Synthetic Ammonia Process Technology Exchange Area [Daily Question 2009-02-24]

1. Use top and bottom nitrogen injection； 2. Low-temperature purge gas combustion combined with synthetic purge gas, release gas ； 3. Waste heat power generation from blowing air.

Low-temperature purge gas combustion with synthetic vent gas, release gas

Energy conservation and consumption reduction should mean the same thing: 1. Use superheated steam to produce gas, thereby increasing the steam decomposition rate; as a result, both the amount of steam used and the volume of water circulated in the subsequent gas washing tower are reduced. 2. Use high-power fans for strong airflow and short cycles, which accordingly increases the gas production time. 3. The gas generation furnace slag, fine dust from the dust collector, and purge gas are all burned in a waste mixture combustion furnace to produce high-quality steam, which is then used for power generation in gas production. 4. It is beneficial to keep the coal quality as stable as possible, as this helps increase the gas generation rate.

1. Recovery of blast furnace gas, with by-product medium-pressure superheated steam used for power generation； 2. Use an efficient waste heat boiler to recover the thermal energy from the gas generated by the gas burner, superheat it appropriately, and send it off for power generation ； 3. Use low-pressure superheated steam as the gasifying agent to improve the decomposition and conversion rate of carbon ； 4. Appropriately reducing the furnace pressure in the fixed-bed gas generator facilitates the gasification of carbon and reduces the carryover of carbon in the exhaust gas ； 5. A new type of grate is used, which prevents coking at the furnace bottom while appropriately extending the residence time of the carbon layer in the furnace, thereby reducing the residual carbon in the slag.

In the first phase, by leveraging the company’s development advantages and favorable conditions, we will build on existing and under-construction production facilities, strengthen energy management, improve production and technical management, enhance operational efficiency, and fully utilize production potential. The main measures include: 1. Strengthening enterprise energy management, and improving the energy management system over time. 2. Strengthen on-site management in enterprise production to prevent energy loss through leaks, spills, and drips, and eliminate unreasonable energy wastage. 3. Strengthen the management of energy procurement and storage, including: improving coal quality control to prevent the purchase of substandard coal and raising the quality compliance rate of coal ； Strengthen the organized storage management of coal yards to ensure an appropriate inventory level, improve the storage conditions for coal, and reduce energy losses caused by wind and rain ； Strengthen the control and management of the proportion of mixed coal usage, and stabilize the types of coal used in the three furnaces ； Properly manage energy waste in coal yards, and make full use of low-calorific-value energy sources such as screened coal gangue and coke dust ； Actively carry out the recycling of low-calorific solid waste within the enterprise. 4. Strengthen the operational management of energy conversion equipment to improve the utilization rate of primary energy, with a focus on the operational management of boilers and gas generation furnaces. 5. Strengthen the management of energy transmission losses, including regular inspections, improving insulation, and timely adjusting and optimizing the operation of water supply, heating, and power supply networks in order to reduce energy losses during transmission. 6. Strengthen the management of the final stage of energy utilization, including: improving process stability and reducing the amount of process materials that are vented ； Improve the power factor of the power supply system to make full use of electrical energy ； Optimize and stabilize the process conditions in the final stage of energy utilization to increase the system’s production capacity, with a focus on optimizing and stabilizing the operation of ammonia synthesis, methanol synthesis, and urea synthesis. 7. Optimize the existing waste recycling facilities to improve the recovery rate of waste residues, waste gases, and wastewater. In the second phase, production facilities will be expanded and upgraded, with a focus on technological improvements to the main production processes; outdated and energy-intensive equipment will be phased out to improve the energy efficiency of the equipment and bring it to an advanced level. The main measures include: 1. Phasing out outdated transformers with high energy consumption ； 2. Upgrade on-site rotating equipment by using frequency conversion technology and high-efficiency electromechanical devices. 3. Recover the waste heat from urea using lithium bromide technology. 4. Replace the existing copper washing process with a dimethyl process, and transform the current carbonization process into a pressure swing adsorption decarburization process with an annual production capacity of 25,000 tons. The core aspect of the third phase is the overall optimization of the energy system. Develop new energy-saving processes to further improve energy utilization efficiency and reach a leading level in the country. At the same time, adjust the corporate industrial structure to increase the added value of products. The main measures include: 1. Replacing some large electric motors with turbine-driven ones ； 2. Add a set of low-pressure membranes to recover hydrogen from the vent gas in the storage tank. 3. Adjust the product structure to use hydrogen generated during the ammonia synthesis process to produce hydrogen peroxide.

New approaches to saving energy and reducing consumption in ammonia synthesis gas furnaces: It was learned from Jiangxi Changyu Industrial Co., Ltd. that the technical upgrade of the gas furnaces at the ammonia synthesis plant of Fujian Sanming Chemical Co., Ltd., carried out by this company, was a success. After the first gas stove was modified and put into operation, the production capacity increased significantly. Using coal balls could achieve 85% of the gasification effect of lump coal; gas production increased by 25%, while the amount of residual carbon in the coal ash decreased by 50%. Moreover, the cost of coal balls was only 55% of that of lump coal, resulting in notable benefits. It is reported that the synthetic ammonia plant of Sanming Chemical Co., Ltd. is a medium-sized nitrogen fertilizer manufacturer equipped with 14 fixed-bed batch gasifiers, which are used to gasify anthracite and briquetted coal in order to produce urea and other chemical products. For many years, enterprises have been plagued by issues such as an unreasonable height-to-diameter ratio of gas furnaces, inadequate design of their structure, and flawed operational processes. As a result, the production capacity per furnace is low, energy consumption is high, and costs remain elevated. To change this situation, the factory adopted technical upgrades to the gas furnace as a solution. After conducting research and on-site inspections of the existing gasification technology and equipment across the country, they decided to choose Changyu’s gasification technology and equipment. Jiangxi Changyu Industrial Co., Ltd. is both a company that designs and manufactures gas stoves and a firm engaged in the research and development of coal gasification technology. It has successfully carried out systematic design and technical upgrades for coal gasification projects at various domestic enterprises. It is understood that the renovation of Fujian Sanming Chemical Co., Ltd.’s first furnace began at the beginning of this year. Jiangxi Changyu Industrial Co., Ltd. uses a new type of furnace bottom to address the issues of an excessively large angle of repose for ash discharge, too small ash discharge openings, and high wind speeds in the central duct ； The use of a PS-Ⅱ type nitrogen injection injector increased the production load ； The new process has solved problems such as high energy consumption and wasted effective gas production time. After the renovation of the first furnace was completed and it came online, production efficiency increased significantly, production costs were **reduced**, and the energy-saving effects were very noticeable. It is reported that to date, the 14 old furnaces in this plant have been upgraded and put into operation, achieving significant results in energy savings and reduced consumption. Zhao Lequn, an expert in gas production and the chief engineer at Jiangxi Changyu Industrial Co., Ltd., told reporters that currently, more than 40 enterprises across the country that use coal as raw material for producing medium-nitrogen compounds possess a total of over 400 gas furnaces of the same type as those used by Sanming Chemical. These enterprises all face similar problems to varying degrees: low production capacity, high energy consumption, and high costs, all of which severely hinder their survival and development. The technical renovation of Sanneng Chemical’s gas stoves overcame the challenge of producing gas from coal balls, taking gasification technology to a new level and paving a successful path for many fertilizer companies to save energy, reduce costs, and improve efficiency.

I. Basic situation of the renovation for the recovery and utilization of low- and medium-grade thermal energy in production systems: During the production of ammonia and methanol, a large amount of reaction heat is generated, resulting in high-, medium-, and low-grade thermal energy at temperatures ranging from 40°C to 500°C. Although measures such as steam generation and heat exchange between hot and cold materials are employed in the process design to recover energy, a significant amount of medium- and low-grade thermal energy is still wasted. This is evident in the fact that, during energy conversion, due to wet dust removal, high-temperature gas or semi-water gas comes into direct contact with water; this causes a large amount of heat to be used to vaporize the liquid, leading to a high proportion of water vapor in the gas and subsequent backflow of condensed liquid, thereby wasting thermal energy； In the production system, nearly 30,000 m3/h of circulating cooling water is used to transfer heat energy at medium and low levels, with this heat energy then being released directly into the atmosphere. Process overview: For high-temperature waste heat above 500°C, steam is used as the working medium for power conversion to generate electricity and recover energy ； Generating electricity and achieving recycling by using organic fluids as working media for power conversion at temperatures ranging from 200°C to 500°C ； At temperatures of 150–200°C, Freon is used as the working fluid for power conversion purposes in order to generate electricity and achieve recycling ； For waste heat at temperatures below 150°C, lithium bromide units are used to generate the cooling source required for system production, replacing the cooling source provided by once-through water currently in use ； In addition, by taking advantage of current practices such as preheating desalinated water and recycling steam condensate, the waste heat generated during the production process is utilized in a stepwise manner. The flue gas desulfurization and resource utilization project (which has entered the practical implementation phase after expert evaluation) employs an ammonia-fertilizer-based desulfurization process to remove sulfides from the flue gas generated by 220-ton coal-fired boilers. At the same time, the heat contained in the flue gas is utilized for concentrating and crystallizing substances to produce ammonium sulfate. This approach requires low investment and energy consumption, enabling comprehensive resource utilization. Once implemented, the project will enable the reduction of sulfur dioxide emissions by 44,843 tons per year; moreover, sulfur dioxide present in the waste gas along with the residual heat from the flue gas can be used to produce 97,600 tons of ammonium sulfate fertilizer. This results in resource savings and reduced energy consumption, equivalent to 40,000 tons of standard coal saved, bringing significant economic and social benefits. III. Recovery of waste heat from urea using lithium bromide technology – Basic situation: During the production of ammonia and methanol, a large amount of reaction heat is generated, resulting in high-, medium-, and low-grade thermal energy at temperatures ranging from 40°C to 500°C. Although measures such as steam generation and heat exchange between hot and cold materials are employed in the process design to recover energy, a significant amount of medium- and low-grade thermal energy is still wasted. This occurs because, in the energy conversion process, wet dust removal is used; as a result, high-temperature gas or semi-water gas comes into direct contact with water, causing a large amount of heat to be used to vaporize the liquid. This leads to a high proportion of water vapor in the gas, thereby causing condensate to flow back and wasting thermal energy ； In the production system, nearly 30,000 m3/h of circulating cooling water is used to transfer heat energy at medium and low levels, with this heat energy then being released directly into the atmosphere. Process overview: For high-temperature waste heat above 500°C, steam is used as the working medium for power conversion to generate electricity and recover energy ； Generating electricity and achieving recycling by using organic fluids as working media for power conversion at temperatures ranging from 200°C to 500°C ； At temperatures of 150–200°C, Freon is used as the working fluid for power conversion purposes in order to generate electricity and achieve recycling ； For waste heat at temperatures below 150°C, lithium bromide units are used to generate the cooling source required for system production, replacing the cooling source provided by once-through water currently in use ； In addition, by taking advantage of current practices such as preheating desalinated water and recycling steam condensate, the waste heat generated during the production process is utilized in a stepwise manner. IV. Replacing the copper washing process with the dimethyl process: Basic principles include making rational use of resources, reducing energy consumption, focusing on pollution control, promoting technological advancement, and achieving sustainable development for the enterprise. The implementation of this project can accelerate the in-depth development of Shandong Deqilong Chemical Group Co., Ltd. in the chemical industry, enable an organic integration of coal, chemicals, and power production, and holds significant strategic importance for improving the company’s economic performance and its position in the consumer market in East China, as well as for boosting local economic development. This project is technically reliable and economically viable, offering good economic and social benefits. This process replaces the copper washing method, eliminating the generation of copper-contaminated dilute ammonia solution; it also produces methanol as a by-product, thereby enriching the product portfolio and turning waste into value. The environment was changed, preventing pollution. Process overview: The compressed feed gas (with CO ≤ 3.5% and CO2 ≤ 0.2%) is separated from oil and water, after which it first passes through a preheater before the methanol tower (tubular type) to be heated to 160°C–180°C. It then enters the methanolization tower at its bottom, where it is heated to 210°C–230°C by the heat exchangers inside the tower; from there it enters the catalyst layer via the central tube to undergo the methanolization reaction, with the temperature reaching 250°C. The reaction gas passes through the heat exchanger inside the tower, and before entering the tower it is preheated in the preheater (inside the tubes). The gas that comes out of the preheater is then cooled by water before entering the methanol separator; the crude methanol separated there is sent to the intermediate tank. Part of the unreacted gas (the gas after the alcohol separation step) goes to the recycler for circulation within the system, while another part goes to the preheater before the hydrocarbonization tower (outside the tubes), and from there it enters the bottom of the hydrocarbonization tower. After heat exchange inside the tower, it passes through the central tube and reaches the catalyst layer where the hydrocarbonization reaction takes place. The gas resulting from this reaction exits from the lower part of the tower and enters the preheater (inside the tubes) again, where it exchanges heat with the gas entering the tower. After this heat exchange, it is cooled by water once more, and finally it enters the separation unit. The gases released due to moisture (hydrocarbonated gases), CO + CO2, amount to about 5 ppm; these are then compressed and pressurized for use in the synthesis of ammonia.

I mainly analyze it from a purely technical perspective, as that makes it easier to implement. The energy consumed in the fixed-carbon gasification process includes: fuel energy, steam, electricity consumption, cooling water counted as energy, and energy equivalent of soft water. Recyclable energy sources include: the energy equivalent derived from the recycling of combustibles (recycling of combustibles in waste materials, recycling of ash and slag) ； By-product steam. Based on the above analysis and the methods suggested by others, I make the following additions: 1. Adopt a gas production process that uses an oxygen-enriched steam mixture for continuous gas generation ； 2. Use coal lumps with smaller particles ； 3. The tar separated by the tar separator cannot be separated using current technology, and thus it can be sprayed back into the gasification furnace ； 4. Using pressure swing adsorption technology to produce enriched oxygen eliminates the need for air separation equipment ；