JP2006314924A - Method for producing shell adsorbent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a shell absorbent by which energy consumption is reduced, though much energy is consumed when a shell is fired at high temperature, which adversely affect economic effect, in the case of producing a shell adsorbent. <P>SOLUTION: The method for producing the shell adsorbent by firing the shell is characterized in that the shell is fired in a poor oxidizing atmosphere. Since the shell is fired in the poor oxidizing atmosphere, the firing temperature can be lowered. As a result, the energy consumption can be reduced and the economic effect can be gained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a shell adsorbent, particularly a oyster shell adsorbent.

Although 250,000 tons of oysters are produced annually throughout Japan, specific measures for treating oyster shells that are produced in large quantities each year are becoming a problem.
Since shells contain a lot of calcium, some oyster shells are used for livestock feed and soil conditioners, and are also used for roadbed materials, fish reefs, fertilizers and so on. However, even these treatment methods cannot be treated, and at present, most of the waste is left untreated as industrial waste in farms.

  Oyster shells contain calcium carbonate, a natural resource, as a main ingredient, and as one of the reuses that make use of abundant calcium, they also cause eutrophication of lakes and marshes. Paying attention to phosphorus, it is considered that oyster shells can be effectively used as a remover of phosphorus from domestic wastewater and sewage or as a phosphorus recovery agent.

Under such a viewpoint, phosphate ion adsorption filter media using oyster shells have been developed together with Kanuma soil, activated alumina, iron hydroxide and the like having a large amount of phosphorus adsorption (see, for example, Patent Document 1).
However, when manufacturing the adsorbent filter medium, firing at a high temperature of 800 ° C. to 900 ° C. is in progress, which is problematic from the viewpoint of energy consumption.
JP 11-197500 A

  The present invention was made by finding that firing a shell in a poor oxidizing atmosphere prevents a decrease in the phosphate ion adsorption amount of the fired shell, preventing a decrease in the phosphate ion adsorption amount of the fired shell, and The purpose is to reduce the energy used in firing.

Invention of Claim 1 is a manufacturing method of a shell adsorbent characterized by baking in a poor oxidation atmosphere in a method of baking a shell and manufacturing a shell adsorbent.
The invention according to claim 2 is the method for producing a shell adsorbent according to claim 1, wherein in the shell firing, a poor oxidation atmosphere is generated by an inert gas.
The invention according to claim 3 is the method for producing a shell adsorbent according to claim 1 or 2, wherein the flow rate of the inert gas is 50 ml / min or more and 500 ml / min or less. .
Invention of Claim 4 is a manufacturing method of the shell adsorbent in any one of Claim 1 thru | or 3 characterized by adding carbon.

The method for producing a shell adsorbent of the present invention can prevent a decrease in the amount of phosphate ions adsorbed by the fired shell by firing the shell in a poor oxidizing atmosphere.
In addition, the continuous supply of inert gas promotes the removal of carbon dioxide gas generated during shell firing and the generation of calcium oxide, and the calorific value is balanced by limiting the flow rate of the inert gas. The firing temperature can be further reduced, and the process cost in bulk processing can be reduced.
Further, by using carbon, gas body adsorption can be achieved.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the best mode for carrying out the invention.

The shells referred to in the present invention include shells such as oysters, scallops, idiots, blue goats, clams, clams, shijimi, akoya, mussels, red oysters, scallops, abalone, clams, preferably oysters. It is a shell.
The oyster shell is composed of a white chalk structure and a translucent leaf-like structure, and the fine lattice constituting the chalk structure increases the surface area and has a structure that is easy to adhere and stick.
In addition, when the oyster shell is used as an adsorbent with such a structure remaining, microorganisms are likely to settle. It becomes possible to purify the sewage.
The choke structure is a structure in which many lattice structures are held and moisture is held in the lattice, and the leaf structure has a structure in which a number of thin leaves are stacked.

By firing the shell in a poor oxidizing atmosphere, the reason is not clear, but for example, when the amount of phosphate ion adsorption is used as an index, in the production of a fired shell capable of adsorbing the same amount of phosphate ion, The firing temperature can be lowered.
The poor oxidation atmosphere referred to in the present invention refers to an atmosphere that does not contain oxygen or that contains 5% or less, and does not necessarily mean an atmosphere that is positively reducing.
When the oxygen content exceeds 5%, there arises a problem that the amount of phosphate ion adsorption by the fired shell (particularly oyster shell) is reduced.

In the present invention, firing is performed in a poor oxidation atmosphere, but vacuum processing or electromagnetic heat treatment may be performed as pretreatment for firing.
Pretreatment removes moisture in the oyster shell chalk structure to prevent heat loss used to evaporate moisture, further expands the uneven structure on the surface of the oyster shell, and changes calcium carbonate to calcium oxide. This is because it is considered that the influence of moisture cannot be considered.

  The inert gas referred to in the present invention refers to a gas that is chemically inert, and usually refers to rare gas elements (helium, neon, argon, xenon, radon), but nitrogen gas is preferred from an economic viewpoint.

The flow rate of the inert gas used is not less than 50 ml / min and not more than 500 ml / min per 2800 cm ³ of the baking apparatus. If the flow rate is 50 ml / min or less, there will be a problem that the amount of phosphate ions adsorbed on the shell will decrease, and if it is 500 ml / min or more, the amount of heat carried away by the inert gas will increase, resulting in poor thermal efficiency. Because it occurs.
In addition, when supplying an inert gas, it is preferable to preheat.

Carbon can be used for firing. The carbon source may be charcoal, paper charcoal, bamboo charcoal, or the like, or carbon from an organic substance attached to the shell during firing.
The form is not particularly limited, but it is preferable to use it in powder form from the viewpoint of operation in firing.
Although there is no limitation about the usage-amount, it should just be 10% or more with respect to the shell weight.

By using carbon, in the firing furnace
CaCO ₃ + C → CaO + 2CO
Since carbon monoxide gas reacts with oxygen, a poor oxidation atmosphere is formed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to an Example.

(Phosphorus collection (rate) measurement method)
The amount of phosphorus collected is measured by the molybdenum blue method.
The molybdenum blue method will be described below.
Add 2.5 mL of concentrated sulfuric acid to 500 mL of water to prepare 2.5 M sulfuric acid.
Next, 20 g of ammonium molybdate is dissolved in 500 mL of water to prepare an ammonium molybdate solution, 1.76 g of ascorbic acid is dissolved in 100 mL of water, and a 0.1 M ascorbic acid solution is prepared. Prepared in a ratio of 2.5 M sulfuric acid: ammonium molybdate solution: 0.1 M ascorbic acid solution = 10: 3: 6, and this solution is used as a mixed reagent.
7.165 g of potassium dihydrogen phosphate is precisely weighed and dissolved in 1 L of water to prepare a phosphate ion standard solution having a concentration of 5000 ppm.
0.5 g of a sample for measuring the amount collected is put into a centrifuge tube, and 10 mL of a solution prepared by diluting the prepared phosphate ion standard solution with pure water to 50 ppm is added thereto.
After standing for 10 minutes, centrifuge at 2000 rpm for 10 minutes in a centrifuge.
After separation, collect 2 mL of the supernatant from the solution in another centrifuge tube, add 2 mL of the prepared mixed reagent and 8 mL of pure water in this order, and shake well.
After standing for 15 minutes, the absorbance at a wavelength of 880 nm is measured with an ultraviolet-visible spectrophotometer (HITACHI U-3500).
Further, 2 mL of phosphate ion standard solution prepared to 50 ppm, 2 mL of mixed reagent, and 8 mL of pure water are mixed, and the absorbance of the standard solution is measured.
The blank test is performed with 9 mL of pure water and 1 mL of mixed reagent.
The collection rate is calculated from the values obtained by these operations.

Example 1
Oyster shells were fired under a nitrogen atmosphere.
The flow rate of nitrogen was 200 mL / min, and an annular electric furnace was used for firing at a heating temperature of 1 hour and a firing time of 1 hour at a firing temperature of 600 ° C. to 800 ° C. at 100 ° C. intervals.
After firing, the phosphorus collection rate was measured by the phosphomolybdenum blue method.
The results are shown in Table 1.

(Comparative Example 1)
In the atmosphere, as in Example 1, using an annular electric furnace, firing was performed at 100 ° C. intervals up to a firing temperature of 200 ° C. to 800 ° C. with a heating time of 1 hour and a firing time of 1 hour.
After firing, the phosphorus collection rate was measured by the phosphomolybdenum blue method.
The results are shown in Table 1.

なお、表中○はリン捕集率７５％以上、△はリン捕集率５０〜７５％、×はリン捕集率５０％未満であることを示す。

In the table, ○ indicates that the phosphorus collection rate is 75% or more, Δ indicates that the phosphorus collection rate is 50 to 75%, and x indicates that the phosphorus collection rate is less than 50%.

  As is clear from Table 1, firing is generally performed at a high temperature (800 ° C. to 900 ° C.), but since the phosphorus collection rate is improved by firing in a poor oxidizing atmosphere, the firing temperature is set to be low. Can be reduced, and energy consumption can be reduced.

(Example 2)
Bamboo charcoal was mixed with oyster shells at different molar ratios and then fired. The oyster shell was mixed with bamboo charcoal at the following ratio, and then fired in an electric muffle furnace (ADVANTEC KM-160) with a heating time of 1 hour and a firing time of 1 hour. At a molar ratio of 1, oyster shells of 1.009 g were mixed with 0.12 g of bamboo charcoal, at a molar ratio of 2.09 g of oyster shells of 0.24 g of bamboo charcoal, and at a molar ratio of 0.39 g of bamboo charcoal was mixed with 1.009 g of oyster shells.
The firing temperature was 800 ° C.
0.5 g each of bamboo charcoal and calcined oyster shells with different molar ratios were collected in a centrifuge tube, and 10 mL of a solution prepared by diluting the prepared phosphate ion standard solution with pure water to a concentration of 2000 ppm was added thereto. Thereafter, the absorbance was measured by the molybdenum blue method to determine the phosphorus collection rate.
Table 2 shows the phosphorus collection rate of the fired oyster shell.

(Comparative Example 2)
In Example 2, the bamboo charcoal was not used as Comparative Example 2, and the phosphorus collection rate is shown in Table 2.

  As is apparent from Table 2, it is recognized that the phosphorus collection rate is improved when bamboo charcoal is used. Since bamboo charcoal can be used as a poor oxidation atmosphere, it is also conceivable to lower the firing temperature by firing in a poor oxidation atmosphere.

  The method for producing a shell adsorbent in the present invention can be applied to the waste recycling industry.

Claims (4)

In a method of firing a shell and producing a shell adsorbent,
It is characterized by firing in a poor oxidation atmosphere.
A method for producing a shell adsorbent. In shell shell firing, it is characterized by producing a poor oxidation atmosphere with an inert gas,
The method for producing a shell adsorbent according to claim 1. The inert gas flow rate is 50 ml / min or more and 500 ml / min or less,
The method for producing a shell adsorbent according to claim 1 or 2. It is characterized by adding carbon,
The method for producing a shell adsorbent according to any one of claims 1 to 3.