Auxiliary Processes and Operations

Instrument Control. The full usefulness of refinery equipment can be attained only by the use of automatic control instruments, and the use of instruments has contributed much to the productivity of refinery workmen (see Table 23-1). The handling of 10,000 bpd of capacity required 262 men during 1925 and 158 men in 1956. An attempt to discuss the merits of each individual instrument or type of instrument would be unsatisfactory because there are several different types of satiirfactory instruments for each purpose and because significant improvements are being made each year. 

In the control of a continuously operating system, certain variables must be fixed or the control of others is almc t impossible. Of prime importance are (1) the rate of feed, (2) the temperature of feed, and (3) the top temperatures of the towers. With these variables fixed, the control of the others is well within the capability of a competent operator. Even an expert operator is almost helpless if these three variables are not fixed. A plant can be operated with these controls alone, but the operation will be much more efficient if other controls are utilized. The rate of feed may be controlled by manual operation with the help of stroke 

recording pressure gauge i , indicating pressure gauge E, rate-of-flow controller F, pressure regulator ( , draft gauge H, hand-control valve safety valve ilf, liquid-level control. 

Optional instruments J, industrial thermometers or thermocouple wells K, flow meter L, stroke regulator and counter N, indicating thermocouples or connections for them 0, bypass adjustment valves or proportional draw-off devices. 

The principle of trend analyzing has been one of the notable improvements in instrument design. A trend-analyzing instrument will begin to stop the actuating mechanism before the condition (temperature, pressure, or rate of flow) has been brought back to the desired condition. In this way the tendency to overcontrol, or hunt, has been corrected. Such instruments apply a large correction if the condition is far from the control point and a small correction (or none at all) if the condition is nearly at the control point. 

---

In addition to the fixed capital investment needed to purchase and install process equipment and auxiliaries, there is a continuous expenditure referred to as operating cost, which is needed to operate the process. The operating cost (or manufacturing cost or production cost) includes raw materials, mass-separating agents, utilities (fuel, electricity, steam, water, refrigerants, air, etc.), catalysts, additives, labor, and maintenance. The total annualized cost of a process is defined as follows ... 

The work done in such a cycle is a maximum when all the operations are conducted reversibly, and, since all the auxiliary processes are reversible, it follows that the given process must also be conducted reversibly to obtain the maximum work. 

Auxiliary processes. Refineries also have other processes and units that are vital to operations by providing power, waste treatment, and other utility services, such as boilers, wastewater treatment, and cooling towers. Products from these facilities are usually recycled and used in other processes within the refinery and are also important with regard to minimizing water and air pollution. 

The economic outcome of the operation of a centrally located facility is comparable with all other hydrometallurgical operations and is highly dependent on price and quality of the metals produced. All products have to conform to commercial specifications. Adequate quality and quantity of cheap feed materials are also essential. It is very important to consider the fact that the transformation of waste and raw material usually involves a dramatic increase in the value of the feed material. The economic result cannot be isolated to an auxiliary process, but is the result of the combined effects on the total operation. 

Process and organisational solutions of design developments shall ensure maximum independence of MHR-T modules during operation and in all possible accidents with radiation emission/release. Links between MHR-T modules and between these modules and process lines and overall infrastructure (control, support and auxiliary systems) shall be determined at the design stage. 

Besides the main components, particular emphasis was placed on the essential subsystems/peripherals/balance-of-plant, including utility and auxiliary subsystems (instrument/operating air supplies, nitrogen supply, demineralised water/KOH systems, ventilation, etc.), process and safety control subsystems, and extensive test data acquisition subsystems. Also power conditioning (converters and inverters) as a way of improving the operability and efficiency of the overall system was considered. Some of the integration issues investigated in detail were ... 

Chlorine Plant Auxiliaries. Flow diagrams for the three electrolytic clilor—alkali processes are given in Figures 28 and 29. Although they differ somewhat in operation, auxiliary processes such as brine purification and chlorine recovery are common to each. 

To calculate the depreciable capital cost we need to calculate the cost of buildings and auxiliary facilities. Table 2.6 contains factors for calculating these costs. Ulrich [31] pointed out that these costs are not affected by process-equipment operating temperature and pressure, materials of constraction, or equipment design. Thus, we calculate the base installed cost, which is the installed cost of carbon-steel equipment at ordinary operating conditions and equipment design. To obtain the cost of auxiliary facilities and buildings, multiply Csbi by fAB- Now, we can now complete the calculation of the depreciable capital cost as outlined in Table 2.14. 

Along with selecting conditions which ensure obtaining products with the required degree of purity at a maximum yield, the choice of a process scheme in which expenditures for auxiliary operations are reduced and wastes are minimized determines, in many respects, the efficiency of the process and the expediency of its use. 

ANCILLARIES. The equipment and components mentioned thus far are directly connected with the supercritical fluid food processing plant, but other ancillary and auxiliary equipment must also be specified, procured and installed. Heating, cooling, and other utilities must be integrated with the SCF process components and operate efficiently and reliably. 

---