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Application of coal-saving agent technology in nitrogen fertilizer gas production I. Basic principles: By combining techniques such as the homogenization of coal, thermodynamics, coal chemical engineering, surface chemistry, catalytic gasification technologies, and oxygenation methods to promote combustion at the center of briquettes, energy-saving and coal-saving gasification briquettes for synthetic ammonia production are created. II. Technical aspects: Catalytic gasification technology that enables a CO2 decomposition rate of over 70% is employed, along with oxygen-enrichment technology that promotes combustion in the core area of the briquettes. This allows for catalytic gas reactions, as well as both external and internal combustion, thereby increasing the carbon conversion rate and the proportion of useful gas components ； By using a binder composed of various metal compounds with different melting points combined with calcareous materials, the gasified coal achieves high thermal stability, a sufficiently high ash melting point, adequate cold and thermomechanical strength, long-term water resistance, and the ability to cure naturally without the need for drying. The newly produced industrial coal can be stacked to a height of 4 meters and allowed to cure naturally. a. Catalytic gasification technology that can promote a CO2 decomposition rate of over 70%. To increase the combustion temperature of gasified coal and enhance the chemical reactivity of CO2 – thereby increasing its decomposition rate and boosting the gas production – it is necessary to use appropriate catalysts to reduce the reaction activation energy. After repeated experiments, we used two types of aerospace materials that remain stable at room temperature, along with weak acid salts as catalytic additives. Under high-temperature conditions, the catalyst catalyzes the decomposition of the water in coal to produce hydrogen and oxygen ； At the same time, the gases generated during coal combustion, as well as those produced by various components such as oxygenators, binders, and smoke-reducing sulfur-removal agents, are subjected to ion exchange to produce combustible gases such as methane and water gas ； The gasified briquettes produced were tested by the **Coal Quality Supervision and Inspection Center**, and the decomposition rate of CO2 at 1100°C reached 75% and 73.8%, which is nearly 35 percentage points higher than that of lump coal. b. Coal-saving combustion technology to promote combustion at the center of briquetted coal. As is well known, various types of briquetted coal and anthracite undergo a gasification process that is of the external combustion type (that is, combustion occurs from the outside inward). It takes a long time to burn through these briquettes completely; as a result, the carbon in the center of the coal cannot be fully converted. The ash contains a high proportion of carbon (20%-30%), leaving behind a black core, which results in waste of coal, reduced gasification efficiency, and energy loss. Coal-saving technology is achieved by using an oxygenating agent composed of a combination of two or more oxidants and bulking agents. Thanks to the action of the oxygenator, the traditional external combustion method is overcome, and the briquettes burn simultaneously from the outside inward as well as from the inside outward during the combustion process ； Due to the use of a leavening agent, its micro-explosive effect creates voids in the briquette, thereby increasing the surface area of the briquette’s interior that is in contact with oxygen. This enhances the burning rate of the briquette, eliminates any dark cores within it, ensures complete combustion, and significantly improves the efficiency of its burning. c. Technical and quality indicators: 1. Carbon conversion rate; the content of useful gases ≥ that of high-quality lump coal of the same type. 2. Specific coal consumption ≤ that of high-quality lump coal of the same type. 3. SO2 emissions reduced by over 45%. 4. Unit production cost reduced by over 40% compared to high-quality lump coal. 5. Utilization rate of gasified coal briquettes: 100% (referring to the proportion replacing lump coal). 6. Carbon content in coal slag is significantly reduced. III. Physical and chemical properties of gasified coal briquettes and technical controls: The properties of the raw coal have a significant impact on the gasification process, as they affect the type of gasification and the gasification efficiency. 1) Moisture: Excess moisture in gasified coal increases heat loss, thereby reducing coal gas production and gasification efficiency. In briquette production, the total moisture content should be kept at 8% to 12%; after curing, the overall moisture content of the briquettes is approximately 6%. 2) Ash: Ash itself is an inert substance. Fuel with a high ash content not only increases transportation costs but also deteriorates the gasification conditions. When the ash content is too high, during the gasification process, part of the carbon surface is covered by ash, which reduces the contact area between the gasifying agent and the carbon surface. This affects the diffusion of the gasifying agent, lowers the chemical reactivity of the fuel, and increases the amount of carbon that is discharged along with the ash. As a result, there is more carbon loss and increased wear on the ash disposal equipment. Therefore, when selecting raw coal, it is necessary to choose coal varieties with low ash content based on the local coal conditions. 3) Sulfur content: About 80% of the sulfur in coal is converted into hydrogen sulfide during the gasification process and ends up in the gas. This not only corrodes metals but also poisons catalysts when used in syngas production. In this project, we address the sulfur fixation issue in the raw coal by adding a sulfur-fixing and smoke-reducing agent. Its components are mainly synthesized from four or more raw materials such as calcium oxide, magnesium oxide, and iron oxide trioxide; by utilizing the chemical properties of these substances at high temperatures, the sulfur content in coal is converted into solid sulfates that are trapped within the coal ash. This not only ensures the quality of the syngas but also helps achieve the goal of clean production. 4) Volatiles: The volatiles in briquettes are dried and distilled in a gasifier to produce gas and tar vapor. Gasified briquettes for different applications have varying requirements regarding volatile matter; those used to produce raw gas for synthetic ammonia production require a volatile matter content of no more than 6%. IV. Coal gasification and basic chemical reactions a. Overview of coal gasification Coal gasification generally refers to the process in which coal reacts with air, oxygen, carbon dioxide, water vapor, or mixtures of these gases to produce various types of gas. Coal gasification involves the pyrolysis of coal to produce semi-coke, which is then gasified together with a gasifying agent at high temperatures. The raw coal can be lignite, bituminous coal, and anthracite. Gassing agents commonly include air, oxygen, water vapor, or carbon dioxide; in recent years, hydrogen and mixtures of these substances have also been used. The components of the generated gas include carbon monoxide, carbon dioxide, hydrogen, and water vapor; when air is used as the vaporization medium, nitrogen is also present. b. Basic concepts of the coal gasification process The coal gasification process takes place in a gasifier. Gasification furnaces are usually cylindrical, with a shell made of steel plates and an inner lining of refractory bricks. The gasification furnace consists of a furnace body, a coal feeding device, an ash discharge device, a furnace grid (also known as a grate or furnace bars), a gasifier inlet, a gas outlet, and other components. Schematic diagram of the gas generator. The briquette layer in the gasification furnace can be divided into five layers from bottom to top: 1) Ash layer ； 2) Oxide layer—primarily involves the combustion reaction of carbon ； C+O2→CO2 3) Reduction layer – primarily carries out the reduction of carbon dioxide and the decomposition of water vapor: C+O2→2CO, CO2 + C→2CO, H2O+C→H2+CO 4) Drying layer – the briquette is dried to form semi-coke or coke, while the volatiles in the coal are released as drying gas. 5) Drying layer. The oxide layer and the reduction layer are collectively referred to as the gasification layer, which is the main area where gas is produced. The dry plating layer and the drying layer together are called the preformed layer. In the gasification furnace, it appears to be a layered process, but in reality the layering is not distinct; the layers overlap each other. Schematic diagram of the general production process; comparison of the conditions before and after gasification using coal with a fuel-saving agent: Table 1 shows a comparison of coal quality test results. For coal subjected to gasification, as well as coal with a fuel-saving agent added during gasification: Fixed carbon FC – 63% vs. 63%; Ash content Aad – 28.68% vs. 28.9%; Volatile matter Vad – 7.6% vs. 7.6%; Moisture content Mad – 0.64% vs. 0.7%. Table 2 presents a comparison of the gas composition: Carbon monoxide – 23%-26% vs. 27%-30%; Carbon dioxide – 11%-12% vs. 9%-10%; Hydrogen – 40%-41% vs. 47%-50%; Oxygen – 0.7%-0.8% vs. 0.8%-1%; Nitrogen – 17%-18% vs. 11%-16%