Cellulose Carbamate Production via Integrated Pulp Mill Urea Recycling
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Solution Overview
Problem
The high cost and environmental concerns associated with producing cellulose carbamate (CCA) and microcrystalline cellulose (MCC) in stand-alone systems, along with the challenge of managing nitrogen compounds and harmful emissions in chemical pulp mill processes, hinder the commercial success of CCA production and the integration of these processes with chemical pulp mills.
Innovation Solution
Integrating microcrystalline cellulose production with cellulose carbamate production within a chemical pulp mill, utilizing acid hydrolysis and reacting MCC with urea at elevated temperatures, while utilizing flue gas carbon dioxide to convert ammonia back into urea, thereby minimizing nitrogen input and emissions, and recycling waste streams for nutrient value or biogas production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If CCA and MCC are produced in stand-alone systems, then production flexibility is maintained, but production costs increase and environmental sustainability deteriorates
Solution Approach 1:
The patent combines CCA production and MCC production into a single integrated system within a chemical pulp mill. The CCA production unit reacts cellulose with urea to form carbamated cellulose, while the MCC production unit simultaneously performs acid hydrolysis to produce microcrystalline cellulose. This merging of operations reduces overall production costs by utilizing shared infrastructure, utilities, and waste heat, while maintaining product quality and production flexibility.
2Productivity
If ammonia is released during carbamation reaction, then carbamation efficiency is maintained, but nitrogen emissions increase
Solution Approach 1:
The patent captures ammonia gas released during the carbamation reaction and converts it into ammonium sulfate fertilizer through reaction with sulfuric acid. This transformation converts a harmful nitrogen emission into a valuable agricultural product. The system maintains high carbamation reaction efficiency by allowing ammonia release, then immediately captures and utilizes the ammonia to produce fertilizer, thereby eliminating environmental pollution while creating additional economic value.
3Loss of substance
If flue gas carbon dioxide is utilized to convert ammonia back into urea, then nitrogen input is minimized, but process complexity increases
Solution Approach 1:
The patent implements a urea recycling system where ammonia released during carbamation is captured and converted back into urea by reacting with carbon dioxide from flue gas. This recovered urea is then fed back into the carbamation reaction process. This closed-loop approach minimizes nitrogen compound loss by recovering and reutilizing ammonia, reducing the need for fresh urea input while maintaining product quality and reaction efficiency.
4Object-affected harmful factors
If waste streams are recycled for nutrient value or biogas production, then environmental sustainability is enhanced, but waste management complexity increases
Solution Approach 1:
The patent enables the integrated system to serve its own waste management needs by internally processing and utilizing its own waste streams. Ammonia from carbamation is converted to ammonium sulfate fertilizer, carbon dioxide from flue gas is used to regenerate urea, and other organic waste streams are directed to biogas production or nutrient recovery. This self-service approach enhances environmental sustainability by minimizing external waste discharge while reducing the need for complex external waste treatment infrastructure.
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 integrated process reduces production costs, minimizes nitrogen and carbon dioxide emissions, and enhances the environmental sustainability of CCA production by reusing urea and managing waste streams effectively, making it a more viable alternative to traditional viscose fiber production methods.
Implementation Method 1
Urea starts to decompose when the temperature exceeds 133° C., and the intermediate products isocyanic acid and ammonia are formed
Implementation Method 2
Isocyanic acid reacts further with OH-groups of cellulose by forming a carbamate group to the cellulose backbone
Implementation Method 3
Due to elevated temperature, the water is evaporated and the CCA thus formed is physically in solid form
Implementation Method 4
carbon dioxide from the flue gases is reacted with released ammonia to produce urea, which is used in the carbamate production
Implementation Method 5
microcrystalline cellulose is produced from chemical pulp produced at a pulp mill, such that the chemical pulp is subjected to acid hydrolysis at an elevated temperature
Data Source
AI summary
A method for controlling discharges of nitrogen compounds in the production of cellulose carbamate (CCA). Microcrystalline cellulose is produced from chemical pulp produced at a pulp mill, such that the chemical pulp is subjected to acid hydrolysis at an elevated temperature to form microcrystalline cellulose (MCC) and hydrolysate, and the MCC is reacted with urea to produce cellulose carbamate whereby ammonia is released. The microcrystalline cellulose production and the cellulose carbamate production are integrated into the pulp mill having a flue gas system such that carbon dioxide from the flue gases is reacted with released ammonia to produce urea, which is used in the carbamate production.