Patent Publication Number: US-2022212924-A1

Title: Production of syngas using recycled co2 via combined dry and steam reforming of methane

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority on U.S. Provisional Application No. 62/845,574, now pending, filed on May 9, 2019, which is herein incorporated by reference. 
    
    
     FIELD 
     The present subject matter relates to the production of methanol and, more particularly, to the CO 2  resulting therefrom. 
     BACKGROUND 
     In a conventional methanol plant, natural gas is used to produce synthesis gas or syngas, which in turn is used to produce methanol. The syngas production process is endothermic and requires large amounts of heat that is produced by burning more natural gas. This results in a process that generates large amounts of greenhouse gas emissions, mainly carbon dioxide (CO 2 ), from the combustion of natural gas and as a by-product from the production of syngas. 
     Carbon dioxide is a greenhouse gas that has a detrimental effect on human and all forms of life on the planet, causing global warming. 
     It would therefore be desirable to have a process that reduces the amount of carbon dioxide released to the atmosphere from the production of methanol. 
     SUMMARY 
     It would thus be desirable to provide a process that uses carbon dioxide, for instance for the production of methanol. 
     The embodiments described herein provide in one aspect a process for using CO 2 , comprising recuperating CO 2 ; and transforming the CO 2  into a synthetic gas by means of plasma. 
     For instance, the CO 2  used to produce the synthetic gas includes recycled CO 2  emissions from a plant. 
     For instance, the CO 2  emissions are obtained from a methanol producing plant. 
     For instance, the CO 2  emissions used to produce the synthetic gas are recycled back into the methanol production process. 
     For instance, the CO 2  includes emitted CO 2  from fossil-fuel heating burners used as carbon source to produce the synthetic gas. 
     For instance, the synthetic gas is produced via a combined plasma methane-steam reforming. 
     For instance, the synthetic gas is produced using a combination of dry and steam reforming of methane via the plasma, thereby producing a rich synthetic gas stream with a H 2 :CO ratio of 2. 
     For instance, the syngas is used for the production of methanol. 
     For instance, CO 2  emissions from a urea plant are captured and recycled into the synthetic gas for the production of methanol. 
     For instance, the CO 2 , methane and steam react to produce the synthetic gas, via the following reaction CO 2 +3CH 4 +2H 2 O=4CO+8H 2 . 
     For instance, a plasma reactor is provided for the reaction. 
     For instance, for the reaction, a reaction temperature of between approximately 1100-3000° C. is used. 
     For instance, the reaction temperature is between approximately 1100-2100° C. 
     For instance, the reaction temperature is between approximately 1200-1800° C. 
     For instance, the reaction temperature is approximately 1600° C. 
     For instance, part of the heat of the synthetic gas is used to heat water, which water being adapted to be at least part of the steam used to produce the synthetic gas. 
     For instance, a heat exchanger is provided for causing the synthetic gas to heat the water. 
     For instance, the synthetic gas, downstream of the synthetic gas having heated the water, is used to produce methanol. 
     Also, the embodiment described herein provide in another aspect a 
     Furthermore, the embodiment described herein provide in another aspect a process whereby CO 2  emissions from a plant are recycled by producing synthetic gas. 
     Furthermore, the embodiment described herein provide in another aspect a process whereby synthetic gas is produced via a combined plasma methane-steam reforming. 
     Furthermore, the embodiment described herein provide in another aspect a process for transformation of CO 2  to synthetic gas by means of plasma. 
     Furthermore, the embodiment described herein provide in another aspect a process that uses emitted CO 2  from fossil-fuel heating burners as a carbon source to produce synthetic gas. 
     Furthermore, the embodiment described herein provide in another aspect a process that combines dry and steam reforming of methane via thermal plasma to produce rich synthetic gas stream with a H 2 :CO ratio of 2. 
     Furthermore, the embodiment described herein provide in another aspect a process whereby CO 2  emissions from a methanol producing plant are recycled back into the methanol production process. 
     Furthermore, the embodiment described herein provide in another aspect a process that combines dry and steam reforming of methane into syngas with a H 2 :CO ratio of 2, required for the production of methanol. 
     Furthermore, the embodiment described herein provide in another aspect a process for methanol production that reduces the carbon footprint by 355 000 t CO 2  eq/yr for a 3 000 t/day methanol production plant. 
     Furthermore, the embodiment described herein provide in another aspect a methanol production plant integrated with a urea production plant, wherein CO 2  emissions from the urea plant are captured and recycled into syngas for the production of methanol. 
     Furthermore, the embodiment described herein provide in another aspect a process for producing synthetic gas using CO 2 , comprising: a) providing CO 2 , methane and steam; and b) submitting the CO 2 , methane and steam to high temperatures so that the CO 2 , methane and steam react to produce a synthetic gas. 
     For instance, in step b) the high temperatures are provided by plasma. 
     For instance, a plasma reactor is provided. 
     For instance, the CO 2  used to produce the synthetic gas includes recycled CO 2  emissions from a plant. 
     For instance, the CO 2  emissions are obtained from a production of methanol. 
     For instance, the synthetic gas is used in a methanol production process. 
     For instance, the synthetic gas is produced using a combination of dry and steam reforming of methane via the plasma, thereby producing a rich synthetic gas stream with a H 2 :CO ratio of 2. 
     For instance, CO 2  emissions from a urea plant are captured and recycled into the synthetic gas for the production of methanol. 
     For instance, the CO 2 , methane and steam react as per the following reaction CO 2 +3CH 4 +2H 2 O=4CO+8H 2 . 
     For instance, a plasma reactor is provided for the reaction. 
     For instance, for the reaction, a reaction temperature of between approximately 1100-3000° C. is used. 
     For instance, the reaction temperature is between approximately 1100-2100° C. 
     For instance, the reaction temperature is between approximately 1200-1800° C. 
     For instance, the reaction temperature is approximately 1600° C. 
     For instance, part of the heat of the synthetic gas is used to heat water, which water being adapted to be at least part of the steam used to produce the synthetic gas. 
     For instance, a heat exchanger is provided for causing the synthetic gas to heat the water. 
     For instance, the synthetic gas, downstream of the synthetic gas having heated the water, is used to produce methanol. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the embodiments described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, which show at least one exemplary embodiment, and in which: 
         FIG. 1  is a graph showing a reaction system of CO 2 +3CH 4 +2H 2 Oat equilibrium in accordance with an exemplary embodiment; and 
         FIG. 2  is a schematic block diagram of an integrated process for valorization of CO 2  from a Methanol-Urea plant in accordance with an exemplary embodiment. 
     
    
    
     DESCRIPTION OF VARIOUS EMBODIMENTS 
     Generally, the process of the present subject matter is adapted to recycle CO 2  from a carbon capture system downstream of the methanol production plant into more syngas and methanol, thereby reducing the amount of CO 2  released to the atmosphere, and thus favourably reducing the greenhouse effect and global warming. 
     The proposed solution is based on using thermal plasma technology to valorize the CO 2  into syngas that is the main feed stream for methanol production. In this process, CO 2  is converted to syngas using a combination of dry and steam plasma reforming at high temperature. In order to be able to recycle back the CO 2  as the carbon source into the methanol or methanol-urea plant, the CO 2  should be converted to a usable product, that is syngas which consists of H 2  and CO. Dry reforming of CO 2  through reaction with methane will yield syngas with a H 2 /CO ratio of 1 according to the following reaction: 
       CO 2 +CH 4 =2CO+2H 2 (H 2 /CO=1) 
     This conversion of CO 2  to syngas via the above reaction yields a syngas with a H 2 /CO ratio of one (1). However, to be able to use this syngas in the methanol plant, a ratio of H 2 /CO=2 is required according to the following methanol synthesis reaction: 
       CO+2H 2 ═CH 3 OH
 
     Therefore, to make it possible to reuse the excess CO 2  from the purification plant in the form of syngas, the following reaction is proposed: 
       CO 2 +3CH 4 +2H 2 O=4CO+8H 2 (H 2 /CO=2) 
     The feasibility of the above-mentioned plasma reaction was validated using HSC software that uses Gibbs-Free energy minimization method to predict the reaction system at various temperatures for a gas mixture of CO 2 , CH 4 , and H 2 O. The ratio of CH 4  over H 2 O was varied while CO 2  was kept constant until a H 2 /CO ratio of 2 was produced in the reaction system, at a reaction temperature of 1600° C., which is readily archivable using plasma technology. The results of HSC calculation for a gas mixture of CO 2 +3CH 4 +2H 2 O is shown in  FIG. 1 , highlighting the main products. 
     As can be seen in  FIG. 1 , the production rate of H 2  and CO maximizes at a temperature of 1600° C., and above this temperature, H 2  starts to decompose into atomic hydrogen (H) while CO is stable over a wider temperature range. For a high syngas production yield, therefore a reaction temperature of, for instance, approximately 1600° C. is recommended. 
     The main source of H 2 O in the reaction can be steam plasma that contains a very high enthalpy and it is very reactive, which is enough for the proposed reaction to proceed at 1600° C. at a very high yield. In fact, the heat and mass (H&amp;M) balance calculation was performed to study the specific energy required for the reaction regarding the methanol or methanol-urea plant CO 2  surplus to proceed at 1600° C. The results of H&amp;M balance calculation are summarized in the following Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Heat and Mass balance over proposed combined 
               
               
                 plasma dry-steam reforming of CO 2  at 1600° C. 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 Temper. 
                 Pressure 
                 Amount 
                 Amount 
                 Amount 
                 Heat Content 
                 Total H 
               
               
                   
                 ° C. 
                 bar 
                 kmol 
                 kg 
                 Nm 3   
                 kWh 
                 kWh 
               
               
                   
               
               
                 INPUT SPECIES 
               
               
                 Formula 
               
               
                 CH4(g) 
                 25 
                   
                 3000 
                 48127 
                 67241 
                 0.000 
                 −62167 
               
               
                 CO2(g) 
                 25 
                   
                 1000 
                 44010 
                 22414 
                 0.004 
                 −109307 
               
               
                 H2O 
                 25 
                   
                 2000 
                 36031 
                 39 
                 0.005 
                 −158794 
               
               
                 OUTPUT SPECIES 
               
               
                 Formula 
               
               
                 CO(g) 
                 1600 
                   
                 4000 
                 112040 
                 89654 
                 57939 
                 −64885 
               
               
                 H2(g) 
                 1600 
                   
                 8000 
                 16127 
                 179309 
                 108062 
                 108062 
               
               
                   
               
               
                   
                   
                   
                 kmol 
                 kg 
                 Nm 3   
                 kWh 
                 kWh 
               
               
                   
               
               
                 BALANCE: 
                   
                   
                 6000 
                 0 
                 179270 
                 166001 
                 373446 
               
               
                   
               
            
           
         
       
     
     Assuming a theoretical 100% conversion yield of CO 2  to syngas, at a feed rate of ˜44000 kg/hr CO 2 , specific energy requirement of the system is ˜373 MWhr, which gives a specific energy requirement of 2.9 kWhr/kg of syngas (H 2 /CO=2). Since thermal plasma is energized by only using electricity and knowing the abundance of hydroelectric power in the Province of Quebec, Canada, the process can be considered green with near zero carbon footprint. 
     Since the methanol process requires syngas at a lower temperature, the excess heat that is carried by the syngas leaving the plasma reactor can be recovered. For instance, the differential energy content of the syngas stream as shown in above Table 1 with regards to a delta T of 1100° C. is ˜120 MWh, which would be enough to produce ˜160 000 kg of atmospheric pressure steam at 145° C. 
     In addition, there are a few important advantages of the present plasma process, as follows:
         green process;   compact, as only the reactants are directly brought to the reaction temperature;   no sensitivity to the quality of CO 2  stream, as no catalyst is used; and   very high conversion yield of CO 2  to syngas, thereby resulting in a pure syngas stream.       

     A process block diagram of the present plasma-based solution, integrated with a Methanol-Urea plant, is depicted in  FIG. 2 . The excess CO 2  is valorized into syngas that is then used in the methanol plant to produce methanol with 25% of its carbon by CO 2  recovery. 
     In summary, water is introduced at  10 , which water is heater by a heat exchanger  12  and is then fed at  14  to a plasma torch  16  that is powered by electricity  18 . The steam from the plasma torch  16  is fed to a plasma reactor  20 , which is also fed with the aforementioned recovered CO 2  at  22  and with methane CH 4  at  24 . 
     The syngas  26  produced by the plasma reactor  20  include excess heat, heat that the syngas does not require for its use with natural gas to produce methanol. Therefore, this excess heat in the syngas  26  is recovered in the heat exchanger  12  for heating the input water  10 . 
     The econo-environmental impact of the present process is summarized in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Econo-Environmental impact of the present plasma-based 
               
               
                 solution 
               
            
           
           
               
               
               
               
               
            
               
                 Specific  
                   
                   
                 direct cost  
                   
               
               
                 energy 
                 GHGs 
                 Carbon 
                 of syngas 
                 Physical  
               
               
                 requirement 
                 reduction 
                 foot print 
                 production 1   
                 Footprint 
               
               
                   
               
               
                 ≤2.9 kWh/kg 
                 355 000 t 
                 −25% in  
                   ~ 0.3 $/kg 
                   ~ 1/10 of conven- 
               
               
                 syngas 
                 CO 2  eq/yr 
                 methanol 
                   
                 tional process, 
               
               
                   
                   
                 produced 
                   
                 lower CAPEX 
               
               
                   
               
               
                   1 Excluding Natural gas price, and 10 cents per kWh 
               
            
           
         
       
     
     While the above description provides examples of the embodiments, it will be appreciated that some features and/or functions of the described embodiments are susceptible to modification without departing from the spirit and principles of operation of the described embodiments. Accordingly, what has been described above has been intended to be illustrative of the embodiments and non-limiting, and it will be understood by persons skilled in the art that other variants and modifications may be made without departing from the scope of the embodiments as defined in the claims appended hereto.