The chemical characteristics of acetylene gas restrict its technical practicability, and the efficiency of industrial grade welding gas acetylene recovery is typically just 63% to 78%. Experiments by Praxair prove that the expense of purity recovery in purifying waste acetylene with impurities (phosphine >0.08%) by means of acetone absorption is up to $1.2 / cubic meter, 42% higher than producing new gas at a cost. The low-temperature separation technology of the German Linde Group has the capability of raising the acetylene recovery rate to 85% if the condition is -25°C, but equipment energy consumption equals 4.8kW·h/m³, therefore increasing the overall cost by 35%. The 2023 EU Environmental Protection Agency report indicated that the concentration of residual acetone in recovered acetylene must be controlled at <0.5g/m³ to meet the welding specification, but the mainstream technology at present is only capable of achieving 1.2-1.8g/m³, which means 28% of the recovered gas must undergo secondary treatment.
Economic analysis indicates that small-scale recycling is not economical. 3M estimates in 2024 show that recovery equipment with less than 50,000 cubic meters annual capacity will be priced at $2.3 /m³ a unit, while the new cost of gas buying is only $1.7 /m³. It will only be able to cut down the cost to $1.50 /m³ when the processing scale is over 200,000 cubic meters and could make a profit margin of 12%. China Baosteel Group’s practice case shows that its 4.8 million yuan self-investment in the recycling plant it constructed, annual processing volume of 180,000 cubic meters, by recycling gas consumed in cutting auxiliary process, replacing 23% of demand for new gas, the return on investment cycle is also 5.8 years. If smes use third-party recycling facilities, the cost of treatment is 0.8 US dollars per cubic meter, and the total cost is more than the new gas price by 9% after calculating transportation charges.
Regulatory obstacles contribute significantly to recycling applications. The EU EN 14620 regulation requires that the recovered acetylene for welding must be of purity ≥98.5%, but the actual yield of impurities (e.g., methane, CO) is in the range of ±1.2%, resulting in 32% of the batches being below the standard. In 2023, the US OSHA fine imposed on a Texas recycling plant illustrated that while because the concentration of phosphine in acetylene was above 0.003%, the same fine as high as $120,000 equated to 85% of the earnings for one month from the factory. Since the amendment of China’s Safety Technical Specification for dissolved acetylene in 2024, inspection intervals of recycled gas cylinder have been doubled from two years to once every half a year, and compliance expenses have increased by 18%, driving 15% of small-scale recycling companies in the Yangtze River Delta region out of operation.
Technology substitution effect is shown in actual application instances. After Toyota Motor brought hydrogen-oxygen cutting technology to Japan in 2024, the welding gas acetylene in the welding department fell by 41%, thus reducing the economic efficiency of the recycling program by 27%. By adjusting the gas ratio, Meyer Shipyard in Germany increased the peak of the mixing ratio of recycled acetylene and new gas from 30% to 45%, and the weld strength standard deviation decreased from ±8% to ±3.5%, but more dynamic gas mixing equipment was required, and the equipment investment increased by $220,000. Industrial statistics have shown that if the ratio of recycled gas is over 25%, the welding speed needs to be reduced by 12% to 15% so that quality remains consistent at the expense of a 9% increase in man-hour costs.
New technologies are surmounting recycling barriers. Sinopec’s announcement in 2025 of a plasma decomposition and reorganization technology, which is capable of burning waste acetylene into hydrogen and carbon at high temperature, i.e., 3000°C, then catalyzing new acetylene synthesis with purity as high as 99.2%, and whose energy cost reduces to $1.1/m³. Its demonstration project figures confirm that the 100,000 cubic meters/year processing capacity, 480 tons of CO2 equivalent carbon reduction benefits, through carbon trading can pay off 15% of the operating costs. The molecular sieve membrane separation apparatus developed by ABB at Switzerland increases the recovery rate of acetylene to 92%, the residual acetone concentration is driven to 0.3g/m³, and the volume of equipment is only 1/4 of the traditional apparatus, which is especially suitable for Marine welding conditions. However, the unit cost of such technology patent licensing fees still hovers between 18-22% over new gas prices, preventing bulk commercial applications.