production of high-quality paraffinic distillates and vacuum resid. revamping of the avt-2 unit...

7/29/2019 Production of High-Quality Paraffinic Distillates and Vacuum Resid. Revamping of the AVT-2 Unit Vacuum Block

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Chemistry and Technology of Fuels and Oils, Vol. 41, No.3, 2005

TECHNOLOGY

PRODUCTION OF HIGH-QUALITY PARAFFINIC DISTILLATES AND VACUUM RESID.

REVAMPING OF THE AVT-2 UNIT VACUUM BLOCK

N. I. Bilyk, Yu. N. Lebedev, I. P. Khashchivskii, T. M. Zaitseva, UDC 66.048.037

and Ya. P. Lozhkin

____________________________________________________________________________________________________

Kedr Oil Transhipment Co. Galichina Oil Transhipment Co., Drogobych, Ukraine. Translated from Khimiya

i Tekhnologiya Topliv i Masel, No. 3, pp. 9 11, May June, 2005.

0009-3092/05/41030175 2005 Springer Science+Business Media, Inc.

The basic plan for revamping of the vacuum block was developed at Kedr-89 OTC and the engineering

plan for the K-8 vacuum tower was drawn up at UkrNIIkhimmash Open Joint-Stock Company (Kharkov). A

vacuum tower was manufactured and it was delivered with five blocks from Penzkhimmash OJSC. Preassembly

and installation of the vacuum tower was executed by Galichina OTC OJSC with Universal LLC. The working plan

for the vacuum-creating system was deve loped by Tekhnovakuum LLC (Moscow).

Due to the good organization and high professionalism of the executors, all of the work, including drawing

up the development documents, manufacture, preassembly, and installation of the vacuum tower, construction of

the vacuum-creating system, and startupdebugging work was completed in nine months.

The vacuum tower is designed for production of vacuum gasoil (VG), middle and heavy lube oil distillates

(MOD and HOD), and vacuum resid. The goals of the revamping were to:

Indexes VG MOD HOD Vacuum resid

Cut points, (5 95%), 75 115 75

Nominal [Engler] viscosity, E

at 50C 1.1 1.2 1.7 2 103 140*

at 100C 1.5 2.3

Density at 20C, kg/m3 872 898 915 980

Flash point (open cup), C 145** 193 243 267

Note. * Nominal [Engler] viscosity at 60 C in sec

** Closed cup.

Table 1


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3000

4000

1

2

3

4

5

6

V

IV

III

II

I

VAKUPAK packing

KEDR packing

Slit tray

Fig. 1. Diagram of the K-8 vacuum tower


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increase the quality and takeoff of paraffinic distillates by increasing the efficiency of separation;

decrease the power consumption per 1 ton of target product;

improve the environmental situation.

To solve these problems, computer modeling of the vacuum block was performed with Hysys software

at Kedr-89 OTC OJSC.

It was previously* shown that the operation of the entire heating furnacetransfer line vacuum

tower vacuum-creating system manufacturing chain must be analyzed to select the optimum operating parameters

of the vacuum block. The minimum relative investments, i.e., capital and operating, was used as the optimality

criterion.

The minimum relative investments are obtained with the following process parameters: residual pressure

above the vacuum column of 2.66-3.99 kPa; pressure differential between the feedstock input zone and the top of

the tower of 1.995-2.66 kPa; temperature of atmospheric resid at the inlet into the tower of 380-390C; consumption

of steam fed in at the bottom of the tower of 0-1 wt. %. Note that the quality of all distillates is ensured in dry

distillation of atmospheric resid and steam feed is only useful for regulating the quality of the vacuum resid.

To attain these goals of revamping and ensuring the optimum process parameters, Kedr-89 Co. developed

a modern vacuum tower design (see Fig. 1) equ ipped with efficient structured packing so that the diameters of the

new tower (3000 mm at the top and 4000 mm at the bottom) are much smaller than the diameter of the old tower (6000mm). The support of the new tower is cone-shaped, which allowed using the existing base of the old tower.

Five sections (I-V) of VAKUPAK and KEDR structured packing were installed in the tower over the feedstock

input zone. Low-pressure liquid distributors of the rectangular-cap type were used to irrigate the packing in each

section. Collecting trays with steam nozzles were installed under each packing section. To prevent entrainment of

condensed liquid from the vacuum tower, an ULTRASET safety trap developed at Kedr-89 Co. was installed under

the steam outlet connection.

Input of feedstock into the tower was organized with a special rotor structure that ensured efficient

separation of liquid and vapor. Single-flow valve and slit trays highly recommended for low steam loads and

relatively high liquid loads were installed in the lower part of the tower.

The vacuum tower operates as follows. Atmospheric resid heated in the furnace enters the tower at atemperature of 380C. Due to the low residual pressure at the top of the tower and the low packing resistance in

the feed zone, the pressure does not exceed 5.985-6.65 kPa. A high proportion of vapors is ensured in these

conditions: 45-48 wt. %. Two circulating reflux streams are provided for organization of internal reflux:

upper in packing section I and middle in section III.

The target cuts vacuum gasoil, middle and heavy lube oil distillates are taken off from blind trays in

sections I (upper), III, and IV. The zone (section V) for washing out resin and asphaltene vapors, which worsen

the color of the target products, is positioned above the feedstock input. The dark product goes out from the

blind plate in section V. Vacuum resid goes out at the bottom of the tower. For regulating its quality, steam is fed

in at the bottom of the tower. Cooled vacuum resid (quench) is fed into the tower still to maintain the temperature

below 350C.

After revamping of the vacuum block was completed, a fixed run was conducted. The material balance and

operating regime of the vacuum tower during the run are reported below:

*Yu. N. Lebedev, V. G. Chekmenev, and T. M. Za itseva, Khim. Tekhnol. Topl. Masel, No.9-10, 16 (1994).


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Consumption, tons/h

atmospheric resid 72.5

steam 0.7

Output, tons/h

vacuum gasoil 5.2

lube oil distillate

middle 21.6

heavy 4.9

vacuum resid 41.4

losses 0.1

Temperature in tower, C

at top 98

at bottom 340

Pressure in tower, kPa

at top 3.099

in feed zone 5.32

Target product takeoff temperature, Cvacuum gasoil 167

lube oil distillate

middle 241

heavy 303

The quality of the target cuts (see Table 1) satisfy the requirements of the company specifications and

standards.

The results obtained showed that the vacuum block is operating stably and efficiently. The vacuum tower

equipped with VAKUPAK and KEDR structured packing has an important output reserve and the pressure

differential at maximum atmospheric resid loading does not exceed 2.128 kPa.Revamping of the AVT-2 unit thus introduced energy-saving technology, increased takeoff, and i mproved

the quality of paraffinic distillates and vacuum resid. The real operating indexes of the vacuum block correspond

to the current world level.

production of high-quality paraffinic distillates and vacuum resid. revamping of the avt-2 unit...

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