KR19980073418A - Indirect heated fluidized bed apparatus with interpolated heating tubes for oil contaminated soil restoration - Google Patents

Abstract

A heated apparatus for restoring oil contaminated soil, comprising: (1) a fluidized bed thermal desorption system for desorbing oil in an oil contaminated soil, and (2) a low temperature heat equipped with an oxidation catalyst for combusting the oil desorbed in the fluidized bed thermal desorption system. Fracture system, (3) located between the fluidized bed thermal desorption system and the low temperature thermal destruction system to form a multi-stage structure with these systems (1, 2), and the heat of combustion of the desorbed oil content generated in the thermal destruction system Oil contaminated soil recovery consisting of a heating tube system for providing a heat source of the fluidized bed thermal desorption system, and (4) a circulation system for allowing gases in and out of the systems (1, 2, 3) to circulate organically with one another. An indirect heated fluidized bed apparatus with interpolated heating tubes for a method and a method for recovering soil contaminated with oil using the apparatus are disclosed. have.

By using an indirect heated fluidized bed apparatus according to the present invention, it is possible to maximize the use of energy to restore oil contaminated soil with high efficiency.

Description

Indirect heated fluidized bed apparatus with interpolated heating tubes for oil contaminated soil restoration

The present invention is directed to an indirect heated fluidized bed apparatus in which a heat pipe is interpolated that can be used to recover soil contaminated with oil.

Recently, the soil around gas stations has been severely damaged by petroleum or chemical products, and the contamination of soil by petroleum or chemical products has been shown in the deep environmental report of the Chosun Ilbo dated August 8, 1996. As shown, oil leaks from about 36.1% of the 529 underground storage tanks in 175 gas stations in Korea, and in particular, 5 samples of the soil around 5 out of 6 gas tanks 10 to 40 years after they are buried. It is reported to be contaminated with oil and heavy oil components, showing its seriousness. Moreover, the oils in these contaminated soils contain more than 150 toxic substances, including carcinogens such as benzene and toluene, which cause leukemia and various diseases caused by contaminated groundwater. Will result.

Remediation of soils contaminated by these petroleum products is a technology to reduce the contaminated soil and groundwater to the natural state through the management treatment system, and active treatment through research and field application in advanced countries including the United States. Is in progress. Contaminated soil remediation techniques are classified into i) in-situ systems and ii) ex-situ systems. In-situ restoration systems are technologies that remove and disintegrate contaminants in situ without digging and moving contaminated soil. This technology is being actively researched and applied to perform biological recovery in situ, along with vapor extraction restoration techniques that are effective in removing harmful volatile contaminants. Ex-situ system is a system that excavates contaminated soil, transfers it to a new place where contaminated soil treatment facilities and external blocking facilities are installed, and then restores the restored soil to the original excavation site. Physical, chemical and biological methods can all be used in this technique.

On the other hand, considering the location environment around the oil reservoir at the gas station, which is currently a problem, and comparing the main technologies applicable to the contaminated soil restoration developed in developed countries, etc., it is possible to deduce to what extent it is suitable. First, take a look at the location environment around domestic gas stations.

First, most of the old gas stations that are to be restored are concentrated in urban areas or in places with heavy traffic, so working environments such as facilities for soil restoration can interfere with the flow of vehicles to and from nearby residents. Is likely to trigger,

Secondly, most gas stations around the city center are expensive, and from the land owner's point of view, land cannot be left idle for long periods to restore soil.

Third, soils contaminated with petroleum products have various types of pollutants, so it is difficult to treat contaminated soils using only one technique.

For the reasons described above, the soil restoration methods of the in-situ system have many limitations for application to contaminated soil sites around domestic underground storage tanks despite the many advantages they have inherent. Therefore, heat treatment, which has the effect of treating the soil contaminated with a wide variety of contaminants in a short time and completely, has been developed to restore contaminated soil to date, especially when compared with biological treatment or other physical / chemical treatments. Among the methods, the effect is considered to be the most proven technique.

Incineration, which is a representative method among these heat treatment methods, can be combined with toxic removal and volume reduction, but it is expensive to install, and attention should be paid to solid residue treatment and exhaust gas treatment. That is, incineration is not only possible to control the amount of combustion gas generated when raising the temperature of the contaminated soil to the point where the pollutant is burned, but also generates sulfur oxides and nitrogen oxides at high temperatures, Even the heavy metals contained there are problems such as the result of moving from the soil to the atmosphere.

The thermal desorption method developed as a method for solving the problems of the heat treatment method is a method of desorbing contaminants present in soil pores or between soil particles by applying thermal energy to contaminated soil from the liquid phase or solid phase to the gas phase. The thermal desorption method is divided into direct heating method and indirect heating method according to the heat supply method. The direct heating method uses incomplete combustion heat by supplying a limited amount of oxygen inside the thermal desorber, and the indirect heating method is thermal desorption by excluding combustion reaction. It is a method using only the heat source of the heating body interpolated in the machine. Such an indirect heating thermal desorption system can significantly reduce the amount of waste gas generated to bring about the effect of reducing the processing scale of the processing gas. However, the technologies developed so far include a method of interpolating a high temperature screw thread in which hot oil circulates inside the thermal desorber (LT ³ Technology, PT Kostecki and EJ Calabrese, Petroleum Contaminated Soils: Remediation Techniques Environmental Fate Risk Assessment, Vol. 1) , pp 201-209, Lewis Publisherss, Inc., Chelsea, Michigan, 1989; see EPA Report, Low Temperature Thermal Treatment (LT ³ ) Technologyy, EPA / 540 / AR-92 / 019, Dec. 1992). The method is problematic in that the apparatus used is complex and the processing scale is limited due to limitations in heat transfer efficiency.

Accordingly, the present inventors have made a thorough study to overcome the limitations of such conventional methods.

SUMMARY OF THE INVENTION An object of the present invention is a heated device for restoring oil contaminated soil, comprising: (1) a fluidized bed thermal desorption system, (2) a low temperature thermal destruction system equipped with an oxidation catalyst, (3) the fluidized bed thermal desorption system and the low temperature thermal destruction system A heating tube system disposed between and forming a multi-stage structure, and (4) a heating system for recovering oil-contaminated soils, comprising a circulation system for allowing gases in and out of the systems (1, 2, 3) to circulate organically with each other. It is to provide an indirect heated fluidized bed device in which a tube is interpolated.

It is another object of the present invention to provide a heating method for restoring an oil contaminated soil, comprising: (1) continuously desorbing oil-contaminated soil in a fluidized bed heat desorption system, and (2) removing the desorbed oil content in a heat destruction system. Decomposing and removing, (3) providing combustion heat of the desorbed oil content to the heat source of the fluidized bed desorption system by the heating tube system, and (4) in and out of the systems (1, 2, 3) It is to provide an oil-contaminated soil restoration method comprising the step of allowing the gases to circulate organically with each other.

Another object of the present invention is to provide a method for minimizing the waste gas generated when restoring soil contaminated with oil.

It is another object of the present invention to provide a method which can improve the energy utilization in restoring soil contaminated with oil.

1 is a schematic diagram of an indirect heated fluidized bed apparatus with interposed heating tubes for oil contaminated soil restoration according to the present invention;

Figure 2 is a graph showing the oil content of the contaminated soil in the thermal desorption system over time when purifying the soil contaminated with 10% diesel oil in the fluidized bed thermal desorption system of the present invention.

Explanation of symbols on the main parts of the drawing

1: contaminated soil supply pipe

2: Purified soil discharge pipe

3: cyclone

4: desorption gas discharge pipe

5: fluidized gas supply pipe

6: waste gas discharge pipe

7: oxygen supplement supply pipe

8: desorption gas supply pipe

The apparatus for restoring the oil-contaminated soil of the present invention operates the thermal desorption system at a temperature below 500 ° C. in which the contaminated oil is not burned and only the desorption process proceeds, and the desorbed oil is burned at a low temperature using an oxidation catalyst. As a high-efficiency device that transfers most of the thermal energy back to the thermal desorption system by a heating tube, the thermal desorption system uses a fluidized bed to maximize the heat transfer efficiency between the systems and mass transfer from the solid phase to the gas phase.

The system of the present invention is a multistage contaminated soil heat treatment system in which a heat destruction system consisting of a fluidized bed heat desorption system and a honeycomb oxidation catalyst is connected by a heating tube in order to achieve high energy efficiency. In this system, the desorption energy required for desorption of oil present in contaminated soil is constructed in such a way that the heat of combustion generated by the desorbed oil content is burned in the heat destruction system is indirectly transferred to the heat desorption system with high efficiency by a heating tube without special heat transport mechanism. In addition, the thermal destruction system is operated at a temperature much lower than the combustion temperature of oil (about 300 ° C.), and has a characteristic of fundamentally suppressing the generation of sulfur oxides and nitrogen oxides (NOx) generated during high temperature operation.

The system of the present invention consists of the following components: (1) fluidized bed thermal desorption system, (2) low temperature thermal destruction system, (3) heating tube system, and (4) gas circulation system.

The fluidized bed used in the fluidized bed thermal desorption system refers to a state in which solid particles are suspended by a liquid or a gas. In this state, the film resistance of mass transfer and heat transfer between a solid phase and a liquid phase or a gaseous phase is so small that from the external system into the fluidized bed. It is possible to increase heat transfer and mass transfer from the solid phase to the liquid or gas phase more than 10 times than the stationary phase. Accordingly, in the present invention, by using the fluidized bed having such an advantage, by thermal desorption of contaminants in the fluidized bed, heat transfer into the fluidized bed required for thermal desorption and mass transfer from the contaminated soil to the gas phase are made possible.

In thermal destruction systems, it is possible to combust oil volatile organic compounds (VOCs) desorbed in a fluidized bed at low temperatures using an oxidation catalyst. In the present invention, a platinum-based honeycomb catalyst was used.

The heating tube system of the present invention uses an indirect heating method, the heating tube has a large amount of heat transport capacity, uniformity of temperature distribution, light and simple structure and fast response, as well as the heat transfer amount and system temperature by incorporating non-condensable gas It has many advantages, such as being able to control it. The principle of operation of the heating tube is extremely simple. In other words, when a suitable amount of working fluid is injected into a vacuum-sealed container and heated with a high temperature heating medium on one side, the working fluid evaporates and is moved by a pressure difference to the other side. By condensing and circulating to the evaporation unit where the working fluid has evaporated, it is a device that does not require an external heat transport mechanism by transferring heat of a high temperature heat medium to a low temperature medium through latent heat of evaporation as a medium. In the present invention, by using such a heating tube, it is possible to smoothly transfer the thermal energy of the thermal destruction system into the fluidized bed thermal desorption system to indirectly heat it.

In the apparatus of the present invention, the gases in and out of each system constituting the apparatus are circulated organically with each other, which is well illustrated in the following description of the material and energy circulation.

1 is a schematic diagram of an indirect heated fluidized bed device with a heating tube interpolated for oil contaminated soil restoration according to the present invention, and the material circulation is as follows. The soil contaminated with oil is fed into the fluidized bed through the contaminated soil supply pipe (1) and the purified soil is discharged through the purified soil discharge pipe (2). The fine soil scattered during the process is discharged through the cyclone (3) in combination with the soil discharged back to the contaminated soil supply pipe (1) or from the purified soil discharge pipe (2). In addition, the desorbed oil (hydrocarbon) in the fluidized bed is discharged through the desorption gas discharge pipe (4) and supplied to the thermal destruction system through the desorption gas supply pipe (8) by a circulation pump, oxidized in the oxidation catalyst bed and converted into carbon dioxide and water, Carbon dioxide, condensate and water vapor contained in the soil are discharged to the waste gas discharge pipe (6), and the amount of oxygen consumed to burn the oil content by the oxidation reaction is introduced into the thermal destruction system through the oxygen supplement supply pipe (7) as oxygen or air. Supplied.

Meanwhile, the energy cycle is as follows. The contaminated soil at room temperature is supplied into the fluidized bed through the contaminated soil supply pipe (1) and the oil is desorbed while being heated to a temperature in the range of 200 to 300 ℃, and the purified soil is discharged through the purified soil discharge pipe (2). In addition, the heated gas in the fluidized bed contains an oil content and is discharged through the desorption gas discharge pipe 4 to circulate to remove as much oxygen as necessary to burn the oil content by the oxidation reaction and moisture generated during the combustion reaction. (Mainly containing H ₂ O, CO ₂ and O ₂ ) and supplied to the thermal destruction system through the desorption gas supply pipe 8 by a circulation pump. The heat of combustion generated in this system is transferred by the heating tube through the fluidizing gas supply pipe 5 into the fluidized bed. Most of the combusted gas is supplied as it is to the fluidized bed and serves as a heat source for heating the contaminated soil, but about 10% of the amount of combusted gas is discharged through the waste gas discharge pipe (6) to remove moisture generated during the process or desorbed from the contaminated soil. Removed from the process.

Hereinafter, the present invention will be described in detail with reference to representative examples, but these examples are only intended to illustrate embodiments of the present invention and do not limit the scope of the present invention.

Example 1

Measure the temperature change over time of soil contaminated with 10% diesel oil in the fluidized bed while changing the heating part temperature of the naphthalene heating tube using naphthalene as the working fluid to 200 ° C, 300 ° C and 450 ° C The weight loss of the sample was investigated by thermogravimetric analysis by sampling in units, and the results calculated based on the weight loss due to heat treatment are shown in Table 1 below. Desorption rate was defined as the rate of change in weight per unit of time sampled in a fluidized bed thermal desorption system to the original weight of the contaminated soil.

TABLE 1

Temperature change and desorption rate in a fluidized bed thermal desorption system over time of soil contaminated with 10% diesel oil measured by varying the temperature of the heating section.

As shown in Table 1, as the temperature of the heating tube was increased, the desorption rate increased and about 95% of the contaminants were desorbed at the fluidized bed temperature of 300 ° C.

In addition, the residual amount of the actual diesel oil component was measured by the solvent extraction method. 2 g of the sample was mixed with 2 cc of methylene chloride, extracted for about 2 hours by an ultrasonic wave, and filtered. 2 μl was analyzed using GC-FID (Model: HP 6890, manufactured by Hewlett Packard). It was. Figure 2 is a graph showing the oil content of the contaminated soil in the thermal desorption system over time when purifying the soil contaminated with 10% diesel oil in the fluidized bed thermal desorption system of 300 ℃.

As can be seen from FIG. 2, the diesel oil component that is not removed remains rapidly reduced as the heat treatment time elapses, and about 99% of the diesel oil component, which is much higher than the value calculated on the basis of weight loss, is removed. It was confirmed. In addition, the C ₁₀ -C ₁₅ component begins to be rapidly removed as the heat treatment time elapses, and is completely removed after 30 minutes. However, C ₂₁ or more hydrocarbons having a relatively high molecular weight have a relatively low removal rate and thus remain after 30 minutes of heat treatment time. It can be seen that it constitutes most of the.

From these results, the fluidized bed thermal desorption system in which the heating tube is inserted can effectively transfer heat into the thermal desorption system without a separate heat transport mechanism, and can also utilize heat energy generated during catalytic oxidative combustion to maximize energy utilization. Has proven to be an economical, high-efficiency system.

Example 2

Thermal destruction efficiency of desorbed organic compounds was measured using a platinum-based honeycomb oxidation catalyst. Reaction conditions used the space velocity to 12,000 hours ^-1 , and the enriched air whose oxygen concentration is about 27%. The feed concentrations of the three organic compounds of BTX and diesel oil are 0.0032-0.0035 g / cc for benzene, 0.0025-0.0028 g / cc for toluene, 0.0022-0.0024 g / cc for meta-xylene and 0.000794 g for diesel oil, respectively. Fracture experiment was performed with / cc, and as shown in Table 2, it was found that about 90% or more was removed.

TABLE 2

Removal Efficiency on Platinum Honeycomb Oxidation Catalysts for Various Petroleum Products

By using the indirect heated fluidized bed apparatus according to the present invention for oil contaminated soil recovery, the contaminated soil can be desorbed by the fluidized bed thermal desorption system, and the desorbed oil can be decomposed and removed by the oxidation catalyst in the thermal destruction system. Indirect heating using a heating tube system enables efficient transfer of heat into the thermal desorption system without the need for a separate heat transport mechanism, as well as the use of thermal energy generated during catalytic oxidative combustion, maximizing energy use to remove contaminated soil. Can be restored to high efficiency.

Claims (4)

In the heated device for restoring oil contaminated soil, (1) fluidized bed thermal desorption systems for desorption of oil in oil-contaminated soils, (2) a low temperature thermal destruction system equipped with an oxidation catalyst for burning oil desorbed in the fluidized bed thermal desorption system, (3) located between the fluidized bed thermal desorption system and the low temperature thermal destruction system to form a multi-stage structure with these systems (1, 2), the heat of combustion of the desorbed oil content generated in the thermal destruction system; A heating tube system for providing a heat source of the phase thermal desorption system, and (4) a circulation system for causing gases in and out of the systems (1, 2, 3) to circulate organically with each other, Indirect heated fluidized bed apparatus with interpolated heating tubes for oil contaminated soil recovery. In the heating method for restoring oil contaminated soil, (1) continuously desorbing soil contaminated with oil through indirect heating by a heating tube system in a fluidized bed heat desorption system, (2) decomposing and removing the oil content desorbed in the fluidized bed heat desorption system in a heat destruction system using an oxidation catalyst, (3) providing combustion heat of the desorbed oil content generated in the thermal destruction system to the heat source of the fluidized bed thermal desorption system by the heating tube system, and (4) allowing gases in and out of the systems (1, 2, 3) to circulate organically with each other, How to restore oil contaminated soil. The method of claim 2, wherein the oil content desorbed in the fluidized bed heat desorption system is supplied to the heat destruction system by a circulation pump and oxidized in the oxidation catalyst layer in the heat destruction system to convert to carbon dioxide and water, the produced carbon dioxide and condensate and Exhausting water vapor contained in the soil and supplying externally as much oxygen as is consumed by the oxidation reaction in the thermal destruction system. 3. The method of claim 2, wherein the heat of combustion generated when the oil content desorbed in the fluidized bed thermal desorption system is combusted in an oxidation catalyst layer in the thermal destruction system is transferred to the fluidized bed thermal desorption system by the heating tube system.