JPS5829929B2 - Methanol production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a methanol production method, and its purpose is to not only be able to provide power for the plant itself, but also to be able to supply surplus power to other plants, eliminating the need for a reforming furnace. The present invention has the following advantages: the produced water can be supplied to other plants, the methanol concentration step can be simplified, and the synthesis column can be manufactured at low cost. Examples thereof will be described below with reference to the drawings.

First, the state of methanol production will be explained based on FIG.

Natural gas (or methane gas, etc.) 1 is supplied from a burner 4 to a boiler 5 together with air 3 that has passed through a filter 2.
It is combusted in the boiler 5.

The combustion gas (G) generated in the boiler 5 passes through the opening/closing flange section 6 and the first valve 7, is cooled in the cooler 9 to which cooling water 8 is supplied, and then is cooled in the steam separator 1.
Water is removed at 0.

Note that the temperature of the combustion gas at the outlet of the boiler 5 is 120°C, and the temperature of the combustion gas at the outlet of the cooler 9 is about 80°C.

The water (H2O) removed here is sent to the deaerator 11,
Further, the combustion gas fG) is sent to the CO2 extraction device 12.

In this CO2 extractor 12, the combustion gas (G) is washed with a chemical liquid such as 2CO3 to allow the 2CO3 to absorb CO2, and the 2CO3 solution containing CO2 is stripped with steam to extract CO2 residue. However, gases other than CO2 are purged (P).

However, if the purge gas contains flammable gas such as methane (such as when the boiler is operated at an excess air ratio of 1.0 or less), it is not possible to return this gas to the fuel line of boiler 5. be.

Hydrogen gas (H2) is added to the gas (CO2) from this CO2 extraction device 12, and this
).

This raw material gas (CO2+H2) is pressurized by the compressor 13 and sent to the synthesis column 15 via the second valve 14.

While passing through the catalyst layer 16 of this synthesis tower 15, vaporized methanol M is synthesized.

9 to 16 above constitute a vaporized methanol production line.

Water (H20) taken out from the deaerator 11 by the water supply pump 17 is heated in the economizer 18 in the boiler 5, then taken out from the boiler 5, and supplied to the synthesis column 15 via the first control valve 19. , the synthesis heat generated in the synthesis process is absorbed in a non-contact manner to promote the synthesis reaction.

The heated water from the synthesis tower 15 is led to the boiler 5 again via the third valve 20, and then to the evaporation section 21. and is heated in a superheater 22, thereby generating steam M.

A bypass line 24 having a second control valve 23 is provided in parallel with the synthesis column 15.

Therefore, by operating both control valves 19 and 23, it is possible to control the amount of boiler water sent to the synthesis column 15.
5 can be controlled to the optimum temperature for synthesis.

In the embodiment, heated water from the economizer 18 is shown as the heat source medium taken out from the boiler 5, but the optimum position may be determined depending on the operating conditions of the synthesis column 15 and the boiler 5.

That is, depending on the operating conditions, it is also possible to recover the synthetic heat by taking it out from before the economizer 18, at an intermediate position in the evaporator 21, or at an intermediate position in the superheater 22.

Steam M generated in the superheater 22 is sent to a steam turbine 25 and becomes a working fluid for the steam turbine 25, and power is extracted by a generator 26.

Note that the gas pressure at the outlet of the turbine 25 is approximately 700 mmH.
g and the temperature is about 90%.

The steam M whose pressure has been reduced thereby is cooled in a condenser 28 to which cooling water 27 is supplied, and the condensed water is sent to the deaerator 11.

On the other hand, vaporized methanol and unreacted gas M from the synthesis tower 15 are sent to the gas turbine 29 and become working fluid for the gas turbine 29, and power is extracted by the generator 30.

The vaporized methanol and unreacted gas M, whose pressure has been reduced thereby, are cooled in a cooler 32 to which cooling water 31 is supplied, and then separated into a methanol aqueous solution (CH30H + H20) and an unreacted gas (Ml) in a steam-water separator 33. separated into

The unreacted gas (Ml) is pressurized by the recycle compressor 34 and then sent to the synthesis tower 15 again.

The methanol aqueous solution (CH30H + H20) is sent to the methanol stripper 35, where it is heated by the steam M extracted from the steam turbine 25 and flowing through the methanol stripper 35 to the condenser 28, and the evaporated content is Condensed methanol (CH30H) is obtained by being condensed in the condenser 37 to which the cooling water 36 is supplied.

Water (H2O) in the deaerator 11 is used in this process, but the excess water is purged (P).

The above 31 to 37 constitute a liquefied methanol production line.

In FIG. 1, thick lines indicate power plant lines, and thin lines indicate synthetic gas lines.

Although the boiler 5 is a once-through boiler in the above embodiment, it may be a narrow type boiler.

The operating conditions of the synthesis tower 15 are 50 to 300 kg/Cm, 25
The temperature is about 0 to 400°C.

Generally, in a methanol plant, low pressure operation is advantageous if the raw material gas is inexpensive.

Next, this process was applied to a 1000 T/D plant on an economic basis, and the calculation results are shown in the material balance sheet in Figure 2.

In this case, Ql is the amount of heat generated in the boiler 5, and Q2 is the amount of heat generated in the synthesis column 15.
(E,) is the output of the generator at the steam turbine 25, and (E2) is the output of the generator at the gas turbine 29.

The reaction formula in the O process is as follows.

Methanol yield: 40% (generally 3
(range 0 to 60%) Purge of recycle line...... None 0 Design conditions on the power plant side Boiler steam conditions 230 kg/caG x 560℃ (
Superheater outlet) Boiler water supply conditions 260 kg/criG X 1.4
0°C boiler excess air ratio 1.1 Boiler efficiency 92% (low standard) Thermal efficiency as a power plant 35% ○Synthesis tower operating conditions 250 kg/cttlG X 3
50℃ and the boiler water side pressure is about 250 kg/cni
It was set as G.

Next, the operating state when this plant is used as a mere power plant will be explained based on FIG. 3.

As shown by the thick line in the figure, the combustion gas (G) generated in the boiler 5 is released through the opening/closing flange 6 because the first valve γ is closed and the opening/closing flange 6 is open.

This release may be released into the atmosphere or into the next treatment plant (desulfurization,
It may be a denitrification device, etc.).

Water (H
2O) is heated in the economizer 18 in the boiler 5 and evaporates through the bypass line 24 since the first control valve 19 and the third valve 20 are closed and the second control valve 23 is open. section 21, a superheater 22, and then sent to a steam turbine 25.

A portion of the steam N sent to the steam turbine 25 is extracted and used for heating the deaerator 11, and the majority is returned to the deaerator 11 via the condenser 28 after generating power.

As described above, according to the present invention, the following effects can be expected.

A. In conventional methanol production plants, only heat recovery was performed using a waste heat boiler, and most of the power for the process was supplied from other power plants, but according to the present invention, steam turbines and gas turbines This allows extremely large amounts of power to be generated with extremely high efficiency, and the output of these turbines not only makes it possible to replace process power, but also allows surplus power to be supplied to other plants.

Note that the depressurization and condensation process requires two lines: a steam line and a methanol gas line, but since the steam line does not contain H2 and CO2 gas, which cannot be condensed, the turbine back pressure cannot be sufficiently lowered. , it is advantageous to ensure the thermal efficiency of a normal power plant.

B0 According to the present invention, a large amount of high-purity carbon dioxide gas can be obtained,
Therefore, by receiving hydrogen gas from another process, raw material gas for synthesis can be secured.

Therefore, it is possible to eliminate the need for reforming furnaces, which accounted for a large amount of cost in conventional methanol plants.
The initial cost and operating cost of the plant can be reduced.

C. Since water is produced by the methanol synthesis reaction, in addition to recovering water from boiler exhaust gas, water other than that used in this plant can be taken out as surplus and used in other plants, thus making it possible to produce water. You can also expect good results.

For example, when boiler steam and synthesis gas are combined, the concentration of the methanol aqueous solution sent to the methanol stripper will inevitably be lower, but according to the present invention, the power plant line and the synthesis gas line are independent. Therefore, the concentration of the methanol aqueous solution can be increased.

Since it is possible to operate the heating side (synthesis gas side) and heat receiving side (boiler water side) of the E0 synthesis tower at equal pressure, only the outer panels of the synthesis tower (body plate, head plate, etc.) can have pressure resistance. The production cost is lower than that of conventional synthesis towers.

F. As shown in the example, if the line to the synthesis tower is closed, the boiler water is bypassed, and the exhaust gas from the boiler is released from before the exhaust gas cooler, it can be operated as a simple power plant. The switching operation is also extremely simple.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a flow sheet for a methanol production system, FIG. 2 is a material balance sheet for the same, and FIG. 3 is a flow sheet for a power plant system. 1...Natural gas, 5...Boiler, 9.
...Cooler, 10...Steam water separator, 11
--- Deaerator, 12 --- CO2 extractor, 15 --- Synthesis tower, 16 --- Catalyst layer,
22... Superheater, 24... Bypass line 25... Steam turbine 28...
・Condenser, 29...Gas turbine 30...
...Condenser, 35...Methanol stripper.

Claims (1)

[Claims] 1 Natural gas, methane gas, etc. are combusted in a boiler, the generated combustion gas is cooled, moisture is removed, carbon dioxide is extracted from this combustion gas, hydrogen gas is added to it, and this raw material gas is is guided into the synthesis tower and subjected to a synthesis reaction while being cooled in a non-contact manner using the heat source medium taken out from the boiler.The vaporized methanol from the synthesis tower is passed through a gas turbine and then flowed to the liquefaction section. is a methanol production method characterized by introducing the methanol into a boiler again to generate steam, and passing this steam through a steam turbine.