Camere Process

Abstract-

A pilot plant to produce methanol by CO2 hydrogenation has been constructed with the government research fund in participating with POSCO and Korea Electric Power Research Institute (KEPRI). The pilot plant is consisted of a reverse water gas shift reactor and a methanol reactor. Two reactors are serially connected to remove water in the first reactor and then, synthesize methanol in the second reactor. The production capacity of the plant is 100 kg methanol per day. The methanol production yield in CAMERE Process is higher than twice as compared with the yield in the direct hydrogenation of CO2 into methanol without reverse water gas shift reaction. The pilot plant for methanol synthesis from CO2 was combined with the pilot plant for separation of CO2 discharged from a power plant.

Introduction-

The CAMERE process (Carbon dioxide hydrogenation to form methanol via a reverse-water gas shiftreaction) was developed to fix CO2 into methanol. The reverse water gas shift reactor and the methanol synthesis reactor are serially aligned to form methanol by CO2 hydrogenation. Carbon dioxide is firstly converted to CO and H2O via the reverse water gas shift reaction (RWGSR) and then, the water is removed from the reactant gas before injection into the methanol reactors. The higher the conversion of CO2 to CO is in the RWGSR, the higher the methanol productivity can be increased, because methanol yield is dependant on the CO concentration in the CO2/CO/H2 mixture gas. Therefore, the volume of the recycle gas in the methanol synthesis reactors can be minimized by increasing the conversion of CO2 to CO in RWGSR as compared with the direct CO2 hydrogenation into methanol.1 The RWGSR should be carried out at higher temperature than 600 °C to obtain CO2 conversion over 60 % in the thermodynamic point of view.2 Therefore, development of an active and stable catalyst for the RWGSR at higher temperature than 600 °C was a critical requirement for the CAMERE process.

The water-gas-shift reaction has been studied intensively for the last several decades in order to adjust H,/CO ratio in the synthesis gas. On the contrary, a reverse-water-gas-shift reaction has attracted little attention because of little demand. The Fe;0yCr;03 catalyst is a well-known commercial catalyst for the water-gas-shift reaction. The commercial catalyst,Fe0,/Cr;O, was not a good candidate for the RWGSR of the CAMERE process because of severe deactivation. Deactivation of the catalyst was attributed to the reduction of FezO to the Fe metal. On the other hand, a new type of catalyst, ZnAlOs, for the RWGSR was developed, which showed good activity and stability without coke formation.In this paper,ZnAl;04 catalyst was optimized for RWGSR and the pilot plant was operated using the ZnAlOs and Cu/ZnO/Al;0, catalysts.

 

Experimental-

The CAMERE process (Carbon dioxide hydrogenation to form methanol via a reverse-water gas shift reaction) was developed to fix CO2 into methanol. The reverse water gas shift reactor and the methanol synthesis reactor are serially aligned to form methanol by CO2 hydrogenation. Carbon dioxide is firstly converted to CO and H2O via the reverse water gas shift reaction (RWGSR) and then, the water is removed from the reactant gas before injection into the methanol reactors. The higher the conversion of CO2 to CO is in the RWGSR, the higher the methanol productivity can be increased, because methanol yield is dependant on the CO concentration in the CO2/CO/H2 mixture gas. Therefore, the volume of the recycle gas in the methanol synthesis reactors can be minimized by increasing the conversion of CO2 to CO in RWGSR as compared with the direct CO2 hydrogenation into methanol.1 The RWGSR should be carried out at higher temperature than 600 °C to obtain CO2 conversion over 60 % in the thermodynamic point of view.2 Therefore, development of an active and stable catalyst for the RWGSR at higher temperature than 600 °C was a critical requirement for the CAMERE process.

The water-gas-shift reaction has been studied intensively for the last several decades in order to adjust H,/CO ratio in the synthesis gas. On the contrary, a reverse-water-gas-shift reaction has attracted little attention because of little demand. The Fe;0yCr;03 catalyst is a well-known commercial catalyst for the water-gas-shift reaction. The commercial catalyst,Fe0,/Cr;O, was not a good candidate for the RWGSR of the CAMERE process because of severe deactivation. Deactivation of the catalyst was attributed to the reduction of FezO to the Fe metal. On the other hand, a new type of catalyst, ZnAlOs, for the RWGSR was developed, which showed good activity and stability without coke formation.In this paper,ZnAl;04 catalyst was optimized for RWGSR and the pilot plant was operated using the ZnAlOs and Cu/ZnO/Al;0, catalysts.

 

Result and Discussion-

ZnAl;O, catalysts were prepared by a coprecipitation and the activity of the
prepared catalysts for RWGSR was dependent on the pH of the solution (Figure 1). The
ZnAl;O4 catalyst prepared at pH=7 shows the highest activity as compared with catalysts
prepared at acidic condition. Especially, ZnAl,04 catalyst prepared at pH =5.4 shows lower
activity and broaden diffraction pattern. We obtained the ZnAl;O, catalyst with the highest
activity at plH-7.

Figure 1. cO conversion and the X-ray diffractogram of ZnAl;04 catalyst depending on the
preparation pH. (a) pH-5; (b) pH=6.0; (c) pH-6.4; (d) pH=7.0
Figure 2 shows CO conversion with respect to GHSV over ZnAl,O4 catalyst
prepared at pH-7. The dashed line is the equilibrium conversion for RWGSR. When the
reaction temperature is increased, CO, conversion over ZnAl,0, catalyst approaches to the equilibrium conversion.Most oxide catalysts show high catalytic activity for RWGSR at atmosphere pressure, but are rapidly deactivated because the RWGSR condition is very reductive above 400°C and the reactant ratio of H/CO 3/1.23 Moreover, it should be operated above 600C to obtain higher Cco2 conversion than 60%.

Therefore, the stability of the catalyst at the high temperature is very important in the
practical point of view. The activity of ZnAl;O4 was rarely decreased at 700°C operation fo
9 days with fecd rate of 150,000 ml/ge.h so it turns out to be very stable catalyst as
compared with Fe:0y/Cr;0 and Cr:O/Al,O3 oxide catalyst.*
The pilot plant for CAMERE process to obtain methanol from CO hydrogenation
was constructed based on the detail PED (Process Flow Diagram) and P&ID (Piping and
Instrument Diagram). Figure 3 shows the simple schematic process flow diagram and Figure
4 shows the picture for CAMERE process.

 CO2 and H, is mixed in D-105 for the H/C0 ratio of 3, which is injected into the reactor is through HE-101 for RWGSR. After RWGSR, the produced water is removed through HE 102 before injection into the diaphragm compressor.The mixed gas of H/CO/CO is compressed into the operation pressure for methanol synthesis.

And the mixed gas from the RWGSR With part of recycled gas is fed into methanol reactor of
R-201. Part of recycled gas is fired in the FN-101 to regulate the reaction conditions. The
temperature of the four fixed bed reactors was well controlled by steam in the temperature
range of 250-300°C for methanol production.
The pilot plant has been operated to obtain the optimum reaction conditions and the data for
the evaluation of the methanol production cost. To evaluate the effect of the RWGSR on the
methanol production yield, the pilot plant was operated in the RWGSR (On) or RWGSR(OM.
RWGSR (On) means that the RWGSR was operated at the temperature range of 600-700°C.
On the contrary, RWGSR (O) means that the RWGSR was not operated during methanol
production so HyCO-3/1 was just injected into the methanol reactor. Table 1 distinctively
shows the effect of the reverse water-gas shift reaction on the methanol production yield. The
methanol yield in the RWGSR (On) becomes more than twice in comparison with the yield
in the RWGSR (OfM) at the same reaction conditions. Moreover, the CO2 conversion over the
ZnAl;O4 catalyst was about 35% in the RWGSR (On). It is worth noting that the reverse
water-gas shift reaction shows a significant effect on the increasing of the methanol yield.

CAMERE Process was simulated using the simulation program of Aspen Plus and
the state equation of UNIFAC based on the 2000 tons methanol production in a year. The
construction cost for the plant was evaluated based on the Guthrie's Modular Method. The
methanol production cost was calculated depending on the hydrogen cost and methanol production capacity as shown in the figure 5. The methanol production cost proportionally
increases with hydrogen cost in market and dramatically decreases up to 50,000 tons of methanol production capacity and then, becomes stable with the production capacity.
It indicates that methanol can be produced with 300USS/ton from CO2 hydrogenation through CAMERE process if a commercial plant of 100,000ton/year is constructed. It also means we cannot economically produce methanol from CO hydrogenation because the
methanol is sold at 100-150 USS/ton in the recent market. To become an economical process,the target material of the CAMERE process should be changed into another one having a
value added, for example, DME (Dimethyl ether).

 On the other hand,the methanol production cost of 300USS/ton calculated here would be a standard value for carbon dioxide sequestration process. In addition, whenever the carbon tax starts to work,CAMERE process to sequestrate carbon dioxide should be evaluated based on the real situation.

Figure 5. Methanol production cost via CAMERE Process depending on hydrogen cost and methanol production capacity.

Conclusion-

Methanol yield of 70 % was obtained from the pilot plant for CAMERE process.
Methanol of 75kg was produced in a day from the pilot plant for which about the 100kg of
cO was consumed. Based on the results, we estimated the methanol production cost
depending on the hydrogen cost and methanol production capacity. Operating cost of about
300USS was requested for Iton methanol production through CAMERE process.