Kiln capital cost

Cement kilns - Capital costs for handling and feeding - Low cost of alternate fuels (particularly in areas where petroleum coke is available) - Expense and downtime in environmental... 

Including the cement kiln case just reviewed, the thirteen cases presented in (43) show the capital cost of various "energy" conservation projects in comparison with the capital required to provide an equivalent new supply. 

Except for the rotary kiln itself, which now represents only a fraction of the total capital cost, today s modern coke calcining plants bear little resemblance to the original facilities (Figure 2). Even the kiln itself has undergone major changes, not the least of which is increased capacity. A typical modern kiln,... 

Rotary kiln processes are continuous processes that use a rotary kiln reactor to depoly-merize plastic [4, 5]. They have a lower capital cost compared with fluidized-bed processes and their liquid product resembles crude oil. The following are some general characteristics of kiln processes ... 

Option 2. Calcining to Nonacidk State. Capital costs for kilns, absorption towers, and baghouses were estimated at 3 H 200 000, 13 600 000, and 14 400 000 for plants A(H), B(H), and C(H), respectively, with the remainder of the cost being that of the lime and limestone required for neutralization of the SO2 and maintaining an alkaline environment in the kilns. No operating costs are included. Costs for Plants A(A), B(A), and (i(A) were determined by ratioing. 

Controlled-air incinerators have a lower capital cost since they do not normally require air pollution control equipment (unless acid gas emissions are excessive). But since this facility must comply with new stringent regulations and acid gas emissions may be excessive, a rotary kiln system may be more advantageous. 

Two small commercial incineration facility designs are under consideration. The first design involves a liquid injection incinerator and the second a rotary kiln incinerator. For the liquid injection system, the total capital cost (TCC) is 2.5 million, the annual operating costs (AOC) are 1.2 million, and the annual revenue generated from the facility R) is 3.6 million. For the rotary kiln system, TOC, AOC, and R are 3.5, 1.4, and 5.3 million, respectively. Using straight-line depreciation and the discounted cash flow method, which design is more attractive Assume a 10-yr facility lifetime and a 2-yr construction period. Note that the solution involves the calculation of the rate of return for each of the two proposals. 

Rotary kilns were developed for the manufacture of cement, and were first used for lime burning in 1885. Their high capital cost, however, limited their use to relatively large productive capacities. They could only calcine small limestone (e.g. with a top size of 60 mm), but, while this was an advantage in terms of the stone balance of the quarry, the small lime produced was not as marketable as lump lime. For many years, rotary kilns were largely used to feed hydrating plants. 

Thereafter, the standard project considerations apply (e.g., capital/operating costs and the logistics of number/size of kilns in relation to current and forecast market demand). The extent to which a new kiln might fit into the existing infrastructure, and particularly to existing lime and limestone handling and storage equipment, can also have a marked effect on the capital cost and ease of installation. 

A conservative capital cost estimate was made for a 610-mm diameter SBD designed to dry 220 kg/h of wet sludge with 20% by weight solids. The cost compared favorably with available kiln-type technologies and shows that the spouted bed is cost competitive with conventional technology. 

Rosen has given pilot-scale data on pressure steam drying of lumber for 27-mm-thick, green, yellow poplar, and red oak [10]. He also made a technoeconomic study based on a number of plausible assumptions. Essentially, he showed that the capital cost of the steam dryer was about the same as that of a conventional kiln, although the drying times were reduced. 

Shuttle car-hearth furnaces and kilns are hybrids between batch and continuous furnaces and kilns, combining the compact lower cost of a batch operation with the productivity and fuel economy of a continuous furnace or kiln. A shuttle furnace has doors at both ends and with two rolling hearths, permitting quick unloading and reloading of the furnace with minimum cooling during the switch-around. (See fig. 4.8.) The capital cost is only about 65% of two furnaces, but the production rate is almost doubled. The fuel economy per year and per ton heated is better because the doors are closed and the burners are in use more often. 

The capital cost of equipping a cement kiln to burn waste solvent covers... 

Microscopy with point-counting can be used and, although it can be time-consuming, it is quite attractive in terms of its low capital cost. It also produces information on kiln performance not available from other methods. 

Measurement. The need for cost-effective pollution prevention, efficiency improvements, and emissions meastmement has created a need for new types of integrated control and meastirement systems. One of the best methods to improve environmental performance initially is to maximize efficiency through optimization in their manufacturing and energy processes. Many cement kilns now use continuous NOx measurement at the kiln exit to feed back information to the process control to optimize combustion. Capital costs are usually small, especially if PEM/ optimization software systems can be included at the time of a control system u rade. The increased operator awareness of the plant is a benefit, and fuel savings, qualify control, and maintenance planning can quickly pay back initial costs. 

This whole picture suggests that chemical recycling is financially still a rather uncertain business, a view that is indeed reinforced by cost calculations. The basic point probably is that purpose-built recovery installations will always have trouble in competing with technologies built for another purpose, but which happen to be able to recycle or recover MPW - which is the case with blast furnaces and cement kilns. The latter have the advantage that capital investment does not need to be allocated to the MPW. 

Two major types of lime caleiners are die rotary (Fig. I) and (he vertical kiln, In North America, rotary kilns are widely used for lime cnlcinuiion. whereas in Europe vertical kilns are most popular. Rotary kilns typically have higher output [up to 6 tons (545 metric tons)/da> and lower labor cost. Vertical kilns can be designed for higher fuel efficiency and lower capital investment. They handle down to about -in. (19-cnt) stone, hut... 

Burning tires in existing pulp and paper mills and certain types of cement kilns requires much less capital investment than the dedicated power plants mentioned above. Pulp and paper mills often bum hog-fuel (chipped wood), thus requiring very little modification for tire chips. The main economic variable is the price of the competing fuel. Tire-derived fuel must often compete with low cost coal or petroleum coke, a waste product from the petroleum refining process. If tdf is only slightly cheaper than the alternate fuel, then plant modification cannot be justified. 

The high capital investment cost of the Asahi process is due to the necessity for large absorbers, evaporators, crystallizers, dryers, rotary kiln crackers and screw decanter separators. The major operating and maintenance costs are electricity, fuel oil, steam and chemicals such as soda ash, EDTA and limestone. The requirement for consumption of large amounts of utilities is associated with the operation principle and design of the Asahi process. According to the economic evaluation, equipment required for N0X and SO2 absorption (such as packed-bed absorbers) accounts for 20% of total direct capital investment for treatment of dithionate ion (such as evaporator, crystallizer, dryer, and cracker) it accounts for about 40% and for treatment of nitrogen-sulfur compounds (such as screw decanter and cracker) it accounts for only 2%. 

For the processes of different reactor types, kiln and retort pyrolysis processes are characterized by a relatively low capital investment. However, they suffer from unfavorable economics, due to the high processing costs compared with the value of the oil product obtained. Also, the characteristics of this process are relatively long residence times of waste in the reactor, poor temperature control due to large temperature gradients across their internal dimensions, fouling walls of the reactor by carbon residue and low liquid product quahty due to the production of a diverse number of pyrolysis products. 

A more robust method involves preheating the air 10-20°C above ambient. This increases the low adsorptive capacity of the air and ensures that drying continues throughout winter. Less basic versions recycle the heated air within an enclosed space and in effect function as a uninsulated, low-temperature kiln. Such an operation has attractions where damp winters make air-drying very slow. They are cheap, and capital is often limited for small companies. Low-temperature, low-cost driers provide some control over the drying elements that is lacking in air-drying. 

The choice of lime kiln is of paramount importance to a lime producer. It must be suitable for burning the selected feedstone and for producing the required quality of quicklime. It must have sufficiently low capital and operating costs to produce quicklime at a competitive price. Its capacity must also be appropriate for the market requirements. 

D. Sauers, N. Biege, D. Smith, Comparing lime kilns . Rock Products, 1993, 1. Introduction March, 2 Feed size April, 3 Quarry utilisation May, 4 Product Quality and fuel types June, 5 Capital and operating costs July. 

The production cost is also affected by charges for capital (interest and depreciation), labour and refractories. In industrialised countries, large kilns have been installed to reduce those costs per tonne of quicklime. Increasingly, shaft and rotary kilns are being installed with capacities of up to 600 and 1000 t/d respectively. In less industrialised countries, however, where labour costs and the availability of capital are lower, continuously operated shaft kilns with capacities of 1 to 100 t/d are common. Batch Idlns are also widely used, where still lower production rates and/or increased flexibility is required. 

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