Issues related to the utilization of low-temperature heat

The utilization of low-temperature heat has always been a key factor in energy conservation and consumption reduction within the chemical industry. I hope everyone can share their experiences so that we can progress together, offer suggestions for businesses, and improve energy efficiency as a group.

The main problems currently existing in the utilization of low-temperature heat by petrochemical enterprises are an unsystematic and unscientific network structure. The selection of heat sources and heat sinks is rather arbitrary, without adhering to the scientific principle of energy use based on matching temperatures and hierarchical utilization. In addition, the processes related to these low-temperature heat networks have not been optimized; as a result, there is often a large volume of circulating heat transfer fluid and low return water temperatures, which prevents the effective use of heat sinks with higher temperature levels. At present, heat integration among the upstream and downstream units in refineries both domestically and internationally is an important measure to reduce energy consumption. By using the heat generated by catalytic cracking units as a heat source for gas fractionation units, steam consumption is reduced, thereby achieving improved economic efficiency as well as energy savings. The effects and potential of low-temperature heat recovery and utilization are analyzed from aspects such as heat integration between upstream and downstream units, condensed water recovery processes, material diversion and recombination, and improvements in separation processes. It further explored the feasibility of setting steam grades in refineries and improving the energy efficiency of heat tracing systems. The Jinan branch carried out energy-saving renovations aimed at making use of low-temperature heat throughout the plant. By adjusting the heat exchange processes in the two catalytic cracking units, the low-temperature heat obtained was used as a heat source for the reboilers at the bottom of the deethanization tower and the depropyleneation tower in the gas separation unit, thereby replacing 1.0 MPa steam; the energy-saving effects were quite significant. Tests were also conducted using low-temperature heat as a heat source for the reboiler at the bottom of the light tetrahydrocarbon removal tower, with good results. (From Baidu O(∩_∩)O~~~)

Set up a lithium bromide refrigeration unit that can use both hot water and steam; this way, waste heat can be utilized while cooling capacity is also provided. Of course, the prerequisite is that the enterprise needs cooling; if cooling isn’t required for production, it can also be used for central air conditioning.

1. Use a heat exchanger to exchange heat with the low-temperature feed； 2. Add a waste heat recovery unit.