Segmented Urea Plant Valve for Corrosion and Heat Treatment
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Solution Overview
Problem
Existing urea production plants face challenges with valves that lack sufficient corrosion resistance and mechanical properties, particularly in high-pressure environments, leading to high capital expenditure and limited lifetime due to the aggressive nature of carbamate-containing process streams.
Innovation Solution
A valve design comprising an inner body part made of highly corrosion-resistant duplex stainless steel and an outer body part made of a less corrosion-resistant material, allowing for separate manufacturing and easier heat treatment, with the inner part directly exposed to the corrosive environment and the outer part shielded, enabling complex shapes and reduced manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single body valve made of duplex stainless steel is used, then corrosion resistance is improved, but manufacturing complexity and heat treatment difficulty increase
Solution Approach 1:
The valve body is divided into two separate parts: an inner body part made of corrosion-resistant duplex stainless steel and an outer body part made of less expensive material. This segmentation allows each part to be optimized independently - the inner part provides corrosion resistance where needed, while the outer part provides structural support at lower cost, resolving the contradiction between reliability and manufacturing complexity.
Solution Approach 2:
Instead of making the entire valve body from expensive duplex stainless steel, the corrosion-resistant material is applied only to the inner body part that directly contacts the corrosive carbamate-containing process streams. This local quality approach provides corrosion resistance exactly where it is needed, reducing overall material costs and manufacturing complexity while maintaining reliability.
2Reliability
If a single body valve is replaced entirely at end of lifetime, then reliability is maintained, but capital expenditure increases
Solution Approach 1:
By segmenting the valve body into replaceable inner and outer parts, the invention enables selective replacement of only the inner body part when it reaches the end of its service life, rather than replacing the entire valve. This significantly reduces capital expenditure while maintaining reliability, as the outer body part can be reused if it is still in good condition.
Solution Approach 2:
The design allows the outer body part to be recovered and reused after the inner body part is replaced. This discarding and recovering principle reduces the quantity of new materials needed and lowers capital expenditure, while the reliable inner part is replaced only when necessary to maintain valve performance.
3Strength
If large size valve blocks are heat treated, then mechanical properties are improved, but heating and cooling uniformity deteriorates
Solution Approach 1:
Dividing the valve body into smaller inner and outer parts allows the inner part to be heat treated more uniformly. The smaller size of the inner body part enables better heat penetration and more uniform temperature distribution during heating, and more uniform cooling, resulting in improved mechanical properties without the defects associated with heat treating large monolithic blocks.
Data Source
AI summary
The disclosure pertains in certain embodiments to a plant and to urea production in a plant comprising a valve body comprising an inner body part and an outer body part.