Change Process Checklists

11.09.2014 0

Leading change and getting others to be engaged and enthusiastic about upcoming changes can often be very difficult.

The way to implement change is different for every engineer, however there are some key steps which should always be done, regardless of your skill and style.

Due to the vast number of projects I always seem to be working on I find it extremely helpful to formalize the change management process into a checklist document.

This is an example of the kind of change procedures that you should consider using in your own perosnal change management checklist:

Update maintenance strategy
Update operating strategies
Update tagout/lockout systems
Complete change request documentation
Develop business case
Complete commissioning
Update control system graphics
Send out communication

After all these processes have been completed it is always useful to get another person to check your work – this could be a senior engineer or coworker.

Increase Chemical Plant Profitability – Part 3 – Production

07.09.2014 0

This is Part 3 of the How to Increase Chemical Plant Profitability series.

One of the most popular methods to increase plant profitability is to increase the production capacity of the site without using any additional equipment. This method is most common amongst production of commodities where the sale of the product is almost guaranteed.

This works in two ways:

  1. Direct increase in profit from increased quantity of sales
  2. Efficiency increase through dilution of fixed losses

The first part is fairly self explanatory, so I won’t dwell on that but part two only works without replicating existing production lines.

Focusing on energy efficiency fixed losses are based on temperature (which is generally controlled) and surface area of the vessels (which are fixed). So by increasing flow through the circuit the heat losses remain the same. This means that profitability can be increased by improving energy efficiency through increased flow/production.

production_dilutes_fixed_losses(1)

 

But heat losses are only one of the expenses that can be diluted out through increased production. If the increased production can be done without needing to hire additional people then the total site labour costs can also be diluted out. Anything from energy, to labour, and maintenance costs can be reduced per tonne is this manner.

The actual method of how to increase production is incredibly subjective and cannot be explored in any detail in this general article, but the theory is to identify and eliminate any bottlenecks. This can include anything including:

  • Pumping capacity
  • Storage capacity
  • Customer requirements
  • Ability to hit control setpoints
  • Any equipment capability
  • Labour requirements
  • Maintenance speed
  • Breakdown frequency

The idea behind this method of improving site profitability is fairly easy to grasp so it doesn’t need much detail but the actual execution can be very difficult and time consuming.

 

 

Pulp and Paper Production – The Kraft Process Overview

30.01.2013 0

The kraft process is a process for creating wood pulp out of wood, for use in paper production. Unlike many other chemical engineering processes, the kraft process is not named after its inventor, but instead derived from the German word kraft, meaning “strong.”

This name was chosen by the inventor of the process himself, Carl Ferdinand Dahl, who intended to market the superior strength of the paper created from this process.

A resident of Danzig, Kingdom of Prussia (present-day Germany), Dahl invented the process in 1879, and had himself awarded a U.S. patent for the invention on April 15, 1884. His invention was first put into action when a pulp mill in Sweden first began using it in 1890.

Pulp and Paper MillThe kraft process has undergone significant improvements throughout the century, especially since the invention of the recovery boiler during the early 1930s by G.H. Tomlinson. The innovation helped it surpass the sulfite process, another pulp-making process, in usage and catapulted it to the widespread popularity that it enjoys today.

The kraft process begins with presteaming common wood chips. This involves collecting wood chips that are 12–25 millimeters (0.47–0.98 inches) in length and 2–10 mm (0.079–0.39 in) in width, and wetting them before heating with steam. This causes cavities within the wood chips to be filled with both air and moisture.

After this, the wood chips are impregnated with white and weak black liquor by heating up to 100 °C (212 °F). During this process, liquor penetrates the capillary structure of the wood chips, and saturates them homogeneously throughout.

White liquor, so-named because of its white opaque color, is a strongly alkaline, aqueous solution of sodium sulfide (Na2S), sodium hydroxide (NaOH), sodium carbonate (Na2CO3), sodium sulfate (Na2SO4), sodium thiosulfate (Na2S2O3), sodium chloride (NaCl), calcium carbonate (CaCO3) and water. However, only the first two (and to a lesser extent, the third) compounds actually contribute to the breakage of extractives–cellulose fiber bonds; the other components of white liquor are considered to be chemically inert.

Black liquor, on the other hand, is simply the residue created from the consumption of white liquor during the previous batches of the kraft process. Black liquor is thus a mixture of woodchip residues in white liquor. Aside from being used as a digesting agent during the early stages of the kraft process, black liquor is also combusted in the recovery burner in order to recover useful compounds from the black liquor and generate extra power for the pulp mill.

The rationale for recycling spent white liquor is pretty simple: economy. Not all of the active components of white liquor are spent up during digestion, and disposing them right after just one use is fiscally imprudent and environmentally irresponsible as well. Black liquor is, as its name suggests, a viscous, aqueous, black liquid that turns water to dark caramel upon contamination, and is very toxic to aquatic life. About 7 tons of black liquor is produced for every 1 ton of pulp manufactured under the kraft process. Recycling black liquor (i.e. spent-up white liquor) greatly reduces the amount of it that goes into our ecosystem.

During digestion, the wood chip–liquor mixture is placed into a highly pressurized vat for several hours at temperatures ranging from 170 to 176 °C (338 to 349 °F). The liquor mixture act to digest the pulpwood into paper pulp by removing lignin (a complex chemical compound found in the wood’s secondary cell wall), hemicellulose (a polymer also found in the cell wall) and other extractives. This is done in order the pulpwood cellulose fibers that are used as ingredient in making paper. Reactions between nucleophilic bisulfide (HS-) or sulfide (S2-) and the woodchip components underpin this step of the kraft process.

Digestion produces a solid pulp known as a “brown stock.” This product is then collected and washed to rid it off the inorganic compounds that came from liquor impregnation. Atmospheric pressure is reduced in the containers in order to let steam arise from the brown stock, and cool them down. Efficiently designed pulp mills recycle this steam to turbines in order to generate electrical power.

Afterwards, the pulp is passed through sieves in order to remove dirt and other unwanted contaminants; and then washed again for several times in order to produce a final product that is clean pulp. Finally, the pulp is bleached to give it paper’s familiar white color. Several chemicals may be added after this process in order to improve the quality of the pulp.

The kraft process produces a lot of by-products, the most notable of them being crude sulfate turpentine and tall oil soap. Both of which can be used as ingredients of a wide range of retail and industrial products, including lubricants, soaps, solvents, inks, binders and many more. Effluent produced by kraft-process pulp mills are extremely detrimental to the environment and should be recycled whenever possible.