JPH06264764A - Methanol power generation using exhaust gas energy - Google Patents

Abstract

PURPOSE:To secure an inexpensive methanol source by thermally discomposing material methanol by way of using combustion exhaust gas sensible heat of a motor, making formaldehyde and crude or purified methanol and using it as methanol for steam reforming. CONSTITUTION:A sintered mineral is air-cooled by a sintering factory cooler 7, and sensible heat of the sintered mineral collected at this time is supplied to a methanol reforming device 1. Thereafter, by carrying out steam reforming of methanol, methanol steam, H2, CO2 are generated and they are supplied to a gas turbine 3. In the meantime, combustible gas is combustedby the gas turbine 3 and a generator 5 is driven. Subsequently, combustible exhaust gas of the gas turbine 3 is supplied to a gas turbine exhaust gas sensible heat collection device 9, and collected sensible heat is supplied to a material methanol thermal discomposing device 15 and an unreacted methanol preheating device 11. At this time, by thermally discomposing material methanol, formaldehyde and crude or purified methanol are made, and they are used as methanol for steam reforming.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes a sensible heat of exhaust gas at a relatively low temperature (for example, 500 ° C. or lower) generated in a steelworks or the like to obtain a methanol reforming combustible gas, and uses this gas as a fuel. Regarding how to generate electricity. In particular, it relates to a new process combining energy saving and organic synthesis, which can produce high-purity formaldehyde at low cost by utilizing sensible heat of exhaust gas generated in this power generation stage.

[0002]

2. Description of the Related Art A conventional technique will be described taking a technique in a steel mill as an example. In the recovery of sensible heat of exhaust gas at a temperature of 500 ° C. or less in a steel mill, steam recovery has been customary in the past. However, as an alternative method when the merit of process vapor recovery is small, hydrothermal power generation (Mitsubishi Heavy Industries Technical Report, 17, 40 to 45
(1980)) and CFC gas power generation (80th and 81st Nishiyama Memorial Technology Course P. 84-87 (1982)) were proposed. These methods have low energy conversion efficiencies of 20% or less, and have recently been postponed for adoption because of low energy prices.

The methanol power generation to which the present invention pertains is NEDO.
Is playing a central role in promoting development. However, considering the price of methanol (15 to 30 yen / kg in CIF) and the calorific value (5,330 kcal / kg), LNG power generation has a lower power generation unit price at an operation rate of 50% or more. Therefore, methanol power generation can only be positioned as an inland type, a remote island type, or a small-scale distributed generation for peak hours, and it is quite difficult to industrialize.

[0004]

In the three technical fields of power generation from methanol, recovery of intermediate- and low-temperature exhaust heat, and production of formaldehyde from methanol, the following problems existed. (1) Methanol At present, only high-purity methanol for the chemical industry can be effectively obtained as methanol for power generation. It is necessary to manufacture cheaper methanol to reduce the unit price of power generation.

(2) As a method of recovering the sensible heat of the cooler exhaust gas from the steel plant sintering plant, low-pressure steam recovery or hot water recovery is possible. However, there are no users in the steelworks, and if hydrothermal power generation is used, it will be completely unprofitable. (3) A number of patents for the production of formaldehyde by thermal decomposition of methanol have been issued (Japanese Patent Laid-Open No. 41185/41185).
3, JP-A-47-19251, JP-A-48-9780
8, JP-A-51-1407, JP-A-52-215, JP-A-51-76209, and JP-A-62-148443). However, in any of the production methods, unreacted methanol always remains because the equilibrium exists in the reaction yield in the range of 22.4 to 66.0%, and there is no suitable treatment destination. Then it could not be economically established.

In order to solve the above three problems in an integrated manner, the present invention manufactures inexpensive reforming methanol, and efficiently uses sensible heat of low-temperature exhaust gas, which has been difficult to use economically in the past. Aims to provide a new process combined with economical methanol pyrolysis formaldehyde production.

[0007]

In order to achieve the above object, the present invention uses a sensible heat of exhaust gas to steam-reform methanol to obtain a hydrogen-containing gas, and this gas is used as fuel for a prime mover for power generation. In the method of carrying out, the raw material methanol is pyrolyzed by utilizing the sensible heat of the combustion exhaust gas of the prime mover (accurately dehydrogenation but is referred to as pyrolysis in the present invention) to obtain formaldehyde and crude or purified methanol. The crude or purified methanol is used as the steam reforming methanol.

That is, in one embodiment of the present invention, the steam reforming of methanol is carried out by utilizing the sensible heat of the cooler exhaust gas from a steel plant sintering plant, and 1 kg of liquid fuel having a total calorific value of 5330 kcal / kg is converted to 6400 kcal at 280 ° C. Gas fuel of 0.2
It is converted to 6 Nm ³ and used as fuel for prime movers such as gas turbines to generate electricity. Furthermore, about 60 discharged from the prime mover
Using sensible heat of gas at 0 ° C, methanol is thermally decomposed to produce formaldehyde and hydrogen gas. The unreacted methanol generated at that time is used as the steam reforming methanol.

[0009]

[Function] The thermal decomposition of methanol is 400 to 6 in the presence of a catalyst.
It proceeds at a temperature of 50 ° C. and normal pressure. This reaction is an equilibrium reaction, and the decomposition rate of methanol is as follows. 327 ° C 427 ° C 527 ° C 627 ° C 17.2% 53.8% 86.1% 96.4%

To obtain a 100% decomposition rate, the reaction temperature is 70
Must be above 0 ° C. However, in such a high temperature state, the problem of carbon trouble occurs and the generated formaldehyde decomposes into CO and H ₂ . Therefore, in the end, 100% methanol
It cannot be disassembled. The problem here is that there is no effective source of unreacted methanol. If unreacted methanol is steam-reformed to improve calories and then burned in a gas turbine or the like to generate electricity, the unreacted methanol can be effectively used and formaldehyde production costs can be reduced.

Formaldehyde is currently produced as an aqueous formaldehyde solution having a concentration of 37% by air-oxidizing methanol and absorbing it in water produced at the same time. Formaldehyde for polyacetal and the like dislikes the presence of water, and thus is concentrated to a concentration of 99.9% or more. According to the present invention, a mixture of methanol and formaldehyde having a low water content can be obtained only by thermally decomposing methanol.

[0012]

EXAMPLES Examples of the present invention will be described below. Figure 1
It is a figure showing the process system of the power generation of this invention and the manufacturing method of formaldehyde. In the sinter factory cooler 7, the sinter ore is air-cooled. The sensible heat of the sinter recovered at this time is sent to the methanol reforming apparatus 1. The equipment receives methanol, steam (17 atm, 300 ° C), and sensible heat (280 ° C) from the sintering plant cooler 7,
Steam reforming of methanol is performed, methanol vapor,
H ₂ and CO ₂ are generated and sent to the gas turbine 3. The main reaction formula at this time is as follows. CH ₃ OH + H ₂ O → CO ₂ + 3H ₂

The gas turbine 3 comprises a methanol reformer 1
By burning the combustible gas supplied from
The generator 5 is rotated to generate electricity. The combustion exhaust gas (604 ° C.) of the gas turbine 3 is sent to the gas turbine exhaust gas sensible heat recovery device 9. In the device 9, the combustion air of the gas turbine is preheated to 554 ° C. The gas turbine exhaust gas sensible heat recovery device 9 includes, in addition to preheating the gas turbine combustion air,
Heat is also supplied to the raw material methanol thermal decomposition device 15 and the unreacted methanol preheating device 11 described later. Further, the preheated hot water (280 ° C) is supplied from the sinter plant cooler 7 to the methanol reformer 1 at 17 atm and 300 ° C.
We also supply steam for reforming. The above part of the present embodiment is substantially the same as a general methanol power generation process.

The part of the present embodiment to be described subsequently is the characteristic part of the process of the present invention of "pyrolysis of raw material methanol → formaldehyde production → separation of unreacted methanol". The raw material methanol supplied to the raw material methanol preheating device 13 may be fuel grade low-pure, low-purity methanol. The raw material methanol is preheated to 150 ° C. by the raw material methanol preheating device 13 using the sensible heat of the sintering plant cooler, becomes methanol vapor at 150 ° C., and is supplied to the raw material methanol thermal decomposition device 15.

A gas of 100% methanol vapor may be supplied to the raw material methanol thermal decomposition apparatus 15, but the hydrogen rich gas discharged from the thermal decomposition apparatus 15 is used as a diluent gas for the methanol vapor to dilute the methanol vapor. May be supplied. Preferably, it is diluted with 30 to 50% by volume of hydrogen-rich gas (circulation gas). Thermal energy for the pyrolysis device is provided from the gas turbine exhaust gas sensible heat recovery device 9. The main reaction equation of methanol pyrolysis is as follows. CH ₃ OH → HCHO + H ₂ In order to accelerate this decomposition reaction, a copper-based, zinc-based or zeolite-based catalyst is effective.

The gas generated in the raw material methanol pyrolysis device 15 is sent to the cooling device 17 and cooled. At this time, 0.37 parts of white paraformaldehyde, 0.09 parts of formaldehyde, and 0.5 parts of unreacted methanol (liquid phase) are obtained with respect to 1 part of raw material methanol. The gas discharged from the cooling device 17 is a hydrogen-rich gas having a H ₂ concentration of 90% or more containing a small amount of CO, CH _{4, and the} like. This hydrogen-rich gas can be sent to the raw material methanol pyrolyzer 15 as a diluted circulating gas and also used as a fuel for a gas turbine. In such a case, the gas turbine fuel can be increased in calories, and the amount of power generation and steam generation can be increased.

In the separator 19, formaldehyde and unreacted methanol are separated. About 0.4 parts of the unreacted methanol separated was used as the unreacted methanol preheater 11
Then, it is preheated to 150 ° C. using the sensible heat from the gas turbine exhaust gas sensible heat recovery device 9 and supplied to the methanol reforming device 1.

The methanol reformer 1 has 17 atm, 3
1.65 parts of steam at 00 ° C are also supplied. Where C
In the presence of a u-Zr (or Cu-Ni etc.) catalyst, the sensible heat of the exhaust gas (280 ° C.) of the sintering plant cooler 7 is also supplied to carry out the steam reforming reaction of methanol. As a result, the obtained reformed gas is supplied to the gas turbine 3.
The gas turbine 3 is supplied with 20.6 parts of combustion air after being preheated to 554 ° C. by the gas turbine exhaust gas sensible heat recovery device 9. In addition, steam for methanol reforming (17 at
m, 300 ° C.) is obtained by heating 2.66 parts of soft water to 80 to 280 ° C. in the sintering factory cooler 7 and then further heating in the gas turbine exhaust gas sensible heat recovery device 9.

In the method of the present invention, the entire amount of methanol received in the process is passed through a "pyrolysis → formaldehyde production" line, and only unreacted methanol obtained in the line is subjected to a "steam reforming → gas turbine combustion" line. It can also be flushed. In such an operation pattern, formaldehyde can be increased in production. Of course, when it is desired to suppress the production of formaldehyde and increase the amount of power generation, methanol may be directly fed to the methanol reformer 1.

[0020]

As is apparent from the above description, the methanol power generation method using exhaust gas energy of the present invention exhibits the following effects. By using unreacted methanol after producing formaldehyde as the power generation methanol, an inexpensive methanol source can be secured, so that the power generation cost can be reduced.

[0021] In a steel mill or the like, low temperature exhaust gas energy recovery can be recovered as hot water or process steam (at low pressure) when there is a use destination, but it is remarkably converted when converting to electric energy when there is no use destination. Efficiency is low. However, a conversion efficiency of 30% can be achieved by combining the methanol power generation by steam reforming of methanol of the present invention. Can construct economically decomposing methanol decomposition formaldehyde production process.

[Brief description of drawings]

FIG. 1 is a diagram showing a process system of a power generation method and a formaldehyde production method of the present invention.

[Explanation of symbols]

 1 Methanol reforming device 3 Gas turbine 5 Generator 7 Sintering plant cooler 9 Gas turbine exhaust gas sensible heat recovery device 11 Unreacted methanol preheating device 13 Raw material methanol preheating device 15 Raw material methanol thermal decomposition device 17 Cooling device 19 Separation device

Claims (3)

[Claims] 1. A method of producing hydrogen-containing gas by steam reforming methanol by utilizing sensible heat of exhaust gas, and using this gas as fuel for a prime mover to generate electricity; using sensible heat of combustion exhaust gas of the prime mover. A methanol power generation method using exhaust gas energy, which comprises thermally decomposing raw material methanol to obtain formaldehyde and crude or purified methanol, and using the crude or purified methanol as the methanol for steam reforming. 2. A gas having a high hydrogen concentration or other combustible gas generated during the thermal decomposition of the raw material methanol is mixed with a hydrogen-containing gas obtained by the steam reforming and used as the fuel for the prime mover. A methanol power generation method using the described exhaust gas energy. 3. The methanol power generation method using exhaust gas energy according to claim 1 or 2, wherein the exhaust gas sensible heat is cooler exhaust gas sensible heat of a steel plant sintering plant.