Technology & Product - Nowva Energy

The "Horizontal Circulating Fluidized Bed Combustion Technology" is a world-leading efficient and clean biomass combustion technology jointly developed by Nowva Energy and Tsinghua University.

This technology innovatively puts forward the concept of "three-bed, two-return and multi-pass" horizontal circulating fluidized bed, which effectively solves the problems of low thermal efficiency, high initial NOX emission and poor variable load operation capacity of small and medium-sized biomass fired boilers. It fills the technical gap of small and medium-sized fluidized bed boilers worldwide.

Product Performance

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Product Advantage

Four ultra characteristics: Ultra-wide fuel adaptability, ultra-high actual operation thermal efficiency, ultra-long operation period and less maintenance, ultra-low environmental protection operation cost.

Ultra-wide Fuel Adaptability

99 %

Ultra-wide Fuel Adaptability

Solid fuels with a low heating value of 6.3-25.0MJ/kg are suitable for the boiler . It can meet the pure burning or blending burning of agricultural and forestry wastes and biomass industrial wastes. The operation is steadily, which can realize the clean and efficient operation under the load between 30%-110%.

Ultra-high Thermal Efficiency.

92 %

Ultra-high Thermal Efficiency.

The actual operation thermal efficiency is 80%-92%, up 20 percentage point comparing with the conventional small and medium sized industrial boiler, a remarkable energy conservation effect.

Ultra-long Equipment Operation Period and Less Maintenance.

225 天

Ultra-long Equipment Operation Period and Less Maintenance.

The annual operation time is over 8000 hours which has realized 225 days' continuous operation. The two-stage separation of materials at high temperature and medium temperature has strong resistance to ash accumulation and slagging, making it more suitable for biomass fuels with low ash melting points. The maintenance cycle is extended and the maintenance cost is low.

Ultra-low Environmental Protection Operation Cost.

50 mg/m3

Ultra-low Environmental Protection Operation Cost.

Low temperature combustion and staged air distribution reduce the NOX initial emission concentration to lower than 100mg/m3 from 500 mg/m3. With the assistance of SNCR method, an ultra-low emission standard of 50 mg/m3 can be met.

Industry Comparison

The patented "three beds, two returns" horizontal circulating fluidized bed technology of Nowva Energy innovatively solves the global problem in miniaturizing fluidized bed boilers. This technology fills the gap of 35t/h and below fluidized bed boilers worldwide. The technology is significantly superior to similar products in terms of various technical performace when applied to small and medium-sized boilers below 75t/h.

Comparison between Horizontal CFB boiler and the conventional vertical CFB boiler

Project	Horizontal CFB boiler	Conventional CFB boier(vertical)
Specification	≤110t/h	≥75t/h
Thermal efficiency	≥88%	/
Separation temp	≈500℃	≈850℃
NOX initial emission≤100 mg/m³	≤100 mg/m³	≈500 mg/m³

Principle of Combustion Technology for New Type of Horizontal Circulating Fluidized Bed Boiler

Three-stage Furnace and Two-stage Material

circulating increases the effective combustion period and improve combustion efficiency

Medium Temperature Separation, Temperature 500℃

two-stage separation to prevent post-combustion and separator coking.

Low Temperature Combustion and Stage Air Distribution

The initial emission of NOX is lower than 100mg/m3.

This product creatively bends the rising bed furnace of the conventional vertical circulating fluidized bed boiler 180° twice "fold one into three". The height of the boiler is reduced and the furnace arrangement extend to the direction of depth from height. Reducing height and then extending depth forms the unique horizontal layout of three-stage furnace(three beds) with compact structure. Besides "rising bed", the main combustion chamber
①, it newly adds "downer" secondary combustion chamber
② and "second rising bed" Burningout chamberTwo-stage material recycle, "two returns" is composed of the primary material return system ⑤ and secondary material return system ⑥. The fuel is fed into the furnace by the hopper and mixed with the material along the furnace. In the bottom of the secondary combustion chamber, the bed material is divided into two parts. One part of the materials return to the primary combustion chamber through the primary material cycling entrance to form the first stage of the material circulation (reverse U-shaped channel ⑦ ). The other part of the material enters the post-combustion chamber from the secondary combustion chamber and then is separated by the separator ④, and returns through the feed leg to form the second stage of the material recycle (positive U-shaped channel ⑧).Three-stage furnace structure and two-stage material return ciruculation extend the length of the furnace by 60% which prolong the fuel combustion process in the furnace so that the combustion is much more sufficient with the boiler's thermal efficiency rising from75% to 88%-92%.

Compared with the traditional vertical CFB boiler, the horizontal CFB boiler introduces secondary combustion chamber and the burnout chamber. It realizes the high temperature separation of materials at the bottom of the secondary combustion chamber and the medium temperature separation of materials at the outlet of the burnout chamber. The working temperature of the medium temperature separator is about 500℃ , much lower than that of vertical CFB boiler(about 850℃) so it has strong resistance to ash and slagging in secondary combustion chamber, burnout chamber and material circulation loop. This technology is more suitable for biomass fuel with low ash melting point and the continuous operation time of the boiler is increased to not less than 4 months, which is easy to maintain. The extending of the maintenance cycle and the high availability rate of equipment decrease the maintenance cost.

To solve the problem of high NOX initial emission of biomass boiler, the air and fuel are arranged in stage. The three-bed multi-stage circulating combustion technology is proposed and the fuel staged nozzle was innovative added to form a three-bed multi-stage low-NOX-CFB combustion technology which is able to reduce the NOx initial emission to lower than 100mg/m3. Adding desulfurizer such as limestone to the primary combustion chamber can also remove sulfur in the furnace. Equipmented optically with SNCR, FGD, bag filter and other auxilary facility together it can realize ultra-low emission economically and efficiently. Compared with the conventional technology, it can reduce the operating cost of desulfurization and denitrification of by half while can reach the same environmental protection emission standard.