Methanol (nitrogen-methanol or pure methanol dripping) is one of the most commonly used carrier gas sources for controlled atmosphere heat treatment in China. However, methanol is a flammable, toxic and dangerous chemical, which requires high costs for storage, transportation, fire protection, environmental impact assessment and personnel management, and fluctuations in cracking components in the furnace will affect carbon potential control. Replacing methanol with centralized gas supply from an endothermic gas generator can simultaneously reduce the risk of hazardous chemicals and improve atmosphere stability. Modifications require assessment of gas consumption, piping, safety interlocks and re-validation of the process.
- Methanol problems: flammable and toxic, high storage and environmental impact assessment costs, volatile ingredients
- Alternatives: Centralized gas supply from endothermic gas generators; nitrogen-based atmosphere can be used for some processes
- Benefits: Reduce the risk of hazardous chemicals, make the atmosphere more stable, and reduce methanol purchases
- Steps: Assessment → Design → Installation → Switchover → Process Validation
- Layer depth, hardness and texture must be re-verified after switching
Why consider replacing methanol
Security and Compliance - Methanol is flammable and toxic, and storage tanks and delivery systems need to comply with hazardous chemicals management requirements; - Ongoing costs for fire protection, leak detection, personnel training and emergency response plans; - Environmental impact assessment and safety assessment have strict review on methanol reserves and use.
quality - Methanol is cracked in the furnace, the degree is affected by temperature and furnace type, and the CO content fluctuates; - In the case of the nitrogen-methanol integral-quench furnace monitored by Gauss Control, CO fluctuates between approximately 19%–22%, resulting in a carbon potential deviation of approximately ±0.12.
cost - Methanol price fluctuations; - Store and manage hidden costs.
Gauss Control Fine Wire/Steel Pipe Industry Page also pointed out that one of the biggest challenges for special steel manufacturers comes from the safety control and environmental impact assessment of protective atmosphere media, such as the management costs of methanol storage and use.
Alternative
| Plan | Applicable | Description |
|---|---|---|
| endothermic gas generator centralized air supply | Carburizing, quenching and heating, multi-furnace workshop | Stable composition, no methanol storage, gas and generator investment required |
| endothermic gas generator + small amount of enriched gas | Carburizing | Enriched gas with natural gas or propane |
| Nitrogen hydrogen/dissociated ammonia | bright annealing | A process that does not require carbon potential |
| Keep methanol as emergency backup | transition period | Reduce the reserve as a backup during generator maintenance |
Transformation steps
- Current situation assessment: Furnace list, methanol consumption of each furnace, process type, furnace conditions;
- Gas consumption calculation: Determine the generator capacity and number (see generator selection);
- System design: Generator location, pipe network, branch metering, safety interlocking;
- Installation and debugging: Generator acceptance, pipe network pressure and leakage testing;
- Switching in batches: Switch some furnaces first, verify and then expand;
- Process validation: Make furnace samples for each process to verify layer depth, surface carbon, hardness and structure;
- File update: Process card, control plan, FMEA, operating procedures.
Risks and Countermeasures
| Risk | Countermeasures |
|---|---|
| Generator failure leading to gas outage | Double furnace or multiple redundant units, or reserve emergency air source |
| Changes in penetration rate after switching | Adjust carbon potential or time and re-verify |
| Insufficient pressure at the end of the pipe network | Check during design and increase pipe diameter if necessary |
| Personnel unfamiliar with the generator | Training and maintenance services |
Frequently asked questions
Is nitrogen still needed after all methanol is replaced?
Nitrogen is still needed for safety purges and parts of the process, but the amount is usually reduced.
Can production not be stopped during the renovation?
By switching in batches and properly arranging furnace shutdown windows, this can usually be accomplished without a complete shutdown of production.
Is it worth replacing only one or two furnaces in a small workshop?
Accounts need to be settled. Generators with low usage have a longer investment payback period, but if the pressure on hazardous chemicals management is high, small generators are also an option.