This invention segregates the heat integration in a hydrothermal liquefaction (HTL) process to reduce the design pressure and temperature requirements for piping, pumps, and heat exchanger equipment. Reducing the design conditions reduces the equipment cost and size and allows for multiple heat exchange technology options to be simultaneously utilized. The vapor pressure of water sets the system operating pressure. Water is very volatile, so the vapor pressure increases rapidly with operating temperature. Areas of the process that require high temperatures, such as the reactor, must be designed for a high operating pressure. However, areas of the process that do not operate at high temperatures can in principle be designed for lower operating pressure. The HTL process requires heating a slurry feed from ambient temperature to 600-700 degF. The large temperature change requires a significant investment in heat exchangers. Heat exchangers are responsible for >70% of the capital cost of HTL. The design pressure of the heat exchangers has a major influence on the cost. The thickness of the heat exchanger shell is proportional to the design pressure. Therefore, reducing the design pressure by half will reduce the mass of metal required to make the shell by approximately half. In addition to heat exchangers being cheaper, lowering the design pressure allows additional styles of heat exchangers to be used. For example, spiral heat exchangers have many advantages over shell and tube heat exchangers for slurry service. However, the relatively low design pressure limitations of spiral heat exchangers have prevented their utilization for HTL. This invention separates the feed/product heat exchanger train into multiple sections operating at different pressures. Sections earlier in the heat exchanger train (operating at lower temperature) can operate at lower pressure, allowing them to be manufactured cheaper. Staging pumps are used to increase the pressure between the different heat exchanger sections. This invention allows for different heat exchanger technologies to be used between the multiple sections. One configuration proposed is to use a spiral heat exchanger design in the earlier, low pressure stages and shell and tube in the later, high pressure stages. This configuration could be advantaged because spiral heat exchangers perform very well in the HTL application due to their fouling resistance and reasonably good heat transfer with viscous fluids, but can be expensive to manufacture at high design pressures.