How is Pinch technology different from other energy audits?
Pinch technology reveals all the possible savings and their corresponding financial benefits.
Results from 58 Pinch studies completed by American Process between 1995 - 2002
What really determines the steam consumed in a site?
In a mill site there is a small number of streams that determine the steam used on site. These can be characterized as "hot" and "cold" streams. "Hot" streams are those that must be cooled (e.g. extraction liquor) or that are available to be cooled (e.g. D1 effluent), while "cold" streams are those that need heat (e.g. weak black liquor evaporation).
Pinch analysis is based on identifying the "hot" streams and "cold" streams. For a complex pulp and paper mill with TMP, kraft and recycle operations and 3 paper machines, there will typically be a total of 100 significant hot and cold streams.
Having identified these streams, and using specialized methods for appropriate data extraction, these data are combined so that the whole process, plotted on a Temperature (T) vs. Heat flow (H) diagram, looks like a heat exchanger.
These curves are called the composites curves, or the hot and cold composites and they are a combination of the cooling and heating duties respectively.
In effect, this type of analysis examines which "hot"streams can be matched to "cold" streams via heat recovery. When the heat recovery is maximized the remaining thermal needs must be supplied by steam.
This minimum amount of absolutely necessary steam is the "target".
Using the composite curves we can identify:
So what is the significance of the Pinch temperature?
It is the temperature that defines heat distribution on the site and it is unique for each mill. Below the Pinch temperature there is always more heat than the process needs and above the Pinch temperature there is always less heat than the process needs.
Therefore, steam should not be used anywhere below the Pinch temperature since the mill already has an excess of heat below this temperature.
This and other guidelines of Pinch technology are used to clearly define the projects that are necessary in order to decrease steam usage.
We can save steam but do we always save money?
This is really the key question and the first that our application of Pinch technology defines. Not all the mill steam has the same value. The best example is given in the table below.
Swing steam is necessary for header pressure control and cannot be replaced through heat recovery. Steam generated by purchased fuels and let down through PRVs is more expensive than that extracted through the turbine. In turn steam extracted through the turbine is more expensive when it is generated from natural gas rather than from coal.
Pinch Technology - the Next Generation
It is clear that the emphasis of today's Pinch analysis lies in successfully applying thermodynamics so as to reveal the economic potential of the mill.
At American Process we have revolutionized the way Pinch analysis is applied to pulp and paper. Successive Design Methodology (SDM™) and Operational Pinch, (O-Pinch™), were developed as American Process Inc add-in methodologies to traditional Pinch technology. They are used to identify water savings opportunities (SDM™), and low or no capital cost projects, (O-Pinch™).
Using our data base of extensive Pinch analysis results we are able to identify the critical stream data, Pinch temperature and cross-Pinch grids in record time. Employing our feed-forward design algorithm we are able to produce multiple design grids quickly and accurately. Our field teams conduct the analysis on the mill site with on the spot layout and operability considerations.
The discipline and rigor of the detailed Pinch analysis is maintained throughout, but our experience and databanks allow unmatched performance in result delivery.
What this means is that we have the time to place the emphasis on analyzing the findings in terms of economics.
Economic analysis
In mills, projects get implemented if they meet predefined investment (payback) criteria or if they improve the payback of forced expansion or environmental expenditure. At American Process we analyze a matrix of grid configurations to optimize savings versus payback criteria.
Investment grids give concise information about which set of projects meets payback criteria within the capital budget allocation available.
Pinch Plus
2 great COMPANIES 1 great SOLUTION
American Process Inc. and TurboCare have allied to provide plant specific cogeneration and turbine analysis to pulp and paper mills.
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