its heating value. As a rule the proportions are CH 4, H 2 and CO. Table 3-1 lists their heating values.

Transcription

1 3. Energy Conversion 3.1 Heating vales The chemical enthalpy is converted into heat by the oxidation o the carbon and hydrogen contained in the el. I, in accordance with Figre 31, the gas is cooled to 0 C ater combstion, then the reslting water is present as liqid. The enthalpy converted in the process is denoted as gross heating vale H o (earlier designation pper heating vale). Ater the combstion the gas is drawn o with temperatres above dew point so that the water is vaporos. As a reslt the condensation enthalpy is not converted into heat. Then the converted chemical enthalpy o the el is denoted as net heating vale h (earlier designation lower heating vale). Both vales are ths dierentiated only by the proportion o the condensation enthalpy h H x h (31) 2 0 H O vap x H 2 O being the proportion o water in the gas. Table 31 lists the gross heating vales and the net heating vales or typical els. The vales or the ossil els represent average vales or ermany [3.1]. Hydrogen possesses the highest heating vale in relation to the mass. Here the dierence between gross heating vale and heating vale is the largest. This dierence is the greatest in the case o the ossil els; in natral gas 10%. In natral gas the heating vale depends comparatively more greatly on the composition. I this is known, then the heating vale can be calclated sing h x h (32) i i x i being the combstible proportion o gas and h i its heating vale. As a rle the proportions are CH 4, H 2 and CO. Table 31 lists their heating vales. In solid and liqid els the chemical bond type o the components is not known so that the heating vale mst always be determined experimentally. I the heating vale wold be calclated according to Eq. (32) rom the C and H mass raction o the composition given in Table 21, so too high heating vale reslts. Especially, i oxygen is inclded already in the el, as it is the case or example in methanol, then considerably higher vales reslt. The heating vales o liqid els vary by ± 3 % depending on the reerence given. The dierent densities o liqid els have to be taken into accont becase they are saled in volme (litre) and not in mass (kg). As a conseqence a litre o Diesel els contains abot 14 % more energy than a litre o Otto el. For black coal the heating vale depends on the composition, especially on the amont o volatile matter, and can vary by ± 8 % rom the given mean vale. Raw lignite coal has a low heating vale becase o the high content o liqid water. ignite dst, which has been dried, has conseqently a higher vale. This vale is lower than that or black coals becase o the content o oxygen (see table 21). The heating vale o woods depends on their kind and amont o water. In the table only approximate vales can be given. Remarkable is the low heating vale related to volme. Thereore, the energy transport is not so econonomic than that or coal and oil. The higher the heating vale o els the higher is also their air demand. Figre 32 shows the heating vale and the air demand or a lot o combstible matter. It can be seen that approximately a linear correlation exists. More and more els are sed which are separated

2 rom residals and waste. Their composition is mostly known. However, the heating vale can be determined and herewith the air demand can be estimated according Figre 32. Heating vales and energy consmption oten given in dierent nits. The transer o these nits is smmarized in Table 32. As briely described in part, the crde el mst be treated or se ater its extraction rom the earth. The treatment demands energy. I the energy or the transport and storage is added on, the socalled spply energy reslts. This is compiled or some els in Table 33. Other sorces speciy partly slightly deviating vales (±1% o the percentage o the heating vale). Sch spply energies are necessary to calclate the cmlative energy reqired in the scope o ecostdies. For natral gas and crde oil approximately 10% o the heating vale and or bitminos coal 5% is thereore reqired or provision. 3.2 Combstion as Temperatres Designations The gas ater combstion is designated as combstion gas and the temperatr as combstion temperatre respectively (Figre 33). In an adiabatic chamber the highest temperatre is obtained. For temperatres above 1800 C it has to be considered that in reason o eqilibrim the conversion is not complete. Than it is diered between the adiabatic combstion temperatre with and withot dissociation o gas components. I heat is emitted dring the combstion, or example throgh loss owing to nonadiabatic walls, then the temperatre o the gas lowing ot o the combstion chamber is called process gas temperatre. The gas released into the environment ater completely sed is designated as le gas and the accompanying temperatre as le gas temperatre. In accordance with Figre 33 the combstion with heat emission can be carried ot in one or two apparatse connected in a series. I the gas contains dst ater combstion, or example in the case o solid els or dst generating prodcts, then it is designated as a smoke gas. Only ater cleaning, then it is called a le gas Adiabatic Combstion Temperatre The combstion in an adiabatic chamber gives the highest temperatres o the gas. This adiabatic combstion temperatre ad reslts rom the energy balance or the adiabatic combstion chamber in accordance with Figre 32 (h + c ) + c c + h. (33) p p ad diss Energy is inserted with the mass low o el and air. The enthalpy c ed in with the el can be disregarded compared with the heating vale h. Exceptions are only hot lean gases. Energy lows ot with the mass o the combstion gas and with dissociation enthalpy o the not complete oxidized components. The ollowing applies to the dissociation enthalpy

3 h diss ~ ~ ~ x x... M ~h CO M ~h H 2 x M ~h OH CO + H + 2 OH + (34) CO H 2 OH h i being the dissociation enthalpies o the reactions sch as CO CO O 2 H + 2O H O2 H 2 O OH + H O 2 O + O and so orth. In Eq. (33) is c nd c p the speciic heat capacity o el and air respectively and cp mean spec. heat capacity o the combstion gas. is the The speciic heat capacity is temperatre dependent. Hence, corresponding with the deinition o the enthalpy, a mean vale mst be introdced in the balancing between the air and gas temperatres h c p ( ) d c ( ) p. (36) Conseqently the ollowing applies c p T 1 cp ( T) dt T T. (37) T Absolte temperatres being applied or the sake o expediency. The temperatre dependence o the speciic heat capacity o a gas component can in act be approximated very well by the power nction [Müller, 1968] c p ( T) c ( T ) ( T T ) n (38) p 0 0 Ths the ollowing reslts as the mean vale o a gas component c c p n+ 1 ( T) 1 (T T0 ) ( T ) n + 1 T T 1 p (39) The mean speciic heat capacity o the gas mixtre is obtained rom sm o the mass related speciic heat capacity o the individal components c p 1 x i cpi x~ i ρi cpi. (310) ρ Table 34 lists the speciic heat capacities with the accompanying exponents n and the densities or the most important gas components. Figre 34 shows the temperatre dependence o the speciic heat capacity o the combstion gas or typical els.

4 The ollowing applies to the mass lows M & and λ & (311) M ( 1 + λ ) +. (312) With these two eqations the ollowing reslts rom the energy balance (33) or the adiabatic combstion temperatre h h λ c diss p ad +. (313) ( 1+ λ ) cp cp 1+ λ cp Figre 35 shows the adiabatic combstion temperatre and the accompanying concentrations in the combstion with air preheated to 800 C. From this it is obvios that the maximm adiabatic combstion temperatre is not prodced at stoichiometric combstion (λ 1) bt when combstion is hypostoichiometric with approximately λ 0.9. In this case the converted enthalpy is in act lower than λ 1; the air demand is lower as well. The varios components reach their maximm concentrations at dierent excess air nmbers. Figre 36 speciies the inlence o the dissociation on the adiabatic combstion temperatre. The dissociation is not taken into accont in the pper temperatre proile. Thereore only the homogeneos water gas reaction eqation is taken into accont in the area o hypostoichiometric combstion. In this case the maximm vale reslts when λ 1. The dissociation o CO 2 and H 2 O is taken into accont in the average crve. In the lower crve additionally the dissociation o O 2 and H 2 is also taken into accont. It is obvios rom the igre that approximately above temperatres o 1800 C the dissociation exerts an inlence and that the dissociation o O 2 and H 2 can still be disregarded p to temperatres o approximately 2300 C. I the air is only slightly preheated, then the enthalpy o the air approximately 1 to 3 % o the heating vale. Then λ is only c p p ( 1 + λ ) cp λ c (314) can be approximately set. Thereore the ollowing enses or the adiabatic temperatre h h diss ad +. (315) (1 + λ ) cp cp The adiabatic temperatre is all the lower, the higher the excess air nmber is, and all the higher, the higher the air preheating and the higher the O 2 content o the combstion air and the lower the air demand ths is. Figre 37 shows the adiabatic temperatre or typical els. An adiabatic temperatre only slightly higher than in natral gas is prodced by el oil. By comparison coal possesses lower adiabatic temperatres. ean gases sch as top gas prodce only relative low adiabatic

5 temperatres. Ths these gases ignite and brn relatively poor, which is the reason why air is oten preheated in these cases. Figre 38 represents the inlence o the air preheating on the adiabatic combstion temperatre, again sing the example o natral gas. The higher the temperatre, the smaller is the inlence o the preheating air on the adiabatic combstion temperatre, since larger proportions dissociate. Finally Figre 39 represents the inlence o the O 2 enrichment o the air. The adiabatic combstion temperatre can already be increased considerably by relatively low oxygen enrichments Nonadiabatic Temperatre and Fle as Temperatre Heat losses across wall are always present in real combstion chambers. Normally combstion processes have excess air nmbers higher than 1.1 and heat loss. Thereore the temperatre o the gas is so low that dissociation can be neglected. The energy balance is as M & h + c c + Q& (316) p p e Q & e being the heat low o loss to environment. Using the approximation (314) the ollowing reslts or the temperatre o the gas h Q& e ( 1+ λ ) c p +. (317) I an eiciency o apparats h Q& e η a (318) h is introdced, the ollowing enses or the temperatre h η a +. (319) ( 1+ λ ) cp I the process gas emits the eective heat low Q &, then the energy balance is p e ( 1+ λ ) cpg g h + λ c Q& + Q& + (320) g then being the le gas temperatre. For the le gas temperatre the ollowing is obtained rom the above sing eqation (314) g h Q& Q& ( 1+ λ ) c e pg +. (321)

6 The level o the le gas temperatre ths depends on the heat emission and conseqently on the type o process. 3.3 Fel Demand Pyrotechnical Eiciency From the energy balance (320), the ollowing reslts as the el demand or the necessary heat low Q & o the process to be carried ot & e h (322) M 1 Q& + Q& ( 1+ λ ) cpg ( g e )/h when e is the environmental air temperatre. The speciic energy demand related to the prodct low M & is applied to compare processes h 1 h + Q& e ( 1+ λ ) cpg ( g e )/h (323) h being the prodct s speciic change o enthalpy in accordance with Q & M & h. (324) For the rating o iring plants the pyrotechnical eiciency η Q& + Q& h e (325) is introdced, which prodces the ratio o the emitted heat to el energy consmption. Using eqation (322) the ollowing is obtained ( 1+ λ ) c ( ) pg g e η 1. (326) h Figre 310 represents this eiciency or the two els, natral gas and heating oil. It is obvios that the eiciency is all the higher, the lower the le gas temperatre is and the more the excess air nmber approaches the stoichiometric vale. When le gas temperatres and excess air nmbers are eqal, the el oil has in act a somewhat higher pyrotechnical eiciency, in practice however, de to the acid dew point, higher le gas temperatres mst be maintained in el oil irings than in natral gas irings. The overall eiciency η ov Q& h (327)

7 is introdced or the rating o the proportion o the tilized heat to the expended el. Using eqation (318) the ollowing then enses or the overall eiciency η η η (328) ov a This is ths smaller than the pyrotechnical eiciency Heat Recovery rom Fle as In many processes o hightemperatre technology the combstion gases leave the kiln with temperatres ar above 200 C. Thereore, Figre 311 presents the pyrotechnical eiciency or temperatres p to 1000 C. It is clear that the eiciencies drop to approximately 40%. Figre 312 presents in principle, heat recovery rom the heated gas redces the speciic energy consmption, in which the air or the combstion in a recperator is preheated. I the el low with and withot heat recovery is denoted with M & or M & 0 respectively, the ollowing can be deined as the eiciency o energy saving E 1 0 h h. (329) Using the el consmption according to eqation (322) the ollowing is obtained rom this ( 1+ λ ) cpg ( g e ) ( 1+ λ ) c ( ) h E 1 (330) h pg g e The level o the air preheating and thereore o the temperatre redction o the combstion gas depends on the qality o the recperator. For its speciication, the eiciency η R c c p p ( p e ) ( ) g e c c pg p ( g g ) ( ) g e (331) is deined which is the enthalpy emission o the combstion gas in the recperator in relation to the inlet enthalpy. Ths the ollowing reslts rom eqation (330) ( 1+ λ ) c ( ) h pg g e E 1 (332) λ c ( ) ( ) ( ) p h + λ 1 cpg g e 1 η R 1+ λ cpg and with the pyrotechnical eiciency in accordance with eqation (326) η E 1 (333) λ c ( ) ( ) p 1 1 η 1 η R 1+ λ cpg Figre 312 represents this eiciency o energy saving. It is obvios rom this that particlarly in low pyrotechnical eiciencies mch energy can be saved by heat recovery. In a

8 pyrotechnical eiciency o 0.5 or example and a recperator eiciency o likewise only 0.5 a relative energy saving o approximately 35% is prodced. The eiciency o energy saving is oset thogh by the investment costs. These are still relatively inexpensive p to air preheating temperatres o approximately 600 C, since they then can still be constrcted ot o steel. I the combstion gas permits a considerably greater preheating o the air, then as a rle regenerators made o ceramic materials are introdced here. It shold be noted that air preheating can be problematic with le gases which contain a high proportion o dst or liqid metal oxides (adherence on the walls) or trace gases which act corrosively O 2 Enrichment o Air As Figre 313 schematically depicts, a rther possibility or the redction o the speciic energy consmption exists in the oxygen enrichment o the combstion air. The air rom the environment is mixed with pre oxygen so that the combstion air possesses an O 2 concentration x~ O 2 > 0. 21or x O2 > In accordance with eqation (22) and (26) respectively, the air demand and conseqently also the le gas low sink in this way, as a reslt o which the le gas losses are redced. From eqation (320) the ollowing is obtained or the el demand sing eqation (26) Q M & & h λ O. (334) 1 1+ cpg ( g e )/h x O2 I the relative eiciency o energy saving is deined in trn as E 1 0 h h (335) M & 0 h being the el demand related to the O 2 concentration o the ambient air x O2 e, then the ollowing enses rom the two eqations above λ O h 1+ cpg ( g e ) x O2e E 1 (336) λ O h 1+ cpg ( g e ) x O2 Figre 314 shows this relative eiciency o energy saving as a nction o the O 2 enrichment o the air sing the example o el natral gas. It is obvios that the eiciency o energy saving is all the greater, the higher the le gas temperatre is and the greater the excess air nmber deviates rom one. It is especially apparent rom the representation that slight oxygen enrichments are already sicient to achieve a relatively high el saving and that a rther enrichment only slightly increases the el saving. The el costs saved are oset by the oxygen costs. The crrent costs are ths compared with one another or the economic assessment o the O 2 enrichment. In the operation withot O 2 enrichment the costs reslt in

9 C 0 M 0 c & (337) M & 0 being the necessary el low and c the price o the el. In the case o operation with O 2 enrichment the costs C M & c + c (338) O 2 O 2 are incrred, M & O being the O 2 2 mass low introdced and c O the price o the oxygen. The 2 investment costs or the installation o the O 2 enrichment are comparatively low and can be allowed or the additional oxygen price. The level o the O 2 low depends on the O 2 enrichment in accordance with O2 λ O x O2 x x 1 x O2 O2e O2e. (339) I a cost saving is deined analogosly to the el saving E C C 1 (340) C 0 then, sing the eqations (331) to (334) and the el demand in accordance with eqation (3 30), the ollowing enses E C λ O x O x O e c 2 2 O2 E (1 E). (341) x 1 x c O2 O2e This eqation shows that the cost saving does not depend on the individal prices bt on the price ratio. Owing to > 0 the cost saving is always smaller than the energy saving. Only in c O 2 the ideal case 0 are both eqally large. Figre 315 depicts the relative cost saving as a c O 2 nction o the price ratio with the le gas temperatre as parameter and to be precise sing 1. The cost saving decreases the example o natral gas with maximm O 2 enrichment ( ) x O 2 linearly with rising price ratio. Below the line E C 0 the O 2 enrichment leads to an increase o the costs. At present the price ratio o oxygen to el is approximately in the range 0.2. According to that a cost saving is obtained only in processes with le gas temperatres approximately above 700 C. From the eqations (336) and (331) with E C 0, the maximm price ratio, p to which an O 2 enrichment is still economical, amonts to c c O2 max c pg 1 1 x O2e. (342) h λ O 1 x g O2e

10 This price ratio depends thereore only on the le gas temperatre, the el and the excess air nmber; on the other hand it does not depend on the level o the O 2 enrichment. Figre 316 shows this maximm price ratio as a nction o the le gas temperatre with an excess air nmber o 1.3. As a rle an O 2 enrichment is not worthwhile at crrent prices. A heat recovery rom the le gas will be more economical. An O 2 enrichment can however be economical or other reasons, or example i by this means a prodction increase can be achieved in an existing plant or i additional costs in the le gas cleaning can be saved in the case o very dirty le gases sch as rom waste incineration. 3.4 Domestic Firings Domestic irings are characterized by very low process temperatres, which are speciied by the retrn temperatre o the heating water recirclation loop. The pyrotechnical eiciency can be increased and the gross heating vale can be sed to redce the energy consmption o private hoseholds Pyrotechnical Eiciency In ermany once again a higher vale or the pyrotechnical eiciency o heating systems is stiplated starting in the year 1998 or energy saving in private hoseholds. According to the size o the system the eiciencies mst be above 89 to 91%. As a rle in systems the air is scked in throgh the injector eect o the escaping el. In this way excess air nmbers in the magnitde o three reslt so that in accordance with Figre 39 the reqired eiciency cannot be maintained. Modern systems thereore have a controlled air inlet in order to set the lowest possible excess air nmbers, as a rle arond 1.2. With an additional slightly redced exhast temperatre modern (conventional) heating systems achieve a pyrotechnical eiciency o approximately 95%. The condensate problems which might occr here are gone throght the chimneys ross Heating Vale Use In view o the low temperatre level o the process heat, gross heating vale se can save el energy in heating engineering. Here a portion o the condensation enthalpy o the water vapor in the le gas is sed. The hmidity o the le gas was already explained with Figre 29. Figre 210 represents the dew point temperatre o the le gas. According to that in the case o natral gas the le gas mst be cooled nder 60 C and in the case o el oil even nder 50 C beore the steam condenses. Since natral gas moreover still possesses the higher proportion o water vapor the gross heating vale se is worthwhile as a rle only with this el. The more the le gas is cooled, the more condenses as a reslt. For the assessment o the gross heating vale se the condensation rate η con H2O ( ) x H 2O g 1 (343) x ( ) dew

11 is introdced, ( ) x being the le gas hmidity in accordance with Figre 29 at the H 2 O dew dew point temperatre. Using eqation (214) the ollowing reslts rom this η con H 2O ( ) ( ) dew H2O ( ) p H O g p p 2 H 2O dew 1 (344) p p p ( ) g sing the eqilibrim steam pressre o the water vapor p eq according to eqation (253). Figre 317 presents the rate o condensation or natral gas as a nction o the le gas temperatre with varios excess air nmbers. The lower the excess air nmber is, the more condenses. The energy saving amonts to E η H h 0 con (346) h H 0 being the gross heating vale. In comparison with the other ossil els the dierence rom the heating vale is the greatest in the case o natral gas and in accordance with Table 31 amonts to 10.5%. At a maximm heating temperatre o 40 C with a retrn temperatre o the heating water o 30 C, a cooling o the le gas is possible p to approximately 40 C. According to Figre 317 the gross heating vale se then amonts to 60%. In accordance with Figre 39, the pyrotechnical eiciency amonts to 99% at this le gas temperatre. The total pyrotechnical eiciency in the gross heating vale s can conseqently reach vales o 105% (in relation to the heating vale). Compared with modern heating systems with pyrotechnical eiciencies o p to 94%, an energy saving o 11% is conseqently possible. This saving consists thereore o p to 6% rom the gross heating vale se and o p to 5% redction o the le gas losses. The el costs saved are in trn oset by higher investment costs, since the gross heating vale boilers are technically more complex and larger heating sraces are necessary in view o the lower heating temperatres. The technology o heating engineering will be dealt with in the relevant chapter. In hoses erected ntil now the heating system is designed or higher low and retrn temperatres o the water recirclation loop than 40 or 30 C respectively. In older systems the low and retrn temperatres amont to 70 to 50 C. When these heating system is replaced with gross heating vale heating the condensation heat is conseqently lower than 6% speciied above, which makes the economic easibility worse. By comparison the heating system in new bildings is designed or the low water temperatres withot considerable additional costs, an nderloor heating being very sitable. In gross heating vale heating an installation on the roo presents itsel, as a reslt o which the costs or the chimney are saved. 3.5 Brning o metals Not only ossil els bt also a mltiplicity o rther materials can be oxidized and therewith brned. However most o these materials occr not natrally and are relatively expensive. Thereore their oxidation remains limited to special cases. In this section as example the brning o some metals is treated. In the orm o dst these can react and brn very well.

12 In ig. 321 the mass lows are represented or an adiabatic reaction. As combstion prodcts reslt a metallic oxide, which is present liqid de to the very high combstion temperatre, and a gas, which consists o nitrogen and or excess air o srpls oxygen. To the mass lows applies and ( 1+ x ) M & M & (352) Ox Met O2 ( 1) O & λ & λ, (353) MMet x N2 + MMet x 2 whereby x N 2 and x O 2 are the mass concentrations o nitrogen and oxygen in air. The oxygen and air reqirement can be compted with the Eg. (23) and (25) given in section 22. In the table 36 these two vales or the brning o the or metals chrome, alminm, magnesim and iron are speciied. By comparison with the tables 23 and 25 it is evident that metals have a very small air reqirement. Metal Oxide O h kgo 2 kg Met kg kg air Met MJ kg Met M ~ Met kg kmol melt h melt C c ( λ 1) kj kg Oxide kg kj Oxide K ad C Cr Cr 2 O Al Al 2 O Mg MgO Fe Fe 3 O Table 36: Brning o metals As energy balance is valid Met Ox ( cox ad + h melt ) + cp ad h + c. (354) With the metal reaction enthalpy h is spplied. The enthalpy spplied with air is negligible. With the metallic oxide also melting enthalpy is exhasted. The speciic thermal capacity c Ox o the metallic oxides is represented in ig The mean speciic thermal capacity o the gas is compted with Eq. (310). With the Eqs. (352) and (353) ollow or the adiabatic brning temperatre ad h ( 1+ xo ) h 2 melt ( 1+ xo ) cox + ( λ xo ) c. (355) 2 2 This temperatre is speciied or a stoichiometric reaction in table 36 with the associated enthalpy. One recognizes that the brning temperatre is not only mch more higher than the melting temperatre bt also very mch higher than the combstion temperatre o the ossil els. The brning temperatre is so high despite the low reaction enthalpy relatively low

13 opposite that o the ossil els, since the oxygene reqirement is so small. De to their high temperatre the metallic oxides shine very brightly. Thereore these are sed or ireworks.

14 0 C Fel Reaction Chamber H O Dry combstion gas 0 C 0 C Air Complete Combstion with λ > 1 iqid water 0 C Fig. 31: Determination o Heating Vale Stochiometric Air Demand CO Blast rnace gas Methanol andill gas Biogas Wood Textilies Papers Alcohol Plverised lignite m & eather Natral gas H Fel oil S asoline Natral gas Coke oven gas Carbon Fel oil E Anthracite Benzene Plastics Coal Coke Car tyres Propane 0,33 [kg /MJ] h 0 Fig. 32: Heating vale h in MJ/kg Correlation between heating vale and air demand

15 Air Fel M & M &, F Adiabatic Firing Chamber Combstion gas M & Adiabatic temperatre ad Fel M & Air M &, F Nonadiabatic Firing Chamber Q & e Combstion gas M & Temperatre Frnace/Heating Q & Fle gas M & Fle gas temperatre g Fel M & Air M &, F Frnace/Heating Q & Q & e Fle gas M & Temperatre g Solid Fel M & Frnace/heating Q & e Smoke gas Priication Fle gas Air M &, Fig. 33: Temperatre o Combstion as

16 1,30 Mean speciic heat capacity [kj/(kg K)] 1,25 1,20 1,15 1,10 1,05 1,00 λ 1.0 Natral gas type Fel oil (light) Anthracite Antracite Blast rnace gas λ 1.2 0, as temperatre [ C] Fig. 34: Mean speciic heat capacity Molar Concentration 1,E+00 1,E01 1,E02 H 2 O CO H O CO 2 N 2 OH H 2 O 2 1,E03 Natral gas type Air: 0.21% O2 Air preheating: 800 C 1,E04 0,7 0,8 0,9 1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2 Excess air nmber Adiabatic gas temperatr [ C] Fig. 35: Temperatre and concentration at combstion o natral gas type

17 Adiabatic gas temperatre [ C] CO 2, H 2 O, H 2, CO, N 2 as components concidered: CO 2, H 2 O, O 2, N 2 CO 2, H 2 O, O 2, N 2, CO, H Natral gas type 1900 Air: 0,21 Vol% O 2 Air preheating: 800 C ,6 0,7 0,8 0,9 1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2 Excess air nmber λ CO 2, H 2 O, O 2, N 2, CO, H 2, O, H, OH Fig. 36: Compairison o adiabat gas temperatre with and withot dissociation as temperatre [ C] Blast rnace gas CO H 2 as lame coal Fel oil light Natral gas type Anthracite Antracite coal coal Brown coal 1 1,2 1,4 1,6 1,8 2 Excess air nmber Fig. 37: Adiabatic lame temperatre with dissociation

18 2300 Temperatre [ C] air 800 C 600 C 400 C 200 C C ,7 0,8 0,9 1 1,1 1,2 1,3 1,4 Excess air nmber Fig. 38: Inlence o air preheating on gas temperatre Adiabatic combstion o natral gas type, λ 1.1 0,3 0,25 Temperatre [ C] H 2 O CO 2 0,2 0,15 0,1 Concentration ,05 O 2 CO H ,21 0,26 0,31 0,36 0,41 Concentration o O 2 in air Fig. 39: Inlence o O 2 enrichment

19 1 0,99 0,98 Natral gas type Fel oil (light) 0,97 Firing eiciency 0,96 0,95 0,94 0,93 λ 1 λ 1,2 0,92 λ 1,5 0,91 λ 2 0, Temperatre dierence between le gas and combstion air [K] Fig. 310: Firing eiciency 1 0,9 0,8 Firing eiciency 0,7 0,6 0,5 0,4 Natral gas type λ 1 λ 1,2 λ 1,5 0,3 λ 2 0, Temperatre dierence between le gas and combstion air [K] Fig. 311: Firing eiciency or natral gas type

20 . Q e Ambient Air e Fel Q. Firing Fle as Fle gas g., M Preheated Air p., M Fig. 312: Firing plant with heat recovery rom le gas Relelative energy saving 1 0,8 0,6 0,4 0, ,2 0,4 0,6 0,8 1 η 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 Eiciency o recperator η R Fig. 313: Relative energy saving by air preheating

21 Ambient air Fel Frnace Q. le gas Fle gas Heat Heat. AO exchanger A exchanger M g, A. Preheated air V, M. Preheated el, M BV B AO V Fle gas Air A BV Fle gas Fel Flow length A Fig. 314: Firing plant with heat recovery by air and el preheating 1 Rel. energy saving E 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Air demand η R 0,8 η RB 0,8 η R 0,8 η RB 0 λ 1,1 η 0,4 0,6 0,8 Fig. 315: Relative energy saving by air and el preheating

22 Fel Ambient Air x Oxygen O2e Combstion Air x O 2 Q. Fle as Fig. 316: Oxygene enrichment o combstion air Relative el saving 1,0 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 Natral gas type λ 1.1 λ 1.3 Fle gas temperatre 800 C 600 C 400 C 0,0 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 Fig. 317: Inlence o oxygene enrichment 1600 C 1400 C 1200 C 1000 C Oxygen content in enriched air [m 3 O2/m 3 air]

23 1 Fle gas temperatre 1600 C Relative cost savings 0,75 0,5 0, C 1200 C 1000 C 800 C 600 C Natral gas type λ C 0,25 0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 Price relation oxygen / el Fig. 318: Relative cost savings 0,8 0,7 Excess air nmber λ 1.3 Anthracite Antracite imit price relation 0,6 0,5 0,4 0,3 0,2 0,1 Natral gas type Fel oil light 0, Fle gas temperatre [ C] Fig. 319: imit price relation

24 1 0,9 Condensation degree η con 0,8 0,7 0,6 0,5 0,4 0,3 0,2 Fel oil light λ Natral gas type , Fle gas temperatre [ C] Fig. 320: Condensation degree 1,00 0,98 0,96 0,94 Eiciency 0,92 0,90 0,88 0,86 0,84 0,82 Natral gas type Fel oil light λ 1,0 1,2 1,5 1,0 1,2 1,5 0, as temperatre [ C] Fig. 321: Eiciency o combstion plants with gross heating vale as reerence

25 M Met, h M Oxid, Schm, h ad M, M g, ad Fig. 322: Mass low in metal combstion 2,0 Speziic heat capacity [kj/kg K] 1,8 1,6 1,4 1,2 1,0 0,8 Fe 3 O 4 MgO Al 2 O 3 Cr 2 O 3 0, Temperatre [K] Fig. 323: Speziic heat capacity o metal oxids

26 Fel ρ Net heating vale Upper heating vale Hydrogen Carbon monoxide Methane Propane Natral gas Natral gas H Cokeoven gas Top gas Biogas ight oil Heavy oil Diesel oil Petrol Methanol Ethanol raphite Coal Coke Raw lignite ignite dst Wood (dry) kg/m 3 in MJ/m 3 MJ/kg MJ/m 3 MJ/kg ,6 28, Table 31: Reerence vales or heating vales o els Fel Natral as ight Oil Heavy Oil Coal Coke ignite Electricity withot distribtion Electricity with distribtion Treatment Demand Energy In MJ/kg In % rom heating vale kwh el /kwh prim kwh el /kwh prim Table 33: Treatment Demand Energy or Fossil Fel according to Fe [1.2] and Mach [1.1]

27 NO 2 O 2 CO 2 H 2 O CO H 2 as c p KJ/(kgK) n ρ i M ~ kg/m kg/kmol Table 34: Speciic heat capacity and density at 273 K and 1 bar Heating power ntil 1983 p 1983 p 1988 p 1998 in kw > Table 35: imit vales in % or loss o le gas or oil and gas heating according to installation year kj kcal kwh kg SKE kg RÖE m 3 Natral as 1 Kilojole (kj) 0,2388 0, , , , Kilocalorie (kcal) 4,1868 0, , ,0001 0, Kilowatt hor (kwh) ,123 0,086 0,113 1 kg coal eqivalent ,14 0,7 0,923 (SKE) 1 kg Crde oil eqivalent ,63 1,428 1,319 (RÖE) 1 m 3 Natral as ,816 1,083 0,758 Table 32: Conversions or energy nits

28 Metal Oxid O h M ~ Met Melt Melt h c ad ( λ 1) kg kg O2 Met kg kg Air Met MJ kg Met kg kmol C kj kg Oxid kg kj Oxid K C Cr Cr 2 O Al Al 2 O Mg MgO Fe Fe 3 O Table 36: For calclation o metal combstion