Project Overview

Industry: Soda Ash & Ammonium Chloride (Combined Alkali Process)

Application: Mother Liquor Transfer Pipeline

Location: Jiangsu, China

Project Commissioning: 2013

Pipeline Length: More than 3,000 meters

Pipe Material: Steel-Lined Nylon Composite Pipe

Operating Temperature: 10–45°C

Media: Mother Liquor, Ammonia Mother Liquor, Hot & Cold Ammonia Mother Liquor, Semi-Mother Liquor

Project Background

The combined alkali production process transports highly corrosive mother liquor containing ammonia, chloride ions and alkaline components.

Before this project, the plant used 316L stainless steel seamless pipes, which experienced frequent corrosion at welded joints. Pipeline leakage caused repeated shutdowns, high maintenance costs and contamination risks due to iron ion release.

To improve corrosion resistance and reduce lifecycle costs, the plant decided to replace the existing stainless steel system with steel-lined nylon composite pipes throughout the mother liquor network.

Challenges

1. Highly Corrosive Process Media

Combined alkali mother liquor continuously attacks conventional metal pipelines.

Common problems included:

• Internal corrosion

• Weld corrosion

• Leakage

• Frequent replacement

2. Product Quality Requirements

Soda ash and ammonium chloride production require extremely low iron contamination.

Corroded metal pipes released iron ions into the process, negatively affecting product purity.

3. Short Service Life of Stainless Steel

Although 316L stainless steel offers better corrosion resistance than carbon steel, its welded joints became the weakest point.

Typical service life was less than one year before weld corrosion caused leakage.

4. Complex Operating Conditions

The project involved:

• Multiple mother liquor systems

• Different temperatures

• Various flow rates

• Long-distance pipelines

• Large diameter piping

The selected material needed excellent mechanical strength as well as long-term corrosion resistance.

Solution

After evaluating several pipe materials, the plant selected steel-lined nylon composite pipe for the complete mother liquor system.

The solution included:

• Mother Liquor I

• Mother Liquor II

• Cold Ammonia Mother Liquor I

• Hot Ammonia Mother Liquor I

• Ammonia Mother Liquor II

• Semi-Mother Liquor II

The new piping system gradually replaced the original stainless steel network.

For elbows, tees and other wear-prone locations, replaceable reinforced fittings were installed to simplify maintenance and reduce downtime.

Why Steel-Lined Nylon Composite Pipe?

One-Piece Nylon Lining

The internal nylon lining is manufactured as an integral layer without welding.

This eliminates one of the primary failure points found in stainless steel pipelines.

Excellent Corrosion Resistance

The nylon lining withstands continuous exposure to corrosive combined alkali mother liquor while preventing iron contamination of the process fluid.

High Structural Strength

The external carbon steel shell provides:

• High pressure resistance

• Excellent rigidity

• Long-distance pipeline capability

• Large diameter support (up to DN1200)

Long Service Life

Operating experience shows:

Pipeline Section	Service Life
Low-temperature mother liquor pipelines	Over 10 years
High-temperature pipelines	Approximately 9–10 years
Elbows and tees	Replace every 7–10 years
Straight pipe sections	No significant wear observed

Lower Lifecycle Cost

Compared with stainless steel pipelines, the steel-lined nylon system significantly reduces:

• Maintenance frequency

• Shutdown time

• Replacement costs

• Total ownership cost

Project Implementation Timeline

Date	Milestone
May 2013	Water commissioning completed
July 2013	Mother liquor trial production
December 2013	Full commercial operation

Operating Results

After more than ten years of industrial operation, the piping system has demonstrated excellent reliability.

Low-Temperature Pipelines

Mother Liquor II and Cold Ammonia Mother Liquor I have operated continuously for more than 10 years without leakage.

High-Temperature Pipelines

Mother Liquor I and Ammonia Mother Liquor II have achieved approximately 9 years of service life, requiring only scheduled replacement after long-term operation.

Wear Components

Only elbows and tees exposed to severe erosion require replacement every 7–10 years.

Straight pipe sections remain in good condition.

Comparison with Stainless Steel

Item	316L Stainless Steel	Steel-Lined Nylon Composite Pipe
Weld corrosion	Frequent	None (no internal welds)
Typical service life	Less than 1 year	More than 9–10 years
Iron contamination	Possible	No iron ion release
Maintenance frequency	High	Low
Lifecycle cost	High	Significantly lower

Technical Advantages

Corrosion-Free Nylon Lining

The seamless nylon liner eliminates internal weld corrosion and greatly extends pipeline life.

Wide Operating Temperature Range

Suitable for continuous operation between 10°C and 45°C, maintaining excellent mechanical properties throughout the process.

Large-Diameter Capability

Supports pipeline sizes up to DN1200, making it suitable for large-scale chemical plants.

Stable Product Quality

No iron ion contamination helps maintain the purity of soda ash and ammonium chloride products.

Easy Maintenance

Standardized elbows and tees can be replaced independently, reducing maintenance time and minimizing production interruptions.

Project Benefits

After replacing the original stainless steel pipeline system, the plant achieved:

• More than 10 years of proven industrial operation

• Significant reduction in pipeline leakage

• Lower maintenance costs

• Reduced production downtime

• Improved product quality

• Longer pipeline service life

• Lower total cost of ownership

Conclusion

This project demonstrates that steel-lined nylon composite pipe is a reliable alternative to stainless steel for highly corrosive combined alkali applications.

With over a decade of successful industrial operation, the solution has proven its ability to provide long-term corrosion resistance, stable production, reduced maintenance and lower lifecycle costs, making it an effective piping solution for modern soda ash and ammonium chloride plants.

Appendix

1. On-site pictures

2. User feedback