feasibility of industrial wood pellet production

Industrial wood pellet production developing background

Renewable energy, as what we know, is one of the most important kinds of fuel in recent years. It takes about 10% of world energy consumption, and almost 80% of developed countries. In developing countries, the consumption of renewable energy also increases fast. While the most significant renewable energy is perhaps biomass energy. Some experts say, energy is planted rather than exploited. With world developing, limited amount of fossil fuels can hardly meet the demand of modern society. As a result, to rationally develop renewable biomass energy becomes a key measure to solve energy crisis.

Nowadays many countries have developed biomass energy, especially wood pellets, to gradually replace fossil fuels. A large proportion of wood pellet production is made from industrial pellet mills, while a small proportion is home scale production. here we mainly discuss the industrial scale wood pellet production.
 

Industrial wood pellet production process

The industrial production of wood pellets is composed by raw material preparation, sieving, drying, screening, pelletizing, cooling, sieving, and packing procedures. All parts are equipped with strict quality control system to guarantee product quality. The production process can be seen below.

Detailed steps of industrial wood pellet production

1. Raw material pile: the raw material is mainly wood sawdust. The size of raw material storage shall be around 500m². To make sure normal and continuous industrial pellet production, the raw material shall be enough for at least 2-4 days in case of raw material shortage. The ceiling of raw material warehouse shall be rain, thunder and wind proof; the fire separation shall be at least 50m away from production area and living area, >30m away from road, and >30m away from power transformer. Also, the warehouse shall be equipped with fire protection facilities.

2. Sieving: raw material is delivered by a screw conveyor into the sieving machine to sift out large size wood blocks or iron nails and other impurities.

3. Drying: the industrial pellet mill requires low moisture content of raw biomass material. Therefore, after sieving, wood sawdust is delivered into the rotary dryer for heat drying.

4. Cyclone separation: in the conveying of raw material after drying, there is still plenty of moisture left; the moisture shall be discharged by a cyclone separator. In this industrial pellet production system, there are 2 sets of cyclone separators: the second one is used to discharge the moisture from wood pellets after cooling.

5. Raw material conveying: in accordance with customer demand, this industrial pellet mill line adopts screw conveyor, auger conveyor and elevator to deliver raw material into relevant equipments.

6. Pelletizing: the industrial pellet mill is the core part in the complete production line. At GEMCO, we have 3 models of industrial pellet mills for you to choose: BPM35 (0.5-0.8ton/h), BPM420 (1.2-1.5ton/h), BPM508 (1.5-2ton/h). GEMCO industrial wood pellet mills can also process many kinds of other biomasses. They are stable to use. The wood pellets made by GEMCO industrial pellet mill can reach 1.0-1.3ton/m³ density. Most customers who produce 5ton/h or more usually purchase one more set of pellet mill in case of emergencies.

   Small industrial pellet mill BPM35 (500-800kg/h)	Large industrial pellet mill BPM420/508 (1.2-2.5ton/h)

7. Cooling: when the wood pellets are made out, their temperature is as high as 80-90℃ with loose structure and easy to break; therefore these wood pellets need to be cooled by counter flow cooling system till room temperature. This system is designed with cooler and cyclone separator to separate the powder and return it to previous procedures for re-pelletizing.

8. Pellet sieving: the wood pellets after sieving can be sieved by vibrating sieve. The broken ones will be sifted out for reproduction, and intact ones can go to finished product warehouse.

9. Packing/storing: the finished pellets can be packed or stored in the warehouse.

The heat value of different biomass pellets

Index	Fir wood pellets	Pine wood pellets	Stalk pellets	EU standard (DIN51 731)
Heat value (MJ/kg)	19.42	19.86	16.38	17.5
Heat value (KJ/kg)	4646	4751	3919	4187
Moisture content (%)	8.7	9.2	8.4	<12
Density (kg/m3)	1.22	1.23	1.12	1.0-1.4
Ash content (%)		1.01	12.5	<1.5
Sulphur content (%)	<0.03	<0.02	<0.06	<0.08
Nitrogen content (%)	0.16	0.16	0.24	<0.3
Chlorinity content (%)	0.002	0.002	0.002	<0.03