Description: FORM 2
THE PATENTS ACT 39 OF 1970
&
THE PATENT RULES 2003
COMPLETE SPECIFICATION
(SEE SECTIONS 10 & RULE 13)
1. TITLE OF THE INVENTION

“A NOVEL PROCESS TO CONVERT A CARBONACEOUS FEEDSTOCK INTO AMMONIA THROUGH AUTO THERMAL CHEMICAL LOOPING GASIFICATION METHOD”

2. APPLICANTS (S)
NAME NATIONALITY ADDRESS

BHARAT HEAVY ELECTRICALS LIMITED
INDIAN
With one of its Regional Offices at REGIONAL OPERATIONS DIVISION (ROD), PLOT NO: 9/1, DJ Block 3rd Floor, Karunamoyee, Salt Lake, Kolkata-700091, West Bengal, India; having its Registered Office at BHEL HOUSE, SIRI FORT, NEW DELHI - 110049, India, an Indian Company

3. PREAMBLE TO THE DESCRIPTION
COMPLETE SPECIFICATION

The following specification particularly describes the invention and the manner in which it is to be performed

FIELD OF INVENTION
[0001] The invention falls under category of ‘conversion of syngas using an auto thermal chemical looping gasification method and allied areas of applications of syngas’. More specifically, this invention is related to “Conversion of a carbonaceous feedstock into ammonia through auto thermal chemical looping gasification method”. The invention covers overall process development of converting solid feedstock through chemical looping method to syngas and subsequent conversion of syngas to ammonia.

BACKGROUND OF INVENTION

[0002] The conversion of carbonaceous feedstock, such as biomass, coal, and petcoke, into syngas comprising CO, H2, CO2, and CH4 is known as gasification. The resulting syngas finds diverse applications, including power generation using Integrated Gasification Combined Cycle (IGCC) technology, liquid fuel synthesis via the Fischer-Tropsch process, and hydrogen production through the water gas shift reaction. The ratio of H2 to CO in the syngas varies depending on the intended application.
[0003] During the gasification process, carbonaceous feedstock undergoes partial oxidation using a mixture of gasification agents like steam, O2, and CO2. Typically, oxygen is obtained from an air separation unit (ASU), which can be costly. To avoid the need for oxygen externally in gasification, a technique known as Chemical Looping Gasification (CLG) is employed.
[0004] Chemical Looping Gasification utilizes solid oxygen carriers (OC) such as metal oxides (e.g., Fe2O3, Mn2O3, NiO, Cu2O) and a gasification medium of steam and CO2. The fuel undergoes gasification in a fuel reactor where reactions occur among the OC, feedstock, and syngas. The OC is reduced in the process, providing oxygen for gasification, and then transferred to an air reactor where it is oxidized by air, eliminating the need for an expensive air separation unit. The fuel reactor operates at temperatures of 800-1000°C, while the air reactor operates at temperatures of 1000-1200°C, making CLG an efficient and cost-effective gasification method.
[0005] In Chemical Looping Gasification, the syngas produced reacts with the oxygen carrier, generating heat due to exothermic reactions. However, this heat alone is insufficient to meet the heat requirements of the endothermic gasification reactions, necessitating external heat input to the fuel reactor. In the air reactor, the exothermic reactions between the OC and air generate heat. The hot oxidized OC is then transferred to the fuel reactor to fulfil the heat requirements. By integrating heat exchange between the fuel reactor and air reactor, it is possible to avoid the need for external heat input. When no external heat supply is required for both the fuel reactor and air reactor, the operation is known as autothermal chemical looping gasification (aCLG).
[0006] Ammonia is a crucial chemical used as an intermediary in the production of various compounds such as urea, ammonium sulphate, ammonium nitrate, and nitric acid. The synthesis of ammonia involves the reaction of nitrogen (N2) and hydrogen (H2) over an iron-based catalyst at high pressures ranging from 80 to 200 atm. The stoichiometric molar ratio required for the production of ammonia is 3 parts of N2 to 1 part of H2. In commercial processes, hydrogen is typically obtained through steam methane reforming of natural gas using a nickel-based catalyst, while nitrogen is sourced from the air. The resulting syngas, which consists of nitrogen, hydrogen, and inert gases like methane, is then compressed to the desired pressure of around 150 bar before being introduced into the ammonia reactor for the synthesis of ammonia.
[0007] This invention primarily focuses on the continuous conversion of any carbonaceous feedstock into ammonia using the Chemical Looping Gasification method. In this process, the operating temperature of the air reactor is higher than that of the fuel reactor to facilitate the transfer of heat from the air reactor to the fuel reactor through recycled oxygen carrier. The optimal autothermal condition is achieved when there is no oxygen present in the outlet of the air reactor, requiring the air reactor to operate at a temperature where oxygen is absent in the outlet stream. It is noted that there is limited literature available on the continuous operation of Chemical Looping Gasification method.

PRIOR ART OF INVENTION
[0008] In prior art, US Patent No. 2012/0214106 A1 dated 23rd August 2012, claimed to have developed a process to convert fuel into syngas by employing metal oxides. It was claimed that reduction of metal oxide occurs first in the fuel reactor and second reduction occurs in a cyclone and loop seal of FR. It was also claimed that by sending reduced OC to air reactor results in heat. This invention objective being generation of heat and not that of syngas or its applications. This invention does not also mention about aCLG.
[0009] Further, US Patent No. 8,771,549 B2 dated 8th July 2014 has described a method for chemical looping combustion to control the circulation of the solid active mass particles between reaction zones independently by employing one or more non-mechanical valves of L- type valves. In this patent continuous operation of CLG has not been discussed.
[0010] In addition, US Patent No. 9,481,837 B2 dated 1st Nov 2016 has claimed to have developed a process to convert fuel into CO and H2 through chemical looping method. The patent also discussed about applications of syngas generated in the chemical looping method. However, this patent is not discussed about auto thermal operation and conversion of syngas to ammonia.
[0011] In other invention, European Patent No. EP0130846A2 dated 4th July 1984, claimed to have developed a process to produce ammonia from feedstock by syngas generation using air. This invention describes method to convert syngas into ammonia. This invention has used air as gasifying medium but not blend of steam and carbon dioxide. Moreover, the syngas is not generated by employing CLG method. In addition, since air is used as gasification agent in this invention and hence it results in the lower calorific value of synthesis gas.
[0012] In other invention, International patent No. WO90/06281 dated 14th June 1990, claimed to have developed process to convert feedstock into ammonia through syngas. The patent has described the method to convert syngas into ammonia. However, the syngas generated from solid fuels is not considered in this invention. In addition, the invention has not discussed about CLG method.
[0013] In other invention, US patent No. 6448441 B1 dated 10th September 2002, has claimed to have developed a process to maximize H2/CO2 ratio in the syngas to produce ammonia and urea. In this invention, 2 gasifiers have been used to optimize H2/CO2 ratio by feeding different fuels.
[0014] In other invention, US patent No.0303703 A1 dated 2nd December 2010, has claimed to have developed a process to produce ammonia from hydrocarbons like methane, natural gas and naphtha etc by generating syngas. It was claimed that by sending enriched air to secondary reformer, the capacity of syngas will be enhanced. This patent is not applicable for the syngas generated through gasification of solid carbons.
[0015] In addition to above, an International patent No. WO2020085324 A1 dated 30th April 2020 has described a method to reduce energy consumption for ammonia production. It was claimed that for the condition of reaction pressure of 10 MPa and recycle ammonia of 3 %, the energy can be reduced. This patent is particular to optimizing the ammonia loop and syngas generation details are not available.

OBJECTIVES OF INVENTION
[0016] The objectives of the invention include the following:
1. Development of a method that converts feedstock into syngas using the autothermal chemical looping gasification method, which involves utilizing a metal oxide known as the oxygen carrier (OC).
2. Utilization of nitrogen from the air reactor outlet for the generation of ammonia.
3. Use of hot nitrogen from the air reactor and hot syngas from the fuel reactor to produce steam, which is then utilized as a gasifying medium in the fuel reactor.
4. Operation of the entire plant in autothermal mode, where no external heat input is required.
5. Use of carbon dioxide as a gasifying and transport medium for the fuel reactor.
6. Implementation of sand to regulate and control high temperatures in both the fuel and air reactors.

SUMMARY OF THE INVENTION
[0017] The technology described is a process for converting carbonaceous feedstock into ammonia using an auto thermal chemical looping gasification method. Key features of this technology include:
1. Auto Thermal Operation: The process operates in an auto thermal mode, where external heat sources are not required to sustain the endothermic gasification reactions, leading to energy efficiency and cost savings.
2. Chemical Looping Gasification: Solid oxygen carriers, such as metal oxides, are used instead of molecular oxygen from an air separation unit, reducing capital costs and improving sustainability.
3. Syngas Production: Carbonaceous feedstock is converted into syngas through a chemical looping gasification system containing fuel reactors and an air reactor, ensuring continuous syngas generation.
4. Ammonia Synthesis: The syngas is further processed to enhance hydrogen concentration through catalytic water gas shift reactions, and high-purity ammonia is synthesized by mixing hydrogen with nitrogen using an iron-based catalyst.
5. Temperature Control: Sand is utilized to control and regulate temperatures within the reactors, ensuring optimal operating conditions and protecting the equipment from high temperatures.

STATEMENT OF INVENTION
[0018] A process is developed to convert a carbonaceous feedstock into ammonia by employing auto thermal chemical looping gasification method to generate syngas by utilizing metal oxides of Fe, Cu, Mn, Co and Ni rather than utilization air separation unit for oxidation of carbonaceous feedstock. The process comprises of
a) Conversion of carbonaceous feedstock into syngas by employing CLG system containing 2 fuel reactors and 1 air reactor which are operated in auto thermal condition at which no heat is supplied externally, obtained by ensuring no oxygen at the outlet of air reactor which will be met by sending exact amount of air to air reactor for oxidation of reduced OC (metal oxide) coming from fuel reactor;
b) Passing of enough air to air reactor such that exact amount of oxygen required to oxidize to reduced OC coming from fuel rector is supplied by ensuring no oxygen comes out of air reactor which is a condition to obtain auto thermal condition of CLG system as described in (a);
c) Utilization of hot N2 stream coming from air reactor of (a) to generate steam and further to use as a reactant to ammonia production;
d) Utilization of syngas coming from fuel reactor (a) to generate steam and passing of syngas to particulate removal system and scrubber to remove particles from syngas
e) Passing of said syngas (e) to catalytic water gas shift reactor to convert CO to CO2 by admitting steam by which enhancing the concentration of H2 in the syngas;
f) Passing of said syngas (f) to CO2 removal module to remove CO2 from syngas and passing of syngas containing mostly H2 to pressure swing adsorption to separate H2;
g) Passing of said stream containing H2 (g) and N2 gas of (d) to methanator to convert any traces of CO or CO2 to methane resulting no traces of CO and CO2 in the resultant gas;
h) Compressing the resultant gas (h) consisting of H2 and N2 to a desired pressure and admitting the gas to ammonia synthesis loop in which ammonia gets generated;

DESCRIPTION OF DRAWING
[0019] The accompanying drawing shows the method to convert carbonaceous feedstock into ammonia using thermal chemical looping gasification method.

DETAILED DESCRIPTION
[0020] The process shown in Fig.1. describes a method to convert carbonaceous feedstock into ammonia using thermal chemical looping gasification method which employs oxygen carriers (OC) like metal oxides of Fe, Ni, Co, Ni, Mn etc. for oxidation of feedstock.

[0021] The system consists of two fuel reactors (11 and 12) and one air reactor (14). The fuel reactor is where the endothermic gasification reactions take place, while the air reactor facilitates exothermic combustion reactions.

[0022] A carbonaceous feedstock is introduced into a receiver (2) through stream (1) and the carbonaceous feedstock continues to flow through a steam (3) from the receiver (2). A transporting medium of CO2 comes from a compressor (13) through a stream (4) and gets into a first fuel reactor (11) through stream (6), besides a gasifying medium of steam and CO2 enters the first fuel reactor (11) through stream (73b) and stream (7), similarly, the steam and CO2 are admitted into a second fuel reactor (12) through stream (73c) and stream (9) and simultaneously oxidized oxygen carriers (OC) are admitted into the first fuel reactor (11) from an air reactor (14) through stream (19) and into second fuel reactor (12) through stream (22).
[0023] A chemical reaction takes place between oxidized oxygen carriers, carbonaceous feedstock, steam and CO2 in the first fuel reactor (11), as a result syngas is formed from the chemical reaction, the syngas comprises of CO, CO2, H2, CH4, the resultant syngas comes out of the first fuel reactor (11) and second fuel reactor (12) through the streams (27 and 28).
[0024] With the syngas, reduced oxygen carriers comes out of the first fuel reactor (11) and second fuel reactor (12) through streams (20 and 21) and the reduced oxygen carriers get admitted to the air reactor (14), the air is sucked from atmosphere through the compressor (24) into the air reactor (14), through the stream (26) and as a result the reduced oxygen carriers react with air, in the air reactor (14), and an oxidation reaction takes place in the air reactor (14), which is an exothermic reaction, hence heat is liberated, this heat gets transported to the first fuel reactor (11) by means of hot oxidized OC, this heat is used for endothermic reactions in the first fuel reactor (11). Therefore, without utilizing an expensive air separation unit, atmospheric air is used for the oxidation reaction of air reactor (14).
[0025] Hence there is no need for supplying external heat, because the heat required for endothermic reactions in fuel reactor (11), is generated from exothermic reactions of the air reactor (14), and it gets transported to the fuel reactor (11) by means of hot oxidized OC.
[0026] After the formation of syngas, there is an accumulation of ash in the first fuel reactor (11), so it needs to be removed and cleaned, and to ensure continuous operation, gasification reactions are switched on to the second fuel reactor (12). Hence continuous generation of syngas is ensured.
[0027] As the reactors are working under high temperatures, sand is used for controlling their temperatures, the sand is stored in the receiver (16) and flows through stream (15) and it is admitted to the first fuel reactor (11), second fuel reactor (12) and to the air reactor (14) through stream (24, 23 and 18).
[0028] The syngas generated in the first fuel reactor (11) in the above process is admitted to heat recovery boiler (30) through the stream (29) to extract heat from it, the cooled syngas is then admitted to a particulate removal system (32) through stream (31) and separated particles from syngas leaves the system through stream (34), and the syngas leaves the particulate removal system through the stream (33) and from stream (33) the syngas is admitted to a scrubber (35) and water enters the scrubber from stream (41) and it removes fine particles and any other contaminants like ammonia from syngas and the water then leaves the scrubber through stream (74).
[0029] From stream (36) the cleaned syngas then enters into a cross flow heat exchanger (37) and it gets heated and now the heated syngas then enters water gas shift reactor (39) through stream (38), the water gas shift reactor is filled with iron based catalyst, in this reactor, CO gets converted to CO2 by reacting with steam coming from stream (73a), it forms hot hydrogen rich syngas and then it leaves water gas shift reactor through stream (49), further the syngas leaves through stream (42) from cross flow heat exchanger (37) into a CO2 removal module (43).
[0030] In the CO2 removal module (43), the CO2 present in syngas is separated using amine-based absorption, the separated CO2 from syngas leaves through stream (44) and it gets admitted to a storage tank (45). The CO2 is then admitted to the compressor (13) through the stream (46), from which it gets fed to the reactors, the CO2 free syngas leaves through the stream (47) and gets admitted to a pressure swing adsorber (48) where hydrogen is separated from remaining gases, the separated hydrogen then leaves through the stream (49) and gets mixed with nitrogen stream coming through the stream (68).
[0031] The blended gas consisting of N2 and H2 is admitted through a stream (51) into a methanator (52), where any traces of CO and CO2 will be converted to CH4, as a result, the methane gas leaves the methanator through the stream (53) and is then admitted to a compressor (54) and gets compressed to 150 bars. The compressed gas leaves through the stream (55) and it is cooled to a temperature of 250 degree Celsius in the cross-flow heat exchanger (56) and it gets admitted to a first ammonia reactor (58) through the stream (57), where N2 and H2 reacts and forms ammonia. The expected per pass conversion of nitrogen in the first ammonia reactor (58) is 25%.

[0032] The exothermic reaction of forming ammonia results in an increase in temperature at the outlet of the ammonia reactor (58). The outlet stream leaves through stream (59) to a heat exchanger (60). In this heat exchanger the temperature of the ammonia gas is brought to 250 degree Celsius by using water as coolant, the water is admitted to heat exchanger (69) through a stream (70). The cooled ammonia gas is then admitted to a second ammonia reactor (62) through a stream (61). The expected per pass conversion of nitrogen in the second ammonia reactor (62) is 10%. And from the second ammonia reactor (62), it is admitted to a heat exchanger (56) through a stream (63), the ammonia rich syngas from stream (64) from the heat exchanger (56) gets admitted into the ammonia chiller system (65).
[0033] From the ammonia chiller system (65), some part of the ammonia is resent through stream (65b) to stream (53) while the remaining ammonia is withdrawn continuously through the stream (66).
[0034] These steps illustrate the conversion of nitrogen and hydrogen into ammonia through a series of reactions and processes, with the necessary cooling and heat exchange mechanisms in place to optimize the production of ammonia.
[0035] The technology enables continuous operation of the chemical looping gasification system, allowing for a consistent and uninterrupted conversion of carbonaceous feedstock into valuable ammonia. It was clear from this invention that, any carbonaceous feedstock can be converted to ammonia through auto thermal chemical looping gasification method. The ammonia produced can be used for multiple applications such as in the production of urea, ammonium sulphate and nitric acid etc.

, Claims:WE CLAIM -
1. A method for producing ammonia from a carbonaceous feedstock from an auto thermal chemical looping gasification, comprising steps of:
a. introducing the carbonaceous feedstock with steam and CO2 into a first fuel reactor (11), along with oxidized oxygen carriers from an air reactor (14), wherein the carbonaceous feedstock, steam, CO2 reacts with oxidized oxygen carriers thereby generating syngas comprising of H2, CO, CO2, CH4;
b. introducing reduced oxygen carriers produced in the first fuel reactor (11) into the air reactor (14);
c. passing air into the air reactor (14) to oxidize the reduced oxygen carriers from the fuel reactor (11), wherein reduced oxygen carriers react with air thereby producing N2 gas and heat;
d. sending the syngas produced in the first fuel reactor (11) into a particulate removal system (32) and a scrubber (35) to eliminate impurities like ammonia;
e. admitting the syngas without impurities produced in step d into a catalytic water gas shift reactor (39), wherein CO present in the syngas is converted to CO2, thereby enhancing the hydrogen concentration in the syngas;
f. passing of the syngas with enhanced hydrogen concentration into a CO2 removal module (43), wherein CO2 is removed from the syngas;
g. passing of the said syngas into a pressure swing adsorber (48) to separate H2 from the syngas;
h. N2 generated at step d and H2 generated at step g are blended and are introduced into a methanator (52) for conversion of remaining traces of CO and CO2 into methane;
i. compressing the methane gas to a desired pressure and admitting the compressed methane gas into a first ammonia reactor (58), resulting in formation of ammonia and heat,
j. admitting of heated ammonia gas into a heat exchanger (60), wherein it is cooled and sent to a second ammonia reactor (62), resulting in the formation of ammonia;
k. admitting of heated ammonia gas into a heat exchanger (56), wherein ammonia gas is cooled and introduced into an ammonia chiller system (65), from which ammonia is generated.
2. The method as claimed in claim 1, wherein the temperature of the fuel reactor is about 800-1000oC and that of the air reactor is about 1000-1200oC.
3. The method as claimed in claim 1, wherein the carbonaceous feedstock is introduced into a receiver (2), from which a part of it goes into the first fuel reactor (11) and the remaining part of feedstock goes to second fuel reactor(12), wherein first fuel reactor (11) and second fuel reactor (12) have gasifying medium of steam and CO2.
4. The method as claimed in claim 1, wherein metal oxides of Fe, Cu, Mn, Co, and Ni are used as oxygen carriers.
5. The method as claimed in claim 1, wherein the blended gas combining H2 and N2 is admitted to a compressor (54) and gets compressed to 150 bars, and then it is cooled to temperature of 250oC in a cross-flow heat exchanger (56).
6. The method as claimed in claim 1, wherein 25% of N2 is getting converted into ammonia in the first ammonia reactor and 10% of N2 is getting converted into ammonia in the second ammonia reactor.
7. The method as claimed in claim 1, wherein sand is utilized to control the temperature within the fuel reactors and the air reactor.

Dated this 29th day of March, 2024

SOMA RANI MISHRA
IN/PA – 1159
OF L. S. DAVAR & CO.,
APPLICANT’S AGENT