Integrated Ammonia-Urea Process Heat Integration
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Solution Overview
Problem
Current integrated ammonia-urea production systems face challenges due to high operational pressures and temperatures, energy requirements, and economic inefficiencies, particularly in the urea production section, which necessitates the development of more efficient methods for producing urea.
Innovation Solution
A method involving the exchange of heat from syngas comprising hydrogen and carbon dioxide to a urea solution containing ammonium carbamate, where the heat decomposes at least a portion of the ammonium carbamate, optimizing the production of urea by reacting syngas with liquid ammonia to create a carbon dioxide lean syngas and ammonium carbamate solution, and subsequently heating the solution to dehydrate it into urea.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the urea section is operated at high pressures and temperatures to achieve high conversion rates, then the conversion of ammonium carbamate to urea is improved, but the energy consumption and operational complexity increase significantly
Solution Approach 1:
The patent combines the ammonia synthesis loop and urea production section into an integrated system where the ammonia synthesis gas cooler serves dual purposes: cooling the synthesis gas and providing heat for ammonium carbamate decomposition in the urea section. This heat integration allows the system to achieve high conversion rates without proportionally increasing external energy input, as the heat required for urea production is partially supplied by the exothermic ammonia synthesis reaction itself.
Solution Approach 2:
The patent utilizes the temperature and pressure parameters dynamically - the ammonia synthesis operates at high pressure and temperature to produce ammonia exothermically, and these same parameters are leveraged in the urea section where the hot synthesis gas at high pressure directly heats and pressurizes the ammonium carbamate solution, promoting decomposition and urea formation without requiring separate high-pressure compressors or external heating systems for the urea section.
2Productivity
If the urea section is integrated with the ammonia plant, then the overall production efficiency is improved, but the shutdown of the urea section necessitates shutdown of the ammonia section, reducing operational flexibility
Solution Approach 1:
The patent merges the ammonia synthesis and urea production into a single integrated process flow where the ammonia synthesis gas cooler is thermally coupled to the urea production system. This integration creates a unified system that operates efficiently as a whole, but the design allows for staged operation where the urea section can be isolated and maintained while the ammonia synthesis continues, or vice versa, by controlling the flow and thermal coupling between sections.
3Productivity
If a large amount of energy in the form of steam and compressors is used to operate the urea section, then the production capacity is improved, but the economic viability decreases
Solution Approach 1:
The patent implements self-service by having the ammonia synthesis section automatically provide the heat and pressure energy required by the urea section through the thermal coupling of the synthesis gas cooler. The exothermic ammonia synthesis reaction generates heat that is directly used to drive the endothermic ammonium carbamate decomposition, and the high-pressure synthesis gas directly pressurizes the urea reaction system. This eliminates or reduces the need for separate steam generators and high-pressure compressors for the urea section, significantly reducing operational costs and improving economic viability while maintaining high production capacity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces energy consumption and operational pressures, enhancing the efficiency and economic viability of urea production while maintaining high conversion rates of ammonium carbamate to urea.
Implementation Method 1
the heat transferred can be sufficient to decompose at least a portion of the ammonium carbamate
Implementation Method 2
The second reaction for producing urea is endothermic and does not go to completion
Implementation Method 3
A method involving the exchange of heat from syngas comprising hydrogen and carbon dioxide to a urea solution containing ammonium carbamate
Implementation Method 4
The first reaction producing ammonium carbamate is an exothermic reaction and essentially goes to completion
Data Source
AI summary
Methods for producing urea are provided. A method for producing urea can include exchanging heat from a syngas comprising hydrogen and carbon dioxide to a urea solution comprising urea and ammonium carbamate. The heat transferred can be sufficient to decompose at least a portion of the ammonium carbamate. In one or more embodiments, the syngas can be reacted with liquid ammonia to provide a carbon dioxide lean syngas and an ammonium carbamate solution. The ammonium carbamate solution can be heated to a temperature of about 180 C. or more. At least a portion of the ammonium carbamate in the heated ammonium carbamate solution can be dehydrated to provide the urea solution.