RU2258691C1 - Method for preparing methanol - Google Patents

Abstract

FIELD: organic chemistry, chemical technology.

SUBSTANCE: method for synthesis of methanol involves the following stages: removing hydrocarbon gas to be processed, sulfur elimination, catalytic steam conversion to obtain converted gas, heat utilization with separation of water, synthesis of methanol and separation of condensed methanol. Hydrocarbon gas with unstable composition is removed under pressure 0.001 MPa, not less, and sulfur elimination of hydrocarbon gas with unstable composition is combined with stage of step-by-step stabilization of pressure to form steam-gaseous mixture. Methanol synthesis is carried out for at least two successive flow steps with reducing volume of catalyst under pressure 1.5 MPA, not less, and separation of methanol between successive stages. Method provides significant reducing cost of gas processing and service of devices and allows carrying out the processing in mobile traveling devices in field conditions. Invention can be used in processing gas with unstable composition, for example, casing-head petroleum gas in petroleum-extracting holes, in field conditions in small traveling devices.

EFFECT: improved preparing method.

2 cl, 2 dwg

Description

The invention relates to the field of chemical technology and can be used in the processing of gas of an unstable composition, such as, for example, associated petroleum gas in oil wells, in the field with small mobile units.

From the information published in the patent literature, no technical solutions have been identified aimed at processing associated gas or gas with an unstable composition to produce methanol.

Known methods of processing natural gas to produce methanol. From these methods it is known that the processing of natural gas is carried out under high pressure, with which gas enters the processing plants along the pipelines. In addition, the necessary condition for the implementation of known methods are stringent requirements for the composition of the gas, as well as the synthesis of methanol at high (up to 7.0-10.0 MPa) pressure, which is achieved by the use of powerful and expensive compressors at stationary installations of chemical and oil refineries .

Currently, there is the problem of processing associated petroleum gases, as well as gases from new fields with an unstable gas composition that does not meet the requirements of GOST. According to existing technologies, such gases are either flared, which is harmful to the environment and negatively affects the environment, or there is a need to lay pipelines to existing gas pipelines or to the nearest processing plant. At the same time, during transportation through gas pipelines, part of the hydrocarbons of the transported gas necessary for processing is lost as a result of multistage compression and sequential cooling cycles when overcoming the hydraulic resistance of the long routes of gas pipelines, since their content in a gas with an unstable composition is too small. Thus, the costs of constructing gas pipelines and transporting gas from the field to processing plants are not justified.

A known method of producing methanol from synthesis gas, comprising two stages of methanol synthesis at elevated temperature and pressure, where in the first stage the synthesis is carried out in a flow reactor, and in the second stage in a reactor with recycling, when supplied to the second stage, they are added to the gas supplied to the second stage, an additional gas stream containing an excess of hydrogen or carbon oxides to control the volumetric ratio of CO / (H ₂ + CO ₂ ). This method also includes the stage of preliminary reduction of carbon monoxide from dioxide in additional reactors (RF patent No. 2052444, C 07 C 31/04, 1996).

The disadvantage of this method is significant energy consumption, including an increase in energy consumption for the oxide reduction process, as well as the need to use compressors to achieve a given pressure on the synthesis operation, requiring constant monitoring and care.

A known method of processing natural gas to produce methanol, including the vapor-oxygen conversion of natural gas to produce synthesis gas, heat recovery, partial removal of carbon dioxide from synthesis gas, drying, compression to a pressure of 8.5-9.0 MPa and the synthesis of methanol in two steps - preliminary flow under pressure of steam-oxygen conversion and the main circulation (RF patent No. 2135454, IPC 6 C 07 C 31/04, 1999).

The disadvantage of this method is the use of steam-oxygen conversion, which requires large costs to ensure the safety of the process, as well as the need to remove excessively formed carbon dioxide, which entails significant energy costs. To implement this method requires expensive and high-precision equipment, such as compressors.

A known method of producing methanol, including the vapor-oxygen conversion of natural gas, the allocation of part of carbon dioxide from the converted gas, followed by drying and compression to a pressure of 8.5 to 9.5 MPa and the synthesis of methanol from carbon oxides and hydrogen in shelf columns (RF patent No. 2099320, IPC 6 C 07 C 29/15, 1997).

The disadvantage of this method is the use of steam-oxygen conversion, which requires large costs to ensure the safety of the process, as well as the need to remove excessively formed carbon dioxide, which entails significant energy costs. To implement this method requires expensive equipment, such as compressors, requiring constant tracking and maintenance.

A known method of processing natural gas to produce methanol, including the selection of natural gas under pressure, heating, desulfurization of gas, catalytic steam conversion to produce converted gas, heat recovery, gas compression, methanol synthesis with unreacted gas circulation, heat recovery of the latter and separation of condensed methanol, (RF patent "2124387, IPC 6 C 07 C 27/26, 1999). This decision was taken as a prototype.

The disadvantage of the prototype is significant energy consumption, the use of compressors to ensure that the pressure rises to the required level.

The problem solved by the invention, the provision of methanol by processing associated petroleum gases, as well as gases from new fields with an unstable gas composition at low pressure without the use of expensive compressors in mobile mobile units.

The problem is solved due to the fact that in the known method for producing methanol, including the selection of the processed gas, desulfurization, catalytic steam conversion to produce converted gas, heat recovery, methanol synthesis, separation of condensed methanol, in accordance with the invention, a gas of unstable composition is selected under pressure not less than 0.001 MPa, gas desulfurization is combined with a stage of stepwise pressure stabilization, methanol synthesis is carried out in at least two consecutive flow stages with a decreasing catalyst volume at a pressure of at least 1.5 MPa, and the separation of methanol is carried out between successive stages.

Step-by-step stabilization of gas pressure is carried out using gas-jet apparatuses.

The technical result of solving the problem lies in the fact that through the processing of gas of unstable composition provides a solution to both environmental and economic problems associated with the utilization of associated petroleum gases, as well as gases from new fields with unstable gas composition.

Due to the fact that gas processing is carried out at low pressures: conversion at a pressure of 0.001 MPa and methanol synthesis at a pressure of 1.5 MPa, there is no need to use expensive compressors that require constant monitoring of their operation, which significantly reduces the cost of gas processing and maintenance of plants and allows processing on mobile mobile plants in almost field conditions.

In addition, carrying out the process at low pressures makes it possible to combine gas desulfurization with the stage of stepwise pressure stabilization using gas-jet apparatuses, which also affects the reduction in the cost of the methanol production process.

The synthesis of methanol in at least two consecutive flow stages with a decreasing catalyst volume and the separation of methanol between successive stages eliminates the need for synthesis gas circulation, and synthesizes in isothermal and adiabatic flow reactors at low pressures over a wide range of space velocities.

The implementation of this method will allow the processing of gas of unstable composition directly at the production sites with the production of methanol and its subsequent use for household needs. Thus, it is possible to get rid of flares over oil fields or fields where the produced gas does not meet the requirements of GOST. And also do not spend money on laying gas pipelines to natural gas processing sites.

Figure 1 - block diagram of the stages of the process.

Fig 2 is a diagram of a process for producing crude methanol.

The method of obtaining is as follows (see figure 2). Hydrocarbon gas of unstable composition and pressure (0.001-20 MPa), having passed, if necessary, a purification unit from sulfur-containing compounds (not shown conventionally in figure 2), enters pressure stabilization unit 1, where the latter is stabilized in the range of 2-5 MPa s the formation of a gas-vapor mixture (steam: gas ratio = 4: 1).

Then, the vapor-gas mixture preheated to 650-750 ° C is subjected to catalytic steam reforming in the tube furnace 2. To increase the overall thermal efficiency of the installation, it is possible to utilize the heat of the flue gases of the tube furnace 2, aimed at heating the flue gas, and producing steam and overheating of the vapor-gas mixture before entering the reaction tubes. Utilization of flue gas heat is carried out in the BTA (heat exchange equipment unit) 3.

The converted gas after leaving the reaction tubes is sent sequentially to a recuperator 4, a waste heat boiler 5, a heater 6 and a condenser 7, where heat is removed and water is separated in front of the methanol synthesis unit.

Methanol synthesis is carried out in an isothermal reactor block at a temperature of 180-280 ° C and a pressure of 2-5 MPa.

The dried gas after the condenser 7 enters the heater 8, where its temperature rises to 180-280 ° C and then goes to the isothermal reactor 9. After the reactor, the gas passes through a recuperator 10 and a condenser 11, where the reaction gas is cooled with the separation of crude methanol. After the recuperator 9, the gas is sent to the second stage of synthesis, identical to the first, etc.

Depending on the composition and pressure of the source gas, the number of synthesis steps can range from two to eight.

The exhaust gas from the synthesis unit is sent for combustion in the form of fuel in a tube furnace 2.

This method can be implemented using known equipment, eliminating the use of expensive compressors.

Claims (2)

1. The method of producing methanol, including the selection of the processed hydrocarbon gas, desulfurization, catalytic steam conversion to produce converted gas, heat recovery with water separation, methanol synthesis, condensed methanol separation, characterized in that the unstable hydrocarbon gas is taken under a pressure of at least 0.001 MPa , the desulfurization of hydrocarbon gas of an unstable composition is combined with the stage of stepwise pressure stabilization with the formation of a vapor-gas mixture, methanol synthesis is prov no less than two consecutive flow stages with a decreasing catalyst volume at a pressure of at least 1.5 MPa, and methanol is separated between successive stages. 2. The method according to claim 1, characterized in that the stepwise stabilization of the gas pressure is carried out using gas-jet apparatuses.

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