BACKGROUND It is well known that certain alkali metal compounds have a low melting temperature and therefore leads to problems with sintering when biomass, which have a high alkali content, is combusted, gasified or pyrolysed. Silicon is another element typically abundant in the fuel or as a bed material added to fluidized-bed systems as silica. Alkali compounds in combination with silica and possibly small amounts of calcium can produce low-temperature eutectica.

These may cause severe agglomeration and sintering in combustion, gasification and pyroly- sis reactors; in particular at temperatures above 750°C. Besides alkali compounds, which condense on cold spots in the reactor or downstream of the reactor, can cause corrosion problems.

K20-4Si02 melts at 765°C. KrO-4SiO2 mixed with small amounts of CaO-Si02 produce an eutectica below 750°C. Also K : CaSi304 have been measured in the sintered bed material.

The melting of inorganic compounds into sintering particles causes bed defluidization and diminish the carbon-catalyst contact. Additional CaC03 have been shown in laboratory scale to cause significant neck growth between the particles (Skrifvars 1994,1997) which can lead to agglomeration in the bed. Information about melting temperatures for several inorganic mixtures including oxides of Si, Ca, K and Na can be found in Levin [1985]. See the dia- grams: fig. 391,395,401 and 485. One way of preventing agglomeration is to use additives in the process in order to convert the harmful alkali species. A number of possible additives are known. Such additives should be abundant and cost effective in use and during their use result in products with a useful and valuable property e. g. as a fertilizer. Anti-agglomeration agents in biomass typically deactivate the catalyst. The aim is, however, to maintain as much catal-vilc effect as possible and at the same time avoid severe agglomeration and sintering during the combustion, gasification or pyrolysis process.

REATECH's INVENTION ReaTech's invention improves the combustion, gasification and pyrolysis process in an eco- nomical way and increases the value of the residual products.

Observation in our laboratory lead to the proposal that for fuels containing large amounts of potassium and sodium together with calcium and silicon, the melting tempera- tures are increased and the ash properties improved by the addition of phosphor compounds said in the form of phosphoric acid, H, PO4, or calcium di-hydrogen phosphate, Ca (HnPO4) *H20 or H4P207.

The phosphorous containing additive may be added alone or directly to the fuel as a liquid, slurry, solid, powder, granula material or as a gas. The phosphorous containing addi- uves may De added in combmation mth the tuel and added catalyst and bed matenat in sucn amounts that the product phosphor compounds are sufficient abundant to prevent agglomera- tion and sintering to take place. The amount of phosphorous addition depends on the process conditions, bed material, externally added catalyst and the inherent ash composition. The maximum needed amounts of moles total phosphorous added to the process necessary to pre- vent agglomeration and sintering will typically be equal to the sum of the molar contents of the alkali metals and the earth alkali metals introduced to the reaction zone. In simple cases the maximum amount is equivalent to the molar amounts of alkali and earth alkali metals inherent in the fuel. In most cases half or less of this amount is sufficient. In specific cases the amount, type and form of other additives or bed material must be considered. One typical bed material in a circulating or a bubbling fluid bed reactor is calcium carbonate, which will also partly react with phosphate to calcium phosphate. In case Ca (H, PO4) 2*H2O is introduced as an additive, parts of the calcium herein will also react with the phosphate during the con- version process.

Using SEM-EDX ourselves, FTIR light scattering together with M. Sc. Jimmy Bak [1999] and X-ray diffraction together with Dr. Poul Norby [1999], we have found K3PO4 in residual products in accordance with predictions from equilibrium calculations and also Ca (HPO4), KCa (PO4).

A number of these compounds provide a week catalytic activity without contributing to severe agglomeration and sintering through the reaction with silica. Several tests have been made at the laboratory of ReaTech and at the Department of Energy Engineering (DTU, Denmark). The resulting phosphorous containing compounds prevented melt formation and thus the addition of phosphorous decreases the agglomeration and sintering problems other- wise observe without addition of phosphorous.

All naturally occurring phosphorous minerals are (ortho) phosphates and several phos- phates are derived from phosphate rock. Phosphorous is thus a non-renewable resource.

Large amounts of phosphate are however utilized as a fertilizer and the phosphate utilized in the present process will after withdrawal from the reactor and with or without addition treatment substitute phosphates added directly to soils as fertilizers. Information about sev- eral relevant phosphorous containing mixtures and their melting temperatures can be found in Levin [1985]. See the following diagrams: Fiacre 246-248,536-540,665-668,959,960-962.

If abundant amounts of sodium is present, certain species may give low temperature eutec- tics, see Levin [1985]. These compounds have however not been detected for the relevant process conditions and Na seems in general to occur as gaseous NaCl.

PRESENT STATE OF ART The addition of phosphorous to processes involving conversion of carbonaceous material has been used by a number of other groups. In US5538929 a preparation method for producing a phosphorous treated activated carbon (containing 2.5% to about 10% by weight of phospho- rous support) is shown. An already activated carbon is used as a raw product. After prepara- tion activated carbon is suitable as a carbon based catalyst support for use in a wide range of catalytic applications. In the present invention by ReaTech, phosphorous compounds (even- tually together with various catalysts) are either directly added, or added together with a car- bonaceous fuel, to the combustion/gasification/pyrolysis reactor, where the carbonaceous fuel is being gasified-/combusted/pyrolysed. The product of the process is (besides a gasifi- cation gas) an ash containing phosphorous in various forms together with other ash com- pounds. The ash also contains small residual amounts of carbon. The phosphorous compound reacts with alkali and earth alkali compounds in the fuel hereby preventing the alkali and the earth alkali compounds from reacting to compounds causing severe agglomeration, sintering and corrosion.

In patent US4458095 zinc and copper (I) salts comprising halides, carbonates, sulfates, acetates and phosphates are utilized for a pyrolytic conversion of mbber and waste, which results m reduced level of sulfur and nitrogen impunies in the products. Zinc and copper (I) salts are not used in the present invention.

In JP52042806 a method comprising heating waste at 400°C in the presence of acidic cata- lyst (e. g. phosphoric acid treated silica) is described. The waste (e. g. polyethylene) is decom- posed into paraffin wax containing oil and gaseous products. Paraffin is recovered from the oil (containing approximately 80 wt. % wax) and the gas is used as a fuel for the reactor. In gasification the anti sintering effect is interesting for process temperatures above 500°C.

In JP58167682 in the presence of at least one compound selected from phosphate, sulfate, nitrate or halide of Group VIII is added to a hydrogenation process (500-950°C) with a hy- drogen pressure of 35-250 kg/cm2. A carbonaceous substance (e. g. pulverized coal) is hydro- genated. Group VIII phosphate compounds accelerates the conversion of carbonaceous sub- stance. It is not a part of the present invention to convert carbonaceous material in a hydro- genation process.

In JP54151585 a catalyst is carried by an inorganic heat resistant paint formulated metal oxide pigment. The carrier consists of alkali metal silicate (sodium silicate) and acidic metal phosphate, which has an excellent heat resistance. The catalyst is used to modify the gasifi- cation gas in order to minimize deposition of carbon and formation of tar. It is not a part of the present invention to add phosphate carried by an inorganic carrier consisting of alkali metal silicate and metal phosphate, and the purpose is different.

In JP2258067 a catalyst composed of a ceramic-supporting material wherein catalyst- compo-nents are described. This catalyst is immersed for promoting combustion of petro- leum and prevents gene-ration of free-carbon, hydrocarbon and CO gas. The catalyst may be the silicate of alkali metal or metal phosphate or metals of Pt family. Together with this com- position a substance activating the catalyst is included. The present invention does not in- clude the use of a ceramic supporting material to add phosphate carried by an inorganic car- rier.

In JP56070875 a coating capable of preventing deposition of carbonaceous matter, are formed by coating a minute inorganic paint in which metal phosphate is used as a binder, on the surface of metal base, followed by dring, further coating a paint in. In this paint is dis- persed a fatty acid-gasification decomposing catalyst with metal phosphate as binder, and sintering so as to form a coated layer. The catalyst is e. g. Na, KsO, CaO and MgO. The invention made by ReaTech does not add a paint that is used as a coatis.

In JP53136007 it is described how to produce a specially mixed fuel containing oil base and water. The oil base and water is separately contacted with acid (e. g. nitric acid, sulfuric acid, acetic acid, phosphoric acid, hydrofluoric acid) or alkaline catalyst (e. g. alkali and alkali earth metals) and then mixed under agitation and pressure. The mixed fuel is used for boilers and internal combustion engines. The invention by ReaTech adds phosphorous components to a process without preliminary mixing these components into separate fuels that are fol- los ino mixed and thus the present method deviates significantly from the method presented in JP53136007.

In EP00052334 a technique is presented, where carbonaceous materials are heated slowly to a conversion temperature of 200-600°C. The heating procedure is made at air exclusion conditions. The heating rates are specified to be from 5 to 30°C per minute. The products of the process are e. g. oil and carbon that may be used either for combustion or other purposes.

As possible catalysts phosphoric acid and phosphate are mentioned but not alkali or earth alkali metals. The invention made by ReaTech adds phosphorous components to a gasifica- tion or combustion process. Air exclusion is not necessary, the heating rate may be rapid and the maximum reactor temperature is above 500'C, where agglomeration and sintering may become a problem if the reactor is operated without additive.

[Janson et al. 1996] describes a phosphate-based pulping of agrofibre including papermak- ing and spent liquor recovery. Trisodiurnphosphate, Na3P04, is used as a pulping and bleaching chemical in papermaking. A regenerative process is described. It is claimed that after cleaning the phosphate spent liquors from silica, the spent liquor can, if necessary, be burned in fluidized bed or gasification plants. [Zevenhoven et al. 1999] states that in a pres- surized gasification of biomass, phosphates are always present as Ca3 (PO4) 2 with a high melting point of 1780°.

The invention by ReaTech does not involve the use of Na3PO4 as a bleaching chemical. It is not necessary to remove silicates from the process and phosphate is seen in several other forms than Ca3 (PO4) 2, in particular phosphates occur in the forms of potassium or sodium compounds. The phosphorous agents, in the invention by ReaTech, are added to the process in order to react with potassium, sodium and calcium compounds and hereby avoid sintering and agglomeration in the bed.

MODE FOR CARRYING OUT OF THE INVENTION The precise amount of added phosphorous said as phosphate depends on the precise process conditions, the fuel composition as well as the amount and composition of other additives and the specification of the quality of the residual product. Normally the amount of additive is minimized due to economic reasons. Sufficient amounts are however such amounts that introduces enough phosphorous to react with most alkali components in the process. Simple stoichiometric relations can also be utilized in combination with the valuable operational experience that is obtained from running full-scale reactors. The maximum needed amounts of moles total phosphorous added to the process necessary to prevent agglomeration and sin- tering will typically be equal to the sum of the molar contents of the alkali metals and the earth alkali metals introduced to the reaction zone. In simple cases the maximum amount is equivalent to the molar amounts of alkali and earth alkali metals inherent in the fuel. In most cases half or less of this amount is sufficient. In specific cases the amount, type and form of other additives or bed material must be considered. An estimate of the needed amount can be calculated using an equilibrium program like HSC, Roine [1997]. HSC calculates equilibrium compositions using a minimization method for Gibbs free energy and use a database based on thermochemical data like Barin [1995] and Knacke et al. [1991]. Other equilibrium pro- grams are Chemsage and FACT. These programs can together wdth process knowledae be used to estimate the needed amount of additive to the process.

Phosphor addition in gasification Reference cited U. S. PATENT DOCUMENTS Jul. 23/1996. Sudhakar et al.

4,458,095 Jul. 3,1984. Wingfield et al.

JAPANESE PATENT DOCUMENTS JP52042806, (IshI-N) IshII Works Co. LTD.

JP58167682, Asahi Chem. Ind. Co Ltd.

JP54151585, Matsushita Elec Ind Co LTD.

JP2258067, Nishi Nihon Trust K.

JP56070875, Matsushita Elec. Ind. Co. LTD.

JP53136007, Hankona LTD.

EUROPEAN PATENT DOCUMENTS EP 000 52 334 A2, B 1 and B2.

OTHER PUBLICATIONS Levin E. M., Robbins C. R., McMurdie H. F. Fifth. Printing [1985]. Phase Diagrams for Ceramist, Vol. I, 1964.

Roine A.. HSC ChemistryX for Windows [1997]. Chemical Reaction and Equilibrium Software with extensive Thermochemical Database.

Barin I. [1995]. Thermochemical Data of Pure Substances, Third edition, Weinheim, Germany.

Knacke O., Kubaschewski, Hesselmann K. [1991]. Thermochemical Properties of inorganic Substances, Second Edition. Springer-Verlag Berlin, Heidelberg, Germany.

Janson, J. and Jousimaa, T. [1996]. Nordic Pulp and Paper Research Journal 1,4-14.

Skrifvars B.-J., Sfiris G., Backman R., Widegren-Dafgård K., Hupa M. [1997]. Ash Behavior in a CFB Boiler during Combustion of Salix, Energy & Fuels 11,843-848.

Skrifvars B.-J. [1994]. Sintering tendency of fuel ashes in combustion and gasification conditions. Doctoral Thesis, Abo Akademi University, Abo/Turku, Finland.

Zevenhoven-Onderwater M., Skrifvars B.-J., Backman R., Hupa M. [1999]. Nordic Workshop on Ash Chemistry, Properties and Behavior, June 3-4, Gothenburg, Sweden.

Jimmy Bak [1999], Riso National Laboratory, Denmark (personal communication).

Poul Norby [1999], University of Oslo, Nor vay (personal communication).