Perform an engineering evaluation of alternatives for the recovery of steam condensate at an edible oil manufacturing facility.
CONDENSATE RECOVERY SYSTEM ALTERNATIVES EVALUATION
The client, an edible oil manufacturing facility, contracted with Process Engineering Associates, LLC (PROCESS) to provide process engineering services in the technical and economic evaluation of alternatives for recovery of the plant condensate. The project included a detailed review of potential alternatives to determine technical feasibility and then an economic comparison of the technically feasible options to determine which option(s) would be the best to carry further into front-end engineering design. Alternatives that were technically reviewed included the following:
- Returning the condensate directly to the deaerator (DA) tank (with and without a guard filter)
- Returning the condensate to the DA tank and installation of a reverse osmosis (RO) system on the makeup water
- Additional preheat of boiler makeup water using a new heat exchanger (the boiler makeup water was already being preheated in two stages using the boiler blowdown and stack gas economizer).
All three options were considered technically feasible for this application. Returning condensate to the DA tank involved consideration of the fact that oil carryover to the condensate could occur if there was a compromise in the upstream plant process equipment. A system would need to be designed to either remove the oil to an allowable concentration level in the boiler feed or to detect the presence of oil and divert the condensate to the sewer. PROCESS evaluated equipment options for both scenarios. The following tasks were executed to complete the scope of the project:
- Generated as-built piping and instrumentation diagrams (P&IDs) of the existing condensate collection system from the process discharges to the boiler feed system.
- Developed a heat and material balance and process flow diagram for the existing system operation as well as each alternative. This information was used to determine the technical feasibility of the options; and to the potential changes in energy consumption (natural gas and electricity), makeup water usage, and wastewater generation.
- Estimated the estimated total installed costs (TIC) for each option (budget level). This involved gathering actual budget pricing from equipment vendors for all major pieces of process equipment and using a factored based cost estimating spreadsheet to generate the TIC.
- Estimated the annual operating cost savings for each option. Actual utility, raw material, and waste disposal costs provided by the client were used to generate an annual operating cost savings and/or increases associated with the changes in fuel usage, makeup water usage, and wastewater disposal.
- Evaluation of alternatives for detection and/or elimination of oil in the condensate before it is returned to the DA tank. Turbidity monitors and total organic carbon (TOC) analyzers were evaluated for technical feasibility in the process and both were applicable. The turbidity monitor required the collection of operating data for a period of time in order to develop a correlation between oil concentration and turbidity in the condensate. The client already had some of this data available and a straight line correlation was apparent. Typical guard filters or water polishing systems (standard carbon beds, oil filters) had design temperature limits below the actual operating temperature of the system. Pricing was obtained for non-standard maximum condensate temperature.
- Marked up existing P&IDs for the selected option to define piping and instrumentation modifications.
Returning the condensate to the existing DA tank with controls in place to detect oil in the system was selected as the most cost effective alternative (payback of less than 2 years even if the condensate is diverted a quarter of the time). The client elected to move forward with front-end engineering design on this alternative.
- Food Manufacturing
- Process alternatives evaluation