Naphtha (35–180˚C) (95–356˚F)
Alcohol or ole ns
35–85˚C
H , H S C –C
Isomerisation
25–50%
Benzene reduction
Hydrotreater
Methaformer 5 atm (73 psi) 370˚C (700˚F) 50–75%
Stabili s er
Naphtha
Gasoline
Gasoline blendstock* 90–92 RON <1% benzene / sulphur 1 10
Reforming
85–180˚C
Figure 2 Conventional naphtha processing highlighting individual units replaced by Methaformer
Water
FCC dry gas are upgraded in a unit similar to a hydrotreater at modest pressure and temperature. The product is similar to reformate: a gasoline blendstock with relatively low sulphur and, importantly, <1% benzene. The process flow resembles a hydrotreater in which ethanol/ethylene is used instead of hydrogen without a recycle compressor. The yields are comparable to a semi-regen reformer plus isomerisation, except that most of the benzene is converted to toluene, and half the ethanol becomes water. Byproducts include hydrogen, some light ends, and H 2 S in the overhead. The inexpensive zeolite catalyst does not contain precious metals. The capital and operating costs are comparable to a single hydrotreater. The operating costs are much lower than conventional processes (see Figure 2 ) because the Methaformer replaces four units. The Methaformer can upgrade most naphthas and reduces sulphur by 90%, thereby avoiding the need for a hydrotreater and hydrogen supply to this unit. It replaces the reformer and, because of low benzene production, avoids the need for benzene reduction steps. Methaforming also effectively processes light naphtha, thereby Figure 1 Methaforming: one-step process to upgrade naphtha and ethanol/ethylene
eliminating the need for an isomerisation unit. In this way, capital and operating costs are reduced to about one-third. Table 1 shows the economics for converting a 20K BPD (860K tpa) semi-regen reformer into a Methaformer. • The second column shows the economics for Methaforming. First, the yields including net fuel gas, then CO 2 credits, followed by other operating expenses, and finally, the estimated Capex is $20 million. Then, the bottom row shows the total 20-year net present value (NPV) for a Methaformer • The third column shows the same values for an existing naphtha hydrotreater plus a semi- regen reformer without isomerisation • The last column shows the difference between Methaforming versus this alternative. The Methaformer has $31 million/year better yields plus an additional $22 million/year for a reduction in CO 2 emissions (valued at $50/t) when using ethanol/ethylene as the co-feed • The fixed and variable Opex is $10 million/ year lower because of less equipment. The lower fuel gas requirements are incorporated into the yields. Finally, the Capex for the conversion to Methaforming is approximately $20 million. This gives an NPV difference of $400 million. The CO 2 emissions reductions occur to the extent ethanol or ethylene are used as a co-feed. When ethylene is used as the co- feed, the process is called Aroforming. For a Methaformer/Aroformer, the co-feed is 15- 50% of the naphtha quantity and can be any mix of light alcohol or light olefins. To what extent ethylene is the co-feed, there are added economic benefits, as highlighted in Table 3 .
Existing 860K tpa
Metha- Semi-regen ∆ Methaforming
unit (20K BPD)
forming
reformer
semi-regen
Yields, $million/yr
126
95
+ 31 + 22 - 10
CO 2 credits
22
0
Opex, $million/yr Capex, $million Total NPV, $million
13
23
20
-
20
890
490
+ 400
Table 1 Economics for converting semi-regen reformer into a Methaformer
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