A partially answer (working in a particular case) might be the following one. Assume that you have a partially ordered ring A, which is also a vector lattice over the real field (example: A=C(X), the space of all real continuous functions on a topological space X. The positive cone P is the cone of all nonnegative functions at each point of X). Define a positive convex ideal as being a convex ideal for which all its elements are positive. Then the sum of two positive convex ideals is a positive convex ideal. In fact, if 0
Is the sum of two convex ideals convex too? Yes it iis convex but it is to be changed as the linear sum of two convex ideals is a convex ideal. . . . Dr N V Nagendram
The Riesz property is valid, in particular, in any vector lattice. Information on this subject was published in the classical monograph of H. H. Schaeffer: "Topological Vector Spaces", Springer-Verlag, Chapter 5. Another source is the monograph by Romulus Cristescu: 'Ordered Vector Spaces and Linear Operators", Academiei, Bucharest, and Abacus Press, Tunbridge Wells. For both these excellent books, there are several improved editions. More information is available on the Internet..