According to a first aspect, the invention relates to a method for producing
methanol or hydrocarbons from at least one carbonaceous material
US 20 1010022669 describes a method for producing liquid hydrocarbons from a
carbonaceous material such as methane or biomass, by using a source of renewable
energy of variable power, a unit for generating oxygen (air separation unit or electrolyzer)
consuming a fraction of the electric energy, a reformer consuming the generated oxygen
and another fraction of the electric energy, and a unit for making liquid hydrocarbons from
synthetic gas produced by the reformer.
This document envisions several solutions for solv~ng the problems of the
variability of the available electric power. A first envisioned solution is to vary the amount
of oxygen provided to the reformer, in order to make the latter more or less endothermic
or exothermic and modify the electric power required for the heating. Other solutions
consist of lowering the production capacity of liquid hydrocarbons, using an additional
electric source for heating the reformer, using an additional heat source or further using
an oxygen buffer storage.
These methods are not very efficient, and make it difficult to compensate for a
significant decrease in the available long term electric power.
In this context, the invention aimed at proposing a method which is more robust,
and which may tolerate longer and more pronounced decreases in electric power.
For this purpose, the invention relates to a method for producing methanol or
hydrocarbons from at least one carbonaceous material, the method comprising the
following steps:
- producing a synthesis gas stream from the carbonaceous material according to a
method comprising at least one operation for reforming an intermediate gas stream
stemming from the carbonaceous material, the synthesis gas stream comprising at least
hydrogen and carbon monoxide, the synthesis gas having a first hydrogenlcarbon
monoxide molar ratio under first operating conditions for the reforming operation;
- producing a hydrogen stream from a hydrogenated raw material and from a first
consumed electric power, the hydrogen stream having a first molar flow rate for said first
consumed electric power;
- producing methanol or hydrocarbons from the synthesis gas stream and from the
hydrogen stream;
- lowering the consumed electric power in order to produce the hydrogen stream,
down to a second electric power lower than the first electric power, the hydrogen stream
having a second molar flow rate below the first molar flow rate for the second consumed
electric power, and being set under second operating conditions different from the first for
the reforming operation in order to compensate for the decrease in the molar flow rate of
the hydrogen stream, the synthesis gas having a second hydrogenlcarbon monoxide
molar ratio which is greater than the first under the second operating conditions.
The method may further include one or several of the characteristics below,
considered individually or according to all technically possible combinations:
- under the first operating conditions, the reforming operation is carried out at a first
temperature; under the second operating conditions, the reforming operation is carried out
at a second temperature below the first temperature;
- under the first operating conditions, the reforming operation is carried out at a first
pressure; under the second operating conditions, the reforming operation is carried out at
a second pressure below the first pressure;
- the reforming operation is carried out in a reforming unit receiving as an lnput a
plurality of inflows containing organic molecules, including the intermediate stream, the
reforming unit receiving from the different inflows, all in all, a total molar flow of carbon
atoms contained in the organic molecules and a total water H20 molar flow, the reforming
operation passing from the first operating conditions to the second operating conditions by
modification of a ratio of the total water H20 molar flow rate over the total molar flow rate
of carbon atoms contained in the organic molecules;
- the ratio of the total water H20 molar flow rate over the total molar flow rate of
carbon atoms contained in the organic molecules is equal to a first value under the first
operating conditions, and is equal to a second value greater than the first under the
second operating conditions;
- the second value is comprised between 1.1 and 5 times the first value, preferably
between 1.5 and 3 times the first value;
- the reforming operation is carried out in a reforming unit receiving as an input a
plurality of inflows, including the intermediate stream, the reforming unit receiving different
inflows, all in all, a total molar flow rate of carbon atoms contained in the organic
molecules and a total oxygen O2 molar flow rate, the reforming operation passing from the
first operating conditions to the second operating conditions by modification of a ratio of
the total molar flow rate of oxygen over the total flow rate of carbon atoms contained in the
organic molecules;
-the hydrogen stream is produced from electricity provided by an electric
distribution network serving other consumers; and
- the intermediate stream is obtained by gasification of the carbonaceous material.
According to a second aspect, the invention deals with a facility for producing
methanol or hydrocarbons from at least one carbonaceous material, the facility
comprising:
- a unit for producing a synthesis gas stream from the carbonaceous material,
comprising at least one unit for reforming an intermediate gas stream stemming from the
carbonaceous material, the synthetic gas stream comprising at least hydrogen and carbon
monoxide, the synthesis gas having a first hydrogenlcarbon monoxide molar ratio under
the first operating conditions for the reforming operation;
- a unit for producing a hydrogen stream from a hydrogenated raw material and
from a first consumed electric power, the hydrogen stream having a first molar flow rate
for said consumed electric power;
- a unit for producing methanol or hydrocarbons from the synthetic gas stream and
from the hydrogen stream;
- a programmed control unit for decreasing the consumed electric power in order to
produce the hydrogen stream, down to a second electric power below the first electric
power, the hydrogen stream having a second molar flow rate below the first molar flow
rate for the second consumed electric power, the control unit being programmed so as to
have the reforming unit pass under second operating conditions different from the first for
compensating for the decrease in the molar ratio of the hydrogen stream, the synthesis
gas having a second hydrogenlcarbon monoxide molar ratio greater than the first under
the second operating conditions.
Other features and advantages of the invention will become apparent from the
detailed description which is given thereof below, as an indication and by no means as a
limitation, with reference to the appended figures, wherein:
- Fig. 1 is a simplified schematic illustration of a facility for producing hydrocarbons
according to a first embodiment of the invention;
- Fig. 2 is a schematic illustration similar to the one of Fig. 1, for a production
facility according to a second embodiment of the invention;
- Figs. 3 to 8 are graphic illustrations of the time-dependent change in the molar
fractions on a dry basis of CH4, HZ, CO and C02 at equilibrium and of the conversion rate
of methane at the outlet of the reformer, versus the reaction temperature, at 30 bars, for
different input conditions in the reformer;
- Figs. 9 and'l0 are graphs illustrating the time-dependent change of the CO/C02
and H,/Co ratios at equilibrium, versus the reaction temperature, at 30 bars for a reformer
operating under the operating conditions of Figs. 3 to 8.
In Figs. 1 and 2, each rectangle corresponds both to a step or a sub-step of the
method of the invention, and to the corresponding industrial facility unit. The facility will be
described as comprising units corresponding to the steps or sub-steps of the method.
The facilities schematically illustrated in Figs. 1 and 2 aim at producing methanol
and/or hydrocarbons from a carbonaceous material. The carbonaceous material may
comprise one or more of the following elements:
- coal, lignite,
- municipal waste,
- animal waste,
- biomass,
- plastic materials such as polyethylene or polyethylene terephthalate etc.
This list is non-limiting.
In the exemplary embodiment of Fig. 1, the carbonaceous material is biomass.
The facility of Fig. 1 comprises at least the following units:
- a unit 10 for producing a first stream of synthetic gas from the carbonaceous
material,
- a unit 12 for conditioning the first stream of synthetic gas;
- a unit 14 for adding a hydrogen stream to the first stream of synthesis gas, in
order to form a second stream of synthesis gas;
- a unit 16 for producing a first product stream from the second stream of synthesis
gas;
- optionally a first separation unit 18, in which the first product stream is separated,
for example into a water stream, into a second product stream and into a first stream of
gas intended to be recycled;
- optionally a second separation unit 20, in which the first gas stream intended to
be recycled is separated into a gas purge stream and into first and second recycled
streams;
- a unit 22 for electrolysis of water;
- optionally an air separation unit 24.
The unit 10 for producing the first stream of synthesis gas typically comprises a
unit 26 for gasification of the biomass producing an intermediate flow, and a reforming unit
30 producing the first stream of synthesis gas from the intermediate flow.
The biomass may optionally undergo pretreatment before feeding the gasification
unit 26. This pretreatment may be a milling, drying operation or any other operation
required for putting the biomass in a suitable condition so as to be treated in the
gasification unit.
The gasification unit is selected according to the characteristics of the biomass to
be treated. It is of known type, it will not be described in more detail here. It is fed with
biomass via line 34, with water via line 36 and with oxygen via line 38. The oxygen stems
from the electrolysis unit 22 and/or from the air separation unit 24. The intermediate gas
stream leaves the gasification unit through line 28. In the gasification unit 26, the biomass
is broken down into a gas essentially comprising methane CH4, water, carbon dioxide,
carbon monoxide and hydrogen.
The intermediate stream then passes into a unit 40 for adjusting the steam level in
the intermediate stream. If the intermediate stream contains an excess of steam relatively
to the level required for proper operation of the reforming unit 30, a portion of the steam is
separated from the intermediate stream and leaves the unit 40 through line 42. The
intermediate stream leaves the unit 40 through the line 44, and feeds the reforming unit
30. The water stream leaving the unit 40 through the line 42 may feed the gasification unit
26 or the electrolysis unit 22.
The reforming unit is typically an autothermal reforming (ATR) unit or a partial
oxidation reforming (POX: Partial Oxidation) unit or a steam reforming (SR) unit. The
reforming unit 30 is supplied with the intermediate stream via line 44, and is supplied with
oxygen from the electrolysis unit 22 or from the air separation unit 24, via line 46. It also
receives the first recycled gas stream via line 48. It is optionally supplied with steam
through line 49, in the case when the intermediate stream does not comprise sufficient
steam for properly operating the reforming unit 30. The first recycled gas stream
essentially comprises CO, Cop, CH4, Hz and light hydrocarbons. In the reforming unit 30,
the methane molecules from the intermediate stream and the methane molecules as well
as the light hydrocarbons stemming from the first recycled gas stream are broken down
and converted into CO, C02 and H2.
The reforming unit produces the first stream of synthesis gas, which is directed
towards the unit for conditioning the gases 12 via line 32.
The first stream of synthesis gas in majority comprises carbon monoxide CO,
carbon dioxide COP, hydrogen Hp and water. It also comprises other gases in a smaller
amount. These other gases are i,a. non-converted hydrocarbons and impurities (H2S,
NOx, etc).
The unit for conditioning the gases 12 receives the first stream of synthesis gas
stemming from the reforming unit 30 and separates the carbon monoxide and the
hydrogen from the carbon dioxide, steam and other impurities such as H2S for example. In
the unit for conditioning the gases 12, the first stream of synthesis gas is thus separated
into a first stream of purified synthesis gas essentially containing CO and hydrogen, and
into one or several separate gas streams. The first stream of purified gas leaves the unit
12 via line 50, the separate gas streams via lines 52 and 54.
The first stream of purified synthesis gas is directed from the gas conditioning unit
12 as far as the unit 14 for adding hydrogen, via line 50. The separate gas streams,
before being discarded into the atmosphere, may undergo a treatment for example aiming
at recovering the steam so as to feed the electrolysis unit 22 or the gasification unit 26.
The COP may be discharged into the atmosphere or recycled or stored.
In the unit 14, a determined amount of hydrogen is added to the first stream of
purified synthesis gas so as to form a second stream of synthesis gas. The hydrogen
stems from the electrolysis unit 22 via line 56. In the unit 14, the second stream of
recycled gas is also mixed with hydrogen and with the first stream of purified synthesis
gas. The second stream of recycled gas feeds the unit 14 via line 58. This second stream
mainly comprises H2 and CO, and smaller amounts of C02, methane and light
hydrocarbons. The second stream of synthesis gas leaves the unit 14 via line 60 and
feeds the production unit 16.
The production unit 16, in the exemplary embodiment of Fig. 1, operates according
to the Fisher-Tropsch process. In this unit, the carbon dioxide CO reacts with hydrogen for
producing hydrocarbons. This reaction is catalyzed with suitable catalysts. The production
unit is of a known type and will not be described in more details here.
The first product stream leaves the unit 16 via line 62 and is directed as far as the
first separation unit 18. The first product stream comprises the CO and Hz fraction
stemming from the second stream of synthesis gas and not having reacted in the unit 16.
It also comprises all the products stemming from reactions within the unit 16, and in
particular a large number of hydrocarbons of different natures, as well as water. It further
comprises ;.a. methane CH4, and CZ, C3, C4,.. . , ClO0, chains etc. The hydrocarbons
comprise ia. naphthas, ceraceous materials, waxes (ceraceous materials) and recyclable
products such as for example diesel fuel, and/or kerosene, etc.
In the first separation unit, the first product stream is separated into three streams:
- a water stream with certain organic products dissolved in a small proportion
(alcohols, organic acids);
- a second stream of final products comprising the major part of the condensable
products (for the Fischer-Tropsch process, C4 to CIOO products);
- a first gas stream intended to be recycled, comprising at least CO, Con, Hp and
light hydrocarbons, notably CH4.
The second stream of final product leaves the first separation unit 18 via line 64. It
may be directed towards a post-treatment unit aiming at separating the different
components of this stream from each other. The post-treatment unit may also be a unit
aiming at converting these components into another recyclable product, for example
diesel fuel, etc.
The water stream leaves the first separation unit 18 via line 66. For example it is
directed towards the electrolysis unit 22 or towards the gasification unit 26, optionally after
treatment. The first stream of gas intended to be recycled leaves the unit 18 through line
68 and is directed towards the second separation unit 20.
In this second separation unit, this stream is divided into three different streams:
the purge stream (line 70), the recycling stream towards the unit 14 via line 58 and the
recycling stream to the unit 30 via line 48. The flow rate of each stream is selected so as
to optimize the yield of the process. Normally, the value of the purge flow rate is the
smallest of the three. In an exemplary embodiment, the three flows have exactly the same
composition for all the compounds. However, a separation unit may be provided with
which it is possible to efficiently remove the impurities from the recycling streams towards
the units 14 and 30, and to transfer them into the purge stream.
The purge stream is discharged into the atmosphere, after optional post-treatment.
This post-treatment may consist of burning the light hydrocarbons (energy recycling),
separating certain gas elements for which emission into the atmosphere is regulated etc.
The electrolysis unit 22 gives the possibility of producing a hydrogen stream and
an oxygen stream by electrolysis of the water. The water feeding the electrolysis unit 22
stems from a water source outside the process. In order to limit total water consumption of
the process, a portion of this water supply may also stem from the gas conditioning unit
12, andlor from the first separation unit 18. The hydrogen leaves the electrolysis unit via
line 56. The oxygen leaves the electrolysis unit via line 74, and feeds the gasification unit
or the reforming unit. The electrolysis unit 22 is also supplied with electricity via the
electric line 76. The electric line 76 is typically connected to an electric distribution
network, the network not being dedicated to the electrolysis unit 22 and serving other
consumers outside the unit for producing methanol or hydrocarbons.
In the air separation unit 24, oxygen from air is separated from the other gases,
such as nitrogen. In certain exemplary embodiments, the air separation unit 24 is not
required, the electrolysis unit 22 providing sufficient oxygen for feeding the production unit
10.
The different units of the facility are controlled by a programmed control unit 78 for
applying the production method which will be described below.
The production facility of Fig. 2 will now be described. Only the points through
which this facility differs from that of Fig. 1 will be detailed below. Identical elements all
providing the same function in both facilities will be designated with the same references.
In this facility, the reforming unit 30 is a steam reforming (SR, Steam Reforming)
unit. The reforming unit 30 comprises a combustion sub-unit 80 and a reforming sub-unit
82. The intermediate gas stream after passing into the unit for adjusting the steam level
40, feeds the sub-unit 80. In the sub-unit 80, this gas is indirectly heated, by heat
exchange with a combustion gas. The heated-up intermediate gas stream leaves the
combustion sub-unit 80 through line 84 and is directed to the reforming sub-unit 82. The
combustion gas, in the example of Fig. 2, stems from the second separation unit 20. It
typically includes CO, C02, CH4 and H2 and light hydrocarbons. It is directed from unit 20
as far as an addition unit 88, via line 86. In the addition line 88, an oxidizer, for example
air or oxygen is added to the combustion gas, via line 90. The combustion gas is then
directed via line 92 of unit 88 as far as the combustion sub-unit, in which it burns while
releasing heat. The burnt gases leave the sub-unit 80 through line 94 and form the purge.
They are discharged into the atmosphere, optionally after purification.
In the reforming sub-unit 82, the methane of the heated-up intermediate gas
stream is broken down and converted into CO, C02 and H2 by reforming reactions.
The first stream of synthesis gas, leaving the reforming sub-unit 82, is directed
towards the gas conditioning unit through line 32.
In the production method of the invention, modulation of the electric power demand
of the electrolysis unit 22 is provided, in order to adapt to the electric power available on
the network. Firstly, this gives the possibility of decreasing the electric power of the
electrolysis unit during peak periods, i.e. when the other electric consumers connected to
the network demand significant power. Indeed, the consumed electric power varies during
a same day, with for example a peak at the end of the day. On the other hand, electric
consumption during the night is reduced.
Electric consumption also varies during the year, this consumption being greater
during winter months because of the large number of consumers having electric heating
means, and is more reduced in summer at least in countries where air conditioning is not
in widespread use.
Modulating the electric power of the electrolysis unit is also particularly useful in
the case when the electricity distribution network is supplied with electric sources of
variable power, such as wind turbine or solar sources. The electric power provided by
such sources actually varies depending on the weather conditions.
Thus, in the production method of the invention, the electric power consumed for
producing the hydrogen stream is more significant at certain so-called off-peak periods
and less significant at other so-called peak periods.
Thus, the electrolysis unit 22 produces a smaller hydrogen stream in a peak period
and a larger one in an off-peak period.
In order to compensate for this lack of hydrogen and to therefore obtain the proper
H21C0 ratio at the inlet of the unit 16 (typically of the order of 2.1 for a Fischer-Tropsch
application), the control unit 78 is programmed so as to apply the following strategy.
The operating conditions of the reforming unit 30 may be modified in order to
produce a more or less significant amount of hydrogen. Typically, the H21C0 molar ratio
obtained at the outlet of the unit 30 may vary between 0.6 and 3. Indeed, the operation of
this unit is determined by the temperature, the reaction pressure and the composition of
the incoming streams in the reforming unit 30, notably the H20/C and 02/C ratio
(respectively the total molar flow rate of water entering the unit 30 over the total molar flow
rate of carbon atoms contained in the organic compounds entering the unit 30, and the
total oxygen molar flow rate entering the unit 30 over the total molar flow rate of carbon
atoms contained in the organic compounds entering the unit 30).
By (( total molar flow rate of a species entering the reforming unit 30 )) is meant the
sum of the molar flow rates of the species in all the streams entering the unit 30. In the
example of Fig. 1, the total molar flow rate of carbon atoms contained in the organic
compounds corresponds to the sum of the molar flow rates of carbon atoms in the
different organic compounds (hydrocarbons) in the intermediate stream and in the first
recycled gas stream. The total molar flow rate of water H20 corresponds to the sum of the
water molar flow rates in the intermediate gas stream 44, 49 and in the first recycled gas
stream (48). The total molar flow rate of oxygen essentially corresponds to the oxygen
flow rate brought through line 46, since the molar flow rate of oxygen in the other streams
entering the reforming unit 30 is practically zero.
In practice, when methane CH4 is in majority in the organic compounds entering
the reforming unit 30, it is possible to approximate the ratios above for H20/CH4 and
02/CH4 ratios. H20 and O2 have the same meaning as above. CH4 corresponds to the
total molar flow rate of methane in all the streams entering the reforming unit 30.
Figs. 3 and 10 show calculations obtained by simulation in order to illustrate in a
simplified way the time-dependent change of the different molar fractions of the gases
produced in an ATR or SR type unit. The relevant reactor is isothermal and the operating
pressure 30 bars. The thereby obtained concentrations are at thermodynamic equilibrium
(Gibbs reactor). Further, it was considered that the reactor was perfectly heated to the
desired temperature.
Figs. 3 to 6 show the time-dependent change in the molar fractions on a dry basis
of CH4, Hz, CO and C02 at equilibrium, and the methane conversion level at the outlet of
the reforming unit of Fig. 1, versus the reaction temperature. The temperature is in
abscissas, the molar fractions and the methane conversion level are in ordinates. The
temperature is expressed in degrees C and the other parameters in %.
For a reforming unit of the ATR type which comprises two steps, integrated in a
single reactor:
- a partial combustion or oxidation step, in which oxygen is injected in order to
increase the temperature of the inflowing gases up to the desired reaction conditions,
under the effect of exothermic reactions,
- a second endothermic step, during which the reforming reactions take place in a
fixed catalytic bed.
The temperatures in the catalytic bed typically vary between 800 and l,OOO°C,
under a pressure from 20 to 100 bars. In the upper portion of the catalytic bed, the
temperatures may attain 1,100 to 1 ,400°C. The catalyst is for examples based on nickel
on a spinel support. The temperature in the combustion step is of the order of 2,000°C.
In Figs. 3, 4 and 5, the stream of inflowing gas does not include any C02. On the
other hand, the ratio of total H20 over total CH4 at the inlet of the reactor is 1 in Fig. 3, 2 in
Fig. 4, 5 in Fig. 5. In Fig. 6, the ratio of total H20 over total CH4 in the inflowing gases is 2,
and the ratio of total H20 over total CH4 in the inflowing gases is 1.
Figs. 7 and 8 give the same quantities depending on the temperature as Figs. 3 to
6, for a steam reforming unit such as the one illustrated in Fig. 2. In Figs. 7 and 8, the ratio
of total H20 over total CH4 at the inlet of the reforming unit is equal to 2. Also, the ratio of
total O2 over total CH4 at the inlet of the reforming unit has the value 0.6 in both cases. On
the other hand for Fig. 7, there is no C02 in the gases entering the reforming unit. For
Fig. 8, the ratio of total CH4 over total C02 at the inlet of the reforming unit has the value 1.
Figs. 9 and 10 show the time-dependent change in the respective CO/C02 and
HJCO ratios at equilibrium, i.e. at the outlet of the reactor, versus the reaction
temperature for the six cases corresponding to Figs. 3 to 8.
It clearly emerges that:
a) The methane conversion level is very sensitive to the reaction temperature and
conversion of the methane is promoted by high temperatures,
b) A large (H20/CH4) ratio promotes conversion of methane and therefore
production of synthesis gas (Figs. 3, 4 and 5),
c) The presence of COP and of O2 at the inlet of the reactor causes a reduction of
the (H2/CO) ratio as well as their obtained relative amounts (Figs. 7 and 8),
d) The COP level increases with the increase in the (H20/CH4) ratio at the inlet of
the reactor (Figs. 3, 4 and 5),
e) In Figs. 9 and 10, it may be seen that the presence of O2 at the inlet of the
reformer causes a significant reduction in the H2/C0 ratio.
f) The H2/C0 ratio decreases with the reaction temperature,
g) In the whole of the figures, it may be seen that there exists a compromise
between the conversion of methane and the obtained H2/C0 ratio.
Conversion of the methane is promoted for lower pressures. However, this solution
for varying the H2/C0 ratio is not preferential, since a significant decrease in the operating
pressure would imply addition of a compression unit downstream in order to obtain a
suitable pressure for the unit 16 (typically between 25 and 35 bars for a Fischer-Tropsch
unit).
Further, although the reaction temperature is a parameter which highly influences
the H2/C0 ratio, this parameter may be varied with caution, since the reaction kinetics,
which depends on the activity of the catalyst, and the reaction rates are modified
accordingly.
Thus, in order to compensate for a decrease in the consumed electric power by
the electrolysis unit 22, and therefore a decrease in the amount of hydrogen produced by
this unit 22, the operating temperature of the reforming unit 30 should be reduced and/or
the 02/C ratio should be decreased at the inlet of the reforming unit 30 and/or the H,O/C
ratio should be increased at the inlet of the reforming unit.
In a less preferential alternative, the operating pressure of the reforming unit 30
should be decreased.
In practice, it is not possible to carry out all these modifications simultaneously, or
only in restricted ranges. Indeed, a decrease in the temperature affects the reaction
kinetics and it is possible that equilibrium conditions at the outlet of the reactor are not
attained for too low temperatures. Moreover, the oxygen amount determines the reaction
temperature of the reformer and an increase in the H20/C ratio implies oxygen demand,
since there is a larger proportion of reforming reactions (endothermic reactions). Thus, it is
necessary to determine on a case by case basis, depending on the composition of the
intermediate gas and on the reforming unit type used, which parameters may be acted
upon and to which extent.
Fig. 10 shows that, for the relevant calculation cases in Figs. 6 to 8, an increase in
the ratio of total H20 over total CH, at the inlet of the reforming unit allowed an increase in
the H20/C ratio at the outlet of the reforming unit. The control unit 78 is programmed in
order to vary the total H20/C (or H20/CH4) ratio at the inlet of the reforming unit by at least
one factor comprised between 1.1 and 5, preferably comprised between 1.5 and 3.
However, in certain other exemplary embodiments, for example with other types of
carbonaceous material and other operating conditions of the reforming unit, the total H20
/ total CH4 ratio at the inlet of the reforming unit should be decreased by the control unit 78
in order to increase the H2/C0 ratio at the outlet of the reforming unit.
Depending on the cases, it will be necessary to increase or decrease the 02/CH4
ratio at the inlet of the reforming unit in order to increase the H20/C0 ratio at the outlet of
this same reforming unit.
In the example shown below in [Table I], the only parameter for controlling the
H2lCO ratio at the outlet of the unit 30 is the H20/C ratio. The value of the 02/C ratio is
adjusted so as to have constant reforming temperature.
Table 1 shows the performances of the methods of Fig. 1 and of Fig. 2 during a
peak period and during an off-peak period when the unit 16 is a Fischer-Tropsch reactor.
In the four calculation cases, the HdCO ratio at the inlet of the unit 16 is 2.1. In the
off-peak period, the consumed electric power by the electrolysis unit is significant (of the
order of 150 MW). In a peak period, the electric power consumed by the electrolysis unit is
reduced to about 80 MW, but the H20/CH4 ratio at the inlet of the reforming unit is
increased. This ratio has the value 1.15 in an off-peak period and the value 5 in a peak
period. A decrease in the net power required by the electrolyzer is seen to be of the order
of 45%. However, inevitably the FT products decrease by the order of 17%. Indeed, the
carbon yield decreases because a portion of the CO is converted into C02 and H2 in order
to make up for the lack of electrolytic hydrogen. Also, the discharged amount of C02 of the
system increases. This C02 may be stored so as to be used in another type of recycling
operation or for sequestration.
The composition of the intermediate gas stemming from the gasification unit is
indicated in Table 2, as well as the mass flow rate of the intermediate gas stream, the
temperature and the pressure at the outlet of the gasification unit.
The table shows that the H,ICO ratio at the outlet of the reforming unit may vary
from 0.7 in off-peak periods to 1.2 in peak periods, for the relevant calculation case. The
product flow rate at the outlet of the Fischer-Tropsch unit 16 is of the order of 3.4 kgls in
off-peak periods and 2.8 in peak periods.
The method of the invention and the corresponding production facility have
multiple examples.
It gives the possibility of adapting the power required by the electrolyzer to the
availabilities of the electric distribution network, which contributes to stabilization of the
operation of the distribution network at least locally. Moreover, this allows a reduction in
the electric consumption of the electrolyzer at the moment when the prices of electricity
are the highest, in order to increase electric consumption at the moment when the
electricity costs are lower. The yield of the facility is thereby increased. The possibility of
modulating the consumed electric power by the electrolysis unit allows the latter to
operate with electricity not stemming from a local electric distribution network but directly
from a renewable electric source, for example wind turbines.
It is possible to adapt the operation of a facility without resorting to massive
storage of hydrogen or of electric power.
The electric power consumed by the electrolyzer may be strongly reduced, the
amount of produced hydrocarbon being moderately reduced. The amount of hydrocarbon
produced per consumed MW is clearly greater in a peak period than in an off-peak period,
as shown by Table 1. In the examples of this table, a reduction by more than 40% in the
electric power consumed by the electrolysis unit causes a reduction by at least 20% of the
produced amount of hydrocarbons.
As compared with these results, if the flexibility of the method towards the supply
flow rate for the Fischer-Tropsch reactor is also taken into account, it is possible to reach
a reduction by more than 50% of the consumed electric power per electrolysis unit, for a
reduction by less than 30% of the amount of produced hydrocarbons.
The method and the production facility may have multiple alternatives.
The production unit 16 may not operate according to the Fischer-Tropsch process
but be a unit for producing methanol. Methanol may be the final product or be subject to a
post-treatment in order to be converted into a hydrocarbon, for example according to the
MTG (Methanol to Gasoline) process.
The air separation unit 24 is not required in every case, the electrolysis unit being
in certain cases sufficient for providing the required amount of oxygen to the gasification
unit and to the reforming unit.
Table 1: Comparison of the performances of the FT method with an ATR and SR unit
The ATR and SR units operate at 950°C and 28.5 bars.
Study variables
(H21CO) (mol) Line 60
(H20/CH4) (mol) Reformer
inlet Line 44
ATR or SR (Unit 30)
(H2/CO) (mot) reformer
outlet Line 32
O2 reformer supply (kgls)
Line 46
Combustion
O2 reformer (kgls) Line 90
Electrolyzer (Unit 22)
Hz (kgls) Line 56
0, (kgls) Line 74
MW consumed Line 76
FT process (Unit 16)
Conversion (%)
Synthesis gas (CO+H2)
supply (kgls) Line 50
FT process supply (kgls)
Line 50
FT reactor supply (kgls)
Line 60
Products (kgls) Line 64
Purge ratio (%)
Gas purge (kgls) Line
70194
Discharged C02 (kgls)
Line 52
(kg of products)/(MWh of
electrolyzer)
Fig. 2 (SR)
Off-pea k
period
2.1
1.15
0.69
---
3.697
0.880
6.987
152
70
9.1 1
12.43
32.33
3.402
19
4.517
1.945
80.5
Fig. 1 (ATR)
Off-peak
period
2.1
1.15
0.73
3.392
---
0.846
6.714
146
70
9.00
12.37
32.40
3.354
5
1.199
6.859
82.6
Fig. 2 (SR)
Peak period
2.1
5
1.20
---
2.522
0.476
3.778
82
70
7.91
11.39
30.52
2.847
17
3.693
4.757
125.0
Fig. 1 (ATR)
Peak period
2.1
5
1.19
2.478
---
0.4682
3.716
8 1
70
7.73
11.29
30.63
2.781
5
1.180
8.679
123.6
Table 2: Drv basis composition of the intermediate qas at the outlet of the qasification unit
CO
Con
H 2
CH4
Other organic compounds
H2/CO
Pressure
Temperature
Mass flow rate
Ethane
Ethylene
Methane
CO
Con
H2
Hz0
N2
Ar
Ammonia
H2S
BTX - Benzene
Tars-Naphthalene
H2/C0
HPOICH~
19.2
45.0
19.0
13.2
3.5
1 .OO
2 9
950
20.4
0.08
1.53
8.17
11.86
27.92
11.79
37.69
0.06
0.06
0.29
0.01
0.26
0.27
1 .OO
4.6
% mol
% mol
% mol
% mol
% rnol
mol/rnol
bar
"C
kg/s
% v/v
% v/v
% v/v
% v/v
% v/v
% v/v
% v/v
% v/v
% vlv
% v/v
% v/v
% v/v
% v/v
mol/mol
mol/mol

IWe Claim:
1. A method for producing methanol and/or hydrocarbons from at least one
carbonaceous material, the method comprising the following steps:
- producing a synthesis gas from the carbonaceous materials, according to a
process comprising at least one operation for reforming an intermediate gas stream from
the carbonaceous material, the stream of synthesis gas comprising at least hydrogen and
carbon monoxide, the synthesis gas having a first hydrogenlcarbon monoxide molar ratio
under first operating conditions for performing the reforming;
- producing a hydrogen stream from a hydrogenated raw material and from a first
consumed electric power, the hydrogen stream having a first molar flow rate for said first
consumed electric power;
- producing methanol and/or hydrocarbons from the synthesis gas and from the
hydrogen stream;
- decreasing the consumed electric power for producing the hydrogen stream,
down to a second electric power below the first electric power, the hydrogen stream
having a second molar flow rate below the first molar flow rate for the second consumed
electric power, and setting second operating conditions different from the first for the
reforming operation in order to compensate for the decrease of the molar flow rate of the
hydrogen stream, the synthesis gas having a second hydrogenlcarbon monoxide molar
ratio greater than the first under the second operating conditions.
2. The method according to claim 1, characterized in that, under the first operating
conditions, the reforming operation is carried out at a first temperature; under the second
operating conditions, the reforming operation is carried out at a temperature below the first
temperature.
3. The method according to claim 1 or 2, characterized in that, under the first
operating conditions, the reforming operation is carried out at a first pressure; under the
second operating conditions, the reforming operation is carried out at a second pressure
below the first pressure.
4. The method according to any of the preceding claims, characterized in that the
reforming operation is carried out in a reforming unit receiving at the inlet a plurality of
inflows containing organic molecules, including the intermediate stream, the reforming unit
receiving from the different inflows, all in all, a total molar flow rate of carbon atoms
contained in the organic molecules and a total water H20 molar ratio, the reforming
operation passing from the first operating conditions to the second operating conditions by
modifying a ratio of the total water H20 molar flow rate over the total molar flow rate of
carbon atoms contained in the organic molecules.
5. The method according to claim 4, characterized in that the ratio of the total
water H20 molar flow rate over the total molar flow rate of carbon atoms contained in the
organic molecules is equal to a first value under the first operating conditions, and is equal
to a second value greater than the first under the second operating conditions.
6. The method according to claim 5, characterized in that the second value is
comprised between 1 .I and 5 times the first value, preferably between 1.5 and 3 times the
first value.
7. The method according to any of the preceding claims, characterized in that the
reforming operation is carried out in a reforming unit receiving at the inlet a plurality of
inflows, including the intermediate stream, the reforming unit receiving from the different
inflows, all in all, a total molar flow rate of carbon atoms contained in the organic
molecules and a total oxygen O2 molar flow rate, the reforming operation passing from the
first operating conditions to the second operating conditions by modifying a ratio of the
total molar flow rate of oxygen over the total molar flow rate of carbon atoms contained in
the organic molecules.
8. The method according to any of the preceding claims, characterized in that the
hydrogen stream is produced from electricity provided by an electric distribution network
serving other consumers.
9. The method according to any of the preceding claims, characterized in that the
intermediate stream is obtained by gasification of the carbonaceous material.
10. A facility for producing methanol andlor hydrocarbons from at least one
carbonaceous material, the facility comprising:
- a unit (10) for producing synthesis gas from the carbonaceous material,
comprising at least one unit (30) for reforming an intermediate gas stream from the
carbonaceous mater, the stream from synthesis gas comprising at least hydrogen and
carbon monoxide, the synthesis gas having a first hydrogenlcarbon monoxide molar ratio
under the first operating conditions for the reforming unit (30);
- a unit (22) for producing a hydrogen stream from a hydrogenated raw material
and from a first consumed electric power, the hydrogen stream having a first molar flow
rate for said first consumed electric power;
- a unit (16) for producing methanol andlor hydrocarbons from the synthesis gas
and from the hydrogen stream;
- a programmed control unit (78) for decreasing the consumed electric power for
producing the hydrogen stream, down to a second electric power below the first electric
power, the hydrogen stream having a second molar flow rate below the first molar flow
rate for the second consumed electric power, and for setting the reforming unit (30) under
second operating conditions different from the first for compensating for the decrease in
the molar flow rate of the hydrogen stream, the synthesis gas having a second
hydrogenlcarbon monoxide molar ratio greater than the first under the second operating
conditions.
Dated 14 August 2013
KONPAL RAE
INIPA-1228
Agent for the Applicant
To,
The Controller of Patents
The Patent Office at New Delhi