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Synthesis Gas Utilization

As shown in Table 3 (Khan, 2018) synthesis gas can be produced from a variety of feed sources, with coal accounting for 48.3%. Once the synthesis gas is produced, there are several downstream processes for synthesis gas to chemicals, fuels and power.

The following discussion on conversion of synthesis gas to chemicals applies to monetization of coal as well as remote natural gas. Table 4 shows the 2018 applications (Khan, 2018) of synthesis gas.

As seen in Figure 5 (Vora, 2015), once coal or natural gas is converted to synthesis gas, it opens up a number of options for making different products. Lee (1997) provides an excellent review of various processes for methane derivatives via synthesis gas. Chang (1984) provides a good review of chemicals from methanol. The question becomes: Producing which product from which feedstock is most economical? For most petrochemical processes, raw materials account for 60-70% of the cost of production. Therefore, a first analysis requires a look at the differential between the product value and the feed cost. Table 5 shows this differential using 2018 average product values at various natural gas as feed prices. One can do a similar analysis for coal. This shows the production of olefins, ethylene and propylene via methanol has the highest differential, making methanol an important intermediate. Coal at 100S/MT is equivalent to 3.80S/mmBTU.

Table 3. Feed sources for synthesis gas production.

Feed source

% of synthesis gas production

Coal

48.3

Natural Gas

46.5

Biomass/waste

3.9

Petroleum

1

Table 4. Applications for synthesis gas production in 2018.

Application

°/o of synthesis gas used

Chemicals

74.3

Liquid Fuels

11.6

Power

3.3

Gaseous Fuels

10.6

Natural gas and coal utilization

Figure 5. Natural gas and coal utilization.

Table 5. Product-feed price differential, 2018 product value at different NG price.

Product

Product value, $/MT

Approx, tons of NG per ton of product

Differential at NG 200S/MT, = S4 nimBTU

Differential at NG 400S/MT, = $8/mmBTU

Differential at NG 800S/MT, = $16/mmBTU

Gasoline, MTG

800

1.46

508

216

-368

Diesel, FT

900

1.4

620

340

-220

Ethylene, Propylene; MTO

1250

1.46

958

666

82

Propylene, MTP

1300

2

900

500

-300

Assumption: NG to Synthesis Gas efficiency 80% Synthesis gas to Methanol-95%

MTG-90%, FT-90%, MTO-90%, MTP-65%

Methanol

From the previous discussion, it is clear that synthesis gas can play an important role in the utilization of coal or remote natural gas reserves. Since methanol is a key intermediate in this conversion, it is important to discuss developments in methanol markets and technology. The world methanol demand balance for its different uses is shown in Table 6. From 1995 to 2010 methanol production grew at an annual rate of 4.7%. The recent new application of methanol for the production of ethylene and propylene has given a further boost to methanol production, with 2018 total methanol production reaching 90 million MTA. Alvarado (2016) compared methanol uses in 2010 and 2015, as shown in Figure 6.

An interesting point to note is that in 2010, the use of methanol for the production of ethylene/ propylene via MTO MTP was negligible and is not represented on the chart. However, in 2015 at 18% it is the second largest application after formaldehyde.

There are several methanol technology suppliers. Lurgi GmbH, Davy and Haldor Topsoe are some of the main licensors (HP, 1993). Until 2000, a typical large methanol plant capacity was 2500 metric tons per day (MT D). Some trends in methanol synthesis technology are particularly important for the production of light olefins from gas. First, plant capacity is increasing significantly, as exemplified by several mega-scale plants (~ 5000 MT/D) that came into operation during the 2010s, as reported by Bonarius (2005). Second, lower feedstock costs in specific geographic areas are having a major impact on methanol production economics. Technology for the production of methanol from synthesis gas is available from several licensors (Chem System, 2012), as seen in Table 7.

The early development in methanol technology is credited to Imperial Chemical Industries Ltd. (ICI). ICI first introduced the Low-Pressure Methanol (LPM) Process in 1966. In 1994, ICI Katalco introduced the Leading-Concept Methanol (LCM) Process. Later, this became part of Johnson Matthey. The overall reaction from methane to synthesis gas to methanol can be summarized as:

Table 6. Products from methanol in 1995 and 2010.

Product, 1000 metric tons per annum (MTA)

1995

2010

Formaldehyde

7670

14880

Acetic acid

1730

4800

MTBE

8030

5280

Ethy'lene-Propy'lene

0

1920

DME, Gasoline blending

480

9600

Other

6590

12520

Total

24500

49000

Methanol applications in 2010 and 2015

Figure 6. Methanol applications in 2010 and 2015.

Table 7. Major methanol technology licensors.

Methanol technology licensor

% Share by no. of plants

% Share by capacity

Davy Process and Johnson Matthey (JM)

24

30

JM/Uhde

5

2

JM/Jacobs

8

7

Lurgi

25

31

Mitsubishi Gas Chemical

12

18

Haldor Topsoe

15

3

JM/Toyo

3

4

Other

8

5

Synthesis gas is processed over a fixed bed of catalyst forming methanol and water. Two reactor types are most popular: An adiabatic reactor with multiple quenches of a cold stream (ICI system) or a multi-tubular reactor with internal heat exchange (Lurgi system). Both types are operated at a temperature range of 200-280 °C and low pressure of 5-7 MPa using Cu ZnO/AfO. catalyst. More details are given by Lee (1990). Typical methanol properties and specifications are shown in Table 8.

Methanol production economics

Capital investment costs and the feedstock costs vary significantly for different geographic areas. In some parts of the Middle East, the natural gas price in 2018 was 1.00-1.5OS/imnBTU. In the USA it ranged between S2.50 to $4 per nmiBTU. It was over $8 to $12 per mmBTU in China, Japan. India and other Asian countries where LNG is imported.

During the 1980s-l 990s, high feed cost units in North America and Western Europe led to significant capacity shut downs. By 1990, all production in Japan was shut down (Chem System, 2012). Subsequently, almost all new methanol units were located where natural gas was relatively low in cost, typically in the Middle East and South America. This development led to a dramatic change in the methanol industry. Since 2010, with the development of shale gas, methanol production in North America is reviving again. At the same time, China has been aggressively moving into chemicals from coal, where methanol is a key intermediate. This led to significant coal-based production of methanol in China. As was seen earlier, in Table 2, from 2000 to 2018 the coal price has ranged between 30 and 110 dollars per ton (BP. 2019). Table 9 shows the cost of methanol production for a unit producing 5000 metric tons of methanol per

Table 8. Methanol properties and specifications.

Properties

Value

Formula

CHjOH

Molecular Weight

32.04

Specific Gravity

0.7924 g/cc

Viscosity at 20 C

0.00592 poise

Vapor Pressure at 20 C

92 mmHg

Freezing Point

-97.8 °C

Boilmg pomt

64.7 °C

Methanol specifications

Grade AA

Methanol nun wt%

99,85

Acetone max wt%

0.002

Aldehyde max vt%

0.001

Ethanol max wt%

0.001

Acidity (CH.COOH) max wt%

0.003

Appearance

Free of opalescence, suspended matter and sediment

Carbouisable substances

Not darker than color standard No. 30 of ASTM D1209 Pt/Со scale

Color

Not darker than color standard No. 5 of ASTM D1209 Pt/Со scale

Permanganate Fadmg Tune, Minutes

30

Water max wt%

0.10

Table 9. Methanol production economics m 2018.

Feedstock

Coal China

Coal USA

Natural gas China

Natural gas USA

Natural gas ME

Feedstock Cost

100 S/MT

70 S/MT

10 S/muiBTU

3.5 S/mmBTU

2 S/mmBTU

Total Capital Investment, SMillion

1240

1500

930

1160

1260

Operating Cost, $/MT

Raw Material

122.82

99.78

390

140

86

Utilities

147.94

51.53

8

5

10

Fixed Cost

38,09

41.93

26

30

33

Cash Cost of Production

173.47

193.24

424

175

79

Depreciation

60.61

74.40

43

58

63

Return on Capital

74.36

89,76

56

70

76

Total Cost of Production

443.82

357.40

523

303

267

day. based on 2018 coal prices in China and the USA and 2018 natural gas prices in China, Middle East and the USA.

 
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