Date of Graduation

5-2012

Document Type

Thesis

Degree Name

Bachelor of Science in Chemical Engineering

Degree Level

Undergraduate

Department

Chemical Engineering

Advisor/Mentor

Penney, William R.

Abstract

A major industrial water user in New Mexico discharges approximately 3.8 million gal of wastewater per day. The topology of the site provides an elevation difference of about 150 ft between the plant site and the entrance to the municipal sewage line; this flow and elevation difference is sufficient to produce about 40 kW of electrical power using a water turbine/electrical generator set to extract power from the flowing stream. This report includes designs and economic analyses for two distinct cases. One case is based on the written premises of the task; whereas, a second case is based on a real surrogate site, which is Intel’s Rio Rancho (near Albuquerque, NM) plant, which does discharge about 3.8 million gal per day and has about 120 ft of head available for power generation. After analyzing several turbine technologies, the Pelton wheel turbine was determined to be the most economical means for generating commercial electrical power. Pelton Wheel turbines operate most efficiently with a constant head and flow. Because the wastewater discharge for the task varies from 0.5 – 4 MM gal/day, an integrated study of the flow fluctuations determined that a surge tank of 27,000 gal was required to maintain a steady flow as input to the turbine. The task premises did not include any existing storage for the discharge stream; consequently, a 27,000 gal surge tank was provided for the task premises site. The surrogate site has a surge basin with a surface area of 17,000 ft2. This surface area requires only a 3 in level change to accommodate 27,000 gal of surge; consequently, no surge tank was included in the surrogate site case. The surge provides the turbine with a steady flow of 2,400 gpm and a constant head of 120 ft. The purchased turbine system selected by CREW has an overall (mechanical + electrical) efficiency of 68%. For the task premises scenario, 40 kW is produced, and for the surrogate site scenario, 30 kW is produced. The WERC task premises case is most economical with an IROR of 4.3%. This return is marginal for earnings projects under normal circumstances. However, interest rates are now at historically lower levels, and are projected to remain low for several years. The surrogate location IROR is about 2.4%, which is considered as a reasonable return for a minimal risk project with today’s economic environment. This energy recovery initiative is a “Green” project, which inherently lowers the acceptable IROR for environmentally conscious industries. This project will require about 12 months to complete once funds are available.

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