Rice husk-fired CFB boiler

According to the combustion characteristics of rice husk, designed the rice husk-fired CFB boiler. Manufacture

(1). Boiler parameters:

1	Nominal capacity	D	4	t/h
2	Operating pressure	P	1.25	MPa
3	Feed temperature	tgs	20	°C
4	Saturated steam temperature	tbq	193	°C
5	Cold air temperature	tlk	30	°C
6	Blowdown rate	ρ	5	%
7	Smoke exhaust temperature	θpy	180	°C
8	Fuel for design		Thailand rice husk
9	Lower heating value	Qnet,ar	11393	kJ/kg
10	Design efficiency	η	78	%
11	Fuel consumption	B	1223	kg/h
12	Overall heating surface	H	186	m2

(2). Boiler characteristics.

a. full tube structure with double drum longitudinal layout is adopted, more rational, more safety and more reliable.

b. package boiler structure is adopted, make the boiler proper, burn room and air distribution plate as a whole, and economizer as a single. Steel frame and platform and stair are as another piece. The installation period is reduced greatly.

c. the medium fluidized bed combustion technology is adopted to provide a steady and fine fluidized combustion, even though rice husk is a kind of poor mobility particles with rough surface.

d. lower thermal state fluidized wind velocity is adopted to reduce the wear of heating surface in dense area.

e. cap plate with holes on the top of furnace is installed so that the flue fas velocity will be uniformed and the particles carried by flue gas will be reduced effectively.

f. cyclone furnace burn room at the outlet of furnace is set up to further improve the combustion efficiency and reduce the amount of fly ash.

g. lower flue gas velocity in convection tube bank is used to meet the feature of high silicon in rice husk ash to reduce the wear and tear on the heater surface and to prolong the boiler service life.

h. The boiler is small, good in appearance, and takes up less area. Its water capacity and thermal interior are small, start-up and shut-down time are reduced, and fuel and power consumption are also reduced.

i. Screw feeder is used in positive pressure zone; it has the advantages of high combustion efficiency, low air leakage coefficient, and environmental friendly.

j. Cast-iron economizer is used with the characteristics of high silicon resistance, wear resistance, and long service life.

k. Equipped with automatic control of boiler water level, it will alarm at high-limit or low-limit water level, and shutdown automatically at extreme low water level or overpressure state. With practical control function such as start-up and shut-down for forced draft fan and induced draft fan in order. The operation of this boiler is simple and safe.

l. fluidized combustion technology is used, the boiler load adjustment range is relatively wide (25%~110% rated load) with flexible regulation and stable operation.

m. The boiler’s thermal efficiency of rated load test is 79.3%; it has reached the advanced level of similar products, and much superior to the chain grate rice husk-fired boiler. It can save 3000 tons of fuel for users every year.(calculated by running 7200 hours)

n. Rice husk ash has high silicon content, it is not only just a clean bio-fuels, but also can control its combustion complete degree, and the solid residues (ash) can be used as raw materials for silicon extracting.

o. The noise test in boiler room is lower than 85dB, dust capacity in chimney flue gas emission is 146mg/Nm3, Ringelmann smoke blackness is less than level 1. Environmental indicators are in line with national standards for the requirements of second-class areas.

Rice husk-fired CFB boiler