15/12/2008

Waste management case study: industrial waste solutions from Braby

Paul Mayer, sales and marketing director at Braby, describes how Braby’s in-house design and project management team has collaborated with leaders in industry to develop chemical dosing test rigs to clean waste gas streams produced by waste-derived fuels.

The skid mounted, chemical dosing modular units have undergone trials at various plants across the country. The test rigs allow manufacturers and industries using waste-derived fuels to make sure waste gas stream outputs are clean, efficient and comply with the Waste Incineration Directive (WID) regulations.

Braby is one of the UK’s largest manufacturers of aluminium and stainless steel silos, tanks and processing equipment and has a manufacturing history of over 150 years. Founded in 1854, Braby led the way in the welding of aluminium and maintain their position as pioneers in industry, continually developing technology with the backing of a complete design and project management expertise.

With the extensive technical knowledge Braby posses, the company continually looks to develop new equipment and grow in new and existing industries. In 2007, Braby produced the first standard, low cost, fully ATEX compliant vacuum transfer and batch weighing package for the food industry. The Vacatex system met the DSEAR and ATEX 137 regulations for fire and explosion prevention in the workplace and was designed to assist small to medium companies meet new explosion prevention standards required by the regulations. Braby have seen a huge popularity for Vacatex and the system has been widely celebrated across the industrial press.

With Braby’s ambitions for further developments in industry technology, the company focused on the increasing use of waste-derived fuel within sectors using incinerators, such as waste incineration plants and the cement industry. These industries have a requirement to clean the waste gas streams of toxins produced during the incineration process and Braby had the technology to produce a system to meet these needs.

Objectives of the test rigs

The Waste Incineration Directive applies to most activities that involve burning waste, including burning waste for fuel. There are a large number of waste incinerators in England and Wales, ranging from small laboratory incinerators to large operations burning household waste. The directive also applies to co-incinerators, such as combustion plants and cement works which burn waste as a fuel.

Braby developed the chemical dosing test rigs to enable these varying operations to clean the waste gas streams produced from the incineration process. Braby endeavours to produce systems which enable businesses to operate within social and environmental requirements, but whilst also being able to maintain a profitable platform.

The test rigs are installed on a trial period basis at the plants. They are available for short term hire and handle a wide range of materials at various dosing rates, so each operation can determine which materials will produce the best results. The test rigs can be operated in manual mode, where rates per minute or hour are set, or alternatively the PLC control can adjust the feed rate as required, relative to gas monitor emission feed back.

The design process

Braby’s skid mounted modular units are designed to use chemical dosing to remove pollutants from waste gas streams. Braby are long term specialists in the storage, handling and dosing of materials and have developed several of the pioneering chemical dosing test rig projects to help solve waste problems experienced by industrial processes.

The use of compounds to remove pollutants from waste gas streams involves close collaboration with material manufacturers, environmental engineers and chemists. Compounds used in the test rigs have ranged from urea prills, dosed as a solid and mixed with ammonia; hydrated lime used to clean hydrogen chloride; activated carbon and coke dust.

Braby carried out tests of these material compounds to discover properties such as ease of flow discharging. The materials were also researched to assess the affect of temperature on the compound during movement within the airstream. Braby carried out these industry tests in the 3900 square metre testing facility at their Bristol-based production facility.

The chemical dosing test rigs on trial at a leading UK cement plant

Chemical dosing test rigs installed by Braby at a leading cement manufacturer utilise hydrated lime to reduce hydrogen chloride in the waste gas stream. After testing one of the rigs, the company purchased a fully integrated dosing plant and storage silo from Braby for one of its facilities.

The material used in the unit is a modified technical grade of lime powder, which produces a reaction at temperature in the waste gas stream. The process requires bulk storage and accurate dosing and conveying of the lime powder into the waste gas stream. The amount of lime powder dosed is strictly controlled by gas monitors within the emissions stack.

Monitoring probes within the stacks at the cement plant automatically monitor hydrogen chloride passing through in the waste gas stream. Signals within the installation then feed back information into the Braby system. The system monitors and controls the dosing of hydrated lime fed into the stack which is required for treating the hydrogen chloride.

The hydrated lime is fed into the stacks via a highly accurate duel dosing system. The main measurement of lime is combined with a fine dose to produce the accurate measurements demanded by the levels of hydrogen chloride in the process. The main dosing system provides the bulk of the lime, whilst the fine measures required for topping up levels to high accuracy are administered by the secondary dosing system.

When hydrated lime is dosed into the gas stacks, carbon dioxide produced by the lime reacts with hydrogen chloride in the gas stream to become a new compound, calcining. The resulting compound is a dust, removed further down the system in the filter area. The dust is stored and must eventually be disposed of in landfill. Accurate dosing within any installation is of great benefit to business - less waste is produced via the cleaned waste gas streams, which leads to lower costs.

The USP of Braby’s chemical dosing test rigs

The automatic monitoring system within the stacks follows the WID upper and lower bands of tolerance closely, producing a reaction time of around 30 seconds to changing conditions and chemical levels within the system. Many other systems within the market do not have this level of control over dosing. Instead they often feed in bulk amounts of the cleaning substance, in broad brush technique. This can however produce large waste outputs at the end of the process. Materials such as the hydrated lime dust are collected in filters and will need to be disposed of in landfill.

The cost of landfill is rising all the time and is hard hitting for industry. Whereas previously hydrated lime has been dosed in larger amounts to make sure all hydrogen chloride was neutralised, with the accurate dosing system in the Braby installation, material and disposal costs can be drastically reduced for industrial enterprise.

Conclusion

Balancing corporate environmental responsibility with enterprise profitability is top of industry priorities in the current economical and environmental climate. With these test units Braby can gain feedback and insight into how best to positively contribute to the environment, whilst remaining at the forefront of global manufacturing industry.

The success of Braby’s trial chemical dosing test rigs proves that industry can provide environmentally sound alternatives to landfill. Businesses can trial materials in their gas streams for effectiveness without having to undergo huge capital expense.
Supporting customers introduce new materials to their processes is a key part of Braby’s offering. Working in partnership with an organisation with the relevant technical and chemical experience gives customers reassurance that process changes they are using fully comply with EU regulations.