Batch conveying systems

The systems considered so far have all been capable of continuous conveying. In many processes, however, it may be more convenient to convey one batch at a time. Although a 

Two types of system are considered. In one, the batch size is relatively large, and the material is fed into the pipeline gradually, and so can be considered as a semi-continuous system. In the other, the material is fed into the pipeline as a single plug. 

The blow tanks used vary in size up to 50 m or more, generally depending upon the material flow rate required as well as a need to maintain a reasonable frequency of blow tank cycling. The material can be conveyed in dilute or dense phase, depending upon the capability of the material, the pressure available and the conveying distance, as with continuously operating systems. 

In comparison with a continuously operating system, therefore, the batch operating system would appear to be at a disadvantage. Blow tank systems, however, can operate at very much higher pressures to compensate, and twin arrangements in series can be configured 

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Each chapter starts with a description of the topic covered in the chapter. This is followed by a short example highlighting a reported incident involving a batch reaction system. The case study is followed by a listing of key issues and process safety practices unique to the topic. The issues and concerns presented in this book, as well as potential design solutions and sources of additional information are presented in the tables. This format concisely conveys the necessary and relevant information in a familiar and convenient format. The organization of the tables is described below. 

The benefits of a conveying system over a multi-flight hoisting system are in the elimination of buffering and batching facilities in the transfer from one flight to the next. 

All pneumatic conveying systems, whether they are of the positive or negative pressure type, conveying continuously or in a batch-wise mode, can be considered to consist of the basic elements depicted in Figure 4.12. 

While negative pressure conveying systems have been covered in some detail in Chapter 4, there is a small sub-set that will be considered here. Small volume batch conveyors, or simply vacuum conveyors , generally consist of a small tank and a relatively short conveying line in which a vacuum is generated, and this is connected to a material feed hopper. Once the required negative pressure has been reached using the attached vacuum pump, a valve is opened on the feed hopper and the material is conveyed into the vacuum tank. The system... 

The specific equipment used for each step depends on the incinerator type and the physical and chemical characteristics of the wastes the incinerator is designed to bum. Wastes are fed into the incinerator in batches or in a continuous stream. Liquid wastes are often pumped and atomized into fine droplets that bum more easily. Solid wastes may be fed into the incinerator in bulk or in containers using a conveyer, a gravity system, or a ram feeder.8... 

Therefore, the dispenser control panel should be equipped with a timer-relay device to insure that all admixture has been discharged from the conveying hoses or pipes. If the admixture dispenser system is operated manually, the plant operator should be furnished a valve with a detente discharge side to prolong the discharge cycle until it is ascertained that all admixture is in the concrete batch. 

If computer-integrated resin handling systems are considered, one must compare their operating procedures with one s process requirements. These process requirements describe the flow of resin and product through the system, which determines the system s electronic architecture. Pertinent considerations include batch vs. continuous operations, the type and number of conveying lines, resin storage and distribution, quality control means and procedures, inventory control, the type and quantity of process parameter sensors, the type and quantity of controlled devices, modes (automatic, semiautomatic, manual, and/or shutdown modes), process information, process management controls, and centralized vs. local operation (Fig. 9-1). 

A variation of the vacuum system just described utihzes a rotary airlock on the bottom of the hopper in place of the flapper assembly. The airlock seals the vacuum in the hopper while, at the same time, allows the material to be discharged into the silo. The primary advantage of this system is the fact that it conveys continuously rather than in intermittent batches. Its drawbacks are higher cost than the flapper discharge, airlocks tend to be a high-maintenance item located on top of the silos, and the tendency of some materials to break up or smear when passed through the rotor. 

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