SK282498B6 - Method of disposal of modified organic waste by combusting in cement rotary furnaces - Google Patents

Abstract

A method of disposing of treated organic waste, in particular meat-and-bone meal, waste fats and other processed veterinary waste of animal origin by incineration in a cement rotary kiln, which is heated during the clinker firing process with noble fuel or a mixture of noble fuels or a mixture containing alternatives. This waste is added to the cement rotary kiln either via the main burner and / or the calcination burner directly to the flame, and / or via the auxiliary burner to the flame with temperatures of 1900 to 2000 ° C, and / or to the hot part of the rotary kiln with temperatures of 1400 to 1900. ° C. In this method, part of the energy content of the noble fuel or mixture of noble fuels, or the mixture containing noble and alternative fuels, is replaced by meat-and-bone meal, waste fat and / or other treated animal waste in any selected ratio up to a maximum of 90%. and an oxidizing furnace atmosphere in excess combustion air is burned using their thermal energy. Non-toxic flue gases after perfect thermal destruction are partially trapped in countercurrent firing on the ground raw material mixture and the formation of clinker and ash formed from bone minerals by combustion quantitatively reacts into the clinker mass with P205 mineralizing effect to form clinker phases up to 2% P2O5 in clinker. The added treated organic waste has a min. calorific value 11 MJ.kg-1 and contain max. 50% ash with max. humidity 50% .à

Description

Technical field

The invention relates to a process for the disposal of treated organic waste by incineration in cement rotary kilns, in particular meat-bone meal, fats and other processed veterinary waste of animal origin.

BACKGROUND OF THE INVENTION

The disposal of hazardous, biologically contaminated organic substrates, banned for inclusion in the food chain and for human production, is now highly topical. Waste of animal origin is processed in sanitation institutes known as rendering plants for meat-bone meal and animal fats, resp. other products. Large quantities of these wastes in the form of bone and viscera are the products of the meat processing industry, as bones make up about one fifth of the animal's weight. Dead animals infected with various diseases, including the now highly problematic BSE disease, known as mad cow disease, also represent a significant group of hazardous wastes.

BSE - bovine spongiform encephalopathy was caused by the feeding of infected meat-bone meal in compound feed containing pathological protein particles - prions, which was administered to bovine animals as a major protein source without prior high-temperature processing. Pathological prions cause serious neurodegenerative diseases in humans, known as a new variant of Creutzfeldt-Jacob disease, and in animals known as BSE (bovine spongiform encephalopathy) - mad cow disease and TSE (transmissible spongiform encephalopathy) known as scrapie. Prion diseases have been identified in 20 animal species including humans. The immune system is unable to recognize infectious prions and the disease is spreading uncontrollably through the organism resulting in brain degeneration and death. In the case of livestock, the whole herd must be destroyed when this disease is detected.

Today, there is no effective medicine or preventive vaccination against these diseases, prions are very resistant, survive in the external environment and are difficult to dispose of with conventional disinfectants. The only possible protection against the spread of these diseases is the destruction of meat-bone meal from hazardous animal waste by incineration.

In conditions of common municipal waste incineration plants, where the temperature reaches 700 - 900 ° C, max. 1200 ° C, there is a danger of incomplete combustion of organic carbon of meat-bone meal and there is also a problem of waste ash utilization. The energy potential contained in the meal is not utilized in conventional combustion chambers. The disposal of flesh-and-bone meal by improperly selected technology may cause additional environmental problems associated with incomplete combustion, which could result in the formation of toxic flue gases containing CO, carbon black, organic pyrolysis compounds, dioxins, furans, HCN under H ₂ S reducing conditions and the presence of additional addition halogenated organic compounds that are a major environmental burden.

The perfect combustion of organic waste should result in flue gases containing CO ₂ , SO ₂ , NO _X , H ₂ O, hydrogen halides and harmless ash.

Several patents address the problem of the disposal of hazardous bio-waste by combustion in combustion chambers of different designs. Wastes are e.g. burnt on the grate furnaces according to the published international application WO 9500804, respectively in the fluidized bed according to CS AO 214859, SK 278 599, DE 4414579, in the form of various pellets according to US 5,001,993, or of various lump, liquid and resp. gaseous waste according to FR 2 661 734, in combustion plants in various design variants EP 0751347, WO 9626021, US 3782301. However, these patented solutions do not disclose methods for the disposal of ashes resulting from the incineration of infectious animal waste and also do not exploit the energy potential generated by incineration waste.

Combustion of animal bones in a suitably treated apparatus, at temperatures of about 650 ° C, is dealt with in US Patent 4,000,705 to form ash and volatile hydrocarbons that can be either condensed, released into the atmosphere, or burned.

The use of meat-bone meal as an additional fuel for the fluidized-bed combustion of mechanically dehydrated sewage at temperatures of 850 to 1150 ° C is disclosed in published international patent application WO 995230.

High-temperature high-capacity incineration of hazardous wastes in blast furnaces where the temperature of the bottom of the furnace reaches about 2000 ° C is described in CZ patent 284 954. The wastes are added to the furnace charge and dosed into the furnace from above. blast furnace gas. Partial melting of the charge, development of blast furnace gas, pyrolysis and formation of pyrolysis fumes occur. The blast furnace gas contaminated with the fumes is discharged to a second blast furnace for combustion. The disadvantage of this solution is that the finely grained contaminated material can be caused by e.g. In case of malfunctions, pyrolysis products can escape into the atmosphere, gaseous SO ₂ , HCl, HF are not captured and as blast furnace slag is produced as natural waste of the iron production technology.

Combustion of solid combustible wastes in the form of pellets as a supplementary fuel in a cement rotary kiln is disclosed in US Patent 5,724,899. Pellets are fed into the furnace by a special device located on the furnace shell and burn almost before entering the rappel zone, forming a secondary furnace within cement rotary kiln. In this way, however, there is a risk of contamination of dust from the cement rotary kiln with non-combusted fine contaminated material resulting from the decomposition of the burning pellets and entrained flue gases with high flow rates, since the pellets are not dosed to the highest temperatures in the melt zone of the furnace. practically impossible due to high temperatures and stickers.

EP 0501944 discloses the use of preheated waste air from refrigeration industrial equipment, such as a cement clinker cooler, for the combustion of bio-waste, but it also does not address the problem of ash formation.

The disadvantage of the prior art in the field of disposal of bio-waste, especially such as meat-bone meal and other processed animal substrates, is generally their inefficient ecological and economical disposal by incineration in conventional combustion chambers where there is a possibility of toxic fumes by incomplete combustion. economical use of their energy content and the resulting problem associated with the use, respectively. the disposal of ash from incinerated infectious waste.

SK 282498 Β6

The object of the present invention is the safe, hygienic, ecological, waste-free and economical disposal of meat-bone meal and other processed animal waste from rendering plants with a possible microbiological infectious negative effect on living organisms by burning as an alternative fuel in rotary cement kilns.

SUMMARY OF THE INVENTION

This objective is achieved by the disposal of treated organic wastes, in particular meat-bone meal, waste fats and other processed veterinary wastes of animal origin by incineration in a cement-fired rotary kiln heated by the noble fuel clinker firing process, where these wastes are added to the cement rotary kiln a main burner and / or a calcination burner directly into the flame and / or through the auxiliary burner to a flame at temperatures of 1900 to 2000 ° C, and / or to the hot part of the rotary kiln at temperatures of 1400 to 1900 ° C, that part of the energy content of a noble fuel or a mixture of noble fuels, or a mixture containing noble and alternative fuels, is replaced by meat-bone meal, waste fat and / or other processed animal waste in any chosen ratio up to 90% in the furnace atmosphere in the excess of combustion air burn out using their thermal energy. Non-toxic flue gases after perfect thermal destruction are partly captured by countercurrent firing on the ground raw material mixture and the clinker forming and ash formed from bone minerals by combustion quantitatively reacts to the clinker mass with the mineralizing effect of P ₂ O ₅ to produce 2% oxide clinker phosphorus P ₂ O ₅ in clinker, obtained from ash from meat-bone meal, resp. bones containing organic waste at firing, preferably maintaining the level of P ₂ O ₅ in the clinker at a level of up to 0.5%. The treated treated organic wastes added have a minimum calorific value of 11 MJ.kg ^-1 , preferably above 20 MJ.kg ^-1, and contain at most 50 wt. ash with a maximum humidity of 50%, preferably below 10%.

Advantages also include that part of the energy content of the noble fuel or of the mixture of noble fuels or of the mixture containing noble and alternative fuels is replaced by a meat-bone meal of max. up to 40%, preferably up to 10%, or waste grease up to max. 90%, preferably 30%.

At high temperatures achieved by clinker burning in an oxidizing atmosphere in excess air and a sufficiently long residence time of flue gases and fired material in a cement rotary kiln, complete high-temperature destruction of all organic substances occurs without the possibility of toxic flue gases.

The countercurrent flow of material and flue gas and their sufficiently long residence time in the cement rotary kiln - heat exchanger system ensures the binding of gaseous acidic compounds of chlorine, flora and sulfur to the alkaline raw material mixture to form alkaline compounds which then bind into the resulting clinker structure in the firing process.

The combustion results in non-toxic flue gases containing carbon dioxide CO ₂ , nitrogen oxides NO _X , water vapor H ₂ O, and oxygen O ₂ and with a reduced content of sulfur dioxide SO ₂ and hydrogen halides. High combustion temperatures, sufficiently long exposure, perfect destruction of organic substances, their oxidation in excess of O ₂ and the overall technological arrangement of the cement rotary kiln do not allow the re-generation of toxic flue gases containing dangerous dioxins, furans and other organic compounds as observed in conventional waste incineration plants.

An important advantage of the combustion of organic substrates of animal origin, in particular meat-bone meal and bone-containing waste in cement kilns, is the immediate disposal of the ash produced by its quantitative incorporation into the clinker phase structure by chemical reactions and physical processes, becoming an integral part thereof.

One of the significant advantages of burning meat-bone meal and other organic waste, especially processed animal waste of animal origin with min. calorific value 11 MJ / kg, max. 50% and with an ash content of max. 50%, such as e.g. waste animal fats from the risk group of animals is the saving of expensive noble fuels commonly used in cement technology (natural gas, fuel oils, coal). These wastes are used as alternative fuels to a specified extent so that the technological process during the clinker burning is not adversely affected and the overall quality of the cement produced is closely related. For meat-bone meal, it is a substitute of noble fuel in the range of up to 40%, usually up to 5%, in waste fat the range is wider and with suitable burner adjustments even higher waste fat dosing is possible than 70% whereas fat has a comparable calorific value to that of a noble fuel and practically zero ash content.

It may also be advantageous to use a mixture of meat-bone meal and waste animal fat, which is a well-transportable suspension, as an alternative fuel for firing clinker.

The limiting factor of the amount of meat-bone meal used as an alternative fuel in cement clinker firing is the content of phosphorus oxide P ₂ O ₃ in ash and consequently also in clinker. The amounts of P ₂ O ₅ in the clinker are at trace levels of up to 1.5%, typically 0.05 to 0.25%. Concentrations above 0.5% can sometimes cause serious quality problems and reduce cement strengths, especially at an earlier stage. Additions of P ₂ O ₅ over 0.5% stabilize dicalcium silicate C ₂ S at the expense of tricalcium silicate C ₃ S, which is the most important clinker material in terms of strength, or decompose tricalcium silicate C ₃ S into dicalcium silicate C ₂ S and calcium oxide CaO. Concentrations of up to 0.5% phosphorus oxide P ₂ O ₅ significantly increase initial strength (due to increased hydraulically C ₃ S), up to 2% phosphorus oxide P ₂ O ₅ satisfactory cement strengths, higher concentrations above 2% strength. The amount of P ₂ O ₅ in the clinker up to 2% has a mineralizing effect on the overall clinker-forming process and improves the grinding capacity of the clinker.

The variability of the ash composition does not require extraordinary measures for homogenizing meat-bone meal or other processed organic waste of animal origin. The composition of the ash does not require chemical changes, resp. only minimal corrections of the chemical composition to the CaO content in the preparation of the raw material mixture.

The perfect incineration of animal waste to non-toxic flue gases and the quantitative incorporation of ash into the clinker structure does not require the continuous monitoring and control of the generated fumes.

Overview of the figures in the drawing

BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in more detail with reference to the drawing, in which: 1 is a diagrammatic illustration of a cement rotary kiln for carrying out the process of disposing of treated organic waste according to the invention based on Example 2.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

In a cement kiln rotary kiln 1 with an output of 1700 t clinker per day, waste meat-bone meal was burned in an amount of up to 5% of the energy content of the noble fuel (natural gas with a calorific value of 33.5 MJ.nf ³ ). The meat-bone meal was fed through the main burner 4 into the flame, where it was completely thermally destroyed. In clinker, an increase in P ₂ O ₅ from the original 0.15% to 0.4% P ₂ O ₅ was observed. During firing an increase in hourly output by about 3% was observed. The cement obtained by grinding the clinker and the solidification regulator thus showed no deviation from the norm properties, the cement leaches did not contain increased amounts of heavy metals. The flue gas after the heat exchanger contained no toxic compounds and no dust from the burned organic substrates was identified in the dust collectors.

Example 2

In a cement kiln rotary kiln 1 with a precalciner channel 2 with an output of 1700 t clinker per day, animal waste from rendering was burned up to 30% of the energy content of the noble fuel (heavy fuel oil with a calorific value of 40 MJ.kg ^-1 ). The preheated mixture of animal animal fat and heavy fuel oil was fed through a calcining burner 5 into a flame in the precalciner channel 2 between the heat exchanger 3 and the rotary kiln 1 where it was completely thermally destroyed. No decrease in performance and no technological problems were observed. The cement obtained by grinding the clinker and the solidification regulator thus showed no deviation from the norm properties, the cement leaches did not contain increased amounts of heavy metals. The flue gases after the heat exchanger contained no toxic compounds.

Example 3

In a cement kiln rotary kiln 1 with an output of 1700 t of clinker per day, a mixture of meat-bone meal and animal animal waste in a weight ratio of 1: 1 in an amount of up to 200 kg per hour was burned. The preheated mixture was fed via an auxiliary burner 6 to the hot portion of the rotary kiln saline zone where it was completely thermally destroyed. In clinker, an increase in P ₂ O ₅ from the original 0.15% to 0.18% P ₂ Os was observed. The cement obtained by grinding the clinker and the solidification regulator thus showed no deviation from the norm properties, the cement leaches did not contain increased amounts of heavy metals. The flue gas after the heat exchanger contained no toxic compounds and no dust from the burned organic substrates was identified in the dust collectors.

The examples given are illustrative only and do not exhaust all the possible uses of treated organic wastes, in particular of animal origin, as alternative fuels.

Industrial usability

The process according to the invention is primarily concerned with the disposal of meat-bone meal, waste fats and other organic substrates from rendering plants. The process of disposing of treated organic waste by incineration, in particular meat-bone meal and other processed veterinary waste of animal origin in cement kilns, provides reliable and waste-free disposal of such waste.

Claims (3)

PATENT CLAIMS 1. A method of disposing of treated organic waste by incineration in cement kilns, in particular meat-bone meal, waste fats and other processed veterinary waste of animal origin, which is heated in the process of burning clinker with a noble fuel or a mixture of noble fuels or a mixture containing nobles , wherein these wastes are added to the cement kiln either through the main burner and / or the calcination burner directly into the flame, and / or through the auxiliary burner into the flame at temperatures of 1900 to 2000 ° C, and / or into the hot part of the rotary kiln. temperatures of 1400 to 1900 ° C, characterized in that part of the energy content of the noble fuel or of the mixture of noble fuels or of the mixture containing noble and alternative fuels is replaced by meat-bone meal, waste fat and / or other processed animal waste m of the selected ratio up to a maximum of 90%, which at high temperatures and oxidizing furnace atmosphere burn out in excess of combustion air using their thermal energy, while non-toxic flue gases after perfect thermal destruction are partially captured in countercurrent firing on milled raw material mixture and clinker ash formed from bone minerals by burning, reacts quantitatively into the clinker mass with the mineralizing effect of P ₂ O ₅ phosphorus oxide on the formation of clinker phases up to a content of 2% of phosphorus oxide in clinker, obtained from ash from meat-bone meal, resp. bone containing organic waste during firing, with the added modified organic waste having a minimum calorific value of 11 MJ.kg ^'1 and containing at most 50% by weight. ash with a maximum humidity of 50%. Method according to claim 1, characterized in that part of the energy content of the noble fuel or of the mixture of noble fuels or of the mixture containing noble and alternative fuels is replaced by a meat-bone meal of max. up to 40%. Method according to claim 1, characterized in that part of the energy content of the noble fuel or of the mixture of noble fuels, or of the mixture containing noble and alternative fuels, is replaced by waste grease to a height of max. 90%.