Nanjing Chengzhi Clean Energy — MTO (2017) — Ethylene Liquefaction System for Methanol-to-Olefins Plant

Nanjing Chengzhi Clean Energy operates a coal-to-methanol-to-olefins (MTO) production chain, converting coal-derived methanol into ethylene and propylene — the two most widely used petrochemical building blocks. The MTO process catalytically converts methanol to a mixture of light olefins, which are then separated into polymer-grade ethylene and propylene through a series of distillation and refrigeration steps.

Client	Nanjing Chengzhi Clean Energy Co., Ltd.
Plant / Unit	MTO — Methanol-to-Olefins
Equipment	Ethylene Liquefaction System × 3
Design Code	GB
Cooling Capacity	1,848 kW per unit
Motor Power	800 kW, 220 kW (dual compressor configuration)
Refrigerant	Propylene (R1270)
Process Medium	Ethylene
Design Institute	China Chengda Engineering Co., Ltd.
Year	2017

Customer Background

Nanjing Chengzhi Clean Energy operates a coal-to-methanol-to-olefins (MTO) production chain, converting coal-derived methanol into ethylene and propylene — the two most widely used petrochemical building blocks. The MTO process catalytically converts methanol to a mixture of light olefins, which are then separated into polymer-grade ethylene and propylene through a series of distillation and refrigeration steps.

Ethylene liquefaction is the critical final step in the separation train. Gaseous ethylene from the distillation column overhead must be condensed to liquid at approximately −104 °C for storage and transportation. This requires deep refrigeration using a cascade system where propylene (R1270) provides the primary refrigerant cycle operating at temperatures low enough to condense ethylene.

MTO technology provides an alternative pathway to olefin production for regions with abundant coal resources but limited access to naphtha or ethane feedstock. The ethylene liquefaction systems are critical for converting the gaseous MTO product into a tradable, transportable liquid commodity that can be shipped to downstream polymer producers.

Challenges and Engineering Requirements

Process Temperature Control in petrochemical processing

Nanjing Chengzhi Clean Energy Co., Ltd. required precise low-temperature cooling for Ethylene Liquefaction System × 3 service in the petrochemical processing sector. The brine chiller system must maintain stable outlet temperatures within narrow tolerances despite variable process heat loads. Fluctuations in feed composition, ambient temperature swings, and seasonal load variations all affect the refrigeration duty — the system must respond to these changes while protecting compressor operation from surge and liquid carryover.

Refrigerant Selection and Safety

The choice of Propylene (R1270) reflects the balance between thermodynamic efficiency at the target evaporating temperature, compatibility with the plant’s existing refrigerant infrastructure, and safety classification under the applicable code. Each refrigerant brings specific considerations: flammability limits for hydrocarbon refrigerants, operating pressure ranges that affect component sizing, and oil miscibility that influences compressor lubrication system design.

Integration with EPC Engineering

The chiller packages were specified and documented by China Chengda Engineering Co., Ltd. as part of a larger process unit. This means every interface — brine supply/return connections, electrical load requirements, control signal protocols, and physical footprint — must match the EPC’s plot plan and P&ID exactly. Any deviation requires formal design change management, adding time and cost to the project.

Why Nanjing Chengzhi Clean Energy Co., Ltd. Selected Lmart

Integrated refrigeration package capability. Lmart designs and manufactures complete refrigeration systems — compressor selection, heat exchanger sizing, piping layout, control logic, and skid-frame engineering — as a single-source supplier. This eliminates the interface risks that arise when the chiller vendor, vessel fabricator, and system integrator are separate companies.

Process refrigerant experience. Lmart has delivered refrigeration packages using propylene, propane, ammonia, R134a, and other process refrigerants across petrochemical, chemical, and marine applications. This experience base means the engineering team understands the specific requirements of each refrigerant — safety classifications, oil management, capacity control methods — without a learning curve.

Repeat performance. Lmart has delivered equipment to Nanjing Chengzhi Clean Energy Co., Ltd. and similar clients in the petrochemical processing sector, demonstrating consistent quality and on-time delivery performance across multiple projects.

Technical Scope and Specifications

Three ethylene liquefaction systems, each rated at 1,848 kW, provide the refrigeration duty for the MTO plant’s ethylene product recovery section. Each system uses a dual-compressor configuration with an 800 kW main compressor and a 220 kW booster compressor, operating in a propylene cascade arrangement to achieve the deep temperatures required for ethylene condensation.

Key design features:

• High cooling capacity: At 1,848 kW per unit (5,544 kW total for three units), this is a substantial ethylene liquefaction installation reflecting the MTO plant’s significant ethylene production capacity
• Dual compressor cascade: The 800 kW and 220 kW compressors operate at different temperature levels in the propylene cascade, achieving the deep evaporating temperature required for ethylene condensation while maintaining acceptable compression ratios per stage
• Cryogenic service: Evaporator and ethylene-side equipment designed for operation at approximately −104 °C, requiring low-temperature impact-tested materials and specialized welding procedures
• Three-unit redundancy: The triple installation provides operational flexibility during maintenance and allows the plant to modulate ethylene production without shutting down the entire liquefaction section
• China Chengda Engineering design: Equipment engineered to Chengda’s specifications for integration with the MTO plant’s overall process control and safety systems

The combination of high capacity (1,848 kW), cryogenic temperature (−104 °C), and three-unit scope made this one of Lmart’s most significant ethylene liquefaction projects, demonstrating capability for large-scale coal chemical and MTO applications.

Delivery and Quality Assurance

All three ethylene liquefaction systems were factory-assembled and tested at Lmart’s Zhangjiagang facility. Cryogenic components underwent low-temperature impact testing per GB/T 229 to verify material toughness at the design minimum temperature of −104 °C. Pressure vessels were hydro-tested per GB 150, and all welded joints on cryogenic piping and equipment were subject to 100% radiographic examination.

Each system was shipped as a pre-assembled package to minimize on-site welding and hot work in the hazardous area. China Chengda Engineering’s specifications for documentation, including detailed operating procedures, maintenance schedules, and spare parts lists, were delivered alongside the physical equipment. The three-unit installation was commissioned as part of the MTO plant’s ethylene product recovery section, providing the full refrigeration duty for the plant’s ethylene output.

Results and Business Impact

Lmart successfully delivered 3 units of Ethylene Liquefaction System × 3 to Nanjing Chengzhi Clean Energy Co., Ltd., meeting the project’s quality, schedule, and documentation requirements. The equipment was manufactured to GB standards, with full documentation packages accepted by the client and applicable inspection authorities.

This project reinforces Lmart’s position as a qualified manufacturer for petrochemical processing applications, demonstrating the company’s ability to deliver equipment that meets international quality and certification standards.

Customer Voice

“The equipment was delivered on schedule and the documentation package was complete. The quality of fabrication met our inspection requirements.”

— Nanjing Chengzhi Clean Energy Co., Ltd. project team (paraphrased from project review)

Note: Lmart respects client confidentiality. Specific contact references are available upon request during the qualification process.