DE2054125B2 - INTEGRATED FLUID BED COOKING AND GASIFICATION PROCESS - Google Patents

Description

The invention relates to an integrated fluidized bed coking and gasification process for the production of Coke and gases containing hydrogen and carbon monoxide, in which three separate from each other Fluidized bed zones each with different temperatures with regard to the heat and material balance are integrated.

In conventional fluid coking, the carbonaceous feedstock is injected into a fluidized bed of coke, where it is cracked into vapors and coke. The vapors are passed through a cyclone to a washer / fractionator, where they are fractionated into gas, naphtha and oil products and a heavy flow, which is returned to the coke reactor ¹ . A circulating coke stream is taken from the bottom zone of the reactor and brought into a coke burner, where enough air is blown to burn some of the coke and heat the rest sufficiently to provide the necessary heat in the coking reactor when unburned hot coke is in this is returned. The remainder of the unused coke in the incinerator is withdrawn as coke end product.

The coke obtained in this way is difficult to utilize, so that attempts have been made to increase its value by subsequent treatment, for example by high-temperature calcining and briquetting. Optionally, the coke can also be converted into a _{gas enriched in H 2} and CO in a subsequent process step by reaction with steam and an oxygen-containing cast. So far, these additional coke processing methods have not been economically viable. If, in addition, common crude oil residues were processed in a fluidized bed coking plant, the combustion products cut an undesirably high SO?

In de, · US-PS 26 05 215 is a two-stage process described in which the coking of kohlenstoffiü containing feedstock and the gasification of the coke produced during coking are. A part of the product gas produced during the gasification is namely directly into the coking zone passed in order to supply heat there for the coking process ι-s.

Furthermore, from US-PS 34 59 655 a process is known in which hydrocarbons are ^{injected into a low-temperature coking zone (482 to 760 °} C.) and cracked. The products are then passed into a high temperature ^{coking zone (] 427 C} C) to produce a hydrogen-enriched gas and coke. The heat required for the entire process is supplied to the high-temperature coking zone by circulating the coke in the diluted phase through an externally heated heater for 2 seconds. For this purpose, a fuel, for example hydrogen or natural gas, is burned with oxygen and the hot combustion gases are brought into contact with the coke. The coke is circulated through the heater in a diluted phase as a ίο gas / solid system. The coke is used as a heat carrier to transport heat into the high-temperature coking zone and from there to the low-temperature coking zone.

The invention is now based on the object of providing a coking process that is good on the one hand Recyclable products with the exclusion of air pollution problems results and on the other hand is much more economical than due to optimal utilization of the heat generated in the coke gasification previously known procedures.

To solve this problem, an integrated fluidized bed coking and gasification process for the production of coke and gases containing hydrogen and carbon monoxide, in which
a) a carbonaceous material is introduced into a fluidized bed coking zone,
b) a portion of the coke is transferred to a fluidized bed heating zone for heating to a temperature higher than that of the coking zone and
c) some of the heated coke is returned to the coking zone,

proposed, which is characterized in that another part of the coke heated in the heating zone is passed into a low pressure gasification zone, where it is filled with steam and an oxygen-containing gas Contact is made, whereupon the gases and the entrained coke are passed into the heating zone and the gases are removed from the heating zone and recovered.

According to the invention, the conventional coke burner is through in conventional fluidized bed coking processes replaces an integrated heating and gasification zone, each of which has fluidized coke beds and are separated from one another by a grid or in some other way. The coke is in the lower zone, namely the gasification zone, in the presence of steam and air or commercially pure Oxygen-forming gases gasified. The hot ones

Product gases from coke gasification flow into the overlying heating zone, in which they apply their heat to the "cold" coke from the coking zone hand over. The coke heated in this way is then used to supply the heat required for coking returned to the coking zone and to .τι part in introduced the gasification zone. Alternatively, the gases from the gasification zone can be circulated with the Coke from the reactor is combined and passed through a transfer line into a separation vessel from which the hot coke is then fed back into the coking zone. May be a negligible amount of fine coke particles was carried along in the gases emerging from the gasification zone will. However, this small amount of entrained fine coke particles cannot act as a carrier significant amount of heat. So mainly act as heat exchangers hot, gaseous products from the gasification zone.

If necessary, air, O2 or other oxygen-containing gases can be fed into the heating zone to burn some of the CO and hydrogen so that it enters the coking zone returned coke the required amount of heat can be supplied.

The gas obtained from the heating zone is _{enriched in H 2} and CO and is a good feed _{gas for generating a concentrated H 2} stream due to the known water-gas equilibrium reaction or for other chemical processes. It is also a good fuel. For most purposes it will be necessary to further treat the gases to remove sulfur, which is primarily present as H2S and which can be easily removed, for example by the Stretford process; Furthermore, ash components can be removed from the gasified coke. Valuable by-products arise during gas treatment, namely ash products enriched in sulfur and metals.

The fluidized bed coking process according to the invention can be performed so that the in the Coke generated coke is completely gasified or that a desired proportion of the resulting Coke can be obtained.

The particular advantage of the process of the invention is that suitable process conditions can be maintained and heat can be used economically by using the hot gas products from the gasification zone to heat the coke in a separate heating zone. In addition to the much greater economic efficiency associated therewith than with conventional processes, the process according to the invention also offers the advantage that the three-zone reaction system achieves better and more independent regulation of coking, heating and gasification.

In the following, the invention is based on the drawing, which is a suitable in schematic form Device shows to be explained in more detail.

The carbon-containing feedstock with a Conradson carbon number of about 15%, such as, for example, a high-boiling residual oil with a boiling point above 566 ⁰ C or a hard coal slurry is via line 2 and distribution line 3 via injection lines 4, 5, 6, 7 and 8 into a Fluidized bed coking zone 1 initiated. The fluidized bed consists of coke with a particle size of 40 to 1000 μ and extends up to the upper limit L. 15 to 1.2m / sec. to achieve. Via the line 10. Coke is introduced at a temperature between 37-150 ⁰ C above the coking temperature in ausreicheridei ¹ amount in the coking zone to reach a coking temperature in the range 480-650 ⁰ C.

The lower part of the coking zone serves as a stripping zone for trapped or entrained Remove hydrocarbons from the coke. Of the

υ Coke is discharged from this stripping zone via a line U withdrawn and passed into a fluidized bed heating zone 12. The conversion products are via a Cyclone 13 passed to remove entrained solids, which via a vent 14 into the coker to be led back. The vapors leave the cyclone via line 15 and are in a Washer / fractionator 16 passed, where they are separated, into a via line 17 withdrawn gas, via line 18 withdrawn naphtha and via line 19 withdrawn gas oil. The shear flow is taken off via line 20, some of which is passed through conventional heat exchangers and is circulated in the scrubber via line 21; another part of the material is via the Line 22 fed to the coking zone. The small amount of fine solid particles released by the The reactor cyclone is running, is fed back into the coking reactor with this circulating flow.

In the heating zone 12, the so-called cold coke which has been stripped off from the reactor is passed via line 14 into a fluidized bed with hot coke which extends up to level L. This fluidized bed is heated by fuel gases which flow upwards through a distributor element 23 with a disk or perforated disk shape and baffles (egg crate baffle) 23 or 24. Hot coke is discharged from the fluidized bed in the heating zone 12 via line 25, and a portion is passed via line 26 into the gasification zone 27 comprising a bed of fluidized coke with the height L. Another part is fed back into the coking zone 1 via the line 10 in order to supply it with the necessary heat. The coke that is introduced into the fluidized bed in the gasification zone 27 is with. Steam from line 28 and air or oxygen from line 29 are brought into contact, whereby the following reactions take place:

(π + I) C + (0.5 + / ι) Ο ₂ -π
CO + V ₂ O ₂ - »CO ₂
CO ₂ + C v ^ 2CO
H ₂ O + C ^ H ₂ + CO
H ₂ O + CO ^ CO ₂ + H ₂

CO + / 1CO ₂ (1)
(2)
(3)
(4)
(5)

When the coke is oxidized, a mixture of CO and CO _{2 is} initially obtained according to equation (1) . At temperatures above 870 ° C, the CO is rapidly oxidized to CO2 in the presence of oxygen according to equation (2). After the oxygen has been consumed, the CO2 reacts with carbon to form CO. High temperatures favor the shift of the equilibrium (3) to the right with the formation of CO.

This implementation is also promoted by lower pressure. The implementation (3) takes place more slowly than the implementation (2). The equilibrium would therefore favor very high CO / CO2 ratios at 927 to 954 ° C and higher and at pressures of 2.7 atm or lower in the gasification zone. The steam also gasifies the coke according to equation (4). This reaction is slightly endothermic, and when some of the oxygen is replaced by steam , the temperature in the gasification zone drops with a constant amount of coke to be gasified. Finally, water reacts with CO to form CO2 and hydrogen according to equation (5). Most of the sulfur in the coke is converted into H2S, with only small amounts of COS being formed.

The gases formed according to the above equations flow from the gasification zone through the narrow Connection part 30 upwards into the heating zone. Additional air or oxygen can be added to the Lines 3t are fed to burn a small part of these gases and the coke in the Apply additional heat to the heating zone. The gases leave the heating zone 12 via the cyclone 32, entrained coke particles are returned to the gasification zone. The gases then exit at 34 and have the following typical composition using air for Gasification:

Mol% Mol.-Vo - including except 20.6 H ₂ O + H ₂ H ₂ O + H ₂ S 8.2 M ₂ 6.5 6.8 64.4 H ₂ O 2.9 - CO 19.9 CO ₂ 7.9 N ₂ 61.9 H ₇ S 0.9

.15

• 40

100

100

The net calorific value on a dry basis is 753 kcal / m ³ . When using oxygen for gasification, a gas with the following typical composition is obtained:

MoL-% ΜοΙ, -% monotonous except H ₂ S ι H ₂ O H ₂ S ι H ₂ O H ₁ 24.2 30.9 H ₂ O 20.0 co 34.2 43.6 CO ₁ 19.8 25.3 N ₂ 0.1 0.2 N ₂ S 1.7

K) (I.

KK)

The calorific value on a dry basis is 1993.6 kcal / m ¹ . Small amounts of cracked hydrocarbons are also present in the product gas and increase the calorific value of the product gas. The amount and the composition vary somewhat depending on the nature of the feedstock for the coking reactor and on the nature of the reaction and deposition conditions.

('S If desired, some of the coke can be withdrawn as product via line 33. Agglomerates of foreign solids, which may form in some cases, can also be cleaned via this line via an elutriator, from which coke carried along can be returned to the Gasification zone can be blown back.

Although the process has been described using the circulation of coke as a fluidized bed medium, can of course also be a self-contained fluidized bed of inert particles, such as alundum or mullite, can be used in the gasification zone 27. This is an advantage when large quantities are extremely fine Particles of foreign solids are conveyed into the gasification zone, so that extremely low speeds are required to achieve a stable fluidized bed; this takes place with particles of about 10 μ and fewer. Such a self-contained fluidized bed can be easily without a noticeable entrainment of the Closed fluid bed particles at surface velocities whirl through, which are much higher than the entrainment speed of the fine ones Particles released from the coke. Such a closed fluidized bed gives a good result mixed reaction zone in the gasification zone, in which the carbon is burned and the foreign particles can be released without impairing the turbulence. A certain equilibrium concentration the fine particles remain in the fluidized bed of the gasification zone, so that a sufficient Residence time for complete gasification of the carbon is given before the main mass of the Particles are carried away by the escaping gases. The hot products of the gasification zone including the entrained solid particles flow through a heat exchanger bed, which is the Bed described in connection with the heating zone 12. In this Heat exchanger bed allows the coke from the reactor to be heated as far as is necessary for the heat balance of the reactor is required. This method is preferable when the input products are larger Have solids content than is usually found in petroleum residues such as bitumen from coal, tar sands or oil shale from the FaI! which may contain 15 to 20% inert solids. The solids how finer Sand, metal oxides or the like are made from the bitumen in the closed bed in the gasification zone released and are smaller than the coke, so they are more easily carried away and up by that Heat exchanger bed are transported away. These fine particles also flow through the usual ones Cyclones connected to the heating zone can then be electrically separated further downstream will.

example

A Kuwail residual oil boiling above 565 "C with a content of 5.5% by weight sulfur and a Conradson carbon steel of 21.8 is introduced into the fluidized bed of the coking zone 1 at a temperature of 525" C. The coke produced is introduced into the heating zone 12 at a temperature of 510 to 525 "C and heated with gases from the gasification zone 2Ί to 982 ° C. These gases are formed by a coke which is introduced into the gasification zone 27 by means of air or oxygen The gases leave the heating zone at a temperature of

620 ⁰ C after they have given their heat to the circulated coke. Virtually all of the solid material is then separated from the gases by cyclone 32. The steam to air ratio is adjusted so that the bed in the gasification zone is maintained at a temperature of about 982 ° C. The heating zone is operated under a pressure of 1.4 atmospheres and the gasification zone under a pressure of 1.76 atmospheres. The following values are obtained here:

Table 1

Working conditions and composition of the raw materials and the end product

Feed product for the coking zone speed 1908m ³ / day

Input material Kuwait 556 ° C +

Final residue

Conradson carbon, weight percent 21.8 sulfur, weight percent 5.5

Density in ⁰ API 5.7

Vanadium in ppm 113

Ni in ppm 25

Total ash in ppm 252

working conditions

Reactor temperature ^{525 0 C}

End intersection of the

Reactor product 510 ° C

Speed of

Coke circulation in t / min 15.5

Heating zone temperature 621 ° C

Printing of the same 1.41 atü

Gasification zone temperature 982 ° C

Pressure of the same 1.76 atü

Table I (continuation)

Coke composition

Gross oil

Net for gassing

Hydrogen in% by weight 6.0 14.7 2.5 Carbon in% by weight 86.6 77.9 90.1 Sulfur in% by weight 7.4 7.4 7.4 Va in ppm 410 - - Ni in ppm 90 - - Total ash in ppm 906 - -

Product gas composition

Gasification with air / steam

Gasification with oxygen / steam

Composition in mol .- '/ »

CO CO,

(CH),

N ₂ 20.4 6.6 4.4 1.4 5.0 1.2

61.0

100.0

Calorific value (HHV) in kcal / m ¹ without H ₁ S 1335

42.0 18.0 18.7

6.7 11.0

2.6

100.0

3115

Material balance in heating and gasification

Zone:

Table 2

Heat and material balance in the heating and gasification zone

Material balance: The values for the oxygen / steam gasification are given in brackets if they are from the

Air / steam gasification.

steam I.
Air or (oxygen) 2
steam 3
cold coke
from the reactor 4th
carried away
oil 5
hot coke
to the Reakloi Temperature in 'C
1000 kg / h
Moles / h 177
6030 (1070) 178
1.81 (6.35) 524
860 524
6.53 621
844

Table 2 (! • 'orlsel / ung)

Temperature in C 621

K) OO kg / h 61.7 (59.9)

v1ol / h

lr '/ min

The feedstock for the product gas of the the Veigiisuiigsz.one gasification zone

98.7

8100 (3917) 2330 (I 130) in (Ml 'gasification * - / oik · entrained coke

982 45.4 (43.5)

additional lull

(SaucrstolV)

/ ur upper zoiu

177

1630 (■! () ())

IO l'mdukli'.as

621

9980 (4445) 2370 (IOM))

20 54 9 Table 2 (continued) 125 7th Heat balance in the Heating zone Heat load Air / steam Oxygen/ Heat supplied to the steam circulating coke Crack heat for 130.0 130.0 entrained oil Heating up the steam 5.0 5.0 from the supply line Heat losses 3.4 3.4 All in all Heat supply 3.6 3.6 Gas from the 142.0 142.0 Gasification zone Entrained coke 42.0 20.1 Combustion of CO and II, in the heating zone 28.6 28.5 71.4 93.4

ίο

Total 142.0 142.0

Of course, the working conditions, the composition of the product gas and the total heat and material balance differ significantly from the above values depending on the feedstock in the gasification zone and the desired coking product.

1 sheet of drawings

Claims (5)

Patent claims: I. Integrated fluidized bed coking and grouting process for the production of coke and gases containing hydrogen and carbon monoxide, in which a) a carbonaceous material in a fluidized bed coking zone is brought in, b) part of the coke to be heated to a temperature higher than that of the coking zone transferred into a fluidized bed heating zone and c) some of the heated coke into the coking zone is returned, characterized in that another Part of the coke heated in the heating zone is passed into a low-pressure gasification zone, where it is brought into contact with steam and a gas containing oxygen, whereupon the gases and the entrained coke is passed into the heating zone and the gases are removed from the heating zone and be won. 2. The method according to claim 1, characterized in that the coking zone on a Temperature of about 482 to 549 ° C is maintained. 3. The method according to claim 1, characterized in that a pressure of in the gasification zone 2.7 atm or less is maintained. 4. The method according to claim 1, characterized in that an inert in the gasification zone Particulate-containing fluidized bed is used. 5. The method according to claim 1 to 4, characterized in that a residual oil as the carbonaceous Input product is used.