CA2741257C - Method for the "co shift" conversion of a synthesis gas in a fast fluidised bed - Google Patents

Abstract

The invention consists of a conversion facility of CO shift of a synthesis gas by means of catalyst particles introduced into a fluidized bed reactor receiving water vapor and input into a synthetic gas wind box. according to the invention, the installation comprises at least two fast fluidized bed reactor loops (1, 2, 3) connected in series by a gas circuit, each loop comprising a reactor (1A, 2A, 3A) associated with a device for separating gases and solids (1C, 2C, 3C) and a solid return line (1D, 2D, 3D) in said reactor, and in which circulates said particles of catalyst, the reactor (1A) of the first loop receiving the raw synthesis gas at the inlet and the reactor (2A) of the second loop receiving the separated gas at the outlet of the separation device (1C) of the first loop, and the reactors (1A, 2A, 3A) of these two loops operate at different temperatures.

Description

WO 2010/052397 PCT [FR2009 / 051870 PROCESS FOR CONVERTING "CO SHIFT" OF A FLUIDIZED BED SYNTHESIS GAS
FAST

The invention relates to a device for converting CO shift of a gas synthesis in a fast fluidized bed.
CO shift here means the reaction between carbon monoxide and the water vapor: CO + H20 - H2 + C02. This reaction is called in French displaced conversion of carbon monoxide.
The production of synthetic fuels based on fossil fuels and biomass, or even urban and industrial waste, is being development, given the imbalance between demand and limited supply especially due to the lack of new oil deposits, for next few years, while reserves of natural gas and coals lignite are more important, and that biomass and waste are a deposit permanent and harmless from the point of view of carbon dioxide. This is by example of producing gasolines, methanol, ethanol, dimethyl ether, automotive fuels alone or in combination or to make substitutes at diesel fuel.
This technique of producing synthetic fuels is based on the following technologies, which are industrially known, particularly in South Africa, but expensive:
- Gasification under pressure of the fuel, generally carried out at oxygen and steam, using fixed beds, trained beds, or fluidized beds - steam reforming of natural gas in tubular furnaces filled with catalysts, the CO shift making it possible to adjust the CO / H2 ratio to the desired synthesis, - the capture of sulfur species H2S and COS from the fuel, the capture of CO2 in the synthesis gas, - Synthetic fuel synthesis loop.
The cost reduction of these technologies and their integration for this application is an absolute priority. It implies a simplification radical

2 technologies and ideally should allow to respond to the sizes of the very great industrial units but also medium-sized or small units cut forest and agricultural biomass.
It is known from patent document WO 97/31858 to produce CO
shift out of a gasification system by means of a bed reactor fluidized dense catalyst bed receiving as input synthesis gas and the steam of water. The catalyst is essentially alumina. This CO shift is realized in one step and therefore at a single temperature between about 530 and 980 C.
Such an arrangement makes it possible to convert only a limited portion of the carbon monoxide, of the order of 80%. This limited yield in conversion of carbon monoxide to hydrogen leads to losses of carbon monoxide and therefore carbon dioxide when released to the atmosphere, in a context of combustion.
Moreover, the CO shift steam consumption is very over-stoichiometric in relation to the need for the reaction, which penalizes this conversion from the energy point of view.
Finally methane from gasification passes through this conversion and must be evacuated at the level of the fuel synthesis loop synthetic.
The invention solves these technical problems and to do this, it proposes a CO shift conversion facility of a synthesis gas using of catalyst particles introduced into a receiving fluidized bed reactor of the water vapor and as input to a synthetic gas wind box, characterized in that it comprises at least two fluidized bed reactor loops connected in series by a gas circuit, each loop comprising a reactor associated with a separation device for gases and solids and a return line of solids in said reactor, and in which circulates said particles of catalyst, the reactor of the first loop receiving the raw synthesis gas in inlet and the reactor the second loop receiving the gas separated out of

3 separation device of the first loop, and in that the reactors of these two loops operate at different temperatures.
The principle of the invention is to carry out the CO shift reaction in fast fluidized bed loop with circulation of the catalyst under pressure, allowing for a simple way to control the exothermicity of each step of conversion.
The invention makes it possible to avoid the division of the gaseous streams to be treated into CO shift, knowing that each gas stream in the existing technique must to be treated at different temperature stages requiring each of the specific heat exchangers, which leads to complexity and cost important.
Due to the significant turbulence prevailing in each reactor, obtaining the conversion with a quasi stoichiometry of injected vapor is made possible.
The invention thus allows a gain in yield, a reduction in size of the reactor, steam minimization, simplification and extrapolation to all unit sizes.
The catalyst is not fixed but circulates in a loop and ensures the function of coolant.
The exothermicity of the CO shift reaction is now transferred by gas and solid exchanges, the solid being the catalyst.
The invention is described in more detail with the aid of figures representing the installation according to a preferred embodiment of the invention.
FIG. 1 is a diagrammatic view in vertical section of an installation according to the invention.
Figure 2 is a vertical sectional detail view of this installation.
According to this preferred embodiment, the CO conversion plant shift of a synthesis gas comprises three fluidized bed reactor loops fast 1, 2, 3 connected in series by a synthesis gas circuit, each loop comprising a reactor 1A, 2A, 2B in which particles are introduced of

4 catalytic converter and receiving at the entry in a wind box 1B, 2B, 3B of the gas of synthesis as a fluidizing gas and at the bottom of the receiver, above of the fluidization grid forming the ceiling of the wind box, the water vapour.
This reactor is associated with a device for separating gases and solids, of cyclone type 1C, 2C, 3C, and a return line 1D, 2D, 3D solids in the bottom of the reactor. A particulate catalyst therefore circulates in each loop.
The reactor 1A of the first loop receives the raw synthesis gas, at a temperature of about 800 to 1000 C and a pressure of between 5 and 50 bars, entering into its wind box 1B, the reactor 2A of the second loop receives in its wind box 2B the separated gas output of the device of separation 1C of the first loop and the reactor 3A of the third receives in its box wind 3B the gas separated at the outlet of the separation device 2C of the second loop. Final synthesis gas free of carbon monoxide is recovered at the gas outlet of the separation device 3C of the third loop.
The reactors of these three loops operate at temperatures different. Preferably, the reactor 1A of the first loop operates at a temperature between about 400 and 550 C, preferably between 450 and approximately 500 ° C., the reactor 2A of the second loop operates at a between about 280 and 400, preferably between 350 and approximately 400 C and the reactor 3A of the third loop operates at a temperature between about 180 and 300 C, preferably between 250 and about 280 C.
In the first and second loops 1, 2, the catalyst used is preferably Fe203 iron oxide activated with Cr203 chromium oxide. In the third loop 3, the catalyst is preferably copper oxide and zinc oxide supported by alumina. This catalyst is in particles of average diameter between 20 and 80 microns.
The solids circulating in each loop can be of composition different optimized for resistance to sulfur pollutants, that is the COS sulphide carbonyl and H2S hydrogen sulphide, depending on the operating temperatures above, the solid circuits of each loop are preferably independent.
Each reactor loop has a control heat exchanger of the temperature on its circuit solids. This exchanger 1E, 2E, 3E can to be

5 disposed on the return pipe of the solids ID, 2D, 3D and / or this exchanger 1F, 2F, 3F is disposed in the reactor 1A, 2A, 2B. These exchangers ensure temperature control of the reactors and transfers the exothermicity of reactions CO shift.
The installation has a single circuit of water and water vapor 4 which feeds each exchanger 1E, 2E, 3E, 1F, 2F, 3F. The water vapor produced by this circuit 4 is partially used as a reagent in the CO reaction shift and the surplus is exported on a steam network. The exchanger 3E, 3F of the third loop at lower temperature is for example an economizer, while an evaporator and a low temperature superheater are for example installed in the other loops 1, 2.
The second reactor 2A and the third reactor 3A have a 2G, 3G high speed cyclone filtration device built-in upstream of their windbox, in order to minimize the pollution of the catalysts by the loss of fine particles through cyclones 1C, 2C of the first and second loop. A
such arrangement is shown in FIG.
The wind box 2B, 3B equipped in the upper part of fluidization nozzles 5 supplying the lower part of the reactor 2A, 3A is open on its lower part at plunger tube 7. This lower part of the reactor also comprises 6 steam injection rods, in the immediate vicinity of the return of the solids fe so as to dissipate the exothermicity of the reaction in the flow of solid recycled ..
The dip tube 7 forms the output of the high speed cyclone gas 2G, 3G in which between the gas separated at the outlet of the separation device 1C, 2C of cyclone type of the previous loop, by means of a lateral pipe 8. The fine particles are removed in the lower part of the cyclone at high speed

6 3G and are extracted by an airlock 9 and then stored in a tank 10 before their recycling.

Claims (11)

1. Installation for conversion of "CO shift" of a synthesis gas by means of particles of catalyst introduced into a fluidized bed reactor receiving steam water and synthesis gas inlet and characterized in that it comprises at least two loops of fast fluidized bed reactor (1, 2, 3) connected in series by a circuit of gas, each loop comprising a reactor (1A, 2A, 3A) associated with a separation device gas and solids (1C, 2C, 3C) and a solid return line (1D, 2D, 3D) in said reactor, wherein said catalyst particles circulates, the reactor (1A) of the first loop receiving the raw synthesis gas input and the reactor (2A) of the second loop receiving the separated gas at the outlet of the separation device (1C) of the first loop, and in that the reactors (1A, 2A, 3A) of these two loops operate at temperatures different. 2. Installation according to claim 1, characterized in that it comprises three so-called loops fluidized bed reactor (1, 2, 3) connected in series by said gas, the reactor (3A) of the third receiving the separated gas at the outlet of the separation device (2C) of the second loop, and in that the reactors (1A, 2A, 3A) of these three loops operate at different temperatures. 3. Installation according to claim 1 or 2, characterized in that each said loop of reactor (1, 2, 3) has a catalyst particle circuit independent. 4. Installation according to any one of claims 1 to 3, characterized in that each reactor loop (1, 2, 3) comprises a control heat exchanger of the temperature on its circuit solids. 5. Installation according to claim 4, characterized in that said exchanger (1E, 2E, 3E) is disposed on said solid return line (1D, 2D, 3D). 6. Installation according to claim 4 or 5, characterized in that said exchanger (1F, 2F, 3F) is disposed in said reactor (1A, 2A, 3A). 7. Installation according to claims 3 and 6, characterized in that a single circuit of water and water vapor feeds each said exchanger (1E, 2E, 3E, 1F, 2F, 3F). 8. Installation according to any one of claims 1 to 7, characterized in that each reactor comprises a wind box (1B, 2B, 3B) into which the gas of synthesis as fluidization gas and supply rods (6) of water vapor in the lower part of the reactor. 9. Installation according to any one of claims 2 to 8, characterized in that said second reactor (2A) and optionally said third reactor (3A) have a high-speed (2G, 3G) cyclone filtration device downstream of their wind box (2B, 3B). 10.Installation according to claim 9, characterized in that said box wind has in lower part an open dip tube (7) forming the cyclone gas outlet at high speed (2G, 3G). 11. Installation according to any one of claims 2 to 10, characterized in that the reactor (1A) of said first loop operates at a temperature of enter about 400 and about 550 ° C, the reactor (2A) of said second loop works at a temperature between about 280 and about 400 ° C and the reactor (3A) of said third loop operates at a temperature between about 180 and about 280 ° C.