limestone process auxiliaries

how to process limestone? - hongxing machinery

how to process limestone? - hongxing machinery

Limestone is a common non-metallic mineral, which is also a trading name as a raw material mineral. Limestone is widely used because of its wide distribution and easy access in nature. As an important building material, the limestonehas a long history of mining. In the modern industry, limestone is themain raw material for the manufacture of cement, lime and calcium carbide. In addition, the limestone is alsoan indispensable flux limestone in the metallurgical industry.

Limestone can be also used to manufactureglass, soda ash, caustic soda, etc., and the quicklimecan be used to manufacture slag material, removing harmful impurities such as sulfur and phosphorus. In the agricultural industry,the application of slaked lime in the soil can neutralize the acidity of the soil, improve the structure of the soil, and supply the calcium required for the plant.

Generally, the chemical industry uses limestone to make important calcium salts such as calcium chloride, calcium nitrate, and calcium sulfite. In China,Xinjiang provinceis rich in limestone reserves. In view of the huge economic value of limestone mining, the limestone powder processing industry has been vigorously developed in recent years and has achieved good economic benefits.

With the continuous advancement of science andnanotechnology, the application field of limestone is being further broadened. Limestone is not only an indispensable raw material for the cement and steel industrybut also widely used in water ash, smelting, cement, chemical, power plant desulfurization, and paper industries.

In addition, the limestonecan be used as a substitute for plastics to make packaging materials, which brings environmentally-friendly benefits. The limestone market demand is increasing year by year, and it is one of the most dynamic environmental protection and green mineral resources in the 21st century. In recent years, the limestone powder processing industry has gradually become hot, and its application has achieved considerable economic benefits.

From the current demand for limestone at home and abroad, the annual demandfor limestonein the world is about 1.2 billion tons, but 80% is for general use. High-quality limestonehas a small market and a low market due to its low resources. In recent years, countries in the Asia-Pacific region have imported about 1.1 million tons of limestone from China each year because of insufficient domestic limestone resources.

From the perspective of the domestic market, the rapid development of the western region, urbanization, and new rural construction all have played a direct role in promoting the development of the metallurgical building materials industry, which will certainly stimulate the development of the metallurgical building materials industry. At the same time, limestone demand will increase.

From theperspective of the international market, Chinas limestone mineral resources are rich, accounting for more than 64% of the worlds total reserves. Due to the limited limestone minerals in most western countries, cement production and limestone mineral resources have been restricted. Therefore, its dependence on Chinese limestone has gradually increased, and the export market continues to be optimistic.

Judging from the resource situation, the large limestone mines have been basically monopolized by large cement companies and metallurgical enterprises, and new resources are becoming less and less. In a sense, someone who owns limestone resourceswill occupy the future cement and steel market.

The physical properties of limestone are small hardness and high brittleness. The limestone has low silicon content and low abrasiveness. Limestone crushingis relatively easy and the production cost is relatively low. According to differentapplications, the limestone needs to be crushedinto particles of different sizes, which requires a limestone crushermachine. As long as the appropriate process configuration and crushing equipment selection are adopted in the crushing process, a good crushing effect can be obtained.

In combination with the principle of crushing more and less grinding in the limestone production line, it is necessary to produce the best particle size in the stage of limestonecrushing. There are several types of rock crusher machine can process limestones, such as fixed jaw crusher, impact rock crusher machine, hammer crusher machine, and hydraulic cone crusher machine.

The fixed jaw crusher machine is very convenient to operate and maintain, and it is very easy and quick to replace parts, saving a lot of replacement time. In addition, the fixed jaw crusher machine has low production cost and high output, which is very suitable for the primary crushing of limestone.

Even the hammer crusher machine continuously working for long hours, the frequency of crushing failure tends to be low, saving customers a maintenance cost and reducing maintenance time, which has increased the economic benefits for the company to a certain extent. Stable operation, high output, and strong adaptability are the biggest advantages of the hammer crusher machine.

Compared with the hammer crusher machine, the impact crusher machine has a larger crushing ratio and can fully utilize the high-speed impact energy of the entire rotor. In the process of actual production, the impact rock crusher is also the main rock crusher of the limestone crushing production line. The crushing characteristics of the impact rock crusher are remarkable: uniform discharge granularity, cubic discharge, low fine powder and dust.

Compared with other rock crushers for sale, the hydraulic cone crusher has the advantage of environmental protection. At the limestone crushing site, almost no dust can be seen, reducing pollution to the environment. In addition, the hydraulic cone crusher machine has the advantages of superior performance, affordable price, high output, and low failure rate.

Common limestone crushing line equipment includes fixed jaw crushers, impact crushers, belt conveyors and vibrating screens. This is in terms of overall device configuration. However, differenttypes of rock crushers will be configured according to customersactual needs. Thefixed jaw crusheris generally selected as primary crushing. If the second-stage crushing needs to be configured according tocustomersactual demands.

Through analysis and comparison, the four stone crusher machines have their own advantages in crushing limestone. In the end, which stone crusher should be selected depends on the customers actual needs. If the amount of limestone material processed tends to be relatively large, it is recommended to select an impact rock crusher. For the price of limestone crushers, the price of different types of rock crushers for sale is different.

For example, the fixed jaw crusher is divided into CJ series European version fixed jaw crusher, PEX series fixed jaw crusher, and the hydraulic cone crusher can be divided into single-cylinder hydraulic cone crusher, multi-cylinder hydraulic cone crusher, full hydraulic cone crusher, etc.

The price of rock crushers for sale with high-yield tends to be high. HXJQ technicians will design the most suitable rock crusher for sale according to each customers needs and budget. The corresponding stone crusher will be configured according to the production site and production demand. In addition, our technicians will personally install and debug the machine to provide a one-stop service for customers.

auxiliary plant - an overview | sciencedirect topics

auxiliary plant - an overview | sciencedirect topics

Various emission control options are driving added auxiliary power requirements for coal-fired power plants. Figure 15.4 illustrates the various options for emission controls and their typical location in a coal-fired power plant. To highlight the range of impact of these processes on auxiliary power requirements, EPRI studied a variety of flue gas desulfurization (FGD) technologies. Refer to the blue SO2, SO3 control elements in Figure 15.4. Tables 15.3 and 15.4 list the effects of applying several alternative FGD techniques on the connected load of a 500MW coal-fired power plant.

The addition of anti-pollution devices such as precipitators and sulfur dioxide (SO2) scrubbers restrict stack flow and require an increase in in-plant electric drive power. About 40 percent of the cost of building a new coal plant is spent on pollution controls, and they consume about 5 percent of power generated [7].

Whilst the greater part of the turbine hall layout is the result of co-operation between the mechanical plant engineers and the turbine manufacturer, the electrical layout engineer must take a very detailed interest at an early stage to ensure that provision is made for personnel and cable access to all electrical items, and suitable locations are agreed for electrical equipment cubicles away from hot and potentially wet locations.

Some equipment imposes its own special restrictions- for example, the hydraulic control fluid used to operate the main steam valves must not be allowed to come into contact with the PVC insulation which is used on most cables. Chemical reaction causes the PVC to decompose.

From the examples of station layout shown in this chapter it will be noted that the relative positions of many auxiliaries vary considerably from one station to another; the amount of equipment being dependent on the operating philosophy of the station. A base-load unit may possibly have one quick-start air pump and three maintaining air pumps, whilst a unit intended for flexible operation could have two quick-start and two maintaining air pumps.

Most pumped systems have duplicate 100% duty units with instrumentation to measure pressure and temperature and give an automatic changeover should the running pump fail. Also, separate cable routes are provided for each pump to meet the requirements for segregation see Section 14.6.1 of this chapter.

In addition to the auxiliary equipment, the turbine-generator will itself require extensive cable steelwork to cater for the many instrumentation and control devices along the length of the set. Most of these will be marshalled by the turbine manufacturer who will fit flexible metal harnesses, containing heat or oil resistant wiring as necessary, between the actual devices. The devices may be located in a hostile environment and then junction boxes positioned in less hostile locations.

All the latest generator excitation systems make use of an AC exciter with diode rectification and thyristor control. The diodes may be static and mounted in the automatic voltage regulator (AVR) and excitation cubicle, in which case the cubicle must be mounted close to the generator to allow for the solid busbars necessitated by the heavy excitation current (5170 A for a 660 MW unit). Final connections are made to the pilot and main exciters by sliprings and brushgear.

Alternatively the diodes may be mounted between the exciter and the generator and rotate with the shaft, control and switching taking place between the main and pilot exciters. The lighter current permits the use of cable connections and allows greater flexibility in positioning the equipment cubicle. With this arrangement however, diode monitoring and maintenance are more complicated.

For the process boiler, there are several auxiliary plants and auxiliaries that require steam at different conditions. In addition, there is normally a turbo generator to provide electric power as a captive power plant. High-pressure steam required for the steam turbine therefore must be reduced to the desired pressure set point. This is achieved by a PRV that opens by a controller [may be a single-loop controller or a part of the main distributed control system (DCS) depending on the size and complexity of the plant] to a desired pressure set point. The inlet and outlet of the PRV (Fig. 1.33) are controlled with two remotely operated motorized isolation valves (post indicating valves) for isolating the control valve during maintenance.

During this time, the system can be made operational by remotely throttling (inching) the BPV, which heats up the line before starting the PRV operation by crack opening it. After pressure reduction is accomplished at the PRV, the steam is then allowed to pass through the desuperheating station to lower the temperature of the steam to the required value. The attemperation water is sprayed at high velocity through nozzles and at adequate quantity on the desuperheater. The desired value or set point is compared with a PID controller to generate the output signal, which determines the position of the desuperheating control valve (DSCV) by attemperation water flow to the desuperheater. At the inlet and outlet of the control valve (DSCV), there are two isolating remotely operated motorized isolation valves (TIVs) used to isolate the control valve during maintenance. During this time the system can be made operational by remotely throttling the BPV. In Fig. 1.33, two PRDSs are illustrated. The number of such stations depends on the requirement of the plant's auxiliaries.

Prior to tests taking place, detailed test schedules are agreed between the manufacturer and CEGB staff. The latter usually witness the principal tests, whilst other tests can be carried out by the manufacturer, so long as the results are submitted to the CEGB for scrutiny.

As far as is practical, all items of auxiliary plant are fully tested in the respective manufacturer's works before assembling them with the diesel generator. Such tests include hydraulic pressure tests on oil coolers, valves and piping, water coolers and tanks, air compressors and their auxiliaries. All rotating plant, such as air compressors, and all types of pumps are subjected to running tests over the full specified range of duty. Tests on motors prior to assembly with their driven items are covered in Chapter 7.

After checking such details as cylinder head nut torques, tappet clearances, pump drive chain tensions, crankshaft deflections, correct charging with oil and correct functioning, charging and priming of all auxiliary systems; each diesel engine, fully assembled with its generator, exciter, governor, AVR and auxiliary equipment, is then subjected to the following combined tests:

Run at normal speed and highest overspeed permitted by the manufacturer for five minutes to check the balance of rotating parts and compliance with vibration requirements. A typical figure for highest permissible overspeed for 5 minutes is 7%.

Run at full rated output by use of artificial electrical loading facilities for a sufficient length of time to ensure that steady working conditions have been reached, followed by a one hour run at 10% overload. Records of temperature attained on the unit are taken.

No-load operation endurance test, to demonstrate the ability of the unit to accept load and run satisfactorily after a continuous period of 48 h at synchronous speed, normal voltage and zero load. During this run, checks of fuel consumption, vibration, exhaust discoloration, etc., are made at regular intervals.

OLCS functions should include sequential controls (ATRS), interlock and protection for various plant auxiliaries, valves, dampers, etc. For OLCSs a few features needing a designers attention includes but are not limited to the following:

OLCS hierarchy: As discussed above, the OLCS system can be conceived to be arranged in a hierarchical structure including a unit level, group level (such as the boiler, turbine, feed water system, etc.), and subgroup level (such as the evacuation subgroup anddrive level). Hierarchical structure may be helpful for sequential control implementation. However, some drive controls are implemented in I/O cards. It is purely a design philosophy of the manufacturer.

Unit level start-up and shut down: It is possible today to start-up/shut down a complete plant with a single key stroke. Such start-up or shut down is done at theunit level. While designing a control system of this kind, safety is given the highest priority at every stage so that the sequence may proceed properly.

Group level control: Such controls are quite common in systems like BMS, ATRS, ATT, etc., as discussed in Clauses 2.2 and 2.3. At this group level independent automatic startup and shutdown are possible. When at the unit level, all groups are started one by one from single start/stop command. For group starting or shut down, each group needs a separate command. All subgroups, subloops, and drive interfaces (as applicable) under each of these groups is started one by one under a single group command. It is interesting to note that these group commands can be either fully automatic and semi-automatic.

Check back: CLCS is a feedback control system. Sequential controls of an OLCS may have a check back(see Clause 4.1.7) that signals for the sequence to proceed. It is like the feedback in CLCS. After a command signal is issued, before proceeding, the system ensures that the previous command has been obeyed by all concerned within the allowed time gap. This is to ensure that there is no hindrance to the sequence. This is done by check back signals. If there is any constraint for the execution of the previous command, then the fault/constraint must be detected and removed (may be bypassed for noncritical check backs, even manually and/or by manual override). For example, to start a large fan it is necessary that its lubrication pump(s) runs to establish a flow of oil in the bearing. If a command is issued to start the pump, but the pump does not start or cannot send oil, then bearings will starve. Therefore check back signals (that the lube pump is running and oil pressure is okay) are essential for the sequence to proceed further. Now if there is no such check back for a large fan, then one can only imagine what would happen.

Operation release and logic criteria: Before issuing any command, safety and readiness of the concerned equipment and systems need to be checked. When a command is issued (even manually) it is the duty of the system to check whether all the conditions for the safety and readiness of the concerned equipment and systems are available before it can make the command effective. These criteria checked by the system at the start of the sequence for any subgroup/subloop/drive are normally referred to as operation release. For example, after a boiler shut down any fuel can be started only after purging is complete in the recent (allowed time gap) past. Ifthe fuel is not started within a specified time after purge, another fresh purge cycle may have to be repeated before starting the first burner. Similarly at each stage, or for each interlock, such checks are done with the help of a check back and other status signals referred to as logic criteria, which need to be satisfied (or bypassed) to proceed to the next logical step. Safety interlocks for a human/machine are executed atany stage and are given the highest priority (see FigureVII/4.1.2-1)

Operational modes: Normally three modes of operations are seen in this type of OLCS. These modes areautomatic, semi-automatic (step by step), and manual (operator guidance). These are also discussed in no 5 of Clause 2.3.2.

Monitoring and display: To facilitate operation, it is customary to have these steps: operational release, step criteria, and check back status displays made available to the operator. There are provisions for alarms for abnormal situations. All modes, loss of timing, etc., are made available to the operator. Also it is important that access to these logic programs is restricted to the authorized persons. Certain step/criteria bypasses are allowed, but this is by operator only when faster action of operation is called for but never at the cost of (human and equipment) overall safety, and only authorized persons are allowed to take such actions. In addition to these, there are other sensor monitorings done including noncoincidence error, open/short circuit monitoring, etc.

Coverage: OLCS is not only applicable to main power plant sequence, interlock, and protection, it also includes all off sites as well. However, in these off sites a PLC may be used to integrate with the main DCS, but the criteria discussed for the OLCS could be used, depending on applicability. It is also applicable for the electrical control system.

OLCS functions shall include sequential controls (ATRS), Interlock, and protection for various plant auxiliaries, valves, dampers, etc. For OLCS, a few features shall include but are not limited to the following:

OLCS HIERARCHY: As discussed above, the OLCS system can be conceived to be arranged in a hierarchical structure, such as unit level, group level (such as boilers, turbines, feed water systems, etc.), subgroup level such as the evacuation subgroup, and drive level. A hierarchical structure may be helpful for sequential control implementation. However, some system drive controls are implemented in I/O cards. It is purely the design philosophy of the manufacturer.

UNIT LEVEL START UP AND SHUT DOWN: It is possible nowadays to start up/shut down a complete plant from a single keystroke. Such start up or shut down is done at the unit level. While designing a control system of this kind, the safety aspect is given the highest priority at every stage so that the sequence may proceed properly.

GROUP LEVEL CONTROL: Such controls are quite common in most of the systems such as BMS, ATRS, ATT, etc., as discussed in Sections 2.3 and 2.4 of this chapter. At this group level, independent automatic start up and shutdown is possible. When in the unit level, all groups are started one by one from a single start/stop command. For group starting or shut down, each group needs separate command. All subgroups, subloops, and drive interfaces (as applicable) under each of these groups shall be started one by one under this single group command. It is interesting to note that these group commands need not be fully automatic, but can be semiautomatic also.

CHECK BACK: CLCS is a feedback control system whereas the sequential controls of OLCS have CHECK BACK (ref clause no. 4.2.1.7) signals for the sequence to proceed. It is like feedback in CLCS. After a command signal is issued, before proceeding, the system ensures that the previous command has been obeyed by all concerned within the allowed time gap. This is to ensure that there is no hindrance in the sequence. This is done by check back signals. If there is any constraint for the execution of the previous command, then the fault/constraint must be detected and removed (may be bypassed for noncritical check backs, even manually and/or by manual override). For example, in order to start a large fan, it is necessary that its lubrication pump runs so as to establish a flow of oil in the bearing. Now, if the command is issued to start the pump, but the oil pump does not start or cannot send oil, then the bearings will starve. Therefore, check back signals (that the lube pump is running and the oil pressure is OK) are essential for the sequence to proceed further. Now. if there is no such check back for a large fan, then one can imagine what would happen.

OPERATION RELEASE AND LOGIC CRITERIA: Before issuing any command, the safety and readiness of the concerned equipment and systems need to be checked. When a command is issued (even manually), it is the duty of the system to check whether all the conditions for the safety and readiness of the concerned equipment and systems are available before it can make the command effective. These criteria checked by the system at the start of the sequence for any subgroup/subloop/drive are normally referred to as operation release. For example, after a boiler shutdown, any fuel can be started only after purging is complete in the recent past (allowed time gap). In fact, if the fuel is not started within a specified time after the purge, another fresh purge cycle may have to be repeated before starting the first burner. Similarly, at each stage or for each interlock, such checks are done with the help of check back and other status signals referred to as logic criteria, which need to be satisfied (or bypassed) to proceed to the next logical step. The interlock will have the highest priority and can be executed at any stage.

OPERATIONAL MODES: Normally, three modes of operation are seen in this type of OLCS: Automatic, semiautomatic (step by step), and manual (operators guidance). These are also discussed in clause no. 2.4.2.5 of this chapter (Fig. 7.75).

MONITORING and DISPLAY: In order to facilitate operation, it is customary to have the step number /step status, operational release, step criteria, and check back status displays made available to the operator. There are provisions for alarms for abnormal situations. All modes, loss of timing, etc., are made available to the operator. Also, it is important that access to these logic programs shall be restricted to the authorized persons. Certain steps/criteria bypasses are allowed, but this is by operator only when a faster action of operation is called for, but never at the cost of (human, equipment) overall safety and only authorized persons are allowed to make such actions. Also, a few other sensors monitoring like Non coincidence error, Open/Short circuit monitoring etc. are done.

COVERAGE: The OLCS discussed above is not only applicable to the main power plant sequence, interlock, and protection, but shall include all offsites as well. However, in these offsites, there may be a PLC integrated with the main DCS, but the criteria discussed in the OLCS could be utilized, depending on the applicability. The same thing is applicable for the electrical control system also.

The various electrical systems within a power station include those associated with the connection of the generating plant to the grid system and the very much larger number which are provided to distribute power supplies around the auxiliary plant within the station boundaries. The total electrical systems therefore interface with the whole of the power station installation. The systems can be summarised as follows:

The security required of the electrical supplies is determined by the importance of the power station plant or equipment. For example, auxiliaries associated with the main unit which if lost would immediately cause loss of unit output, clearly require more secure supplies than services such as sump pumps used occasionally. The nature of the supplies also requires careful consideration by way of voltage and frequency limits, susceptibility to transients caused by faults or switching operations and the consequences of short breaks in supplies. As a matter of course, most items of plant and equipment are specified and tested for compliance with known standards. This will include their electrical performance. If the need for new types of equipment is identified then performance limits should be defined at the outset of any development work, where standards cannot be quoted. The degree of security must also be taken into account since parts of nuclear power stations will warrant a much higher level than, say, a small hydro station.

It is necessary then, to recognise from the outset the importance of each item of plant when determining the nature and degree of security of electrical supplies it requires. The sources for auxiliaries supplies range from the grid-derived AC supplies, through to battery-backed AC and DC supplies and the short break supplies.

The bulk of the electrical auxiliaries load is normally arranged to be taken from the grid-derived AC supplies. This will mean that the outline design of the electrical auxiliaries system can benefit from previous knowledge and experience when considering alternative supply arrangements to a certain level at an early planning stage of a project. The alternatives will include, for example, unit and station transformer schemes, generator voltage switchgear schemes and HV switch isolator schemes. Detailed descriptions of these and other schemes are given later in this chapter.

The timely and accurate design of electrical systems is always easiest if at the outset, and at appropriate stages of the project, full details of electrical loading, rating and duty information can be established from the plant specialists, particularly for the major items, e.g., reactor, boiler, turbine-generator and operational ancillary plant. One way of achieving this is by including standard electrical loading, rating and duty schedules in all the plant enquiry specifications, thereby committing tenderers to identify their design loads. It also assists in forming a comparison between competitive tenders and should be followed up with more accurate and detailed information at defined stages of the contract by the chosen contractors. By this means, the electrical system loadings can progressively be assembled and refined, enabling design ratings of transformers, switchgear, cables, etc., to be established for comparison of the various possible alternative electrical systems.

The system designer would always present a recommended scheme by comparing the alternatives on a basis of first and lifetime costs and suitability for duty. Until this stage is reached, the electrical plant specialists cannot seriously begin to specify their requirements. It is possible, however, that the system designer has already taken account of the commercially available equipment, which will make the specifying of electrical components more straightforward.

This chapter explains the approach and criteria used in determining the most suitable electrical systems for the various duties required at nuclear, fossil-fired and hydro power stations. There is a brief reference to other forms of generation, generally referred to as alternative sources of energy.

The capital cost, CC, includes the cost of biomass energy conversion system, Cg, cost of fuel preparation and handling, Cfp, cost of turbine generator system, Ctg and cost of auxiliary plants, Ce, which include the electrical cost, oxygen separation plant.

The total plant cost (TPC) includes the cost of plant equipment (CC), direct and indirect costs of construction (Ccon), cost of project development (Cproj), most of which is office cost, and the contingency cost (Ccont).

The process contingency covers the uncertainty associated with the technology, while the project contingency covers uncertainty with project execution. If the plant does not perform as designed, modifications in gasifier or associated equipment are required. The process contingency is meant to cover that expense. Gasification, pyrolysis, or torrefaction technologies are not as matured as the combustion technology. So, the process contingency of such a plant would be a higher percentage of the capital cost than it would be for a conventional combustion plant.

A large gasification plant takes several years to complete. From the beginning of the project till the date when the plant actually starts earning revenue, there is no return on the investment, which is largely borrowed. During the entire period of project development, the plant owner would have to pay interest on the borrowed capital. This amount of carrying charge is known as allowance for funds during construction (AFDC) and is added to the TPC to get the total plant investment required (TPI).

The capital cost, CC, includes the cost of biomass energy conversion system, Cg, cost of fuel preparation and handling, Cfp, cost of turbine generator system, Ctg and cost of auxiliary plants, Ce, which include the electrical cost, oxygen separation plant.

The total plant cost (TPC) includes the cost of plant equipment, CC, direct and indirect costs of construction, Ccon, cost of project development, Cproj, most of which is office cost, and the contingency cost, Ccont.

The process contingency covers uncertainties associated with the technology, while the project contingency covers uncertainties with project execution. If the plant does not perform as designed, modifications in gasifier or associated equipment are required, and the cost associated with this modification comes from process contingency. Gasification, pyrolysis, or torrefaction technologies are not as matured as the combustion technology. Therefore, the process contingency of such a plant would be a higher than it would be for a conventional combustion plant. DOE/NETL(2011) gives some values of process contingency such as >40% for new concept with limited data, 30%-70% for concept with bench scale data 5%-20% for full size module operated and 0%-10% for commercial process. American Association of Cost Engineers (16R-90) gives project contingency as 15%-30% of (Bare erected cost + EPC fee + Project contingency).

A large gasification plant takes several years to complete. From the beginning of the project till the date when the plant actually starts earning revenue, there is no return on the investment, which is largely borrowed. During the entire period of project development, the plant owner would have to pay interest on the borrowed capital. This amount of carrying charge is known as allowance for funds during construction (AFDC) and is added to the TPC to get the total plant investment required (TPI).

challenges in limestone processing

challenges in limestone processing

Limestone is a versatile commodity used to create products for agricultural, environmental, and industrial purposes. Cement, paint, soil amendments, and even breakfast cereals all contain this resourceful mineral. Of course, mined limestone is not naturally found in a suitable form for many of these products. Therefore, various processing systems are needed to transform raw limestone rock material into a useful product. Common limestone processing methods that prepare the material for subsequent manufacturing stages include drying, calcining, pre-conditioning, and pelletization. The following information highlights limestone processing issues associated with these techniques, as well as general material challenges associated with limestone manufacturing.

A drying process is often used to precondition limestone rock for subsequent manufacturing steps. Like most rocks, limestone is abrasive as a raw material. As a result, heavy-duty rotary dryers are recommended to handle limestones abrasive characteristics. Equipment customizations such as heavy-duty linings may be necessary depending on the size of the rock being processed and other application specific criteria.

Drying processes may also be used on powdered limestone, with the recommended equipment again being rotary dryers. Many limestone manufacturers address moisture issues and prevent material clumping by utilizing a drying process before storing powdered limestone for extended periods of time.

Rotary kilns are most often used to produce lime products in the United States. Hot combustion gases and limestone move counter currently within the refractory-lined drum of the rotary kiln, applying a high-temperature process that ultimately changes the raw material into a high calcium lime or dolomitic lime. Particle matter pollutants are a common issue with rotary kilns, requiring the application of a particulate control in order to counteract this problem. FEECO also offers special burners to limit air pollutant emissions such as NO2 and CO.

Pelletization resolves a number of issues associated with limestone processing, from uniformity to nutrient delivery. Limestone pellets offer reduced dust, more accurate application, improved handling, and less product lost to dust. Fortunately, with such great benefits, limestone pelletization is a fairly straight-forward process.

However, there are still limestone processing problems that must be considered. For example, moisture is an important element in effectively pelletizing limestone. Throughout preconditioning, pelletization, and drying, moisture levels should be monitored and maintained to ensure optimal products are created through every stage of limestone processing.

Pre-Conditioning:A pin mixer imparts a powerful rotating motion upon limestone and its binder, creating an evenly distributed mixture with a moisture level best suited for pelletization. A successful pre-conditioning process creates an easily controllable mixture for forming limestone pellets on the subsequent disc pelletizer. Additionally, the material densification is greater than that of a disc pelletizer alone. However, pin mixers require special abrasion resistant pins due to the potential for accelerated wear when processing limestone. Consequently, proper maintenance is important to avoid equipment breaks and prevent costly downtimes.

Pelletization:A disc pelletizer gradually grows the pre-conditioned mixture into limestone pellets using a binder and the motion of the rotating disc. Monitoring the materials moisture level is critical at this stage, because pellet characteristics such as size and strength are secured by monitoring moisture ratios during this process.

Drying:A drying process is utilized to control moisture levels within the pelletized limestone. As an added benefit, drying adds pellet strength and prevents clumping related issues. Rotary dryers are recommended for their ability to uniformly dry pellets, handle a large throughput of material, and naturally polish the limestone as it tumbles through the drum. The resulting product is also easier to handle and store. Knocking systems are available to reduce material clumps by dislodging material build-up inside the drum.

Limestone processing problems are not unlike the challenges faced by many other naturally occurring materials. In addition to build-up and clumping problems, limestone composition can also vary from one region to another.

Limestone build-up has the ability to wear down equipment parts if left untreated. In order to prevent limestone maintenance issues, consistent material build-up removal (as part of an equipments regularly scheduled maintenance plan) is necessary.

Limestones composition, porosity, and texture can vary for a number of reasons, especially when the material is mined from different regions around the world. Consequently, FEECO recommends testing limestone before moving forward with processing strategies.

From drying to pelletizing, and even testing and material handling, FEECO is a complete processing solutions provider for the limestone industry. By combining over 60 years of experience with superior engineering capabilities and a unique material testing facility, FEECO is able to create the best limestone processing and equipment designs for our customers. For more information on our limestone processing experience, contact us today!

manufacturing process of lime from limestone production line - best stone crusher plant solution from henan dewo

manufacturing process of lime from limestone production line - best stone crusher plant solution from henan dewo

Dewo machinery can provides complete set of crushing and screening line, including Hydraulic Cone Crusher, Jaw Crusher, Impact Crusher, Vertical Shaft Impact Crusher (Sand Making Machine), fixed and movable rock crushing line, but also provides turnkey project for cement production line, ore beneficiation production line and drying production line. Dewo Machinery can provide high quality products, as well as customized optimized technical proposal and one station after- sales service.

Production. In the lime industry, limestone is a general term for rocks that contain 80% or more of calcium or magnesium carbonate, including marble, chalk, oolite, and marl. Further classification is done by composition as high calcium, argillaceous (clayey), silicious, conglomerate, magnesian, dolomite, and other limestones.

11.17 Lime Manufacturing. 11.17.1 Process Description 1-5 Lime is the high-temperature product of the calcination of limestone. Although limestone deposits are found in every state, only a small portion is pure enough for industrial lime manufacturing. To be classified as limestone, the rock must contain at least 50 percent calcium carbonate.

For example, a common use is in the production of precipitated calcium carbonate (pcc) by reaction with carbon dioxide. Slaked lime is formed by reacting quicklime or calcium oxide with water. The quicklime is usually produced by thermally decomposing calcium carbonate, eg. obtained from a mineral source, such as limestone, in a furnace.

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The compressive strength of limestone is typically about 150 MPa, it belongs to soft rock, and therefore impact crusher is adopted for the production process of limestone production line. The proven Hazemag impact crusher is used in Sanme limestone production line, it is a new type of impact crusher with high efficiency, and is suitable for ...

ca-looping for postcombustion co2 capture: a comparative analysis on the performances of dolomite and limestone - sciencedirect

ca-looping for postcombustion co2 capture: a comparative analysis on the performances of dolomite and limestone - sciencedirect

The CO2 capture performance of dolomite is studied at realistic calcium-looping conditions.Dolomite has a superior capture performance as compared to limestone.MgO grains in decomposed dolomite serve as a thermally stable support for CaO.Full decarbonation of dolomite is achieved at lower calcination temperatures as compared to limestone.

The low cost and wide availability of natural limestone (CaCO3) is at the basis of the industrial competitiveness of the Ca-looping (CaL) technology for postcombustion CO2 capture as already demonstrated by 1Mwt scale pilot projects. A major focus of studies oriented towards further improving the efficiency of the CaL technology is how to prevent the gradual loss of capture capacity of limestone derived CaO as the number of carbonation/calcination cycles is increased. Natural dolomite (MgCa(CO3)2) has been proposed as an alternative sorbent precursor to limestone. Yet, carbonation of MgO is not thermodynamically favorable at CaL conditions, which may hinder the capture performance of dolomite. In the work described in this paper we carried out a thermogravimetric analysis on the multicyclic capture performance of natural dolomite under realistic regeneration conditions necessarily implying high calcination temperature, high CO2 concentration and fast transitions between the carbonation and calcination stages. Our study demonstrates that the sorbent derived from dolomite has a greater capture capacity as compared to limestone. SEM analysis shows that MgO grains in the decomposed dolomite are resistant to sintering under severe calcination conditions and segregate from CaO acting as a thermally stable support which mitigates the multicyclic loss of CaO conversion. Moreover, full decomposition of dolomite is achieved at significantly lower calcination temperatures as compared to limestone, which would help improving further the industrial competitiveness of the technology.

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