EFB Pellet Combustion

Azeus Pellet Machinery

Page 2

Introduction

EFB pellet is pelletized by the byproduct of EFB, as a

new biomass, it is friendly to the environment. However,

EFB contains a large variety of different fuels with

different chemical composition and combustion

characteristics. If making it into pellet in the case of

unpretreament, which may lead to slagging, fouling and

corrosion when combustion.

Page 3

Problems Occurred During the Combustion of EFB Pellet

Page 4

The Main Chemical Composition in EFB Pellet

Chlorine is a special minimal nutrition elements, and it

widely exists in nature. In the seven kinds of necessary

trace elements, plants contain the highest chlorine

content. Such as rice straw, EFB etc. EFB still contains

large quantity of alkali metals, such as, K, Na, Ca, Mg,

etc, and it still contains inorganic element, such as N,

etc. It can generate KCl, NaCl, NOx, HCl, etc easily

under high temperature(>450°C). These ingredients will

generate slagging and corrosion.

Page 5

Slagging and Low Ash Fusion Temperature Problems

Firstly, during the EFB pellet combustion process, its raw

material composition, the parameters(furnace

temperature, contact to the air, heating surface

temperature ) and fuel shape has a certain impact on the

deposition. High chlorine content in the raw materials

can promote the liquidity of alkali, and easily to form

alkali metal chlorine, then deposit on heating surface; if

the furnace temperature rises, it is contributed to the

escape of alkali metal from fuel. The alkali metals

condensate on the fly ash, and reduced its melting point,

which are more likely to cause slagging problems.

Page 6

Corrosion Problem

Moreover, caused by alkali corrosion mechanism, the

furnace temperature, chlorine content and deposit

volume are the important factors affecting corrosion. In

the process of corrosion caused by solid alkali metal

oxide, furnace temperature and the deposit volume’s

increasing will obviously increase the oxidation rate of

boiler steel. And the rise of temperature will accelerate

the response to the corrosion; and the increasing of

chlorine content in EFB pellet will also cause corrosion.

Page 7

Solution of Problems Which Occur at Combustion of EFB Pellet 1. Use multi-fuel boiler which is suitable for burning EFB pellets.

2. Using washed method to remove part of alkali metal before pelletization. Most of the alkali metal elements in EFB are water-soluble, so washed method can be used as an effective method to eliminate alkali metal problem. After washing, the ash has different degrees of decline, and ash melting has been improved, and reduced the corrosion problem caused by alkali metal.

3. Using additives when pelletizing. Such as, kaolin clay, activated alumina, dolomite, silica and diatomite. It can solve the problem of chloride content and corrosion effectively.

4. Co-firing with fossil fuel will solve the problem of low ash fusion temperature and reduce the chloride content.

5. Lower combustion temperature is also the effective way to solve the problem of low ash fusion in the EFB pellet burning.