Author: Mike Watson, Managing Director, Tube Tech

Following a recent survey of refinery operators from across the world Tube Tech have compiled the Top 10 cleaning and inspection challenges faced by the refining industry.

As a world leading specialist industrial cleaning contractor Tube Tech have solved some of the refining and petrochemical sectors most difficult cleaning challenges. Tube Tech asked over 2500 refinery operators to complete their survey and the Top 10 cleaning and inspection challenges were developed as result of the survey feedback.

Below is THE most common cleaning and inspection challenge faced by the refining sector.

 

No 1       Fired Heater / Furnace / Charge Heater Convection Section Cleaning

Fired heaters / furnaces / charge heaters cannot operate effectively when fouled.

What might appear to be an insignificant 1mm layer of dust (both atmospheric and refractory) whether from fuel system impurities even decoke effluent it can lead to a decline in convection bank performance and thereby stack temperatures increase, leading to greater energy consumption.

Every known cleaning technique generally relies on a long hollow lance being fed through side access doors in order to deliver the cleaning medium whether air, water jets, dry ice or chemicals etc which will only ever clean what the operator can see or reach. This generally means only the top surface or underside of a single finned tube row is cleaned representing barely 2% of the entire 2500 square metre surface area leaving the majority untouched. Tube Tech offer a unique robotic convection section cleaning system which ensures near 100% surface contact of every finned or studded row in every bank. Inaccessible convection banks within fired heaters / furnaces / charge heaters etc and their correspondingly high stack temperatures are now a thing of the past.

 

Challenge

  • Approximately 60 feet long, convection banks contain nearly 2500 square meters of finned or studded surface area.
  • A manual lance operator can physically only reach 2% of total surface area with 98% remaining untouched and fouled.
  • Interestingly some fired heaters have zero access to the convection bank, while others have doors less than 150mm x 200mm.
  • Manual water jetting congeals refractory dust and forces combustion deposits down into the lower inaccessible rows, turning the paste into a concrete-like deposit that sits firmly between the finned tube rows reducing heat transfer.
  • Abrasive blast media not only erodes the tubes leaving a key way for deposit to build quicker but also blocks the finned space. All leading to increased future fouling rates and impossible to remove.
  • Soot blowers just remove “soot” within a narrow proximity as they are fixed and only apply air or vapour by moving in and out.
  • Foam cleaning relies on the dissolution of deposits with detergents and solvents and is appropriate for very light dust deposits without bridging. However whilst fouling is more prevalent on the underside and deep between rows of convection banks, foam is only ever administered from the top!
  • On-line chemical cleaning methods are often limited in effectiveness and known to create long term damage and generally struggle with hard deposits by relying on the updraft from flue gasses and have the limitation associated with manual lancing.

Solution

  • Robotic fired heater convection bank cleaning technology which solves the issues of poor or limited access to fired heater convection banks and also removes any type of deposit, whether hard or soft.
  • The robot acts as a delivery vehicle using one or two lances, capable of delivering a wide range of cleaning media from ultra high pressure water, ice, liquid nitrogen, steam etc. The choice of cleaning medium is dependent on the nature of the deposit.
  • The blast cleaning radius is delivered within a distance of one inch from the fouled surface systematically removing any and all deposits from between every tube row while providing 360 degree external tube surface contact, regardless square or triangular pitch and without refractory or fibre blanket damage.
  • The fired heater convection section cleaning robot is the worlds only technology to physically penetrate deep inside and between every row of finned or studded convection banks.
  • The robot is placed on top of each convection bank via existing access doors. New doors if required, can be cut in whilst the furnace is running prior to shut down, thereby removing this element from the shutdown period, reducing down time further. The door size can be as little as 150 mm x 200 mm and as large as 24 in².
  • The robot can either use one lance for cleaning and one for inspection – allowing inspection to follow immediately after to verify cleanliness without delay.
  • Two lances can be used for cleaning, resulting in twice the productivity per robot.
  • Productivity can be further enhanced and downtime reduced by the simultaneous deployment of multiple robots, at multiple levels reducing cleaning time to around 40 hours for a near 100% clean.
  • The robot is equipped with cameras allowing it to be remotely controlled from an operator external to the convection bank in which the robot has been placed. The lances are remotely activated and are pre-set to the technical drawings provided by the client, ensuring that each convection bank is cleaned at every level
  • Once cleaning is complete, the robot inspects and records the cleanliness for archive and benchmark purposes.
  • Regardless of whether the convection bank is square pitch or triangular pitch, the blast cleaning pressure emitted from the cleaning tips nozzles do not hit the refractory as their angle is such that they first deflect off the tubes first, where pressure is dissipated quickly. There is therefore no danger of refractory damage, as confirmed by Shell Global Solutions, worldwide independent consultants amongst others.
  • A shroud can be easily attached to the lance to provide plant operators with extra confidence that the high pressure blast medium such as liquid ice, CO2, water, etc., does not make contact with the refractory wall.

 

Conclusion

When selecting the cleaning method for a fired heater’s convection bank – it is crucial to consider the risk of cleaning failure, which is particularly high when the fouling is in the form of harder deposits. Should manual lancing technique fail, the operator will be forced to take the unit offline sooner, adding lost production to the cost of cleaning. Robotic fired heater convection section cleaning is extremely cost effective considering the improvement from an average of 2% surface coverage to near 100% surface area coverage.

Robotic fired heater convection section cleaning as developed by Tube Tech offers a unique and superior solution, delivering proven energy and multi million dollar financial savings in situations where conventional methods have struggled or failed and at a superior net present value.