The reforming process of natural gas in ammonia production

 

The invention relates to processes of reforming of natural gas for ammonia production. The essence of the method lies in the fact that compressed natural gas for technological purposes is mixed with admixtures purge gas cycle for the synthesis of ammonia, is heated in additional convective furnace coil primary reforming, is subjected to low-temperature desulfurization, mixed with superheated steam, heated in a convection furnace coil primary reforming, is supplied into the reaction tube radiant zone of the furnace the primary reformer. Utilization of flue-gas furnace primary reforming is carried out in the secondary coils of the convective zone due to the heating of natural gas and condensate Stripping columns. The technical result consists in reducing energy consumption, improving the reliability and safety of operation, optimization of operating modes of the stage desulfurization unit combustion furnace equipment of the primary reformer, increasing the production of ammonia. 2 Il.

The invention relates to processes of reforming natural gas to produce ammonia, used in the production of mineral heating natural gas before stage desulfurization [EN 2175950 C2, 2000.03.02], according to which natural gas from pipeline under high pressure of 3.8-5.0 MPa is applied to the ammonia plant. Under this scheme the throttling is only part of 30-45% of the supplied natural gas used for combustion. The remainder of natural gas after filtration from the solid mechanical impurities is supplied to the heater, built-in oven primary reforming of natural gas, where it is heated to a temperature of 150-200°C due to heat from flue gases and is sent directly to fire the heater system and hydro - desulfurization, where it is heated to a temperature of 370-400°C and then fed to the hydrogenation and desulfurization according to the technological scheme of the process of reforming.

The disadvantage of this scheme is that the low temperature level of the natural gas heating in the additional heater and use the "classic" scheme desulfurization temperatures 370-400°C do not allow the exclusion of permanent technological scheme of fire heater - occurs only decrease the heat load on it. When this heat loss due to high temperature flue gases and due to losses to the atmosphere through the walls of the apparatus remain.

The main disadvantages of this scheme is the possibility of overheating of natural gas in the coil, which is without duct when the operations start and stop the oven primary reforming, increased demands on thermal stability of the metal coil natural gas.

The closest in technical essence and the achieved result to the present invention is a method of reforming of natural gas in the production of ammonia [ammonia Production / Ed. by B. N. Semenov. - M.: Chemistry, 1985, S. 21-57]. The method consists in the fact that the raw materials - natural gas 1 is supplied from the factory manifold pressure of about 1.2 MPa, is divided into two streams: one for technological purposes 2 going to the conversion, the other for burning as fuel 3. Natural gas for technological purposes komprimerede to 4.6 MPa in a two-stage turbocharger 4, is mixed with nitric mixture of 5 coming from the Department of ammonia synthesis (after compressor first stage synthesis gas), in the ratio Prim°C. The mixture of natural gas with nitric mixture enters the reactor hydrogenation of sericoidini 7 volume 35-45 m3of the catalyst. Then natural gas passes sequentially through two adsorber 8 and 9 filled with scavenger, 31.5 m3of each absorber. After the process of purification from sulfur natural gas is mixed with superheated steam is 10 and supplied to the heater 11, located in the convective part of the furnace 12. After the convection coil gas-vapor mixture to a temperature of about 500-550°C. is supplied into the reaction pipe 13 is installed in the radiation chamber, the tube furnace, heated with a heat of combustion of natural gas in the annular space of the furnace. Flue gases leaving the tube space of the tubular furnace at a temperature of about 1000°C. the Physical heat of the hot flue gas is used for sequential heating of the reaction gas mixture 11, steam-air mixture 14, overheating of the water vapor in the second stage superheater 15, overheating of the water vapor in the first stage of the steam superheater 16, boiler water in the economizer 17, the fuel gas heater 18. Next, the flue gases are released into the atmosphere two exhausters 19 through the smoke tronauts: 1. The need for a separate fire apparatus heated front stage desulfurization of natural gas heating to a temperature of 400°C. increases the heat loss due to high temperature flue gases 300-320°C and at the expense of losses to the atmosphere through the walls of the apparatus. 2. A large amount of catalyst and absorber used in stage desulfurization. This increases the loss of natural gas due to a long time warming up of the catalyst and absorber in the start-up of ammonia. 3. Increased risk of operation of the desulfurization apparatus with a wall temperature above 300°C due to the possibility of development of hydrogen corrosion and creep of the metal housings of the apparatus. 4. The presence of the recycling mixture of nitric, part of which is returned from the stage of compression of the synthesis gas to the stage desulfurization, thereby increasing the power consumption of the unit. 5. The high temperature of the discharged flue gases from the furnace to the primary reformer, whereby the consumption of natural gas remains at a comparatively high level.

The present invention is the optimization of operating modes of the stage desulfurization unit combustion furnace equipment primary reforming the ow diagram of the apparatus of the fire-heated natural gas.

The task in accordance with the present invention is solved in the following way: as a source of hydrogen for the process of purification of natural gas from the sulfur compounds used immixture purge gas cycle for the synthesis of ammonia, heating the mixture of natural and carry out the purge gas coil in the convection zone of the furnace the primary reformer, the cleaning gas from the sulfur compounds is carried out at low temperatures of at least 230°C., load of hydrogenation catalyst and absorber sulfur compounds produce comprehensively in a single device, using low-temperature catalytic hydrogenation of sericoidini and low-temperature absorber sericoidini, waste heat of flue gas furnace primary reforming is carried out in the secondary coils of the convective zone due to the heating of natural gas and condensate Stripping columns, fire heater before separating the desulfurization is used for unit start with a "cold" state.

The proposed process is implemented according to the circuit diagram shown in Fig.2.

Feedstock - natural gas 1 is supplied from the factory network with a pressure of 0.7 to 1.7 MPa. In Assembly natural gas is divided pour, compressed to 3.5-4.5 MPa in the compressor 4 of the natural gas is mixed with the purge gas cycle ammonia synthesis 5 containing ammonia in the volume concentration of not more than 2%, in order to achieve the volume fraction of hydrogen 2-5%, then goes to the convection coil 6 of the furnace primary reforming unit 7, located along the flue gas after the coil of the fuel gas heater 8, where it is heated to a temperature of at least 230°C. Next, a mixture of natural gas with a purge gas to the synthesis loop is fed into the reactor 9 volume 34 m3uploaded by catalytic hydrogenation of sericoidini and absorber sericoidini, operating at low temperatures of not less than 230°C. After purification from sulfur natural gas is mixed with superheated steam is 10 and enters the convection coil gas mixture 11 of the furnace of the primary reformer. After the convection coil gas-vapor mixture is supplied into the reaction pipe 12 radiant zone of the furnace primary reformer heated by an open fire burned natural gas. Flue gases with temperatures up to 1100°C, proceed for heat in the convection section of the furnace of the primary reformer (block thermal equipment), which consistently respriratory 15 superheater, water heater boiler feed pressure of 10.5 MPa 16, the fuel gas heater 8, heater natural gas before desulfurization 6, boiler condensate Stripping tower 17 18.

Fire heater natural gas 19 before separating unit remains in the technological scheme only for unit start with a "cold" state.

The advantages of the proposed method of reconstruction are:

1. A significant reduction in energy consumption of ammonia at the expense of:

- heat recovery flue gas furnace primary reformer to heat the natural gas and condensate Stripping column;

exclusions from the scheme inefficient firing heater;

- use of low-temperature catalytic hydrogenation of sericoidini and low-temperature absorber sericoidini;

- reduce the volume of catalyst in the hydrogenation of sulfur compounds and absorber sulfur compounds;

- use as a source of hydrogen for hydrogenation of sericoidini purge gases cycle for the synthesis of ammonia.

2. Improving the reliability and safety of operation of the ammonia plant due to the exclusion of the constant technological scheme of the apparatus with Ognevka Stripping columns in the convection zone of the furnace primary reforming eliminates the possibility of overheating of technological media in the operations of starting and stopping the furnace primary reforming, increased demands on thermal stability of the metal coil and boiler.

Claims

Method of reforming of natural gas in ammonia production, which consists in the fact that compressed natural gas for technological purposes is mixed with hydrogen-rich recycle gas is heated, subjected to desulfurization of a hydrogenation catalyst and absorption of sulfur compounds, is mixed with superheated steam, heated in a convection furnace coil primary reforming, is supplied into the reaction tube radiant zone of the furnace primary reformer heated by an open fire burned natural gas, flue gases with temperatures up to 1100°C, leaving a radiant zone of the furnace primary reforming, are consistently coils convection zone, characterized in that as a source of hydrogen for the process of purification of natural gas from the sulfur compounds used immixture purge gas cycle for the synthesis of ammonia, heating the mixture of natural and carry out the purge gas coil in the convection zone of the furnace the primary reformer, the cleaning gas from the sulfur compounds is carried out at low temperatures of at least 230°C., load the reattaching the low-temperature catalytic hydrogenation of sericoidini and low-temperature absorber sericoidini, waste heat of flue gas furnace primary reforming is carried out in the secondary coils of the convective zone due to the heating of natural gas and condensate Stripping columns, fire heater before separating the desulfurization is used for unit start with a “cold” state.

 

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FIELD: hydrocarbon conversion catalysts.

SUBSTANCE: catalyst for generation of synthesis gas via catalytic conversion of hydrocarbons is a complex composite composed of ceramic matrix and, dispersed throughout the matrix, coarse particles of a material and their aggregates in amounts from 0.5 to 70% by weight. Catalyst comprises system of parallel and/or crossing channels. Dispersed material is selected from rare-earth and transition metal oxides, and mixtures thereof, metals and alloys thereof, period 4 metal carbides, and mixtures thereof, which differ from the matrix in what concerns both composition and structure. Preparation procedure comprises providing homogenous mass containing caking-able ceramic matrix material and material to be dispersed, appropriately shaping the mass, and heat treatment. Material to be dispersed are powders containing metallic aluminum. Homogenous mass is used for impregnation of fibrous and/or woven materials forming on caking system of parallel and/or perpendicularly crossing channels. Before heat treatment, shaped mass is preliminarily treated under hydrothermal conditions.

EFFECT: increased resistance of catalyst to thermal impacts with sufficiently high specific surface and activity retained.

4 cl, 1 tbl, 8 ex

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