Design a custom 3-phase heat exchanger and separation system.
The client operates a waste-to-energy pilot facility with a reactor and heat exchanger. It had been determined that the existing heat exchanger was not adequate to meet the anticipated demands of the process. Process Engineering Associates, LLC (PROCESS) was contracted to evaluate and specify the parameters of a heat exchanger system that could handle the required range of conditions specified by the client.
To support this system redesign concept, PROCESS was tasked to complete the following general items:
- Develop a heat exchanger design model that addressed the novel requirement that heat is released in the heat exchanger system. This heat release is due to the heat of reaction of process constituents formed as the gas temperature is reduced.
- Incorporate a method in the design to remove condensables (water, HCl, organics) and metals. Such tasks resulted in designing a 3-phase heat exchanger (in series) with collection pots to allow the removed / condensed gases to be examined at three different temperature cuts. Furthermore, gas-liquid separators with removable chevron type mist eliminators were also specified as required within the exchanger system. Since solids (carbon and metals) are expected to be removed in the exchangers, each vessel (collection chamber) was specified to have a water flush nozzle and cleanout door.
- Construct a flow diagram for the proposed heat exchanger system including the proposed instrumentation and control for the system. The process control concept for each heat exchanger included controlling the off-gas temperature for each exchanger by manipulating the flow of the cooling water to the shell side of each heat exchanger. The control concept also included an automatic liquid level control for the liquid collector and gas-liquid separators. Furthermore, temperature indication on the exit cooling water streams for each heat exchanger was included in the design. Flow indication on the reactor gas was also included.
- Incorporate non-instrument equipment as required. Though not part of instrumentation directly, process safety valves were considered on the cooling water for each heat exchanger to prevent overpressure during the potential steam generation scenario. In addition, a back-pressure regulator was considered on the cooling water return line to maintain the cooling water system pressure below its bubble point.
- Heat transfer modeling
- Heat exchanger design