1, overview

Biomass is a kind of renewable energy, but it has low calorific value, low ash melting point and high alkali metal content. According to the special components of biomass and combustion characteristics, Beijing Thermal Energy Technology Co., Ltd. and Tsinghua University jointly developed a horizontal circulating fluidized bed biomass boiler, the boiler has high heat efficiency, no coking, no accumulation characteristics of ash, fuel adaptability etc..

2, the main technical parameters

Boiler type: horizontal circulating fluidized bed biomass boiler

Boiler output: 4 ~ 75t/h (2.8MW ~ 53MW)

Thermal efficiency: 86 ~ 90%

Applicable fuel: biomass particles, biomass bulk

Calorific value range: 1500-4000Kcal/kg

Furnace structure: membrane wall

Dust removal: bag filter

NOx Governance: low temperature staged combustion

Applications: power generation, heating, industrial steam

3, the main technical characteristics of horizontal circulating fluidized bed biomass boiler:

(1) increase of fuel combustion time, high boiler thermal efficiency

Volatile biomass is high, generally more than 70%. The residence time of volatile components in the furnace is short, and the burning rate of volatile components is not high due to the insufficient height of the furnace and the conventional circulating fluidized bed boiler. This product adopts three stage furnace structure, compared with the vertical circulating fluidized bed boiler, an increase of the furnace height of 60%, so that the combustion time of volatile components longer, full combustion. At the same time, the boiler adopts two stage ash returning structure to further reduce the carbon content of fly ash. Fly ash combustible below 3%.

In addition to the high rate of fuel burn out, the boiler also uses a full film wall seal structure, good thermal insulation, heat loss is small, the heat dissipation is only 1%.

The company's 15t/h biomass boiler has been tested, the thermal efficiency of the boiler reached 88.98%.

(2) strictly control the combustion temperature, effectively control the occurrence of coking.

The ash melting point of biomass is generally low, and the boiler is easy to coke. This product adopts low temperature combustion technology, which can effectively prevent the furnace from coking. The temperature of the dense phase zone is controlled at 800 DEG C by reasonable selection of wind speed, air volume and temperature. At the same time, for more than 35t/h of the biomass boiler, in the dilute phase of the furnace layout of the water cooling screen, increase the furnace radiation heat absorption capacity, to maintain the temperature control of the furnace dilute phase zone at about 850 degrees celsius.

(3) the medium temperature separation can be used to prevent the coking of the latter and the separator

The separation temperature of the conventional circulating fluidized bed is 850 - 900 DEG C, which often occurs after the combustion of biomass. The product of an ash temperature is 650 DEG C, two ash temperature is 500 DEG C, due to the low temperature ash, can effectively control the combustion temperature, dense phase zone does not occur at the same time, the separator and the tail heating surface coking phenomenon. In addition, due to the separation of medium temperature, can reduce heat loss, can increase the life of the separator.

(4) effective treatment of tail ash deposition.

Due to the high content of alkali metal in the biomass ash, the ash viscosity is relatively large, it is very easy to cause the boiler tail heating area ash. We take the following technical measures in boiler design:

One is to take the economizer in-line arrangement, and increase the pitch; and, as a result of the economizer of boiler smoke temperature of about 500 DEG C below the entrance, the deposition temperature of alkali metal bond, so it can effectively prevent the economizer in the convection tubes on ash deposition;

Two is a small proportion of convection heating surface in the design, but also effectively reduce the alkali metal caused by the bond deposition;

Three is to take the best soot blowing effect of gas pulse soot blower.

In the actual operation of the boiler, no ash deposition occurred.

(5) a wide range of fuel types, suitable for a variety of biomass.

At present already processed biomass fuels are: corn cob, rice husk, medicine dregs, coffee, wheat bran, tobacco stalk etc..