RU2235889C1 - Method of heat regeneration at obtaining synthesis-gas for production of ammonia and methanol - Google Patents

Abstract

FIELD: industrial power generation and chemical technology.

SUBSTANCE: invention can be used in production of synthetic ammonia and methanol. According to proposed method of heat regeneration for obtaining synthesis-gas for producing ammonia and methanol from natural gas or other hydrocarbon raw materials containing admixtures of sulfur compounds effected by chemisorption-catalytic sulfur purification under higher pressure and temperature with heating of initial gas, vapor conversion of hydrocarbons in tubular furnace by combustion of fuel gas and use of heat of outgoing smoke gas in heat utilization equipment unit including heat exchange elements arranged in series in direction of smoke gas flow in zones for heating gas-gas mixture, air-air mixture and for overheating water vapor at pressure of 8.8-10.9 MPa to temperature of 475-500^oC, and in zones of heating of feed water and heating of fuel gas, heating of initial gas for chemisorption-catalytic sulfur purification is carried out by smoke gas of tubular furnace in heat exchange elements arranged in heat utilization equipment unit in zone after overheating of water vapor.

EFFECT: reduced consumption of fuel gas.

3 cl, 1 dwg

Description

The invention relates to the field of industrial energy and chemical technology and can be used to produce synthesis gas in the production of synthetic ammonia and methanol.

There is a method of purification of natural and process gases in the production of synthesis gas for the production of ammonia by conducting chemisorption-catalytic desulfurization of the source gas under elevated pressure and temperature (see. Reference book nitrogen. - M .: Chemistry, 1986, p. 208-215, fig. 111-1). The heating of the source gas supplied to the treatment is carried out in a fire heater.

The disadvantage of this method is the need to use separate equipment in the form of a fire heater and low efficiency of its heat, which leads to an increase in total energy consumption.

Closest to the proposed invention is a method of heat recovery in the production of synthesis gas for the production of ammonia and methanol from natural gas or other hydrocarbon feedstocks containing impurities of sulfur compounds (see Nitrogen Handbook. - M .: Chemistry, 1986, p. 112- 121, 83-85), carried out by means of chemisorption-catalytic desulfurization under elevated pressure and temperature with heating of the source gas, steam conversion of hydrocarbons in a tube furnace by burning fuel gas and using the heat of the exhaust flue gas and in a block of heat-consuming equipment, including heat-exchange elements, located successively along the flue gas zones for heating a gas-vapor mixture, steam-air mixtures and for overheating water vapor with a pressure of 8.8-10.9 MPa to a temperature of 475-500 ° C, as well as in zones heating feed water and heating fuel gas.

The known method has the disadvantage that it is characterized by insufficient full use of the heat of the flue gases in the block of heat-using equipment, caused by the inefficient temperature regime of heating the source gas with flue gas having a high temperature, and a deficit of heat-removing media in the block of heat-using equipment of the tubular furnace, resulting in increased total losses heat with exhaust flue gases and, as a consequence of this, an excessive consumption of fuel gas.

The technical result, the achievement of which the present invention is directed, is to reduce fuel gas consumption by more fully utilizing the heat of flue gases.

The specified technical result is achieved by the fact that in the heat recovery method for producing synthesis gas for the production of ammonia and methanol from natural gas or other hydrocarbon raw materials containing impurities of sulfur compounds, carried out by chemisorption-catalytic desulfurization under elevated pressure and temperature with heating of the source gas, steam conversion of hydrocarbons in a tubular furnace by burning fuel gas and using the heat of the exhaust flue gas in a block of heat-using equipment, including heat-exchange elements located in successive zones along the flue gas for heating a vapor-gas mixture, a steam-air mixture and for overheating water vapor with a pressure of 8.8-10.9 MPa to a temperature of 475-500 ° C, as well as in zones of heating feedwater and heating fuel gas, heating the source gas for chemisorption-catalytic desulfurization is carried out by flue gas of a tube furnace in heat exchange elements located in a block of heat-using equipment in the zone after overheating of water vapor.

The specified technical result is also achieved by the fact that the heating of the source gas for chemisorption-catalytic desulfurization is carried out in heat exchange elements arranged sequentially along the source gas, first in the area near the exit of the flue gas, then in the area in front of the heat exchange elements for heating the feed water.

The specified technical result is also achieved by the fact that protection against overheating of the heat exchange elements for heating the source of desulfurization gas during stops and stopping the flow of media is carried out first by a controlled discharge of gas after the heat exchange elements, then by supplying a protective gas medium, for example, purge nitrogen can be used fuel gas, etc.

The drawing shows a schematic diagram for implementing the method.

The scheme includes a chemisorption-catalytic desulfurization stage with a source gas heating unit in heat-exchange elements located in a unit 1 of heat-using equipment, a catalytic hydrogenation apparatus of organosulfur compounds 2 and chemisorption absorbers of hydrogen sulfide 3. The scheme also includes steam conversion of hydrocarbons in a tube furnace 4 with exhaust fans 5, exhaust pipe 6 and steam-air conversion of methane 7.

The source gas containing impurities of sulfur compounds under pressure up to 4.5 MPa is heated to 350-400 ° C in heat exchange elements located in the block of heat-using equipment 1 in the zone after overheating of water vapor along the flue gas or to increase the achieved effect in two successive steps along the gas: first in the zone near the exit of the flue gas, then in the zone in front of the heat exchange elements for heating the feed water.

Next, the gas enters the desulfurization apparatuses 2, 3 and, after adding water vapor and heating the gas mixture in the block of heat-using equipment 1, is fed into the reaction tubes of the tube furnace 4. After steam conversion, the gas-vapor mixture is supplied to the steam-air conversion 7 and then sent for further processing to the CO conversion and for the removal of CO ₂ and CO. The block of heat-using equipment 1 includes heat exchangers located in series along the flue gas zones for heating the gas mixture, steam-air mixture and for overheating water vapor with a pressure of 8.8-10.9 MPa to a temperature of 475-500 ° C, as well as in the heating zones feed water and fuel gas heating. Flue gases after heat recovery in the unit of heat-using equipment 1 with the help of a smoke exhauster 5 enter the exhaust pipe 6.

Example 1

In accordance with the invention, there is provided a method for producing synthesis gas for ammonia production with a capacity of 1360 t / day with heating of the source gas in heat exchange elements located in the block of heat-using equipment 1 in the zone after overheating of water vapor along the flue gas.

The source gas enters the heat exchange elements under a pressure of up to 4.5 MPa at a temperature of up to 130 ° C.

The temperature of the flue gas after overheating of water vapor is 430-500 ° C. After heat exchange heating elements, the temperature of the source gas is 350-400 ° C, and the flue gas is 390-450 ° C. The fire heater for heating the source gas for desulfurization is excluded.

As a result of the additionally introduced heat removal from the flue gas, a more complete use of heat and a decrease in the temperature of the exhaust flue gas are ensured while maintaining the heating mode of other media in the block of heat-using equipment within the acceptable range. In addition, the exclusion of a fire desulfurization heater eliminates the consumption of fuel gas for it. As a result, the saving of fuel gas in thermal equivalent is 3.2 million kcal / h compared with known methods.

Example 2

A method for producing the synthesis gas from Example 1 with the same initial data but with heating the source gas for desulfurization in a block of heat-using equipment in two successive steps along the gas is presented: first in the zone near the exit of the flue gas, then in the zone in front of the heat exchange elements for heating feed water.

This solution provides additional use of heat of the exhaust flue gas in comparison with example 1, which provides fuel gas savings in thermal equivalent of up to 5 million kcal / h compared with known methods.

In connection with the use of flue gas with a temperature of up to 500 ° C and in order to exclude the use of alloy steels for the manufacture of heat exchange elements for heating the source gas, the invention provides for protection against overheating during shutdowns and interruptions in the flow of media, carried out in two stages: gas discharge after heat-exchange elements, then supply of a protective gas medium, for example, purge nitrogen, fuel gas, etc.

Claims (3)

1. The method of heat recovery in the production of synthesis gas for the production of ammonia and methanol from natural gas or other hydrocarbon raw materials containing impurities of sulfur compounds, carried out by chemisorption-catalytic desulfurization under increased pressure and temperature with heating of the source gas, steam conversion of hydrocarbons in a tube furnace burning fuel gas and using the heat of the exhaust flue gas in a block of heat-using equipment, including heat exchange elements located but along the flue gas zones for heating the vapor-gas mixture, steam-air mixture and for overheating water vapor with a pressure of 8.8-10.9 MPa, to a temperature of 475-500 ° C, as well as in the zones for heating the feed water and heating the fuel gas, characterized in that the heating of the source gas for chemisorption-catalytic desulfurization is carried out by the flue gas of a tubular furnace in heat exchange elements located in a block of heat-using equipment in the zone after overheating of water vapor. 2. The method according to claim 1, characterized in that the heating of the source gas for chemisorption-catalytic desulfurization is carried out in heat exchange elements arranged sequentially along the source gas, first in the area near the exit of the flue gas, then in the area in front of the heat exchange elements for heating the feed water . 3. The method according to one of claim 1 or 2, characterized in that the protection against overheating of the heat exchange elements for heating the source gas desulphurization during stops and stopping the flow of media is carried out first by a controlled discharge of gas after the heat exchange elements, then by supplying a protective gas medium, in which purge nitrogen, fuel gas, etc. can be used, for example.