Naphtha Hydrodesulfurization Process

Naphtha is hydrodesulfurized to make the feed suitable for subsequent treatment; catalytic reforming to improve octane or steam reforming for hydrogen production. In the first case, this takes the name pretreatment. The process consists of treating the feed with hydrogen in the presence of a catalyst under suitable operating conditions to remove feed contaminants (see Figure 2-2).

The naphtha feed enters the unit through charge pump P-101. It is mixed with hydrogen gas coming from a cat reforming unit or hydrogen plant. The feed/hydrogen mix is next heated in succession through heat exchange with reactor effluent in E-101 and fired heater H-101. The heated feed/hydrogen mix next enters the desulfurization reactor V-101 at the top. The desulfurization reactions take place over a Co-Mo on alumina catalyst contained in the reactor. The reactor effluent contains the desulfurized naphtha, excess hydrogen, H2S, and light end elements formed as a result of reaction of sulfur in the feed with hydrogen in the presence of the catalyst.

FEED HEATER

HOS REACTOR

FEEWEFRUEWT HEflT EXCHANGER E-101

EFFLUENT TRIM

COOLER

E-103

HP SEPARIOR

FEED HEATER

HOS REACTOR

FEEWEFRUEWT HEflT EXCHANGER E-101

EFFLUENT TRIM

COOLER

E-103

HP SEPARIOR

Hydrodesulfurization Reactor Design

NAPHTHA FEED

«YOSOGfN

COMPRESSOR

C-10t

Figure 2-2. Naphtha HDS unit.

NAPHTHA FEED

«YOSOGfN

COMPRESSOR

C-10t

Figure 2-2. Naphtha HDS unit.

The reactor effluent is cooled and partially condensed through feed/ effluent heat exchanger E-101, an air cooler E-102, and a trim cooler E-103, before flowing into high-pressure separator V-102. The separation between the vapor and liquid phases occurs in this separator drum. The vapor from this drum containing H2S, light hydrocarbons formed as a result of desulfurization reactions, and excess hydrogen are purged and sent out of unit's battery limit.

The liquid from V-102 is preheated through a heat exchange with the stripper bottom in heat exchanger E-105 before charging to the stripper column V-103, where the dissolved hydrogen and H2S contained in the HP separator liquid is removed as overhead product. The gross overhead product from V-103 is partially condensed through heat exchanger E-104. The uncondensed vapor, containing most of the separated H2S, is sent to an amine unit for H2S recovery. The liquid is refluxed back to the column through pump P-103.

The column is reboiled with a fired heater H-102. The bottom recirculation is provided by P-102. The stripper bottom product is cooled by heat exchange with incoming feed in E-105 and next in E-106 to 100°F before going out of unit's battery limits.

Operating conditions of a naphtha HDS unit for preparing cat reformer feed are shown in Table 2-2. Corresponding feed and product properties, unit yields, and utility consumption are shown in Tables 2-3 to 2-5.

Table 2-2 Naphtha HDS Operating Conditions

OPERATING PARAMETERS

UNITS

REACTOR INLET TEMPERATURE

SOR

°F

608

EOR

°F

698

TOTAL PRESSURE AT SEPARATOR DRUM

psia

303

HYDROGEN PARTIAL PRESSURE AT REACTOR OUTLET

psia

160

LIQUID HOURLY SPACE VELOCITY (LHSV)

hr~'

4.00

HYDROGEN CONSUMPTION

scf/bbl

45

CATALYST: CO-MO ON ALUMINA SUPPORT TYPICAL COMPOSITION AND PROPERTIES: CO = 2.2%, MO = 12.0% SURFACE AREA = 225 m2/gm PORE VOLUME = 0.45 cm3/gm CRUSH STRENGTH = 30 kg

CATALYST: CO-MO ON ALUMINA SUPPORT TYPICAL COMPOSITION AND PROPERTIES: CO = 2.2%, MO = 12.0% SURFACE AREA = 225 m2/gm PORE VOLUME = 0.45 cm3/gm CRUSH STRENGTH = 30 kg

Table 2-3

Naphtha HDS Feed (Sulfur-Run) and Product Properties

Table 2-3

Naphtha HDS Feed (Sulfur-Run) and Product Properties

QUALITY

UNITS

SULFUR GRAVITY

0.734

TBP DISTILLATION

IBP

op

194

10%

°F

203

30%

op

221

50%

op

239

70%

op

257

90%

op

275

FBP

op

284

HYDROCARBON TYPE

PARAFFINS

VOL%

69

NAPHTHENES

VOL%

20

AROMATICS

VOL%

11

TOTAL SULFUR

Wt%

0.015

MERCAPTAN

SULFUR

Wt%

0.008

TOTAL NITROGEN

ppmw

1

MOLECULAR WEIGHT

111

PRODUCT SULFUR

ppmw

0.5

IBP = INITIAL BOILING POINT; FBP = FINAL BOILING POINT.

IBP = INITIAL BOILING POINT; FBP = FINAL BOILING POINT.

Table 2-4 Naphtha HDS Unit Yields

YIELD WEIGHT FRACTION

FEED

NAPHTHA FEED 1.0000

HYDROGEN 0.0080

TOTAL FEED 1.0080 PRODUCTS

ACID GAS 0.0012

H2 RICH GAS 0.0110

LPG RICH GAS 0.0058

HYDROTREATED NAPHTHA 0.9900

TOTAL PRODUCT 1.0080

Table 2-5

Naphtha HDS Unit Utility Consumption per Ton Feed

Table 2-5

Naphtha HDS Unit Utility Consumption per Ton Feed

UTILITY

UNITS

VALUE

FUEL GAS

mmBtu

0.4330

STEAM

mmBtu

0.3680

POWER

kWhr

10.0000

COOLING WATER

mig

1.0600

DISTILLED WATER

mig

0.0025

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Responses

  • patricia
    What is naphtha hds unit?
    8 years ago
  • belladonna
    What move to make if naphtha IBP is high?
    7 years ago

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