COMPARISON OF METHODS OF BIO-MASS GRINDING

AS USED IN THE POWER INDUSTRY WITH SPECIAL REFERENCE TO GRINDING

ON ROLL GRINDERS

FP Engineering specializes in the grinding of a variety of bio-mass materials, e.g. rape bran, sunflower husk pellets, straw pellets, wood shavings. The innovative bio-mass grinding technology offered by FP Engineering is result of research, extensive testing and information from current installations. The flexible grinding system enables the user to adjust the final product granulation to requirements during operation of the line.

We offer comprehensive services for:

• process design, • bio-mass trial grinding tests, • engineering works, • equipment supply, • start-up & commissioning, • service.

Our design includes the information required by a civil contractor for building design. We have made numerous milling tests of a wide variety of bio-mass materials. Milling tests can be done on the materials to be ground at the request of the customer. Due to international business the company has a wide base of reliable suppliers and manufacturers. Long-term cooperation ensures favorable prices, timely delivery and high quality service.

Each project is different and during the design our company takes into account many factors such as flexibility of production, the nature of the raw materials and requirements of the final products. Health & Safety and fire protection norms as well as ATEX requirements are also taken into account.

We design and supply complete technological lines for bio-mass grinding for the Power Industry.

A standard line consists of the following elements:

• intake of bio-mass material,

• bio-mass mechanical conveying and storage,

• separation of mineral and ferromagnetic impurities,

• bio-mass grinding (milling),

• low pressure pneumatic conveying of the ground bio-mass to bins and furnaces.

Bio-mass intake

Bio-mass storage

Separation of mineral and ferromagnetic

impurities

Bio-mass grinding

Intermediate ground bio-

mass bin

TYPICAL SCHEME OF BIO-MASS INSTALLATION

To Furnaces

The Intake section for the bio-mass would consist of a truck or rail unloading hopper with a system of mechanical transport for transferring the material to storage bins. In order to reduce dust concentration in the receiving hopper, and thus reduce the risk of explosion, we use filters alongside the intake hopper.

Before the bio-mass grinding separators are used to remove mineral impurieties such as stones as well as ferromagnetic impurities. The separation of these impurities extends the life of the working parts of machines and reduces the risk of ignition, explosion, and extend the periods between replacements of fast-wearng parts.

Separation of stones is made by application of fluidized-sieve separator, and separation of magnetic impurities using magnetic separators.

Depending on the technological system being used the bio-mass material is weighed on scales - having an accuracy of +/- 0.3%

After grinding the material is conveyed via a blowing line (blow-through airlock and Roots type blower) to the intermediate ground bio-mass bin(s).

The whole process starting from the separation of impurieties, through sampling, weighing, milling, to blowing line utilises gravity rather than pneumatic transport.

We are the manufacturer of all the basic equipment for mechanical and pneumatic conveying as well as the weighing and de-dusting (exhaust) systems. After discharging the ground material from the storage bins a blowing line conveys it to the furnaces. Our company has extensive experience in designing and supplying pneumatic conveying systems for a variety of bulk materials. The longest blow-line made by our company is 723 metres long with capacity of 25 t/h

We utilise our innovative bio-mass grinding technology, which is result of many years research, laboratory and construction works.

We have completed a large number of bio-mass trial grinding tests. We are the only company that has undertaken to carry out controlled grinding testing of bio-mass material.

In consulation with customers we run tests of on materials in terms of their milling, storage and transportation capabilities.

Our innovative technology is a new method of biomass grinding. Traditionally hammer mills have been used for the grinding. These have high power consumption and high spare parts costs, as well as the possible risk of explosion. We replace these with roll grinders which have been used for grinding of various granular materials in other industries. In developing the technology for bio-mass grinding utilising roller mills our intention was to introduce an alternative, safer and cheaper technology. (Examples of products that are ground on roll grinders: cereal grains, pepper, pelleted materials, peanuts, granulated fertilizer, ferrous sulfate, coffee, salt, varous kinds of dried fruits).

The working parts of the machine used for grinding are rolls with a grooved (fluted) surface. Bio-mass grinding occurs as a result of the “scissor” cutting action of the rolls (rather than the “pulverising” effect of Hammermills). The grinding process is a combined result of the crushing and shearing forces in the gap between the rolls.

Obtaining the proper degree of bio-mass granularity depends on:

1. Peripheral speed of the grinding rolls

2. Gap between the grinding

rolls 3.Roll speed differential drive 4. Type of applied roll grooving

(fluting)

DIFFERENT MATERIAL LAYERS OF ROLL

Outer hardened part of roll (ca. 20mm depth)

Inner softer

layer

”Plug” holding the spindle

Fluting (grooving) is cut diagonally across the length of the roll.

Opposing grooves (fluting) give a

shearing/cutting action

Various angles of grooves (flutes)

can be used

DURING THE GRINDING PROCESS THE GROOVES OF THE LOW-SPEED ROLL HOLD THE MATERIAL AND THE

GROOVES OF HIGH-SPEED ROLL SHEAR AND GRIND IT.

Profile of roll grooves (fluting)

The groove has two surfaces – sharp and dull. The surfaces form angles: the angle of sharp and

the angle of dull

Settings of grinding grooves in the inter-roll slot:

Sharp to Sharp Dull to Sharp

Dull to Dull Sharp to Dull

Based on our experience we match the configuration of grinding machines - peripheral speeds of the grinding rolls, inter-roll differential transmissions, roll fluting and other work parameters according to process requirements. These elements influence grinding capacity as well as the degree of grinding.

Typical particle size %ages on a roll grinder

(material humidity <15%, fat content <4%)

* Above given parameters concern particle size in three dimensions

Kind of biomass

Grinding degree*

Sieve throughs (%) sieve

dimension:

2 mm 1 mm

Rape seed meal 97-98 75-80

Straw pellets 85-90 55-60

Sunflower husk pellets 95-97 70-75

Wood pellets 85-90 55-60

In our installations we can apply two types of grinding machines: • Crusher with one pair of rolls (single high) • Roll grinder with two pairs of rolls stacked one above the other (two high). With these options, we can construct different variants of the progressive bio-mass grinding: • pre-grinding, and • final grinding.

SCHEMATIC DRAWING OF ROLL GRINDER WITH ONE PAIR OF ROLLS ON EACH SIDE

SCHEMATIC DRAWING OF ROLL GRINDER WITH TWO PAIRS OF ROLLS PER SIDE

The double grinding system using crushers is used only in exceptional cases - only for certain types of exotic bio-mass materials and bio-mass in the form of pellets of non-standard dimensions. A suggested grinding system is the result of the earlier trial grinding tests. The initial fragmentation occures in the correspondingly adapted crusher. A Roll Grinder is used for proper grinding.

EXAMPLE OF A BIO-MASS GRINDING

INSTALLATION WITH 2 HIGH ROLL GRINDER

EXAMPLE OF BIOMASS GRINDING

INSTALLATION WITH A CRUSHER MILL

FOLLOWED BY A ROLL GRINDER

Benefits of the bio-mass grinding line based on roll grinders compared to hammer mills.

Bio-mass grinding line based on hammer mills requires: • higher power requirement, • more sophisticated and complicated aspiration system, • usage of a larger floor area and building area - which increases the cost of investment, • extensive explosion prevention system (because of the characteristics of the hammer mill), • additional transportation equipment and intermediate biomass bins, • the range of particle sizes cannot be controlled

Benefits of the bio-mass grinding line based on roll grinders compared to hammer mills.

Bio-mass grinding line based on roll grinders is characterized by:

• considerably lower power requirement (approx 1/3), • substantially reduced noise levels, • gravity feed & discharge, • reduced demand for space required for installation, • possibility of roll re- fluting = lower spares costs (hammers/screens are not subject to regeneration) • adjustment of particle sizes can be made during operation, • construction and method of grinding in a roll grinder greatly reduces any risk of explosion, • roll grinder process is less aggressive than hammer mills - fragmentation of products is the result of cutting and not impact.

The innovative technology supplied by our company allows considerable maintenance and energy savings to be achieved when compared to previous technology. The application of the FP Engineering grinding system in a grinding line leads to savings in: • costs of working parts (hammers, sieves) • costs of energy

Hammer mill Roller Mill – innovative technology

Capacity [t/h] 10,0 10,0-15,0 – depending on biomass type

Installed power [kW]

300-450 134

Everage cost of biomass grinding

10 t/h [PLN]

87-130,5 38,86

The annual difference

in cost of electricity consumption[PLN]

421 700 802 766

* 1 kW = 0,29 PLN

Installation consists of 3 grinding lines with nominal capacity 10 t/h, (max 12 t/h each)

Installation of FP Engineering grinding system in a bio-mass processing plant in a power station in Poland (owned by EDF)

On the left the bio-mass storage tank with a capacity of 600 m3 (fitted with vibrators to ensure no material “hang-up”) On the right a bin mounted Filter for exhaust (dust removal) of bin(s) during filling.

Intake section with filters.

From left elements of aspiration line. In the middle of the storage tank with twin-screw discharger and magnetic separator. This system is located directly above the roller mill.

Roll Grinder

Part of pneumatic transport line consisting of blow-through airlock with hopper.

Roots type Blower for pneumatic conveying (acoustic hoods available where required)

Installation of FP Engineering grinding system in a bio-mass processing plant in a power station in Poland

(owned by CEZ).

Roll Grinders

Fluidized-sieve separator for separation of mineral impurities

Roll Grinder

Roll Grinder

Part of pneumatic transport line consisting of blow-through airlock and hopper.