Cement Energy and Environment

Potential savings and benefits are as follows: • US$ 64 000/yr is saved in fuel costs based on Table 2. Results of decreasing kiln firing hood leakage from 10% of total air entering kiln to 2% on preheater kiln system with grate cooler Before After Effect change change Kiln hood leakage,% 10 2 - 8% of total kiJ n inlet air Fuel consumption, net 775 750 - 3.2% kcallkg Production capacity, tpd 975 1000 +2.5% Annual production 330 322 ()()() 330 {)()() +8000 days/yr, tpa Fuel cost, US$/t 6.20 6.00 - US$ 0.20 · production of 322 000 tpa. • US$ 160 000/yr in additional savings or income can be reali sed from additional producti on achieved. • ln the case of planetarycoolers, reducing kiln firing hood leakage will increase air flow through the planetary coo ler whi ch redu ces the c li nker discharge temperature as it leaves the cooler and improves fuel efficiency. The effects of decreasing kiln feed end hood leakage on clinker production, specific fuel consumption and preheatcr inlet gas temperature for a preheater kiln with a grate cooler are shown in Fig. 3. In this exampl e, preheater exit gas fl ow was maintained at a constant level and the fuel firing rate, clinker production and preheater inlet gas temperature were allowed to vary. 4 ~ 2 "' 0 v "' -2 "' v .... u v -4 "0 ~ -6 ;a "' -8 <) cr. "' v t> - I0 ..s - 12 10 ln a kiln system limited by the lD fan capacity, kiln capacity will increase signifi cantly and specific fuel consumption will decrease as shown in the above example. The potential savings achjeved by decreasing kiln feed end preheater leakage from I0 per cent of the total air entering the kiln to 2 per cent are shown in Table 3. Potential savings and benefits are as follows: • US$ 36 000/yr is saved in fuel costs based on production of 300 000 tpa. Table 3. Potential savings of decreasing kiln feed end preheater leakage from 10% of total air entering kiln to 2% Before After Effect change change Prcheater leakage. % 10 2 -8% of total preheater inlet Fuel consumption. net 765 750 -2.0% kcallkg Production capacity. 91 0 1000 +9.9% tpd Annual produc.:Lion 330 300 000 330 000 +30000 days/yr, tpa Fuel cost. US$/t 6. 12 6.00 - US$ 0.12 • US$ 600 000/yr in potenti al savings or income can be realised from the additional production acrneved. Heat transfer cfficienC) Numerous indicators of heat transfer efficiency exjst, such as kiln systemexit gas temperature. Acompari'son 60 50 G :. 40 til'-' "' <) 0/J v: - "' ~ ~ 30 t: u ·- .5 ~ ~ Specific ::5 - 20 C) :::l consumption ..t: ;; ll) ,_ _ Preheaterinlet .... ll) 10 p... 0. gas temperature E - Clinker production ~ 0 8 6 4 2 In a preheater kiln , reducing air infil tration at the kiln feed end reduces the amoun t that the kiln exit gases are coo led. Hi gher gas temperatures entering the preheater improves heat transfer efficiency between gases and material flowing in the preheater. In addition, lower air infiltration decreases the volume of air travelling through the preheater that results in lower velocity and. therefore, increases the retention time of the gases travelling through the preheatcr. An increase in retention time improves heat transfer in the preheater. Thi s also applies to a ca lcincr kiln system. Fig.3 1!.1fects of decreasing kiln feed end lzood leakage 11