WO2001036570A1

WO2001036570A1 - FUEL OILS PROVIDING EXHAUST GASES WITH LOW NOx CONTENTS WHEN COMBUSTED

Info

Publication number: WO2001036570A1
Application number: PCT/HU1999/000078
Authority: WO
Inventors: András Bertha; Levente Fülöp; Béla PINTÉR; Péter PÁLFI
Original assignee: Bertha Andras; Fueloep Levente; Pinter Bela; Palfi Peter
Priority date: 1999-11-17
Filing date: 1999-11-17
Publication date: 2001-05-25
Also published as: AU1578100A

Abstract

The invention relates to fuel oils which can be combusted in environmentally sound manner. The primary aim of the invention is to provide fuel oils which, when combusted, provide exhaust gases with low NOx contents. The fuel oil according to the invention comprises up to 40 % by weight of water optionally together with one or more conventional additive(s) in a total amount of up to 15 % by weight. The fuel oil according to the invention also comprises as a further component at least one NOx emission lowering carbamic acid derivative, which is urea, biuret, semicarbazide, a carbamate salt and/or a C1-C10 alkyl urethane, in an amount of 0.1-2.5 % by weight.

Description

FUEL OILS PROVIDING EXHAUST GASES WITH LOW NO_x CONTENTS WHEN

COMBUSTED

The invention relates to fuel oils which can be combusted in environmentally sound manner The primary aim of the invention is to provide fuel oils which, when combusted, provide exhaust gases with low NO_x contents

The term "fuel oil", as used in the present description and claims, covers the full scale of combustible oils of mineral, plant and animal origin, including their semi- synthetic and synthetic variants, too Such fuel oils are e g liquid and semisolid distillation products of mineral oil (such as gasoline, Diesel oil, fuel oil, residual asphalt and black oil) comprising various hydrocarbons as main components, oils and fats of plant and animal origin comprising various fatty acid esters as main components, furthermore synthetic or semisynthetic liquid or semisolid materials and residues comprising various hydrocarbons and/or derivatives of higher hydrocarbons as main components From the aspects of the present application liquid or semisolid wastes comprising various combustible components (such as spent oil wastes of food industry and the like, further on combustible industrial wastes) which can be used, either alone or in admixture with non-waste fuel oils to produce energy by combustion are also regarded as fuel oils

The term "combustion" is also used in a broad sense, this term covers both combustion in an internal combustion engine and combustion in a heating equipment Thus the term "fuel oil also covers fuels used to drive internal combustion engines of motor venicles

Numerous efforts have been made for a long time to utilize combustible industrial wastes for energy production which has several benefits from the aspects of energy saving and environment protection. Two basic problems have been emerged in this field, which can be regarded nowadays as more or less solved.

One of these problems arises from the water content of the waste to be combusted These aqueous wastes are frequently not sufficiently stable even as formed, and their stability impairs further when admixing them with non-waste fuel oils. To overcome the problems arising from instability, basically two methods have been elaborated: in one of them a water/oil emulsion with prolonged stability is formed by using appropriate emusifying agents (see e.g. JP 59202294, US 4158551 , HU 181331 and references cited therein); whereas according to the other one oil and water (or aqueous oil) are(is) fed into a burner head equipped with a specific homo- genizer, and the emulsion formed there is combusted practically at the rate of its formation ("on-line technique", see e.g. Industriefeuering 22. 12-13 /1982/) This latter method can also be performed with emulsions of low stability, which can be formed either by using an added emulsifyer, or by utilizing the emulsifying effects of certain substances which are already present in the fuel or which form therein spontaneously upon combustion (see e.g. HU 214223, HU 202908 and references cited therein)

The second problem to be solved is to reduce the amounts of corrosive and/or pollutant materials which form upon combustion. For this purpose various water-soluble and/or oil-soluble salts, such as salts of metals belonging to Groups I, II and VIII of the Periodic System, manganese salts and ammonium salts, have been used (see e g HU 203573 and references cited therein). As disclosed in HU 203573. both corrosion damages and soot and S0₂ contents of exhaust gases can be suppressed considerably when oil-soluble salts are used together with water- soluble salts Water with a hardness exceeding 10° (German scale) can also be used as a source of water-soluble salts

Of course, the above methods, which have been elaborated primarily for the utilization of wastes, can also be applied with good results for non-waste fuels comprising water and/or environmentally detrimental substances

Up to now, less attention has been paid to reduce NO_x contents of exhaust gases formed from fuel oils when combusted, although the increasingly severe requirements of environmental protection prescribe now to reduce this value, too It has been mentioned in US 51561 14, which discloses carbonaceous fuels for internal combustion engines comprising 20-80 % by volume of water, that NO_x emission can even be completely eliminated when the fuel comprises a sufficiently high amount of water This phenomenon can be attributed to the cooling effect of the high amount of water present, which cools the temperature in the burning chamber below the critical temperature of NO_x formation However, it is frequently not desirable to raise water content above a certain level It is particularly true for fuel oils to be used for heating purposes where, just as a consequence of this cooling effect, a well observable decrease in burning efficiency and caloric value occurs even when water content is raised above some percents

The invention is based on the recognition that certain derivatives of carbamic acid (NH^-COOH), more particularly urea (carbamic acid amide), biuret (carbamyl urea) semicarbazide (carbamic acid hydrazide) carbamate salts and C1 -C10 alkyl urethanes (C1 -C10 alkyl esters of carbamic acid) are suitable to decrease considerably the NO_x contents of exhaust gases formed from fuel oils upon combustion

Thus, the invention relates to a fuel oil comprising up to 40 % by weight of water optionally together with one or more conventional addιtve(s) in a total amount of up to 15 % by weight The fuel oil according to the invention also comprises, as a further component, at least one NO_x emission lowering carbamic acid derivative, which is urea, biuret, semicarbazide, a carbamate salt and/or a C1 -C10 alkyl urethane in an amount of 0 1-2 5 % by weight

Depending on the solubιlιty(ιes) of the compound(s) concerned the fuel oil may comprise the NO_x emission-lowering carbamic acid derιvatιve(s) in either of the aqueous and oily phases The water-soluble compounds are added to the fuel oil preferably as a solution formed with its water content

In this specification the percentages by weight always relate to the total weight of the composition concerned

The lower limit of water content of the fuel oils according to the invention depends primarily on their intended use When the fuel oil is to be combusted by online technique the lower limit of water content may be low, such as even 2 % by weight As known according to the on-line technique the oily components of fuel oil are admixed with the aqueous component(s) just in the burner head thus it is the burner head itself where the fuel oil with the composition according to the invention is formed The upper limit of water content of fuel oils to be combusted by on-line technique may be the usual value, generally about 25 % by weight The same relates to fuel oils to be combusted shortly after their formation

It is however more appropriate to provide fuel oils in the form of transportable storable and directly combustible water/oil mixtures In such instances the lower limit of their water content may be higher typically 5-10 % by weight whereas the upper limit may be 40 % by weight as given above For fuel oils comprising a heavily viscous substance or a semisolid substance which solidifies easily at lower temperatures ( such as black oil or residual asphalt) the adjustion of water content above 10 % by weight runs with the further advantage that viscosity and pour point decrease considerably, which is very favourable from the aspects of transporting, storage and use

In both instances the water content of fuel oil may originate from added water and/or from the water content of combustible industrial waste

Emulsifying agents form one of the typical groups of conventional additives of fuel oils In some instances, such as when the fuel oil comprises protein-containing wastes of food industry as combustible industrial waste and the fuel oil is to be combusted by on-line technique (see e g HU 202908) no added emulsifying agent is required, however, in most of the cases the required stability of the aqueous fuel oil is provided for by admixing it with added emulsifying agent(s) Any of the emulsifying agents applied for this purpose, such as those disclosed in the references cited above, can be utilized either alone or in combination with one another Particular representatives of emulsifying agents are as follows alkali metal, alkaline earth metal and ammonium soaps, fatty alcohol sulphonates and naphthenates, invert soaps, fatty acid esters of mono- or polyhydroxylic fatty alcohols polyalkylene glycol ethers and esters, and polyalkylene glycol sorbitane fatty acid esters Particularly preferred representatives of emulsifying agents are those formed from coco fatty acids, such as coco fatty acid amides, succinic amides furthermore amides of other fatty acids with at least 8 carbon atoms When the fuel oil according to the invention also comprises an emulsifying agent its amount may be typically 0 5-8 % by weight preferably 1 -6 % by weight

The emulsifying agent is introduced into fuel oils preferably as a solution formed with their water content One may be proceed e g in such a way that the emulsifying agent is dissolved in water or in a combustible aqueous industrial waste the water-immiscible components of the fuel oil are admixed with this solution, and then, if desired, the water content of the fuel oil is adjusted to the required final value by adding more water or aqueous industrial waste. If more than one emulsifying agents are used, they are dissolved preferably in the order of increasing HLB values.

Substances for reducing corrosion and/or soot and S0₂ emission form a second group of the typical additives. As mentioned above, typical representatives of such substances are oil-soluble and water-soluble metal salts and water-soluble ammonium salts. Of the metal salts those of metals belonging to Groups I and II of the Periodic System are preferred. In some instances, such as when various spent oils, wastes of metal processing and/or hard water are utilized, the required metal salts may already be present in the oily and/or aqueous phase, whereas in other instances salts should be added to the respective phases, preferably before admixing the aqueous and oily phases. Water-soluble salts can also be introduced as a solution formed with the aqueous solution of the emulsifying agent discussed above Although it is obvious for one skilled in the art, it should be noted here that metal salts having corrosive and/or environment-polluting anions (such as halide ions) must not be added to the fuel oil. Preferred representatives of the anions are those listed in HU 203573 In the context of the present specification metal oxides and hydroxides are also regarded as metal salts. When the fuel oil comprises such salts their amount may be typically 0 2-5 % by weight, preferably 0 5-2 5 % by weight It should be noted that when the fuel oil is sulphur-free, as it is the case with non-waste oils of plant origin, it is not always necessary to use such salts.

Further examples of conventional additives are substances for improving combustion (metal salts discussed in the previous paragraph may also serve for this purpose) and biological preservatives, such as bactericidal and bactenostatic agents, e g those mentioned in HU 202908 The latter should be used preferably when the fuel oil is or comprises a combustible waste from food industry, or when the fuel oil is to be stored for a prolonged period before combustion When the fuel oil comprises one or more of such further conventional additives, their total amount may be gener-ally 0 1-2 % by weight, preferably 0 2-1 % by weight

The fuel oils of the present invention differ from the known ones basically in that they comprise at least one NO_x emission lowering carbamic acid derivative Of the NO_x emission lowering carbamic acid derivatives listed above urea and carbamate salts proved to be the preferred ones Carbamate salts may be both organic and inorganic salts, the salt-forming cation may be preferably a cation of a metal belonging to Group I, II and/or VIII of the Periodic System

The total amount of NO_x emission lowering carbamic acid derivatives present in the fuel oil of the invention may be preferably 0 5-1 5 % by weight, particularly about 1 % by weight

NO_x emission lowering carbamic acid derivatives are introduced into the fuel oil preferably as a solution formed with its water content in a similar way as it has been disclosed above for the introduction of emulsifying agents

The invention also relates to an aqueous solution for preparing a fuel oil with a composition according to the invention said aqueous solution comprising 0 1-2 5 units by weight of a NO_x emission lowering carbamic acid derivative as defined above optionally together with 0 5-8 units by weight of an emulsifying agent and/or 0 2-5 units by weight of a soot and SO_? emission lowering water-soluble metal and/or ammonium salt, and/or 0 1 -2 units by weight of one or more other conventional addιtιve(s) of fuel oils Here the term unit by weight" does not refer to the percentage composition of the aqueous solution, but it refers to weight units which lead to the final concentrations expressed above in % by weights when the fuel oil to be combusted has been made by utilizing the aqueous solution These aqueous solutions preferably contain all of the necessary water-soluble additives in a single common solution As discussed above, hard water (i e water with a German degree of hardness above 10°, preferably above 20°) may also be used as a source for at least a part of the metal salts, thus it is preferred to use such hard water for the preparation of the aqueous solutions These aqueous solutions can be used for supplementing fuel oils which, in their starting state, are free of water or contain less water than that required

Further details of the invention are given below in the following non-limiting Examples

Example 1

5 kg of sodium carbonate, 3 kg of sodium hydrocarbonate and 5 kg of urea were dissolved at room temperature in 100 kg of tap water with a German degree of hardness of 23' 0 05 kg of hexachloroprene and 0 1 kg of methyl-p-oxy-benzoate were dissolved then in the solution, and subsequently 10 kg of coco fatty amide 5 kg of a mixture of aliphatic fatty amides with at least 8 carbon atoms 34 kg of polyethylene glycol sorbitane lauryl ester and 4 kg of sodium dodecyl sulphosuccinate were added to the solution under constant stirring The resulting concentrate was added to 632 95 kg of F100/200 black oil (pour point 50-60°C) preheated to 70' C and after 5-10 minutes of intense stirring further 200 kg of tap water of room temperature were added to the mixture A fuel oil with a pour point below 10⁽ C was obtained, which was easy to transport and could be stored at room temperature for at least 6 months without any change This fuel oil is referred to in the following as

fuel oil "A"

A fuel oil containing no urea but otherwise of the same composition as described above was also prepared for comparative tests In this fuel oil the amount of urea was supplemented by equal amount of black oil. This fuel oil is referred to in the following as fuel oil "B".

Black oil of the same type as given above was also tested for comparison This fuel oil is referred to in the following as fuel oil "C"

In the comparative tests the three fuel oils given above were combusted in a boiler equipped with a SAACKE SKJV 25 type jet nozzle, the boiler was operated at a loading of 50 % The fuel oil was injected at a pressure of 3 7 bars The pressure prevailing in the combustion chamber of the boiler was 2 6 bars for fuel oils "A" and "B", and 3 bars for fuel oil "C". The composition of the exhaust gases leaving the boiler was analysed with a Testotherm 33 type analyser The results, which are averages of three tests, are listed in Table 1

Table 1

Examined parameter Fuel oil "A" Fuel oil "B" Fuel oil "C"

Burning efficiency (ξ) 88,7 88,9 90,2

Temperature of ex202 202 206 haust gas, ^C C

Composition of exhaust gas

NO_x, mg/m 370 612 625

SO,,, mg/m³ 1261 1721 3200

CO, mg/m³ 160 143 206 co₂, % 10,9 11,1 12,8 o_?, % 6,5 6,2 4,0 The following can be seen from the data of Table 1 Although the burning efficiencies of emulsion fuel oils (fuel oils "A" and "B") were lower than that of fuel oil "C", the decrease was slight, which means a considerable save in fuel, when the high (30 % by weight) water content of fuel oils "A" and "B" is taken into account As it was to be expected on the basis of the literature, fuel oils "A" and "B" provided exhaust gases with decreased SO^ CO and C0₂ contents, the decrease in SO, content was particularly remarkable For fuel oil "B" there was only a slight change in the NO_x content of the exhaust gas which, when compared to the data for burning efficiency, means that the water content was insufficient to cool the combustion chamber to a temperature below the critical temperature of NO_x formation With fuel oil "A" the NO_x content of the exhaust gas dropped approximately to the half which can be attributed clearly to the effect of urea added to the fuel oil

Example 2

5 kg of calcium carbonate and 3 kg of calcium hydrogen phosphate were dissolved at 80 C in 80 kg of tap water with a German degree of hardness of 23 5 kg of urea were dissolved then in the solution, and subsequently 3 kg of a coco fatty acid-based emulsifyei 2 kg of succinic amide formed from pπmarv secondarv and te-tiary amines 10 kg of a coco fatty amide/polyethylene glycol ether mixture and 3 kg of sodium dodecyl sulphosuccinate were added to the solution under constant stirring The resulting solution was added to 889 kg of F 100/200 type heavy fuel oil preheated to 70 C and the mixture is intensely stirred for 5-10 minutes A fuel oil for direct combustion in burner head was obtained, for which viscositv lowering and prolonged storabi ty were not required When testing this fuel oil as disclosed in Example 1 , similar results were obtained as indicated there for fuel oil "A".

Claims

What we claim is

1 A fuel oil comprising up to 40 % by weight of water optionally together with one or more conventional addιtιve(s) in a total amount of up to 15 % by weight which comprises as a further component at least one NO_x emission lowering carbamic acid derivative which is urea, biuret, semicarbazide, a carbamate salt and/or a C1 -C10 alkyl urethane in an amount of 0 1 -2 5 % by weight

2 A fuel oil as claimed in claim 1 , wherein the NO_x emission lowering carbamic acid derivative is dissolved in the water content of the fuel oil

3 A fuel oil as claimed in claim 1 or 2, which comprises 0 5-1 5 % by weight of an NO_x emission lowering carbamic acid derivative

4 A fuel oil as claimed in any of claims 1-3, wherein the NO_x emission lowering carbamic acid derivative is urea and/or a carbamate salt formed with a metal ion belonging to Group I, II or VIII of the Periodic System

5 A fuel oil as claimed in any of claims 1 -4, which comprises as conventional additive one or more emulsifying agent(s)

6 A fuel oil as claimed in claim 5 which comprises 0 5-8 by weight of emulsifying agent

7 A fuel oil as claimed in claim 5 or 6, which comprises as emulsifying agent a coco fatty acid amide a succinic amide and/or an amide of a fatty acid of at least 8 carbon atoms

8 A fuel oil as claimed in any of claims 1 -7 which comprises as conventional additive an oil soluble metal salt and/or a water soluble metal salt and/or a water soluble ammonium salt in an amount of 0 2-5 % by weight 9 A fuel oil as claimed in any of claims 1 -8, which comprises as conventional additive one or more combustion improving agent(s) and/or one or more biological preservatιve(s) in a total amount of 0 1-2 % by weight

10 A fuel oil as claimed in any of claims 1 -9 for combustion by on-line technique, which comprises 2-25 % by weight of water

1 1 A fuel oil as claimed in any of claims 1 -9 as a storable composition, which comprises 5-40 % by weight of water and at least 1 % by weight of an emulsifyer

12 A fuel oil as claimed in any of claims 1 -1 1 , which comprises water with a German degree of hardness of at least 10°

13 An aqueous solution for preparing a fuel oil as claimed in any of claims 1 - -12, which comprises 0 1-2 5 units by weight of a NO_x emission lowering carbamic acid derivative, optionally together with 0 5-8 units by weight of an emulsifying agent, and/or 0 2-5 units by weight of a soot and SO, emission lowering water-soluble metal and/or ammonium salt, and/or 0 1 -2 units by weight of one or more conventional addιtιve(s) of fuel oil

14 A solution as claimed in claim 13 which comprises water with a German degree of hardness of at least 10°