Design slurry pump

CHAIRMAN SEGLIN I think their conceptual design was based on lock hoppers. He alluded to slurry pumping, but that s a horror. 

Supervision instituted new procedures. When slurry feed supply is shut down, procedures require the operators to continue agitation and acid flow for at least 30 minutes. On startup, the agitators and acid feed will be restored before starting up the slurry pumps. Both of these steps were designed to eliminate the possibility of having an undetected layer of calcium carbonate. 

Another example of a short residence time PFR is that of New York University [25]. It has a different design in the reactor segment in that a twin-screw extruder is used as a moving-bed mechanism eliminating the external slurry pump. Although the detailed design in acid injection and temperature... 

The head for the circulating pump and the slurry pumps can be calculated from information in the Chemical Engineers Handbook (Perry 1973). The mechanical design should be in accordance with the information in the american Society of Mechanical Engineers Code for Unfired Pressure Vessels, Section VIII, for the current year. There is a section devoted to the design of vessels under external pressure. 

Abrasion is usually a major consideration in pump selection. Except for the mild chemical-type duties already referred to, slurry pumps are of special construction, essentially to resist abrasion to the pump and its shaft seals but often also to permit fast maintenance and liner or component replacement for very abrasive duties. Generally either replaceable rubber lining or specially hard abrasion-resistant alloys are used shaft seals are of special design, and are usually continually flushed with clean water. Impeller tip velocities are kept within proven limits for the application. Power transmission is often through V-belts rather than direct-drive couplings, to permit exactly the required speed to be obtained (rather than synchronous speeds) and to permit speed optimization in service (varying the impeller diameter is not so convenient). 

It is wise to allow for pump head and efficiency deterioration, relative to its water performance, of a few per cent, based on the pump supplier s data and according to the slurry properties. Indeed, the suppliers of specialist slurry pumps will usually assist in the overall system design. It is also wise to allow a margin of 15-25 per cent of maximum calculated absorbed power when sizing the driver, to provide flexibility for operation at increased densities and pump speeds. 

Centrifugal Slurry Pumps These pumps are characterized by limited casing pressure and efficiency. Efficiency is low because of the robust nature of the impeller design and relatively wide impeller throat clearance. Multiple pumps in series can develop final-stage discharge pressures up to about 600 psig. 

The problem of pumping thixotropic froth in oil sand plants was a challenge to manufacturers of pumps, and for a while the belief was that only positive displacement pumps could he used. In 2000, the operators of oU-sand processing plants invited the manufacturers of slurry pumps to develop new appropriate pumps. Research is being conducted at the Saskatchewan Research Institute in Canada and is starting to yield new concepts of pump design. 

It is hoped that the various worked examples in this book will help the practical engineer to design slurry pipelines, it may be necessary to use more than one method and compare results. There are many advantages to pumping slurries at high concentrations, such as concentrates from process plants, food pastes, and ceramic slurry for the manufacture of new materials. 

The diameter of the rods is often 50 mm (2 in) but can be set by the designer of the mill. It is, however, important to separate the rods or balls from the slurry at the discharge of the mill before they enter the slurry pump. The successful separation of steel balls from the slurry involves proper design of trommels, a mechanism to catch the balls, and screens on top of the pump box. Ideally, the balls should be recycled back to the feed of the milling unit. 

The design of centrifugal pumps involves a combination of mathematical and empirical formulae and models. Although water pumps have been the subject of extensive research in the past, slurry pumps have been designed based on a compromise of what can be cast with hard alloys, molded in rubber, and what can meet the hydraulic criteria. 

A lot of papers have been published over the years on various aspects of wear in a slurry impeller or volute, performance corrections and derating, etc. The reader of these papers is often left with the impression that the design of these pumps is a combination of science and art. What is often lacking in the literature are guidelines for the design of slurry pumps. 

In this chapter, the concepts of expeller, pump nt vanes, and dynamic seal will also be examined. These are very important aspects of slurry pump design that have suffered from a dearth of information in the published hterature. 

Wear remains a concern for the design of a slurry pump. There is no direct correlation between the best hydraulics and the highest wear Ufe. In fact, the whole activity of designing a slurry pump is to find an optimum compromise. 

A centrifugal pump is essentiaily a rotating machine with an impeller to convert shaft power into fluid pressure. The dynamic energy is then converted into pressure or head in a special diffuser or casing. The manufacturers of slurry pumps have developed a number of specialized designs such as... 

Before dwelling on the design of a siurry pump, it is essential to have a basic understanding of the hydraulics invoived. But since the design of slurry pumps must also take in account the wear due to pumping abrasive solids, many other factors enter into the equation, such as the ability to pump large particles and the use of special alloys or polymers for liners or impellers. 

Practically all slurry pumps are single stage. Multistage pumps are limited to mine dewatering applications. Slurry pumps are rubber lined whenever they are designed to handle particles finer than 6 mm or Because rubber is susceptible to thermal degradation when the tip speed of the impeller exceeds 28 m/s or 5500 ft/mrn, ruhher-Uned pumps are typically reserved for a maximum head of 30 m (98.5 ft) per stage. 

In the case of slurry pumps, passageways are larger than in water pumps to accommodate solids and the Anderson area ratio is difficult but useful to use. Unfortunately, many leading references on slurry pump design written in North America, such as the work of Herbrich (1991) and Wilson et al. (1992), continue to ignore the area ratio methods and focus on the Stepanoff school, which believes that the impeller is the main producer of head and efficiency. 

The design of a centrifugal slurry pump is complex. Performance depends on the area ratio, impeller tip angle, recirculation patterns, change with wear of the impeller, back vanes, and front pump-out vanes. 

---