RU1807050C - Formaldehyde synthesis process control method - Google Patents

Abstract

Usage: relates to the field of process control, in particular to methods for controlling the process of formaldehyde synthesis. The essence of the method: according to the invention, they measure and stabilize the air flow rate of the additional flow supplied to the middle part of the contact layer of the synthesis apparatus and distributed over the section of the layer. 1 ill., 1 tab.

Description

The invention relates to the field of process control, in particular to methods for controlling the synthesis of formaldehyde and can be used in the chemical, petrochemical and other industries.

An object of the invention is to increase the yield of formaldehyde.

The drawing shows a schematic diagram of the control of the formaldehyde synthesis process that implements the proposed method.

A mixture of methanol and water and a main air stream are supplied to the alcohol evaporator 1 via pipelines. Air flow control main air flow. The flow rate control of the main stream is carried out by the air flow sensor 2, the flow rate control of the alcohol-water mixture is carried out by the flow sensor 3 of the alcohol-water mixture. The temperature sensor 4 shows the temperature in the alcohol evaporator 1. The alcohol-water-air mixture formed in the alcohol evaporator 1 is piped to the formaldehyde synthesis apparatus 5, where formaldehyde is synthesized on the contact layer 6. The temperature of the contact layer 6 is measured by the temperature sensor 7 and is regulated by the temperature controller 8, which changes the amount of methanol in water-air; the air mixture supplied to the synthesis apparatus 5 using the heating element 9. The air flow sensor 10 measures the flow rate of additional the air flow supplied to the middle part of the contact layer 6 of the synthesis apparatus 5 and distributed over the cross section of the layer, the air flow regulator 11 changes the degree of opening of the regulatory body 12 on the additional flow pipe zduha. The reacted gases from formaldehyde synthesis apparatus 5 are supplied via. labor. piping into the absorber 13, which receives water through another piping. The water flow rate is monitored by the water flow sensor 14. From the absorber 13, the exhaust gases are discharged through pipelines and the finished product, formE

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ling. The consumption of gases is measured by the sensor 15 of the consumption of gases, the analysis of their composition is carried out by the gas analyzer 16.

In order to experimentally verify the claimed control method at a pilot plant in the Central Laboratory of the Gubakhinsky Production Association, Methanol to the alcohol evaporator 1, a mixture of methanol and water in the ratio of 70:30 and a flow rate of cm3 / h and the main air flow with a constant throughout experience of expenses, 8 l / h. The flow rate of the main stream was monitored by the air flow sensor 2, the flow rate of the alcohol-water mixture was carried out by the flow sensor 3 of the alcohol-water mixture. The temperature sensor 4 showed the temperature in the alcohol evaporator 1 ТИП.180-190 ° С. The alcohol-water-air mixture formed in the alcohol evaporator 1 was fed through a pipeline to the synthesis apparatus 5, where on the contact layer 6, consisting of pumice-silver catalyst granules and having 12 cm high, formaldehyde was synthesized. In this case, both the process of methanol dehydrogenation and its oxidation by atmospheric oxygen took place:

CHzOH52. CH20 + H2-20 kcal (1) CHzOH + 0.5 02-CH20 + H20 + 38 kcal (2) Adverse reactions also occurred simultaneously with the main formaldehyde formation reactions. H2 + 0.5 02 ± H20 (3) CH2OH + 1.502 - CO2 + 2H20 (4). NSON -. СО + Н2 (5) 2НСОН + 02 - 2НССУ (6) СНзОН + Н2 СН4 + Н20 (7) The temperature of the contact layer 6 was measured by a temperature sensor 7 Тк.с. 600-640 ° С and was regulated by a temperature controller 8, which changes l the amount of methanol in the alcohol-water-air mixture supplied to the synthesis apparatus 5 using the heating element 9. If the temperature of the contact layer 6 deviates from the set value, the heating of the alcohol-water mixture in the alcohol evaporator 1 increases, as a result, the amount of evaporated methanol increases, this caused an increase in de hydrogenation (1), and, consequently, a decrease in the temperature of the contact layer 6 to a predetermined value. With a negative deviation of the temperature of the contact layer 6 from the set value, the heating of the alcohol-water mixture in the alcohol evaporator 1 decreased, as a result, the amount of evaporated methanol decreased, this weakened the dehydrogenation reaction (1) and, as a result, the temperature of the contact layer 6 increased to the set value. The air flow rate sensor 10 measured the flow rate of an additional air flow of 0. 0. 0-28.5 l / h (0-7.75% of OV) supplied to the middle part of the contact layer 6 of the synthesis apparatus 5 and distributed over the section of the layer. The introduction of an additional air flow divides the contact layer 6 into the upper (c, el.) And lower (n.a.s.). The height of the upper layer was LB.cn.1 cm, the lower needle was 5 cm. In order to determine the specific values of formaldehyde yield at

5 different flow rates of the additional air flow changed the task of the regulator 11 of the air flow: experiments 1-3 l / h; Odogt experiments 17.3 l / h; experiments 7-9 l / h; experiments 10-12, 5 l / h. The regulator 11 pzc0 of the air flow maintained the value of the flow rate of the additional air flow at a given level by changing the degree of opening of the regulating body 12 on the pipeline of the additional air flow. With a positive deviation of the air flow of the additional flow from the set value, the degree of opening of the regulating organ 12 decreased, while with a negative deviation the degree of opening of the regulating organ 12 increased. The reacted gases from the formaldehyde synthesis apparatus 5 were fed through a pipe to an absorber 13, into which an other pipe was supplied

5 water with a flow rate of cm3 / h, Consumption

water was controlled by the flow sensor 14

water. From the absorber 13 through pipelines

; formalin-alcohol solution was removed

formaldehyde and gases, the consumption of which

0 were measured with a Qa.r.360-410 l / h gas flow sensor 15. The analysis of gases for the content of CO2, CO, H2, 02 and N2 was carried out by a gas analyzer 16. The amount of each of the components in the gases was calculated from the consumption of the gases and their composition. Using the stoichiometric reaction ratios (1-7), the amount of reacted methanol and the amount of methanol that went into the formation of formaldehyde were calculated.

0 Based on the readings of the sensor 3 of the flow rate of the alcohol – water mixture and the known methanol – water ratio (70:30) and methanol density (, 87 g / cm), the total amount of methanol passed through the unit was determined. Further, the indicators of the formaldehyde synthesis process were determined: the total conversion of methanol as the ratio of the amount of reacted methanol to the amount of methanol passed, the yield of formaldehyde (or useful conversion

methanol) as the ratio of the amount of methanol spent on the formation of formaldehyde to the amount missed, methanol and selectivity as the ratio of the yield of formaldehyde to the total conversion. The experimental data and calculated indicators of the formaldehyde synthesis process are presented in the table.

Using the proposed method for controlling the process of formaldehyde synthesis, it is possible to increase the overall conversion and yield of formaldehyde by 3-5%, while maintaining selectivity unchanged. In addition, due to a decrease in the temperature of the contact layer, the range of the catalyst increases.

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Claims (1)

SUMMARY OF THE INVENTION A method for controlling the process of formaldehyde synthesis by oxidation of methanol on a pumice-silver catalyst by controlling the temperature of the contact layer of the synthesis apparatus by changing the amount of methanol in the alcohol-water-air mixture supplied to the synthesis apparatus at a constant flow rate of the main stream air. characterized in that, in order to increase the yield of formaldehyde, an additional air stream is supplied to the middle part of the contact layer of the synthesis apparatus, distributed over the section of the layer, the air flow rate of the additional stream is measured and stabilized. alcohol- ioghc- 4o atfyti. H&S