JPS59128202A - Method for reforming methanol while recycling purge gas - Google Patents

Abstract

PURPOSE:To improve the yield of hydrogen and to stabilize the operation of a crude hydrogen generating section by blowing hydrogen-rich purge gas from units for purifying hydrogen by pressure swing adsorption into a gas mixing nozzle before the methanol-water evaporator of the hydrogen generating section. CONSTITUTION:The pressures of methanol 1 as a starting material, water 2 and a condensate 15 are increased with pumps, and they are mixed in a pipe, preheated to a temp. below the evaporating temp. with a preheater 4, and fed to a mixer 5, where the mixture is mixed with purge gas recovered from units 10 for purifying gaseous H2 by pressure swing adsorption. The resulting liq. mixture contg. methanol mixed well with water is evaporated in an evaporator 6, heated to the reaction temp., and introduced into a reformer 7 to produce crude gaseous hydrogen contg. CO2, CO, moisture and a little methanol. This reformed gas is cooled with the preheater 4 and a gas cooler 8, and moisture and methanol are separated as a condensate with a separator 9. The remaining crude gaseous H2 is passed through the units 10 to increase the purity. Purge gas used in the regeneration of an adsorbent in each of the units 10 is stored once in a surge tank 12, compressed with a compressor 14, and blown from the nozzle of the mixer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing methanol-reformed hydrogen in which the scavenging gas of the PSA hydrogen purification unit is recycled to the crude hydrogen generation section, thereby achieving stable operation of the device and obtaining high-purity hydrogen at a high yield. Regarding.

Hydrogen production by steam reforming of methanol generally involves preheating a mixed solution of pure methanol solution, water, and condenser 1 with gas at the outlet of a reformer, and feeding it into an evaporator to evaporate methanol and water. This mixed gas of methanol vapor and steam is superheated and sent to a reactor, and a reforming reaction produces crude hydrogen containing 74% hydrogen (in dry components excluding water) and other carbon dioxide gas, steam, carbon oxide, etc. The gas is cooled, the water is separated as a condensate, and then passed through a PSA hydrogen purification unit to selectively adsorb and remove impurity components such as carbon dioxide, carbon oxide, trace amounts of Meknol, and water. Obtain high purity hydrogen.

In this method, JJX
The methanol and steam must be sufficiently mixed. That is, if a methanol solution, water, and condensate are simply mixed in a pipe and sent to an evaporator, bumping of methanol occurs in the evaporator due to the difference in boiling point of methanol and water, making it difficult to maintain stable operation. It is also difficult to maintain the mixing ratio of evaporated methanol vapor and steam at a constant value of 1.5 to 25, which is the appropriate molar ratio necessary for the reaction.

On the other hand, approximately 74% (in the dry component) of the crude hydrogen gas generated in the reforming reaction is passed through the PSA hydrogen purification unit to produce a 999%
In order to obtain the above-mentioned high-purity hydrogen, during regeneration of the adsorption tower, product hydrogen gas is fed from the bath outlet side after desorption under reduced pressure.
It is necessary to scavenge the inside of the tower.

Conventionally, a portion of the reduced pressure desorption gas and the scavenging gas were either completely released into the atmosphere as off-gas or sent to a fuel gas line. That is, since the hydrogen concentration in the off-gas is usually 40 to 50%, there is a loss of product hydrogen, and the product hydrogen yield (ratio of population to outlet hydrogen amount) of the PSA hydrogen purification equipment is 70% at the inlet hydrogen concentration.
-75%, it is usually about 75-80%. Therefore, in order to obtain the desired amount of product hydrogen, it is necessary to increase the amount of crude hydrogen gas supplied by 12 to 1.25 times, and this has been considered the only disadvantage of hydrogen purification by the PSA method.

The inventors of the present invention aimed to prevent bumping and stable operation of the evaporator.

In order to improve the hydrogen yield of hydrogen production equipment, as a result of various experimental studies, we installed a gas mixing device in the methanol water evaporator of the crude hydrogen generation section, and added a gas mixing device to the methanol water evaporator of the crude hydrogen generation section. By recovering the methanol, pressurizing it with Combuhinocer, and sending it to the mixing device, the mixing of raw methanol, water and condensate 1 is improved, bumping of the evaporator is prevented, and as a side effect, molar specific power of methanol vapor and steam;
It has been found that the operation of the crude hydrogen generating section becomes stable.

In this method, the entire hydrogen-rich scavenging gas in the PSA hydrogen purification unit off-gas is recycled and recovered before the reforming reactor, so the overall hydrogen yield is 10 to 1.
Improve by 5%.

Next, a method of implementing the present invention will be explained with reference to a flow sheet shown in FIG.

The raw materials methanol 1, water 2, and continsade 15 are each boosted in pressure by a pump, mixed in piping, and then preheated in a raw material preheater 4 to a pre-evaporation temperature. Next, it enters the mixing device 5, where the scavenging gas recovered from the PSA hydrogen purification unit is mixed. A sufficiently mixed solution of methanol and water is evaporated in the evaporator 6, and the methanol/steam molar ratio is 1.
．． It becomes vapor with a partial molar ratio of 5 to 25, and is heated to 1 reactor temperature, and about 74% of H2 (in the dry component) and other CO2, CO, moisture, and small amounts are generated by the reaction in front of the reforming reactor. Crude hydrogen gas consists of unreacted methanol. The reformed gas is cooled by a preheater 4 and a gas cooler 8, and moisture and a small amount of methanol are separated from condensate by a separator lake 9. Contin+-1 is combined with water, the raw material water, and recycled by a pump.

16 is a heat medium heater and an evaporator 6. This is the heat source for the reforming reactor 7.

Crude hydrogen gas with a hydrogen temperature of approximately 74% (in dry components) is passed through a normal PSA hydrogen purification unit 10 to obtain hydrogen with a purity of 999% or higher using the PSA method. Scavenging gas from the adsorption tower outlet due to product hydrogen during agent regeneration is stored in the surge pump 12, pressurized by the compressor 14, and blown through the nozzle of the methanol water mixing device 5, so that methanol and water' are sufficiently mixed, and at the same time. The scavenging gas from the PSA hydrogen purification unit 10 is recovered to the crude hydrogen generation section.

In FIG. 1, as an example, the scavenging gas is recovered to the crude hydrogen recovery section by feeding it into the mixing device 5 in front of the evaporator 6 in the middle of the raw material liquid pipe, but it is mixed directly to the bottom of the evaporator 6. Of course, this is also possible and the same effect can be obtained.

As explained in Section 2 below, the conventional method is carried out by blowing and recovering hydrogen scavenging gas from the PSA hydrogen purification unit into the nozzle of the mixing device for methanol, water and condensate in front of the methanol water evaporator in the crude hydrogen generation section. In addition to improving the hydrogen yield from 75 to 80% to more than 90%, it is also effective in stabilizing the operation of the reaction system.

[Brief explanation of drawings]

FIG. 1 shows a flow sheet of the method for producing methanol-reformed hydrogen by off-gas recycling according to the present invention. ■ = Raw material methanol 2: Water 3: Water tank 4: Raw material preheater 5: Missing device 6: Evaporator 7: Reforming reactor 8: Gas cooler 9: Separate lake - 10: PSA hydrogen purification unit 11: Product high purity hydrogen 12: Scavenging gas surge tank 13: Off-gas fuel surge tank 14: Compressor 15: Condensate 16: Heat medium heater 17: Fuel Patent applicant Shiroo Sano, representative of Nihon Kagaku Gijutsu Co., Ltd. 1 Figure

Claims (1)

[Claims] Pressure swing adsorption (hereinafter referred to as PSA) recovers ice-rich scavenging gas from the hydrogen purification unit, and collects methanol and water at the inlet of the methanol water evaporator in the crude hydrogen generation section. A method for producing methanol-reformed hydrogen by recycling scavenging gas, the method comprising blowing into a mixed liquid pipe or a mixing nozzle provided in the evaporator.