The methods of improving physical and chemical properties of solid fuels and products obtained in that process

The methods of improving the physical and chemical properties of solid fuels, especially those made from biomass, brown coal or related products obtained in that process, is the basis of the invention.

Significant cost reductions may be obtained in industrial processes that utilize solid fuels to produce heat and electricity may be achieved by substituting inexpensive fuel such as brown coal or common biomass. Due to the technological requirements of existing power plants substitution is not always possible.

The most popular fuels of biological origin are solid fuels obtained from biomass, mainly wood or vegetable waste. The most commonly used materials from this group are currently straw, timber, sawdust, wood chips, and bark. There are problems that prevent their use in heat and power stations. Low heat-to-weight ratios and seasonal availability create logistical problems, including transport and storage requirements of large amounts of materials. Biomass is generally moisture-prone and can easily decay, ferment, and compost. This decomposition negatively affects its energy producing properties especially its heat value as a result of that moisture. Brown coal has similar problems. While this type of fuel is readily available and inexpensive its high moisture content sometimes makes firing impossible and forces process support through the introduction other high heat- value fuels.

Patent literature states that the problem of utilizing inexpensive and/or renewable fuels is solved by investing in new installations adapted for firing with a specific kind of fossil fuel. Taking into consideration existing big power stations fired with solid fuel this type of solution is economically questionable. The direction of development for this technology is co-firing hard coal or brown coal mixed with biomass fuel to produce a fuel in the proper heat range so they can replace high-heat value fuels.

Plantation owners and farmers know the kinds of plants that grow fast e.g. willow which has a heat value ranging from 5.5 MJ/kg to 18 MJ/kg depending on moisture content. On the other hand the most popular boilers in Polish power plants are designed for burning pulverized hard coal which has a heat value ranging from 17 to 23 MJ/kg. Another group of units, it is brown coal fired boilers, i.e. fired with fuel with heating value not exceeding 10 MJ/kg. Hard coal or to be more specific fine coal's heat value is practical independent of influence by weather conditions that severely affect biomass and brown coal. Both water and

steam can increase fuel moisture by capillary and water molecule cohesion to its pieces. The fuel heat value of biomass is affected detrimentally from the point of view of keeping stable burning parameters that are required due to moisture problems. This process is depicted in Patent Claim WO01/25689. Pulverized bio-fuel is mixed with fine coal dust from hard or brown coal so that the fuels are commonly fired. The mixing is accomplished during belt conveyor or bucket fuel transport when pouring takes place.

Another example of mutual combustion is presented in Russian patent claim RU 2189526 which uses wood waste and achieves proper firing by blowing air pre-heated with the combustion gas.

The core of this invention is its method of improving the physical and chemical properties of solid fuels, especially those made from brown and hard coal, biomass obtained like wood waste, wood chips and other biomass originated materials as well as sewage sludge featured by processing them in a bath of hot vegetable, animal or mineral oil. Oil from saturated coal can be reclaimed by pressing, using vibropress or through centrifugal separation.

It is important to note that water evaporation heat is recovered with heat exchangers and by the reutilizing a volatile substance from coal hydrogenated oil is obtained. This invention allows for obtaining fuel of high-heat value. Steam pressure can be used for running the turbine producing mechanical or electrical energy or power.

This fuel can be used as substitute for high-heat value hard coal and in some cases also for coke. And hydrogenated oil can be applied for many purposes including the power generating industry.

The solution according to this invention is depicted in the drawing where Fig. 1 is the diagram for brown coal increasing fuel parameters including water evaporation energy recovery.

A batch of brown coal 1 is submerged in tub 2, containing hot vegetable oil 3. Oil temperature 3 in the lower 2 tub's zone 4 substantially increases water boiling temperature which speeds up boiling and evaporation of moisture in brown coal 1, including hygroscopic moisture. Next, gas is relieved from coal 1 and moisture is replaced by oil 3. Zone 5, over brown coal layer 1 keeps mixture of oil, volatile substance and steam. Up higher, where heat exchanger 7 has been placed, zone 6 is formed to reclaim heat from evaporating water. Carbon dioxide 8 and water solution is formed in the top part of zone 6. Superficial zone 9 contains "cold" oil 3 prevents volatile substances from leaving the bath generates better absorption by oil 3. Whole oil volume 3 absorbs volatile substance obtained during

hygroscopic moisture evaporation during chemical reaction and due to its viscosity. In the case where brown or hard coal is fed to vegetable oil bath by specific time at specific temperature then moisture is completely evaporated and volatile substance from hygroscopic moisture, according to the principle that gas solubility goes down to zero in boiling water, reacting with oil and this includes oil hydrogenation. This oil is also turned into high-heat value and ecological fuel.

Brown coal or biomass that has achieved higher parameters can be mixed with other fuels or burned separately and can also be applied as a hard coal substitute in power and energy producing units that normally use hard coal. This allows for using this fuel in many power industry installations that are not adapted for inexpensive fuel substitutes. This process also allows for applying different kinds of vegetable, animal oil, or petroleum. Its additional advantage is the fact it can be stored for some time without lowering its heat- value as it is impregnated and does not absorb ambient water. Fine brown coal soaked with oil can be granulated or converted to briquettes.

This invention's method fills the gap in recent processes and connects them into one that is processed individually. The method depicted in this claim assumes professional, calculation and research based, fuel heat value increase for low parameter fuels and adapts them for firing in power industry units. Power industry processes impose strict requirements for fuel quality especially in reference to their physical parameters stability. This invention allows for obtaining fuel that meets physical parameters stability and solves problems caused by moisture content in low-heat value fuels. It allows efficient fuel drying, reclaiming of evaporated water heat, storage in oil of the greater part of gas from coal, mainly hydrogen, improved energy parameters of oil that can be also used as fuel.