Unnecessary complexity also can afflict control systems. For example, when working up a design for additional processing capacity for a reactor effluent gas stream, the consulting process engineers noticed opportunities to simplify the existing control system.
Typically, the system for recovering byproduct from the reactor was viewed as having two separate procedures, reaction and compression, and was designed with separate control valves for each. As byproduct from the reactor made its way to the compressors that processed the end product, it first was cycled through an intermediate recovery unit where a dedicated valve controlled the pressure of the reactor. Downstream of that valve, another control valve on the compressor’s discharge recycle line regulated compressor suction pressure. In this configuration, the pressure was controlled on both sides of the control valve (Figure 3).
Viewing the two processes as one continuous system led to a straightforward solution — eliminating the upstream valve and controlling pressure only with one properly sized valve in the compressor’s discharge recycle line (Figure 4). This also allowed for a slightly smaller compressor that optimally handles a higher suction pressure and better controls the volume flow of the compressor feed stream. The change supported a continuous flow at a rate that met the increased capacity requirement.
Process simplification means change — and that can raise objections. People resist because they’re invested in the existing process, worry about the reliability of the new configuration, or even fear job losses.
Engineers experienced in simplification don’t dwell on criticizing the existing process, but instead focus on the benefits of the improvements and, when possible, how to implement them in a phased way if that better suits the situation.
A question that often arises during streamlining efforts is: “What if the line breaks down, then what?” When the solution stems from a holistic team-based approach, the ability to see the sound technical basis of simplification surfaces more readily. The notion that separate processes creating daily operational problems and frequent maintenance are more reliable than a single continuous process becomes moot, especially when engineers have experience with streamlining and can cite successful implementations.
Converting the brine feed process to a straightforward one required fewer pieces of equipment, increased the efficiency of the brine saturation process, and eliminated controller upsets and byproduct compressor trips. The higher byproduct recovery rate boosted the profit on its sale.
Similarly, eliminating the controller in the reactor process allowed for a smaller more-efficient compressor to regulate the feed stream volume in such a way that controlling pressure separately at both ends of the process wasn’t necessary; the simplification cut cost while raising production.
The aim of process simplification is to improve efficiency and achieve operating savings, not to eliminate jobs. Indeed, streamlining may enable redeploying staff to higher-value activities.
EMBRACE THE OPPORTUNITY
Succeeding at process simplification doesn’t demand “reinventing the wheel.” Rather, it requires focusing on how streamlining can improve a process. The KISS strategy can identify straightforward changes for enhancing the efficiency and profitability of a chemical process. Not every system will derive a huge gain from process simplification — but most can realize some benefits from adapting proven solutions.
Remember, as a process gets increasingly streamlined and simplified, so, too, do training and maintenance. As a result, further opportunities for improvement become easier to recognize.
RICHARD J. BEAMAN, P.E., is a Midland, Mich.-based senior chemical process engineer with the SSOE Group. ERIC HOPKINS, P.E., is a Cincinnati, Ohio-based senior chemical process engineer with SSOE. CLIFFORD REESE, P.E., is a Midland, Mich.-based business leader and senior associate with SSOE. E-mail them at Rick.Beaman@ssoe.com, Eric.Hopkins@ssoe.com and Cliff.Reese@ssoe.com.