JP2007224206A - Method for forming high-calorie gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a high-calorie gas by the hydrogenation and the conversion into a reducing gas of an organic material such as a waste plastic, a waste tire and a biomass including waste wood to afford a hydrocarbon or CO at a low cost in high reaction efficiency without using special external energy. <P>SOLUTION: The method for forming the high-calorie gas by decomposing and gasifying the organic material comprises feeding a coke oven gas having ≥60% hydrogen content and ≥600°C temperature to the organic material to progress the thermal cracking and the hydrogenation and gasification reaction of the organic material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for producing a high calorific gas, and a gas produced in a coke oven such as a steel mill (hereinafter referred to as a carbon source) while treating an organic material that can be hydrocracked, such as waste plastic, waste tire, and biomass. Using the H ₂ component and sensible heat in the coke oven gas (or COG), gasify it as hydrocarbons or CO and simultaneously recover it with COG and recover it with high-calorie gas recovery. On how to achieve.

Blast furnace coke used as a reducing agent for iron ore in the iron making process is produced by dry distillation of powdered coal at a temperature of about 1000 ° C. for about 20 hours using a coke oven. The pyrolysis gas of coal generated in this process (hereinafter referred to as coke oven gas or COG) contains a large amount of flammable components such as H ₂ and is therefore used as a fuel gas in each manufacturing process of the iron making process. Yes.

The coke oven gas is taken out of the coke oven through a conduit, purified by a water condenser, direct cooler, naphthalene scrubber, ammonia scrubber, etc., and then stored in a gas holder. This coke oven gas usually has an average gas composition of CH ₄ 30%, C ₂ H ₄ 5%, C ₂ H ₆ 0.5%, CO 5%, CO ₂ 5%, H ₂ 55%, other The gas is about 5%, and the amount of combustion heat is 4500-4800 Kcal / Nm ³ .

  On the other hand, in addition to the above coke oven gas, as a gas generated in the iron making process, a gas generated in the process of reducing iron ore in a blast furnace (hereinafter referred to as blast furnace gas or BFG), a process in which pig iron is refined in a converter There are generated gases (hereinafter referred to as converter gas or LDG), and gases generated by CDQ (coke dry quencher) (hereinafter these gases are referred to as low calorific gas).

  In either case, the amount of combustion heat is lower than that of the coke oven gas, but it is used alone or mixed with the coke oven gas as the energy gas for each facility in the iron making process.

  By the way, conventionally, methods for increasing the amount of heat of coke oven gas have been studied.

For example, a method is known in which coke oven gas is reformed using a steam reforming method to increase the amount of heat. This method promotes the reaction between hydrocarbons in coke oven gas and water vapor (H ₂ O) at a temperature of about 300 to 500 ° C. using a catalyst, and is determined by the equilibrium reaction shown below. The gas is converted into a gas having a mixed composition of (CH ₄ ), hydrogen (H ₂ ), carbon monoxide (CO), and carbon dioxide (CO ₂ ).

CO + 3H ₂ ⇔CH ₄ + H ₂ O (1)
CO + H ₂ O⇔CO ₂ + H ₂ (2)
2CO⇔CO ₂ + C (3)
CH ₄ ⇔2H ₂ + C (4)
In the equilibrium reaction, the reaction for increasing the calorific value of the coke oven gas is a reaction of the above equation (1) for obtaining methane (CH ₄ ) from carbon monoxide (CO). Since the concentration of carbon monoxide (CO) is as low as several percent, a large increase in the amount of heat cannot be achieved. For this reason, conventionally, a carbon source such as LPG or naphtha is added to the coke oven gas, and the amount of methane produced is increased by performing steam reforming to convert the gas into a high calorific value gas.

By this method, it is possible to use H ₂ with a content of more than 50% in coke oven gas and convert it to high calorific gas like city gas, but it requires expensive carbon raw materials such as LPG and naphtha. However, it is not an industrially advantageous method in terms of production cost and production efficiency.

Further, instead of expensive LPG, naphtha, etc., using an inexpensive carbon source such as powdered coal, plastic, rubber, waste, etc., and hydrogen (H ₂ in coke oven gas heated to 700 ° C. or higher) ) (Hydrogenation gasification reaction) to generate methane (CH ₄ ) to increase the amount of heat of the coke oven gas by about 35% (for example, see Patent Document 1).

However, in this method, since the storage coke oven gas purified after being discharged from the coke oven is used as a reaction gas, the concentration of hydrogen (H ₂ ) in the reaction gas is as low as less than 60%. However, sufficient reaction efficiency for producing methane (CH ₄ ) having a large calorie cannot be obtained.

  Moreover, since this storage coke oven gas is at room temperature, it must be heated to a reaction temperature of 700 ° C. or higher, and another heating facility for hydrogenation gasification reaction is required, which is disadvantageous in terms of operation cost. It was a method.

In addition, because the gas composition of storage coke oven gas varies with changes in coal raw materials and operations during coke production, methane (with the change in hydrogen (H ₂ ) content in storage coke oven gas There was also a problem that the amount of CH ₄ ) produced and the amount increased increased.

Conventionally, most of waste plastics, waste tires, biomass containing waste materials, and the like have been burned and incinerated. However, the combustion treatment increases the environmental load such as CO ₂ generation. In particular, the waste plastic has a large calorific value, so that there is a problem that the incinerator is damaged, and in the landfill disposal, the emission amount increases. There is a shortage of landfill, and in particular, waste plastics and waste tires have a problem that they are not decomposed by bacteria and bacteria in the soil.

  Therefore, in recent years, there is a demand for adopting environmentally friendly recycling technology without incinerating and landfilling these waste organic substances. Currently, as a recycling method that does not incinerate, in addition to reuse as a chemical raw material, a method of reusing a gas or oil obtained by pyrolysis as a fuel or chemical raw material is being studied.

JP 2000-303081 A

  In light of the current state of the prior art described above, the present invention can be applied to hydrocarbons or organic materials such as waste plastics, waste tires, and biomass containing waste materials at low cost and high reaction efficiency without using special external energy. It is an object of the present invention to provide a method for generating high calorific gas by hydrogenation and reduction gasification of CO.

In order to solve the above problem, the present inventors diligently studied about a solution, and as a result, high hydrogen (H) separated from coke oven gas directly into organic materials such as waste plastic, waste tire, and biomass containing waste material. ₂ ) We have found a method to supply coke oven gas with concentration and sensible heat to produce high calorific gas at low cost and high reaction efficiency.

  The present invention has been made on the basis of such knowledge, and the gist thereof is as follows.

  (1) In a method for producing a high calorific gas in which an organic substance is decomposed and gasified, a coke oven gas having a hydrogen concentration of 60% or more and a temperature of 600 ° C. or more is supplied to the organic substance, A method for producing a high calorific gas, characterized by advancing thermal decomposition and hydrogenation reaction of an organic material.

  (2) The coke oven gas is a gas obtained by continuously measuring the hydrogen concentration of gas generated in the coke oven and separated and recovered when the hydrogen concentration reaches 60% or more. (1) The method for producing a high calorific gas described in (1).

  (3) The above-mentioned (1) or (2), wherein the organic material is an organic material capable of hydrocracking consisting of one or more of waste plastic, waste tire, and biomass. Of high calorific gas production.

According to the present invention, a coke oven gas having a high hydrogen (H ₂ ) concentration and sensible heat is separated from a coke oven into an organic material that can be hydrocracked, such as biomass including waste plastics, waste tires, and waste building materials. Then, the hydrogenation gasification reaction of the organic substance is allowed to proceed, and a high calorific gas can be generated at low cost and high reaction efficiency.

  By applying the present invention, it becomes possible to decompose municipal waste such as plastics and obtain a high calorie gas, so that the energy self-sufficiency efficiency in the steelmaking process is improved, and the contribution to environmental improvement is great, It can be said that the industrial contribution is great.

  Details of the present invention will be described below.

The present inventors pay attention to hydrogen (H ₂ ) and sensible heat in coke oven gas discharged from the coke oven, and use these hydrogen (H ₂ ) and sensible heat to generate a large amount as waste. We studied in detail how to efficiently gasify organic materials that can be hydrocracked, such as waste plastics, waste tires, and biomass containing waste building materials, into caloric gases such as hydrocarbons and CO.

  Hereinafter, the reaction using waste plastic as an example will be described. However, for substances having a hydrocarbon structure that undergoes a hydrogenation reaction, such as waste tires and biomass containing waste building materials, the reaction is almost the same for some parts. move on.

In general, it is known that when an organic material such as waste plastic is heated to a high temperature and hydrogen (H ₂ ) is supplied, the organic material is decomposed into lower hydrocarbons and gasified.

  For example, polyethylene (PE) and polypropylene (PP), which are the main components of waste plastics, begin to be randomly decomposed in a temperature range of about 400 ° C. Further, when the temperature rises, hydrogen is added to the thermally decomposed hydrocarbons. Addition produces lower hydrocarbon gas.

  In addition, plastics containing phenyl groups such as polystyrene, which is a polymer of alkylbenzene, also generate monomers and low polymers by depolymerization at about 300 ° C, and these undergo further thermal decomposition and hydrogenation reaction at higher temperatures. To produce hydrocarbon gas.

  Plastics containing a phenyl group such as polystyrene, compared with the above-mentioned aliphatic polymers such as polyethylene (PE) and polypropylene (PP), have a lower generation rate of lower hydrocarbon gas, but thermal decomposition starts at about 350 ° C. At a high temperature, about 50% by weight of lower hydrocarbon gas is generated, and the remainder becomes oily, tar and wax components.

  The temperature of gasification by pyrolysis or hydrogenation reaction varies depending on the type of polymer in the waste plastic, but at temperatures of about 300-400 ° C, the amount of oil and wax components produced by pyrolysis of the polymer increases, but the gas There is not much progress in lowering the polymer until it is made.

  As a result of the study by the present inventors, organic materials such as the above-mentioned waste plastic and biomass including waste tires and waste building materials are heated and recovered as energy gas by thermal decomposition and hydrogen reaction, mainly C = 1 to It was confirmed that the temperature of coke oven gas supplied to the organic material must be 600 ° C. or higher in order to efficiently produce about 3 lower hydrocarbon gas. For this reason, in the present invention, the temperature of the coke oven gas supplied to the organic material is set to 600 ° C. or higher.

  As described above, organic materials such as biomass and waste tires, such as waste plastics and waste building materials that have aliphatic main chains, are subject to hydrogenation reaction in the presence of hydrogen reducing atmosphere gas at a heating temperature range of 600 ° C or higher. Progression mainly produces lower hydrocarbon gas of about C = 1 to 3 and, in addition, produces oil, tar, and wax components containing phenyl groups that are difficult to be decomposed.

  Further, a part of the generated hydrocarbon gas reacts with oxygen or the like contained in a trace amount in the organic material, and more stable CO gas is generated in a high temperature range.

  That is, hydrocarbon gas obtained by thermal decomposition and hydrogenation reaction of organic materials such as waste plastic can be used as fuel gas etc., and recovered as high calorie gas mainly containing high calorie hydrocarbon gas and CO can do. In addition to the high calorific gas, some oil, tar and wax components produced can also be used as fuel and chemical raw materials.

A coke oven that supplies high-temperature coke oven gas to the above-mentioned organic material and proceeds to the hydrogenation reaction along with thermal decomposition of the organic material to produce the desired high calorific gas. In addition to the above temperature conditions of the gas, it is necessary to increase the hydrogen (H ₂ ) concentration in the coke oven gas.

As an example, FIG. 1 shows the relationship between the concentration of hydrogen (H ₂ ) in coke oven gas (COG) supplied to waste plastic and the rate of increase in the amount of combustion heat of the gas.

  1 L of coke oven gas (COG) having a different hydrogen concentration at 800 ° C. was supplied to 100 mg of waste plastic at atmospheric pressure, heated for 5 minutes, and the combustion heat of the gas was calculated from component analysis of the generated hydrocarbon gas.

It can be seen from FIG. 1 that when the concentration of hydrogen (H ₂ ) in the coke oven gas (COG) supplied to the waste plastic exceeds 60%, the rate of increase in the amount of combustion heat of the product gas is further increased. This indicates that when the hydrogen (H ₂ ) concentration is 60% or more, the hydrogenation reaction of the waste plastic proceeds rapidly and satisfactorily.

On the other hand, in the steady state where the hydrogen concentration is lower than 60%, the gasification to hydrocarbons does not proceed sufficiently in terms of reaction equilibrium because CH ₄ is present in about 30% in the COG at the same time.

  The results shown in FIG. 1 were the same for organic substances that can be hydrocracked, such as other waste plastics, waste tires, and biomass.

That is, in order to generate a high calorific gas with an increased target heat increase sufficiently and stably by a hydrogenation reaction of an organic material, and to recover this efficiently, hydrogen ( It was found that the H ₂ ) concentration needs to be 60% or more.

Therefore, in the present invention, in the hydrogenation reaction between the organic material and hydrogen (H ₂ ) in the coke oven gas, in order to improve the reaction efficiency and generate a high calorific gas sufficiently and stably, the coke oven In addition to the temperature regulation of the gas, the hydrogen (H ₂ ) concentration in the coke oven gas supplied to the organic material is set to 60% or more.

  In the present invention, the coke oven gas having a hydrogen concentration supplied to the organic substance of 60% or more and a temperature of 600 ° C. or more can be produced as follows.

Generally, the hydrogen (H ₂ ) concentration in the purified storage coke oven gas after being discharged from the coke oven is about 50-55%, but at this level of hydrogen (H ₂ ) concentration Since the reducing power is insufficient, the efficiency of the hydrogenation reaction cannot be improved and the amount of heat increase cannot be sufficiently increased.

As a method for increasing the hydrogen (H ₂ ) concentration (usually about 50 to 55%) in the coke oven gas to 60% or more, for example, a hydrogen separation method such as hydrogen PSA (Pressure Swing Adsorption) is used. A hydrogen concentration process for separating and purifying hydrogen therein is known. However, the hydrogen concentration treatment improves the reducing power of CO ₂ in the low calorific gas, but since the coke oven gas is cooled, external energy for heating to a temperature at which the reduction reaction is performed is required. It is not preferable.

The present inventors separated the coke oven gas discharged from the coke oven, and then maintained the temperature of 600 ° C. or higher by sensible heat without cooling the hydrogen (H ₂ ) concentration in the coke oven gas. A method for improving the ratio to 60% or more was examined.

  FIG. 2 shows changes with time of the main component concentrations in the coke oven gas during the coal carbonization process.

From FIG. 2, among the gas component compositions contained in the coke oven gas, the H ₂ concentration has a large time change in the dry distillation process compared to other gas components such as CH ₄ , and in particular, the end of the dry distillation (in this case) After about 15 hours), the hydrogen concentration in the coke oven gas increased rapidly and was found to exceed 90%.

  It was also confirmed that the coke oven gas generated at the end of dry distillation (2 to 3 hours (set time) from the end of the fire to the end of dry distillation) contained almost no oil such as tar.

In the present invention, the hydrogen (H ₂ ) concentration in the coke oven gas in the coke oven gas during the carbonization process is used to measure the hydrogen (H ₂ ) concentration of the gas generated in the coke oven continuously. H ₂₎ separation when the concentration became 60% or more, by using the recovered gas, while maintaining the temperature above 600 ° C., hydrogen (H ₂₎ concentration to ensure a 60% of the coke oven gas be able to.

  An example of an embodiment of the present invention will be described with reference to FIG.

The hydrogen (H ₂ ) concentration in the coke oven gas (COG0) discharged from the coke oven 2 is continuously monitored from the start of dry distillation to the end of dry distillation using a hydrogen gas monitoring device 3 equipped with a detector such as a hydrogen sensor. When the hydrogen (H ₂ ) concentration reaches a predetermined value of 60% or more, more preferably 80% or more, the flow is switched from the normal COG piping 6 side to the reaction tank 4 side in the flow path switching unit 4 of the COG gas conduit. The passage is switched, and coke oven gas (COG1) having a hydrogen (H ₂ ) concentration of 60% or more, more preferably 80% or more is supplied to the reaction vessel 4.

The predetermined value of the hydrogen (H ₂ ) concentration in the coke oven gas is appropriately set so that the hydrogen concentration from the start of dry distillation to the end of dry distillation is in the range of 60 to 90%. Further, the temperature of the coke oven gas can usually be maintained at a temperature of about 800 ° C. from the start of dry distillation to the end of the dry distillation, and a predetermined temperature of 700 ° C. or higher can be ensured for decomposition of organic substances and hydrogenation reaction temperature. If necessary, it is possible to cool for adjusting the reaction temperature.

  The generated high calorific gas (HG) is partially gasified and returned to a normal COG conduit together with oily substances, and oil, moisture, etc. are removed by a normal COG refining treatment equipment 7 and purified. And finally stored in the COG storage holder 8.

  In order to maintain the sensible heat of the coke oven gas and supply it to the reaction tank 4, the reaction tank 4 and the conduit connecting the rise pipe of the coke oven gas and the reaction tank 4 and the reaction tank 4 are kept warm by a heat insulating material or the like. Further, it is desirable to install the reaction tank 4 in a place as close as possible to the coke oven 2.

  The organic substance is intermittently supplied to the reaction tank 4 and is used as a fuel or power generation energy for each facility in the iron making process as a high calorific gas by hydrogenation reaction, thereby improving the energy self-sufficiency efficiency. In addition, if waste or the like is used as the organic substance, waste treatment in the iron making process can be realized by the present invention, and an environment improvement effect can be obtained.

  Next, the effects of the present invention will be described with reference to examples.

  Using the equipment shown in FIG. 2, 10 kg of waste plastic (of which about 9 kg of carbon) is charged into the reaction tank 4, and as an example of the invention, hydrogen at the end of the coal dry distillation period (after 15 hours from the start of dry distillation) generated in a coke oven A coke oven gas (COG1) having a concentration of 85% and a general coke oven gas (COG) having a hydrogen concentration of 56% were supplied as comparative examples. At this time, the temperature of the coke oven gas (COG) was adjusted to 800 ° C.

  Table 1 shows the conditions and results of the inventive examples and comparative examples.

Coke oven gas (COG1) (main component H ₂ : 85%, CO ₂ : 1%, CO: 5%) satisfying both the conditions of hydrogen concentration and temperature specified in the present invention is applied to the waste plastic filled in the reaction layer. By supplying the waste plastic, the hydrogenation gasification reaction proceeds with H ₂ in the coke oven gas, and 95 wt% or more thereof is gasified, and the generated gas (HG) is CH ₄ , C ₂ H ₄ and The total amount of CO and the like was about 15 Nm ³ . Heat at this time is 115Mcal, corresponds to approximately twice the heat of 15 Nm ³ normal COG (4500~4800kcal / Nm ^3).

On the other hand, the coke oven gas (COG) (H ₂ : 56%, CO ₂ : 3%, CO: 5%), which is out of the low hydrogen concentration but satisfies the temperature conditions defined in the present invention, is used as waste plastic. When supplied, the hydrogenation reaction of waste plastic does not proceed sufficiently, the gasification rate is as low as about 50%, carbon is not gasified, and is obtained as an oily component that is not carbonized or sufficiently low molecular weight, The increase in the calorific value of the COG gas was small.

It is a figure which shows the relationship between the hydrogen concentration in coke oven gas, and the calorie | heat amount increase rate of the generated gas accompanying decomposition | disassembly of waste plastics. It is a figure which shows the time-dependent change of the main component density | concentration in the coke oven gas in a coal carbonization process. It is a figure which shows the processing flow of high calorific gas production | generation which shows an example of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coke oven 2 Hydrogen gas monitoring device 3 Flow path switching part 4 Reaction tank 5 Organic substance 6 Normal COG piping 7 COG refinement processing equipment 8 COG storage holder COG0 Coke oven gas COG1 High H2 concentration coke oven gas HG High calorie gas

Claims (3)

  In the method for producing a high calorific gas for decomposing and gasifying an organic substance, a coke oven gas having a hydrogen concentration of 60% or more and a temperature of 600 ° C. or more is supplied to the organic substance, A method for producing a high calorific gas, wherein the thermal decomposition and hydrogenation gasification reaction of water are advanced.   The coke oven gas is a gas separated and recovered when the hydrogen concentration of the gas generated in the coke oven is continuously measured and the hydrogen concentration reaches 60% or more. Of high calorific gas production.   The high-calorific gas production according to claim 1 or 2, wherein the organic material is an organic material that can be hydrocracked consisting of one or more of waste plastic, waste tire, and biomass. Method.

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