Reactors are extensively used across many industry sectors and specifically pharmaceutical, chemical, food and fertiliser processing plants. They are designed to safely contain chemical reactions and/or thermal changes of ingredient substances in a pressurised environment, acting in a similar way to a pressure cooker in a domestic household kitchen.
If the substances used in the vessel are highly potent, toxic and of a particularly hazardous nature with aggressive chemical reaction affects, glass lined reactors are typically used rather than stainless steel reactors. A glass lined reactor has a hard wearing enamel surface coating on the wetted surfaces which provides high chemical resistance to the vessel – ideal for reactor applications.
After the reaction, the media inside the vessel is then discharged in a number of ways to a variety of subsequent operations including condensing, separation, distillation, evaporation and weighing/packaging. Ultimately the media is sent to a finishing process such as a tablet forming and packing machine or dispensed into bottles and containers for human consumption. In addition to obvious health issues, if the media is not reacted correctly inside the vessel then large amounts of time and money can be wasted by the subsequent process operations. Therefore, in-cycle reactor checking of the media to ensure the reactions are to the correct quality is the secret of a successful process.
Plant designers endeavour to ensure that the substances contained within the vessel react to the correct quality standard and at the highest efficiency. As with any process optimisation the first priority is to ensure safety and quality standards are not compromised. Then, plant designers must aim to produce the highest yield of product while spending the least amount of money to purchase and sustainably operate the reactors.
‘Sustainably operate’ is a key phrase. Above all the normal operating expenses such as energy input, energy removal, raw material costs and labour, is the issue of sustainable stakeholder safety is of paramount importance. Reactor risk management is all about expecting the unexpected and minimising human process intervention helps to mitigate risk and keep operations safe.
Probably the highest risk in the reactor process is taking a process media sample at elevated temperatures. This is major cause of concern for Pharmaceutical plants especially when taking the sample from a Reactor where the reaction is hazardous as found on practically all glass lined reactor applications. Spill over and exposure of sampling liquid is a perennial cause of batch rejection, reprocessing and various quality-related issues ultimately leading to personnel risk and lost profit.
Forward thinking plants are now standardising on reactor sampling systems which are designed to provide automatic vacuum-operated safe sampling.
In India, Standard Glass Lining Technology (SGLT) has sales and service branches located across the country as well overseas in Europe and the UK and are leading the way in this field with their innovative automated reactor sampling device. This device is offered as a value-adding option on their glass lined reactor supply, to ensure they provide their clients with best available practice solutions.
In operation, a pre-established sample quantity is directly pulled into the sampling container by vacuum in a closed-loop manner. At all times, the operator is safe, isolated from the media and in full control. The innovative design is optical sensor powered and is offered with a clear sampling pot so that the operator can see exactly what is happening to the reacted substances at all stages of the reaction process. Furthermore, Distributed Control System (DCS) operation is also possible with the auto sampler and unlike conventional systems, cleaning of the sampling pot is easy, fast and risk-free.
Given the potentially hazardous nature of the substances inside stainless steel, exotic alloy and glass lined reactors, SGLT’s safe auto sampler is now fitted as a site-wide standard by many leading international pharmaceutical manufacturing companies for both new build plants/extensions as well as retro fits to all existing their reactors.
Stainless Steel was invented in 1912 by Harry Brearley of the Brown-Firth research laboratory in Sheffield, UK, the home of Standard Glass Lining Technology’s (UK). Mr Brearley was looking for a corrosion-resistant alloy for gun barrels when he discovered and subsequently industrialised the martensitic stainless steel alloy. Since then, stainless steel has been adopted for containment of chemical processing because it has better chemical resistance than iron or mild steels and is widely available in the market place.
Misapplication of Stainless Steel
Stainless Steel is an inorganic chemical combination of essentially iron, chromium and nickel. Products manufactured from stainless steel are strong and their initial cost, though higher than iron or mild steel, is often less than other exotic metallurgical materials. However Stainless can be misapplied which results in processing problems as the material does not have sufficient properties to overcome chemical attack or the corrosive attack of biofilm components. Unfortunately, Stainless steel will corrode over time as the minor ingredients are lost and as electrochemical potentials arise which promote the oxidation of iron.
This is typically illustrated in stainless steel weldments where the iron is made more readily accessible to oxidation. Even the “mildest” of chemical conditions such as hot steam, the resulting rust (“rouging”) will then contaminate and compromise the quality of the products being produced in such equipment. This can have disastrous consequences for pharmaceutical plants processing expensive drugs and human consumption related substances.
Stainless steel can be chemically treated (passivated) to be made less reactive but this is a time consuming and expensive treatment that must be performed regularly to ensure that the iron in this material doesn’t oxidize (rust). The material can also be electro-polished but again this is expensive and can only ever be considered as a temporary improvement solution as electro-smoothing only miniaturizes the height of the asperities in the metallurgical surface and does little to remove the nooks and crannies surrounding the base of the asperities. Worse still, electro polishing can remove inclusions in the metal creating pits, which, in turn, can harbor microorganisms and biofilm components to perfectly shelter them from even the most vigorous cleaning.
Therefore in summary, no matter what treatment is made to stainless steel, unfortunately it is reactive to many harsh chemicals as encountered in chemical, pharmaceutical and biotechnology applications and therefore alternate chemical resistance solutions must be applied to processing equipment.
Alternative Chemical Resistant Materials
Some suppliers widely promote the use of Teflon or PTFE materials which have excellent chemical resistance properties. Unfortunately, like all plastics, their durability is a significant disadvantage as they are prone to surface scratching, mechanical deterioration and abrasion attack. However probably the greatest disadvantage is their inability to withstand temperature and pressure applications. For temperatures up to 100 degC, PTFE will expand over TEN times faster than Stainless Steel.
This means that the dimensional properties of the vessel, pipe or equipment will change significantly, creating a whole host of further problems with valves, seals and close fitting components. Over 100 deg C and the expansion is even worse and the PFTE material is generally not suitable for anything.
Advantages of Glass (Enamel) Lining
Glass Lined equipment provides an idealised technical solution for chemical and pharmaceutical processing applications. A glass coating is sprayed then thermally fused onto the surface of substrate material, typically steel, at high temperature in a repetitive process until the desired glass thickness is achieved. The substrate material provides high strength to the equipment whilst the glass lining provides significant physical and chemical advantages for the wetted surfaces.
These glass lined wetted surfaces are hard wearing and highly polished making them easy to sustainably clean with a whole range of substances including steam. This super hard, fine finish also makes glass lined equipment surfaces inherently good at avoiding cross contamination in batch processing applications and as the glass finish does not affect the flavour, colour or purity of contents of equipment, it provides a very versatile solution for high quality operations.
Arguably the greatest advantage of glass lined equipment is the very high corrosion resistance against inorganic acid, organic acid and organic solvents at different concentrations and temperatures. As a result, glass lined equipment such as Reactors, Receivers and Storage Tanks have won favour with many plant managers across the UK, Europe, India and USA as the vessels are robust, durable, hard wearing and physically strong, capable of handling a wide range of high pressures and temperatures.
Cost Effective Solution
Traditionally, high quality glass lined equipment for Indian pharmaceutical applications had to imported from suppliers in Europe and North America. This made the widespread use of glass lined equipment, specifically for bespoke equipment, in India, commercially restrictive. However, over the last 5 years with the introduction of Standard Glass Lining Technology Pvt. Ltd. based in Hyderabad, world class glass lined technology for ALL types of process equipment and associated components has become very affordable for the Indian domestic market.
Standard Glass Lining Technology is part of the Standard Group of Companies with primary manufacturing facilities of over 250,000sqft based in Hyderabad in over eight facilities, with technological innovation from the UK. The company therefore supplies a whole host of turnkey advantageous equipment designs from Valves to Reactors, Filters to Blenders and Barrier Isolators to Agitated Nutsche Filter Dryers (ANFD's), any of which can be offered with glass lined wetted surfaces.
The result is an affordable, superior performing glass lined product range, ideal for holistic chemical and pharmaceutical processes, which offers increased equipment durability, hardness and chemical resistance compared to other materials, delivered with exceptional customer service.