(60at) A Novel Approach of Converting Industrial Wastewater into Energy

Many industries use complex production processes that result in high-strength, hard-to-treat wastewaters. Examples include oil and gas refining, petrochemicals, and pharmaceuticals. Their wastewaters may vary in composition, but they typically have at least one of these problematic characteristics: high levels of biorefractory compounds; toxic compounds; halogenated organics; and aromatic or aliphatic hydrocarbons.

In addition, their chemical oxygen demand (COD) levels can range widely, up to 300,000 mg/l. On top of that, some process waters/wastewaters have high salt levels, especially chlorides, requiring expensive materials of construction, making cost-effective treatment especially challenging.

Existing treatment solutions for these high-salt wastewater streams are typically incineration or gasification. The former combusts the wastewater completely in the presence of excess oxygen at 1,100°C (2,012°F), producing carbon dioxide, water, and salts. The latter burns the wastewater using stoichiometric oxygen to produce carbon monoxide and lesser amounts of hydrogen. In turn, these gases can be processed into more useful fuel gases. Unfortunately, both processes are expensive, especially their energy costs. Also, high-temperature processes can be expensive to maintain, requiring backup units that consume capital, operating expenses, labor, and space.

Given these challenges, this presentation will focus on hydrothermal gasification to handle wastewaters that cannot be economically treated with other oxidation technologies. It uses a heterogeneous catalyst to spur reactions similar to those that typically occur in steam reforming and gasification. These reactions occur in an aqueous phase, so temperatures are much lower than what gas-phase gasification processes require. This paper will provide data on treatment for organics and chlorides; propylene oxide/styrene monomer (PO/SM) wastewaters; produced waters containing kinetic hydrate inhibitors (KHI); and propylene glycol wastewaters.

The benefits of catalytic gasification will be explained. They include fuel-gas production, providing data of gas composition for different types of compounds treated; high COD destruction rates, helping reduce downstream treatment costs; capital and energy savings, due to a lower-temperature process; and saving space, relative to other oxidation treatment approaches.