JP4296271B2 - Gypsum processing method - Google Patents

Description

  The present invention relates to a method for treating gypsum. More specifically, the present invention relates to a method for treating gypsum in which gypsum is converted into calcium carbonate and hydrogen sulfide by supplying water vapor to a mixture of gypsum and a predetermined amount of biomass and gasifying it.

  Gypsum is by-produced by limestone slurry or the like, and these gypsum are used as a raw material for gypsum board and cement. In particular, many of them are made into boards as biomass-containing plaster and used for building interior materials. About 2 million tons of gypsum containing gypsum and biomass (hereinafter referred to as “gypsum waste material”) is said to be generated annually in Japan. About 1 million tons of gypsum waste discharged from renovation and demolition work of houses and buildings are disposed of in landfills. The amount of gypsum waste generated tends to increase year by year, and recycling of gypsum waste is required from the viewpoint of lack of landfill and environmental conservation.

Conventionally, as a treatment of gypsum waste material, a method is known in which gypsum is burned in a kiln and sulfuric acid is recovered from exhaust gas containing quicklime and SO ₂ . In addition, as shown below, the gypsum is sulfided by spraying gypsum powder that has been pulverized and dried in advance in a high-temperature reducing gas stream containing hydrogen and / or carbon monoxide, carbon dioxide, and water vapor. By converting to calcium and then cooling this gas stream, the calcium sulfide is converted into calcium carbonate and hydrogen sulfide, which is led to a dust collector and separated into a solid containing calcium carbonate and a gas containing hydrogen sulfide (patented) Document 1) has been proposed.
CaSO ₄ + 4H ₂ → CaS + 4H ₂ O (conversion to CaS by hydrogen)
CaSO ₄ + 4CO → CaS + 4CO ₂ (conversion to CaS by carbon monoxide)
CaS + CO ₂ + H ₂ O → CaCO ₃ + H ₂ S (carbonation during cooling)
JP-A-61-63504

According to the above conventional method, equipment for supplying a reducing gas such as H ₂ and CO is required, and dust and exhaust gas treatment is complicated. In the case of a kiln, quick lime and calcium sulfide generated for uneven heating are used. Sintering progressed, hindering the next process and insufficient control of the reaction.
The present invention has been made in order to overcome the above problems against the background of the actual situation, and achieves the following object.
An object of the present invention is to provide a gypsum processing technology that does not require a reducing gas supply facility when processing gypsum waste, and performs processing by effective use of resources with a simple configuration by using biomass.
Another object of the present invention is to provide a gypsum treatment technique that allows easy gasification treatment with easy reaction control.

As a result of intensive research on the background of such problems, the present inventor made the present invention to react a mixture of gypsum and a predetermined amount of biomass with water vapor under a high temperature condition at a low pressure. The reaction between biomass and steam produces hydrogen, carbon monoxide and carbon dioxide, and gypsum is converted to calcium sulfide, and then cooled, the calcium sulfide is converted to calcium carbonate and hydrogen sulfide for separation. is there.
Furthermore, when reacting a mixture of gypsum and a predetermined amount of biomass with water vapor, if the carbon dioxide absorbing material is allowed to coexist, the biomass is mainly gasified into hydrogen and carbon dioxide, and hydrogen is efficiently generated, Conversion of gypsum to calcium sulfide and conversion of calcium sulfide to calcium carbonate and hydrogen sulfide can be performed efficiently. The present invention has been made on the basis of these technologies, and is intended to further improve technological development.

  In addition, the biomass as used in the present invention means organic resources derived from living organisms excluding fossil fuels such as coal and oil, and forests, agricultural products, seaweeds and seafood, or organic waste after using these. Renewable organic resources including By using this biomass, it is possible to secure renewable energy, and since it is an organic material, it has the potential to become a high-range energy resource and has no problem with environmental problems. It means that it can be utilized. The present invention takes the following means to achieve the above object.

  The gypsum treatment method of the present invention 1 is a mixture of gypsum and biomass, which is reacted by supplying water vapor under conditions of a pressure of less than 1.5 MPa and a temperature of 650 ° C. to 800 ° C. Gasifying into a gas containing carbon monoxide and carbon dioxide, the gypsum is converted into calcium sulfide by the hydrogen and carbon monoxide generated by the gasification, and the calcium sulfide contains water vapor and the carbon dioxide. It is characterized by being cooled to a temperature of 400 ° C. or lower together with a gas component and converted into calcium carbonate and hydrogen sulfide.

The gypsum treatment method of the present invention 2 is the gypsum treatment method of the invention 1,
The mixture of gypsum and biomass is composed of one or more oxides or hydroxides selected from calcium (Ca), magnesium (Mg), strontium (Sr), barium (Ba), and iron (Fe). A carbon dioxide absorbing material is added and coexisted, and the biomass is gasified while part of the carbon dioxide generated from the biomass is absorbed by the carbon dioxide absorbing material.

  The gypsum treatment method of the present invention 3 is characterized in that, in the gypsum treatment method of the present invention 2, the carbon dioxide is added to convert the calcium sulfide into the calcium carbonate during the cooling.

  The gypsum treatment method of the present invention 4 is the gypsum treatment method of the first to third aspects of the present invention, wherein the mixture containing the calcium carbonate and the hydrogen sulfide is led to a dust collector, and the solid calcium carbonate and the gas It is characterized by separating into hydrogen sulfide.

  The gypsum treatment method of the present invention 5 is characterized in that, in the gypsum treatment method of the present invention 1 to 4, the reaction is carried out under conditions of a pressure of less than 1.0 MPa and a temperature of 700 ° C to 800 ° C.

  The gypsum treatment method of the present invention 6 is the gypsum treatment method of the present invention 2 to 5, wherein the carbon dioxide-absorbing substance is removed as carbonate and then reused by removing the carbon dioxide by heating. It is characterized by that.

The gypsum treatment method of the present invention 7 is the gypsum treatment method of the present invention 1 to 3, wherein the reaction is a ratio of the number of moles of carbon [C] in the biomass to the number of moles of the gypsum [CaSO ₄ ]. The reaction is performed by supplying the biomass so that [C] / [CaSO ₄ ] is 4 or more.

Processing method of plaster of the present invention 8 is the first to process how the third plaster of the present invention, the number of moles of the steam to the number of moles of carbon [C] of the biomass in the reaction [H 2 _O] in The water vapor is supplied so that the ratio [H ₂ O] / [C] is 2 or more.

  The method for treating gypsum according to the present invention 9 is the method for treating gypsum according to 2 or 3 according to the present invention, wherein the reaction is carried out in the number of moles of the carbon dioxide absorbing material to be added to the number of moles of carbon [C] in the biomass. The ratio is less than 0.5, and the reaction is such that the carbon dioxide produced is not completely absorbed.

The present invention, as long as in line with the above objects, configuration combining two or more selected from among 1-9 of the present invention is naturally also be employed.

  According to the present invention, the biomass is coexisted with gypsum and steam gasified under a very mild reaction condition of a temperature of 650 to 800 ° C. and a pressure of less than 1.5 MPa, and then cooled and processed, so that the compact The composition makes it possible to effectively use resources and efficiently separate gypsum into solid calcium carbonate and hydrogen sulfide, a gas useful as a sulfur source. Moreover, the reaction was promoted by coexisting a carbon dioxide-absorbing substance and gasified into steam, and the ratio of hydrogen in the gas could be increased. By using biomass, processing without waste of resources was possible, and it became a processing method with no environmental problems.

Hereinafter, the embodiment of the processing method of gypsum of the present invention is described. As described above, the method for treating gypsum of the present invention is a mixture of gypsum and a predetermined amount of biomass, or a mixture of gypsum and a predetermined amount of biomass in which a carbon dioxide absorbing substance coexists. By converting biomass into steam gas, it is converted to hydrogen, carbon monoxide, carbon dioxide, etc., and these gases are used to carbonate calcium sulfate, the main component of gypsum, into calcium carbonate, which is a mixture of gypsum and biomass Is a method of separating calcium carbonate into hydrogen carbonate and hydrogen sulfide.
In the present invention, water vapor is supplied to a mixture of gypsum and biomass, but it is biomass that directly gasifies with water vapor, and the gas generated by this reaction reacts with gypsum. The mixing ratio of gypsum and biomass is determined to be a predetermined ratio in consideration that the gypsum waste material also contains biomass, and is supplied to a reaction facility such as an autoclave.

  More specific reaction conditions will be described. A mixture of gypsum and a predetermined amount of biomass or a mixture of gypsum and a predetermined amount of biomass in which a carbon dioxide-absorbing substance coexists at a pressure of less than 1.5 MPa. When steam gasification is performed in a reaction field at a temperature of 650 to 800 ° C., biomass efficiently generates hydrogen, carbon monoxide and carbon dioxide, and the hydrogen sulfate and carbon monoxide generate calcium sulfate as the main component of gypsum. Converted to calcium sulfide. Next, when the calcium sulfide is cooled to a temperature of 400 ° C. or less together with gas components including water vapor and carbon dioxide, the calcium sulfide is converted into calcium carbonate and hydrogen sulfide, and the calcium carbonate is solid and the hydrogen sulfide is separated as a gas.

  Thus, gypsum can be separated into calcium carbonate and hydrogen sulfide by reacting a mixture of gypsum waste and biomass with a simple structure. This will be described in detail below.

  The present inventor efficiently gasifies biomass mainly into hydrogen, carbon monoxide and carbon dioxide when steam gasification is performed under a reaction condition of a temperature of 600 to 800 ° C. alone and a pressure of less than 2.5 MPa. Make sure you can. For example, when woody biomass such as cornwood or cedar is steamed, about 70% is gasified on a weight basis.

  This is because woody biomass has a higher proportion of volatile matter than coal and heavy oil. The main components of the woody biomass are cellulose, hemicellulose and lignin, and the cellulose is structured to be protected by lignin, and they are considered to volatilize at 200 to 500 ° C. Such a tendency is also observed in other types of biomass, but especially paper does not contain lignin that decomposes at higher temperatures (280 to 500 ° C.), so it is considered that it is easier to decompose when using paper as biomass. It is done.

For example, a metal species such as nickel (Ni), ruthenium (Ru), platinum (Pt), or palladium (Pd) is replaced with α-alumina (α-Al ₂ O ₃ ) or zirconium oxide (ZrO) as a support. _When the supported metal catalyst supported on ₂ ) is allowed to coexist in the reaction field, the steam reforming reaction of the compound (tar) which has a relatively large molecular weight and condenses at room temperature and normal pressure can be promoted and the gasification rate can be improved.

If the general chemical formula of biomass is expressed as CxHyOz,
CxHyOz → (x−z) C + zCO + (y / 2) H ₂ (1)
By this reaction, biomass is decomposed thermochemically.

Furthermore,
C + H ₂ O → H ₂ + CO (2)
C + CO ₂ → 2CO (3)
Such a reaction occurs, and is relatively easily chain-decomposed into gaseous carbon. The composition of the gas produced by these gasification reactions is mainly composed of carbon monoxide, water vapor, carbon dioxide and hydrogen, and each composition gas reaches chemical equilibrium by the following chemical equilibrium equation.
CO + H ₂ O⇔CO ₂ + H ₂ (4)
At that time, the ratio of each composition gas remains at a constant equilibrium value depending on conditions such as pressure and temperature. For example, the ratio of hydrogen is about 30% of the whole under the condition of a pressure of less than 2.5 MPa and a temperature of 600 to 800 ° C. Occupy.

  When a carbon dioxide-absorbing substance (for example, CaO) coexists in the reaction field in advance, a reaction that absorbs and removes carbon dioxide from the generated gas occurs, and the chemical equilibrium equation (4) generates carbon dioxide and hydrogen ( That is, it reacts in the chemical equilibrium formula (4). And the carbon dioxide newly produced | generated by this reaction reacts with a carbon dioxide absorption substance further, and is absorbed. In this way, the reaction proceeds sequentially, and finally the proportion of hydrogen in the gas can be increased, for example, it can be improved to about 80%.

  In the steam gasification of biomass, the biomass can be efficiently gasified under conditions of a temperature of 600 to 800 ° C. and a pressure of less than 2.5 MPa, and the chemical equilibrium of the chemical equilibrium formula (4) can be reached. It is as follows. In an experiment using Quercus wood chips as biomass, when the reaction field pressure was changed from 0.3 MPa to 2.5 MPa, the gasification rate and hydrogen yield were maximized around 0.6 MPa. In addition, when the pressure is further increased, the gasification rate and the hydrogen yield are decreased. That is, the gasification rate is better when the pressure is lower than 2.5 MPa.

  This result means that when woody biomass such as waste wood and paper are used as starting materials, it can be gasified even at low pressure as described above, and the pressure is actively less than 2.5 MPa. This suggests that it is better to have a low pressure state. Biomass gasification and hydrogen generation processes are complicated processes in which various reactions such as the above reaction formulas (1) to (4) proceed in a complex manner. I can say that.

  That is, the above-described thermochemical decomposition reaction of biomass [see reaction formula (1)] and the steam reforming reaction of tar are both reactions in which the number of moles is increased. Is easy to progress. That is, in the biomass steam gasification experiment described above, when the pressure is increased from 0.6 MPa, the gasification and hydrogen yield of bimass decrease, and when the pressure is increased, the volatilization of the biomass itself is inhibited, and the thermochemical decomposition reaction of biomass and Biomass steam reforming reaction is difficult to proceed, and biomass gasification and hydrogen generation are hindered.

As described above, biomass itself is gasified sufficiently easily even under steam gasification conditions at a temperature of 600 to 800 ° C. and a pressure of less than 2.5 MPa. And steam reforming reaction proceeds. For this reason, it is easy to reach the chemical equilibrium formula (4). However, as shown in the examples described later, since the conversion reaction of calcium sulfate to calcium sulfide by hydrogen is an endothermic reaction, from the viewpoint of conversion efficiency and the like, as the steam gasification conditions, the pressure is less than 1.5 MPa. The temperature is preferably from 650 to 800 ° C., more preferably from 700 to 800 ° C. under a pressure of less than 1.0 MPa.
Under such steam gasification conditions, the gasification rate of biomass shows 50% or more on a carbon basis, mainly hydrogen and carbon dioxide are present, and calcium sulfate is converted to calcium sulfide. During cooling, carbonation of calcium sulfide is promoted by water vapor and carbon dioxide to produce calcium carbonate.

Now, in the reaction of the present invention in which biomass is mixed with gypsum, or biomass and carbon dioxide-absorbing substances are allowed to coexist in gypsum, and the biomass is steam gasified to treat the gypsum, carbon (C) 1 atom in biomass described above For every,
C + 2H ₂ O → CO ₂ + 2H ₂ (5) (Biomass steam gasification)
The chemical reaction occurs.
To be exact, the biomass contains a large amount of hydrogen atoms and oxygen atoms, but as shown in the above reaction formula (5), the number of moles of water vapor relative to the number of moles of carbon in the biomass [C] in the reaction field. [H 2 _O] ratios of _{[H 2 O] / [C} ] is, if the supply of steam at 2 or more, theoretically can be reacted without leaving biomass.
Next, reaction formula (6) in which calcium sulfate is converted to calcium sulfide by hydrogen generated by gasification of biomass, and further, reaction in which calcium sulfide is converted to calcium carbonate by coexisting water vapor and carbon dioxide to generate hydrogen sulfide. Formula (7) is demonstrated.
CaSO ₄ + 4H ₂ → CaS + 4H ₂ O (6) (Conversion to CaS by hydrogen)
CaS + CO ₂ + H ₂ O → CaCO ₃ + H ₂ S (7) (Carbonation during cooling)

  The conversion reaction formula (6) of calcium sulfate to calcium sulfide is said to occur at 700 ° C. or higher. In this reaction, diffusion of hydrogen from the surface of the gypsum particles to the inside becomes important. It gets faster as you make smaller. When the particles are large, the diffusion rate is dominant, so that even if the reaction temperature is 800 ° C. or higher, there is no effect on the formation of calcium sulfide. In the steam gasification reaction of biomass, when gypsum particles are small, the conversion reaction formula (6) of calcium sulfate to calcium sulfide by hydrogen occurs even at 650 ° C. From this, it can be said that the gypsum treatment temperature of the present invention is usually preferably in the temperature range of 650 to 800 ° C. On the other hand, when the pressure is set to 1.5 MPa or more, the conversion reaction of calcium sulfate to calcium sulfide hardly occurs. Therefore, the pressure during gasification is preferably less than 1.5 MPa.

  Further, the carbonation reaction formula (7) of calcium sulfide is an equilibrium reaction, and the temperature must be 400 ° C. or lower in order to complete the reaction. Since the rate of carbonation reaction is slow, it is preferable to promote the reaction at a reaction temperature of 400 ° C. or lower. Therefore, in the present embodiment, carbonization can be easily performed by performing steam gasification of biomass at a gypsum treatment temperature of 650 to 800 ° C. and then air cooling to room temperature. In order to perform carbonation of gypsum more effectively, it is preferable that the gypsum has a smaller particle size as described above. In this embodiment, the gypsum is 50 microns or less.

Further, as is clear from the above-mentioned formulas (6) and (7), the ratio [H ₂ ] / [CaSO ₄ ] of the mole number of hydrogen [H ₂ ] to the mole number [CaSO ₄ ] of gypsum is 4 above, the number of moles of gypsum [CaSO _4] moles of carbon dioxide for the ratio of _{[CO 2] [CO 2]} / [CaSO 4] is required to be 1 or more. In the gypsum treatment of the present embodiment, the amount of biomass mixed with the gypsum when the gypsum is completely carbonated stoichiometrically with respect to the number of moles of gypsum [CaSO ₄ ] as in the following formula (8). The ratio [C] / [CaSO ₄ ] of the number of moles [C] of carbon in the biomass is 2 or more.
_{2C + H 2 O + CaSO 4} → CaCO 3 + H 2 S + CO 2 ... (8)
However, since the current gasification rate of biomass is 50% or more, the molar ratio is preferably 4 or more.

Now, if a carbon dioxide absorbing material coexists in the reaction field in advance, the carbon dioxide in the product gas in the chemical equilibrium represented by the chemical equilibrium equation (4) reacts with the carbon dioxide absorbing material and decreases.
Now, if the carbon dioxide absorbing substance is represented by X, this reaction formula is
X + CO ₂ → (XCO ₂ ) (9)
It can be expressed as.
Incidentally, (XCO ₂ ) is a compound generated by the carbon dioxide absorbing material (X) absorbing carbon dioxide. For example, if the carbon dioxide absorbing material is CaO, (XCO ₂ ) is
CO ₂ + CaO → CaCO ₃ (10)
CaCO ₃ produced by the reaction formula of

  When carbon dioxide is reduced from the product gas by this reaction, the chemical equilibrium shown in the chemical equilibrium formula (4) proceeds to the right, that is, in the direction of generating carbon dioxide and hydrogen. The newly generated carbon dioxide further reacts with the carbon dioxide absorbing material and is absorbed. In this way, the reaction progresses sequentially, and the gasification rate of biomass is improved. Finally, the proportion of hydrogen in the gas is improved, and hydrogen can be produced efficiently, so that calcium sulfate is effectively converted into calcium sulfide. Converted.

  If a carbon dioxide-absorbing substance in an amount capable of absorbing all of the generated carbon dioxide is present in the reaction field in advance, the generated carbon dioxide is fully absorbed. By such a reaction, the gasification rate of biomass under the gasification conditions of the present invention can be improved to about 80%. However, if there is a carbon dioxide-absorbing substance in an amount that can absorb all of the carbon dioxide that is literally generated, the carbon dioxide will be completely absorbed, so that the carbonization of calcium sulfide may occur during cooling after gasification. Disappear.

As shown in the above reaction formula (9), the carbon dioxide-absorbing substance and carbon dioxide usually react one-on-one, and carbon dioxide is produced by oxidation of carbon atoms in biomass. In order not to completely absorb carbon, the number of moles of carbon dioxide absorbent added to the number of moles [C] of carbon in the biomass must be smaller than 1. Moreover, due to the carbonation of calcium sulfide in the reaction formula (7), for example the number of moles of gypsum [CaSO _4] moles of carbon in biomass for [C] ratio [C] / [CaSO _4] is In the case of 4, the amount of carbon dioxide absorbing material supplied to the reaction field is stoichiometrically the ratio of the number of moles of carbon dioxide absorbing material to the number of moles of carbon in the biomass in the reaction field [C]. It must be less than 0.5.

If the gasification rate of biomass is about 80%, the ratio of the number of moles of the carbon dioxide-absorbing substance to the number of moles of carbon [C] in the biomass is 0.4 or less. However, if the supply amount of carbon dioxide-absorbing substances is small, the gasification rate of biomass and the generation efficiency of hydrogen and carbon dioxide are reduced to about 50%, so the number of moles of carbon in the biomass [C] Thus, the ratio of the number of moles of the carbon dioxide absorbing material is 0.25 to 0.4. Of course, when the ratio [C] / [CaSO ₄ ] of the molar ratio [C] of the carbon in the biomass to the molar number [CaSO ₄ ] of gypsum is larger than _4, the molar ratio [C] of carbon in the biomass, The ratio of the number of moles of carbon dioxide absorbing material is increased.

  In addition, a carbon dioxide-absorbing substance in an amount capable of absorbing all of the generated carbon dioxide is pre-existing in the reaction field, and the biomass gasification rate is improved to about 80% based on carbon under the gasification conditions of the present embodiment. Then, the conversion of gypsum to calcium sulfide can be promoted by efficiently producing only hydrogen. In the case of the steam gasification reaction of biomass under such conditions, the carbon sulfide can be carbonated by supplying carbon dioxide from the outside during cooling after the steam gasification reaction.

  Thus, when supplying carbon dioxide from the outside, the ratio of the amount of carbon dioxide absorbing material that can absorb all the carbon dioxide produced by steam gasification of biomass is carbon dioxide relative to the number of moles [C] of carbon in biomass. The ratio of the number of moles of the absorbing material is preferably 0.5 or more, and more preferably in the range of 0.8 to 1.5. However, the ratio of the number of moles of carbon dioxide absorbing material to the number of moles of carbon in biomass [C] in order to take out hydrogen sulfide that becomes constant by adsorption and absorption by carbon dioxide absorbing material by carbonation. 0.8-1 is good. If hydrogen sulfide is made constant by the carbon dioxide-absorbing substance, the ratio of the number of moles of the carbon dioxide-absorbing substance to the number of moles of carbon [C] in the biomass is preferably 2 or more, more preferably 2-4.

In the gypsum treatment of the present invention, the carbon dioxide-absorbing substances used for coexisting with biomass and effectively gasifying biomass into hydrogen and carbon dioxide include calcium (Ca), magnesium (Mg), and strontium (Sr). , Barium (Ba), and iron (Fe) oxides (CaO, MgO, SrO, BaO, FeO, Fe ₂ O ₃ , Fe ₃ O ₄ ), and the same metal hydroxides (Ca (OH) ₂ , Mg (OH) ₂ , Sr (OH) ₂ , Ba (OH) ₂ , Fe (OH) ₂ , Fe (OH) ₃ ) are preferable.
Further, in the experiments by the present inventors, even when using biomass of shells such as oysters and scallops containing Ca content and having a characteristic porous three-dimensional structure as an oxide or hydroxide, It has been confirmed that it effectively absorbs carbon dioxide.

  These carbon dioxide-absorbing substances can be converted into carbon dioxide-absorbing substances by taking them out of the reaction field as carbonates and further decomposing the carbonates by heating to remove carbon dioxide. It can be used after returning to the reaction field.

  In this way, finally, the hydrogen sulfide generated by converting the calcium sulfate of this embodiment into calcium carbonate is effectively recovered. After steam gasification, after cooling at a temperature of 400 ° C or less to complete carbonation, it is sent to a dust collector consisting of a cyclone or a bag filter (a filter that removes specific substances with a filter cloth) to separate solids and gases. As a gas, hydrogen sulfide is sent to the hydrogen sulfide recovery section. Solid calcium oxide is stored in a hopper or the like.

  The embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and various other modifications are possible without departing from the essence thereof. Needless to say. For example, the above explanation has mainly taken woody biomass such as quercus and cedar, but other seaweeds and seafood, or organic waste after using these, are exactly the same. Of course, these biomasses can also be used as starting materials coexisting in the gypsum treatment of the present invention.

Examples of the above-described embodiment will be described below. Needless to say, the present invention is not limited to these examples.
[Gypsum processing apparatus in Examples]
FIG. 1 is a block diagram of a gypsum treatment apparatus based on a batch steam gasifier having an autoclave (manufactured by Inconel). Gypsum treatment was performed using this apparatus. The configuration is as follows. The autoclave 1 is a pressure kettle for mixing gypsum A, biomass B, and water vapor C and reacting them by heating under pressure. Further, carbon dioxide absorbing material D is supplied as necessary. Before the experiment, nitrogen is supplied to the autoclave 1 through the valve 2 to purge oxygen.

  A heating device 4 incorporating a heater for heating is disposed on the outer periphery of the autoclave 1. The temperature and pressure in the autoclave 1 can always be measured with the thermometer 5 and the pressure gauge 6. The autoclave 1 in FIG. 1 is configured to perform a gasification process by a high-temperature reaction of biomass and a process of converting gypsum into calcium sulfide, but the autoclave 1 cools the gas and converts calcium sulfide into calcium carbonate and hydrogen sulfide. The structure which performs the process to perform may be added. Further, when the carbon dioxide absorbing material is supplied, the carbon dioxide absorbing treatment is performed. The generated gas generated in the autoclave 1 is subjected to a cooling process 12 and sent to a dust collector 14 to be separated into calcium carbonate and hydrogen sulfide. The hydrogen sulfide is sent to a gas bag 9 through a pipe 7 and an on-off valve 8. Collected. The gas bag 9 is covered with a sealed container 10. The volume of hydrogen sulfide causes a volume change when the gas bag 9 expands, and this volume is measured by the gas meter 11. On the other hand, calcium carbonate is solid and is stored in the hopper 13.

[Conditions]
The implementation conditions are as follows. Crushed gypsum (0.3 g, average particle size 10 μm), Quercus cedar or cedar (average particle size 500 μm each) is used for biomass, and Ca (OH) ₂ (particle size about 10 μm) is used as the carbon dioxide absorbing material. It was. Confirmation of the chemical-physical change of gypsum was performed using an X-ray diffraction method and an atomic absorption analysis method. The amount of hydrogen sulfide produced was measured with a detector tube.

[Example 1]
Based on the configuration shown in FIG. In the autoclave 1, the ratio ([C] / [CaSO ₄ ]) of the number of moles [C] of carbon in the quercus material to the number of moles [CaSO ₄ ] of the main component CaSO ₄ of gypsum is 4, The molar ratio of water vapor to the number of moles [C] ([H ₂ O] / [C]) was set to 6 to introduce gypsum, quercus and water. The pressure is fixed at 0.6 MPa, the temperature is set to 700 ° C. and 750 ° C., respectively, and steam gasification is performed for 10 minutes (the biomass gasification is completely completed), and then air-cooling to room temperature is performed for gypsum treatment. Then, the dependency of the steam gasification temperature was measured.

[result]
As a result of analyzing the gypsum treated by steam gasification at 700 ° C., it was 90.5 wt% calcium carbonate, 3.5 wt% calcium sulfide, 4.4 wt% calcium sulfate, and 1.6 wt% in others. As a result of analyzing the gypsum treated by steam gasification at 750 ° C., it was 93.5 wt% calcium carbonate, 3.0 wt% calcium sulfide, 2.1 wt% calcium sulfate, and 1.4 wt% in others. Hydrogen sulfide commensurate with this carbonation reaction was confirmed.

[Evaluation]
That is, conversion from calcium sulfate to calcium sulfide and carbonation of calcium sulfide were effectively performed by steam gasification of biomass at 700 ° C. The results also revealed that when the steam gasification temperature of biomass was increased to 750 ° C., the conversion from calcium sulfate to calcium sulfide and the carbonation of calcium sulfate were further increased.

[Example 2]
The same procedure as in Example 1 was performed with the apparatus shown in FIG. In the autoclave 1, the molar ratio [C] of carbon in the cedar wood to the number of moles of gypsum [CaSO ₄ ] ([C] / [CaSO ₄ ]) is 4 and the number of moles of carbon in the cedar wood [C] The ratio of the number of moles of water vapor [H ₂ O] to [H ₂ O] / [C] is 4, and the carbon dioxide absorbing material Ca (OH) added to the number of moles of carbon [C] in cedar Gypsum, cedar, Ca (OH) ₂ and water were introduced so that the molar ratio [Ca] of ₂ was 1. The pressure is fixed at 0.6 MPa, the temperature is fixed at 750 ° C., and steam gasification is performed for 10 minutes (the biomass gasification is completely completed), and then the number of moles is twice the number of moles of gypsum [CaSO ₄ ]. Carbon dioxide was added and air-cooled to room temperature to perform gypsum treatment, and the dependency of the steam gasification temperature was measured.

[result]
As a result of analyzing the gypsum treated by adding the carbon dioxide-absorbing substance Ca (OH) ₂ and steaming at 750 ° C., calcium carbonate 97.5 wt%, calcium sulfide 1.7 wt%, calcium sulfate 0.4 wt%, and others 0 It was 4 wt%. Hydrogen sulfide commensurate with this carbonation reaction was confirmed.

[Evaluation]
The coexistence of carbon dioxide-absorbing substances promotes the conversion of calcium sulfate to calcium sulfide, and if sufficient carbon dioxide is supplied, the carbonization of calcium sulfide is also effectively performed, resulting in a further increase in calcium sulfate carbonation. It became clear from.

FIG. 1 is a block diagram of a gypsum processing apparatus to which the gypsum processing method of the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Autoclave 2 ... Valve 3 ... Valve 4 ... Heating device 5 ... Thermometer 6 ... Pressure gauge 7 ... Pipe 8 ... On-off valve 9 ... Gas bag 10 ... Sealed container 12 ... Cooling process 13 ... Hopper 14 ... Dust collector

Claims (9)

Supply water vapor to the mixture of gypsum and biomass under the conditions of a pressure of less than 1.5 MPa and a temperature of 650 ° C. to 800 ° C.
This reaction gasifies the biomass into a gas containing hydrogen, carbon monoxide, and carbon dioxide,
The gypsum is converted into calcium sulfide by the hydrogen generated by the gasification and the carbon monoxide,
A method for treating gypsum, wherein the calcium sulfide is cooled to a temperature of 400 ° C. or less together with water vapor and the gas component containing carbon dioxide, and converted into calcium carbonate and hydrogen sulfide. In the processing method of gypsum according to claim 1,
The mixture of gypsum and biomass is composed of one or more oxides or hydroxides selected from calcium (Ca), magnesium (Mg), strontium (Sr), barium (Ba), and iron (Fe). Add a carbon dioxide-absorbing substance to make it coexist and react
The biomass is gasified while absorbing a part of the carbon dioxide produced from the biomass with the carbon dioxide-absorbing substance. In the processing method of gypsum according to claim 2,
The method for treating gypsum, wherein the carbon dioxide is added during the cooling to convert the calcium sulfide into the calcium carbonate. In the processing method of gypsum according to one selected from Claims 1 thru / or 3,
A method for treating gypsum, wherein the mixture containing calcium carbonate and hydrogen sulfide is guided to a dust collector and separated into mainly solid calcium carbonate and gaseous hydrogen sulfide. In the processing method of gypsum according to one selected from Claims 1 to 4,
The method for treating gypsum, wherein the reaction is performed under conditions of a pressure of less than 1.0 MPa and a temperature of 700 ° C to 800 ° C. In the processing method of gypsum according to one selected from Claims 2 to 5,
The method for treating gypsum, wherein the carbon dioxide-absorbing substance is taken out as a carbonate and then reused by removing the carbon dioxide by heating. In the processing method of gypsum according to claim 1 selected from Claims 1, 2, and 3,
In the reaction, the biomass is supplied so that the ratio [C] / [CaSO ₄ ] of the number of moles [C] of carbon in the biomass to the number of moles [CaSO ₄ ] of the gypsum is 4 or more. A method for treating gypsum characterized by the above. In the processing method of gypsum according to claim 1 selected from Claims 1, 2, and 3,
The steam is supplied so that the ratio [H ₂ O] / [C] of the number of moles [H ₂ O] of the steam to the number of moles [C] of carbon of the biomass in the reaction is 2 or more. Gypsum processing method. In the processing method of gypsum according to claim 2 or 3,
In the reaction, the ratio of the number of moles of the carbon dioxide-absorbing substance added to the number of moles of carbon [C] in the biomass is set to be less than 0.5, and the reaction does not completely absorb the generated carbon dioxide. A method for treating gypsum as a feature.

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