Steam Boiler Scale Prevention via EDTA Concentration Control
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Solution Overview
Problem
Steam boilers face challenges in preventing scale formation and controlling chemical oxygen demand in boiler water, leading to inefficiencies and environmental concerns despite the use of corrosion and scale preventive agents.
Innovation Solution
A method for operating a steam boiler that involves using feed water with a hardness of 5 mg CaCO3/L or less, supplemented with a chemical aqueous solution containing alkaline metal silicate, alkaline metal oxide, and ethylenediamine tetraacetate or its alkaline metal salt, with the concentration of the scale preventive agent set at least 1.5 mol equivalent times relative to the feed water hardness, and controlling the condensation rate to maintain a concentration of 40 mg EDTA/L or less in the boiler water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ethylenediamine tetraacetate or its alkaline metal salt is added to prevent scale formation, then scale prevention is improved, but chemical oxygen demand increases
Solution Approach 1:
The patent changes the concentration parameter of the scale preventive agent in the feed water to optimize the balance between scale prevention and COD control. By precisely controlling the amount of ethylenediamine tetraacetate added, the system achieves effective scale prevention while keeping COD within acceptable limits for environmental discharge standards.
2Reliability
If feed water hardness is reduced to prevent scale, then scale formation is suppressed, but water treatment complexity increases
Solution Approach 1:
The patent applies preliminary action by adding a scale preventive agent to the feed water before it enters the boiler system. This preventive measure addresses potential scale formation issues in advance, allowing the use of feed water with slightly higher hardness (up to 10 mg CaCO3/L) without requiring excessively complex water treatment systems.
3Reliability
If corrosion preventive agents are added to protect heat transfer pipes, then corrosion resistance is improved, but boiler water composition control becomes more difficult
Solution Approach 1:
The patent merges the functions of corrosion prevention and scale prevention by using a combined approach where feed water undergoes both softening treatment and addition of scale preventive agents. This integrated water treatment strategy protects against both corrosion and scale formation while maintaining relatively simple control of boiler water composition through coordinated management of multiple water quality parameters.
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 effectively prevents scale formation in steam boilers while keeping the chemical oxygen demand of boiler water below 30 mg/L, meeting environmental standards and reducing the risk of scale generation.
Implementation Method 1
the water softening device used in the steam boiler apparatus is able to remove hardness components (a magnesium ion and a calcium ion) in raw water by ion exchange using a cation exchange resin
Implementation Method 2
a scale preventive agent capable of preventing generation of a scale by chelating the hardness component
Data Source
AI summary
Boiler water is heated in a steam boiler while feed water, which has a hardness of 5 mg CaCO3/L or less and is used as the boiler water, is supplied to the steam boiler. A part of the boiler water is appropriately disposed of. A chemical aqueous solution containing an alkaline metal silicate, an alkaline metal hydroxide and at least one kind of scale preventive agents of ethylenediamine tetraacetate, and its alkaline metal salt, is supplied to the feed water so that a concentration of the scale preventive agent is at least 1.5 mol equivalent times relative to the hardness of the feed water. In the steam boiler, a condensation rate of the boiler water is set so that the concentration of the scale preventive agent in the boiler water is 40 mg EDTA/L or less.