JP2009161391A - Carbon dioxide gas circulation type limestone burning furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon dioxide gas circulation type limestone burning furnace which can recover a large amount of carbon dioxide gas with high purity which is generated by the decomposition of limestone and discharged from a limestone burning furnace when limestone is burned, and which enables utilization of the carbon dioxide gas as a liquefied carbon dioxide and underground fixing treatment thereof. <P>SOLUTION: The carbon dioxide gas generated by the decomposition of limestone is circulated using a carbon dioxide gas circulating fan 106. The circulated carbon dioxide gas is heated to a burning temperature without incorporation of combustion gas with an electrical heater 107 or a radiant tube heater, whereby the temperature and the amount of heat required for burning limestone are ensured to burn limestone. The carbon dioxide gas 4 with high purity generated at this time is bled from a burning furnace outlet piping, stored, and treated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

      At the lime factory, a large amount of carbon dioxide gas is released into the atmosphere when limestone is fired, and there is concern about adverse effects on global warming. To prevent this, technology development for collecting carbon dioxide gas has been underway. In order to recover carbon dioxide gas discharged by limestone firing at a high concentration, coke is used as a calcined fuel and carbon dioxide gas is recovered by burning with oxygen, or limestone is indirectly heated to produce carbon dioxide gas. A collection method has been proposed.

      As a method of recovering carbon dioxide gas generated during limestone firing, if coke mixed in limestone at a constant rate is burned with oxygen, no gas other than carbon dioxide gas is generated, so the gas discharged from the furnace is Only carbon dioxide from combustion and carbon dioxide from decomposition of limestone are used, but if limestone and coke are mixed uniformly and not burned uniformly, excess or deficiency of oxygen occurs or heat is uniformly distributed to limestone due to a lack of heat medium. There is a problem that it is unavoidable that limestone is unevenly burned.

    In addition, the amount of heat transferred to the limestone in the indirect heating limestone furnace is proportional to the heat transfer area, so the production volume is also proportional to the heat transfer area, but the heat transfer area is the surface area of the furnace body itself, There is a limit to the heat transfer area. Therefore, the production amount per one limestone firing furnace is at most several tons per day, and it is difficult to scale up to a practical scale of several hundred tons, and it is difficult to scale up, so there is little merit of scale and there is a difficulty in economic efficiency.

      In order to burn limestone, at least limestone must be heated to 850 ° C. or higher, and heat corresponding to the heat of decomposition of limestone needs to be given to limestone. It is common to use fossil fuels that tend to generate hot gases. Since air is used to burn this fuel, nitrogen in the air remains in the combustion gas, and carbon dioxide gas generated by combustion, water vapor and carbon dioxide gas generated by limestone decomposition are mixed, and the concentration of carbon dioxide in the total exhaust gas Is less than 30%, and it is difficult to effectively use the generated carbon dioxide gas, except for one part, and most of it is released into the atmosphere, contributing to global warming.

      The invention of claim 1 for solving this problem uses carbon dioxide gas generated during firing as a heating medium for limestone firing, is circulated using a circulation gas fan, and is necessary for firing with an electric heater or a radiant tube heater. By heating and raising the temperature of the carbon dioxide gas to a temperature, it is possible to eliminate mixing of gases other than the generated carbon dioxide gas and recover the generated carbon dioxide gas as high-purity carbon dioxide gas.

      According to the invention of claim 2, the circulating gas has a temperature difference between the inlet side and the outlet side of the packed bed, so that the limestone on the outlet side takes longer to decompose than the inlet side, and the production efficiency tends to be reduced. In order to do this, coke is mixed in limestone in advance and a partition is placed at both the inlet and outlet of the circulating gas to divide it into upper and lower parts. The coke in the limestone is combusted at the lower part of the calcining zone to prevent the circulation gas temperature from decreasing and to compensate for the insufficient heat quantity, thereby uniforming the limestone calcining.

      In the invention of claim 3, the product after baking is heated to about 900 ° C. and cannot be transported and stored as it is, so it is necessary to cool it to near room temperature. The product is cut out with a quantitative discharger at high temperature, discharged through a sealing discharge valve so that carbon dioxide in the furnace does not leak into the atmosphere, and then cooled with a separate product cooler. Thus, the temperature is set to 100 ° C. or less which is easy to handle.

      Since high purity carbon dioxide gas can be recovered by the present invention, it can be compressed and cooled to obtain liquefied carbon dioxide gas that is commercially available and has high added value, and can be compressed and buried in the ground or dumped into the sea. Can be expected to help prevent global warming.

Embodiments relating to the limestone firing furnace of the present invention will be described.
This embodiment is described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

      FIG. 1 shows the components of the carbon dioxide circulating limestone firing furnace of the present invention and the overall flow of limestone and gas. Table 1 shows the amount of heat of each part in limestone firing when the production amount is 100 T / D. Shows the balance of pressure and quantity. The limestone mixed with coke corresponding to 20% of the calorie decomposition heat quantity from the upper part of the limestone firing furnace 100 is supplied to the packed bed through the supply device 103 having a sealing property and is heated to 1100 ° C. by the electric heater 107. The upper firing zone 101 is baked by about 80% by carbon dioxide gas, and further descends to obtain the combustion heat of coke in the lower firing zone 102 to complete the firing. The product is discharged as a product by the quantitative discharger 104 and has a sealing discharge valve 105. After that, it is discharged outside the furnace. The generated carbon dioxide in the circulating carbon dioxide at the lime firing furnace outlet is extracted and cooled and stored while being controlled by the pressure regulating valve 108 provided in the extraction pipe so that the packed bed outlet pressure becomes plus or minus zero. The circulating carbon dioxide gas extracted from the generated carbon dioxide gas is boosted by the circulating gas fan 106, heated by the electric heater 107, flows into the limestone baking furnace 100, and burns limestone while passing through the packed bed.

      Table 1 shows the material, temperature, pressure, flow rate, and sensible heat at the location shown in FIG.

    By collecting a high concentration of carbon dioxide gas discharged in a large amount during limestone firing, post-treatment is facilitated and effective as a global warming countermeasure.

It is a flowchart which shows the flow with the lime furnace whole structure apparatus.

Explanation of symbols

100 Limestone firing furnace
101 Upper firing zone
102 Lower firing zone
103 Supply valve
104 metering dispenser
105 Discharge valve
106 Circulating gas fan
107 electric heater
108 Pressure regulating valve

Claims (3)

    In a carbon dioxide circulating limestone firing furnace in which limestone is fired by passing carbon dioxide through a limestone packed bed filled in two opposing lattice brick walls, 700 ° C. to 800 ° C. by pyrolysis of limestone and preheating of limestone. The carbon dioxide gas at the outlet of the limestone firing furnace whose temperature has decreased to ℃ is circulated using a carbon dioxide circulation fan, and the temperature is raised to about 1100 ℃, which is the limestone firing temperature without generating gas with an electric heater or radiant tube heater. Circulating and passing through the packed bed, the carbon dioxide gas newly generated by the decomposition of limestone is extracted from the furnace outlet piping and recovered as high-purity carbon dioxide gas while controlling the pressure at the lattice brick outlet to atmospheric pressure. The carbon dioxide circulating limestone firing furnace according to claim 1, wherein:       In a limestone firing furnace that replenishes the amount of heat when the decomposition of limestone is not completed by mixing coke in an amount that can generate heat equivalent to 10% to 20% of the amount of heat required for decomposition of limestone, The partition is provided in the carbon dioxide gas inlet / outlet space of the calcining zone, divided into upper and lower portions, oxygen corresponding to the amount of coke is introduced only into the lower circulating carbon dioxide, and the coke is combusted at the lower portion of the calcining zone. Carbon dioxide circulating limestone firing furnace Products that have been baked are cut out with a quantitative discharger at a high temperature, discharged to the outside of the furnace through a discharge valve that can shut off carbon dioxide in the furnace and outside air, and cooled to 100 ° C or lower with a separate cooler. The carbon dioxide circulating limestone firing furnace according to claim 1, wherein the furnace is stored in a storage tank.

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