example 3 using 40 g and Comparative Example 4 using 40 g of compost
The experiment was performed as follows. The results are shown in Comparative Examples 1 to 4 in Table 1.

Next, 40 g of a general untreated RDF was crushed, and 10 g and 4 g of NaHCO ₃ were added as desulfurizing agents to prepare Examples 1 and 2;
g of KHCO ₃ as a desulfurizing agent and Na ₂ CO 3
₃ , ₃ g of K ₂ CO ₃ , 3 g of NaOH, and 3 g of KOH were added to Examples 3, 4, 5, and 6, respectively. Also, 40 g of massive RDF was used, and NaH was used as a desulfurizing agent.
An experiment was conducted as Example 7 in which 10 g of CO ₃ was added, and Example 8 in which 10 g of a desulfurizing agent of NaHCO ₃ was added to 40 g of compost. Table 1 shows the results.

[0053]

[Table 1]

From the experimental results in Table 1, the following is considered.

In the case of RDF (1) When crushed, some SO ₂ is generated at 400 to 450 ° C., but it is very good as a whole (Example 1).
6), it can be seen that it is considerably reduced even when compared with Comparative Examples 1 and 2.

(2) 350-45 in the case of a lump
As compared with the case where crushed at 0 ℃ was good as a whole but SO ₂ is slightly more occurred (Example 7), it is understood that corresponds reduced as compared with Comparative Example 3.

In the case of compost: (1) Very good results in all temperature ranges (Example 8).

(2) In the case of Comparative Example 4, 350 to 45
Occurs at 0 ° C.

According to the above experimental investigation, when the sulfides contained are desulfurized, an alkali substance (particularly an alkali metal compound) which reacts with harmful SOx gas to form harmless sulfite is added. By doing so, it was confirmed that the SOx could be rendered harmless.

Although a similar dechlorination effect is obtained at 600 ° C. or higher, it may be determined based on the type of equipment, time, amount of treatment, and the like.

The reason why the harmful SOx is replaced with a harmless sulfite has been clarified from the following reaction.

Sodium hydrogen carbonate (NaHCO ₃ ) → (NaOH) + (CO ₂ ) (2NaOH) + (SO ₂ ) → (Na ₂ SO ₃ ) + (H
₂ O) Potassium hydrogen carbonate (KHCO ₃ ) → (KOH) + (CO ₂ ) (2KOH) + (SO ₂ ) → (K ₂ CO ₃ ) + (H ₂ O) Sodium hydroxide (2NaOH) + (SO ₂ ) → (Na ₂ SO ₃ ) + (2H ₂
O) Potassium hydroxide (2KOH) + (SO ₂ ) → (K ₂ SO ₃ ) + (H ₂ O) Potassium sodium carbonate (Na ₂ CO ₃ + K ₂ CO ₃ ) + (2SO ₂ ) → (Na ₂ SO)
₃ ) + (K ₂ SO ₃ ) + (2CO ₂ ) The effect is particularly remarkable in the case of a hydrogen carbonate system.
First, CO ₂ is separated at a temperature equal to or lower than the temperature (300 ° C. or higher) at which the sulfide gas (SO ₂ ) decomposes and precipitates, so that the remaining alkali metal hydroxide (NaOH, KOH) and the generated SO ₂ It is considered that the atmosphere was such that the reaction could be performed smoothly.

That is, when the reaction state is sodium hydrogen carbonate, (NaHCO ₃ ) → (NaOH) + (CO ₂ ) (2NaOH) + (SO ₂ ) → (Na ₂ SO ₃ ) + (H
₂ O) Potassium hydrogen carbonate (KHCO ₃ ) → (KOH) + (CO ₂ ) (2KOH) + (SO ₂ ) → (K ₂ SO ₃ ) + (H ₂ O), and NaOH, KOH and SO ₂ It reacts quickly to produce harmless chlorides (Na ₂ SO ₃ , K ₂ SO ₃ ).

[0064] was produced as described above, Na ₂ SO ₃ (sodium sulfite), K ₂ SO ₃ (potassium sulfite) is a harmless sulfite, in addition to the above substances, likewise, Na ₂ S
There are the following sodium-based and potassium-based substances that generate O ₃ and K ₂ SO ₃ , and similar effects can be obtained.

Sodium carbonate Potassium carbonate Sodium potassium carbonate Sodium carbonate hydrate Sodium sesquicarbonate Natural soda Next, sulfide after treatment was confirmed.

As a result of analyzing the obtained residue, harmful SO was detected.
No x gas component was detected, and alkali metal salts (Na ₂ SO ₃ , K ₂ SO ₃ ), which are harmless sulfites, were detected.

Further, by stirring the residue for 10 minutes and washing with water, the alkali metal salt of sulfite is easily dissolved in water, hydrolyzed to exhibit alkalinity, and (Na ₂ SO ₃ ) + (2H ₂ O) → (2NaOH) + (H ₂
SO ₃ ) (K ₂ SO ₃ ) + (2H ₂ O) → (2KOH) + (H ₂ SO
₃ ) These substances were dissolved in water and carbide remained, but no harmful SOx gas component was detected in the carbide.

Therefore, the harmful SOx components become a part of the residue, such as sodium sulfite (powder) (Na ₂ SO ₃ ), potassium sulfite (powder) (K ₂ SO ₃ ), moisture (H ₂ O),
Gas (CO ₂ ), preventing the generation of SOx gas,
It was confirmed that the detoxification of SOx gas can be realized from the decomposition gas and the residue.

Examples of the desulfurizing agent used for the desulfurization treatment include: (1) a simple substance of an alkali metal compound, a mixture of plural kinds thereof, and (2) the alkali metal compound is a substance of hydroxide or carbonate. ) Hydroxides and carbonates are sodium-based and potassium-based substances. (4) The desulfurizing agent was selected from sodium bicarbonate sodium carbonate sodium sesquicarbonate natural soda potassium carbonate potassium hydrogencarbonate sodium potassium potassium sodium hydroxide potassium hydroxide It was also found that a single substance or a mixture of plural kinds was suitable.

Therefore, the harmful SO in the generated decomposition gas
harmful SO by the contact reaction between x-gas and the added desulfurizing agent
Since the x gas is replaced and generated by harmless sulfites (Na ₂ SO ₃ , K ₂ SO ₃ ), the SOx gas can be separated from the decomposition gas, and the harmless decomposition gas can be obtained.

On the other hand, harmless sulphite which becomes a part of the residue can be effectively removed by washing treatment with a solution such as water, and after washing, reusable metals and carbides remain, and harmful SOx gas is removed. Because it does not contain any components, it can be reused.

The removal processing of a gas other than SOx (eg, hydrogen chloride) is performed by generally known exhaust gas processing.

[0073]

As is evident from the results of the experiment, when treating wastes containing sulfides, desulfurization that effectively reacts with SOx gas in the generated decomposition gas to produce harmless sulfites By adding a chemical agent, harmful SOx gas can be separated from the cracked gas, SOx detoxification of the cracked gas can be realized, and by removing other harmful gas components, the exhaust gas can be used effectively as fuel etc. Become.

Further, the present invention exerts extremely excellent effects such as detoxification of the residue and effective reuse of the remaining metal and carbide.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a desulfurization treatment using a desulfurizing agent of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mixing means 2 heat treatment furnace 3 heating coil 4 residue treatment means 5 exhaust gas treatment means 6 gas recovery means 7 secondary combustion means

Claims (9)

[Claims] 1. A desulfurizing agent that reacts with a harmful SOx gas decomposed and generated from an object to be treated in a heated atmosphere,
A desulfurizing agent composed of an alkali metal compound that reacts with harmful SOx gas to form harmless sulfite. 2. The desulfurizing agent according to claim 1, wherein the alkali metal compound is a hydroxide or a carbonate. 3. The hydroxide and carbonate are sodium-based,
The desulfurizing agent according to claim 2, wherein the desulfurizing agent is a potassium-based substance. 4. The desulfurizing agent includes sodium hydrogen carbonate, sodium carbonate, sodium sesquicarbonate, natural soda, potassium carbonate, potassium hydrogen carbonate, sodium potassium carbonate,
Simple substance selected from sodium hydroxide and potassium hydroxide,
The desulfurizing agent according to claim 1, wherein the desulfurizing agent is a mixture of a plurality of types. 5. The desulfurizing agent according to claim 1, wherein the heated atmosphere in which the desulfurizing agent and the SOx gas are contact-reacted is any one of a pyrolysis atmosphere, a dry distillation atmosphere, and a low oxygen atmosphere. 6. The desulfurizing agent according to claim 1, wherein the desulfurizing agent is mixed with an object to be treated, heat-treated and subjected to a contact reaction. 7. The desulfurizing agent according to claim 1, wherein the desulfurizing agent is brought into contact with an SOx gas in a decomposition gas generated from an object to be treated. 8. The desulfurizing agent according to claim 1, wherein the desulfurizing agent is in the form of a mass, a plate, a porous material, a powder, a solution, a suspension, or a combination thereof. The desulfurizing agent according to item. 9. The desulfurizing agent according to claim 1, wherein the heated atmosphere in which the desulfurizing agent reacts with the SOx gas is at 200 ° C. to 1000 ° C.