SMART Explosion. Efficient Boiler Cleaning with Explosion Generators

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1 SMART Explosion Efficient Boiler Cleaning with Explosion Generators

2 Problem and Solution The use of solid fuels, such as coal, waste or biomass, is liable to intense fouling of the steam generator heating surfaces within a very short operating period if no continuous cleaning is performed. This affects the operation of the power plant in multiple ways: reduction of heat transfer across the heat exchangers and hence, poor efficiency of the power plant overall; progressive build-up of ash deposits, influencing plant s availability and working capacity; increased pressure loss in flue gas path, driving up power demand of the ID fans; risk of major ash deposits coming loose and dropping down, damaging the boiler; As a result, on-load cleaning systems must satisfy many requirements and play an exceedingly important role for an efficient boiler operation. Key demands include the following: high efficiency of the cleaning performance; reliable and safe automatic operation; low operating cost; no damage to heating surfaces; suitability for new plants and retrofits alike; broad application range for different fuels and boiler types; low space requirement; operation area where access is limited. Our Solution Generally, the focus is to find the optimum solution for the customer-specific cleaning problems. One method of resolving the issue - especially where access to the operation area is limited or space requirements are low - consists in boiler cleaning by means of controlled explosions. Each explosion induces vibrations into the heating surfaces, thereby removing fouling. By carrying out this operation within suitably short time intervals (e.g., once per hour), the build-up of ash deposits is avoided altogether.

3 Dosing tanks 1 2 O 2 CH 4 Gas spring (N 2 ) Piston Combustion chamber Bleed-off valves Boiler wall Glow plug 3 4 Discharge nozzle The Solution: SMART Explosion System s Principle SMART Explosion provides an efficient solution to the problem mentioned above. Unlike manual explosion cleaning, the system removes fouling from heating surfaces automatically in a continuous cycle using permanently installed explosion generators. Thus, the formation of ash deposits is prevented from the very beginning. Upon the enabling signal by PLC the dosing tanks are filled with the necessary small amounts of natural gas and oxygen to the preset pressure level. At this point the two gases are still fully separated from each other, i.e., they are not explosive. The free-moving piston shuts off the discharge opening, creating a gas-tight seal. The solenoid transfer valves for natural gas and oxygen are opened and allow both gases to flow into the combustion chamber where they now form an combustible mixture. The glow plug is activated and generates the explosion. Under the sudden pressure rise to approx. 350 bar in the combustion chamber, the piston shoots back and clears the discharge opening. The pressure wave is directed through the discharge nozzle into the boiler where it spreads in a linear and then spherical pattern. Once the pressure wave has left the explosion generator the piston is pressed against the discharge opening by nitrogen pressure to close it again. The generator is now ready for the next cycle. The explosion pressure wave induces short vibrations similar to those produced by a rapping system in the walls and tube bundles. Dust and accretions of foreign matter are thus removed. In case of a 2-side installation, the penetration depth and cleaning effect can be expected to extend to 15 meters. Optimum cleaning action is achieved with boiler tubes which are free to vibrate. The explosion generators are made of particularly pressure and heat-resistant materials and equipped with high-grade components. Each explosion generator is tested for operation prior to dispatch.

4 System Components Explosion Generator The explosion generator is typically mounted with its discharge nozzle extending in a horizontal direction. However, vertical installation on the boiler is likewise an option. The unit is fitted movably on a rail and is held in place via a spring mount or by direct attachment to the flange (DN125 PN16 for EG10 and EG 10L; DN200 PN6 for EG10XL) provided by the customer. The spring action prevents the explosion generator s recoil from being transmitted directly to the boiler wall. The discharge nozzle extends through the boiler wall and projects approx. 50 mm into the boiler in home position. Gas Supply The gas supply for the explosion generator is commonly obtained from individual gas cylinders or mini-bundles delivering up to 200 bar. The pipes to the generator are designed for a line pressure of 40 bar. For natural gas supply it is also possible to use a small compressor if central gas supply is available. In addition, a single nitrogen cylinder will be required for the gas spring on the generator s piston. Control SMART Explosion is controlled via single or multiple control panels each equipped with a PLC and touchscreen-hmi. For the exchange of data with the DCS system and with the manufacturer of the generator, various solutions are available. Comparison EG10 / EG10L / EG10XL At present three generator types (EG10, EG10L and EG10XL) are available. The design of the generators is nearly identical. Different cleaning results can be achieved by using larger combustion chamber and adapting them to the specific application. Technical Data Volume combustion chamber (l) EG10 EG10L EG10XL Dosing system Predosing Predosing Predosing Dosing cylinders filling pressure (bar) Combustion chamber filling pressure (bar) ca. 29 ca. 32 ca Gas consumption per 16 / 34 / 1 22 / 48 / 1 28 / 61 / 1 explosion (g, ca.), CH 4 or natural gas / O 2 / N 2 Compressed air consumption (6 bar) (Nm 3 /h) for 1 Explosion generator and per additional explosion/h Sealing/cooling air consumption (>20 mbar) (Nm 3 /h), if flue gas temperature > 700 C and /or if the boiler is operated at positive pressure Sound level, average 8h/ peak (dba) 3 (+0.2/ EP) 3 (+0.27EP) 7 (0.2/EP) < 80/120 < 80/120 < 80/120 Installation flange (DN) Weight (kg)

5 Applications Fields of Use More than 300 SMART Explosion systems are in successful operation in many countries. They can be used for cleaning almost any type of boiler or process equipment such as waste incinerators and biomass-fired boilers; industrial boilers (sludge or special waste incinerators); coal-fired power plants; liquor-fired boilers; filters and spray absorbers; cement kilns; zinc works. Certification All explosion generators are CE-certified as pressure equipment (cat. II and cat. III, respectively) according to the Pressure Equipment Directive (PED). Additional types are under development or already in the process of certification. SMART Explosion systems serve to keep clean superheater and economizer bundles as well as empty passes. Their low space requirement of only about 1.5 m³ per explosion generator is a key benefit, especially in cramped site conditions or where boiler access is restricted. A further advantage consists in the fact that the equipment can be installed during operation, i.e., there is no need for a boiler shutdown to install the SMART Explosion system. SMART Explosion EG 10 on rear/front wall

6 Clyde Bergemann is represented in over 40 countries worldwide. Clyde Bergemann Headquarters Clyde Bergemann Companies Clyde Bergemann Associates Clyde Bergemann GmbH Schillwiese 20 D Wesel Phone: Internet: For information about the Clyde Bergemann companies and contact details please visit CBPG 10/17 Subject to technical modifications.