INTRODUCTION

Claus plant sulfur recoveries (97-98%) are not high enough to comply with increasingly stringent environmental legislation. To achieve compliance, several Claus Tail Gas Treatment (TGT) processes have been developed.

We provide catalysts for reductive TGT processes enabling overall sulfur recoveries in excess of 99.9%.

We have a long history concerning TGT catalysts. From the original TG 103, for which a 12-year service life has been demonstrated in conventional reductive Claus TGT units (more than 50 units in operation), to the newest TG 107 and TG 136, the most active CoMo catalysts specially conceived for low temperature processes.

Reducing the inlet temperature to the hydrogenation reactor is a top priority considering the cost of fuel to fire these units and the corresponding CO2 emissions. Maintaining high TGTU performance while lowering reaction temperatures and CO2 footprint requires extremely active catalysts such as TG 107 and TG 136.

NEW TG 107 & TG 136 TGT CATALYSTS

CoMo catalysts TG 107 and TG 136 combine an excellent activity for Sx, SO2, COS and CS2 hydrolysis and hydrogenation reactions and the CO-shift conversion reaction.

TG 107 is a new catalyst based on extensive experience acquired with TG 103. TG 103 has demonstrated exceptional stability due to its high

surface area, optimized pore structure and CoMo content. TG 107 is a promoted spherical catalyst with a highly dispersed active phase.

TG 136 has a higher CoMo content associated with an extra high purity alumina trilobe extrudate carrier and is available in 1.2 and 2.5 mm diameter sizes.

The 1.2 mm extrudate provides the highest possible performance whereas the 2.5 mm catalyst is available when pressure drop is an issue.

Some key physical characteristics of our TGT catalysts are shown in the hereafter table:

TG 103 TG 107 TG 133 TG 136

Shape Spheres Spheres Trilobes Trilobes

Diameter, mm 2 to 4 2 to 4 2.5 2.5

Surface, m2/g 215 215 0.44 230

Loading density

Dense, kg/l 0.79 0.79 0.53 0.69

Sock, kg/l 0.76 0.76 0.44 0.59

Key physical characteristics of TG series catalysts

TG 107 and TG 136 catalysts can be supplied in the oxide form requiring in-situ activation or in pre-activated state for immediate start-up of the unit.

Pre-activated products can also be provided in a passivated form for handling under atmospheric conditions.

TG 107 & TG 136 LOW TEMPERATURE CLAUS TAIL GAS TREATMENT CATALYSTS

COMPARATIVE TESTS

TG 103 is widely employed in a variety of conventional units. Comparative tests with the new TG 107 and TG 136 catalysts were performed on identical feeds, under equivalent operating conditions and at various temperatures (isothermal reactors). Catalysts were sulfided at 240°C. Feeds correspond to typical tail gas streams on which harsher conditions were imposed: • Low H2 content • High space velocity • High COS/CS2 content • High Sx vapor content • Introduction of methyl-mercaptan

The test results reported in the figures hereafter show a substantial increase in performance for TG 107 and TG 136 compared to TG 103:

0

10

20

30

40

50

60

70

80

90

100

300 240 220 200Operating Temperature, °C

SO2

conv

ersi

on, %

TG 103 TG 107 TG 136

Effect of temperature on SO2 conversion

0

10

20

30

40

50

60

70

80

90

100

300 240 220 200

Operating temperature, °C

CS2

con

vers

ion,

%

TG 103 TG 107 TG 136

Effect of temperature on CS2 conversion

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

300 240 220 200

Operating temperature, °C

CO

S co

nver

sion

, %

TG 103 TG 107 TG 136

Effect of temperature on COS conversion

0

10

20

30

40

50

60

70

80

90

100

300 240 220 200

Operating temperature, °C

CO

shi

ft co

nver

sion

, %

TG 103 TG 107 TG 136

Effect of temperature on CO shift conversion

TG 107 catalyst

RESULTS FROM COMMERCIAL UNITS

First commercial unit

Based on the comparative tests, the first commercial unit to use low temperature TGT catalyst began operating with TG 107 in mid-2004 and has operated ever since with the following results: • Inlet temperature 215-220°C • Delta T located in the top third of the catalytic

bed • No reduction in pH • Overall performance > 99.8%

Industrial experience in the U.S.

TG 107 catalyst has been loaded in a US SRU unit in mid-2007.

This unit had operated historically with a reactor inlet temperature above 300°C. Since the start-up with TG 107, it has run between 230-240°C with minimal stack SO2 emissions as shown hereafter:

Sulfur Plant Compliance

0

20

40

60

80

100

120

140

Time on stream (days)

Cor

rect

ed o

utle

t SO

2 co

nten

t (pp

m)

140

160

180

200

220

240

260

Inle

t tem

pera

ture

(°C

)

Outlet SO2 content vs TGTU inlet temperature

Debottlenecking case

TG 107 was installed at the end of 2006 in a unit linked to a coal gasification process that produced increasing quantities of CO2. The in-line burner became a bottleneck as it could no longer heat the tail gas to the required conventional inlet temperature between 280 and 300°C.

By simply replacing the existing catalyst with TG 107 and operating the reactor inlet temperature at 240°C, the plant can now process the required amount of acid gas.

TG 136 catalyst

EASIER OPERATION AND LOWER INVESTMENTS AND OPERATING COST

With TG 107 and TG 136, we offer improved catalysts and more. By operating the Claus TGT hydrogenation reactors at lower temperatures, the operator is free to use lower pressure steam re-heaters and reap significant operating and economic benefits:

Steam re-heaters (600 psig or 40 bars)

• No superheated 80 bar steam required • Non sooting burners • No oxygen slippage • Lower CO2 emissions • No burner control problem any more • Easier operation

Energy savings Tail gas from a typical Claus unit enters the TGT hydrogenation section at 120-150°C. Reducing the inlet TGT reactor temperature from its historical level of 280-300°C to 220-240°C results in fuel (energy) savings of 30 to 50%. Through these energy savings alone, the catalyst can pay for itself very rapidly. Additional benefits include:

Operating cost savings downstream from the reactor

• Less fuel on incinerator • Lower CO2 concentration • Less gas flow saving blower energy • Quench water and amine flows reduced

Longer catalyst service life

• Lower temperature operation results in a reduced rate of hydrothermal ageing

• Considerably lower risk of catalyst problems due to misoperation: soot formation and oxygen slippage are eliminated

• Catalyst damage due to higher SO2 inlet concentrations will be reduced

WHEN SHOULD TG 107 AND TG 136 BE USED?

• To save investment cost for new units

• To reduce operating cost for new and existing units

• To reduce energy consumption

• When debottlenecking is required to reduce pressure drop or to increase re-heater throughput (for lower temperature and gas flow rate)

• When there is presence of BTX in the feed: at low temperature operation there is no cracking and much lower risk of catalyst plugging

• To reduce CO2 emissions

COMMERCIAL EXPERIENCE

Our low temperature TGT catalysts have today extensive industrial experience in SRU worldwide:

• Forty-one (41) units with TG 107 • Thirty-two (32) units with TG 136

Oct

12 –

TG

107-

TG13

6