This video documents an ambitious project to build a large-scale, homemade liquid nitrogen generator capable of producing and storing up to 100 liters. Motivated by the prohibitive cost of commercial systems (over $24,000) and the need for a reliable supply for future experiments, the creator sources and assembles the necessary components. The build centers around three key parts acquired as high-risk purchases from eBay: a membrane nitrogen generator, a powerful cryocooler originally for an MRI machine, and a 30-year-old, 100L liquid helium dewar. The video details the significant financial investment (nearly $17,000), the technical challenges of setting up a powerful external compressor, and the process of individually testing each component. The initial system successfully produces liquid nitrogen at a rate of 14 L/day but is plagued by impurity issues and a slow extraction process. After a month of significant upgrades, including a vastly larger nitrogen generator, the final system achieves a production rate of over 1 L/hour (24 L/day) of high-purity liquid nitrogen, outperforming its commercial counterparts and fulfilling the creator's goal.
Building a High-Capacity Liquid Nitrogen Generator from Scratch
0:00 Motivation and Goal: The creator sets out to build a large-scale liquid nitrogen generator to support future projects, as commercial systems are prohibitively expensive (upwards of $24,000). The goal is a system that can produce and store up to 100 liters.
3:35 The Three Core Components: The plan involves sourcing three main parts: a membrane nitrogen generator to separate nitrogen from air, a powerful cryocooler to liquefy the gas, and a large insulated dewar for collection and storage.
5:46 Sourcing High-Risk Components: The creator purchases the key components from eBay, taking significant risks. This includes a brand-new $5,600 cryocooler from a seller with no feedback, a 30-year-old $1,100 liquid helium dewar with no guarantee, and an unexpectedly necessary $10,000 external compressor. The total project cost rises to nearly $17,000.
18:33 Component Testing and Success: After significant setup, including re-pressurizing the system with helium and configuring a water chiller, the cryocooler and compressor are tested. After a long wait, the system successfully produces liquid air, confirming it can reach the required temperatures for making liquid nitrogen.
28:38 Dewar Proven Functional: The 30-year-old dewar is tested and proves to be in excellent condition, capable of holding a strong vacuum in its insulating jacket without any leaks, which is crucial for holding cryogenic liquids.
36:01 First System Run: The entire system is assembled. After purging with pure nitrogen from the membrane generator, the system is turned on. After several hours of cooling the massive dewar, it begins to produce liquid nitrogen.
40:05 Initial Performance and Flaws: The first run produces about 30 liters of liquid nitrogen at a rate of approximately 14 L/day. However, the nitrogen generator is undersized, leading to contamination with oxygen and water, and the extraction process via a siphon tube is extremely slow.
47:30 Major Upgrades for Peak Performance: Dissatisfied with the initial results, the creator spends a month upgrading the system. A new, massive nitrogen generator is built (providing 7x the capacity), and the extraction system is improved.
47:50 Final Results and Future Plans: The upgraded generator dramatically improves performance, producing over 1 L/hour (>24 L/day) of crystal-clear, high-purity liquid nitrogen. The creator successfully collects nearly 100 liters, fulfilling the project's ambitious goals and enabling a reliable supply for future experiments, such as turning air into alcohol and recreating a superconductor demonstration.