NICE3: New Energy-Saving Process for Recovering and Reusing Methanol

A joint cost-sharing grant program of:
U.S. Department of Energy's Office of Industrial Technologies and Office of Technical and Financial Assistance
U.S. Environmental Protection Agency's Office of Pollution Prevention

Produced by the National Renewable Energy Laboratory,
a laboratory of the U.S. Department of Energy
1000 Independence Ave., SW
Washington, DC 20586

Each year, approximately 436 million lb (198 million kg) of hazardous methanol waste are produced in the United States through the production and purification of many chemicals. Until June 1991, this methanol was disposed of by burning it as waste fuel in cement kilns. Recent environmental regulations stopped this method of hazardous waste disposal; it must now be burned in incinerators -- an expensive and energy-intensive process.

High methanol disposal costs, as well as increasing methanol production costs, have led the U.S. Department of Energy (DOE) and the U.S. Environmental Protection Agency (EPA) to work with FMC Corporation to find ways to recover and reuse methanol at FMC's hydrogen peroxide plant in Pasadena, Texas.

• Challenge: The process of purifying crude hydrogen peroxide requires a catalyst to remove any dissolved contaminants from the processing stream. Periodically, the catalyst must be regenerated to maintain its activity. One regeneration step for the catalyst involves a methanol wash and soak. During this process, methanol is contaminated with organic solvents, trace quantities of hydrogen peroxide, and metal cations.

• Solution: With the help of a $96,000 grant from the DOE- and EPA-sponsored NICE3 program in 1991, engineers at FMC Corporation's hydrogen peroxide plant investigated the use of a new method of steam distillation to recover the contaminated methanol by spraying steam directly into the distillation column. The new process allows 90% of the volume of methanol now used to be recovered and reused.

  Besides recovering a high percentage of methanol, the steam distillation technique allows for safer operation of the distillation column. In traditional distillation, steam or another heat source is indirectly applied through an external reboiler. In contrast, in direct steam distillation, the steam acts as a dilutant, preventing the buildup of undesirable quantities of hydrogen peroxide and metal cations in the bottom of the distillation column. As a result, two potential hazards are avoided:
  

  1. generation of oxygen from the decomposition of hydrogen peroxide by metal ions, which can lead to a methanol fire or explosion; and
     
  2. violent decomposition or detonation reactions catalyzed by the metal ions and activated by a high concentration of hydrogen peroxide in the bottom of the column.

  Construction of FMC's methanol recovery system began in the fall of 1991; it began operating in March 1992. To date, the system has greatly reduced the plant's waste methanol, resulting in significant energy and economic savings and a cleaner environment.

• Energy Savings: Based on the original projected efficiency of 90%, energy savings were estimated to be 19.2 billion Btu (20.3 trillion joules)/yr. Using the unit's actual recovery efficiency of 98.6% for 1992, the annual energy savings were 25.2 billion Btu (26.6 trillion joules).

• Environmental Benefits: At 98.6% efficiency, the unit is saving 1.93 million lb (877.000 kg)/yr of methanol. In 1992, the system recovered 276,104 gal (1.04 million liters) of methanol and saved another 502,080 gal (1.9 million liters) from being sent off site to an incinerator.

• Economic Savings: The methanol recovery system saved FMC more than $500,000 in annual operating expenses in 1992.

• Applications: The methanol recovery unit has allowed FMC to reduce its energy consumption, waste, and emissions, resulting in a better environment and an improved bottom line. Any industry with a waste methanol stream can apply this technology and take advantage of these same benefits.