PBCT-PAS-PM Cooling Water Composition for High COC Scale Control
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Solution Overview
Problem
Current methods for controlling scale and deposition in evaporative cooling towers are inadequate for operating at high cycles of concentration (COC), leading to excessive blowdown and environmental impact, with existing chemical compositions and materials failing to effectively prevent scale formation and corrosion at increased COC levels.
Innovation Solution
A composition comprising an aqueous solution of 2-phosphonabutane-1,2,4-tricarboxylic acid (PBCT), polyacrylic acid species (PAS), and polymaleic acid (PM) in softened water, with adjustable pH, is used to maintain a concentration of PBCT in the treated cooling water between 6 to 14 mg/L, allowing for increased COC operation while preventing mineral scale and deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If cooling towers operate at higher cycles of concentration (COC) to reduce blowdown and water consumption, then water conservation and environmental impact are improved, but scale formation and deposition increase due to exceeded saturation limits
Solution Approach 1:
The patent changes the chemical parameters of the cooling water system by introducing a specific composition of scale inhibitors and corrosion inhibitors. This composition allows the system to operate at higher COC levels (above 6, up to 20 or higher) by modifying the chemical environment to prevent scale formation despite increased dissolved solids concentration. The composition includes phosphonates, polyacrylic acid, and other chemicals that alter the saturation behavior of calcium carbonate and other scales.
Solution Approach 2:
The patent uses a composite chemical composition containing multiple active ingredients working together: phosphonates (for scale inhibition), polyacrylic acid (for dispersion and scale prevention), corrosion inhibitors (for metal protection), and biocides (for biological control). This composite approach enables the system to handle high COC operations by providing multiple mechanisms of action against different types of scaling and corrosion simultaneously.
2Object-affected harmful factors
If scale inhibitors are added to prevent scale formation at high COC, then scale control is improved, but the system is limited to maximum 150-200 times saturation and COC is restricted
Solution Approach 1:
The patent fundamentally changes the saturation parameters by using a synergistic composition that shifts the saturation curve. Instead of working within traditional saturation limits, the composition allows operation at supersaturated conditions (COC > 6, potentially 20 or higher) by modifying the chemical activity of calcium and carbonate ions through complexation with phosphonates and polyacrylic acid, thereby expanding the operational COC range beyond conventional limits.
Solution Approach 2:
The patent introduces chemical intermediaries (phosphonates and polyacrylic acid) that act as mediators between the dissolved solids and the scale formation process. These intermediaries bind to calcium ions and other scale-forming species, preventing them from precipitating as scale even at high concentrations. This mediation allows the system to tolerate much higher COC levels without reaching the traditional saturation barrier.
3Reliability
If traditional chemical treatments are used in cooling towers, then corrosion and biological control are maintained, but blowdown contains high dissolved solids and toxic biocides creating environmental impact
Solution Approach 1:
The patent changes the concentration parameters by enabling operation at higher COC, which concentrates the chemicals in the system water. This reduces the absolute amount of chemicals needed and consequently reduces the volume and concentration of toxic substances in the blowdown, even though the COC is higher. The synergistic composition allows for reduced dosage rates while maintaining effectiveness.
Solution Approach 2:
The patent implements a feedback mechanism where the system operates at high COC to concentrate and recycle water and chemicals, minimizing blowdown. The high COC itself acts as a feedback control that naturally reduces the need for fresh chemical addition and minimizes discharge, creating a self-regulating system that reduces environmental impact while maintaining corrosion and scale control.
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
The solution effectively reduces blowdown from evaporative cooling towers by allowing operation at higher COC levels, minimizing scale and deposition, and reducing the environmental impact by conserving water and limiting the discharge of toxic materials.
Implementation Method 1
A method of preventing mineral scale and deposition within a cooling tower... adding each of the core components of phosphonobutane tricarboxylic acid (PBCT), a polyacrylic acid species (PAS), polymaleic acid (PM)... so as to maintain a level of PBCT in the treated cooling water of from about 6 mg/L to about 14 mg/L
Implementation Method 2
From 75% to 80% of the incoming heat load to an evaporative cooling tower is removed by evaporation of cooling water
Data Source
AI summary
A method and chemical composition are provided which permit operation of evaporative cooling towers at increased cycles of concentration without formation of calcium scale. The method can include first determining the calcium hardness and total alkalinity of the makeup water, calculating the operating cycles of concentration using a formula developed for the specified chemical composition, then dosing the treated water to maintain a constant level of the chemical composition. The method permits scale-free operation of evaporative cooling towers at a minimum of two (2) cycles of concentration over existing technology.