SU47633A1 - Method of converting carbon monoxide to dioxide - Google Patents

Description

The conversion of carbon monoxide or gases containing carbon monoxide to dioxide, in the presence of water vapor, must, in the form of the final product, according to

СО + СОЗ + Na + 10400 cal., (The so-called equilibrium of water gas), to produce carbon dioxide and hydrogen. The equilibrium constant values are known for temperatures in the region from 300 to 1000 °. Of these values, it is clear that at lower temperatures, the most unchanged components and parts of an equilibrium water gas are carbon dioxide | and hydrogen, at higher temperatures — carbon monoxide and water vapor. Technique has therefore always strived to choose the conversion temperature that could be lower if hydrogen extraction was required. In view of the fact that, with decreasing temperature, the establishment of equilibrium slows down more and more until it stops, it is necessary to accelerate the reaction with the help of catalysts. However, in this way too, it has been possible in large-scale industry to reach lower limits than about 400 °, at which approximately 10% of carbon monoxide continues to remain in equilibrium. Here is

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The reason why, along with the use of catalysts, which exclusively achieved the acceleration of equilibrium, went to: a shift in the equilibrium position itself, i.e., a change in the percentage ratio of equilibrium substances involved in the reaction. This goal is achieved by treating carbon monoxide with large amounts of water vapor. If, however, we set ourselves the task of reducing the carbon monoxide content in such a way that only insignificant quantities of it remained unchanged in the state of equilibrium, even at relatively low temperatures would such an excess of water vapor be required that this method would be unsuitable for purely economic reasons. Considerations m. Another way is to shift the state of equilibrium in such a way that it lowers the carbon dioxide tension. In the known methods of this kind, carbon dioxide is gradually displaced from. balance by combining it with lime. Also, in such a treatment, the catalytic acceleration of the reaction is mainly used, namely, iron-type catalysts were previously used in particular. Afterwards;

it has been proposed to use, as a catalyst, magnesium oxide. When performing this method, kilns filled with dolomite are used in practice. Thus, it comes to the same residual amount of carbon monoxide with a smaller excess of water, in comparison with the theoretically required amount, as if the treatment was carried out without absorbing carbon dioxide, with a large excess of steam. However, with such methods, lime or lime containing in dolomite takes part in the reaction in stoichiometric quantities, as a result of which carbonate lime between the two gas generation periods must be calcined so as to regenerate calcium oxide and cool the furnace to a temperature pe, stock In this state of the art, the inventor of this method introduced a group of catalysts for catalytic oxide-water gas, consisting of a mixture of magnesium oxide and an alkali carbonate and carbon. By using these highly active catalysts, especially those suitable for transforming CVDs with water vapor, a positive position can be achieved - equilibrium up to temperature regions in which cost-effective excess water vapor is sufficient to reduce the CO content to satisfactory for many needs. When using these catalysts, lowering the carbon dioxide voltage, by continuously removing it with the help of its bonding agents, is superfluous. It can be considered that the coal contained in the catalyst does not produce this action, since carbon-containing catalysts are not applicable to continuous production without periodic regeneration or without coal feed.

According to the invention, the conversion of carbon monoxide with steam, using a mixture of magnesium oxide and carbon, and especially potassium carbonate as a catalyst, is produced under pressure above the atmosphere.

Since the reaction of the aqueous gas is carried out in both directions without changing the number of molecules and the volume, the equilibrium remains independent of pressure. Nevertheless, in order to save space and water vapor, the technology has already been converted to carbon monoxide with water vapor under pressure from 4 to 40 atm. and above (Germ, patent number 271516).

In this way, a corresponding decrease in the volume of gas, inversely proportional to pressure, is achieved, which means that at a pressure of about 5-1 / 5 atm. With equal capacity, the outgoing gas thus remains five times longer in contact with the catalyst than to achieve full equilibrium at lower temperatures and with the available equipment; chemical turnover per unit of time increases.

Along with the advantages of using pressure, there are, however, with a treatment process with known catalysts, and quite large disadvantages.

First of all, carburization, according to the equation 2Cb C - - CO, increases with increasing pressure. Since the two volumes of the initial gas are transferred to one volume of the final gas, this reaction depends in the sense of pressure, that with an increase in it the formation of carbon increases. In fact, if carbon monoxide conversion in the presence of water vapor is performed using iron-group catalysts at low temperatures under pressure above the atmosphere, carbon emissions become so significant that the gas paths become clogged in the shortest time and the catalyst becomes unsuitable. In contrast, with the addition of catalysts for the compound MgO- | -carbonic alkali - | -C, even at favorable temperatures for converting CO to COj and HZ, carburization does not take place even when the treatment is performed at a pressure above the atmosphere. The reaction process + CO2 from left to right is practically delayed by the fact that carbon

is already in the contact mass.

Further increase in pressure favors the formation of methane. As with the direct synthesis of jis of hydrogen and carbon monoxide, methane is formed in the synthesis of hydrogen and carbon dioxide with a decrease in volume. As a result of the increase in pressure, one should theoretically expect: an equilibrium shift in favor of methane formation. Methane is actually formed by a catalytic process of water gas using metal catalysts within temperatures that are favorable for converting carbon monoxide to COg and Hj, if this conversion is carried out under pressure. Surprisingly, however, this disadvantage is almost paralyzed with the use of the aforementioned mixed catalysts. So, for example, pressure at 4-6 atm. Methane iK is formed even at temperatures below 400 ° C as long as the temperature in the catalyst remains constant. Thus, due to the joint action of special catalysts and the pressure above the atmosphere, with the formation of carbon monoxide in the presence of water vapor, it was possible to obtain a technical result that has not been achieved so far. Plains), due to this combination, it will be possible to fully utilize the special properties of the mentioned 1 catalysts, which make it possible to achieve complete equilibrium even at temperatures below 400 ° and 380 ° in that the inevitable reduction in speed is balanced by an increase in pressure. If, thus, even a small part of the conversion is carried out within the temperature range favorable to the equilibrium of the water gas, i.e. with the greatest economy in terms of the demand for water vapor, then optimal results are obtained. For this purpose, it is recommended to convert into two (or several) work shifts, of which the first takes place within the temperature range of 400-500 °, the second (or last) within 400-320 On large installations it is more advantageous to perform this conversion in two or more steps with the use of special koi. tact furnaces for each of the gudeans with intermediately switched on apparatus for the exchange of heat. Thus, it is possible to use the catalyzed gas mixture exhaust gas from the first contact furnace (or first contact furnaces) to heat the initial source gases instead of losing it to the lowest reaction temperature due to the increasing cooling of individual furnaces to the lowest reaction temperature. form of radiant heat.

In the drawing, for example, a plant is schematically depicted for performing the method.

The collecting tank, from which the source gas, approximately water gas, is led through the compressor 2 to the injection tower 5 filled with Raschig rings so that heat transfer devices 4 to 5 can be passed through pipe 10 with steam. Heated to the appropriate temperature, the mixture from water gas with steam passes into contact furnace 6, where the first conversion takes place at temperatures between 400-500 °. In this case, the catalyst is caustically calcined magnesite and finely ground calcined potassium carbonate in ratios 3: 1 to 5: 1, with 3 to 5 parts of charcoal per part of this mixture. This mixture, in a finely milled state with a watery asphalt emulsion, forms in a granular form and is heated in an airless space to 600-800. Then, the resulting mixture is exposed to steam so that 1.5-2 volume parts of water vapor fall on each volume part of the carbon monoxide of the source gas, and put this mixture on top of the furnace 6 with such a temperature that the contact mass, due to the exothermic reaction, is heated up to 500 °. The catalyzed gas mixture emerging from the bottom of the contact furnace 6 is passed through a heat exchanger 5, where it is cooled to the temperature at which it passes through the countercurrent to the top gas supplied from above.

must enter the second contact furnace 7 in order for the contact mass to reach the final one; temperatures in 320. From here, the catalyzed gas mixture, freed from carbon monoxide to the smallest residue, is passed through a heat exchanger 4, which it passes in countercurrent to the output gas, and then into a cooling tower 8 filled with Raschig rings, where excess water vapor condenses by spraying cooling water. Depending on the working pressure, water is obtained at a temperature of from 120 to 180 °. This hot water is pumped by pump 9 onto the spray tower 3, in which the outgoing gas is pre-saturated with water so that only a fraction of the water vapor required for the conversion must be additionally carried to the JO pipeline. Hot, pressurized water flowing from condenser 8 can also be reduced in pressure and consumed.

steam, either for gas water generators or as feed water for steam boilers. All equipment is under pressure above the atmosphere from about 1 to 20 atm., Mostly from 6 to 7 atm.

The subject matter of the invention.

1. A method for converting carbon monoxide or gas mixtures containing carbon monoxide to dioxide in the presence of water vapor, characterized in that the conversion is performed under pressure over the atmosphere at temperatures below 500 ° C using a catalyst consisting of magnesium oxide, carbon and carbon dioxide alkali, especially potassium carbonate.

2. A method according to claim 1, characterized in that the conversion is performed in several processing degrees, i3f of which in the first process is carried out in the former temperatures between 400 and 500 in the second (or last) within 400 to 320 °.