JPS6131053B2 - - Google Patents

Description

[Detailed description of the invention]

In the present invention, hydrocarbons are partially oxidized in a partial oxidation furnace using carbon dioxide as a furnace temperature adjusting agent to produce a mixed gas containing carbon monoxide and hydrogen as main components, and this mixed gas is used to produce, for example, alkyl Reactions that mainly use carbon monoxide as a raw material for synthesis, such as reactions that synthesize formamides by reacting amines or ammonia with carbon monoxide, or reactions that synthesize acetic acid by reacting methanol and carbon monoxide, are carried out. The present invention relates to a method for preparing carbon monoxide for use as a raw material for synthesis, which is prepared so as to prevent excess hydrogen from being co-produced, and which enables industrially advantageous synthesis reactions. Generally, carbon monoxide for use as a raw material for synthesis is produced by a method in which coke is oxidized at a high temperature, a method in which a gas obtained by catalytic reforming or partial oxidation of hydrocarbons is cryogenically separated, and the like. Since the high-temperature coke oxidation method requires high-grade coke and has many problems in terms of pollution, recently, methods using catalytic reforming of hydrocarbons or partial oxidation have been adopted in many fields. It has reached this point. In the partial oxidation method of hydrocarbons, hydrogen is also produced at the same time as carbon monoxide. On the other hand, in actual industrial situations, it is rare that the carbon monoxide and hydrogen that are obtained have a consumption sector that is commensurate with the amount of production, and in most cases, the demand is unbalanced. If demand is biased toward hydrogen, it is easy to deal with excess carbon monoxide because it can be easily converted to hydrogen, but on the other hand, if only carbon monoxide is required, excess hydrogen is They are forced to live in an uneconomical situation where they only need fuel. One way to avoid this uneconomical problem is to use carbon dioxide instead of steam as a furnace temperature regulator in the partial oxidation of hydrocarbons to improve the ratio of carbon monoxide to hydrogen in the produced gas. However, there are limits to this, and it is impossible to completely eliminate hydrogen production. The present invention applies such excess hydrogen to a synthesis reaction as a mixed gas without separating it by means such as cryogenic separation, and unreacted hydrogen (sometimes containing carbon monoxide) in the reaction. By returning the gas to the partial oxidation furnace, it is possible to prevent excess hydrogen from being co-produced, and to carry out a synthesis reaction using only carbon monoxide as one of the synthetic raw materials, it is industrially advantageous. It is something to consider. In addition, this preparation allows unreacted gas (tail gas) to be effectively utilized without being discharged outside the system, thereby providing a substantially closed synthesis reaction system. The present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a series of processes in which a mixed gas of carbon monoxide and hydrogen is produced by conventional partial oxidation, and a synthesis reaction is performed using the mixed gas. Hydrocarbons as a gasification raw material or a mixture thereof with a carbonaceous substance are introduced into a partial oxidation furnace 4 through a conduit 1, and water vapor and/or carbon dioxide as a temperature adjusting agent are introduced through a conduit 3. Hydrocarbons are decomposed and gasified in the partial oxidation furnace 4 by oxygen and/or air introduced from the conduit 2. The generated crude gas mainly composed of carbon monoxide and hydrogen is taken out through a conduit 5 and guided to a purification device 6. In the purification device 6, waste heat is recovered and impurities such as free carbon, moisture, and acid gas are removed, and the waste heat is sent via a conduit 7 to a reaction device 8, which uses carbon monoxide as one of the raw materials for synthesis. The carbon monoxide reacts in the reactor 8, and the tail gas consisting of unreacted carbon monoxide and/or hydrogen is taken out through the conduit 9 and led to another treatment or combustion device. In this method, the tail gas is advantageously used when there is a demand for hydrogen, but when there is no corresponding demand, the tail gas can only be used as fuel, which is extremely uneconomical. In contrast, the method of the present invention is as shown in FIG. Compared to the conventional method shown in Figure 1, this method has (i)
(ii) the tail gas from the reactor 8 is returned to the partial oxidation furnace 4 via the conduit 9; (iii) it is necessary The carbon dioxide separated by the purification device 6 is guided to the conduit 3 through the conduit 10 according to the requirements, thereby reducing the amount of carbon dioxide introduced from the outside. By returning the tail gas from the reactor 8 to the partial oxidation furnace 4, the method of the invention introduces the hydrogen contained in the gas into the already formed high temperature atmosphere as a furnace temperature regulator. It is intended to act on the carbon dioxide present in the water to cause a reverse aqueous reaction and produce carbon monoxide. In other words, hydrogen is used to reduce carbon dioxide to carbon monoxide, making it possible to reduce the amount of hydrocarbons supplied to the partial oxidation furnace as a raw material for carbon monoxide, and also to reduce the amount of hydrocarbons supplied to the partial oxidation furnace as a raw material for carbon monoxide. Eliminates economic considerations and is used effectively. Therefore, carbon dioxide is used as the furnace temperature adjusting agent in the partial oxidation furnace 4 without using steam, and therefore, the gas taken out from the partial oxidation furnace 4 also contains unreacted carbon dioxide, so it is difficult to purify it. The device 6 separates carbon dioxide. The separated carbon dioxide is recycled via conduit 10 to carbon dioxide conduit 3 as required. This allows for a highly efficient system in which a mixed gas of carbon monoxide and hydrogen is obtained using a partial oxidation furnace that uses hydrocarbons as raw materials, but the system as a whole produces only carbon monoxide. Moreover, it is a substantially closed method. in this case,
A mixture of hydrocarbons and carbonaceous substances can also be used as the raw material. The method of the present invention can be applied to the case where formamides are synthesized by reacting an alkylamine or ammonia with carbon monoxide. It can also be applied to the synthesis of acetic acid by reacting methanol with carbon monoxide. Furthermore, even if both carbon monoxide and hydrogen are consumed as synthesis raw materials, the method of the present invention is effective for reactions in which the amount of hydrogen in the tail gas is greater than that of carbon monoxide. That is,
In this type of synthesis reaction, a method is often adopted in which the unreacted gas is circulated within the synthesis system, but some of it is circulated outside the synthesis system due to the hydrogen that accumulates after several cycles. The tail gas that is emitted cannot be highly evaluated. Even in such a case, if the method of the present invention in which the tail gas is circulated back to the partial oxidation furnace is applied, all the effects described above can be expected. Examples of this type of reaction system include Retzpe reaction (synthesis of butanol, etc.), oxo reaction (synthesis of butyraldehyde, etc.), and the like. The synthesis of the above-mentioned formamides will be explained below using dimethyl formamide as an example. When dimethylamine is reacted with carbon monoxide,
Dimethylformamide is produced by the formula ( _CH3 ) _2NH +CO→( _CH3 ) ₂ -N-COH. This reaction occurs when carbon monoxide is absorbed by dimethylamine, which forms a liquid phase.The concentration of carbon monoxide is not dominant, and hydrogen is inert, so it is not only possible to mix it in. Rather, it has the beneficial function of promoting the dispersion of carbon monoxide, which is a raw material for the reaction. Therefore, the mixed gas of carbon monoxide and hydrogen purified in the purification device can be introduced into the reaction device as it is without separating the hydrogen, and it is preferable to do so. After dimethylformamide is synthesized in this way, the unreacted gas discharged from the reactor is a hydrogen-rich mixture of carbon monoxide and hydrogen, and if this mixture is returned to the partial oxidation furnace, the aforementioned A similar effect can be obtained. Operating conditions for producing dimethylformamide in three methods: the method of the present invention, the conventional method, and the method of using steam as the furnace temperature regulator and returning the tail gas to the partial oxidation furnace. A comparison of the originals is shown in Table 1. (The amount of dimethyl formamide produced as a result of the reaction was all the same, 1000 kg. All conditions such as operating pressure and temperature were set to be the same.)

[Table] As is clear from this table, when the conventional method and the method of the present invention are compared to produce the same amount of dimethylformamide, the main raw materials, hydrocarbon and oxygen, are reduced to 45% and 59%, respectively. The savings and at the same time the amount of gas generated, which determines the size of the device, is reduced by up to 70%, making the process of the invention much more economically advantageous. In the reference method of circulating tail gas while using steam as a furnace temperature regulator, the partial pressure of carbon monoxide in the purified gas decreases significantly (with a composition of CO25.6 Vol.
%), there are many inconveniences in reality, such as the need to raise the dimethylformamide synthesis pressure to twice the normal pressure to compensate, but the values here are calculated assuming that everything can be operated ideally. Ta. At this time, the feedstock oil will drop to 77%, but the oxygen will increase by 19%,
This reduces the advantage, and furthermore, when it comes to generated gas,
This is a 69% increase, making it clear that the series of devices will become larger. As described above, according to the method of the present invention, valuable hydrocarbons and oxygen can be significantly saved, and the amount of generated gas and tail gas emissions is also extremely reduced, so the equipment required for this can be downsized. It will be done. Furthermore, hydrogen gas can be effectively used to generate carbon monoxide, and surplus hydrogen is not co-produced.
It has excellent effects. Example Synthesis gas production equipment includes a hollow partial oxidation furnace whose inner surface is protected with refractory material, a water scrubber and packed tower type trap for removing carbon, a gas cooler,
A series of pressurized water decarboxylation equipment was used. The carbon dioxide taken out of the system by the decarboxylation equipment and flashed was allowed to pass through a dry desulfurization equipment and then mixed with the raw material carbon dioxide. A hollow gas-liquid contact reaction tower was used as a device for consuming carbon monoxide in the synthesis gas. Dimethylamine and a catalyst were pressurized into the reactor using a pump, and the unreacted dimethylamine was vaporized and reached the reflux condenser together with the unreacted gas, where it was reliquefied and returned to the bottom of the reaction tower. Furthermore, the amount of dimethylamine supplied can be increased or decreased depending on the load on the reflux condenser. The non-condensable gas (unreacted carbon monoxide and/or hydrogen, etc.) in the reflux condenser was designed to be able to be mixed with carbon dioxide, which is one of the raw materials for gasification. The operational results of dimethylformamide synthesis using the above-mentioned apparatus in a partial oxidation furnace using carbon dioxide gas as a furnace temperature adjusting agent and generated synthesis gas are as follows. 1 Gasification raw materials etc. Raw material hydrocarbon oil 1Kg/H Specific gravity: 0.923, Calorific value: 10200kcal/
Kg, Composition: 90.4% by weight of carbon, 9.5% by weight of hydrogen, 0.04% by weight of sulfur, Pressure: 45Kg/cm ² G, Preheating temperature: 325℃ Oxygen 1.088Nm ³ /H Purity: 99.6% by volume Pressure: 45Kg/cm ² G, preheating temperature; 125℃ Carbon dioxide 1.631Nm ³ /H (as 100%)
(Including decarbonation system circulating gas) Purity: 81.3% by volume, other H ₂ , CO, etc. Pressure: 45Kg/cm ² G, preheating temperature: 425℃ Reaction system return gas 1.434Nm ³ /H Composition: CO3 3.4% by volume , H ₂ 65.0% by volume, Argon, CH ₄ 2.6% by volume Pressure: 45Kg/cm ² G, preheating temperature: 425℃ 2 Gasification conditions, etc. Gasification conditions Pressure: 30Kg/cm ^2G , Temperature: 1150℃ Generated gas 6.24 Nm ³ /H composition; CO47.2% by volume, CO ₂ 17.8% by volume, H ₂ 18.1% by volume, residual moisture, etc. Purified synthesis gas 3.751Nm ³ /H composition; CO71.4% by volume, H ₂ 27.4% by volume, Ar CH ₄ 1.2% by volume 3 Dimethylformamide synthesis conditions, etc. Synthesis conditions Pressure: 20Kg/cm ² G, temperature: 120°C Raw material dimethylamine 4.283Kg/H Pressure: 20Kg/cm ² G, temperature 25°C Amount of dimethylformamide produced 6.835Kg/H (after purification) Tail gas 1.606Nm ³ /H Composition: CO3 3.4% by volume, H ₂ 64.0% by volume, Ar/CH ₄ 2.6% by volume Disposal of tail gas 89.3% is recycled to the gasification system These results Dimethylformamide production amount
The amount converted to 1000 kg is listed in the second column of Table 1. Comparative Example 1 Using exactly the same series of equipment as in the example, but
Instead of using carbon dioxide as a temperature regulator during gasification, steam is used as before, and both the carbon dioxide flashed in the decarboxylation system and the tail gas from the dimethylformamide synthesis system are not returned to the partial oxidation furnace, but are sent outside the system. The results of each section were as follows when the operating conditions were set using the same amount of raw oil as in the example by purging (once-through operation). 1 Gasification raw materials, etc. Feedstock hydrocarbon oil 1Kg/H or less Same as in Examples Oxygen 0.840Nm ³ /H Water vapor 0.992Kg/H Reaction system return gas None 2 Gasification conditions, etc. Gasification conditions Same as in Examples Generated gas 4.039Nm ³ /H Composition; CO3 3.1% by volume, CO ₂ 8.5% by volume, H ₂ 36.4% by volume, residual moisture, etc. Purified synthesis gas 2.556Nm ³ /H Composition; CO47.6% by volume, H ₂ 52.2% by volume, Ar/CH ₄ 0.1% by volume 3 Dimethylformamide synthesis conditions, etc. Synthesis conditions Same as in Example Raw material dimethylamine 1.945Kg Dimethylformamide production amount 3.14
Kg/H (after purification) Tail gas 1.579Nm ³ /H Composition: CO15.4% by volume, _H2 84.3% by volume, Ar・CH4 _0.3 % by volume Disposal of tail gas Extract the entire amount from the system (separately incinerated) This example This corresponds to a method in which synthesis gas is also obtained by conventional general partial oxidation methods, and then carbon monoxide is digested in a once-through manner. This was converted into 1 kg/H of purified dimethyl formamide and is listed in the first column of Table 1.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a conventional method for preparing carbon monoxide, and FIG. 2 is an explanatory diagram of a method for preparing carbon monoxide according to the present invention. In the figure, 1 is a conduit for gasification raw materials, 2 is a conduit for oxygen or air, 3 is a conduit for steam or carbon dioxide, 4 is a partial oxidation furnace, 5 is a conduit for substances whose main components are carbon monoxide and hydrogen,
6 is a purification device, 7 is a conduit, 8 is a reaction device, 9 is a tail gas conduit, and 10 is a carbon dioxide conduit.

Claims (1)

[Claims] 1. In a partial oxidation furnace that uses carbon dioxide as a furnace temperature regulator, hydrocarbons are partially oxidized to produce a mixed gas containing carbon monoxide and hydrogen as main components, and the mixed gas or A mixed gas of carbon monoxide and hydrogen, from which free carbon, moisture, carbon dioxide, etc. have been removed, is introduced into a synthesis reaction apparatus that uses carbon monoxide as a raw material for synthesis reaction, and is reacted with the unreacted hydrogen in the reaction. A method for preparing carbon monoxide for use as a synthetic raw material, characterized in that a gas rich in carbon monoxide is returned to the partial oxidation furnace. 2. The method for preparing carbon monoxide for use as a raw material for synthesis according to claim 1, wherein the synthesis reaction apparatus is a reaction apparatus for reacting carbon monoxide with an alkylamine or ammonia to synthesize formamides. 3. The method for preparing carbon monoxide for use as a raw material for synthesis according to claim 1, wherein the synthesis reaction apparatus is a methanol method acetic acid synthesis apparatus. 4. The method for preparing carbon monoxide for synthetic raw materials according to claim 1, wherein the hydrocarbons to be partially oxidized in the partial oxidation furnace are hydrocarbons mixed with a carbon substance.