RU2177022C1 - Natural gas-into-acetylene pyrolysis process involving electric arc energy - Google Patents

Abstract

FIELD: industrial organic synthesis. SUBSTANCE: when performing electric-arc pyrolysis of natural gas at average temperature 1650 C, mixture of hydrogen with part of natural gas is fed at volume ratio (0.2-1):1 into anodic and cathodic parts of electric-arc heater, and the rest of raw material (70% of its total amount) is preheated to 600 C and fed into collision zone for heated anodic and cathodic flows at the reactor inlet, while maintaining total volume ratio of natural gas and hydrogen passed through reactor equal to or higher than 1.5:1. As hydrogen source, a part of tail hydrogen-containing gases can be used, which are formed after cleaning pyrolysis gases to remove carbon black, tars, acetylene homologues, and separation of acetylene from the latter. EFFECT: reduced power consumption, reduced carbon black formation, and prolonged continuous running of plasmotron and reactor. 2 cl, 2 ex

Description

The invention relates to processes for producing acetylene from C ₁ -C ₃ hydrocarbons and natural gas using electrical energy.

Known methods for producing acetylene by pyrolysis of gaseous hydrocarbons C ₁ -C ₃ energy of an electric arc, for example, electrocracking of natural gas, implemented on an industrial scale (in Germany, Romania, Russia) (Antonov V.N., Lapidus A.S. Production of acetylene. - M .: Chemistry, 1970, p. 134).

The main disadvantages of electrocracking:
- significant soot formation (10-12 g / nm ³ );
- the formation of pyrocarbon on the walls, structural details and a small resource of the duration of the continuous operation of the electric arc heater-reactor;
- small resource of the electric arc device;
- low degree of conversion of raw materials into the target product (less than 45%).

Known methods for the pyrolysis of hydrocarbons C ₁ -C ₃ energy coolant (hydrogen), heated in an electric arc, the so-called plasma-chemical pyrolysis.

These methods include the steps of heating hydrogen in an electric arc burning between the anode and cathode, supplying raw materials to a stream of heated hydrogen before entering the reactor, mixing it with a coolant, holding it at temperatures of 1500-1700 ^o C with the formation of acetylene and quenching the reaction products formed (Antonov V.N., Lapidus A.S. Acetylene Production. - M.: Chemistry, 1970, p. 147-152).

The main disadvantages of these methods are:
- the need for high-enthalpy heating of the coolant (up to 5-6 kW • h / m ³ H ₂ ), which can be achieved with a thermal efficiency of an electric arc heater of not more than 70%;
- the required high purity of hydrogen (more than 99%), necessary to increase the resistance of the electrodes - the anode and cathode;
- a small resource of the duration of the operation of devices for implementing the specified method.

 The aim of the invention is to eliminate these disadvantages.

This is achieved by the fact that a mixture of hydrogen and part of the hydrocarbon feed is supplied to the near-cathode and anode parts of the arc at a volume ratio of the flow of hydrocarbons and hydrogen in the range from 0.2: 1 to 1: 1, preferably 0.43: 1. The rest of the feed, 70 % or more of the total flow rate is heated to a temperature above 600 ^o C and fed in a collision zone heated in an arc of the flows at the inlet of the reactor, maintaining the total ratio of the flow of hydrocarbons and hydrogen in the reactor equal to or more than 1.5: 1 at an average temperature of 1650 ^o C. Moreover, as a source Hydrogen is possible to use tail gas generated from the pyrolysis gases after their purification and isolation of these acetylene.

 Example 1

35 nm ³ / h of hydrogen, 15 nm ³ / h of natural gas (hydrocarbon-hydrogen ratio of 0.43: 1) are supplied to the anode and cathode parts of the electric arc of the Y-type electric heater, and these streams are heated into the collision zone, located at an angle of 60-90 ^o relative to each other at the inlet of the reactor, natural gas is heated up to 650 ^o C in an amount of 75 nm ³ / h (total ratio: natural gas to hydrogen 1.5: 1). The electric power of the plasma torch is 400 kW. The specific energy consumption for heating and reaction is 2.3 kW • h / nm ^{3 of} plasma-forming gas.

The yield of acetylene is 46 kg / h. The specific energy consumption was 8.7 kWh / kg acetylene. The total amount of pyrogas is 274 nm ³ / h, the amount of carbon black is 700 g / h, i.e. 2.6 g / nm ³ pyrogas.

 Example 2

Instead of hydrogen, a portion of the tail gas of 35 nm ³ / h containing 92% hydrogen, 4% hydrocarbons, 1.5% nitrogen and 2.5% is fed to the anode and cathode parts of the electric arc of the heater of the same type as in example 1 carbon monoxide, as well as 13 nm ³ / h of natural gas. The remaining parameters, the yield of acetylene and specific energy consumption are the same as in example 1. The operation of the plasma torch is stable.

When the mixture is supplied to the electrode regions with a ratio of hydrocarbon to hydrogen consumption of less than 0.2: 1, the stability of the electric arc heater is violated, and when the ratio is more than 1: 1, the amount of soot increases to 8 g / nm ³ and the specific energy consumption for producing acetylene is up to 9, 5 kW • h / kg.

Claims (2)

1. The method of pyrolysis of natural gas in acetylene by the energy of an electric arc, including the steps of heating the coolant stream in an electric arc plasma torch, supplying natural gas to a coolant stream, mixing them, subsequent pyrolysis of natural gas at an average temperature of 1650 ^o C and hardening of the resulting conversion products, characterized in that part of the natural gas mixed with hydrogen is fed directly to the anode and cathode parts of the arc in a volume ratio of raw materials and hydrogen equal to (0.2 - 1): 1, preferably 0.43: 1, and the rest a portion of the feedstock, equal to or more than 70% of the total flow rate, is heated to a temperature above 600 ^o C and fed in a collision zone to the flows heated in the anode and cathode parts of the arc, maintaining a total ratio of the feedstock to hydrogen equal to or greater than 1.5: 1.  2. The method according to claim 1, characterized in that a hydrogen-containing tail gas generated from pyrolysis gases after purification and acetylene evolution is used as a hydrogen source.