CS256167B1 - A method for removing soot from gas and from heat exchange cells - Google Patents

Abstract

Washing off soot from gas after partial oxidation of hydrocarbons and more efficient rinsing of soot from heat exchanger tubes, in such a way that in the ring circuit of the heat exchanger sludge, soot scrubbing in venturi partitions and heat recuperator tubes rinsing , adds a nonionic or ionic surfactant in a concentration of 1 to 20 ppm.

Description

(54) A method for removing soot from gas and heat exchange plates

Gas scrubbing after partial oxidation of hydrocarbons and more efficient rinsing of the soot from heat recuperator tubes, in such a way that non-heat recuperator or non-heat recuperator tubes are added to the common circuit of scrubbing water, venturi scrubbing and rinse tubes. an ionic surfactant in a concentration of 1 to 20 ppm.

258167

The invention relates to a method for removing soot from gas and heat exchange surfaces.

In the partial oxidation of hydrocarbons, the resulting fission gas contains a considerable amount of carbon black. For example, about 20 grams of carbon black is produced per kilogram of decomposed methane at 1450 ° C (oxygen: methane molar ratio = 0.37). Before further processing, it is necessary to remove the carbon black gas

The partial removal of soot occurs already when the fission gas is fermented in the reaction chamber with water, oil or a higher boiling liquid. In the next step, the soot is removed: in shower towers, venturi scrubbers, cyclones, filters, electrofilters, etc. [J. Wozniakowski: Chemist (Gliwicej 20, 2, 53, 1967; E.G. Hurley: Filter. Separ. 8, 3, 271, 297, 1971; G. Schiele: Erdoel Kohle Erdgas, Petrochem. 23, 5, 284, 1970.)

Various liquid media are used for the removal of soot. The use of chlorinated and fluorinated liquid hydrocarbons is known. The scrubbing with high boiling hydrocarbons is the subject of German Patent No. 1,240,052.

Also known is the method of scrubbing carbon black into an oil-in-water emulsion, the stability of which is maintained by the addition of a small amount of emulsifier (French Patent 1450 508). Otherwise, the soot is washed only with water and the emulsifier oil is added additionally to the vessel where the soot oil phase is decanted.

A disadvantage of these processes is the fact that the oil with water forms relatively stable emulsions from which the oil is difficult to separate completely. For this reason, oil leakage may occur. In addition, the aforementioned technologies require separate oil management.

Therefore, scrubbing of soot with water (DOS 2 951 44.2) is more frequently used, although the scrubbing efficiency of water as a medium against soot is lower than that of oils.

Conventional is a process in which the fission gas is saturated with water vapor, which soaks the soot, which is then removed in the separators.

The overall efficiency of soot scrubbing can be enhanced by using a foam apparatus and scrubbing the soot in the foam layer (USSR Patent 183,188; A.J. Valdberg et al., Chim. Prom. 11, 845, 1965; 4, 258, 1972). The apparatuses are countercurrent and the foam mode is achieved by adding small amounts of surfactant to the scrubbing water. According to Romanian patent 71163, an aqueous solution of 80-150 ppm contained sodium dodecylbenzenesulfonate.

Said processes using a scrubbing medium water have the disadvantage that the carbon black, by its nature hydrophobic, is difficult to wet with water. Foaming in the foam layer eliminates this problem to some extent, but can only be used with a separate water circuit.

When partial oxidation of hydrocarbons occurs ^: at elevated pressure (0.2 to 0.3 MPa), the heat of the purified fission gas is usually utilized in indirect heat exchangers (re-entranters). Even after passing through sewage plants, the fission gas still contains a certain amount of soot that settles on the walls of heat exchange apparatus pipes, worsens heat transfer, increases the hydraulic resistance of the equipment, which is the main cause of worsened line operation and eventually leads to shutdown.

This problem is partly solved by continuous liquid flushing of the heat exchanger tube walls. Oil or water is most commonly used. Oil rinses soot more efficiently ^! However, it has other disadvantages already mentioned. The use of water encounters a problem of lower efficiency (poor wettability of soot), but it is more frequent due to easier handling.

The water injected into the tubular space of the heat exchange apparatuses is part of the common water circuit of the fermented water and the water used for scrubbing the soot (shower towers, Venturi washing machines, etc.). Spraying the rinsing liquid into the heat exchanger tubular space is necessary, but on the other hand, it partially worsens the heat transfer (the liquid has a significantly lower temperature than the fission gas and forms a film layer on the tube walls). Moreover, in such a case, the possible use of the foam apparatus for scrubbing soot is questionable, since foam from its circuit must not become part of the common circuit circuit. There must be no foaming when flushing with water as well as in the tubular space of the heat exchangers.

These disadvantages are overcome by the process according to the invention, which comprises adding a non-ionic or ionic surfactant directly to a common water circuit, which is used for gas flow, soot scrubbing and rinsing of the heat exchangers of the heat exchangers, so that its concentration in water is 1 to 20 ppm.

This will improve the wettability of the soot with water and wash it more efficiently, as well as increasing the efficiency of rinsing the heat exchange surfaces of the heat exchangers. The effects will be reflected in the reduction of the hydraulic resistance of the heat exchangers (heat exchangers) and in the improvement of the heat transfer, which is reflected in the extension of one cycle of the line. At the same time, the pressure in the reaction chamber is reduced, which can increase the yields of the fission product (for example, when the methane is split into acetylene) and makes it possible to increase production by increasing the fissioning load of the feedstock.

Example 1

Cracked gas from the partial oxidation of methane-containing carbon black for quenching 3.2 grams per cubic meter, enter the flow rate of 5 L · min ^-1 to, the column filled with Raschig rings. The soot is washed in countercurrent flowing at 80 ° C with warm water at a flow rate of 1 1. min ^-1 . After 16 hours of operation, 6.3 grams of soot was collected in water and the column packing was planted with a total weight gain of 1.4 grams of soot.

In a repeated experiment under the same conditions, 10 ppm of propylene oxide and ethylene oxide nonionic surfactants were added to the water. At the same time, 14.1 grams of soot was collected in the water and the packing remained clean.

Example 2

The cleavage of the gas partial oxidácle methane content of the carbon black in kvančovaním 3.32 grams per cubic meter, enter the first flow rate of 5 ^min-1 to the column filled with Raschig rings. The soot was washed countercurrently with flowing 80 ° C warm water at a flow rate of 1 l.min ^-1 . After 16 hours of operation, 6.5 grams of soot was collected in water and the column packing was planted with a total weight gain of 1.3 grams of soot.

In a repeated experiment under the same conditions, 10 ppm of sodium alkylbenzenesulfonate ionic surfactants were added to the water. At the same time, 13.2 grams of soot was collected in the water and the packing remained clean.

Example 3

The usual running time of the acetylene production line by the partial oxidation of methane given by the heat recuperation cleaning cycle is 5 months, more rarely up to 6 months. The load of two fission furnaces methane, m is 13 000 Nm ³ .h ^-1 , in the last month before the line shutdown is reduced to 12 000 Nm ^{3 due to} increasing pressure loss. h ^-1 .

At the beginning of the sixth month of operation of the line, at high pressure in fission furnaces 0.3 MPa, a solution of non-ionic surfactants based on propylene oxide and ethylene oxide began to be fed into the circuit of the circulating vaults of the furnace (venting), venturi scrubbers and heat recuperators. its concentrate ^! and in the water ranged between 5 and 10 ppm. The pressure drop was gradually reduced by up to 0.015 MPa, which prolonged the operation of the line for 19 months and during the whole cycle it was possible to maintain the methane load, m to 13,000 to 13,500 Nm ³ . h ^-1 , while the pressure in the split furnaces did not exceed 0.3 MPa. The acetylene content of the fission gas increased from 6.4% to 6.5% by volume as a result of the reduction in the pressure in the split furnaces.

Claims (3)

SUBJECT Method for removing soot from gas and heat exchange surfaces, characterized in that a nonionic or ionic surfactant is added to the water used for gas flow, soot scrubbing and rinsing of the non-ion exchange surfactant so that its concentration in the water is 1 to 20 ppm.