How to use scale inhibitor ATMP in papermaking industry

Using the scale inhibitor ATMP (Amino Trimethylene Phosphonic Acid) in the papermaking industry is a highly effective practice, primarily targeting calcium carbonate and sulfate scale control. Here’s a detailed guide on how and where to use it.

Overview: Why ATMP is Used in Papermaking

The papermaking process involves large volumes of water with high levels of dissolved ions (calcium, magnesium, carbonate, sulfate). These ions can precipitate under conditions of high temperature, pH, and concentration, forming hard scale on critical equipment. Scale causes:

Reduced heat transfer in heaters and dryers.

Clogged showers and nozzles, leading of poor paper quality.

Increased energy consumption due to inefficiency.

Downtime for costly cleaning and descaling.

ATMP is an excellent organic phosphonic acid scale inhibitor that prevents these deposits through threshold inhibition and crystal distortion, keeping scaling ions soluble in the water.

1. Key Application Points in the Papermaking Process

ATMP is typically dosed into the water circuits where scaling tendencies are highest. The primary application points are:

Application Point Primary Target Scale Purpose

Pulp Washing & Bleaching Systems Calcium Carbonate, Calcium Oxalate Protects washers, filters, and showers from scaling, ensuring efficient washing and bleaching chemical application.

Chemical Recovery Systems (Black Liquor Evaporators) Calcium Carbonate (Most Critical), Sulfate This is often the most critical application. Prevents severe scaling on heat exchanger surfaces in multi-effect evaporators, maintaining efficiency and reducing cleaning frequency.

Paper Machine Whitewater System Calcium Carbonate, Precipitated Solids Prevents scale in savealls, tanks, pipes, and most importantly, the wire pit showers and felt showers. Clean showers are vital for sheet formation and water removal.

Coating Circuit Calcium Carbonate Prevents scale in pumps, pipes, and applicators used for paper coating mixtures.

Cooling Water Systems Calcium Carbonate If the mill has its own cooling system, ATMP is used to protect cooling towers and heat exchangers.

2. How to Determine Dosage

The optimal dosage of ATMP is not fixed; it depends on your specific water chemistry and process conditions. The general range is between 2 - 20 ppm (parts per million) in the process water stream.

To determine the correct dosage, follow these steps:

Water Analysis: Conduct a full water analysis of the make-up water and the circulating whitewater. Key parameters to measure:

Calcium Hardness (as CaCO₃)

Total Alkalinity (as CaCO₃)

pH

Temperature

Conductivity

Oxalate, Sulfate, and Chloride levels

Scale Prediction Software: Use industry-standard software or saturation indices (like the Langelier Saturation Index - LSI) to model the scaling potential of your water. This will give a scientific basis for the required inhibitor dose.

Trial & Monitoring (Most Common Method):

Start with a baseline dose of 5-10 ppm.

Monitor scaling tendencies: Use inline monitoring equipment (e.g., a pilot-scale test heat exchanger with probes that measure heat transfer resistance) or simply monitor the pressure drop across showers and heat exchangers.

Inspect regularly: Physically inspect showers, pipes, and tanks for scale formation.

Adjust the dose: If scale is forming, increase the dose incrementally. If no scale is present, you may cautiously try to reduce the dose to find the most economical level.

3. How to Apply ATMP: Dosing Procedure

ATMP is typically supplied as a 50% aqueous solution. It is easy to handle and dose.

Dilution (Optional): For more accurate dosing with smaller pumps, ATMP can be diluted with soft water (e.g., to a 10-20% solution). Note: Diluted solutions have a shorter shelf life and are more prone to biological degradation.

Dosing System: Use a chemical metering pump (e.g., a diaphragm pump) to inject the ATMP solution continuously into the process stream.

Injection Point: The injection point should be chosen where there is good mixing, BEFORE the point where scaling is likely to occur (e.g., upstream of a heat exchanger or shower header). A turbulent flow point in a pipe is ideal.

Safety: ATMP is acidic. Handling requires appropriate Personal Protective Equipment (PPE): safety glasses, gloves, and protective clothing. Always refer to the Safety Data Sheet (SDS) provided by the supplier.

4. Benefits of Using ATMP in Papermaking

Effective Scale Control: Highly effective against carbonate scales, even at low dosages.

Thermal Stability: Performs well in the high-temperature environments of evaporators and dryers.

Synergy: Works well with dispersants and corrosion inhibitors, allowing for a tailored treatment program.

Improved Efficiency: Maintains heat transfer efficiency and ensures consistent operation of showers, leading to higher productivity and reduced energy costs.

Reduced Downtime: Drastically reduces the frequency of mechanical and acid cleaning shutdowns.

5. Important Considerations & Best Practices

Not a Dispersant: While ATMP is excellent at preventing scale, it is not a h3 dispersant for organic materials or clay. It is often used in combination with polymers (e.g., polyacrylates) that provide dispersing power for other suspended solids.

Calcium Tolerance: ATMP has good calcium tolerance, but at very high calcium hardness and high pH, it can itself form a calcium-ATMP precipitate. This is why water analysis and proper dosing are critical.

Compatibility with Bleach: ATMP is relatively stable to oxidants like chlorine, but high oxidizing agent doses can slowly degrade it. Dosage may need to be adjusted in bleaching stages.

Microbiological Growth: Phosphonates can be a nutrient source for some microbes. It is essential to have an effective biocontrol program (e.g., using biocides) in place to prevent downstream biological growth.

Conclusion:

To use ATMP effectively in the papermaking industry, identify the critical scaling points (especially evaporators and showers), conduct a water analysis to understand the scaling potential, and apply a continuous, well-mixed dose starting in the range of 5-10 ppm. Continuously monitor the system and adjust the dosage to find the most cost-effective level that prevents scale and ensures efficient, uninterrupted production.