Evaluate a batch specialty chemical steam system for heat recovery opportunities and provide process design information for related utilities.
HEAT RECOVERY PROJECT FOR A BATCH SPECIALTY PRODUCTION PLANT
The ultimate client is a global specialty chemicals company that contracted indirectly with Process Engineering Associates, LLC (PROCESS) through an international engineering and consulting company, to evaluate the utility portions of an FEL2 design for an Alkoxylation surfactant manufacturing plant to be located in Europe. PROCESS was subcontracted to evaluate the steam system process design options; the client was to provide the air compressor and cooling tower designs, and project management.
The original scope of work for PROCESS was comprised of two primary tasks:
- Analysis of the process heating requirements realized by utilizing 18 bar steam purchased from an existing cogeneration turbine exhaust (without condensate return), and the resulting steam condensate generated. This included an analysis of the value of condensate heat recovery by adding feed preheating, and the implications to wastewater costs and process water reduction
- Sizing and design of a 20 bar steam boiler system as a replacement equivalent to the cogeneration exhaust steam.
Both tasks required PROCESS to provide equipment sizing, an equipment list, mass & energy balances, a process level Piping and Instrumentation Diagram (P&ID), and a process description.
The ultimate client subsequently re-evaluated the overall project economics, and scaled back the project objectives. PROCESS' revised scope of work was to evaluate a simplified process to reduce the consumption of purchased steam by implementing condensate heat recovery for feed preheating.
PROCESS' specific project tasks included:
- Design Basis - The design basis established for the project was taken directly from material and energy balance data supplied by the ultimate client.
- Conceptual Design - The existing batch Alkoxylation process utilized medium pressure (MP) steam to preheat the fatty alcohol reactants from 40 °C to 170 °C, and low pressure (LP) steam from the MP steam for reactor jacket heating. The proposed process modifications consisted of recovering heat from the MP condensate as LP flash steam and condensate, and utilizing both for feedstock preheating: Stage (1) with LP condensate, and Stage (2) with LP flash steam. This provided adequate feed preheating. Piping details were not included, e.g., heat exchanger bypasses. These would be necessary to accommodate imbalances in the generation and utilization rates of the LP flash steam due to the specific processing schedule for the various product batches.
- Calculation Procedure - A simplified heat exchanger network was developed and evaluated with a licensed computer simulation model to compare the Base Case (no heat recovery) to the Heat Recovery Case. The model used dodecanol and tetradecanol as model compounds for the long chain fatty acids.
- New Equipment - The new equipment for the proposed process modifications included (2) preheaters (plate and frame heat exchangers), flash vessel, condensate receiver, hot water receiver, condensate pump, and hot water pumps. These were sized and specified for maximum expected flowrates, and appropriate materials of construction.
Compared to the Base Case, the maximum projected steam consumption for the Heat Recovery Case decreased by 24% (2,000 kg/hr). This translated into a calculated projected maximum savings of steam costs. Three PFD’s depicting the proposed process modifications were generated.
- Specialty Chemicals Manufacturing
- Steam systems evaluation and optimization
- Heat recovery and energy minimization
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