DD248369A5 - METHOD FOR THE PRODUCTION OF ASH ARMS AND ELECTRICALLY CONDUCTIVE SOOT - Google Patents

Abstract

The invention relates to a process for the production of ash-lean and electrically conductive carbon black and to an apparatus for carrying out the process. To produce low ash and electrically conductive carbon black by the Stuetzflamm- and quench-free process, the hydrocarbons under pressure segregated to at least 120C and the oxygen gas to 150C and more above the temperature of the fuel. In the reaction, an average residence time of at least 10 seconds is maintained. The carbon black formed in the reactor is then cooled in stages to the filtration temperature. The device for carrying out the method contains at least one heat exchanger for indirect cooling of the soot product. Fig. 1

Description

For this 2 pages drawings

Field of application of the invention

The present invention relates to a process for producing ashless and electrically conductive carbon black by partial combustion and pyrolysis of liquid fuel with an oxygen-containing gas in a reactor. Furthermore, the invention relates to an apparatus for carrying out the method.

Carbon black consists essentially of elemental carbon, which is hexagonally arranged in planes which show less mutual adhesion than graphite. Other components in minimal concentrations are oxygen, hydrogen, and residual structures of the starting hydrocarbons. The carbon blacks are sorted technically according to their fields of application.

Characteristic of the known technical solutions

There is already known a method of producing carbon black in which a gas-air flame of high temperature is generated in a combustion reactor into which liquid hydrocarbons are then injected. The carbon black which forms in the endothermic cleavage reaction occurring during this process is quenched with water at the end of the reaction zone and then recovered. The yield is usually about 50% of the oil-carbon used.

Special difficulties and expensive processes are offered by the production of carbon black, which has electrically conductive properties. For this purpose, a graphite-like structure is sought, which can only be achieved by a significant quality improvement.

Object of the invention

The aim of the invention is to avoid the difficulties and the high cost of the known methods.

Explanation of the essence of the invention

The object of the invention is to propose a method in which to work without a constant support flame and in which there is no quenching of the hot reaction products with water, by means of which otherwise the chemical reaction is brought to a standstill, and an apparatus for performing this method.

According to the invention it has now been found that the soot quality is decisively influenced by the residence time in the reactor.

Further quality improvement is achieved by the stepwise cooling, which is in contrast to sudden quenching.

The inventive method for producing ash-lean and electrically conductive carbon black by partial combustion and pyrolysis of liquid fuel with an oxygen-containing gas in a reactor according to the invention is that the liquid hydrocarbon preheated and under pressure and the oxygen-containing gas having a higher temperature than the hydrocarbon are passed together in the reactor, while the supply of a reaction preceding gas-air supply into the reactor takes place locally separate from the entry point of the reaction components, and also in that the partial combustion and pyrolysis takes place at a residence time which is at least about 10 seconds, whereupon the reaction products are cooled indirectly and stepwise outside the reactor. It is expedient that there is a difference of at least 150 ° C between the temperature of the hydrocarbon and the oxygen-containing gas. The experiments have also shown that it is particularly vorteilhalft when heated to about 120 ° C at at least 15 bar pressure and the oxygen gas to about 300 ° C for introduction into the reactor of the carbons.

Instead of the sudden quenching by injected into the reaction space water according to the invention the reaction products at about 800 to 1 200 ⁰ C warm reaction products are cooled in at least two stages by heat exchange to a filtration temperature of 150 to 300 ⁰ C.

In this way, a high quality electrically conductive product with a minimum ash content is produced, which can be widely used in the industry. The so obtained carbon black can be used in particular as a reinforcing agent and abrasion protection in rubber and plastics, as a pigment and / or as an electrostatically conductive additive in plastics and in batteries. ,

For carrying out the proposed method, a device is suitable which has a reactor which has a length / diameter ratio of at least 2. This reactor is preceded by means for heating the hydrocarbons under pressure and for heating the oxygen-containing gas. Furthermore, at least one heat exchanger for the stepwise indirect cooling of the reaction products downstream of the reactor.

Due to the proposed diameter ratio, a prolonged, particularly favorable residence time is achieved, while the other measures ensure the advantages and special features of the method mentioned above.

A particularly advantageous embodiment of the device provides that the combustion reactor is provided with zone-wise distributed cooling tubes, which are arranged in the lining and adapted to receive a circulating in countercurrent cooling medium. Furthermore, the reactor is preceded by a gas-heated heat exchanger for heating the oxygen-containing gas.

embodiment

An embodiment of the proposed device is illustrated on accompanying drawings, on the basis of which the method is explained. Show it:

Fig. 1: a schematically drawn device with a vertical reactor; and Figure 2: a cross section through the reactor lid.

In Fig. 1, 1 denotes a reactor which has a cylindrical body 2, a hemispherical cover 3 and a conical outlet 4. In the reactor cover 3, three feed units 5 are arranged evenly distributed, while in the middle of the lid 3, a further feed unit 6 is provided. For each feed unit 5 performs a line 7 for hydrocarbon, z. As for oil, which line 7 connects the feed unit 5 with a heat exchanger 8. The heat exchanger 8 is heated by steam and has a steam connection 9 for this purpose. The supply to the heat exchanger 8 takes place through a line 10 with feed pump eleventh

In each feed unit 5 also opens an air line 12, which comprises the line 7 concentrically in the region of the feed unit 5, so that at the common mouth of the two lines an injector effect arises. In this way, through the hydrocarbon flowing through the conduit 7, an oxygen-containing gas, e.g. Air, entrained by the conduit 12, wherein the mixture enters the reaction chamber 13.

To the central supply unit 6, a gas-air supply 14 is connected, by means of which a flame for preheating the reaction space 13 of the reaction is formed beforehand. The described feed unit 6 is thus arranged locally separate from the feed units 5 and is used in advance of the reaction for preheating, so that during the reaction no support flame is present.

For indirect and stepwise cooling of the reaction products serve heat exchangers, which are arranged around cylindrical body 2 of the device in the flow direction, arranged one behind the other. The heat exchangers may consist of vertically extending cooling tubes 15, which are embedded in the lining of the cylindrical body 2 and serve to receive a circulating in countercurrent to the flow direction of the reaction products cooling medium. The connection points of the cooling tubes are designated 16 and 17. The cooling tubes form cooling coils, it being understood that several independent cooling coils can be arranged, which form different cooling zones.

It is essential that during operation of the device, the hydrocarbons before starting the reaction have a temperature which is about at least 150 ° C below the temperature of the oxygen-containing gas. Preferably, the hydrocarbons are contacted at a pressure of at least 15 bar and at a temperature of about 120 ° C with the oxygen-containing gas having a temperature of about 300 ⁰ C. In this state, the reaction components are then introduced into the burner. At the outlet of the reactor, the reaction products have a temperature of 800 to 1200 ⁰ C and are cooled by means of the heat exchanger to a filtration temperature of 150 to 300 ⁰ C.

For heating the oxygen gas, a heat exchanger heated with partial gas and / or heating gas may be present.

It is believed that the lighter boiling components of the liquid hydrocarbon, upon sudden pressure reduction at the nozzle and concurrent contact with the much hotter oxygen gas, exit the vaporized hydrocarbon in a kind of flash diffusion, ignite instantaneously to provide the heat-exiting reaction. It is favorable that the oxygen gas and the hydrocarbon can come into contact with each other as soon as possible at the burner.

The droplets containing the higher boiling components of the hydrocarbon - a not too fine atomization of the hydrocarbon is useful in the practice of the process - are minimally cooled for the moment briefly by the above-described evaporation of the lower boiling fractions. As a result, the resistance of said droplets is probably somewhat increased, which, together with the zone-wise cooling of the reactor, contributes to increasing the residence time of the reaction mixture.

Next, two operational examples of the proposed method will be explained, which, however, do not represent a particularly preferred embodiment of the invention.

Danger was both Maie a reactor with 7.4m height and 1.8m diameter.

example 1

Process data: Grade 100/25

Process air (N m ³ / h 600

KW (kg / h) (hydrocarbon) 200

Temperature process air ° C 350

Temperature KW ⁰ C 120

average calculated residence time, see. 91

Temperature profile: ° C

Measuring points: 1 1 100

2

3.

Cooling input ⁰ C 930 ·

Cooling output ⁰ C 280

Filtration temperature ° C 250

Product data: ''

(Product from process with above data)

BETm ² / g 120

DBPml / 100g · 196

Tint (IRB-E) 85

Volatile constituents,% 1.5

Loss at 900 ⁰ C for 5 min

pH 7

Sieve residue, 45 μm,% 0.05

Ashing residue,% 0.5

Extract with xylene,% 0.05

Electrical resistance, cm

in 50% DBP mixture 1.0

Water content,% 0.5

AS number, ml / 5g 23.5

Bulk density, g / l after compaction 160

Example 2

Process data:

Process air (Nm ³ / h) 1850

KW (kg / h) 500

Temperature process air, ° C 300

Temperature KW, ° C. 75

average residence time, see. 44

Temperature profile ⁰ C:

Measuring points: 1 1 500

2

3.

4 680 Radiator inlet, ⁰ C 950 Radiator outlet, ⁰ C 265 Filtration temperature, ⁰ C 230 Product data:

(Product from process with above data)

BETm ² / g 67

DBPml / 100g 210

Tint (TRB-5) 84

Volatiles, %

Loss at 900 ° C for 5min 1.5

pH 7

Sieve residue, 45 μm,% 0.05

Ashing residue,% 0.5

Extract with xylene,% 0.05

Electrical resistance, cm

in50% DBP mixture 0.7

Water content,% 1.5

AS number, ml / 5g 24.5

Bulk density, g / l after compaction 125

Further below are the determination methods for the average residence times given above and for the electrical resistance of the carbon black in 50% DBP mixture. Average residence time E _v in the reactor

volume

throughput

Practical calculation: volume of the reactor (in m ³ )

The reactor is a 6m high circular cylinder with

Vr = χ (600 + 0.40) = Vr 16.64 m ³ 4

Throughput (mixture): 2 800Nm ³ Zh 2 800Nm ³ / h + 280 Nm ³ Zh calculated value = 3080Nm ³ Zh = 0,86m ^'3 / sec

_ 16,7 m ³ see

E _v = - ^: - = 19.4 see.

A OC r ^ s ^ - ---

υ, ου m

To determine the electrical resistivity (conductivity) of the carbon black, the following method was developed: 1 to 4 g of carbon black, weighed exactly, are added dropwise to a glass plate with dibutyl phthalate and mixed until a paste is formed. The dibutyl phthalate is dosed with a burette so that the volume consumed is accurately known. Usually, the correct paste consistency is obtained with a dibutyl phthalate amount corresponding to the DBP value + 10%.

The carbon black concentration in the paste (GrammZGramm)

Soot = weight of soot, grams

v _DBP = volume of dibutyl phthalate, ml; Density = 1.06

Crude + V ₀ BP X 1.06

Now, a glass tube with an inner diameter of 5mm and a length of 50mm is filled with the paste and this is pressed from both sides with a steel stamp of 5mm diameter and about 15cm in length. The glass tube and the punches are fixed vertically with a tripod plus clamps and the upper punch is weighted with a weight of approx. 1 kg. The electrical resistance of the pressed paste is now continuously measured:

The resistance values decrease over time and after 2V2 to 4 hours a stable value is displayed. This resistance R _p (ohms) is logged.

The length 1 (cm) of the paste drop is measured.

Rp = SpX with 1 = length in cm

^s s = cross section of the glass tube cm ³ .

From this, S _p [Cl cm ] can be calculated.

The reproducibility of the method is within ± 10%.

The advantage of the method is that no high pressure is necessary and that the pressure exerted has little effect on the result.

Claims (7)

1. A process for the production of low ash and electrically conductive carbon black by partial combustion and pyrolysis of liquid fuel with an oxygen-containing gas in a reactor, characterized in that the liquid hydrocarbon is preheated and passed together under pressure and the oxygen-containing gas having a higher temperature than the hydrocarbon in the reactor, while the feed of a gas preceding the reaction Air is introduced into the reactor, locally separate from the point of entry of the reaction components and that the partial combustion and pyrolysis takes place at a residence time which is at least about 10 seconds, after which the reaction products are cooled indirectly and stepwise outside the reactor. 2. The method according to item 1, characterized in that between the temperature of the hydrocarbon and the oxygen-containing gas, a difference of at least 15O ⁰ C prevails. 3. The method according to items 1 and 2, characterized in that for introduction into the reactor, the hydrocarbons are heated to about 120 ⁰ C at at least 15 bar pressure and oxygen gas to about 300 ⁰ C. 4. The method according to the items 1 to 3, characterized in that the reaction products at the outlet of the reactor about 800 to 1 200 ⁰ C are cooled in at least two stages by heat exchange to a filtration temperature of 150 to 300 ⁰ C. 5. Apparatus for producing ash-lean and electrically conductive carbon black by partial combustion and pyrolysis of liquid fuel with an oxygen-containing gas as reaction components, characterized in that it has a reactor with a length-diameter ratio of at least 2, which reactor means for heating the Hydrocarbons connected upstream under pressure and for heating the oxygen-containing gas and at least one heat exchanger with stepwise indirect cooling of the reaction products is connected downstream. 6. The device according to item 5, characterized in that the combustion reactor is provided with zone-wise distributed cooling tubes, which are arranged in the lining and adapted to receive a circulating in countercurrent cooling medium. 7. The device according to item 5, characterized in that the reactor is preceded by a gas-heated heat exchanger for heating the oxygen-containing gas.