Introduction

While oil prices continue to climb, energy conservation remains the prime concern for many process industries. The challenge every process engineer is faced with is to seek answers to questions related to their process energy patterns. Energy and water efficiency can play a key role in a company’s drive to reduce its production cost and cut down on its waste treatment bills. How can a company achieve worthwhile reductions in energy consumption as well as effluent emissions? Good housekeeping, frequent preventive maintenance, and improvement of the utility systems are standard measures that must be implemented by all energy consuming processes. However, such measures could not provide a company with a clear competitive edge since the energy savings involved can often be marginal.

All of these questions and more can be answered with a full understanding of Pinch Technology and an awareness of the available tools for applying it in a practical way.

The term “Pinch Technology” was introduced by Linnhoff and Vredeveld to represent a new set of thermodynamically based methods that guarantee minimum energy levels in design of heat exchanger networks. Over the last two decades it has emerged as an unconventional development in process design and energy conservation. The term ‘Pinch Analysis’ is often used to represent the application of the tools and algorithms of Pinch Technology for studying industrial processes.

Basis of Pinch Analysis

Pinch originated in the petrochemical sector and is now being applied to solve a wide range of problems in mainstream chemical engineering. Wherever heating and cooling of process materials takes places there is a potential opportunity. Thus initial applications of the technology were found in projects relating to energy saving in industries as diverse as iron and steel, food and drink, textiles, paper and cardboard, cement, base chemicals, oil, refinary and petrochemicals. Early emphasis on energy conservation led to the misconception that conservation is the main area of application for pinch technology. The technology, when applied with imagination, can affect reactor design, separator design, and the overall process optimization in any plant. It has been applied to processing problems that go far beyond energy conservation. It has been employed to solve problems as diverse as improving effluent quality, reducing emissions, increasing product yield, debottlenecking, increasing throughput, and improving the flexibility and safety of the processes.

Since its commercial introduction, pinch technology has achieved an outstanding record of success in the design and retrofit of chemical manufacturing facilities. Documented results reported in the literature show that energy costs have been reduced by 15-40%, capacity debottlenecking achieved by 5-15% for retrofits, and capital cost reduction of 5-10% for new designs.

*A refinery manufacturing process uses large amount of utilities, including, heat and cooling water and electricity. Maximising efficiency of heat and cooling water utilization can result in significant monetary savings.

In a process system, it is possible to determine the maximum heating and coolant recovery potential through optimum heat and water cascading. The main objective of this research is to design and improve (retrofit) the refinery heat utilisation systems to achieve maximum practical heat and water recovery, which corresponds to the minimum utility* consumption. Thus, the first key step towards minimising utility consumption is to establish the minimum utility consumption targets (i.e. utility benchmarks) prior to the design or retrofit of a heat and cooling water recovery network through the notion of utility targeting.

Once the minimum utility targets has been established, the process systems will be retrofitted, guided by the benchmarks, towards maximising utility reduction, and hence, savings by considering options for elimination, reduction, reuse/recovery and regeneration of utilities.

Target

Specific Objective
  • To perform feasibility study of any opportunity for utility savings
  • To determine cold and hot stream enthalpy to indicate which unit has potential energy savings
  • To develop mass and heat balance based on process flow diagram with actual condition
  • To predict energy saving target by pinch analysis benchmark calculation
  • To make a preliminary assessment of the systems improvement and modifications
  • To evaluate economic analysis for plant improvement and project implementation
Specific results/output expected from this pre-study include:
  • Performance monitor for heating and cooling water consumption for client's refinery plant, in comparison to
    • The best-achievable performance based on client's operating performance history
    • The minimum utility targets based specifically on a predicted optimum recovery network scheme for the current client's plant
  • Overview of various strategies towards minimum utility design to include utility reduction, reuse and recycling.
  • Overview of An overall improved design of client's refinery process facility towards achieving the utility targets.
  • Overview of Preliminary economic indicators for the proposed design and improvement strategies to include the potential savings, estimated capital investment needs and simple payback period for investment.

A Proven Technique

Abroad, experiences of multinational petrochemical corporations like Shell, Exxon, BP, Dow, Mitsubishi, JGC and Union Carbide in Europe, USA and Japan have shown that Pinch Analysis has led to energy savings in the range of 15 – 95%, and capital savings of up to 30%. Locally, the potential for pinch application is tremendous. Results from preliminary feasibility studies conducted on a number of local process plants point towards substantial scope for savings as shown below:

Methodology

  1. Process Audit - Data collection and measurement
  2. Setting the minimum utility targets
  3. Process retrofit
  4. Economic Analysis – Savings and investment analysis

Thermal Processing Solutions to Improve Plant Performance

Our engineers have extensive knowledge of thermodynamics, heat transfer and fluid flow combined with the experience of providing solutions to hundreds of plants worldwide. In support of our proposals the company spends some 15% of turnover on research, and in particular develops, manufactures and supplies products to enhance heat transfer and reduce fouling.

Working now, in partnership with Process Integration Ltd, we can offer plant studies targeted at improving performance of whole network systems identifying improvement opportunities such as:

  • Enhancing heat recovery to reduce energy consumption to relieve furnace load
  • Increasing throughput where feed / effluent exchangers are limited on capacity
  • Reducing fouling associated with thermal degradation of temperature sensitive fluids e.g. crude oil, residues, polymers etc
  • Optimising performance of air cooled exchangers to maximize cooling and minimize fan power
  • Minimising size, weight, power consumption and maintenance of tubular heat exchangers using hiTRAN Performance  Enhancement Systems.
  • Overcoming the effects of mal-distribution in multiple bundle systems – stabilising performance of thermo-siphon reboilers at low flow, re-distribution of fluids where phase separation limits heat transfer
Looking beyond individual heat exchangers, Ingenious engineers are skilled in the evaluation of overall plant energy use and efficiency. This knowledge and real-world experience can rapidly identify critical performance limits and develop improved solutions.